TH E8! 8

I

2000

llllllIlllllllllllllllHllllllllllllllllllllllllllllllllllllll

3 1293 02074 118

Lissanv
Michigan State
University

 

 

 

 

This is to certify that the
thesis entitled

House mouse (Mus domesticus) habitat use and response

to repeated alfalfa harvests in the agricultural
landscape

presented by

Loren Donald Hayes

has been accepted towards fulfillment
of the requirements for

M. S. degree in May——

flag/limit?

Major professor

 

Date m 1.9, W
U ’ /

0-7639 MS U is an Affirmative Action/Equal Opportunity Institution

 

PLACE IN RETURN BOX to remove this checkout from your record.
TO AVOID FINE return on or before date due.
MAY BE RECALLED with earlier due date if requested.

 

DATE DUE

DATE DUE

DATE DUE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

moo (:lClRCIDmDuo.w5-p.t4

 

HOUSE MOUSE (MUS DOMESTICUS) HABITAT USE AND RESPONSE TO
REPEATED ALFALFA HARVESTS IN THE ARICULTURAL LANDSCAPE
By

Loren Donald Hayes

A THESIS

Submitted to
Michigan State University

in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE
Department of Zoology

l 999

ABSTRACT
HOUSE MOUSE (MUS DOMESTICUS) HABITAT USE AND RESPONSE TO
REPEATED ALFALFA HARVESTS IN THE ARICULTURAL LANDSCAPE
By

Loren Donald Hayes

The objective of this study was to describe house mouse habitat use on three southwest
Michigan farms in which barns were situated next to active alfalfa fields. At each site, 1
determined the proportion of house mouse telemetry locations and/or captures in barns.
At the Guthrie (GU) and Kellogg Biological Station (KBS) farms, the number and sex of
mice captured in the alfalfa fields were determined before and after multiple harvests. At
KBS, females were more frequently captured in the alfalfa field than males. Individuals
captured in the field either returned to the barn or were never recaptured following
harvests and mice rarely returned to the field within two weeks of harvests. Trap success
in the field decreased through the summer at KBS during 1997, but not during 1998. At
the GU farm, mice were rarely caught in the field and radio-collared mice (n = 10) were
never tracked into the field. Most radio-collared mice at the Anthony (11 = 6) and GU
farms were found in the habitat in which they were caught when collars were assigned. In
Michigan, where fields are often near barns, repeated alfalfa harvests during the summer
may limit house mouse movements into fields and between barns, affecting

metapopulation structure.

To Mom & Dad

You are an inspiration to me

iii

ACKNOWLEDGMENTS

I thank my advisor, R.W. Hill, for the advice and support that he provided throughout the
course of my M.S. program. I thank my committee members, G. Mittelbach, D. Straney
and S. Winterstein for their advice and criticisms. K. Holekamp, R. Van Horn, and O.
Schabenberger provided additional advice during the study. B. Bassett, M. Bonifas, J.
Carrara, K. Donahue, K. Greene, and T. Wood were very helpful in the field. Live traps
were provided by D. Beaver, R.W. Hill, R. Merritt, and the Michigan State University
Museum. K. Holekamp and S. Nunes loaned me telemetry equipment. H. Reynolds
assisted in the identification of plant species and in the collection of telemetry data. I
thank the Anthony and Guthrie families for permitting me to conduct research on their
farms. I also thank J. Bronson and the rest of the Kellogg Biological Station Dairy staff
for their assistance and cooperation. R. Douglass, L. Chambers, and G. Singleton
provided advice on the construction and attachment of radio-collars. I thank the men of
the Burgner house for putting up with peanut butter, traps, telemetry equipment and
straw. This project was funded by the following sources: American Society of
Mammalogists Grant-in-Aid-of-Research, Kellogg Biological Station Research Training
Group Summer Fellowship Program, Kellogg Biological Station Laufi' Foundation,
Michigan State University Department of Zoology, and Michigan State University

Ecology, Evolutionary Biology, and Behavior Program.

iv

TABLE OF CONTENTS

LIST OF TABLES .............................................................. vi.
LIST OF FIGURES ............................................................ vii.
LIST OF APPENDICES ....................................................... viii.
INTRODUCTION .............................................................. 1
METHODS ...................................................................... 5
RESULTS ........................................................................ 1 3
DISCUSSION .................................................................... 24
REFERENCES ................................................................... 38
TABLES ........................................................................... 42
FIGURES .......................................................................... 48
APPENDICES ..................................................................... 53

LIST OF TABLES

Table 1. Number of individuals and total number of captures in each habitat type that was
trapped at the Guthrie and Kellogg Biological Station (KBS) farmsl. Chi square values
are based on the expected number of individuals captured divided by the trap effort (total

number of traps set at each site) in each habitat type.

Table 2. Sex and weight of and prevalence of furless patches on individuals captured in
the Guthrie and Kellogg Biological Station alfalfa fields. The number of females in each

weight class and with furless patches is in parentheses.

Table 3. Number and proportion of house mice that were recaptured following harvests

and whose most recent captures before harvests were in the alfalfa field.

Table 4. Average distances and ranges of distances from the Kellogg Biological Station

barn that house mice were captured in the alfalfa field.

Table 5. Proportion of females and large individuals (16 g or more) that used the alfalfa
field during the periods between harvests at the Kellogg Biological Station. Proportions
are based on all captures, including those made in afternoon trapping sessions. Females

and individuals weighing 16 g or more are in parentheses. See methods for harvest dates.

vi

LIST OF FIGURES

Figure 1. Proportions of individuals showing various proportions of captures in barns at
the Kellogg Biological Station (A) and Guthrie (B) farms. Only individuals caught four

or more times during morning trapping sessions are included.

Figure 2. Number of individuals showing various proportions of telemetry locations in
barns at the Kellogg Biological Station (n = 2 individuals), Anthony (11 = 6) and Guthrie

(n = 10) farms.

Figure 3. Total number of afternoon and morning captures in the alfalfa field at the
Kellogg Biological Station on the corresponding days since alfalfa harvests in 1997 (A)
and 1998 (B, C). Only one individual was captured in the field during the period between

the 14 July and 1 September 1997 alfalfa harvests.

Figure 4. Trap success during morning trapping sessions in the alfalfa fields at the
Kellogg Biological Station (A, B) and Guthrie farms (C). Number of individuals captured
per period: (A) 15, 15, 1, 1; (B) O, 10, 4, O; (C) 6, 1, 1. Total number of captures per

period: (A) 21, 21, l, 1; (B) 0, 21, 6, 0; (C) 6, l, 1.

vii

LIST OF APPENDICES

Appendix A. Plant species found in the uncut fields at the Anthony and Guthrie farms.

Appendix B. Trap success (number of individuals captured/number of traps set) and
number of individuals captured in the Kellogg Biological Station barn between June and

August 1997.

Appendix C. Average (:t SE) proportions of barn captures of mice captured four or more

times.

Appendix D. Indoor and outdoor radio-telemetry locations and proportion of barn
locations of individuals tracked at the Anthony (n = 6), Kellogg Biological Station (KBS)

(n = 2) and Guthrie (n = 10) farms during 1998.

Appendix E. Number of individuals captured in alfalfa fields, total number of captures in
alfalfa fields and number of traps set in alfalfa fields during morning trapping periods
before and after alfalfa harvests. Afternoon captures are not included because traps were

not left open through the afiernoon on all dates.

viii

INTRODUCTION

The expansion of agriculture in North America during the last 200 years transformed
large areas of natural habitat into fragmented patches surrounded by farmland. The
potential effects of this spatial heterogeneity on small mammal demography and
movements have been a concern of landscape ecologists (Bowers and Matter 1997).
Some view remnant patches of natural habitat as ‘islands’ within an ‘ecologically hostile’
agricultural matrix (e.g. Henderson et al. 1985; van Apeldoom et al. 1992). Under these
conditions, small mammals are unable to move across cropfields, limiting populations to
within the remnant patches. Recent work suggests that some species are able to move
between patches (e. g. Nupp and Swihart 1998), maintaining metapopulations (Levins
1969) comprised of local populations within remnant patches (Merriam 1988). The
degree to which small mammals are able to move through spatially heterogeneous
habitats depends on many variables. Merriam and colleagues showed that chipmunks
(Tamias striatus) and white-footed mice (Peromyscus Ieucopus) use fencerows to move
between woodland patches (Henderson et al. 1981; Wegner and Merriam 1990). Lorenz
and Barrett (1990) demonstrated that house mice (Mus domesticus) move along chain-
link fences and vegetation strips in simulated landscapes. Movements may depend on the
types of cropfields surrounding patches (Cummings and Vessey 1994; Fitzgibbon 1997),
the distance between patches (van Apeldoom et a1. 1992) and a species’ ability to detect
and orient to source habitats once it has moved into fields (Zollner and Lima 1997).

Fewer researchers have studied how temporal heterogeneity (e.g. changes in

vegetative cover height during the summer) in the agricultural landscape affects small

mammal movements and distributions (e. g. Peles et al. 1997). The growing/harvesting
season of some crops (e.g. alfalfa) coincides with the breeding and dispersal periods of
many small mammals (e.g. Peromyscus). Harvesting or tilling of the land may destroy
underground burrows or expose small mammals to predators (Tew and MacDonald
1993). Harvests may reduce vegetative cover below heights critical to certain species
(Lemen and Clausen 1984), resulting in decreased survival, growth rates, movement and
population sizes (Tew and MacDonald 1993; Edge et al. 1995; but see Wolff et al. 1997).
Lemen and Clausen (1984) argued that mowing altered the composition of a small
mammal community in a native tall grass prairie in Nebraska. On lands that had mostly
recently been mowed, deer mice (P. maniculatus) became the dominant species afier vole
(Microtus) populations decreased (Lemen and Clausen 1984). Following harvests, some
species may be forced out of fields and into adjacent woods (Cummings and Vessey
1994), ‘set-aside’ fields (Tattersall et al. 1997) or buildings (Reimar and Petras 1968) that
may already harbor dense populations and provide insufficient resources.

Although alfalfa is harvested two or more times a summer in southwest Michigan
(pers. obs), no one has studied the impact that repeated harvests have on small mammals
using alfalfa fields. Multiple alfalfa harvests may effectively limit population growth of
vole species that are sensitive to the amount of vegetative cover (Taitt et al. 1981). The
removal of cover affects vole demographics (Peles and Barrett 1996), including possibly
the processes that drive population cycling. Other species respond differently to crop
harvests (e.g. Lemen and Clausen 1984; Henein et al. 1998) and these changes may

depend on the frequency and timing of harvests relative to breeding and dispersal events.

House mice are common in agricultural settings, using both fields and barns
(Stickel 1979). Numerous studies have been conducted on house mice living in buildings
(Bronson 1979) or agricultural fields (e. g. Krebs et al. 1995). However, few researchers
have studied house mouse movements between barns and fields (e. g. Reirnar and Petras
1968) despite evidence that some rodents can move greater distances than previously
thought (Wegner and Merriam 1987; Szacki et al. 1993). Although house mice occur in
alfalfa fields (Kaufman and Kaufman 1990), few researchers have studied the effects of
harvests on house mice (Linduska 1949) and no one has evaluated how harvesting
practices affect their habitat use between barns and nearby fields. Understanding house
mouse habitat use in barns and cropfields is an important step to modeling house mouse
metapopulation structure in the agricultural landscape. Do harvesting practices effectively
isolate house mice to individual barns or does sufficient gene flow for maintaining
metapopulations occur despite activity in adjacent fields? Does the frequent removal of
vegetative cover affect the population dynamics of mice occurring in barns and fields?

The objective of this study was to describe the habitat use of house mice
occurring in barns and temporally heterogeneous agricultural fields (e.g. alfalfa). I first
quantify the use of habitat by house mice on three alfalfa farms in southwest Michigan. I
then describe the movements of house mice using adjacent barns and alfalfa fields at two
sites before and after multiple harvests. This study generates a number of hypotheses
regarding the effects of crop harvest on the habitat use, movements and density of house
mice and other rodents that use buildings in the agricultural landscape (e. g. Peromyscus;

Middleton and Meniam 1981). By understanding how house mice use the agricultural

landscape, we may be better able to predict their response to crop harvests and plan more

efficient pest management programs.

METHODS

This study was conducted on three southwest Michigan farms with barns situated next to
alfalfa (Medicago sp.) fields. During 1997, I determined habitat use patterns at the
Kellogg Biological Station farm and in 1998, the Anthony and Guthrie family farms were
added to the study. Three levels of animal organization were considered in this study.
Within-site habitat use pattems were based on the trapping records of all house mice and
were used to represent general trends at the Guthrie and Kellogg Biological Station
farms. Individual habitat use patterns within each site were determined from the trapping
records of individuals captured four or more times and fi'om individuals tracked with
radio-telemetry. In this study, populations were defined as groups of interbreeding
individuals living in a given habitat type (i.e. barns and fields). Since house mice
throughout most of North America are strongly associated with buildings (Kurta 1995), it
was assumed that house mice originated from populations within barns. However,
individuals (with four or more captures/six or more radio-telemetry locations) found in
fields, but never in barns, were considered members of a field population. While it is
likely that multiple barn populations comprising a metapopulation existed at each site,

this level of organization could not be determined in this study.

Site descriptions

Kellogg Biological Station
The Kellogg Biological Station farm (Hickory Corners, MI) consisted of a barn (11.0 m x

24.4 m) bordered on three sides by an active alfalfa field. A 46-183 m strip of mowed

grass separated the field from the barn. The south side of the barn bordered a mowed
lawn and dirt driveway. The two upper lofis of the barn were used for straw storage and
the three rooms in the lower level of the barn were used for equipment storage. Feral cats
were not observed in or around the barn during 1997 and only once during 1998 (n = 1

cat).

Anthony Family Farm

The Anthony farm (Hickory Corners, MI), approximately 1.5 km southeast of the
Kellogg Biological Station farm, consisted of an unoccupied horse barn (10.4 m x 18.9
m) that was bordered by an active alfalfa field, undisturbed horse paddock, uncut mixed
species field (Appendix A), mowed lawn and dirt driveway. Parts of the alfalfa field were
mowed during the period between 4 and 15 June 1998 and the entire field was mowed on
11 August 1998. The upper lofts of the barn were used for straw storage. The lower level
consisted of six horse stables and a storage room holding open bags of horse feed. On
one occasion, I observed a feral cat moving through a distant field, but no cats were
observed in the ham or in the fields near the barn. Trap data fi'om this site were not
quantified because raccoons repeatedly disturbed outdoor traps, making it impossible to

compare trap success inside barns and in fields.

Guthrie Family Farm
The Guthrie farm is located in Delton, MI, approximately 6.5 km northwest of the
Kellogg Biological Station farm. The site consisted of a main straw storage barn (10.6 m

x 35 m), an alfalfa field 7-8 m from eastern edge of the barn, and a fenced, uncut grass

field located 21 m south of the barn (Appendix A). The barn and uncut field were
separated by a concrete courtyard and an open straw storage container (3 m x 27.4 m).
There were two large, empty silos between the southern end of the courtyard and the
northern end of the uncut field. To the west and north of the uncut field and courtyard,
there was an open-faced pole barn filled with large square straw bales, a small chicken
coop, and a building used for storage. The main straw storage barn was bordered to the
north by a mowed lawn and dirt driveway. The owners had several cats that lived in or
near the barn. One cat in particular was seen on most days and on occasion was observed
carrying voles and house mice in its mouth. Before releasing animals, I paid carefiil

attention to make sure that the cats were not observing my actions.

Procedures

Trapping

During both summers, trapping methods were designed to monitor house mouse habitat
use relative to multiple alfalfa harvests. Sherman and Leather live traps fitted with cotton
and oats were opened in barns and fields starting in the late afternoon (4:30-6:00 PM
EDT) and checked the following morning (6:00-8:00 AM EDT). On dates when traps
were left open through the day, I rechecked the traps 1-3 times depending on the weather
conditions. During both years, traps located in fields were removed shortly before or on
the morning of an alfalfa harvest. Traps were placed back into the fields soon after the
fallen alfalfa was removed from the field, and then the traps were reopened periodically
until the following harvest. Field grids started 3.0-7.3 m from barn edges and varied in

shape and size depending on the location and orientation of the barn relative to the field.

During the 1997 summer, trap grids were set within the Kellogg Biological
Station barn (2 m spacing, n = 51-108 traps) and in areas of the alfalfa field bordering the
northern and eastern edges of the barn (7.6 m spacing, n = 161 traps). Additional traps
were set in a house (11 = 10-15) and hedgerow (n = 11), both of which were about 150 m
west of the barn. Alfalfa was harvested on 11 June and 14 July 1997. Between 6 June and
22 August 1997, multiple cycles of trapping were carried out. During each cycle, I
checked traps in the barn, house, and hedgerow for 2-4 days. I then checked the alfalfa
field grid for 2-4 days before closing all traps for 1-5 days prior to the start of the next
cycle. Adjustments in the trapping cycle were made to ensure that traps were in the field
during the days immediately preceding a harvest. Between 24 August and 19 October
1997, traps were Opened periodically in the alfalfa field and barn to monitor habitat use
relative to a 1 September 1997 alfalfa harvest.

During 1998, trapping methods were changed to include simultaneous trapping of
barns and fields at the Kellogg Biological Station and Guthrie farms. At both sites, barn‘
traps were set along walls, on top and along straw bales, and in areas of low human
activity. Grids with 9 m spacing were set in the areas of alfalfa fields that bordered barns.
At the Kellogg Biological Station farm, traps were set in the barn (n = 32-83) on 34
nights and in the alfalfa field (11 = 85-101) on 50 nights before and after alfalfa harvests
on 19 May, 6 July and 10 and 11 August 1998. During June 1998, trapping effort in the
barn was reduced because the population had not regenerated from a near extinction
during 1997 (see Appendix B). During two trapping periods in May and one in June
1998, raccoons knocked over many of the barn traps. The results fiom these days were

not included in any analyses requiring knowledge of the number of traps set. Between 1

June and 20 July 1998, 12 traps were periodically set in the mowed grass to the south of
the barn. No house mice were caught in this area.

At the Guthrie farm, 55-86 traps in the main straw storage barn (28 nights), 50-
100 in the alfalfa field (47 nights) and 10-36 in the enclosed, uncut field, were set relative
to alfalfa harvests on 20 June and 24 July 1998. On 18 nights between 23 May and 15
July 1998, traps (n = 17-25) were opened in the courtyard, pole barn and chicken coop.
Trapping in these areas was discontinued because over the 18 nights, only one house
mouse was caught.

House mice were marked with an unique toe-clip/ear notch combination, weighed
to the nearest gram with a Pesola spring balance, sexed and inspected for furless patches
on the rump. Individuals weighing 16 g or more were considered adults, whereas those
weighing less than 16 g were considered non-adults (DeLong 1967). Other small
mammals captured during the study included deer mice (Peromyscus maniculatus),
white-footed mice (P. Ieucopus), short-tailed shrews (Blarina brevicauda), and voles

(Microtus).

Radio-telemetry

During 1998, six individuals (three male) at the Anthony farm, ten (five male) at the
Guthrie farm and two (one male) at the Kellogg Biological Station farm, all weighing 15
g or more, were tracked with radio-telemetry. Radio-collars (2 g or less, < 15% of body
weight) consisted of a SM-l transmitter package (AVM Technologies, Livermore, CA)
fixed to a length of heat shrink tubing within an acrylic coating. Radio-collars were held

in place by tightening cable tie (pulled through the heat shrink tubing) around an animal’s

neck. Each individual was anesthetized with methoxyflurane before being assigned a
radio-collar. Before an individual was released, it was allowed to recover from the
anesthesia for 30 min to 1 h in a holding chamber lined with cotton.

Once released, individuals were followed for 1-16 days using a TRX lOOOS PLL
synthesized tracking receiver and Yagi antenna (Wildlife Materials Inc., Carbondale, 111.).
I included data from the day of release in analyses because the transmitters often stopped
working prematurely. Nighttime (sunset-4:00 AM EDT) and daytime (10:00 AM EDT-
sunset) tracking sessions were conducted at each site. I was interested in daytime
locations because house mice are nocturnal (Kurta 1995) and are probably close to their
nests during the daylight hours. During each tracking session, animal locations were
determined at 30 min to 1 h intervals. Locations within 1 m were determined by
triangulating to signals without using the attenuator on the receiver. Once the general
location was resolved, the attenuator on the receiver was turned on so that a more
accurate identification of location could be made. Since I was interested in general habitat
use patterns (rather than home ranges), exact locations were not always necessary. When
signals disappeared, habitats were searched until it was obvious that the transmitter was

not working properly or that the animal had moved far from the study site.

Statistical analyses

Trap success (number of individuals captured/number of traps set) is commonly used to
indicate habitat preference (e.g. Takada 1985). I consider trap success to be an indicator
of within-site habitat use but avoid using the term ‘preference’ because I did not conduct

any habitat choice experiments. A chi-square goodness of fit test was used to compare

10

trap success in barns and fields against an expected 1:1:1 distribution at the Guthrie farm
(alfalfa field, uncut field and barn) and an expected 1:1 distribution at the Kellogg
Biological Station farm (alfalfa field and barn).

Sex ratios and weight categories in fields were tested against an expected 1 :1
distribution using a chi-square goodness of fit test. A Mann Whitney U test was used to
determine if the average number of captures in each habitat was different for females and
males. I chose the Mann Whitney U test because male and female capture probabilities
(i.e. trappability) are not likely to be normally distributed (see Hilbom et al. 1976).
However, when sample sizes were large (n1 >20, n2 >40; 11 = the number of males or
females), a normal approximation was used to estimate the critical value, Zoos (Zar

1984)

Individual habitat use

Individual habitat use patterns were evaluated by determining the proportion of ham
captures for all individuals captured four or more times. The proportion of telemetry
locations inside barns was determined for individuals at the Guthrie (n = 10), Anthony (11
= 6), and Kellogg BiologiCal Station (11 = 2) farms. Mann Whitney U tests were used to
determine if males and females in this sample had different proportions of barn captures.
An equality of proportions test (Zar 1984) was used to determine if proportion of males
using fields at least once was statistically different than the proportion of females using

fields at least once.

11

Response to cutting

The following predictions regarding the effects of alfalfa harvests were made: 1. During
the period of alfalfa regeneration between harvests, the number of mice using fields
increases and 2. As a result of repeated harvests, trap success in fields decreases through
the summer. I used the number of individuals captured in the field as the alfalfa
regenerated (i.e. days since previous alfalfa harvest) to demonstrate the immediate effect
of harvesting on house mouse habitat use in fields. These data are not independent and
thus, cannot be analyzed with known trend analyses (e.g. correlation, Zar 1984;
nonparametric Cox Stuart trend, Bradley 1968). The number of mice using the field
between harvests may be affected by the trappabilities of individual mice (e. g. probability
that an individual is captured; Hilbom et al. 1976) or if animals respond differently to
being held in a trap (i.e. trap response). Trap success during periods between harvests
was determined. The trend in inter-harvest trap success through the summer was used to
evaluate prediction 2. These data are not independent and thus, statistical comparisons

were not made.

12

RESULTS

At each site, habitat use patterns were based on all morning captures. Afternoon captures
were not included in the analyses because traps were not always left open through the
afternoon. Demographic (e. g. sex ratio; weight classes) representation within habitats
were based on morning and afternoon trapping sessions. Individual habitat use patterns
were determined for all animals caught four or more times during the morning trapping

sessions. All trapping data were used to assess house mouse responses to alfalfa harvests.

Within-site habitat use

General habitat use

At the Kellogg Biological Station farm, 95 individuals were captured 336 times in the
barn and 31 individuals were captured 45 times in the alfalfa field between 6 June and 19
October 1997. Between 19 May and 25 August 1998, 38 individuals were captured 130
times in the Kellogg Biological Station barn and 13 individuals were captured 27 times in
the field. Between 23 May and 24 August 1998, 165 individuals were captured 498 times
in the Guthrie family barn, 8 individuals were captured once each in the alfalfa field, and
37 individuals were captured 76 times in the uncut field. Based on trap success for the
entire summer (number of individuals captured/total number of traps set), house mice
were found more commonly in bams than in fields at each site (Table 1). Based on these

data and those shown below, populations (i.e. inter-breeding individuals) were not

13

forming in the alfalfa fields. A feral population may have existed in the uncut field at the

Guthrie farm.

Sex ratio

During the summer, female house mice may move into agricultural fields to establish
nests or to find resources that are heavily guarded (e.g. food) or limiting (e. g. water)
within barns. Consequently, I expected that more females than males would be captured
in the alfalfa fields. Based on all trapping dates, more females than males were captured
in the alfalfa field during 1997 (20 female: 13 male: 1 unknown sex) and 1998 (10
female: 4 male) at the Kellogg Biological Station farm (Table 2). During both years,
however, the sex ratio in the alfalfa field was not significantly different from an expected
1 :1 distribution (1997: x‘ = 1.48, P > 0.05; 1998: 12 = 2.57, P > 0.05). Females were
captured more frequently (average = 1.65 i 0.21 (SE) captures/mouse) than males
(average = 1.31 i 0.17 (SE) captures/mouse) in the alfalfa field during 1997 (Mann
Whitney U: U’ = 187.5, U 005“), 13, 20 = 176). During 1998, females also were captured

more frequently in the field (average = 2.67 i 0.75 (SE) captures/mouse) than males

(average = 1.5 i 0.5 (SE) captures/mouse), but the comparison was not significant (Mann.
Whitney U: U' = 23, U0.05(1),4,9'= 30).

More females than males were captured in the Kellogg Biological Station barn
during 1997 (n = 49 females, n = 43 males, 4 unknown sex) and 1998 (n = 21 females: 17
males: 1 unknown sex). During both years; however, the sex ratio in the barn did not

deviate from an expected 1:1 distribution (1997: x2 = 0.39, P > 0.05; 1998: x2 = 0.42, P >

 

1 One female that died during capture was not included in the analysis.

14

0.05). Females were more frequently captured in the barn (average = 3.88 :1: 0.50 (SE)
captures/mouse) than males (average = 3.33 i 0.43 (SE) captures/mouse) during 1997.
The same trend was observed during 1998 (female average = 3.86 i 0.54 (SE)
captures/mouse; male average = 3.00 i: 0.62 (SE) captures/mouse).

Between 23 May and 24 August 1998, five females and four males were captured
once each in the alfalfa field at the Guthrie farm ()8 = 0.11; P > 0.05). One hundred and
five females and 60 males were captured in the barn and this deviated from an expected
1:1 distribution (x2 = 12.27, P > 0.05). Males averaged more captures in the barn
(average = 3.52 i 0.44 (SE) captures/mouse) than females (average = 2.72 i 0.23 (SE)
captures/mouse). The sex ratio of individuals captured in the uncut field did not deviate
from an expected 1:1 distribution (n = 20 males: 11 = 17 females; x2 = 0.24, P > 0.05).
Males were more frequently captured in the uncut field (average = 2.25 :l: 0.57 (SE)

captures/mouse) than females (average = 1.88 i: 0.30 (SE) captures/mouse).

Animal weights

Table 2 shows the distribution of weight classes of house mice captured in alfalfa fields
during afternoon and morning trapping sessions. Individuals weighing 16 g or more were
captured slightly more frequently in the alfalfa fields than individuals weighing less than

16 g (Table 2).

F urless patches
Furless patches on the rump may be an indicator of aggression and thus, individuals in

the alfalfa fields were examined for patches on the rump. A large number of individuals

15

in fields with furless patches on the rump would suggest that fields may be used by
subordinate mice chased out of barns. However, Table 2 shows that individuals captured
in alfalfa fields rarely had furless patches on the rump. During 1998, only 1 adult
individual had patches at the Kellogg Biological Station and none had patches at the
Guthrie farm (Table 2). During 1997, 6 individuals, all adults, had patches on the rump.

Fifty percent (11 = 3) of the individuals with furless patches on the rump were males.

Individual habitat use

Trapping

During 1998, the proportion of barn captures (captures in the barn/total captures) for each
individual captured four or more times during morning trapping sessions was calculated
for all trapping dates and for the dates when the barn and field were trapped
simultaneously. Since traps were not set in the two habitats on the same days at the
Kellogg Biological Station during 1997, the proportion of captures in the barn for
individuals captured four or more times was calculated for all trapping dates. The

proportions of barn captures for males and females are shown in Appendix C.

Kellogg Biological Station

During 1997, the average proportion of barn captures for individuals caught four or more
times (n = 36 individuals; average = 7.42 i 0.54 captures/mouse) was 0.88 i 0.03 (SE).
Each individual that was captured four or more times was caught at least once in the barn

and 50% were never captured in the field (Figure 1a). Males (n = 15 individuals; average

16

= 0.90 i 0.05 (SE) barn captures/total captures) and females (n = 21; average = 0.87 i
0.03 (SE) barn captures/total captures) in this sample had similar proportions of barn
captures (Mann Whitney U: U = 127, U005“), 15, 21 = 210). A greater proportion of
females (0.57) than males (0.40) used the alfalfa field at least once, but the comparison
was not statistically different (Equality of proportions test: p = 0.5, q = 0.5, Z = 1.01; P >
0.05).

During 1998, the average proportion of barn captures for individuals caught four
or more times was 0.93 i 0.07 (SE) when the barn and field were trapped simultaneously
(n = 7 individuals; average = 6.00 :l: 0.58 (SE) captures/mouse) and 0.84 i 0.05 (SE) for
all trapping dates (11 = 21 individuals; 6.29 i 0.44 (SE) captures/mouse). Based on all
trapping dates, all individuals were captured at least once in the barn and 57% were never
caught in the field (Figure 1a). Males (n = 7 individuals; average = 0.88 :I: 0.07 (SE) barn
captures/total captures) and females (11 = 14; average = 0.82 :l: 0.07 (SE) barn
captures/total captures) fiom all trapping dates had similar proportions of barn captures
(Mann Whitney U: U' = 46.5, U005“), 7, .4 = 72). Based on all trapping dates, an equal
proportion of males (0.43) and females (0.43) used the alfalfa field at least once. When
traps were presented simultaneously in the barn and field, each male (11 = 3) with four or
more captures was caught only in the barn and one of the four females caught four or

more times used the alfalfa field (proportion = 0.5 captures in barn/total captures).

Guthrie Family Farm
The average proportion of barn captures for individuals captured four or more times was

0.95 i 0.03 (SE) when the barn, alfalfa field and uncut field were trapped simultaneously

l7

(n = 38 individuals; average = 6.08 i 0.38 (SE) captures/mouse) and 0.92 i 0.04 (SE) for
all trapping dates (n = 51 individuals; average = 6.55 :l: 0.44 (SE) captures/mouse). Based
on all trapping dates, 88% of the individuals were caught in the barn only and 6% were
never caught in the barn (Figure 1b). Male (11 = 17) and female (n = 21) habitat use did
not differ when the barn, alfalfa and uncut field were trapped simultaneously (U ' = 192;
U035“), 17, 21 = 236) and for all trapping dates (n = 21 males, n = 30 females; Mann

Whitney U with normal approximation: Z = 0.74; P > 0.05).

Telemetry

Radio-telemetry allowed for more precise determination of animal locations than trapping
methods. The proportion of locations within barns was calculated for all animals tracked
with radio-telemetry (n = 18) during 1998. ‘Barn’ locations were assigned when
individuals were inside human-made structures, including the two silos at the Guthrie
farm. Locations along the outer edges of barns were considered ‘outside’ the barn and
thus, did not add to the proportion of locations inside barns. Appendix D shows the
locations and proportion of barn locations for each individual followed with radio-
telemetry.

At the Guthrie farm, individuals (n = 10) showed a propensity to associate with
areas outside of bams (Figure 2; average = 0.43 i: 0.13 (SE) barn locations/total
locations; 22.20 :I: 3.98 (SE) locations/mouse). However, habitat use depended on the
location in which the individuals were trapped when radio-collars were attached.
Individuals that were trapped outside of the barn when collars were attached (n = 5; 3

male) showed a propensity to associate with areas outside the barn (average = 0.17 i 0.07

18

(SE) barn locations/total locations). Individuals caught inside the barn (n = 5; 2 male)
showed a propensity to associate with the barn more than areas outside the barn (average
= 0.70 i 0.20 (SE) barn locations/total locations). A comparison of these averages was
not statistically different (Mann Whitney U: U' = 21, U005“), 5, 5 = 21), probably due to
small sample sizes. Males and females had dissimilar proportions (male: 0.36 i 0.19 (SE)
barn locations/total locations; female: 0.51 i 0.20 (SE) barn locations/total locations);
however, a comparison was not made because unequal numbers were captured in each
habitat.

All individuals tracked with radio-telemetry at the Anthony farm (11 = 6) were
captured in the barn at the time that collars were attached and showed a propensity to
associate with the barn (Figure 2; average = 0.96 i 0.02 (SE) barn locations/total
locations; average = 53.67 i 6.44 (SE) locations/mouse). Males (n = 3; average = 0.97 i
0.03 (SE) barn locations/total locations) had similar proportions of ham locations to
females (n = 3; average = 0.96 i: 0.02 (SE) barn locations/total locations). The individuals
followed at the Anthony farm had similar habitat use patterns as those at the Guthrie farm
that were captured in the barn at the time that radio-collars were attached (n = 5) (Mann
Whitney U: U = 18, U0.05(2), 5, 6 = 27). However, individuals followed at the Anthony farm
had significantly greater proportions of barn captures than those at the Guthrie farm that
were captured outside the barn at the time that radio-collars were attached (n = 5) (Mann
Whitney U: U' = 30, U005“), 5, 6 = 25).

At the Kellogg Biological Station farm, one of the two individuals tracked with

radio-telemetry used the alfalfa field. Both individuals showed a propensity to associate

l9

with the barn (Figure 2; average = 0.93 i 0.07 (SE) barn locations/total locations; 51.50 i

3.50 (SE) locations/mouse).

Response to cutting

Kellogg Biological Station
House mice were rarely caught in the field when vegetative cover was low (Figure 3).
Only one animal was captured in the field during the first trapping period (24 to 26 June
1997) conducted after the 11 June 1997 harvest (Figure 3a). Mice were not captured in
the field until the thirty-second day after the 14 July 1997 harvest and forty-second day
after the 1 September 1997 harvest. During 1998, mice were not captured in the field
until the thirty-fifth and twenty-fourth days after the field had been cut on 19 May and 6
July, respectively (Figure 3b, c). Sixty-four percent (n = 22 individuals) of the mice
captured most recently in the alfalfa fields before a harvest (i.e. location of last capture
before a harvest) were recaptured in the barn or field following a harvest during 1997
(T able 3). During 1998, 44 % (n = 4) of the individuals captured most recently in the
alfalfa field before a harvest were recaptured in the ham or field after a harvest (Table 3).
Between 24 June and 14 July 1997, the number of house mice using the alfalfa
field increased with respect to the days since the 11 June 1997 alfalfa harvest (Figure 3a).
Only one individual was captured in the alfalfa field between 15 July and 1 September
1997. There was an upward trend in the number of house mice captured in the alfalfa
field following the 19 May 1998 harvest (Figure 3b). Following the 6 July 1998 harvest,

all captures in the alfalfa field occurred between 30 July and 5 August 1998 (Figure 3c). 1

20

did not trap the alfalfa field between 6 and 10 August 1998 so that I could track animals
with radio-telemetry.

Cutting may have had lasting effects on house mouse habitat use at the Kellogg
Biological Station farm. Figure 4 shows the morning trap success based on the total
number of captures and total number of individuals captured in the alfalfa field before
and after harvests during 1997 and 1998 (see also Appendix E). During 1997, only one of
33 (0.03) individuals using the alfalfa field was recaptured in the field following a
harvest. One male was not included in this proportion because it was captured alter the
final harvest date. A similar proportion (0.08; n = 1 individual) was recaptured in the
alfalfa field after a harvest during 1998.

Repeated harvests of alfalfa may impact the distance that house mice travel into
the fields. If repeated harvests of alfalfa affect the quality of the field habitat, then house
mice using fields after initial harvests may be captured closer to barns compared to those
mice captured in fields before the initial harvests. However, it is also likely that voles
(Microtus) have a confounding impact on house mouse movements into the fields. Table
4 shows the average distance from the barn that house mice were captured in the alfalfa
field at the Kellogg Biological Station farm. Surprisingly, house mice were captured
farther into the field later in the summer than before the first harvest of the season.

During 1997, the proportion of all individuals that were captured more than once
in the alfalfa field before the 11 June 1997 harvest (0.33; n = 6 individuals) was similar to
the proportion caught more than once in the alfalfa field before the 14 July 1997 harvest
(0.27; n = 4 individuals). The two individuals captured in the field after 14 July 1997

were never recaptured in the field. Forty-five percent (n = 4 individuals) of the

21

individuals using the alfalfa field before the 6 July 1998 were captured more than once in
the field. One of the three individuals using the alfalfa field after the 6 July 1998 harvest
was captured more than once in the field before the 10 and 11 August 1998 harvest.

The sex ratio of individuals using the alfalfa field did not change through the
summer (Table 5). More females than males were captured in the alfalfa field at the
Kellogg Biological Station farm during each period between harvests during 1997 and
1998 (Table 5). One male was captured in the field after the final harvest during 1997.

During 1997, 89% of the captures weighing 16 g or more (11 = 16) were captured
in the alfalfa field before the first harvest at the Kellogg Biological Station (Table 5).
After the 11 June 1997 harvest date, only 2 of the 16 captures in the alfalfa weighed 16 g
or more (Table 5). Of these individuals, two were not weighed while in the alfalfa field.
However, both individuals weighed between 9-10 g within 4 days of capture in the field
and thus were put in the <16 g category (Table 2; footnote 2). One individual that was not
weighed when captured in the alfalfa field (15 August 1997) was not included in Tables 2
and 4 because it was not weighed in the barn within a reasonable period of time.

During the period between 20 May and 6 July 1998, 7 individuals weighing 16 g
or more, 1 individual falling into both weight classes and 1 individual weighing less than
16 g were captured in the alfalfa field at the Kellogg Biological Station farm (Table 5).
Among these individuals, two were not weighed when they were captured in the alfalfa
field but were included in Tables 2 and 4 (see footnote 3 in Table 2). One individual was
put in the 16 g or more category because it weighed greater than 16 g on 28 May 1998.

The other individual was put in the <16 g category because it weighed 15 g 3 days before

22

being captured in the field. After the second harvest, 3 of the 4 individuals captured in the

alfalfa weighed <16 g (Table 5).

Guthrie Family Farm
Only nine individuals were captured in the alfalfa field at the Guthrie farm between 23
May and 24 August 1998. Seven individuals were caught in the alfalfa field between 23
May 1998 and 20 June 1997. One individual was captured on the twenty-seventh day
following the 20 June 1998 harvest. One individual was captured in the alfalfa field on 24
August 1998 while I was attempting to radio-collar individuals.

Figure 4c shows the morning trap success based on the total number of captures
and number of individuals caught during 1998. Seventy-one percent (n = 5 individuals)
of the individuals captured most recently in the alfalfa field before a harvest were

recaptured in the barn or uncut field after a harvest (Table 3).

23

DISCUSSION

General habitat use patterns
The trapping methods used in this study were similar to those used by Reimar and Petras
(1968) on a Windsor, Ontario, farm and thus, a comparison between the habitat use
patterns observed in the two studies may be useful. Based on trapping data, house mice at
the Guthrie farm exhibited similar habitat use patterns as those mice described by Reimar
and Petras (1968). On both farms, sex ratios were female-biased in the buildings, a
finding that is supported by Rowe and colleagues’ (1983) study of house mice living in
four farm buildings in England. The sex ratios of mice occurring in fields were male-
biased at both sites. Male-biased sex ratios are common in agricultural fields (N ewsome
1969; Singleton 1989; Khan and Beg 1990; but see DeLong 1967), suggesting that the
structure of the population in the uncut field at the Guthrie farm may be similar to those
living in infrequently disturbed fields in other farmsteads. In both studies, only a small
percentage of animals captured in fields were also captured inside barns (Guthrie: 13.0%;
Windsor: 6.4%, see Table 3 in Reimar & Petras 1968), suggesting that separate barn and
field populations existed. That radio-collared individuals initially captured in the uncut
field at the Guthrie farm showed a propensity to associate with the field (Fig. 2) supports
this argument.

The sex ratios in the barn at the Kellogg Biological Station during 1997 and 1998
were similar to those at the Guthrie and Windsor farms (Reimar and Petras 1968).
However, house mice at the Kellogg Biological Station used the alfalfa field differently

than the mice at the Guthrie and Windsor farms used fields. A greater proportion of

24

individuals (with at least four captures) used the alfalfa field at the Kellogg Biological
Station farm than at the Guthrie and Windsor (Reimar and Petras 1968) farms; however,
all individuals that used the Kellogg Biological Station alfalfa field were also captured
inside the barn (Figure 1). Simultaneous trapping of the field and barn indicated that
some mice used both the barn and field during the days preceding harvests. These results
suggest that separate populations (i.e. groups of interbreeding individuals) in the barn and
field did not exist.

During 1997 and 1998, the sex ratios of individuals using the Kellogg Biological
Station alfalfa field were female-biased (but not to a statistically significant extent) for
the entire summer and within each period between harvests (Table 5). Were females
forming nests in the alfalfa field or simply wandering into the field in search of food or
water? Does the sex ratio in fields adjacent to barns indicate the conditions of the
population(s) within the barn? The female-biased sex ratio that occurred in the alfalfa
field at the Kellogg Biological Station farm contradicted the results from a number of
studies that suggest that even or male-biased sex ratios are common in fields (e. g.
Singleton 1989). Newsome (1969) observed female-biased sex ratios in declining
populations of mice occurring in fields. It is unlikely that the female-biased sex ratio in
the alfalfa field at the Kellogg Biological Station farm was a result of a declining
population at the site. During 1997, females dominated the alfalfa field during all pre-
harvest periods and before the number of individuals captured in the barn began to
decline (Appendix B). Myers (1974) argued that house mice, particularly females that are
about to become reproductively mature, respond rapidly to available habitat. Lactating

and pregnant females and juveniles were captured in the alfalfa field, suggesting that

25

some individuals may have established nests in the field. Alternatively, females may have
foraged in the alfalfa as resources (e.g. food and water) became limiting in the barn.
Additional studies examining how house mouse females use alfalfa are needed to better
understand why females dominated the field at the Kellogg Biological Station farm.

The observed differences between the Kellogg Biological Station, Guthrie, and
Windsor farms are not surprising because local conditions within farmsteads are
different. Whether or not field populations (i.e. groups of interbreeding individuals, not
individuals moving into fields) are common in North American farmsteads cannot be
deduced from this study or the study conducted by Reimar & Petras (1968). However, the
results of this study are useful in generating hypotheses about general house mouse
habitat use patterns in the agricultural landscape. A better understanding of the
demographic characteristics of field populations may be helpful in predicting the impact
that agricultural practices, such as harvesting and application of pesticides, have on house
mice (for a discussion, see below). A better understanding of the timing of the
establishment and persistence of field populations may also help farmers to control

invasions of house mice into fields.

Response to cutting

The effects of cover removal vary for different small mammal species. Cover removal
has a negative impact on voles (e.g. Microtus pennsylvanicus, Eadie 1953; M. townsendii,
Taitt et al. 1981; M. ochrogaster, Kotler et al. 1988; M. canicaudus, Edge et al. 1995),
wood mice (Apodemus sylvaticus, Tew and MacDonald 1993) and cotton rats (Sigmodon

hispidus, Sietman et al. 1994). Other species, such as deer mice (Peromyscus

26

maniculatus, LoBue and Darnell 1959; Lemen and Clausen 1984; Kotler et al. 1988) and
western harvest mice (Reithrodontomys megalotis, Kotler et al. 1988), are unaffected or
respond positively to cover removal in fields. Before this study was conducted, only
anecdotal notes on the impact of harvests on house mice living in fields were recorded in
the literature (e.g. Linduska 1949, DeLong 1967; Kaufman and Kaufman 1990), and no
one had considered the effects of harvests on populations within barns. This study
supports previous work suggesting that house mouse numbers in fields decrease
following harvests (Linduska 1949) and provides limited evidence that house mice are
negatively affected by the repeated removal of cover in alfalfa fields. One mechanism for
this effect is that harvests may force mice that nest in or use fields back into barns,
increasing competition for space and food resources within barns.

More than half of the Kellogg Biological Station barn is bordered by alfalfa,
permitting mice access to the resources in the field. House mice were frequently captured
in the field when cover was high (Figure 3) suggesting that the field provides an
important resource to some individuals living in the barn. The field may have acted as a
refuge for individuals forced out of the barn; however, individuals rarely showed signs of
intraspecific aggression (Table 2). Harvesting had an immediate impact on mice using the
field (Fig. 3). Following harvests, house mice did not return to the field until at least the
thirteenth day of alfalfa regeneration (Fig. 3). LoBue and Darnell (1959) observed a
similar response by meadow voles (M. pennsylvanicus) in a harvested alfalfa field in
Wisconsin. Voles were frequently captured in alfalfa plots before a harvest but did not re-
invade plots until at least the seventeenth day following a harvest (LoBue and Darnell

1959).

27

Crop harvests cause increased dispersal of (Edge et al. 1995) and predation on
small mammals (Tew and MacDonald 1993). If a large proportion of individuals that
used alfalfa fields were not recaptured following harvests, then I could have argued that
dispersal and predation may have increased as a result of cutting. Based on the proportion
of house mice recaptured following harvests (Table 3), it is difficult to assess whether
harvests directly caused increased dispersal of or predation on house mice at the Kellogg
Biological Station farm. Twenty-two of 34 (64.7%) captures in the alfalfa field during
1997 and 4 of 9 captures (44.4%) during 1998 were recaptured in either the barn or the
field following harvests (Table 3). Whether these results are related to harvesting or
reflect different individual trappabilities (Hilbom et al. 1976) is not certain. Additional
observations suggest that house mice did not leave the system or die during harvests.
First, house mice fiom the barn and adjacent field were never captured in a nearby house
and fencerow following the 1997 harvests. Second, I did not find any dead house mice in
the field during visual surveys of the field immediately following harvests (both years),
suggesting that mice were either unharmed by tractors or were inside the barn during
harvests. One individual that was repeatedly tracked with radio-telemetry in the alfalfa
field before the 10 August 1998 harvest moved between the barn and field within a single
evening and showed a strong propensity to associate with the barn (Figure 2). Had stable
populations been forming in the field, I would have expected greater mortality in the field
and dispersal into areas other than the barn. Based on these observations, it seems that the
immediate impact of harvests was the removal of a resource that some individuals living

in the barn used and not the break-up of populations that formed in the field.

28

A downward trend in trap success in fields next to barns during a summer may
indicate that repeated harvests are effective at stopping mice from invading fields. During
1997, trap success in the field decreased through the summer (Figure 4), and the numbers
using the field decreased from 15 individuals before the 14 July harvest to 1 individual
between 14 July and 1 September 1997. Results fiom 1998 are more complicated,
possibly due to inter-annual differences or insufficient trapping before the 19 May 1998
harvest. Although a downward trend through the summer was not observed, trap success
in the alfalfa field was greater during the period between the first and second harvests
than the period between the second and third harvests. During both years, individuals
were often captured more than once in the field before alfalfa harvests. However, only
one individual during each summer was recaptured in the field following alfalfa harvests,
suggesting that disturbances in fields may impact individuals with previous experience in
fields. Behavioral experiments determining if house mice show a change in habitat
preference following repeated harvests are needed to test this hypothesis.

Harvests affect the movement patterns of mice living in fields (Tew and
MacDonald 1993). I anticipated that the harvesting of alfalfa next to the Kellogg
Biological Station barn would have affected the distances that house mice traveled into
the field from the barn. It is surprising that house mice traveled farther into the Kellogg
Biological Station field after the first harvest compared to those mice captured in the field
before the initial harvests. These observations may have resulted fiom one of the
following scenarios: 1. Repeated harvests may not hinder alfalfa growth above a critical
level and thus, have no effect on house mouse movements in fields or 2. Pre-harvest

levels may provide a challenge to house mice and following harvests, alfalfa may

29

regenerate to levels that house mice can navigate more easily. Alternatively, after the first
harvest of the season, house mice may have to travel greater distances in the fields to find
adequate resources. Harvests may impact the quality of the vegetation and affect the
insect communities associated with the alfalfa, forcing mice to travel farther from the
barn than is necessary during the period before initial harvests. Finally, the results
observed during 1997 may have been have been caused by the different trapping methods
used during the periods between harvests (Table 4).

Although the proportion of individuals weighing 16 g or more decreased between
harvests during both years (Table 5), it is not clear whether the age (as indicated by
weight) of individuals using the alfalfa field was altered by harvests. The sex ratio of
individuals using the alfalfa field was not affected by repeated harvests as females
dominated the field during all periods between harvests. These results stimulate many
questions about the effects of harvests on the demography of individuals using fields. At
the beginning of the summer, are adult females moving into the fields to establish nests?
By not returning to the field, are adult females responding to some negative experience
associated with harvests? In similar settings, are juveniles forced out the barn into fields?
If female-biased sex ratios are common in fields next to barns, harvests at these sites may
have profound effects on population growth, particularly if stressful events inhibit female
reproductive development or result in disrupted pregnancies.

Alternatively, agricultural activity may be of little consequence if resources
within the barns remain constant throughout the summer months or if fields are not easily
accessible. The alfalfa field at the Guthrie farm bordered an area of the barn in which

mice were infrequently captured, and only seven individuals used the alfalfa field before

30

the 20 June 1998 harvest. The number of individuals using the alfalfa field did not
increase as the alfalfa regenerated following the 20 June 1998 harvest, and radio-collared
mice were never tracked into the alfalfa field. Mice captured in more heavily populated
areas of the barn would have had to travel nearly the entire length of the barn (up to 27.4
m) and, presumably through male territories (Selander 1970) to gain access to resources
in the field. Under these conditions, harvesting practices in the field probably did not
have a major impact on the mice living in the Guthrie farm. Based on radio-telemetry and
limited trapping data, similar conclusions can be made about the impact of harvests on
mice at the Anthony farm. Trapping before the 4 June 1998 harvest indicated that house
mice used the alfalfa field when cover was high. However, six individuals tracked with
radio-telemetry did not use the alfalfa field during the two weeks preceding the 11
August 1998 harvest. Like the field at the Guthrie farm, the alfalfa field at the Anthony
farm may not have been easily accessible to mice within the barn. Radio-collared animals
ventured into an undisturbed horse paddock to the east of the barn, suggesting that for
these animals, the alfalfa field was either too far away or provided insufficient resources.
Several questions about the effects of harvests remain unresolved. Tew and
MacDonald (1993) demonstrated that wood mouse (A. sylvaticus) post-harvest nightly
activity in barley and wheat fields decreased significantly relative to pre-harvest levels
and that individual home ranges were smaller following harvests. If harvests force mice
back into barns, aggressive encounters may occur more frequently as the number of
individuals in the barn increases following a harvest. Consequently, individual home
range sizes may become smaller as individuals more aggressively defend their territories

against intruders. Do house mouse home ranges inside barns next to alfalfa fields

31

decrease after repeated harvests? The answer to this question may be difficult to establish
because the most widely accepted methods of home range estimation (see Larkin and
Halkin 1994; Worton 1995 for a review) produce estimates that extend beyond the walls
of barns even for animals that never used areas outside barns (Hayes, L.D., unpub. data).
Individual house mice may also respond differently to traps, potentially biasing home
range estimates based on trapping techniques. Numerous authors have reported
fluctuating population sizes in fields during the summer months (e.g. DeLong 1967;
Myers 1974). Do populations within barns undergo similar fluctuations and if so, are
populations affected by agricultural activity in adjacent fields? Estimates or indices of
population size require frequent and evenly spaced trapping periods. These requirements
conflict with the trapping effort required to estimate habitat use patterns, making it

difficult to determine if patterns are correlated to changes in density.

Future studies

Mowing in crop fields may serve as an effective means of population control for some
small mammals (Edge et al. 1995) and thus, the effects of mowing on rodent habitat use
and population processes warrant further study. While some investigators have studied
the impact of a single crop harvest on rodents (e. g. Edge et al. 1995), until this study, no
one has studied the effects of repeated harvests on small mammals. Since causal
mechanisms were not established, the results of this study should be used to generate
hypotheses about the effects of repeated harvests on small mammals in the agricultural
landscape. I present four alternative studies, two descriptive and two experimental, that I

believe are needed to determine the immediate (e. g. movement) and long-term effects

32

(e. g. population response) of repeated harvests on commensal (i.e. associated with
buildings) rodents.

Using radio-telemetry, Tew and MacDonald (1993) observed decreased
movements by and increased predation on wood mice (A. sylvaticus) after the harvest of
cropfields in the United Kingdom. I originally planned to use similar methods to
determine if house mice (n = 18-20) in fields moved back into barns following harvests. I
was unable to make these observations at the Guthrie and Kellogg Biological Station
farms because of unexpected changes in the harvest dates and the premature failure of
several radio-transmitter batteries. At the Anthony farm, radio-collars on four individuals
persisted through the harvest period. However, radio-collared individuals did not use the
alfalfa field near the barn making it impossible to assess the impact of the harvest. In
future studies, house mice need be tracked with radio-telemetry for a week before and
alter harvests to determine the effects of harvests on habitat use patterns. Additional
studies using radio-telemetry to track mice over several weeks (and consequently, before
and after multiple harvests) are needed to detemrine the effects of multiple harvests on
house mouse movements and habitat use patterns. A better understanding of house mouse
movements relative to harvests may be useful in making predictions about the effects of
harvests on population processes within barns.

Myers (1974) argued that house mouse population density in barns remains stable
due to constant food and cover resources. However, food may become limiting,
particularly if large males successfully defend clumped resources. Population processes
within barns may therefore be affected by the availability of resources outside barns. The

decrease in abundance that occurred in the Kellogg Biological Station barn during 1997

33

(Appendix B) may have been an indirect result of repeated harvests in the alfalfa field
next to the barn. At the Kellogg Biological Station farm, the alfalfa field may have
provided food resources or represented a sink habitat (Pulliarn 1988) in which
subordinate individuals from the barn could find adequate nesting sites. Removal of
vegetative cover and food resources in alfalfa fields adjacent to barns may effectively
limit mice to barns, intensifying competition for space and food resources. A suitable test
of this hypothesis could be made by estimating the monthly population density within
barns located next to uncut fields (n = 3-4), fields harvested once (11 = 3-4) and fields
harvested more than once (n = 3-4). I anticipate that house mouse populations within
barns next to repeatedly cut fields decrease in a manner similar to that observed in the
Kellogg Biological Station barn during 1997 (Appendix B). In buildings next to uncut
fields, resources may not become limiting and the peak density should be greater than
that in either of the alternative scenarios. Populations within barns next to fields that are
cut only once may show an intermediate rate of growth depending on the timing of the
harvest relative to peak breeding periods.

Manipulative approaches are needed to improve our understanding of small
mammal ecology (Krebs 1988). The effects of different mowing practices on house
mouse habitat use and population processes can be tested with a replicated design similar
to that described by Barrett and colleagues (e.g. Peles and Barrett 1996). Settings similar
to that at the Kellogg Biological Station farm can be simulated by building structures in
multiple alfalfa plots within an experimental landscape (see Peles and Barrett 1996). In
this design, three treatments (no cutting control, single harvest and repeated harvests) are

applied to the replicated plots in a completely randomized design (0. Schabenberger,

34

pers. com.) I anticipate that mortality and wounding will be high after the first harvest
and that a decrease in population density through the summer will occur in structures
surrounded by repeatedly harvested plots. Within control plots, mortality and wounding
should be minimal, and an increase in population density through the summer is
expected. Unlike the descriptive study I outline above, this design would permit insights
into causal explanations for changes in density occurring in structures within alfalfa plots.
Since facultative commensals (i.e. animals occasionally associated with human
dwellings), such as the deer mouse (P. maniculatus), may respond differently than house
mice to disturbances within their habitat (Clark et al. 1998), the design should also be
used to evaluate the effects of harvests on other rodent species.

Despite numerous studies on the genetic structure of house mouse populations
inside barns (e.g. Selander 1970) and in fields (e.g. Myers 1974), little is known about
house mouse metapopulation structure in the North American agricultural landscape (see
Merriam 1988). Metapopulation structure in the agricultural landscape may be affected
by human activity in fields and grassy areas between closely spaced barns. On many
farmsteads in southwest Michigan, strips of vegetation separate closely spaced barns,
providing individuals with potential dispersal routes. I hypothesize that dispersal from
populations within barns separated by mowed patches of grass is limited, resulting in
genetic drift within structures. This hypothesis can be tested by comparing the allele
frequencies in mice of known genotypes that are released into closely spaced structures.
Two treatments, mowed grass between structures and unmowed grass between structures,
must be applied. Tissue samples taken from the released population and from the

descendant population after a period of time are used to detect changes in allele

35

frequencies within structures. If mowing of the grass between structures inhibits
dispersal, gene flow will not occur and ‘new’ alleles will not be detected within
structures. However, if mowing has no effect on dispersal between the structures, mice
from both structures should mix, and a shift in allele frequencies within populations
should be detected. Since house mice may also move along fencerows (Kaufman and
Kaufman 1989; Clark et al. 1996), a similar study designed to compare gene flow
between barns connected by fencerows and barns without connecting fencerows is

needed.

Concluding remarks

House mice cause damage to stored food stuffs and may spread disease within the
agricultural landscape. Studies based on trapping methods suggest that house mouse
populations within buildings are highly structured (e.g. Selander 1970). Based on these
studies, one could potentially view barns within the agricultural landscape as islands of
house mouse habitat. Merriam and colleagues’ (see Merriam 1988 for a review) work on
white-footed mice (P. Ieucopus) in agricultural systems suggests that small mammals use
fencerows to move more freely within in the agricultural landscape than has been
previously thought (see Cummings and Vessey 1994). House mice may be able to move
more freely in fields than in barns; feral (i.e. field-dwelling) house mice have greater
home ranges than commensal (i.e. associated with buildings) house mice (Bronson 1979).
In the agricultural landscape, house mice may be able to move between barns if dispersal
corridors (e.g. fencerows, strips of vegetation) are present. Removal of vegetation

between buildings may effectively limit mice to within buildings, affecting

36

metapopulation structure. Under these conditions, populations in a single building may
make up a single metapopulation. Alternatively, if adequate dispersal routes remain
between buildings, populations within a series of barns (and adjacent fields) may make
up a metapopulation. House mouse habitat use patterns presented in this study are useful
in predicting the. effects of harvests on the distribution of house mice within the
agricultural landscape. Future studies on the effects of mowing on house mouse
populations in fields and barns are needed. A better understanding of how harvesting
practices affect house mice and other commensal rodents may improve our understanding
of small mammal metapopulation structure in the agricultural landscape. Advances in
these areas should be useful in planning and designing more efficient pest control

programs.

37

REFERENCES

Bowers, MA. and SF. Matter. 1997. Landscape ecology of mammals: relationships
between density and patch size. Journal of Mammalogy 78: 999-1013.

Bradley, J .V. 1968. Distribution-free statistical tests. Prentice-Hall, Inc., Englewood
Cliffs, New Jersey. 388 p.

Bronson, F.H. 197 9. The reproductive ecology of the house mouse. Quarterly Review of
Biology 54: 265-299.

Clark, B.K., B.S. Clark, T.R. Homerding and WE. Munsterman. 1998. Communities of
small mammals in six grass-dominated habitats in southeastern Oklahoma. American
Midland Naturalist 139: 262-268.

Clark, B.K., B.S. Clark, W.E. Munsterrnan and TR. Homerding. 1996. Differential use
of roadside fencerows and contiguous pastures by small mammals in southeastern
Oklahoma. Southwestern Naturalist 41: 54-59.

Cummings, J .R. and SH. Vessey. 1994. Agricultural influences on movement patterns of
white-footed mice (Peromyscus Ieucopus). American Midland Naturalist 132: 209-218.

DeLong, K.T. 1967. Population ecology of feral house mice. Ecology 48: 611-634.

Eadie, W.R. 1953. Response of Microtus to vegetative cover. Journal of Mammalogy 34:
263 -264.

Edge, W.D., J .O. Wolff and R.L. Carey. 1995. Density-dependent responses of gray-
tailed voles to mowing. Journal of Wildlife Management 59: 245-251.

Fitzgibbon, CD. 1997. Small mammals in farm woodlands: the effects of habitat,
isolation and surrounding land-use patterns. Journal of Applied Ecology 34: 530-539.

Henderson, M.T., G. Merriam and J. Wegner. 1985. Patchy environments and species
survival: Chipmunks in an agricultural mosaic. Biological Conservation 31: 95-105.

Henein, K., J. Wegner and G. Merriam. 1998. Population effects of landscape model
manipulation on two behaviorally different woodland small mammals. Oikos 81: 168-
1 86.

Hilbom, R., J .A. Redfield & C.J. Krebs. 1976. On the reliability of enumeration for mark
and recapture census on voles. Canadian Journal of Zoology 54: 1019-1024.

38

Kaufman, D.W. and GA. Kaufman. 1989. Nongame wildlife management in central

Kansas: implications of small mammal use of fencerows, fields and prairie. Transactions
of the Kansas Academy of Science 92: 198-205.

Kaufman, D.W. and GA. Kaufman. 1990. House mice (Mus musculus) in natural and
disturbed habitats in Kansas. Journal of Mammalogy 71: 428-432.

Khan, Akbar Ali and MA. Beg. 1990. Population dynamics of the Persian house mouse
in the croplands of central Punjab. Pakistan Journal of Zoology 22: 81-87.

Kotler, B.P., M.S. Gaines and B.J. Darrielson. 1988. The effects of vegetative cover on
the community structure of prairie rodents. Acta Theriologica 33, 27: 379-391.

Krebs, C.J. 1988. The experimental approach to rodent population dynamics. Oikos 52:
143-149.

Krebs, C.J., Kenney, Al and Singleton, GR. 1995. Movements of feral house mice in
agricultural landscapes. Australian Journal of Zoology 43: 293-302.

Kurta, A. 1995. Mammals of the Great Lakes region. The University of Michigan Press,
Ann Arbor. 366 p. '

Larkin, RP. and D. Halkin. 1994. A review of software packages for estimating animal
home ranges. Wildlife Society Bulletin 22: 274-287.

Lemen, CA. and MK. Clausen. 1984. The effects of mowing on the rodent community
of a native tall grass prairie in eastern Nebraska. Prairie Naturalist 16: 5-10.

Levins, R. 1969. Some demographic and genetic consequences of environmental
heterogeneity for biological control. Bulletin of the Entomological Society of America
15: 237-240.

Linduska, J .P. 1949. Ecology and land-use relationships of small mammals on a
Michigan farm. Ph.D dissertation. Michigan State University, E. Lansing, Michigan.

LoBue, J. and RM. Darnell. 1959. Effect of habitat disturbance on a small mammal
population. Journal of Mammalogy 40: 425-437.

Lorenz, G.C. and G.W. Barrett. 1990. Influence of simulated landscape corridors on
house mouse (Mus musculus) dispersal. American Midland Naturalist 123: 348-356.

Merriam, G. 1988. Landscape dynamics in farmland. Trends in Ecology and Evolution 3:
16-20.

Middleton, J. and G. Merriam. 1981. Woodland mice in a farmland mosaic. Journal of
Applied Ecology 18: 703-710.

39

Myers, J .H. 1974. Genetic and social structure of feral house mouse populations on
Grizzly Island, California Ecology 55: 747-759.

Newsome, A.E. 1969. A population study of house-mice permanently inhabiting a reef-
bed in south Australia. Journal of Animal Ecology 38: 341-359.

Nupp, TE. and R.K. Swihart. 1998. Effects of forest fragmentation on population
attributes of white-footed mice and eastern chipmunks. Journal of Mammalogy 79: 1234-
1243.

Peles, J .D. and G.W. Barrett. 1996. Effects of vegetative cover on the population
dynamics of meadow voles. Journal of Mammalogy 77: 857-869.

Peles, J .D., C.K. Williams and G.W. Barrett. 1997. Small mammal population dynamics

in strip-cropped vs. monoculture agroecosystems. Journal of Sustainable Agriculture 9:
51-60.

Pulliam, HR. 1988. Sources, sinks, and population regulation. American Naturalist 132:
652-661.

Reimar, J .D. and Petras, ML. 1968. Some aspects of commensal populations of Mus
musculus in southwestern Ontario. Canadian Field Naturalist 82: 32-42.

Rowe, F .P., T. Swinney and R]. Quy. 1983. Reproduction of the House mouse (Mus
musculus) in farm buildings. Journal of Zoology (London) 199: 259-269.

Selander, R.K. 1970. Behavior and genetic variation in natural populations. American
Zoologist 10: 53-66.

Sietman, B.E., W.B. Fothergill and El. Finck. 1994. Effects of haying and old-field
succession on small mammals in tallgrass prairie. American Midland Naturalist 131: 1-8.

Singleton, G. 1989. Population dynamics of an outbreak of house mice (Mus domesticus)
in the mallee wheatlands of Australia-hypothesis of plague formation. Joumal of Zoology
(London) 219: 495-515.

Stickel, LP. 1979. Population ecology of house mice in unstable habitats. Journal of
Animal Ecology 48: 871-887.

Szacki, J ., J. Babinska-Werka and A. Liro. 1993. The influence of landscape spatial
structure on small mammal movements. Acta Theriologica 38: 113-123.

Taitt, M.J., H.W. Gipps, C.J. Krebs and Z. Dundjerksi. 1981. The effect of extra food and
cover on declining populations of Microtus townsendii. Canadian Journal of Zoology 59:
1 593-1599.

40

Takada, Y. 1985. Habitat utilization and mainland populations of the feral house mouse,
Mus musculus molossinus. Journal of the Mammal Society of Japan 10: 123-134.

Tattersall, F. H., D.W. MacDonald, W.J. Manley, S. Gates, R. Feber and B.J. Hart. 1997.
Small mammals on one-year set-aside. Acta Theriologica 42: 329-3 34.

Tew, TE. and D.W. MacDonald. 1993. The effects of harvest on arable wood mice
(Apodemus sylvaticus). Biological Conservation 65: 279-283.

van Apeldoom, R.C., W.T. Oostenbrink, A. van Winden and FF. van der Zee. 1992.
Effects of habitat fragmentation on the bank vole, Clethrionomys glareolus, in an
agricultural landscape. Oikos 65: 265-274.

Wegner, J. and G. Merriam. 1990. Use of spatial elements in a farmland mosaic by a
woodland rodent. Biological Conservation 54: 263-276.

Wegner, J. and G. Merriam. 1987. Spatial and temporal distributions of woodland mice
(Peromyscus Ieucopus) in farm crops and fencerows. Bulletin of the Ecological Society
of America 68: 442.

Wolff, J 0., EM. Schauber and W.D. Edge. 1997. Effects of habitat loss and
fragmentation on the behavior and demography of gray-tailed voles. Conservation
Biology 11: 945-956.

Worton, B.J. 1995. Using Monte Carlo simulation to evaluate kemel-based home range
estimators. Journal of Wildlife Management 59: 794-800.

Zar, J .H. 1984. Biostatistical analysis, 2'"1 edition. Prentice-Hall, Inc., Englewood Cliffs,
New Jersey. 718 p.

Zollner, PA. and S.L. Lima. 1997. Landscape-level perceptual abilities in white-footed
mice: perceptual range and the detection of forested habitat. Oikos 80: 51-60.

41

TABLES

42

Table 1. Number of individuals and total number of captures in each habitat type that was
trapped at the Guthrie and Kellogg Biological Station (KBS) farms’. Chi square values
are based on the expected number of individuals captured divided by the trap effort (total

number of traps set at each site) in each habitat type.

 

Study Habitat Number of Total number of Trap Chi
location type individuals captures effort square
(# of
traps set)
KBS (1997) Barn 95 336 1764 177.82“
Alfalfa 31 45 5470
KBS (1998) Barn2 38 130 1527 6669*
Alfalfa 13 27 4582
Guthrie Barn3 164 486 1933 256.47*
(1998)
Alfalfa 8 8 3292
Uncut 37 76 1247
field

1 Based on morning captures

2 Chi square calculations based on trapping dates when raccoons did not disturb traps
3 Does not include 1 new individual and 12 total captures on 27 May 1998 because the
number of traps set was not recorded

P < 0.05

43

Table 2. Sex and weight of and prevalence of furless patches on individuals captured in
the Guthrie and Kellogg Biological Station alfalfa fields. The number of females in each

weight class and with firrless patches is in parentheses.

 

 

Sex Weight class
Location Males Females 16+ g <16 g Both Furless
weight patches
classes1 on rump
Kellogg Biological 13 20 16 16 1 6
Station (1997) (10) (8) (1) (3)
Kellogg Biological 4 10 8 5 1 1
Station (1998) (5) (4) (1) (0)
Guthrie 4 5 5 4 0 0
(1998) (2) (3)

1 Individuals weighing <16 g and 16 g or more during two different sampling dates

2 One individual not examined for fur patches. See text for detailed explanation of weight
class designation for three individuals not weighed in the alfalfa field. One female that
was not weighed within a reasonable period of time is not included

3 Weight class assignment for two individuals based on measurements made inside the
barn. See text for a more detailed explanation

44

Table 3. Number and proportion of house mice that were recaptured following harvests
and whose most recent captures before harvests were in the alfalfa field.
Harvest date Most recently Recaptured following Proportion recaptured

captured in field a harvest following a harvest
before harvest

 

Guthrie Family F arm
20 June 1998 6 5 0.83
24 July 1998 l 0 0.00

Kellogg Biological Station

6 July 1998 7 2 0.29
10-11 August 2 ' 2 1.00
1998

11 June 1997 18 16 0.89
14 July 1997 15 5 0.33
1 September 1 1 1.00
1997

45

Table 4. Average distances and ranges of distances from the Kellogg Biological Station

barn that house mice were captured in the alfalfa field.

 

Inter-harvest period Number of Avg. dist. Range of Distance
captures from barn (m) distances between traps

(SE) (m) (m)

8-11 June 1997 301 17.7 9.1-36.6 4.6
(1.2)

12 June-14 July 21 46.5 11.9-80.7 7.6

1997 (3.5)

15 July-15 Aug. 1 11.9 11.9 7.6

1997

1 Sept-19 Oct. 1 4.32 4.3 7.6

1997

20 May-6 July 1998 21 13.6 6.1-28.8 9.1
(1.7)

7 July-5 August 6 19.6 15.2-25.1 9.1

1998 (2.0)

1 One individual that was captured against the edge of the barn was not included.
2 The first trap was approximately 4.3 m from the edge of the barn.

46

Table 5. Proportion of females and large individuals (16 g or more) that used the alfalfa
field during the periods between harvests at the Kellogg Biological Station. Proportions
are based on all captures, including those made in afternoon trapping sessions. Females

and individuals weighing 16 g or more are in parentheses. See methods for harvest dates.

 

Variable measured Year Before harvest Before harvest Before harvest
1 2 3
Proportion of females 1998 0 0.73 0.75
(8) (3)
1997 0.61 0.64 1.00
(11) of (1)
Proportion weighing 16 g or 1998 0 0.75 0.25
more (9) (1)
1997 0.89 0.132 Unknown
(16) (2)

1 One individual of unknown sex (11 = 15 total animals)
2 One individual that weighed <16 g and 16 g or more on two different dates was counted
once in each weight class category

47

FIGURES

48

Proportion of individuals

 

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Proportion of captures in barn

I 1998 all trapping dates D 1998 barn and field trapped simultaneously 31997

 

 

 

 

 

 

 

 

 

 

 

 

 

 

B:
l
0.9 r_
{’3’ 0.8 ~
5 0.7 .
'5 06
.8 '
“a 0.5 .
8 04
g. 0.3 ~
E 0.2 .
0.1 r
O ‘l'hI I —T I rm I I I I I I I I I I an E

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Proportion of captures in barn
I All trapping dates El Barn and fields trapped simultaneously
Figure 1. Proportions of individuals showing various proportions of captures in
barns at the Kellogg Biological Station (A) and Guthrie (B) farms. Only

individuals caught four or more times during morning trapping sessions are
included.

49

 

 

 

 

Number of individuals
N
lT

 

 

 

 

 

 

 

 

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Proportion of barn locations

I Kellogg Biological Station 5 Anthony D Guthrie

Figure 2. Number of individuals showing various proportions of telemetry
locations in barns at the Kellogg Biological Station (11 = 2 individuals), Anthony (11
= 6) and Guthrie (n = 10) farms.

50

 

 

 

 

 

 

 

Number of captures m
the alfalfa field
o N A O\ on

13 14 15 25 26 27 30 32 33
Days since 11 June 1997 alfalfa harvest

OWNW-kvr

 

Number of captures in
the alfalfa field

7 91422252729313638444648
Days since 19 May 1998 harvest

 

 

 

 

 

 

0 I I j I I T I I I

8 91011121314151724252627282930
Days since 6 July 1998 alfalfa harvest

Number of captures in
the alfalfa field

Figure 3. Total number of afternoon and morning captures in the alfalfa field at the
Kellogg Biological Station on the corresponding days since alfalfa harvests in 1997
(A) and 1998 (B, C). Only one individual was captured in the field during the
period between the 14 July and 1 September 1997 alfalfa harvests.

51

 

 

 

 

 

 

 

0.025
V)
g 0.02
a 0.015
g 0.01
E—I 0005 0.0010 011110
0
6-11 June 1997 12 June-14 July 15 July-28 6 Sept-19 Oct.
1997 August 1 997 1997
I Total captures/T raps set [:1 Individuals/T raps set
B:
0.01
U)
§ 0.008
g 0.006
g 0.004
[—4 0'00: 0.0000 0.0000 0.0000 0.0000
17-19 May 20 May-6 July 7 July-5 August 12-25 August
I Total captures/T raps set [:1 Individuals/T raps set
C:
O ' 004 0.0033 0.0033
g 0.003 —
a 0.002 _ 0.0017 0.0017
g: . 0.0010 0.0010
“ 0'00“ j |
0 — 1 , .

 

 

 

 

 

 

23 May-20 June 21 June- 24 July 25 July-24 August

I Total captures/T raps set E] Individuals/T raps set

Figure 4: Trap success during morning trapping sessions in the alfalfa fields at the
Kellogg Biological Station (A, B) and Guthrie (C) farms. Number of individuals
captured per period: (A) 15, 15, 1, 1; (B) 0, 10, 4, 0; (C) 6, l, 1. Total number of
captures per period: (A) 21, 21, 1, 1; (B) 0, 21, 6, 0;(C)6, 1,1.

52

APPENDICES

53

APPENDIX A

Common and scientific names of plants found in the uncut fields at the Anthony and

Guthrie farms.

Anthony

Common Name

Couch grass
Japanese brome
Orchard grass
Smooth brome
Timothy

Guthrie
Common Name

Common burdock
Curled dock
Dandelion

Field chamomile
Field pennycress
Field peppergrass
Hedge mustard
Hoary alyssum
Lady’s Thumb
Motherwort
White avens
White campion
White sweet clover

Scientific Name

A gropyron repens
Bromusjaponicus
Dactylis glomerata
Bromus inermus
Phleum pratense

Scientific Name

Arctium minus
Rumex crispus
Taraxacum ofi‘icinale
Arthemis arvensis
Thlaspi arvense
Lepedium campestre
Sisymbrium ofi‘icinale
Berteroa incana
Polygonium persicaria
Leonurus cardiaca
Geum canadense
Lychnis alba
Meliotus alba

54

APPENDIX B

Trap success (number of individuals captured/number of traps set) and number of
individuals captured in the Kellogg Biological Station barn between June and
August 1997.

 

 

 

0.4 “r a” 50 'o
O
a 0.3 -— 1’ 40 g.
g A _+ 30 g
a 0.2» g
i 01 " 2° a
I— . ~— -
-~ 10 '6’
.S
0 I I I I I I I 0 4*
0 V \.
«so? 88$ sf if at" 42? i 43‘!"
’\ B °o °o o e e
x v > .N W Y" Yr Yr
\ x W In > 51'

-l- Trap success +Number of individuals captured

55

APPENDIX C

Average (i SE) proportions of barn captures of mice captured four or more times.

 

Location Male Female Total

Guthrie

All trapping data 0.86 d: 0.07 0.96 :I: 0.03 0.92 :t 0.04
(n=21) (n=30) (n=51)

Barn and fields trapped 0.90 i 0.07 0.99 r 0.01 0.95 i 0.03

srmultaneously (n = 17) (n = 21) (n = 38)

Kellogg Biological Station (I 998)

All trapping data 0.88 i 0.07 0.82 i 0.07 0.84 i 0.05
(n=7) (n=14) (n=21)

Barn and field trapped 1.0 r. 0.0 0.88 i 0.13 0.93 i 0.07

simultaneously (n = 3) (n = 4) (n = 7)

Kellogg Biological Station (1997)

All trapping data 0.90 i 0.05 0.87 i 0.03 0.88 i 0.03
(n= 15) (n=21) (n=36)

56

APPENDIX D

Indoor and outdoor radio-telemetry locations and proportion of barn locations of
individuals tracked at the Anthony (11 = 6), Kellogg Biological Station (KBS) (n = 2) and

Guthrie (n = 10) farms during 1998.

 

Location IDl Sex Indoor Outdoor Proportion of
locations2 locations3 indoor
locations
Anthony 448* Male 49 5 0.91
Anthony 1 13 * Male 70 0 1 .00
Anthony 90* Male 68 0 1 .00
Anthony 265* Female 56 3 0.95
Anthony 144* Female 39 3 0.93
Anthony 125* Female 29 0 1.00
KBS 405 Male 41 7 0.85
KBS 247* Female 55 0 1 .00
Guthrie 10 Male 0 6 0.00
Guthrie 53 Male 0 40 0.00
Guthrie 386* Male 19 17 0.53
Guthrie 405 Male 8 22 0.27
Guthrie 265-2“ Male 29 0 1 .00
Guthrie 24* Female 0 6 0.00
Guthrie 226* Female 24 0 l .00
Guthrie 265-1 Female 2 5 0.28
Guthrie 366 Female 5 12 0.29
Guthrie 448* Female 26 1 0.96

l: Radio-transmitter fiequency

2: Barns or silos

3: Fields, outer edge of barns, and grass areas near barns

* Indicates that the animal was captured in the barn when the radio-collar was attached

57

APPENDIX E

Number of individuals captured in alfalfa fields, total number of captures in alfalfa fields
and number of traps set in alfalfa fields during morning trapping periods before and after
alfalfa harvests. Afternoon captures are not included because traps were not left open

through the afternoon on all dates.

 

Trapping period Number of Number of captures Number of traps set
individuals in the in the alfalfa field
alfalfa field
Guthrie
23 May-20 June 6 6 1800
1 998
21 June-24 July 1 1 1010
1998
25 July-24 Aug. 1 l 582
1998

Kellogg Biological Station

17-19 May 1998 0 0 288
20 May-6 July 1998 10 21 2712
7 July-5 Aug. 1998 4 6 1360
12-25 Aug. 1998 0 O 510
6-11 June 1997 15 21 975
12 June-14 July 15 21 1449
1997

15 July-28 Aug. 1 1 2080
1997

6 Sept-19 Oct. 1997 1 1 966

58

"Illllllllllllllllll“