Unreliable or no assessment of predisposition of prey, or using simplistic models (such as predator:prey ratios) to infer predation effects, similarly contribute to misinformed views of predation. Confusion also comes from predator-prey investigations most do little more than simply identify causes of death of prey, which says nothing of the effect of predation on prey. Highlighting this complexity, few examples exist of predator control having any positive effect on prey populations in the Southwest. Communities in turn are affected by whether predation is primarily compensatory or additive because high levels of additive predation can destabilize communities. Hence, the overall survival rate of the population is not decreased, so predation has little effect on the population. Compensatory mortality means that instead of adding additional mortality to the population (i.e., additive mortality), increases in predation result in compensatory declines in other causes of mortality. Predisposition is necessary for predation to be compensatory, or substitutive, at the level of the population. The greater the degree of predisposition, the less likely the death of a predated individual would have any effect on the population. Predisposition influences whether (or how likely it was that) an individual would have lived if not killed by a predator. At the individual level, predisposition refers to characteristics (e.g., poor body condition, inadequate cover, disease, etc.) of individuals that make them more or less likely to die from predation or any other cause. This view is frequently wrong, and ignores the complexity of predation at the individual, population, and community levels. Most people confuse the act of predation with the effect, believing that the killing of an individual animal invariably results in a negative impact on the population (Figure 1). Predation is a much misunderstood ecological process. Bender College of Agricultural, Consumer and Environmental SciencesĪuthor: Senior Research Scientist (Natural Resources), Department of Extension Animal Sciences and Natural Resources, New Mexico State University.
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