Final report: statewide wildlife investigations- black bear- preliminary investigations of the Ocmulgee River drainage black bear population, 1985

FINAL REPORT

State: Georgia

Project Number: W-37 Study Number: B-2

Proj ect Title: Section Title: Study Title: Period Covered: Abstract:
Introduction:

Statewide Wildlife Investigations

Black Bear

Preliminary Investigation of the Ocmulgee River Drainqse

Black Bear Population."~

~., .

July 1, 1980 -- June 30, 1985

The objectives of this study were to gather baseline data

concerning population density, sex and age structure, pro-

ductivity, mortality, movements and denning ecology of

black bears (Ursus americanus). The major emphasis was on

density and sex and age structure. Black bears were trapped

in culvert traps from 1980 to 1983. A total of 2,475 trap-

nights resulted in 22 bears being captured a total of 38

times. Trap-retrap data were analyzed by producing density estimates of 1 bear per

t3h.1reekm2(3)(1mbeethaords

per 1.2 mi 2). Sex and age data indicated an average age

for males and females of 4.8 and 6.1 years, respectively.

Recording of litter observations produced an estimate of 2

cubs per litter. This compares favorably with other studies

in the eastern United States. Tabulation and verification

of reported mortalities produced an estimate of five (5)

percent annual non-harvest mortality. Movement data from

multiple recaptures indicated average distances of 3.25 km

(2.03 mi) between captures and a range of 1.6-7.52 km (1.0-

4.7 mi). Radio telemetry was utilized to locate winter dens

of three (3) females. All three (3) dens were on the ground

and are described. limited hunting was recommended as a .

result of data gathered in this project. Hunt description

and harvest data are presented. Recommendations for future

research are discussed.

Black bears are classed as big game animals by the Georgia Department of Natural Resources (DNR). Georgia presently supports three (3) distinct black bear populations. The largest and most well known population exists in the mountains of north Georgia. Another well known population is centered around the Okefenokee Swamp in southea~tern Georgia.

Methoas:

This study deals with a third population situated around the Ocmu1gee River in central Georgia. Although this population has existed for a long time, it is relatively unknown to many residents of adjacent counties. Jenkins (1953) first reported the existance of this population and later Go11ey (1962) restated this information. Jenkins estimated the population at 40 animals. This is the only population data available concerning this particular population. This paucity of information precludes making scientific management decisions. Therefore, there was an existing need to accumulate baseline population data relative to the density, sex and age structure, productivity, mortality, den ecology and movement along the river. The accumulation of this preliminary data will provide some foundation on which to make management decisions, as well as, clarify the need for further research.
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Field studies were conducted on lands adjacent to the Ocmu1gee River in Houston and Twiggs Counties, Georgia. These lands are designated as the Oaky Woods and Ocmu1gee Wildlife Management Areas by the Georgia 2NR (Figure 1). The area encompasses approximately 205 km (79 mi 2) in the Upper Coastal Plain physiographic region. The field data collection for this study was accomplished from 1980 to 1983; however, some den location work continued in the winter of 1984. Trapping activities were conducted during a period from April to October each year. This period was selected on the basis of observed bear activity. Various trap types have been used to collect bear population data. One (1) of the more popular types is the culvert trap (Black, 1958; Carlock et a1. 1983; Erickson, 1957; Stickley, 1961 and Hamilton, 1978). Seven (7) culvert traps were mounted on boat trailers for added mobility. Cooked meat scraps were used as bait. Fresh bait was placed in the traps three (3) times per week. Trapping locations were changed approximately every two (2) weeks. Captured bears were immobilized with Serny1an (Phencyclidine hydrochloride) administered in dosages identical to that used by Carlock (1980) in north Georgia (0.7 mg/1b). Once immobilized, physical measurements were made and premolars pulled for aging. Aging was accomplished by cementum annuli techniques as described by Willey (1974). The sex of each animal was recorded for future analysis. For identification on subsequent re-captures, plastic polar bear type tags (Carl Jackson, RFD 2 Box 269, Colebrook, NH 03576) were placed in each ear. Each tag was stamped with identifying numbers. These same numbers were tatooed on the upper lip in the event both ear tags were lost.
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Fig. 1. Black bear Study area
along the Ocmulgee River in Central Georgia.

Results:

Records were maintained of all sightings of sows with cubs.
These, in conjunction with cub counts in dens, were utilized to estimate productivity. This technique has been used in past studies by Erickson and Nellor (1964) and Stickley
(1961) in Michigan and Virginia, respectively. Similar data
relative to mortality incidences were also recorded.

Females were equipped with radio transmitter collars for the

purpose of locating winter dens. Due to the low capture of

females, a one (I) year extension was granted for den

ecology work. The location of dens would not have been

possible without the transmitter collars. Other job respon-

sibilities prohibited a detailed radio tetemetry study of

bear movements. Some movement data was recorded in trap-

retrap efforts. Tr~p-retrap data was als~~used to estimate

densities.

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Trapping: From September 1980 to October 1983 a total of 2,475 trap nights were expended. Twenty-two (22) bears (17 males, 5 females) were captured a total of 38 times in trailer-mounted, culvert traps. Erickson (1957) found that .culvert traps were selective for males. This was primarily due to the larger home ranges exhibited by males enabling them to come into contact with traps more often. Hamilton
(1978) captured more males during the summer and attributed this to the extensive movement of males during the breeding season. Data recorded during this study showed approximately 55 percent of all captures occurred in the months of July and August (Figure 2). Trapping success for the entire
study period was calculated at one (1) capture per 65.1 trap-nights (Table 1). Hamilton (1978) experienced 50 trapnights per capture in the coastal plain of North Carolina. Studies from New York (Miller et al. 1973) and Michigan (Erickson,1957) averaged 40 and 41.2 trap-nights per capture, respectively. Analysis of trapping success, on a quarterly .basis, shows that during the July--August--September trapping periods, an average of 47.4 trap-nights were needed per capture (Table 1). This compares very favorably with other studies.

Table 1. Trapping Success By Quarterly Trapping Periods.

Period

TrapNights Captures

Trapping1 Success

April-May-June

866

7

July-August-September

1328

28

October-Nov ember-December

281

3

123.7
47.4 93.7

Totals:

2475

38

65.1

1. Trapping success measured in trap-nights per capture ..

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15.

10.
(fJ
...aUJ:
:::J
a.
o<t
5.

0........-.,.------......._ ........'--....a..........._ .........J..---I.--.~_





I







MAY

JUNE

JULY

AUCUST

SEPTEMBER

OCTOBER

MONTHS
Fig. 2. Distribution of captures by month during the Ocmulgee River black bear study - 1980 - 1983. -5-

During the trapping phase t Sernylan (Phencyelidine hydrochloride t Bio-Ceutic Laboratories t Inc., St. Joseph, Missouri) was used for immobilizing bears on 23 occasions. Both hand
syringes and C02 powered pistols were used to inject the
drugs. An average of 14.9 minutes were required to immo-
bilize bears for handling. Other duties precluded staying with each bear until recovery, however t recovery times were monitored on ten (10) bears and averaged 3.76 hours.

While immobilized, bears were tagged in both ears and lip

tattooed as a backup measure. In addition t physical mea-

surements recorded were total length; head length; shoulder

height; heart girth; neck circumference; front and rear pad

widths; and weight. Table 2 presents a summary of physical

measurements by age and sex.

~-

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~-

Ages were obtained on 19 of the 22 captured bears. Matson's

Commercial Microtechnique (Milltown, Montana) provided ages

from premolar analysis. The small sample size for each age

class limit the analysis of this type data. Male bears

generally weighed more than females for each age class. Un-

fortunatelytthe heaviest bear captured during this project

(198 kg; 440 lbs) recovered from the drug before a premolar

could be pulled for aging. However t in December of 1982 t 19

months later t an unmarked bear of equal weight was killed by

a truck less than one (1) mile from the trap-site of the

first bear. This road-killed bear was aged at 6.5 years.

Some researchers are skeptical of using body weight alone as the criterion of age (Spencer t 1955; Black t 1958; Erickson and Nellor 1964). Based on the data collected in this project t I would agree with them. As an example t 9.5 and 11 year old male bears weighed 125.6 kg (279 lbs) and 122 kg (271 lbs) respectively. When these are compared with a 6.5 year old
male weighing 198 kg (440 lbs)t there is reason to question the use of weight for aging.

Population Density: Black bear populations, like other
large mammal populations are difficult to census because of widespread home ranges and individual differences in behavior. Added to these intrinsic factors are biases for adequate
sample sizes t trap type, food supplies t available manpower t time, and money. Studies have utilized almost every type data collection and analyses available (Table 3). There is
no consensus as to which technique is better. For the pur-
poses of this studYt three (3) techniques of estimating population density were utilized. Table 4 presents the me-
thods and estimates resulting from each one. The range of these th~ee (3) estimates differ by only six (6) bears with a maximum standard deviation of : 18. I feel that this is a fairly close estimate of this population. An increase in
the number of captures could produce more precise estimates.

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Table 2. Average physical measurements 1 of bears captured during the Ocmulgee River Study from 1980 to 1983. Data is presented by sex and age classes.

Age

Sex

< 1 (1)2 F

1~-(2) M

Total Length 80.0 115.8

Head Length
21. 3
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29.5

Shoulder Hei ght
39.5
60.8

Heart Girth
41.3
68.3

Neck Circumference
23.8
~~.
40.8

Pad Front
6.0
9.0

Width Weight Rear
5...~_ 11. 3
7.8 41.4

2.5 (3) M 146.5 33.8 74.5 83.3

50.3

9.8 9.3 69.3

3.5 (4) M 147.0 34.3 73.5 90.8

53.3

10.0 8.5 72.0

3.5 (1) F 131. 3 31.3 60.0 77 .5

49.5

8.3 8.3 58.5

4.5 (2) M 157.8 36.5 79.8 93.3

62.5

10.8 8.8 94.1

4.5 ( 1) F 161.3 36.3 68.8 97.5

57.5

10.0 9.5 85.1

7.5 (2) M 186.3 40.0 82.5 119.0

72.8

12.3 9.8 145.8

8.5 (1) F 153.3 35.0 67.5 90.8

52.5

10.3 8.8 67.5

9.5 (1) M 170.0 39.5 87.5 112.5

67.5

12.5 10.5 125.6

11 (1) M 180.0 38.5 80.0 109.5

74.5

10.3 10.5 122.0

1. Expressed in cm. and kg.

2. Sample size.

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Table 3. Black bear population densities in the eastern United States.

State Maine New York Virginia Tennessee

Dens ity (Km2/bear)
14.4 15.8
10.1 3.75

Method Cruiseline method 5-year Harvest figures Ques ti onnai res to game wardens Radi~isotope feces tagging -~~-

Reference
Spencer, 1955
McCaffrey et al., 1976
Sti ckley, 1961
-~~.
Marcum, 1974

Table 4. Black bear population estimates as determined from trap-retrap data for this study.

Population Estimate

Densi ty (Km2/bear)

64 (! 18)

3.2

65 (! 11)

3.2

70

2.9

X66

3.1

-

a Seber (1973)

b Seber (1973)

c Edwards and Eberhardt (1967)

Methods
Lincoln Indexa Mean Peterson Indexb Geometric Model c

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Sex and Age Structure: A working knowledge of the sex and age structure of any population is necessary for biologists to make management decisions. Bear populations are no exception. The problem, however, lies in the fact that sample sizes are generally too small to make long lasting interpretations. In addition, there are many extrinsic factors affecting the data (Carlock et al. 1983). Rayborne (1976) found in Virginia that sex ratios were biased towards males when using culvert and harvest data (209:100 and 167:100 respectively). Hamilton (1978) reported a sex ratio of 250 males to 100 females in coastal plain North Carolina. He also stated that due to inherent biases, this represented a higher proportion of males than really existed. Data collected in this project indicates a sex ratio of 440 males to 100 females. The small sample size contributes to this as does the use~f culvert traps. Thi~includes both road and illegal kills. When considering only trapped bears, a ratio of 340 males to 100 females results.
The age structure of a population is becoming more and more important to wildlife biologists. This is especially true when combined with other population parameters. McIlroy (1972) found a higher proportion of older age groups from areas with the shortest history of hunting pressure. Table 5 presents the mean ages, by sex, for all bears examined during. this study. The average ages for males and females are 4.8 and 6.1 years respectively. Since this population hasn't been hunted in modern history, the age structure tends to agree with McIlroy's work. Carlock et al. (1983) reported a mean age of 3.9 and 4.9 for males and females. This data was taken from a population that has a history of hunting. Considering all available data, this Ocmulgee River population has a stable age structure and is capable of supporting an increased harvest.
Productivity: Productivity data is an important population parameter for wildlife biologists. The literature reveals studies reporting estimates of reproduction from litter sizes. Hamilton (1978) summarized reported litter sizes from eight (8) studies in the eastern United States (2.36 cubs per litter). Methods of estimating litter size are field counts, corpora lutea counts, placental scar counts and embryo counts. For this study, field counts were the only method available since no harvesting was allowed. Table 6 summarizes and compares the average number of cubs per litter for four (4) studies plus this study. Beeman (1975) found an inverse relationship existing between published population densities and litter size estimates. This being the case, the productivity of this population could be increased from two (2) cubs per litter by allowing limited hunting.
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Table 5. Mean this study from

ag1e9s80bytose1x98o3.faall

black

bears

examined

during

Year

Male

Female

Total

1980

4.8 (3)b

4.8 (3)

1981

4.3 (9)

8.5 (I)

4.7 ( 10)

1982

4.1 (12)

7.8 (3)

4.8 (I5)

1983

6.3 (9)

2.3 (2)

5.6 (11 )

Total ~*~

4.8 (33) ~*. 6.1 (6)

~ (39)

~*.

a Includes trapped, road and illegal kills

b Sample size

Table 6. Average litter size reported from the eastern United States by using field counts.

State Maine Michigan Wisconsin Tri -State Georgia

Reference Spencer (1955)
Erickson &Nellor (1964)
Drahos (1952) Carlock et ale (1983) This Study

Li tter Si ze 2.40 2.05 2.40 1.86 2.00

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Reproductive synchrony has been exhibited by other black bear populations. Erickson and Nellor (1964) attributed this to the extended relationship between sows and cubs as well as the inhibition of estrus due to nursing. One (1) of the females equipped with a radio transmitter collar in this study was located two (2) consecutive years in the den. In January 1983 she was located in the den alone and in February 1984 she had two (2) small cubs in the den~ This indicates that reproductive synchrony probably exists in this population.
Eastern black bear populations appear to reach sexual maturity at an earlier age than western populations. Collins (1973) reported placental scars in a- 3.75 year old female indicating that 2.5 year olds are c~pable of breeding in ~rth Carolina. 41ne (1) radio-equipped lemale captured in July of 1983 was aged at three (3) years old. In February of 1984 she was located in a den with three (3) cubs. Beeman (1975) attributed early sexual maturity to a longer growing season in the South rather than inferior habitat of the North. Other researchers have contributed litter size, frequency of litters and sexual maturity to habitat quality and nutrition (Rogers, 1976 and Ammons, 1974).
Mortality: A wildlife population turnover rate is directly related to both productivity and mortality rates. However, productivity data is usually easier to obtain. This is especially true of a species with very few natural predators. Few researchers have been able to enumerate and quantify nonharvest mortality in bears. Some have been able to estimate first year mortality in tagging studies (Stickley, 1961; Raybourne, 1976). Annual mortality in populations subject to hunting is usually estimated to be between 15 and 20 percent (Poelker and Hartwell, 1973; Erickson and Petrides, 1961; Carlock et al.; 1983). The objective of this study was to obtain some range of non-harvest mortality. Throughout this study reports were received from informants about illegally harvested bears. However, only four (4) road kills and two (2) illegally harvested animals were verified. Three (3) per year would represent approximately five (5) percent annual non-harvest mortality.
Movement: Most studies designed to monitor bear movements in detail do so through the .use of radio telemetry. Detailed telemetry studies require far to much time for Department personnel. The efforts in this project were directed more toward density, sex and age structure and productivity. Some movement data can be gleaned from trap-retrap data. Many of the multiple recaptures were made at the same trap location. However, recaptures at different locations averaged 3.25 km (2.03 mi) apart. The range was 1.6-7.52 km (1.0-4.7 mi). These distances may represent above average movements due to large percentage of captives coinciding with the reproductive season.
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Di scuss ion:

Den Ecology: Den selection by bears can be a very important habitat quality. Research has indicated varying types of dens utilized by bears. Carlock et al. (1983) reported a preference toward hollow tree dens with reference to ground dens. Hamilton (1978) found ground dens most important in the coastal plain of North Carolina.
lands represented by this study are under intense forest management for pulp production. Consequently, very few hollow trees are available for denning. To facilitate the location of bear dens, radio collars were placed on females. Three dens were located and recorded. In all three cases, the dens were on the ground. Two were under fallen tree tops. The other den was located in a windrow of logging slash. This was a depression in the windrow covereg""py a thic~-~anopy of japanese honeysuckle (Lonicera japonlca) supported by a 30 cm (12 inches) log which ran parallel to the windrow. These dens are similar to those reported to Department personnel by hunters on the wil d1 i fe management areas.
Estimating the density of bear populations can be a difficult task. Trap-retrap data often contains built in biases which can lead to varying estimates of density. In this study, three (3) methods of estimating density produced almost identical estimates. Carlock et al. (1983) reported that the Great Smokey Mountains National Park supported a high density of one (1) bear per 2.6 km2 (approximately 1 bear per mi 2). Data collected during this study estimates density at one (1) bear per 3.1 km2 (1 bear per 1.2 mi 2). One of the major objectives of this study was to collect baseline data to support management decisions. With bear hunting becoming more and more popular in the North and South Georgia populations, it was inevitable that hunters would request a season on this Central population as well. After the completion of three (3) years of field work, it was felt that enough information was gathered to support a recommendation for limited hunting. Therefore in December of 1984, the first bear hunts in central Georgia in recent history were allowed on these two (2) wildlife management areas. The harvest was one (1) female on the Oaky Woods WMA and one (1) male on the Ocmulgee WMA. The recommendation was supported by a high density estimate, a relatively older age structure (average age of 5.0 years), a good productivity rate (2.0 cubs per litter) and low nonharvest mortality rate (5 percent). The hunt was a one (1) day still hunt in mid December. No dogs or bait were allowed. Georgia law prohibits the harvest of cubs (less than 33.8 kg (75 lbs) or sows with cubs. Limited hunting will be allowed until such time as it begins to affect this bear population.
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In general, this project accomplished the original objectives. It does not answer all the questions we have about this population. The more information that is obtained, the better the decisions made by managers will be. There needs to be some detailed investigations into the movement, food habits, denning and productivity aspects of this population. These types of projects are best suited to graduate students rather than DNR personnel. I strongly encourage DNR to work with the various universities to find student personnel to conduct these research projects. I will continue to collect and verify mortality data and all types of data from harvested bears. This will not answer the habitat related questions and these are vital in this area.
Daniel K. Grahl, Jr. Wildlife Biologist Principle Investigator
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Li terature Cited
Ammons, A. E. 1974. Observation on reproductive activity of black bears in captivity in North Carolina. In Proc. Second Eastern Workshop on Black Bear Manage. and Res. Univ. Tennessee, Knoxville. pp 98-100.
Beeman, L. E. 1975. Population characteristics, movements and activities of the black bear (Ursus americanus) in the Great Smokey Mountains National Park. Ph.D. Dissertation, Univ. of Tennessee, Knoxville. 218 pp.
Black, H. E. 1958. Black bear research in New York. Trans. N. Am. Wildl. Conf. 23:433-461.
Carlock, ~~- M. 1980. Personal communication. Carlock, D. M., R. H. Conley, J. M. Collins, P. E. Hale, K. ,G. Johnson,
A. S. Johnson and M. R. Pelton, 1983. The Tri-State Black Bear . Study. Tech. Rep. No. 83-9. Tennessee Wildl. Res. Agency, Nashville,
TN. 286 pp. Collins, J. M. 1973. Some aspects of reproduction and age structure in black
b~ar in North Carolina. Proc. Southeastern Assoc. Fish Game Commissioners Conf. 27:163-170. Drahos, N. 1952. Notes on bears. New York State Conserve 7(2):14-18.
Edwards, W. R. and L. L. Eberhardt, 1967. Estimating cottontail abundance
from live trapping data. J. Wildl. Manage. 33:87-96. Erickson, A. W. 1957. Techniques for live-trapping and handling Black Bears.
Trans. N. Am. Wildl. Conf. 22:520-543. Erickson, A. W. and J. E. Nellor, 1964. The black bear in Michigan. Michigan
State University Res. Bull. 4. 102 pp. Erickson, A. W. and G. A. Petrides, 1964. Population structure, movements and
mortality of tagged black bears in Michigan. Pages 46-67, Part 2, In A. W. Erickson, J. Nellor, and G. A. Petrides. The black bear in Michigan. Michigan State Agric. Exp. Stn. Res. Bull. 4. 102 pp. Golley" F. B. 1962. Mammals of Georgia--A study of their distribution and functional role in the ecosystem. Univ. of Georgia Press, Athens. 218 pp. Hamilton, R. J. 1978. Ecology of the black bear in southeastern North Carolina. M. S. Thesis. The Univ. of Georgia, Athens. 214 pp. Jenkins, J. H. 1953. The game resources of Georgia. Ga. Game and Fish Commission, Atlanta. 114 pp.

Marcum, L. C. 1974. An evaluation of radioactive feces-tagging as a technique for determining population densities of the black bear in the Great Smokey Mountains National Park, M.S. Thesis. Univ. of Tennessee, Knoxville. 95 pp.

McCaffrey, E. R., G. B. Will, and 'A. S. Bergstrom. 1976. Preliminary management implications of black bears, Urus americanus, in the Catskill region of New York State as a result of an ecological survey. Pages 235-245 In M. R. Pelton, J. W. Lentfer, and G. E. Folks, eds. Bears-their biOTogy and management. IUCN New Sur. Pub1. 40. Morges, Switzerland.

McIlroy, C. W. 1972. Effects of hunting on black bears in Prince William

Sound. J. Wildl. Manage. 36:828-837.

Mill er,

R.

-='
L.';"E.

R.

McCaffrey,

andG-=..,,. B.

Will.

1973.

Recent capture and

handling techniques for black bears in New York. Trans. Northeast

Fish Wi1dl. Conf. 30:117-137.

Poe1ker, R. J., and Hartwell, H. D. 1973. Black bear of Washington. Washington State Game Dept. Bio1. Bull. 14. 180 pp.

Raybourne, J. W. 1976. A study of black bear populations in Virginia. Trans.
Northeasterp Fish &Wild1. Conf. 33:71-81.

Rogers, L. L. 1976. Effects of mast and berry crop failures on survival, growth, and reproductive success of black bears. Trans. N. Am. Wildl. Nat. Resour. Conf. 41:43l-437.

Seber, G. A. F. 1973. The estimation of animal abundance. Griffin, London. 506 pp.

Spencer, H. E. 1955. The black bear and its status in Maine. Maine Dep. Inland Fish and Game, Game Div. Bull. 4. Augusta. 55 pp.

Stickley, A. R., Jr. 1961. A black bear tagging study in Virginia. Proc. Southeastern Assoc. Game and Fish Commissioners Conf. 15:43-54.

Willey, C. H. 1974. Aging black bears from first premolar tooth sections. J. Wildl. Manage. 38(1):97-100.

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