Wolf Predation

.. ates that wolf population regulation is needed when a caribou herd population declines and becomes trapped in a predator pit, wherein predators are able to prevent caribou populations from increasing. The final model that attempts to describe the effects of predation on prey populations is the stable limit cycle hypothesis. This hypothesis proposes that vulnerability of prey to predation depends on past environmental conditions. According to this theory, individuals of a prey population born under unfavorable conditions are more vulnerable to predation throughout their adult lives than those born under favorable conditions. This model would produce time lags between the proliferation of the predator and the prey populations, in effect generating recurring cycles.

Boutin (1992) states that if this hypothesis is correct, the effects of food availability (or the lack of) should be more subtle than outright starvation. Relatively severe winters could have long- term effects by altering growth, production, and vulnerability. Thompson and Peterson (1988) reported that there are no documented cases of wolf predation imposing a long-term limit on ungulate populations independent of environmental influences. They also point out that summer moose calf mortality was high whether predators were present or not, and that snow conditions during the winter affected the vulnerability of calves to predation. Messier (1994) asserts that snow accumulation during consecutive winters does not create a cumulative impact on the nutritional status of deer and moose.

All of the four proposed theories mentioned above could describe the interrelationships between the predation of wolves and their usual north american prey of large ungulate species. There has been ample evidence presented in the primary research literature to support any one of the four potential models. The predation limiting hypothesis seems to enjoy wide popular support, and seems to most accurately describe most of the trends observed in predator-prey populations. Most researchers seem to think that more specific studies need to be conducted to find an ideal model of the effects of predation. Bergerud and Ballard (1988) stated A simple numbers argument regarding prey:predator ratios overlooks the complexities in multi-predator-prey systems that can involve surplus killing, additive predation between predators, enhancement and interference between predator species, switch over between prey species, and a three-fold variation in food consumption rates by wolves. Dale et al.

(1994) stated that further knowledge of the factors affecting prey switching, such as density-dependent changes in vulnerability within and between prey species, and further knowledge of wolf population response is needed to draw any firm conclusions. Boutin (1992) also proposed that the full impact of predation has seldom been measured because researchers have concentrated on measuring losses of prey to wolves only. Recently, bear predation on moose calves has been found to be substantial, but there are few studies which examine this phenomenon (Boutin 1992). Messier (1994) also pointed out that grizzly and black bears may be important predators of moose calves during the summer. Seip (1992), too, states that bear predation was a significant cause of adult caribou mortality.

These points emphasize that multiple-predator and multiple-prey systems are probably at work in the natural environment, and we must not over generalize a one predator – one prey hypothesis in the attempt to interpret the overall trends of the effects of predation of wolves on large ungulate populations. Literature Cited Bergerud, A. T., W. Wyett, and B. Snider. 1983.

The role of wolf predation in limiting a moose population. Journal of Wildlife Management. 47(4): 977-988. Bergerud, A. T., and W. B. Ballard.

1988. Wolf predation on caribou: the Nelchina herd case history, a different interpretation. Journal of Wildlife Management. 52(2): 344- 357. Boutin, S. 1992.

Predation and moose population dynamics: a critique. Journal of Wildlife Management. 56(1): 116-127. Dale, B. W., L.

G. Adams, and R. T. Bowyer. 1994.

Functional response of wolves preying on barren-ground caribou in a multiple prey ecosystem. Journal of Animal Ecology. 63: 644- 652. Gasaway, W. C., R. O.

Stephenson, J. L. Davis, P. E. K.

Shepherd, and O. E. Burris. 1983. Interrelationships of wolves, prey, and man in interior Alaska.

Wildlife Monographs. 84: 1- 50. Messier, F. 1985. Social organization, spatial distribution, and population density of wolves in relation to moose density. Canadian Journal of Zoology.

63: 1068-1077. Messier, F. 1994. Ungulate population models with predation: a case study with the North American moose. Ecology. 75(2): 478-488.

Seip, D. 1992. Factors limiting woodland caribou populations and ir interrelationships with wolves and moose in southeastern British Colombia. Canadian Journal of Zoology. 70: 1494-1503. Thompson, I.

D., and R. O. Peterson. 1988. Does wolf predation alone limit the moose population in Pukaskwa Park?: a comment. Journal of Wildlife Management. 52(3): 556-559. Van Ballenberghe, V.

1985. Wolf predation on caribou: the Nelchina herd case history. Journal of Wildlife Management. 49(3): 711-720. Bibliography Literature Cited Bergerud, A. T., W. Wyett, and B.

Snider. 1983. The role of wolf predation in limiting a moose population. Journal of Wildlife Management. 47(4): 977-988.

Bergerud, A. T., and W. B. Ballard. 1988.

Wolf predation on caribou: the Nelchina herd case history, a different interpretation. Journal of Wildlife Management. 52(2): 344- 357. Boutin, S. 1992. Predation and moose population dynamics: a critique.

Journal of Wildlife Management. 56(1): 116-127. Dale, B. W., L. G.

Adams, and R. T. Bowyer. 1994. Functional response of wolves preying on barren-ground caribou in a multiple prey ecosystem. Journal of Animal Ecology.

63: 644- 652. Gasaway, W. C., R. O. Stephenson, J.

L. Davis, P. E. K. Shepherd, and O. E.

Burris. 1983. Interrelationships of wolves, prey, and man in interior Alaska. Wildlife Monographs. 84: 1- 50. Messier, F. 1985.

Social organization, spatial distribution, and population density of wolves in relation to moose density. Canadian Journal of Zoology. 63: 1068-1077. Messier, F. 1994. Ungulate population models with predation: a case study with the North American moose.

Ecology. 75(2): 478-488. Seip, D. 1992. Factors limiting woodland caribou populations and ir interrelationships with wolves and moose in southeastern British Colombia. Canadian Journal of Zoology.

70: 1494-1503. Thompson, I. D., and R. O. Peterson. 1988.

Does wolf predation alone limit the moose population in Pukaskwa Park?: a comment. Journal of Wildlife Management. 52(3): 556-559. Van Ballenberghe, V. 1985. Wolf predation on caribou: the Nelchina herd case history. Journal of Wildlife Management.

49(3): 711-720.

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