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ECOLOGICAL EVALUATION OF LARGE
TREE CAVITIES AND GROUND BURROWS ‘
AND THEER USE BY RACCOONS

Thesis for “as Degree of M. S.
MICHIGAN STATE UNIVERSITY

Alfred Berner ‘
1965

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Michigan State

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ROOM USE ONE.

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TO AVOID FINES return on or before date we.
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MSU Is An Affirmative ActiorVEqual Opportunity Institution
‘ *' 751.13VJ‘f

ABSTRACT

ECOLOGICAL EVALUATION OF LARGE TREE CAVITIES
AND GROUND BURROWS AND THEIR USE BY RACCGCNS

by Alfred Berner

This ecological study was undertaken to describe the
cavities and burrows used by racoons, to determine the
amount and time of use and the microclimates of tree cavi—
ties and ground burrows; and to evaluate the relationship of
environmental factors to the use of cavities and burrows by
raccoonso

All the tree cavities and ground burrows located in
the study area were examined and measuredu Microclimates of
some of the dens were studied by the use of temperature re-
corders and direct observationsu Den use was monitored by
using wire-metal tube switches and an Esterline Angus
event recordero

Of the 13 dens located in the study area, ten were
tree trunk cavities, two were tree base cavities; and one
was a ground burrow° These 13 dens were monitored for 180
dayso The natural ground burrow had the most raccoon
activity! and also the most stable microclimate; the average

daily temperature fluctuation was lOSOFo The most used tree

Alfred Berner

cavity was usually warmer than the ground burrow, and had an
average daily temperature fluctuation of 8,7OF. Most of the
raccoon activity occurred fromcnualunufbefore sunset to two
hours after sunriseo Raccoons were active around dens
during the daylight hours, but in most instances, this was
due to raccoons sunning themselves at the entranceso

Raccoon den use was found to be influenced by the
sunrise-sunset times, the construction and microclimate of
the cavity or burrow, and by the external temperature
fluctuationo The raccoon den activity appear to be regu-
lated more by the sunset than by the sunriseo The size and
how well a den sheltered the raccoon from adverse weather
conditions appeared to have a direct influence on den use,
Also, the construction of the den may have influenced the
microclimateo It was indicated by differential use, that
in most cases microclimate was the most important factor
regulating the type of raccoon use) investigational and
restg The external temperature fluctuations above 350? af-
fected den activity in the following manner, An increase in
temperature brought about a general decrease in activity
while a decrease in temperature brought about an increase in
activity. Below 350E this trend was reversed. Also, above
4OOF the predominant type of den use was investigational and

below 4OOF it was rest use,

ECOLOGICAL EVALUATION OF LARGE TREE CAVITIES

AND GROUND BURROWS AND THEIR USE BY RACCOONS

BY

Alfred Berner

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Fisheries and Wildlife

1965

 

777,47 (WK/925’

I
L//

AC KNOWLE DGME NT S

I wish to express my appreciation to Dr. Leslie
Gysel for initiating the study and for the equipment he
supplied. Also, I would like to thank him for the aid and
guidance he gave me during the study and during my stay
at Michigan State University,

I wish to thank Dr. Rollin Baker and Dr. John King
for their help, suggestions and for editing the manuscript.

Lastly, my heart warmed thanks go to my wife Mary,
whose encouragement and confidence helped me through the

rough moments,

ii

TABLE

INTRODUCTION . o a o . a

 

STUDY AREA . a . o o o 0
LOCATION o . o o o o
PHYSIOGRAPHY . o . 0
FOREST COMMUNITIES

O O

0 O

O O

0

Cut, Unmanaged Stand

Uncut,

0

O

O

0

O

0

OF CONTENTS

0 O

O 0

(Hudson) .

Cut, Managed Stand (Maple)

Cut, Grazed, Unmanaged Stand
SEASONAL CLIMATIC CONDITIONS

METHODS O O O O O O O O

LOCATING AND MEASURING DENS

USE DETERMINATION 0

ANALYSIS OF THE MICROCLIMATES
ANALYSIS OF THE MACROCLIMATE

ANALYSIS OF DEN USE

RECORDED USE INTERPRETATION

Assumptions 0 .

 

Definition_gf Use Units

 

O 0

O 0

O O

O 0

D

O

0

 

MOVEMENT ANALYSIS 0

.RESULTS , a o o o o ,

INDICATION OF THE NUMBER OF RAC“
GENERAL MOVEMENT PATTERNS

DENS LOCATED o o o 0
Types 0 o o o a
Location 0 o o a
Description a o
Surroundings o .

MICROCLIMATES . o o

MACROCLIMATE o . o

RECORDED ACTIVITY AT

 

 

O O

O O

DEN

O

 

Interpreted Activity

 

iii

0

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

_ENTRANCE D
Total Activity Per Den

0

O

Unmanaged Stand (Toumey)

O O

(Grazed)'

O 0

O O

O 0

0

O

Page

[-4

W'xlish-QD‘DNNN

Page

ENVIRONMENTAL FACTORS EFFECTING DEN USE , o o o o o a 48
STRUCTURE AND MICROCLIMATE . a o o o o o o . . o . 48
SURROUNDINGS a . o o o o o a o o o . . o . o o o o 58
TIME OF SUNRISE AND SUNSET . o o o . o o o . o o o 60
CLIMATIC FACTORS . o . o o . . . o . o o o . . a . 62

 

 

 

Temperature . . o o o a o o o . a . o a . o o 65
Precipitation . . o o a a o . . . o o . o . o 72
Wind 0 O O O O O 0 O ’ O O O O O O O C 0 0 0 O 74

SUMMARY AND CONCLUSIONS 0 o . . t o o o o . o . . . o 75

 

LITERATURE CITED 0 O O O O O O O 0 O O O O 0 O O O O 0 79

 

iv

Tables

10.

11°

LIST OF TABLES

A list of the woody plant species identified
in Grazed woodlot . . o . . . o . . . . . .

The number of raccoons trapped and trap-
nights for each of the five traplines . . o

Raccoons that were captured in more than one
trapline I O O O O O O O 0 O O O O O 0 O O 0

Measurements taken of nine tree trunk cavi-I
ties and the raccoon activity recorded for
ten tree trunk cavities . . o a . . . . . 0

Measurements taken of the two tree base
cavities and the raccoon activity recorded
for them 0 0 O 0 O O 0 O O O O 0 O O O O O 0

Measurements taken of the three ground
burrows and the raccoon activity recorded
fOr eaCh O O O O O O O O O O O O O O O O O 0

Number of feet from den to important con-
stituents of the surrounding communities a .

The average daily temperature readings in-
side and outside the dens for the six months
of the study a . o o o o o a . o a . o . o 0

Monthly macroclimatic conditions for the
six months of the study a a a . o . o . o .

Summarized amounts of uninterpreted daily'
activity 0 O O O G O o 0 O O O O O 0 O 0 O 0

Summary of recorded investigational rest
actiVity O O I O O O O 0 O O O O O O O O 0 0

Page

10

23

25

31

32

32

36

39

44

46

47

11°

12°

13°

LIST OF FIGURES

The general study area on the University
farm property a . . . o o . o . . . . . 0

Hudson woodlot and surrounding communities
Toumey woodlot and surrounding communities
Maple woodlot and surrounding communities

Ungrazed portion of Grazed woodlot with
cavity 13 in the foreground . . . . o . o

Grazed portion of Grazed woodlot with
Cavity 11 in the foreground . o o o o 9 .

Intensive study area, Grazed Woodlot, and
surrounding communities a . o o o . o o .

Tree cavity data card . o o o o o a . o 0
Ground burrow data card a o o . a . a . o

Directional switches installed at the
entrance to Cavity 2 . o a . . o . a a o a

Location of the tree cavities and ground
burrows in Grazed woodlot a o . . . o o o

Limb sheltering the entrance to Cavity 9 0

Two raccoons at the entrance of ground
burrow Number 14 . . . o a o o o o o o . .

vi

Page

11

ll

12

15

15

19

29

54

54

LIST OF GRAPHS

Graphs Page

1. Maximum and minimum monthly averages for tree
cavities l, 8 and 11 for the six months of
the Study 0 O O O 0 O 0 O O O 0 O O O O O 0 0 4O

2, Maximum and minimum monthly averages for
ground burrows l4 and 19 for the six months
of the study . . . . . a o . . o . . . . o . a 42

3° Cumulative uninterpreted activity per hour

for each of the first three months a . . o o o 61
4, Cumulative uninterpreted activity per hour

for each of the second three months a . o o o 63
5. Cumulative uninterpreted activity per hour

for the six months of the study 0 . o o o o a 64

69 The relation of temperature fluctuation to
den aCtiVity O O O O 0 0 O O 0 O O O O o O O O 66

7. Relationship of temperature to the types of

den use a . . o o o o o . o o o o o o o . o . 68
8, Relationship of temperature to investi-

gational use a o . o o . a o . o . . . o o . o 70
90 Relationship of temperature to rest use a a a 71

10° Relationship of temperature to the total
interpreted activity a o o o o o o o o o o o o 73

vii

Ecological evaluation of large tree cavities
and ground burrows and their use by raccoons

INTRODUCTION

 

Tree cavities and ground burrows have long been
known to be important forms of shelter used by many species
of mammals. Despite this fact, little is known of the true
ecological picture and importance of these two types of
shelter.

Data, collected on the denning habits of raccoon
(Procyon lotor), indicate that tree cavities and ground
burrows are the principal den types used (Steuwer, 1943,
Butterfield, 1954 and Dorney, 1954). These data also point
out the possibility that a lack of available shelter, par-
ticularly of the types mentioned, has a definite regulatory
effect on raccoon population. In spite of the apparent
importance of dens in the ecology of the raccoon, very few
detailed studies have been made to determine the character~
istics of suitable raccoon dens. There is even less infor-
mation on the amount of daily and seasonal use and on the
environmental factors influencing the time and amount of use.

This study was initiated in June of 1964 and carried

on through December of 1964 in an attempt to accomplish the

following objectives: (1) To describe tree cavities and
ground burrows utilized by raccoon; (2) to determine the
amount and time of raccoon use; (3) to determine the micro-
climates of tree cavities and ground burrows; and (4) to
indicate and evaluate environmental factors influencing the

use of cavities and burrows by raccoons.
STUDY AREA
LOCATION

The land selected as the study area is part of the
Michigan State University farm property south of the campus

at East Lansing, Ingham County, Michigan.
PHYSIOGRAPHY

The general study site* has a surface area of 2.39
square miles (1,529 acres) and is two miles long and 1.62
miles wide (Fig. l). The topography of the area is gently
rolling farmland. It is extensively cultivated. This is
demonstrated by the fact that only 6.5 percent of the total
acreage is in woodlots, while the remaining 93.5 percent is

being used for agricultural purposes (Figs. 2, 3, 4 and 5).

 

*The size of the general study area was determined
by circumscribing a circle, a mile in diameter, around each
of the four woodlots and consolidating all the land within
the circles into one tract.

 

The general study area on the University

farm property.

Figure l:

FOREST COMMUNITIES

The four principal woodlots on the study area are
all similar, yet, each has its own distinguishing character—
istics. The largest of the four forest communities is a

sugar maple (Acer saccharum) - beech (Fagus grandifolia)

 

stand of 19 acres called Hudson woodlot (Fig. 2). The 19
acre stand is divided into two, approximately equal,
sections. The unmanaged, northern half contains trees of
all ages and is well stocked with mature sugar maples and
beeches. The cut south section is an even-aged stand of
young sugar maple, beech and white ash (Fraxinus americana).
The even—age condition is due to cuttings made in 1925 and
1930 which removed the good growing, mature stock of the
tree species previously mentioned (Gysel, 1961).

Almost all the tree cavities present in this stand
are concentrated in the northern section. This is due to
the age of the trees present and to the large amount of de-
cay in the boles, crowns and bases of the mature trees, par-
ticularly the beech. There is also a large number of ground
burrows in the sandy surface soil of the Spinks loamy sand.

Toumey woodlot is a 17.5 acre, old—growth, unmanaged
stand (Fig. 3). It is uncut and ungrazed. It is well
stocked with sugar maple, beech and basswood (Tilia americana)
of all ages. The trees range in size from seedlings up to

40 inches in d.b.h. (Gysel, 1961).

 

 

 

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Hudson woodlot and surrounding
communities.

 

Hayfield

Veterinary
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Buildins' Old field

Pasture

TOUHKY
HOODLOT

Christmas
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Groin
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Hayfield

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HUDSON
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HOODLOT

 

Figure 3: Toumey woodlot and surrounding
communities.

There are a large number of tree cavities, most of
which are in the mature and over-mature trees. Gysel (1961)
found an average of 34 cavities per acre; 3 percent of the
34 had entrances of 4 inches or larger. This gives a calcu—
lated density of one to two cavities per acre large enough
for possible raccoon use. Ground burrows are scarce in the
Hillsdale sandy loam of the woodlot.

Maple woodlot is a 16.1 acre managed stand of sugar
maple (Fig. 4). The present homogenous condition of this
woodlot was produced by selective cuttings which eliminated
most other tree species and poor sugar maple stock. These
cuttings also removed many tree cavities of raccoon size;
however, the stand is well stocked with sugar maples of all
sizes from seedlings to ones with 26 inches d.b.h. There is
also a lack of ground burrows in the Miami loam soil of the
woodlot.

The smallest of the woodlots, Grazed, was choosen as
the intensive study area; this was because it possesses the
following specific characteristics: (1) It appears to be
supporting a sizeable raccoon population; (2) there is
present a sufficient number of tree cavities and ground
burrows of raccoon size; and (3) these cavities and burrows
are all located within a 1,000 foot radius of the center of
the woodlot.

Besides the specific characteristics just mentioned,

Grazed woodlot possesses 13.9 acres of mature sugar maple,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Figure 4: Maple woodlot and surrounding communities,

beech, basswood, white ash, and American elm (Ulmus

americana). A complete list of the stand's woody species

 

can be found in Table l. The west and northwest 3.4 acres
are grazed by cattle. The grazing has produced a complete
lack of woody ground cover in that portion of the woodlot
(Fig. 6). The remaining 10.5 acres have not been grazed for
at least five years. This lack of disturbance has allowed
a tremendous number of seedlings to grow (Fig. 5). Sugar
maple comprises over 90 percent of the seedlings present.
When the leaves are out, the seedlings produce a thick,
three to four foot high, ground cover on 95 percent of the
10.5 acres. The soil type for Grazed woodlot is the same
as that for Maple, Miami loam.

The area surrounding Grazed woodlot, included in the
intensive sutdy area, is being used for various agricultural
purposes (Fig. 7). The principal foraging areas, as de-
termined by scat analysis, for raccoon are located in corn-
fields and the orchard and around the stock feeders.

In other ecological studies on raccoon (Stuewer,
1943, Cabalka, 1952, Dorney, 1954, and Stains, 1956), natural
water supplies, such as streams and lakes, were always con-
sidered a necessary part of the raccoon's habitat and, there-
fore were always included in the immediate environment being
observed. The lack of adjacent surface water distinguishes
my study area from those of the above authors. The nearest

permanent natural water is a pond 1.06 miles south-southwest

10

 

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with Cavity 13 in the foreground.

Figure 5

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Grazed portion of Grazed woodlot
with Cavity 11 in the foreground.

Figure 6

eld

Hayfield

Figure 7:

12

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Intensive study area, Grazed woodlot,
surrounding communities.

 

and

13

of Grazed woodlot. The closest permanent water is at three
metal stock tanks located about 1,500 feet northeast of

Grazed woodlot (Fig. 7).
SEASONAL CLIMATIC CONDITIONS

The climatological standard normals obtained from
the United States Weather Bureau at Lansing, Michigan were
calculated from data recorded for the years of 1931-1960.
The average yearly temperature for this 30-year period was
47.6OF., mean maximum 51.10F., and mean minimum 38.20F. The
average annual precipitation for the same period of time
was 30.62 inches.

The seasonal standard normals for the same 30 year
period were calculated per three month periods and were de-
termined as follows: Winter, January-March, had an average
temperature of 26.9OF., a mean maximum of 34.6OF., and a
mean minimum of 19.3OF. The average precipitation was 6.3
inches. The spring months of April-June had an average
temperature of 56.7OF., a mean maximum of 67.50F., and a
mean minimum of 45.9OF. The average precipitation for these
months was 9.93 inches. The summer months of July—September
had the highest average temperature which was 68.00F., mean
maximum 79.3OF., and mean minimum 56.6OF. Average rainfall
was calculated to be 8.22 inches. Fall, October-December,

had an average temperature of 38.90F., a mean maximum of

14

49.90F., a mean minimum of 30.90F., and an average precipi-

tation of 6.69 inches.
METHODS
LOCATING AND MEASURING DENS

Locating tree cavities and ground burrows used by
raccoons was-accomplished by the following means: (1) By
reviewing the data gathered in a previous study on cavities
and burrows (Gysel, 1961); (2) with the aid of binoculars;
and (5) by the use of ladders designed especially for tree
climbing.

Once a den of sufficient size (entrance four inches
or more in diameter and inner dimensions nine inches or more
in diameter) was-located, it was examined and measured. The
types of measurements and observations made are presented in
figures 8 and 9. Measurements were made with the-aid of a
six foot, flexible metal tape—measure-and a~25 foot, flexible
probe. The-probe was-used primarily to measure the depth of
the-cavities-and burrows.. A periscope device-and~a six volt
spotlight were employed to observe the-bottom in the deep
cavities. Due to the depth of some of the cavities, it was
impossible to obtain accurate measurements of the cavity
bottoms. Trees, too risky to be climbed, and deep natural

burrows were not measured.

15

Figure 8: This is an example of the cards used in
collecting data on tree cavities.

 

 

 

 

Den No.__Date Located Locality

County Township Forest type

TOpography

DEN TREE: Species Height Diameter

Distance to water: Natural Artificial Location
CAVITY: Height____Exposure____Dia. of entrance____Depth to
the nest____Inside dimensions____Nest material

 

Additional Notes: Diagram

 

Figure 9: This is an example of the cards used in
collecting data on ground burrows.

 

 

Den No.__Date Located Locality
County Township Forest type
TOpography

 

Burrow: Distance to water: Natural Artificial

Location Exposure Dia. of entrance Total Horiz.
Depth Horiz. Depth to nest Vert. Depth to nest
Inside Dimensions Nest materials

 

 

Additional Notes: Diagram

 

l6

USE DETERMINATION

The question, which tree cavities and ground burrows
were being frequented by raccoons, was answered by the use
of one or more of three methods. Direct observation of
raccoon signs or the presence of raccoons in the den was
used most often in this determination. If there were no ap-
parent signs of use, hair catchers or automatic photographic
units, placed at the entrances to the dens, were employed to

obtain this necessary information,

ANALYSIS OF MICROCLIMATES

Recording thermometers were employed to obtain the
temperature inside selected cavities and burrows° Stains
(1961), using a similar bulb—type recorder, had placed the
bulb element directly on the cavity bottom where it was
constantly being influenced by the presence of the raccoons.
In order to eliminate this problem, I suspended the bulb
element approximately 18 to 24 inches above the cavity bottom
along the cavity wall° In this study the Bararach bulb-type
Tempscribe, model SDC, was used. The daily maximum and mini—
mum temperatures were calculated from the recording charts
and compared to the external temperature readings obtained
from a weather station located approximately 1% miles due
north of Grazed woodlot. In order to determine other

aspects of the microclimates of the cavities and burrows,

17

direct observations were made periodically. These obser-
vations were made particularly after there had been precipi-

tation of any type°
ANALYSIS OF THE MACROCLIMATE

Climatic data were obtained from a weather station
located east of Baker woodlot on the Michigan State Uni—
versity campus° From the data, I was able to obtain the
minimum—maximum temperatures, amount, time, and duration of
precipitation, and cumulative wind counts from an open area,
The daily sunrise and sunset times were taken from a calcu—
lated sunrise-sunset table. Additional weather information
was obtained from my own observations and from the United

States Weather Bureau at Lansing, Michigan°
ANALYSIS OF DEN USE

In order to determine the time, amount and type of
raccoon use, the cavities and burrows were monitored with
the aid of wire-metal tube switches and an Esterline Angus
Twenty-Pen Event Recorder°

The wire-metal tube switches used to activate the
pens were modifications of the type described by Lawrence
and Sherman (1963). These were modified by using a 2-inch
piece of 3/8ths-inch—diameter c0pper tubing and a 0025 inch
stainless steel wire, 5 inches long, which passed through a

glass capillary rod 1% inches long, These switches were

18

stapled to the entrances of dens in such a position, that
any raccoon passing through the opening would complete a
circuit by bending the wire and touching it against the
tubing (Fig. 10). Some of the switches were modified even
further by making them directional (Fig. 10). This was ac—
complished by insulating the copper tubing so that the con—
tact could be made only in the desired direction. In ad—
dition to these switches, a special one was devised in order
to monitor the cavity located in the top of a rotten beech,
which was too risky to be climbed. This switch was con-
structed in such a manner that it would be activated as the
raccoon made its way up or down the tree trunk.

In determining the validity of the data obtained by
the Esterline Angus recorder, I made direct observations.
Also, automatic photographic units were sometimes used to
verify the raccoon use recorded for the ground burrows. Two
types of photographic units were utilized: One was a single
shot unit devised by Gysel and Davis (1956) and the other

was a unit with an automatic camera and strobe unit.

RECORDED USE INTERPRETATION

In interpreting the activity indicated on the re-
corder charts, I made the following assumptions: (1) Any
activity recorded between sunset and sunrise was attributed
to raccoons unless proven otherwise; (2) any activity between

sunrise and sunset was attributed to squirrels (Sciurus niger)

 

l9

 

Figure 10: Directional switches installed at the
entrance to Cavity 2.

20

unless proven to be raccoons by direct observations; (3) if
activity was recorded at a den before sunrise and again at
the same den after sunset of the same day, it was assumed
that the cavity or burrow had been used as a place of rest
by a raccoon; (4) during cold spells of several days du-
ration, the third assumption was expanded to include activity
that indicated the use of a den as a rest place by a raccoon
during the period of the low temperatures. It was assumed
that a den was used for the duration of the cold spell, if
activity was recorded before sunrise just prior to or at the
onset of the cold spell and not resumed until after sunset
and/or rising temperatures.

In summarizing the activity, two units were devised
to define the types of raccoon use. The term "rest unit"
was used for any activity that indicated that the raccoon
had used the cavity or burrow for any period of time over
three hours in duration. "Investigational unit" was used to
define any activity that was less than three hours in

duration.

MOVEMENT ANALYSIS

Several different methods were employed in obtaining
an indication of raccoon abundance and the direction and
amount of movement between the different plant communities
in the general and intensive study areas. The principal

method used in determining the relative abundance and

21

movement was live trapping and tagging. There were five
traplines in the general study area. The first trapline
consisted of 36 wire-box traps placed in a 600 by 600 foot
grid pattern, in the ungrazed section of Grazed woodlot.

The second trapline consisted of 32 traps, of which 11 were
placed along the fence 100 yards north of Grazed woodlot, 15
along the fence 100 yards east of the woodlot, and 6, 100
feet south of the woodlot. All traps were spaced at 100
foot intervals. The three remaining traplines were in Maple,
Hudson, and Toumey woodlots and all consisted of 36 traps
which were set 100 feet apart in the same grid pattern as the
one described for Grazed woodlot.

Movement from Grazed woodlot to the cornfield 100
yards east of the woodlot was monitored by five counters.
These counters were tripped by lines stretched across run-
ways under or through the fence. The counters gave only an
indication of numbers and not time or direction of movement.

The last method employed to determine general move—
ment was observation of the composition and location of scat.
The scat composition confirmed, in some instances, exactly
where the raccoon had eaten, and the location confirmed the

presence of the raccoon.

22
RESULTS
INDICATION OF THE NUMBER OF RACCOON

Intensive trapping was used to determine whether the
population was of sufficient size for the study, and the
relative numbers in the forest communities surrounding
Grazed woodlot. A total of 47 different raccoons were
captured, tagged and released during 2,500 trapnights*
(Table 2). When these figures were compared with trapping
data of previous years on the study area, there was an indi—
cation of a rise in the raccoon population.

In analyzing the raccoons handled, as to age and sex,
I found that there were 21 adults (11 males and 10 females),
and 26 juveniles (7 males and 19 females). This gave an age
ratio of 1.21 juveniles per adult and a sex ratio of 1 male
per 1.61 females. This sex ratio is quite different from the
ones obtained by Stuewer (1943), 1.08 males per female, and
Stains (1956), 1.1 males per female. If the ratio I calcu—
lated is not valid, then the only explanation for the error
would be a bias in trapping juvenile females; however, this
conclusion is not born out by the data. The ratio of re-
captures to total captures in both the female and male juve—
nile classes was 6 recaptures per 10 total captures. There-
fore, it does not appear that there is a bias in trapping of

juvenile females.

 

*A trapnight is one trap in operation for a 24 hour
period.

23

Table 2: The number of raccoons trapped in the five trap-
lines and the total trapnights for each.

 

 

' ' New Retrapped ) Total
Trapline Trapnights Raccoons Raccoons Captured
1. Grazed 940 15 33 48
2. Vicinity 304 4 10 14
3. Maple 425 2 0 2
4. Hudson 417 14 6 20
5. Toumey 414 12 2 14
Totals , 2,500 . 47 51 98

 

 

 

 

24

GENERAL MOVEMENT PATTERNS

Table 3 lists the raccoons that were retrapped in
more than one trapline. The information obtained from the
movement of the first four raccoons listed indicated that
there was substantial travel between Grazed and Hudson wood—
lot. This was expected because Hudson woodlot is less than
one-half mile from Grazed woodlot, which, according to
Stuewer's (1943), Stains' (1956), and Tester and Siniff's
(1965) estimates of one mile in diameter home range for
raccoon, placed it within the limits of the normal home
range of a raccoon.

The retrap records of the second set of four raccoons
listed in Table 3 indicated that these particular juveniles
appeared to have been summer residents of Grazed woodlot,
and the cornfield east of the woodlot was their main source
of food.

Number 681, trapped in Grazed, was found on October
30, 1964 dead on College Road 400 yards southwest of Grazed
woodlot. A possible explanation for this raccoon's being
there was that its usual food supply had been harvested and
the only other close supply of corn was the cornfields west
of Grazed woodlot.

Number 720 was found dead on February 16, 1965, with
three juvenile females, two juvenile males and one yearling

male, in a field southeast of the Hagedorn-Bennett crossroads.

25

 

 

 

 

 

Table 3: Raccoons that were captured in more than one
trapline.
Traplines
[ Tag

Age Sex No. Grazed Vicinity Maple Hudson Toume Deaths
A M 700 2R** 0*

A M 15 1R 0

J F 671 1R 0 D***
J M 693 0 2R

J F 661 0 4R

J F 665 0 3R

J M 660 0 1R

J F 669 0 1R

J F 681 0 D

J y F 720 y 0 D

 

 

 

 

 

 

 

 

 

*"0" represents the trapline

**IIR"
was recaptured.

*** "D"

of original capture.

represents the trapline in which the raccoon

notes that the raccoon was recovered dead.

26

They had been using a 14 inch drainage tile for a den but
were flooded out by an early thaw and died of drowning and
exposure.

Despite the intensive trapping, only 20 out of the
47 raccoons were ever recaptured; of the 20 recaptured, only
11 were captured more than once and only 8 more than twice.
This indicated that either trap shyness, or emigration or
immigration or mortality or any combination of these factors
must have influenced the recapture rates. The recapture
ratio of adults was noticeably different than that of juve—
niles. The juveniles had 6 recaptures to 10 total captures
ratio while the adults had a 2.4 recaptures to 10 total
captures ratio. This did indicate a trap shyness factor
among adults.

The five counters, along the fence 100 yards east of
Grazed woodlot, were in operation for the months of August
and September. In the month of August, there were 62
tallies in 30 days giving an average of 2.07 counts per day.
In September, there were 56 counts in 31 days for an average
of 1.8 per day. The possible explanation for the decrease
in the number of counts from August to September was the in-
crease in the number of additional openings in the fence.

Scat examined in Grazed woodlot, during the last
week of June 1964 and the first two weeks of July 1964, con—
tained large numbers of sour cherry pits. The only source

of sour cherries in the immediate vicinity of the woodlot

27

was the University orchard west of Maple woodlot. Upon
examination of the cherry trees, I found extensive branch
damage, particularly on the young trees.

As the corn began to ripen in mid-July, it became
increasingly more important in the scat composition analysis.
By the end of July 1964, almost 100 percent of the scat
found consisted of corn. The high percentage of corn in the
scat continued into October, by which time all the corn had
been harvested. The presence of corn in the scat indicated
that they were frequenting the cornfields but due to the
large number of accessible cornfields present, it could not
be determined with any reliability, which cornfields were
being visited by which raccoons.

Apricots were found in the scat along the fence west
of the cornfield between Grazed and Maple woodlot. This,
like the cherries, indicated a use of the orchard as a source
of food. Further examination of the orchard proved that
raccoons also were feeding on the grapes; but, no scat con—
taining grapes was found outside the boundaries of the

orchard.

DENS LOCATED

Types

Using the methods described previously, 13 raccoon

dens were located, examined, classified and measured in

28

Grazed woodlot. The tree cavities were divided into two
groups; tree trunk cavities and tree base cavities. Ten of
the 13 dens located were of the tree trunk type; the remain‘
ing consisted of two tree base cavities and one ground
burrow. In addition to the 13 natural dens located, two
artificial ground dens were constructed, when it was noted
that the only natural ground burrow had tremendous amounts

of raccoon activity.

Locations

 

The locations of the 15 dens in Grazed woodlot are
pin-pointed in Figure 11. This figure, when combined with
Figure 7, illustrates the position of each den in relation-
ship to each other and to the plant communities surrounding
the woodlot°

In attempting to relate location to differential use
of dens, I first divided the ungrazed portion of the woodlot
into four equal parts and then constructed circles from the
center of the woodlot in 65 foot intervals (Fig. 11). I
then tried to make comparisons by contrasting the activity
that had occurred at each den to the activity of the other
dens located in the same quadrant and circle interval. (For
example: comparing activity at cavities 2 and 3.) I also
tried to compare individual den activity of the different
dens in the same quadrant regardless of its circle interval

location and vice versa.

29

Location of the tree cavities and ground burrows
in Grazed woodlot.

Figure 11:

 

 

 

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y
.#8

 

    
 

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5

 

 

 

 

 

o
(
o 1 012
O Gr ound burr ows
x Tree base cavities
Tree trunk cavities «w'

The roman numeral is the circle interval location
and the letters in the corners are the quadrant initials.

30

Descriptions

A verbal description of a den's characteristics
would be of little value, due to the difficulty in making
comparisons with such a description; therefore, in order to
eliminate some of this difficulty, the descriptions were
made in the form of measurements (Tables 4, 5, and 6). In
an attempt to make better comparisons of the tree trunk
cavities certain distinguishing characteristics were used to
place the nine cavities into three groups.

The first category consisted of Cavities 2, 3, 8 and
11. Their similarities, which placed them together, were:
entrance dimensions (5-7.5 inches in diameterh entrance ex-
posure (horizontal); inner dimensions (11-15 inches in di-
ameter); and the distance to the cavity bottom from the en=
trance (56 inches plus). This group of cavities could be
classified as ones with the maximum entrance size for maxi-
mum protection. and medium to large inner dimensions and depth.

The second category consisted of Cavities 1 and 4.
The characteristics of these two cavities were very similar
to the ones just mentioned for group 1 but with one ex—
ception, the vertical entrance exposure. As pointed out
later, however, the vertical entrance exposure does truly
place them in a class by themselves.

The last group consisted of Cavities 7, 9, and 13,

and had the most similarities of the three categories.

31

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32

 

 

 

 

Table 5: Measurements taken of two tree base cavities and
the raccoon activity recorded at them.

1 _#2 3 4 5 7 8 9
Maple 15 24.0 5.0 X 3.5 NH 14.0 X 13.0 18 17 1
Beech 20 29.9 27.5 X 5.5 SH 16.5 X 10.5 25 25 0
1. Tree species 6. Inner dimensions (inches)
2. Cavity number 7. Total activity in 180
3. Tree diameter (inches) days
4. Entrance dimensions 8. Investigational activity

(inches) in 180 days
5. Direction and exposure of 9. Rest activity in 180

entrance days
Table 6: Measurements taken of the three ground burrows and

the raccoon activity recorded for each.

1 2 3 4 5 6 7 8 9 10
Natural 14 9.5 X 6.5 WH 300+ —- - —- - —- 70 66 24 42
Artifi—

cial 19 6.5 X 6.5 SH 50 24 X 14 X 10 24 14 10 4
Artifi-

cial 21 7.0 X 7.0 SH 22 24 X 14 X 10 22 12 12 0
1. Ground burrow type 6. Nest dimensions
2. Burrow number 7. Vertical depth to nest
3. Entrance dimensions 8. Total activity in 180

(inches) days
4. Direction and exposure of 9. Investigational activi-

entrance ty in 180 days
5. Horizontal depth to nest 10. Rest activity in 180

(inches) days

33

Their characteristics of entrance direction (west) and ex-
posure (horizontal), and their inner dimensions (10 inches
in diameter) were all identical. Also, all their entrance
dimensions were much longer than wide and all had very
little or no vertical depth from the entrance to the cavity
bottom (Table 4). This group could be described as having
large sized entrances causing minimum protection, poor
entrance direction (because most rain comes from westerly
directions), small cavity dimensions and no depth.

Only a few studies had information on raccoon den
measurements. Stuewer (1943) had measurements for 34 tree
trunk cavities used by raccoons. In comparing the averages
he obtained in his study, to nine measured for this study, I
found a very close comparison (Table 4).

The remaining five dens, because they could not be
compared to each other or to previously gathered data, were
described by the use of verbal descriptions as well as by
their measurements listed in Tables 5 and 6.

The natural ground burrow, Number 14, was a large
den dug by foxes. Its entrance faced west and was surrounded
by two feet of excavated dirt. The total horizontal length
of the tunnel and the distance to the chamber or Chambers
could not be measured because the distance was longer than
the 25 foot probe available. The greatest vertical depth
measured was 70 inches; however, it is very possible that it

was not the deepest portion of the burrow.

34

Tree base cavity, Number 15, was in the base of a
sugar maple. The 5 by 3.5 inch elliptical entrance opened
into a room-like cavity 14 by 13 inches in diameter and 10
inches in height. There was rotting wood material on the
floor of the cavity.

Number 20, the other tree base cavity, was located in
the base of a mature beech; its 27.5 by 5.5 inch entrance
left the bottom of the cavity exposed to the weather. The
cavity extended 50 inches upward inside the trunk beyond the
entrance on the outside.

Artificial burrows, Numbers 19 and 21, were both
constructed of a piece of rectangular metal duct 24 inches
long, 14 inches wide and 10 inches high, as the chamber, and
connected to the surface by a piece of stove pipe six to
seven inches in diameter and 26 inches or more in length
laid horizontally at a 20 to 30 degree upward angle.

The bottom of all the tree cavities, both trunk and
base, contained rotten organic material and/or sawdust. No
cavities used by raccoons had any material in them that re-

sembled the makings of a nest of any type.
Surroundings

Grazed woodlot is surrounded on the west, north and
east by pastures which were being grazed throughout the
summer and early fall by beef cattle. The grass in these

pastures was usually between four and six inches high, which

35

in most cases offered little in the way of cover for a
raccoon. An alfalfa hayfield to the south of the woodlot
offered much more cover, except when it was mowed (this oc—
curred twice during the study period). When the alfalfa
was over 12 inches high, it gave good cover to any raccoon
traveling in a southeast, south or southwest direction

(Fig. 7). The only permanent cover connected with the wood~
lot was a narrow strip of high grass along the fences
running east and west from the southeast and southwest woodw
1ot corners.

Cavity 1, located in the southwest corner on the
south boundary, was flanked to the south by the alfalfa hayw
field and to the west, north and east by woods with dense
ground cover. The description of the surroundings of Number
1 also describes the conditions existing around Cavity 2 and
8 which were also located on the south border, only east of
Cavity l.

Cavity 3 was located approximately 80 feet from the
east fence and encompassed by the same type of woody ground
cover that was present throughout the woodlot. This cavity
was located closest to the cornfield (Table 7).

Cavity 13 was located aboutifllfeet from the south
fence and was also surrounded by the three to four foot high
woody ground cover (Fig. 5). These same ground cover con-
ditions existed also around cavities 4, 6, 15 and 20, and

burrows 14, 19 and 21.

36

 

 

Table 7: Number of feet from den to important constituents
of the surrounding communities.
*1 2 3 4 5
1 5,280 1,848 1,008 2,561
2 5,280 1,848 657 2,229
3 5,515 1,155 549 2,229
4 5,445 1,555 950 2,640
6 5,636 1,500 709 2,395
7 5,285 1 745 1,040 2,723
8 5,280 1,320 478 2,145
9 5 515 1,640 1,040 2,805
11 5,940 1,815 1,203 3,052
13 5,280 1,718 904 2,561
14 5 430 1,609 923 2,723
15 5,528 1,418 715 2,475
19 5,528 1,500 826 2,640
20 5,445 1,364 631 2,320
21 5,610 1,412 631 2,400
Averages 5,466 1,563 818 2,527

 

Ul-bWNH

Distance
Distance
Distance
Distance

Den number

to
to
to
to

natural water
closest stock tank
nearest cornfield
the orchard

37

A unique set of surroundings existed around Cavity 7
and 9. These two cavities were the only ones located on the
west fence which separated the grazed from the ungrazed
portion of the woodlot (Fig. 11). The cavities were en~
compassed on three sides by the heavy woody ground cover of
the ungrazed portion and on the west by no ground cover but
by a 45 foot plus forest canOpy cover.

The only cavity located in the grazed section of the
woodlot was Number 11, It was located on the middle west
edge which was adjacent to a pasture. The only cover avail-
able was the 45 foot plus forest canopy cover to the north,
east and south of the cavity (Fig. 6).

Figure 11 combined with Figure 7 illustrates the
position of each den in relationship to each other and to
the land use communities surrounding the woodlot. The
amount of activity at a den could have been affected by its
distance to some important environmental constituent. There-
fore, in an attempt to bring out a possible indication of
such an affect, the shortest distances were measured from
the dens to particular communities or environmental condi-
tions believed to have possible importance to the welfare of
the raccoon. The results of these measurements are listed

in Table 7.

38

MICROCLIMATES

Tsing four bulb-type Tempscribes, the temperature
conditions of tree trunk cavities l, 8 and 11, and ground
burrows l4 and 19 were monitored for various lengths of
time. For the periods of time that the dens were not
monitored, due to lack of instruments or malfunctioning of
available ones, temperature averages were estimated. This
was accomplished by calculating the usual daily temperature
fluctuation inside the den and comparing it to the external
temperature fluctuation (Table 8).

Cavity 1, a large tree trunk cavity located in the
southwest corner of the woodlot, was monitored from September
2, 1964 to November 23, 1964. As shown in Graph 1A, the
maximum and minimum averages inside the cavity were always
below the corresponding external maximum and minimum
averages.

Cavity 8, described with the first group of tree
trunk cavities, was equipped with the Tempscribe removed
from Cavity 1 on November 23, 1964. It was monitored from
that date until the end of the study December 31, 1964. Due
to the lack of data, an accurate temperature pattern could
not be determined; but, from a comparison of the data avail-
able I estimated the pattern to be somewhere between that

for Number 1 and that of Number 11 (Graph 1B).

39

 

 

 

 

 

 

 

 

 

 

 

 

Table 8: The average daily temperature readings inside and
outside the dens for the six months of the study.
(Numbers in black are calculated averages from
measurements; ones in parenthesis are estimated
averages.)
* 1 2 3
External July 85.1 61.2 23.9
(Den No.
1 (69) (61.1) (8.8)
8 (75.3) (68.4) (7.3)
Internal 11 78 70.1 8.1
14 (59.6) (58.1) (1.5)
19 (60.4) (58) (214)
External Aug. 79.3 54.2 25 l
Den No.
1 (63.2) (53.1) (10)
8 (69.7) (62.3) (7.5)
Internal 11 72.4 64 8.3
14 57.6 56.1 1.5
19 (58.6) (56) (2.5)
External Sept. 73.0 49.8 23.2
Den No.
1 57 48 8.7
8 (61.4) (54.4) (7.4)
Internal 11 64.5 56.1 8.4
14 56.2 54.8 1.4
19 (57.3) (54.8) (2.4)
External Oct. 59.6 33.2 26.4
Den No.
1 41.4 31.4 11.5
8 (48.5) (40) (8.5)
Internal 11 51.2 41.7 9.5
14 45.8 44.2 1.6
19 47.1 44.3 2.8
External Nov. 52.8 31.8 21.0
93.2-39. .
1 36.2 27.1 9.0
8 (42.2) (33.9) (8.3)
Internal 11 44.9 35.6 9.3
14 42.8 41.2 1.5
19 43.8 41.1 2.5
External Dec. 33.2 18.5 14.7
“Den No.
1 (14.8) (6.7) (8.1)
8 18 11 7.4
Internal 11 23.3 14.3 8.7
14 31.1 29.4 1.3
19 25.7 24.7 1.0

 

LUMP

Average daily maximum temperature (OF).
Average daily minimum temperature (OF).

. Average difference between daily minimum and
maximum temperatures.

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41

A Tempscribe installed at Cavity 11, which was
located in the grazed portion of the woodlot, was in Oper—
ation from July 16, 1964 until December 23, 1964, at which
time the time mechanism malfunctioned. The temperature
pattern of this cavity indicated that this cavity was the
warmest and the most stable of the three cavities monitored.
The temperature pattern, in this case, instead of having the
maximum and minimum averages on either side of the external
minimum average, usually had both of them between the ex-
ternal maximum and minimum averages (Graph 1C).

Ground burrow 14 was equipped with a Tempscribe on
August 24, 1964. The Tempscribe was in operation until
September 20, 1964, at which time the clock mechanism failed.
The mechanism was repaired and the Tempscribe reinstalled on
October 7, 1964; and continued in operation until the termi-
nation of the study. The resulting temperature pattern ob-
tained was completely different from the ones of the
previously mentioned tree trunk cavities. The maximum and
minimum monthly averages were usually only one or two de—
grees apart and the total slope of the graph was very
gradual in comparison to those of the tree cavities (Graph
2A) .

The last den to be monitored was artificial ground
burrow 19. The Tempscribe was installed on October 26, 1964
and remained in operation until December 31, 1964. The

temperature pattern obtained for this den was very similar

42

Graph 2: Maximun and minimum monthly averages for ground
burrows 14 and 19 for the six months of the study.
(All temperatures are in degrees Fahrenheit.)

 

Graph 2A
0 . \\\ #14

 

 

O l I I '
ggoF “‘Jhiy Adg. sept. Odt. Ndv. Déc.
F

 

‘~ Graph 2B

Nu.

BOOF "' \\\# 1'9

 

 

10°F v

 

 

1 1 l L A

47 v . . F'
July Aug. Sept. Oct. Nov. Dec.

 

09F

*The dotted lines are the minimum and maximum averages out—
side the burrow.

**The solid lines are the minimum and maximum averages in—

side the burrow.

The heavier solid lines are the estimated minimum and

maximum averages inside the cavity.

***

43

to the one for Number 14. Its average fluctuation was
usually around three degrees, which was slightly more than
the average fluctuation for Number 14 (Graph 2B). I did not
expect the close comparison of the two patterns due to the
fact that the natural burrow was almost four feet deeper
than the artificial one.

Cavity checks, after substantial precipitation, indi_
cated that cavities l and 4 were always wet, that Number 8
was wet on occasion, depending on the storm direction, and
that cavities 7, 9 and 13 were wet whenever the storm was
from the northwest, west or southwest. These moist periods
affected the temperature by lowering it as the water
evaporated.

Table 9 shows the external weather conditions that
existed during each of the six months of the study. Also
illustrated by the table are the amount of departure from
the expected normal temperatures, and amounts of precipi-
tation taken from the averages calculated for the 30 year

period from 1931-1960.
RECORDED ACTIVITY AT DEN ENI‘RANCES

The den activity indicated by the recorder charts,
was first summarized as to date, den, time, and direction,
if possible. The daily activity and the sunrise-sunset
times were then plotted on a graph. After these had been

plotted for each of the 180 days, daily activity was

44

Table 9: Monthly macroclimatic conditions for the six
months of the study.

 

 

 

 

 

 

 

 

 

 

Temperature Precipitation Wind

Month A B c D *FA B c H”*2; B
.July 1 85.1 61.2 73.2 +1.5 3.07 1.32 +0.49 6.2 28
August . 79.3 54.2 66.8 -3.4 3.95 1.24 +0.90 9.0 45
September 73.0 49.6 61.3 -0.7 1.90 .77 -0.70 8.8 34
October 59.6 33.2 46.4 —4.9 0.65 033 -1.85 8.4 29
November 52.8 31.8 42.3 +4.4 1.92 1.07 —0.29 10.7 47
December 133.2 18.5 25.9 -1.6 1.62 .46 -0.37 11.3 32

 

 

 

 

 

 

 

Temperature (OF)

Average daily maximun
Average daily minimum
Observed daily average
Departure from the expected daily average

Precipitation (inches)

Total for the month
Most in one day
Departure from the expected monthly total

Wind (mph)

 

 

Average daily speed
Fastest recorded

45

summarized by tallying all points on an hourly and weekly
basis. In order to eliminate most squirrel activity, and
also eliminate the interpretation as to type of activity,
raccoon activity was considered only as the activity oc-
curring from one hour before sunset to one hour after sun-
rise, although some day—time raccoon activity was observed.
Also eliminated from the total activity was any activity

caused by skunks (Mephitis mephitis), opossums (Didelphis

 

marsupialis), and cottontail rabbits (Sylvilagus floridanus).

 

This activity, however, proved to be minor, which had been
expected because only one opossum and one cottontail rabbit
were trapped in Grazed woodlot. The summary of the activity
as to hourly and monthly categories is in Table 10.

Next raccoon activity was separated into two cate—
gories, investigational and rest units, and the units were
summarized as to den and month (Table 11). The total units
for each month, listed at the bottom of the table, are as
they were taken from the data sheets. These totals, however,
do not give a complete picture of the total den activity
that could have occurred. This is due to the differences in
the monthly functional day totals (Table 11). If all the
monthly functional day totals were equal to December's 435
days, and the activity was prOportional to the functional
days, the grand total activity per month would probably have
read: July, 47 instead of 33; August, 54 instead of 45;

September, 63 instead of 62; and November, 60 instead of 57.

46

Table 10: Summarized amounts of uninterpreted daily activity.

Daily Activity

 

 

 

 

Hours July Aug. Sept. Oct. Nov. Dec. Totals
PM 12- 1 2 1 l 0 3 1 8
1— 2 0 0 0 7 7 16
2- 3 1 0 0 0 5 2 8
3— 4 0 0 0 0 1 ( 6 ) 7
4- 5 2 1 o ( 2 1 ) 4 10
5— 6 4 ( 2 2 ) 1 3 9 21
6— 7 (**2) 1 1 10 3 8 25
7- 8 6 5 2 9 4 4 30
8- 9 11 5 3 3 3 0 25
9—10 7 3 6 3 0 5 24
10-11 1 4 5 8 7 7 32
MN 11—12 3 5 5 4 1 8 26
AM 12- 1 3 7 8 10 1 6 35
1- 2 4 5 6 7 2 4 28
2- 3 0 4 6 9 6 4 29
3- 4 0 5 5 4 6 1 21
4- 5 7 8 4 3 6 5 33
5— 6 ( 3 ) 3 3 7 7 3 26
6— 7 5 ( 4 1 ) 5 1 2 18
7- 8 1 3 3 ( 2 5 ) 4 18
8- 9 1 1 2 6 8 ( 6 ) 24
9-10 0 1 2 2 5 l 11
10-11 0 0 l 1 1 4 7
MD 11-12 2 2 0 4 7 5 20
Totals 65 70 66 102 93 106 502
*Subtotals 45 59 59 87 53 74 377

 

*The numbers in these categories are the totals for
raccoon activity from one hour before sunset to one hour
after sunrise for each of the six months.

* a: . , .
The parentheSis are the average sunrise and sunset
times for a month period.

47

Table 11: Summary of recorded investigational and rest
activity.

Investigational Activity

 

 

 

 

 

 

 

**Functiona1
days / den Den July Aug. Sept. Oct. Nov. Dec. Totals
174 1 2 8 8 7 O O 25
163 2 0 2 1 0 4 1 8
162 3 2 7 5 3 0 0 17
165 4 1 3 1 2 2 0 9
165 6 1 3 2 2 1 0 9
173 7 0 1 2 0 l 0 4
176 8 1 2 5 1 2 1 12
172 9 O 3 6 12 O O 21
171 11 2 2 1 2 4 3 14
177 13 0 2 2 1 3 0 8
177 14 7 5 2 5 l 4 24
156 15 4 2 6 1 l 3 17
108 19 *(x) (x) 2 3 1 1 7
109 20 (X) (X) 5 7 2 0 14
41 21 (X) (X) (X) (X) 0 4 4
2,289 Totals 20 4O 48 46 22 17 193
Rest Activity
Den July Aug. Sept. Oct. Nov. Dec. Totals
174 1 0 0 0 0 0 0 0
163 2 0 0 0 1 11 2 14
162 3 O O O O 1 2 3
165 4 2 0 0 0 0 0 2
165 6 1 0 0 1 l 0 3
173 7 0 0 l 0 0 0 1
176 8 0 1 0 O 0 3 4
172 9 O O 1 1 O O 2
171 ll 4 2 3 5 4 13 31
177 13 0 O 0 0 0 0 0
177 14 6 2 1 6 17 10 42
156 15 0 0 0 1 0 0 l
108 19 (X) (X) 0 1 1 1 3
109 20 (X) (X) 0 0 0 0 0
41 21 (X) (X) (X) (X) 0 0 0
2,289 Totals 13 5 6 16 35 31 106
Grand Totals 33 45 54 62 57 48 299
Functional
days/month 305 360 371 416 402 435 2,289

 

*The Xs in parentheses indicate that the dens were not
monitored during those months.
**A functional day is defined as one den being moni—
tored for a 24_hour period.

48
ENVIRONMENTAL FACTORS EFFECTING DEN USE
STRUCTURE AND MICROCLIMATE

The most important portion of this report is the
analysis of environmental factors effecting the use of dens
by raccoons. When the construction and the microclimates of
different dens were compared, there were indications of
differential use due to variations of these characteristics.
To show comparisons between the individual den character-
istics and use, each of the 15 dens will be discussed
individually.

Cavity 1 had the largest inner dimensions of all the
tree cavities; despite its size, it was never used as a rest
place during the 174 days it was monitored. Possible explan—
ations for the lack of rest use were indicated by the data.
First, the entrance of the cavity was pointed west and its
exposure was vertical which allowed snow and rain to enter
without much difficulty. This was born out by my obser-
vations of snow on the bottom of the cavity and much rain
running into the entrance. Secondly, in examining the micro-
climates of cavities 1 and 11, (Number 11 being the most used
tree cavity), differences were clearly demonstrated by com-
paring Graphs 1A and 1C. The average daily fluctuation of
Cavity 1 was 9.4OF while that of Number 11 was only 8.7OF
(Table 8). Also, Cavity 1 was usually 10°F colder than

Cavity ll.

49

Cavity 2, one of the three most active rest dens,
had substantial use but only during the months of October,
N0vember and December. This fact produced several questions
that had to be answered. These questions were: Why was the
cavity used mainly during these months; and why was the
principal type of use of the rest type?

Due to the lack of microclimatic information for
this cavity, any direct relationship between the character-
istics of the cavity and use by raccoon was difficult to
prove; however, by comparing the information gathered from
other cavities with the data collected for Cavity 2, I was
able to formulate some possibilities.

First, Cavity 2 had better than average depth from
entrance to the cavity bottom; average entrance dimensions,
and inner dimensions; a horizontal exposure with a lip which
aided in protecting the cavity from wind and other weather
elements (Fig. 10); a south direction entrance; and ten
inches of wood insulation. A comparison of measurements for
Cavity 2 and 11 indicated the possibility that Cavity 2 was
warmer and more stable than Number 11 (Table 4).

In re-examining the amounts and types of den use
during the months of July, August and September, at which
time Cavity 2 was used the least, it was noted that these
were the warmest of the six months. Also noticed was the
fact that the total rest units for all dens were at their

minimum during these months. This gave an indication that

50

the warmth of the cavities was uncomfortable for the raccoon.
From these observations I speculated that the reason for the
lack of use of Cavity 2 during the warm months was the un—
comfortable microclimate existing in the cavity at these
times. As to a reason for an increase of use during the
colder months, I concluded that it was affected by the
stable microclimate offered by Cavity 2 during the presence
of adverse weather conditions.

The greatest distance from the entrance to the
bottom of the cavity, 95 inches, occurred in Cavity 3. This
measurement set it apart from all the other tree cavities.
When first examined, this cavity possessed signs of extensive
animal use; however, from the data collected by the event
recorder, I determined that only about 60 percent of the
total activity occurring at Number 3 could be attributed to
raccoons. Also noted was the fact that, of the total
raccoon activity, only 1/7th was of the rest unit type,
which indicated the presence of some adverse factor or
factors in the cavity itself. There was no microclimatic
data for this cavity, so the only relationships had to be
made on the physical construction comparison.

As previously mentioned, Number 3 was the deepest of
the ten tree trunk cavities. From his observations, Stuewer
(1943) concluded that depth did not apparently have an in_
fluence on use, however, the cavities that went to the base

of the tree were usually wet. Since there was no accurate

51

data on the differential use of cavities of various depths,
I assumed, from the indications, that there was a good possi-
bility that depth did have an adverse affect on use. Of
course, there was the possibility that the depth was a
secondary factor, in that, its influence was felt through
the microclimatic conditions produced by the depth and the
wetness conditions. A northwest entrance direction probably
aided the possibility of a wetness factor since most storms
came from westerly directions. In conclusion, I speculated
that the principal affect was the microclimatic factor, but,
the affect of depth may have been the cause for the un-
favorable microclimatic conditions.

Number 4, like Number 1, had a vertical entrance
exposure. Unlike Number 1, however, Number 4 was used twice
as a resting place during the 165 days it was monitored.
Also, I noted that the rest units occurred on warm sunny
days. In analyzing the total amount of use of this cavity,
I found that the cavity was used very little in comparison
to the average amounts of use of all cavities (Table 4). I
also found that microclimatic conditions similar to the ones
for Number 1 existed in Number 4. On the same days that
snow or other forms of precipitation were noticed in Cavity
1, they were also in Number 4 and usually in greater amounts.
In fact, after an early winter thaw, Number 4 became frozen
solid from the bottom of the cavity to within ten inches of

the entrance. The data from Cavity 4 indicated that this

52

cavity afforded very little protection for the raccoon at
times when protection was needed most.

As previously mentioned, under den descriptions,
cavities 7, 9 and 13 were very similar in construction.
Despite their similarities, activity recorded varied from
very little to slightly above average use. In order to
determine possible reasons for the differential use, I ex-
amined all the characteristics and found the following
differences.

Number 7, located in an American elm 17.8 inches in
diameter, had the least use of any den in Grazed woodlot.
This cavity was the highest from the ground, 17.5 feet, and
the deepest, seven inches, of the three cavities.

Cavity 9 was used the most of the three cavities. It
was located in a basswood only nine feet from the ground.
Although it was shallower than Number 7, this cavity was
sheltered from a west wind by a large limb directly in front
of the entrance, extending from the bottom of the entrance
(Fig. 12).

The last of the trio was located in a beech. The
smooth tough bark of the tree was probably more difficult
for raccoons to climb than the two previously mentioned
trees. Also, this cavity was by far the least sheltered,
due to its large entrance and lack of depth (Fig. 5). It

was always wet from any type of precipitation.

53

From these observations I concluded the following:
Due to their large entrances and shallow depths, their micro-
climates were probably very similar to existing external
conditions. Also, their west entrance direction allowed all
types of precipitation to enter from all westerly storms.
These two observations could account for the fact that all
three cavities combined were used only three times in 522
functional days as resting places by raccoons.

Raccoon activity was recorded only five times for
Number 7. This indicated that there was some factor or
factors of the appearance of the tree which had a negative
affect on raccoons. The diameter of this tree may have
given raccoons such a clue. The diameter of Number 7 was
5.2 inches smaller than the next smallest tree diameter,
which was Number 3, and 7.3 inches smaller than the average
diameter of all the nine trees (Table 4). Also, Number 7, 3
and 13 were the only cavities, whose entrances were over ten
feet from the ground, that did not have a limb between the
ground and the cavity entrance. And of these three only
Number 3 had slightly above average use. In addition to the
unsheltered entrance and lack of depth, the two observations
just discussed could have all had a bearing on the lack of
use of Number 7.

In comparison to cavities 7 and 13, Number 9 was much
more accessible. The cavity was located only nine feet from

the ground and a limb, with a ten-inch flattened surface, was

54

 

Limb sheltering the entrance to

Cavity 9.

Figure 12:

. .1
no

-9
x;

 

Two raccoons at the entrance to

ground burrow Number 14.

Figure 13:

55

directly in front of the entrance (Fig. 12). Raccoons have
been known to use such limbs as resting places (Cabalka,
1952). The quality of accessibility could possibly explain
the reason for the above average total activity but it would
have little to do with dictating the type of use. There-
fore, I believe that the data indicate that the accessibility
factor was controlling the general activity of the cavity,
but that the construction dictated the type of use.

As mentioned before, the bark of a beech tree is be-
lieved to be difficult for a raccoon to climb (Stuewer,
1943). Number 13 was the only tree in this study to possess
this condition. If it,is difficult for a raccoon to climb a
smooth beech tree, then this factor could be an explanation
for the below average amount of total use; however, like
Number 9, I believe that it was the construction of the
cavity itself that controlled the type of use.

When first examined, Cavity 8 appeared to be ex-
tensively used by raccoons. But data from later measurements
indicated that this cavity had below average use (Table 4).
Even after an analysis of its characteristics it appeared to
be a good cavity. When the microclimates of Number 8 and
Number 11 were compared, however, the possible cause for the
lack of expected use was discovered (Graphs 1B and 1C).
Further examination of the construction of the cavity un-
covered a slit five inches long on the west side of the tree,

just four inches above the cavity-bottom. This slit allowed

56

wind and rain to enter from the west and had a definite con—
trolling effect on the microclimate in the cavity.

Number 11, the most active of the ten tree cavities,
was used extensively as a place of rest (Table 4). Due to
the large amount of use incurred by Number 11, it was used
as the primary example for comparisons. This cavity was
located in a basswood 22.6 inches in diameter. The 6 by 4.5
inch entrance was 21.2 feet above the ground and had a south
direction and horizontal exposure. The cavity extended 66
inches down inside of the trunk and was 13 by 8.5 inches in
diameter. Despite the fact that it only had 2.7 inches of
insulation, its microclimate was quite stable and warm. The
average daily fluctuation between its minimum and maximum
temperature was 8.7OF and the average daily temperature was
usually one or two degrees cooler than the external daily
average.

The natural ground burrow, Number 14, had the most
stable temperature of all the dens. Its average fluctuation
was 1.50F and its temperature never went above 600E or be-
low 250F during the five months that its temperatures were
being recorded. This cavity had the largest amount of
activity of any of the 15 dens and was used primarily as a
place of rest (Table 6). Numerous photographs were taken of
raccoons entering and leaving this burrow (Fig. 13).

Artificial burrow Number 19 was equipped with a

temperature recorder so that the microclimate of this man-made

57

den could be compared to the microclimate of the natural
ground burrow. The microclimates proved to be very similar.
The average temperature fluctuation for Number 19 was 2.3OF
as compared to the 1.50F for Number 14 (Table 8 and Graphs
2A and 2B). Despite the similarity between the two burrows'
temperatures, there was little similarity as to the amount
of use. During the 108 days the artificial burrow was
monitored, there were only 10 units of activity (Table 11).
In an attempt to determine the reasons for this difference,
I continued to observe the burrow after the termination date.
The extra observations indicated that Number 19 had poorer
drainage than Number 14. During an early winter thaw, the
burrow filled up with water and became frozen solid when the
cold weather returned.

Number 21, the second artificial burrow, due to its
identical construction, suffered the same fate as Number 19.

The last cavities to be analyzed were the two tree
base cavities, Numbers 15 and 20. Number 15 possessed the
smallest entrance dimensions of all the tree cavities. I
observed a juvenile raccoon entering this cavity on June 25,
1964 and noticed that it had a tight fit. This fact could
explain the lack of rest use recorded for this cavity; how—
ever, the total activity of 18 was almost average and the
investigational units number of 17 was above average.
Number 20 had 25 investigational units for the same period

of time which indicated that this open cavity did not possess

58

rest place qualities, but was very accessible to raccoon
investigation.

It appears that once the dimensions of a den are
sufficiently large enough to house a raccoon, the primary
factor effecting the amount and type of den use is the micro-
climate of the burrow or cavity. The microclimate factor
can be broken down into two components which seem to have
approximately equal influence; temperature and wetness. The
second one, of course, has the primary influence on days
that precipitation occurs. The other factors discussed ap-
pear to be secondary except in specific cases, such as the
smoothness of the beech bark making it difficult for raccoons
to climb a beech tree. Factors such as den construction may
be considered secondary in that they usually affect the
raccoon through the microclimate. Dimensions of a cavity,
however, do have an equal role with the microclimate during
the time when young are in the den. The size must be ade—
quate and the microclimate must be comfortable and sufficient

to supply the young with the proper protection.

SURROUNDINGS

From scat analysis I determined that the cornfields
and the University orchard were the principal sources of
food. Table 7 contains the distances from each of the dens
in Grazed woodlot to the closest cornfield and to the orchard

and also to a natural and artificial water supply.

59

Using the distances and the method of location
analysis described on page 26, I attempted to determine if
there was any relationship between use and den location in
respect to the location of the other dens in the woodlot,
and between use and a den's location in respect to certain
environmental consitituents. After I had made all the com-
parisons of the different dens in the different quadrants
and circle intervals, I could not find any positive indi-
cation that there was any relationship between the amount of
use and the location of the den in Grazed woodlot.

In analyzing the data in an attempt to answer the
question of possible differential use due to location of a
den in respect to particular environmental constituents, I
found that during the months, particularly August and
September, when food was most abundant in the cornfield and
orchard, rest use of dens was at its minimum. But even then,
Numbers 11 and 14 were used eight times as rest places. Of
the cavities closer to the cornfield and orchard than Numbers
11 and 14, only Cavity 8 was used and that was only once in
61 days. During October when most of the food was being
harvested and there was a decrease in temperature, there was
an increase in rest den use, Even then, the cavities
closest to the food supplies were not used as places of rest
(Table 11).

In attempting to determine the possible influence

that den location, in respect to its distance from water,

60

had on the use of the individual dens, I examined both the
natural water area and the stock tanks. There was evidence
of raccoon use but I never observed any raccoons that had
been tagged, around the pond or within one—half mile. Regu-
lar use of this area by raccoons inhabiting Grazed woodlot
was not expected due to its distance from the woodlot. The
stock tanks, which were much closer to the woodlot, were ex-
amined and found to be accessible to the raccoons due to a
platform which would allow a raccoon to reach the water. I
never observed any signs of raccoon use during the time of
the study, but, this was due to the destruction of possible
signs by the beef cattle using the stock tanks.

From these data, I concluded that there was no posi-
tive relationship between den use and the location of the

den in respect to the particular surroundings discussed.

TIME OF SUNRISE AND SUNSET

Raccoons are generally considered to be nocturnal
(Sharp, 1956). If this is true, then activities, particularly
around dens, should be controlled by the sunrise and sunset.
From the den use recorded by the Esterline Angus recorder,
however, I found that raccoons could be active around dens
at any hour of the day. But during July, August and September
the chances of raccoon activity during daylight hours between
two hours after sunrise and two hours before sunset were

very slight (Table 10 and Graph 3). Recorded activity

61
Cumulative uninterpreted activity per hour per month period

 

 

 

 

 

 

 

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62

around cavities, during the daylight hours, increased during
the months of October, November and December; however, the
greatest percentage of this increased activity was verified
to be caused by squirrels (Table 10 and Graph 4).

In comparing sunrise and sunset times with the in—
crease and decrease in daily raccoon activity, I found that
the time of sunset appeared to have more of a controlling ef-
fect on activity than did sunrise (Graphs 3 and 4). In
order to illustrate this more clearly, activity was plotted
against the time at which it occurred (Graph 5). Most of
the raccoon activity during the daylight hours, particularly
around 12 and 1 o'clock, was caused by raccoons sunning

themselves at the entrance to the cavity.

CL IMAT IC FACTORS

Factors effecting den use were not reported in the
literature but some information was given concerning factors
influencing movement. Stuewer (1943) stated, "it appeared
that the coming of snow, rather than temperature, was the
deciding factor which induced raccoons to cease outside
activities." He concluded saying, ”later in the winter when
snow had been on the ground for a month or more, temperature
seemed to have more influence.“ Cabalka (1952) concluded
that the principal factor was the temperature and not the

presence of snow. Stains (1956) came to the same conclusion.

63

       

 

 

 

 

 

 

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64

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Temperature

First,I graphed the average daily activity per week
periods for the 26 weeks of the study. Next, I plotted all
the average daily temperatures for the corresponding week
periods. I then compared the resulting graphs (Graph 6)o
The activity was not broken down into the two units (in-
vestigational and rest) but Vfifii plotted as a daily unit of
activityo This was to eliminate any possible bias that
might have been caused by the interpretation of the activity
as to type. A comparison of Graphs 6A and 68 indicated a
relationship of temperature to activity. From this compari—
son, I found that when the average temperature went below
350F and continued to decrease, activity likewise continued
to decrease; however, if the average temperature was below
350E but had increased over the previous week's temperature,
there was a tremendous increase in activity (Graph 6, 24th
week). The phenomenon just described was reversed when the
average temperatures were above 350Fo In other words, if
the average temperature was above 350F and had decreased
from that of the previous week, the activity was most likely
to increase and just the Opposite if the temperature in-
creased (Graph 6, 6th week)o

When closely analyzed; the complexity of this factor
was indicated in Graph 6. The change in temperature appeared

to be a controlling factor but the duration; direction and

amount of change per unit time may also have had a direct

66

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67

influence on the amount of den activity. For example, from
the third to the fourth week there was a decrease of 60F
from 79oF to 730F; however, there was also a decrease in
activity. In all appearances, this disproved the above con—
clusion; but, when the week was broken down into days I
found that during three of the seven days the average
temperature was 67oF and during the remaining four days the
average daily temperature was 78°F. When the activity was
broken down into its components, I calculated that 7/8th of
the total activity had occurred on the three days with the
67oF average daily temperature. Therefore, the above con—
clusion was not disproven.

The next step in this analysis was to determine the
relationship of temperature to the two types of den use. The
two types of use referred to are investigational and rest
units. These units were arrived at by using the assumptions
and methods of interpretation discussed on page 17. The
units were summarized on an individual and monthly basis
(Table 11). The monthly results were graphed and compared to
the average monthly temperatures (Graph 7). The sum of the
investigational and rest units varied slightly from month to
month. But, when the units were graphed separately a defi—
nite trend took form (Graph 7A). It appeared that as the
monthly average temperatures decreased from 700 to 600F, in—
vestigational units increased and rest units remained

constant at a low level (Graphs 7A and 7B). As the average

68

Graph 7: Relationship of temperature to the types of den

 

    

 

 

 

 

 

 

 

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July August September OctBber NovEmber December

Months

69

monthly temperatures continued to decrease from 6OOF to 50°F,
the investigational units decreased slightly and the rest
units increased sufficiently to keep the total den use at a
steady level (Graph 7A, October). And then, as the average
temperatures dropped below SOOF the investigational units
continued to decrease and the rest units continued to in—
crease. At approximately 4OOF rest units became the pre—
dominant type of den use. This trend continued as long as
the temperatures remained below 4OOF.

In analyzing den use further, I found that when the
total investigational units per two week periods were plotted
against the average minimum temperatures for the same corre—
sponding periods, an inverted parabolic curve resulted
(Graph 8). This curve showed that as the temperatures de—
creased to around 450F the investigational units increased.
Then, as the temperatures decreased below 45°F the investi—
gational units also decreased.

Using the same method of analysis for the rest units,
a straight line was produced (Graph 9). This meant that as
the average minimum temperature decreased the rest units in-
creased pr0portionally. Of all the points plotted only one
did not follow this trend and that value is circled in red
and was for the first two week period of the study. The
only explanation for this departure from the normal trend was
that the juvenile raccoons were still very young and there was

a necessity for shelter despite the favorable temperatures.

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Graph 8: Relationship of tempera—
ture to investigational
use.

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Total investigational units per two week periods

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Total rest units per two week periods

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Average daily minimum temperature (OF) per two week periods

65

72

When the sum of the investigational and rest units
per two week periods were plotted against the corresponding
average minimum temperatures, the curve illustrated by
Graph 10 resulted. The maximum den use was achieved when
the average minimum temperature was at 4lOF.

From this information, I have drawn the following
conclusions as to the effects of temperature on the amount
and types of den use. During the six months of the study,
temperature was directly related to the amount and type of
den use. Investigational use was the predominant type of
use until the average minimum temperature went below 40°F,
at which time rest use became dominant. As temperatures
proceeded to increase, investigational use became minimum
and rest use continued to increase until the carrying

capacity of the useable dens was reached.
Precipitation

Another climatic factor believed to effect the be-
havior of raccoon is precipitation in the form of snow
(Stuewer, 1943). However, after I had examined the data
collected during the study, I could not find any relation-
ship between the presence of snow and raccoon activity. The
possible effects of snow were masked by the low temperatures
which occurred at the times that snow was present. Since I

had more data substantiating temperature as a controlling

73

Total investigational and rest units per two week periods

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74

factor, I had to conclude that snow did not have any notice-
able influence on raccoon activity.

Precipitation, in the form of rain, has not been
considered in other studies as a factor effecting raccoon
activity. In this study, however, there was some indication
that rain did possibly effect raccoon activity. But, there
was a lack of data because: First, most of the heavy rains
occurred during the daylight hours, at which time there was
very little raccoon activity; secondly, several times the rain
ceased at approximately sunset which made it difficult to
calculate which of these two factors had the most influence;
and, lastly, on several occasions there was no activity re—
corded in Grazed woodlot for the entire day, which could
have been taken as a positive or negative indication of the
affect of the rain.

From the total picture indicated by the data, I be-
lieve that raccoons are affected by heavy rains (.10 inches
or more per hour); however, the important factors to be con—
sidered are the time at which the rain occurred, how long it

lasted and its hourly rate.

Wind

The last climatic factor to be considered was wind.
I graphed daily cumulative wind counts taken in Grazed wood—
lot at six feet from the ground and daily cumulative wind

counts obtained from the University weather station, which

75

was in an open field at two and six feet, and compared them

to the daily activity graphs. I could not find any direct
relationship which showed any indication that wind affected
raccoon activity. Wind, however, must be considered, at

least, a secondary factor due to its influence on temperature.
SUMMARY AND CONCLUSIONS

Little is known about the ecology of tree cavities
and ground burrows used by raccoons. This study was initi-
ated in order to describe the cavities and burrows used by
raccoons, to determine the amount and time of use and the micro—
climates of the cavities and burrows, and to evaluate the
relationship of environmental factors to the use of the
cavities and burrows by raccoons.

The study area, located on Michigan State University
farm prOperty, south of East Lansing, Michigan, is heavily
cultivated and is characterized by small scattered mesic
woodlots.

Field data were gathered from July 4, 1964 until
December 31, 1964. Three tree cavities and two ground
burrows were equipped with temperature recorders for varying
lengths of time in order to determine their inside temper-
atures. These temperature patterns were then used to evalu—
ate their microclimates. The natural dens located were
monitored with the aid of wire-metal tube switches and an

Esterline Angus event recorder, for a total of 180 functional

76

days. The artificial burrows l9 and 21 were monitored for
113 and 43 possible functional days respectively.

Thirteen natural dens were located, examined and
measured in Grazed woodlot; ten were tree trunk cavities,
two were tree base cavities, and one was a natural ground
burrow. Two artificial ground burrows were constructed
after it was noticed that the natural ground burrow had much
raccoon use. The average measurements of the nine tree
trunk cavities were very similar to the ones calculated by
Stuewer (1943) for 34 tree trunk cavities he examined. The
averages I obtained were: tree diameter 25.1 inches; height
to entrance 12.4 feet; entrance dimensions 12.7 by 4.98
inches; inner dimensions 14.4 by 11.9 inches; and distance
from the entrance to the cavity bottom 46 inches.

The ground burrow had the most stable temperature.
Its average daily temperature fluctuation was 1.50F. The
most stable tree trunk cavity had a average daily fluctu-
ation of 7.7OF and usually averaged 3.80F below the external
average temperature. The warmest of the tree trunk cavities
averaged 1.30F below the outside average temperature and had
an average daily fluctuation of 8.7OF.

During the 2,289 functional days, 502 units of un-
interpreted den activity were recorded. Of this figure, 377
units were attributed to raccoons. When the activity was
interpreted, I calculated that there were 193 investigational

units and 106 rest units of activity. The three dens with

77

the most investigational activity were: Cavity l with 25,
Cavity 9 with 21; and Burrow 14 with 24 units. The three
dens with the most rest use were: Cavity 2 with 14; Cavity
11 with 31; and Burrow 14 with 42 units.

Four basic environmental factors were indicated by
the data to influence the time, amount and type of den use.
These factors were: sunrise and sunset, cavity size and
microclimate, and the fluctuation of the external tempera-
ture. Sunset appeared to have more of a controlling effect
on raccoons than did sunrise. The influence exerted by
cavity size seemed to be minimized once the inner dimensions
were over 10 inches in diameter, and the entrance dimensions
over 4 inches in diameter. But, during the time the young
were in the dens the minimum size probably increased to 11—
12 inches in diameter. The data indicated that the micro-
climate was the most important controlling factor of the
cavity which, in most cases, appeared to dictate the type of
use. The general construction of the den, however, may have
had a secondary controlling effect which was felt through the
microclimate. The basic requirements of a good microclimate
appeared to be a stable temperature located near the average
daily external temperature, and a sheltered entrance which
keeps the entrance of precipitation at a minimum. The ex-
ternal temperature fluctuations appeared also to dictate the
types and amounts of den use. The average amount of daily

activity at the dens per week increased as the average daily

78

temperature per week decreased, and decreased as the tempera-
ture increased. This trend was followed so long as the
average daily temperatures were above 350F but was reversed
when the temperatures were below 350E. But, if there was an
increase in the average daily temperature per week while the
temperatures were below 350E, there was a noticeable increase
in the average daily activity per week. The predominant type
of den use at temperatures above 40°F was investigational.
Below 40°F rest use became the predominant type. The aver-
age weekly rest use, however, was limited to the dens that
could furnish the necessary microclimate needed to protect
the raccoon during existing adverse external weather condi-
tions. The carrying capacity of the dens located in Grazed
woodlot, under severe winter conditions as indicated by the

data, was 21 rest units per week.

LITERATURE CITED

Butterfield, R. 1954. Some raccoon and groundhog relation—
ship. J. Wildl. Mgt., 18(2):244—246.

Cabalka, J. L. 1952. Resting habits of raccoon in central
Iowa. M.S. thesis, Iowa State College, 1-35 pp.
(Unpublished).

Dorney, R. S. 1954. Ecology of marsh raccoon. J. Wildl.
Mgt., 18(2):211—225.

Gysel, L. W. and E. M. Davis Jr. 1956. A simple automatic
photographic unit for wildlife research. J. Wildl.
Mgt., 20(4):451-453.

. .1961. An ecological study of tree cavities and
ground burrows. J. Wildl. Mgt., 25(1):12-20.

Hamilton, W. 1943. Mammals of eastern United States. Com-
Stock Publ. Co., Inc., Ithaca, N. Y.

Lawrence, W. H. and C. A. Sherman. 1963. An electronic
traffic counter for recording burrow activity of the
mountain beaver. J. Mamm., 44(3):399-405.

Sharp, W. M. and L. H. Sharp. 1956. Nocturnal movements and
behavior of wild raccoons at a winter feeding station.
J. Mamm., 37(2):l70-177.

Stains, H. 1956. The raccoon in Kansas. Univ. Kans. Mus.
Nat. Hist. and State Biol. Surv., Misc. Publ. #10,
1-76 pp.

. 1961. Comparison of temperature inside and out-
side two tree dens used by raccoons. Ecology, 43(2):
410-413.

Stuewer, F. W. 1943. Raccoons: their habits and management
in Michigan. Ecol. Mono., 13(2):203—258.

Tester, J. R. and D. B. Siniff. 1965. Aspects of animal
movement and home range data obtained by telemetry.
Presented at the 30th N. Am. Wildl. and Nat. Res.
Conf., Washington, D. C. (Unpublished).

79

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