Hypotheses of the Effects of Wolf Predation Essay Example For Students

Hypotheses of the Effects of Wolf Predation Essay John FeldersnatchDecember 1st, 1995Abstract: This paper discusses four hypotheses to explain the effects of wolfpredation on prey populations of large ungulates. The four proposed hypothesesexamined are the predation limiting hypothesis, the predation regulatinghypothesis, the predator pit hypothesis, and the stable limit cycle hypothesis. There is much research literature that discusses how these hypotheses can beused to interpret various data sets obtained from field studies. It wasconcluded that the predation limiting hypothesis fit most study cases, but thatmore research is necessary to account for multiple predator multiple preyrelationships. The effects of predation can have an enormous impact on the ecologicalorganization and structure of communities. The processes of predation affectvirtually every species to some degree or another. Predation can be defined aswhen members of one species eat (and/or kill) those of another species. Thespecific type of predation between wolves and large ungulates involvescarnivores preying on herbivores. Predation can have many possible effects onthe interrelations of populations. To draw any correlations between the effectsof these predator-prey interactions requires studies of a long duration, andstatistical analysis of large data sets representative of the populations as awhole. Predation could limit the prey distribution and decrease abundance. Suchlimitation may be desirable in the case of pest species, or undesirable to someindividuals as with game animals or endangered species. Predation may also actas a major selective force. The effects of predator prey coevolution can explainman y evolutionary adaptations in both predator and prey species. The effects of wolf predation on species of large ungulates have proven to becontroversial and elusive. There have been many different models proposed todescribe the processes operating on populations influenced by wolf predation. Some of the proposed mechanisms include the predation limiting hypothesis, thepredation regulating hypothesis, the predator pit hypothesis, and the stablelimit cycle hypothesis (Boutin 1992). The purpose of this paper is to assess theempirical data on population dynamics and attempt to determine if one of thefour hypotheses is a better model of the effects of wolf predation on ungulatepopulation densities. The predation limiting hypothesis proposes that predation is the primary factorthat limits prey density. In this non- equilibrium model recurrent fluctuationsoccur in the prey population. This implies that the prey population does notreturn to some particular equilibrium after deviation. The predation limitinghypothesis involves a density independent mechanism. The mechanism might applyto one prey one predator systems (Boutin 1992). This hypothesis predicts thatlosses of prey due to predation will be large enough to halt prey populationincrease. Many studies support the hypothesis that predation limits prey density. Bergerudet al. (1983) concluded from their study of the interrelations of wolves andmoose in the Pukaskwa National Park that wolf predation limited, and may havecaused a decline in, the moose population, and that if wolves were eliminated,the moose population would increase until limited by some other regulatoryfactor, such as food availability. However, they go on to point out that thisupper limit will not be sustainable, but will eventually lead to resourcedepletion and population decline. Seip (1992) found that high wolf predation oncaribou in the Quesnel Lake area resulted in a decline in the population, whilelow wolf predation in the Wells Gray Provincial Park resulted in a slowlyincreasing population. Wolf predation at the Quesnel Lake area remained highdespite a fifty percent decline in the caribou population, indicating thatmortality due to predation was not density-dependent within this range ofpopulatio n densities. Dale et al. (1994), in their study of wolves and caribouin Gates National Park and Preserve, showed that wolf predation can be animportant limiting factor at low caribou population densities, and may have ananti-regulatory effect. They also state that wolf predation may affect thedistribution and abundance of caribou populations. Bergerud and Ballard (1988),in their interpretation of the Nelchina caribou herd case history, said thatduring and immediately following a reduction in the wolf population, calfrecruitment increased, which should result in a future caribou populationincrease. Gasaway et al. (1983) also indicated that wolf predation cansufficiently increase the rate of mortality in a prey population to prevent thepopulations increase. Even though there has been much support of thishypothesis, Boutin (1992) suggests that there is little doubt that predation isa limiting factor, but in cases where its magnitude has been measured, it is nogreater than other factors such as hunting.A second hypothesis about the effects of wolf predation is the predationregulating hypothesis, which proposes that predation regulates prey densitiesaround a low-density equilibrium. This hypothesis fits an equilibrium model, andassumes that following deviation, prey populations return to their pre-existingequilibrium levels. This predator regulating hypothesis proposes that predationis a density-dependent mechanism affecting low to intermediate prey densities,and a density-independent mechanism at high prey densities. Violence In Sports Essay SummaryThese points emphasize that multiple-predator and multiple-prey systems areprobably at work in the natural environment, and we must not over generalize aone predator one prey hypothesis in the attempt to interpret the overalltrends of the effects of predation of wolves on large ungulate populations. Literature CitedBergerud, A. T., W. Wyett, and B. Snider. 1983. The role of wolf predation inlimiting a moose population. Journal ofWildlife Management. 47(4): 977-988. Bergerud, A. T., and W. B. Ballard. 1988. Wolf predation on caribou: the Nelchina herd case history, a differentinterpretation. Journal of Wildlife Management. 52(2): 344- 357. Boutin, S.. 1992. Predation and moose population dynamics: a critique. Journal of WildlifeManagement. 56(1): 116-127. Dale, B. W., L. G. Adams, and R. T. Bowyer. 1994. Functional responseof wolves preying on barren-ground caribouin 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 ofwolves, prey, and man in interior Alaska. Wildlife Monographs. 84: 1- 50. Messier, F.. 1985. Social organization, spatial distribution, and populationdensity of wolves in relation to moosedensity. Canadian Journal of Zoology. 63: 1068-1077. Messier, F.. 1994. Ungulate population models with predation: a case study with the North Americanmoose. Ecology. 75(2): 478-488. Seip, D.. 1992. Factors limiting woodland cariboupopulations and their interrelationships with wolves and moose insoutheastern British Colombia. Canadian Journal of Zoology. 70: 1494-1503. Thompson, I. D., and R. O. Peterson. 1988. Does wolf predation alone limit themoose 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 ofWildlifeManagement. 49(3): 711-720. Category: Science