METRICS OF HARVEST FOR UNGULATE POPULATIONS: MISCONCEPTIONS, LURKING VARIABLES, AND PRUDENT MANAGEMENT
Keywords:Adaptive Management, Additive Mortality, Compensatory Mortality, Density Dependence, Harvest Metrics, Harvestable Surplus, Harvesting Females, Life-history Characteristics, Modeling, Prudent Management
Biologists often must use incomplete information to make recommendations concerning harvest of large mammals. Consequently, those recommendations must draw on a firm understanding of the ecology of the species in question, along with selection of the most applicable population characteristics on which to base harvest—both essential components for prudent management. Density-dependent processes, which are ubiquitous among populations of large mammals, may be counterintuitive because of unexpected patterns in recruitment coincident with changes in population size. Misconceptions concerning population dynamics of ungulates also can occur when demographics are based solely on correlations with environmental factors. Further, the concept of a harvestable surplus can be misleading for managing ungulate populations, because of the parabolic relationship between population size and number of recruits—harvest determines the surplus rather than vice versa. Understanding consequences of mortality, especially relative components of compensatory or additive mortality, also is necessary. Knowledge of the proximity of an ungulate population to ecological carrying capacity (K) is required to fully assess whether most mortality is compensatory or additive. We describe selected life-history traits and population characteristics of ungulates useful in parametrizing where populations are in relation to K, thereby allowing for a reasonable harvest despite some uncertainty in population size. We advocate an adaptive-management approach while monitoring those life-history traits to evaluate the suitability of a particular harvest strategy.
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