Homing Tendencies of
Translocated Nuisance Black Bears in Northern Wisconsin
From Graduate Thesis work by Jack Massopust, 1985
Wildlife agencies frequently translocate bears that have behavior patterns that conflict with people. Reported results of this practice vary. This study, conducted in early 1980�s through UWSP found the following results.
From 1982-1983, researchers used radio telemetry to study 19 �nuisance� black bears in six northern Wisconsin counties. Nuisance bears were those identified as animals who were habitual offenders of garbage feeding, apiary (bee keeping operations) damage, livestock injury, property damage, or �general nuisance�.
Bears were trapped in culvert traps and immobilized by a veterinarian. Researchers determined the sex and age of the bear, weighed and measured the animals, then fitted the bears with radio collars and ear tags in order to track their movements and record data. The bears were then moved to Federal, state, or county land within the study area.
The bears were moved an average distance of approximately 41 miles from the location where they were in conflict with human activities. Most of the bears eventually returned to the original area (their �home range�) and 3 of the bears returned to the specific location where they were causing damage. A yearling male was the only bear that established a new home range in the vicinity of the new site where it was released.
This research also looked at studies done in other parts of the United States. Studies in Montana showed that moving bears less than 60 km (about 37 miles) resulted in little success. In Pennsylvania, moving bears more than 64 km (about 40 miles) reduced the likelihood of their returning to original site. In Wisconsin bears that were moved an average of 65 km (about 40 miles) returned to their home range. One bear returned after being moved nearly 50 miles away, and another at over 70 miles away. Young bears did not return to the capture area.
The Wisconsin study showed that translocating nuisance bears is only a temporary solution to the problem, since the bears often returned to their home range. Recommendations from the study included moving nuisance bears no further than about 5 miles from the trap site. It was suggested that this distance is far enough to discourage the bears from returning to the specific site where they conflict with people or cause damage, yet keeps them in their home range where they would likely return to anyway. Moving bears a shorter distance would also save transportation costs, reduce stress on the animals and allow them to remain in their home range where they can fully use resources available to them because they are familiar with it.
Other recommendations from the study included creating educational programs for landowners and the public, to include information on behavior and natural history of black bears, electric fence designs for farmers with livestock, methods of garbage storage, and how to behave when confronted by a bear.
Here are some other interesting facts from the study:
as she neared home and her activity
became mostly nocturnal.
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Response of Black Bears to Being
Chased by Hunting Dogs
From Graduate Thesis work by Jack Massopust, 1985
This research was conducted in the summers of 1981 and 1982 during the approved dog training period for those who choose to hunt black bear using dogs.
There is considerable controversy concerning the use of dogs to hunt bears. Some people believe it is inhumane to the bear, some say dogs give hunters an unfair advantage, while others express concern for the safety of the dogs.
Five radio collared bears were involved in this study. The bears were located in their dens during the previous March, and were examined to make sure they were in good physical condition before being chosen for the study. All of the bears chosen had denned in their home range and were without injury.
When the dog training period arrived, the bears� general locations were determined and hunting dogs were released in the area. Dogs used for bear hunting will track the bears� scent and can lead a hunter to the location of the bear. Bears will sometimes climb a tree in an effort to elude the dogs. In this study, none of the five bears was treed by the dogs.
This research showed the bears used zigzag patterns, circles, and backtracking in swamps to elude the dogs. The bears successfully outdistanced the dogs by using bursts of speed in combination with directional changes. The controlled "chase" of each bear ended when the dogs either lost the scent or became tired, requiring the dog handlers to prevent them from continuing the chase.
Monitoring the bears following these chases showed that most bears remained in their home range after the chase. The bears showed no long-term behavioral or physical changes as a result of the chase.
Definitions of some important terms:
An animal's
HOME RANGE is defined as the area traversed during
its normal activities of food gathering, mating and caring for young.
TRANSLOCATE means to move from one place to another.
Wildlife biologists translocate animals like nuisance bears. They also translocate animals to help establish new populations in other areas.
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A Demographic Comparison of a
Hunted and an Unhunted Population of Black Bears in Northern Wisconsin
From Graduate Thesis work by Kieran Fleming, February 1997
Population dynamics is the change in the number of
organisms in a given area plus the factors that influence those changes. This
study sought to determine differences in population dynamics of hunted and
unhunted bears. It also looked at environmental factors that influence the two
groups of bears.
133 bears were captured, marked, and followed from 1984-1994. The unhunted
population was a group of bears studied on Stockton Island, Lake Superior near
the Bayfield peninsula. The hunted bears were studied on the mainland about 40
miles south of Stockton, near Mellen, WI in an area that had similar habitat
to the island.
The unhunted bears grew to a density of nearly 2 bears per square mile, then began to decline. (The hunted population was less than one bear per square mile in 1990 and 1992). The unhunted bears had smaller home ranges and were not as heavy as mainland bears. Females on the island first bred almost a year later than bears on the mainland. Yearlings in the unhunted population had the lowest rate of survival. Cannibalism is suspected in many of these cases. The reduced fitness of the bears on Stockton Island indicates they are vulnerable to high mortality if food production fails.
In cases of cannibalism, strong evidence showed the radio-collared victim was pursued, killed and eaten by another bear. In these cases, broken branches and claw marks on trees indicated the victim was pulled out of the tree alive. Bear scat containing bear hair, claws, and bone indicated the carcass was consumed by a bear. It is likely that social constraints played a role in these incidences of cannibalism. Because of the high density of bears on the island, competition for food and space to rear young may have influenced these incidences. Cannibalism may occur more often when the number of bears grows beyond the carrying capacity (the number of individuals in a population that the resources of a habitat can support).
This study suggests that research on less dense populations of bears should try to determine if maintaining a lower density of bears through hunting will increase the fitness of the bears and reduce population fluctuations. The research data shows the number of bears harvested in northern Wisconsin at that time allowed for a sustainable population of bears that did not decrease. Using this data to help set harvest quotas will maintain populations at a healthy level where bears won't begin to suffer the stresses of high population density as seen on Stockton Island.
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Black Bear Reproductive Biology,
Denning Biology, Habitat Use, and Movements in Northern Wisconsin
From Graduate Thesis work by Gregory Kessler, 1994
Reproduction and Denning
From 1981-1988 all known bear dens in north central Wisconsin were visited to document litter size and den characteristics. This study found that litter sizes and survival rates were the highest found in any study to date. Other research showed that small litter sizes may be due to less available food, lower nutrition, harsher climates, and denser populations. This research didn�t show a correlation between food supply and litter size. High survival rates of cubs in Wisconsin indicate that bears are not stressed by competition from other bears, and that high nutrition is available.
Physical measurements were taken on 247 bears. Body temperatures as low as 21.92 C were recorded, whereas previous researchers felt 32 C was the lowest tolerable body temperature. Heart rates were as low as 13 beats per minute while dormant in the den and as high as 70 beats per minute during breeding season. The mean heart rate was about 34 beats per minute and was similar for all ages of bears. Body temperature for active bears was about 100 F compared to denned bears at about 90 F.
Litter size increased with age of female: age 3-4, 2 cubs; age 5-7, 2.67 cubs; age 8-10, 3.44, age 10+, 3 cubs. Litters with 1-3 cubs had 100% survival while 4 cub litters had 83% survival. Survival of male cubs was a little higher than females. Cubs weighed 8 � 18 lbs for males and about 5.5 � 16 lbs for females at 6 weeks of age. At 1 year old, males were about 69 lbs and females about 59.5 pounds.
Date of den entry was studied for 25 bears from 1981-88. The mean date ranged from September 18 to October 16. In years where food was abundant, bears denned an average of 12 days later. Males entered the den 12 days later than females. During a poor mast year, one female denned on August 26. The latest date of entry was Nov 1st by 2 adult males. Food and weather interact to determine when bears will enter their dens for the winter. Female bears in this study entered their dens in late September/early October. Males denned up later in October. In years when food supply was scarce, bears entered the den earlier. All bears emerged from their dens by April 1 in 1988.
Bears in various geographic areas may have a biological clock which is set my local climate and phenology of foods. Most bears appear to haven chosen den site prior to denning because they moved directly from their initial inactive locations to the den site and spent little time preparing the site. Bears became inactive 1-10 days before entering. Bears were usually away from the den site when activity slowed, and stayed at the den site once construction began. Dens did not appear to be placed near home range boundaries.
Most bears in this study did not dig a den. They chose non-excavated dens created by windfalls, logging, or standing trees. Occasionally, bears hibernated in completely open �nests� in grassy areas. Only 1 bear denned in a hollow tree compared to 50% of dens in hollow trees in a Tennessee study. This is probably because Wisconsin has few trees large enough to provide a cavity for an adult bear. The Tennessee study area had 39% virgin forest while the Wisconsin study area had 1% virgin forest remaining. Wisconsin bears didn�t excavate dens as often as seen in colder climates, probably because of less severe weather conditions.
Bear dens had no evidence of urination, defecation, eating or drinking by dormant bears. Some bears in this study did leave the den during warming trends but traveled less than 110 yards from the den. Bears metabolize stored fat to gain energy and water while dormant.
This study showed that the timing of the Wisconsin bear hunting seasons protects breeding females since most are inactive when the season begins.
Habitat Use and Movements
From May 1986 to October 1988, locations were for 14 bears were determined. Bears were significantly more active during breeding and foraging seasons than during pre-breeding and denning. Wind speed, cloud cover, and precipitation did not alter activity levels of bears. Subadults showed greater rates of movement than adult females, whether or not females had cubs. Bears traveled away from the wind as often as they traveled into it.
The annual home range size was a little more than 7 sq miles. Bears 3-6 years old used the largest home range -- more than 11.5 sq miles. Females with cubs had smaller home ranges than females without.
Bears moved at a rate of .3-.7 miles per hour while foraging. The fastest travel was nearly 2 miles per hour. Rate of movement at night was faster with increased moonlight. Bears were crepuscular (active at dawn and dusk) during the pre-breeding season, diurnal (active during the day) during breeding and foraging, and nocturnal (active at night) during fall denning period. When bears moved more at night, they moved less during the day. Bears bedded between 11 pm and 4 am during the breeding season while in all other seasons bears became inactive earlier and remained inactive later.
Adult females broke up with their offspring and the yearlings dispersed between mid May and mid June. Average dispersal distance of yearling and 2 years olds was about 22.5 miles.
This study found that aspen habitat was the most important for bears of all ages in all seasons. Oak, alder, swamp conifer, northern hardwoods, and swamp hardwoods were also used by bears for food and cover. Bear favored aspen habitat 3 times more than other habitat, possibly because this habitat has the largest number of mast producing shrub species and highest density of shrubs compared to the other forest types in this study.
Bears used aspen forest less frequently during the denning period, possibly because of increased use by humans when archery and grouse hunting opens in mid September and leaf fall increases visibility. Most black cherries, juneberries, choke cherries, and hazelnuts were consumed by that time.
Bears used red oaks in spring and fall when acorns were available. In years of high acorn production when acorns were still available the following spring bear used them shortly after den emergence. Wisconsin black bears did not use jack pine areas. Brushy openings were used by subadults. This was likely due to abundance of mast but lack of sufficient cover for wary adults.
Home range sizes may be an indicator of bear density (small home range � high population density; large home range, low bear density.) Larger home ranges of younger bears may be due to inexperience and lack of ability to compete with larger, older bears.
Younger bears used lower quality food habitat probably because of competitive exclusion by older bears, or voluntary avoidance.
Management implications
Population monitoring is difficult. Population estimates should consider annual changes in the number of male and female bears harvested, weather data and mast surveys. The study suggests mast surveys would help improve management and assessment abilities for many other wildlife species too.
Bears used agricultural land primarily for corn in this study. Damage claims to corn fields have been on the rise since 1939, probably due to increase shift from silage variety corn to early maturing grain corns. This study suggested greater use of abatement techniques where crop damage occurs. The use of propane cannons in small fields and orchards might discourage bears from entering these areas. Electric fence should continue to be primary way of protecting beehives. The author also noted that an increased effort to educate public using pamphlets on abatement techniques would be useful.
Maintenance of aspen forest appears to be important for bear habitat. This tends to be best accomplished with clearcutting since aspen will easily regenerate. Clearcutting practices in Wisconsin are a viable conservation practice in areas that are not prone to erosion. Oak management is also important but we need reliable and cost effective methods of maintaining and establishing these trees. Pine plantations are not good bear habitat. Changes in forestry practices to increase tree size, provide den trees and limit new access roads would improve bear habitat. Private land owners who wish to manage for bear habitat may qualify for financial help through the Conservation Reserve Program, Forestry Incentives Program, and Stewardship Incentives Programs. Food plots could help lure bears away from agricultural crops.
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Black Bear Population Dynamics,
Home Range, and Habitat Use on an Island in Lake Superior
From Graduate Thesis work by David Trauba, 1996
Little is known about how social interactions among bears regulate their populations. Because most bear studies are of hunted populations, it is difficult to determine if reproduction and mortality rates change when bear populations reach carrying capacity. The purpose of this study was to determine population dynamics for bears that have not been hunted. From 1984 to 1992, 27 bears on Stockton Island in Lake Superior were collared and studied.
In 1984, there were three bears living on the 15.7 square mile island. By 1990, the population had grown to 20 bears, not counting cubs, making the population density more than one bear per square mile, among the highest reported in the literature for North America. Bear density on the mainland was reported as .65 bears per square mile. In 1992, the Stockton Island population declined from cannibalism and other effects of a high population density were seen. Five cases of cannibalism and one starvation were documented.
High density of females may force bears to compete for territory and food. Although this didn�t seem to affect litter sizes or the weight of females when they entered their dens, females on the island were found to first breed at a later age than bears on the mainland. The age of primiparity for Stockton Island bears was five years, compared to three to four years old for mainland bears.
Older age of primiparity may be due to social constraints. In 1988, two bears shared about 45% of their home range with each other and seven other bears overlapped these areas. In 1989 one of these bears shifted her home range nearly a mile west, possibly in response to social pressure. This shift provided the remaining bear with about 143 acres of exclusive territory. Both bears produced cubs the following year, probably as a result of reduced social pressure in their home range.
In 1991 only one of five females had cubs and only one of her four cubs survived. Body condition was likely the explanation since the litter was extremely lightweight ranging from 2.2 lbs to less than 4 lbs. Lighter cubs tend to experience greater mortality than heavier cubs. Starvation was hypothesized to be the main cause of cub death.
Yearling (1-2 year old bears) survival was among the lowest documented. Other studies show 73-94% of yearlings survived the second full year of life. Only 60% of yearlings on Stockton Island survived. Food distribution was likely the cause. Although mast production was rated as good to very abundant, these food sources were often clumped in small areas, causing social pressure if more than one bear at a time was in the area. This study showed that yearling weights declined as density increased.
Social interactions with adult males may exclude females from preferred habitats. If so, high density of males could result in decreased reproduction because females would be excluded from food resources. Some studies have suggested it is possible that males and females choose different habitat types.
Beaver flowages covered only 3% of the 254 acre island, but were preferred habitat for adults of both sexes in this study. The flowages provided the largest diversity of food. Clumps of raspberry and blackberry were frequent along the edge of flowages. Beaked hazel was the dominant shrub. Bears were major predators of beaver on the island and were responsible for the beaver population demise. 18 of 26 beaver lodges were dug into by bears, with most lodges excavated to the nest chamber.
Home ranges of adult males extensively overlapped. Females had more distinct home ranges with less overlap. Where home range overlapped, females used the shared areas more than the unshared, though not at the same time. Shared areas were centered around beaver flowages, a most selected cover type. As bear density increased, female home range size decreased. The home range size of one of the original three bears present in 1984 decreased by 67% as the population grew.
When females were located simultaneously through radio telemetry, their distance apart was 132 yards � 2.3 miles. On only two of 110 occasions were females within less than 200 yards apart. Overlap of home range in other studies has varied. Female overlap at Stockton appeared to be related to the distribution of food clumps along beaver flowages. The clumped distribution of food sources may heighten competition among bears.
Home ranges on Stockton Island were smaller than other estimates in North America. Bears may have been physically confined by the size of the island, but bears are good swimmers so it�s unlikely that they were confined by the water surrounding the island. No resident bears permanently dispersed. Dispersal is usually at two years old for males. Females are normally accepted into the resident population. Other studies suggested that adult males cause juveniles to disperse. This study concluded that adult male aggressions don�t affect dispersal; adults disperse to reduce resource and mate competition.
Reduced resource competition on the island would account for lack of dispersal since there was only one adult male bear on the island up until 1989. After 1989 there were five to eight adult males. It was expected that these bears would disperse since all potential mating ranges were occupied and resource competition was becoming evident (delayed breeding and cannibalism.) Of the five, two bears dropped their collars so dispersal couldn�t be determined. The other potential dispersers were killed by another bear or bears as yearlings, so the affects of increasing density on dispersal couldn�t be determined.
Three subadult (2-3 years old) males immigrated to the island but did stay. All had home ranges which included other islands and each denned on other islands. Resident bears did not permanently leave the island. Three males left for short periods visiting the mainland and other islands, but returned.
This study suggests social interactions and intraspecific killings may be regulating the population. It also suggests that density influences home range size.
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Black Bear Activity, Home Range,
Spring and Summer Habitat Use, and Food Habits in Northern Wisconsin
From Graduate Thesis work by Scott Storlid, 1995
Ninety six percent of the forested land in northern Wisconsin is managed for timber. This large and relatively contiguous area provide black bears with diverse and productive habitat with cover types containing an abundance of nutritious foods.
Home range
Sows without cubs had a larger home range than sows with cubs, and their home ranges overlapped moderately with an average of about 25% of their territory being shared. Sows avoided each other by using shared areas at different times. Sows were within 275 yards or less of another sow on only four occasions. Three of these encounters involved an eight year old bear and her 2 year old daughter. These bears had extensive overlap in their home ranges, and denned together in the fall after breaking up the previous spring. The fourth interaction was between three females at a dump. Two of the bears were about 165 yards apart when a third bear approached. The two bears moved away, maintaining the distance of separation. This instance may illustrate mutual avoidance, but is complicated by the presence of an artificial food source. Territoriality was not observed in this study, probably because of the abundance of bear foods in the area.
Sows with cubs or yearling have smaller home ranges and use food resources intensively within that range. Boars cover more area and move greater distances between foraging sites rather than intensively use a small area. When boars were present on the study area, they passed through quickly, which implies possible avoidance of sows.
Bears that move outside their home range to forage become more vulnerable to aggressive encounters with other bears, hunting pressure, and automobile mortality. One bear and her three cubs in this study moved more than 4 miles outside her home range to feed in agricultural areas. One of the cubs did not return with the family unit to the home range and was assumed to have died.
Sows in the area produced cubs about every other year. 67% survived to be yearlings. The survival rate reported in this study does not seem representative of cub survival in the state. The author notes this may be because only nine cubs were observed in the study area. A larger sample size of 18 bears in a previous study reported more than 94% survival for the same region in Wisconsin. All cubs lost in this study were from first litters, indicating that age of the sow may be factor in low survival rates.
Cubs weighed an average of 5 lbs for males and 4.4 lbs for females at birth. Yearling weights were around 50 lbs for males and females.
Food habits
Black bears are considered to be omnivorous and primarily herbivorous. Black bears have been reported to kill adult elk and white-tailed deer. They have also been reported to kill newborn fawns, and to be significant predators of newborn moose and elk. Unpublished data for northern Wisconsin suggests that black bears and deer fawns may use similar habitat types during spring and summer when fawns are most vulnerable.
Field work was conducted between May 1989 and March 1991. This study agreed with an earlier UWSP study showing that bears were generally active during the day and at dusk and dawn. Sows with cubs were less active than other bears during the pre-breeding season. This is likely because cubs are still small at that time and unable to make extensive daily movements. Activity level increased for all sows from the pre-breeding to the foraging season. Sows with cubs showed the highest level of activity for all bears during the foraging season.
Bear scat was analyzed for content to determine what bears were eating. Grasses and sedges were most common and appeared to be the most important food during the prebreeding season. Bears also ate ants, aspen leaves and catkins during this time. White-tailed deer fawn remains were also found in bear scat.
Grasses and sedges remained important foods during the breeding season, but other foods became important as they became available. Soft mast including serviceberry, wild sarsaparilla, blackberry, raspberry and insects were found in scat during this season. Fawn remains were found in about 13% of the scats during breeding season. Other important foods included wasps, domestic corn, and sunflower seeds.
During foraging, grasses and sedges became only a small part of bear diet. Soft mast, ants and wasps were the most common food items. Other important foods included apple, black cherry, and pin cherry.
Garbage from dumps and residences was observed in all scats but didn�t appear to be an important food source. Bears had access to agricultural crops but they were not heavily used. The corn and sunflower seeds found in scats were from several residents in the study area where people were feeding wildlife. With the exception of one sow who fed at the same residence almost nightly, bears did not rely on these food sources. This indicates that natural foods were adequately available.
Habitat use
Sows in this study used lowland hardwoods during all seasons and preferred aspen/hardwoods during the breeding season. Boars avoided aspen/hardwoods during the prebreeding season but preferred this habitat during breeding. This study showed the first evidence of extensive use of lowland hardwoods by black bears in Wisconsin.
Lowland hardwoods were the first cover type to green up in spring, and had a high percentage of nutritious bear foods. Bears appeared to favor cover types that were moderately dense, or thick, and limited horizontal visibility but didn�t impede bear movement. Cover types used by bears most often in this study had a relatively open canopy. Because of this these areas had a well developed shrub layer and produced an abundance of shade-intolerant food like cherries, raspberries, and beaked hazel.
Bears did not use open cover types even when they contained an abundance of food. Other studies have shown aspen to be an important habitat type. Bears in this study did not select aspen forests, possibly because it made up less than 3% of the study area. The author suggests that habitat use may vary from year to year because of variation in productivity of important bear foods.
This study recommends the following criteria be used to determine habitat quality: home range size, successful cub production, lack of foraging movements, and infrequent use of garbage and crops.
Hunting mortality
Seventeen bears were captured, radio-collared and monitored during 1989. Of the 11 bears captured in 1990, eight were radio-collared. Twenty five bears were marked with ear tags during the study period. During the 1990 hunting season, 4 of the 25 marked bears were legally harvested by hunters.
The harvest rates of 15-20% were comparable to the average statewide harvest. Based on observations of hunting pressure on and off the study area and discussions with bear hunters, they were aware of the research but did not avoid the study area. Bear hunters who harvested radio-collared bears indicated they saw ear-tags but did not see collars on the bears they took.
Harvest rates in the Great Lakes region of near and above 20% have been shown to be acceptable for sustaining the bear population. Information on population trends, harvest quotas, bear productivity and survival shows that hunting doesn�t have a negative impact on black bear population in Wisconsin.
Management implications
The primary goal for black bears in Wisconsin should be to maintain the large blocks of uneven-aged forested land like that found in the northern part of the state. Timber harvest practices allow for this diversity and benefit bears and other wildlife species. One limiting factor on bears in Wisconsin appears to be human intolerance, though attitudes of northern Wisconsin residents have allowed black bears to exist in higher densities than in most other states. As human populations increase in bear range, the best management plan will be an intensive education program. Increasing the public�s knowledge of bears and changing human attitudes will change the definition of a �nuisance� bear.
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