Post by grrraaahhh on Sept 11, 2010 14:38:37 GMT -9
Although cannibalism by black bears is uncommon. we observed four incidents during 1991 on northern Vancouver island. The frequency of cannibalism is much greater than that reported from other studies. Our objectives are to describe the incidents and discuss possible causativc factors.
Cannibalism by Black Bears in the Nimpikish Valley, British Columbia
EFFECTS OF FOOD SUPPLY, PREDATION, CANNIBALISM, PARASITES, AND OTHER HEALTH PROBLEMS ON BLACK BEAR POPULATIONS Lynn L. Rogers
Intraspecific Aggression and Cannibalism The role of resident adult black bears in aggressively preventing immigration into their ranges has been well documented in long-term population and behavior studies (Kemp 1976, Rogers 1977, Young and Ruff 1982). Resident adult males repel immigrating subadult males, reducing future competition for mates and reducing immediate competition for food, with potential benefits extending to offspring and pregnant mates. Females in Minnesota occasionally chase or fight females that encroach upon their territories (Rogers 1977), and an immigrant subadult male ran from a territorial female that did not give chase (Rogers, unpublished data). How often these potential immigrants are killed rather than evicted is unknown. Thorough studies to determine causes of death among dispersing subadult males have not been conducted. The only report I found of a free-ranging subadult male of dispersal age (2 or 3 years of age) being killed by another bear is that of LeCount (1982). In that case, a subadult male with bear bite wounds on its head was captured in June and monitored until Infection from the wounds killed the bear the following winter. Whether or not immigrants are killed directly, aggression by residents toward them conceivably could prevent their access to preferred food patches and could force them into suboptimal habitat (Rogers 1976, Bunnell and Tait 1981). This, together with the high mobility of dispersing males, may explain the disproportionately high number of subadult males that become nuisances in residential areas (Rogers et al. 1976) and the high number of these bears that are shot (Rogers 1976, Bunnell and Tait 1981). In Minnesota, eartag returns showed that at least 8 (24%) of 33 males that were born in the study area and studied there until the age of dispersal were shot outside that area as dispersing 2- or 3-year-olds. How much these losses of subadult males eventually affected population density is unknown. To properly assess the effect on population density, the losses must be considered in relation to any gains in reproductive success and cub survival among resident bears-as a result of decreased competition for food. This will require additional study. Several authors have suggested that black bear populations that are not limited by gunshot might be limited by large bears killing smaller ones (Kemp 1972, 1976, Lindzey and Meslow 1977, Bunnell and Tait 1981, LeCount 1982). Thorough study of a population in which human-related mortality is not the usual cause of adult deaths has not been conducted due in part to inaccessibility of such populations, so this idea has not been tested. Indications from studies of black bear social organization are that both males and females conceivably- could increase their fitness through prudent cannibalism (Rogers 1977). Benefits of killing genetically unrelated bears include food value of carcasses and reduction of competition for food, mates, and space. Costs are expenditures of energy and incurring injuries that lead to reduced reproductive success. Considering risk. of injury, cost:benefit ratios from cannibalism probably are most favorable when bears kill nonkin that are too small or in too vulnerable a situation to inflict significant injury. Numerous researchers have reported that bears behaving abnormally because they are drugged or in traps are attacked (Kemp 1976, Rogers 1977, Beecham 1979, Johnson and Pelton 1980). In natural situations, too, reported victims of cannibalism have been either very young bears or denning bears. Deaths of 6 cubs, 2 yearling males, a yearling female, and 2 adult denning females have been documented as follows: 1. A mother with cubs killed and ate a cub from another litter in Yellowstone National Park in late summer 1930 (Arnold 1930). 2. A male climbed a tree, killed a cub, returned to the ground, and ate it in Yellowstone National Park on 14 July 1959 (M. Hornocker, personal communication, 1974). 3. One of two radio-collared cubs accompanying their mother was killed by another bear in Arizona (LeCount, personal communication, 1982). 4. A cub was killed during or after a fight between two adults in Yosemite National Park on 17 July 1955 (Hartesveldt 1955). 5. A radio-collared yearling female that was traveling with its mother in Arizona was killed by an adult female or a subadult male according to the track size of the attacker (LeCount, personal communication, 1982). 6. A radio-collared yearling male was killed and partially eaten by a 5-year-old male in Alberta, Canada, in early fall 1976 (Tietje, Pelchat, and Ruff, personal communication, 1982). 7. A radio-collared yearling was killed by a male in Alberta, Canada, in 1977 (Ruff and Kemp 1980). 8. A large bear killed and ate a mother and two cubs at a den in the upper peninsula of Michigan in mid-April 1963 (D. Wenzel, unpublished report on file at the Michigan Department of Natural Resources Headquarters at Crystal Falls, Michigan). 9. A 16-year-old radio-collared female was dug out of a den, killed, and partially eaten by a bear in early October 1976 in Alberta, Canada. Evidence suggested the predator was a male (Teitje, Pelchat, and Ruff, personal communication, 1982). Additional evidence of attempted or actual cannibalism include reports that a male attempted to catch a cub in Yellowstone National Park (Barnes and Bray 1967); a bear scat collected in May 1973 on Long Island, Washington, contained remains of a cub (Lindzey and Meslow 1977) ; and a 5-year-old radio-collared male was dug out of its den and wounded by another bear in Alberta in mid-October 1976 (Teitje, Pelchat, and Ruff, personal communication, 1982). Despite these observations, indications are that cannibalism is rare in black bear populations studied to date. Documentation is infrequent even in garbage dumps and national parks where black bears are concentrated and highly visible. No radio- collared yearling, subadult, or adult was killed during studies in Minnesota, although undetected cannibalism of noninstrumented cubs could have occurred. Whether cannibalism is a major cause of mortality in any black bear population and whether such deaths follow any pattern other than opportunistic predation remain to be determined. Telemetry technology has now advanced to the point that instrumenting cubs and radio-tracking dispersing subadults are feasible. Thorough studies of mortality in these bears would significantly increase our knowledge of black bear biology and behavior. www.bearstudy.org/website/images/stories/Publications/Effects_of_Food_Supply_etc_on_Black_Bear_Populations.pdf
In July, investigation of the stationary location for three days of a nine year old collared male revealed the remains of a bear. Close examination of the area indicated that the collared bear pursued another bear of unknown sex and age approximately 15 m up a black ash (Fraxinus nigra) tree. As indicated by extensive claw marks some 3 m long and 1.5 cm deep, it then dragged the bear down, killed it and partially consumed it. A bed was located 8 m from the carcass and scats containing hair confirmed that a bear had eaten the carcass. The bear killed was determined to be a nine year old adult.
In early October 1995 – a particularly bad year for natural food – some forestry workers observed a large bear eating another bear. When we investigated the site several days later, all that remained of the carcass was the upper and lower jaw, some broken bones, and some claws. Although numerous bear scats containing hair were found around the remains, we were unable to determine whether it was a case of predation or scavenging. casiopa.mediamouse.ca/wp-content/uploads/2010/05/PRFO-1998-Proceedings-p169-179-Inglis-Wilton.pdf
Doc, my tiger's got an itch: the true story of a Kentucky Hill Country veterinarian who occasionally runs away with the circus
"...was a bear fight after dark and one of the older, full grown black bears managed to get to the polar bear and killed it. Before Wally knew it had happened, the black bear tore open the little polar bear and was eating on the body when Naughton found them. The grown bear had..."