Sex-Biased Harvesting and Population Dynamics in Ungulates: Implications for Conservation and Sustainable Use
The consumptive use of wildlife in particular trophy hunting and game ranching of ungulates has been advocated as a tool for conservation in Africa. We show that these methods of harvesting differ significantly from natural predation, with trophy hunting showing extreme selection for adult males and game ranching leading to disproportionate harvests of young males. Little information, either theoretical or empirical exists concerning the effect of these harvesting regimes on the long-term population dynamics of ungulate populations.
Despite the potential effects of numerous sex-skewed harvests, in this paper we investigate one potentially deleterious effect of sex-skewed harvests. Both theory and experimental data suggest that male ungulates are limited in their absolute ability to inseminate females.
Using a Leslie-Matrix model and published data on impala, we show that the interaction between sperm limitation and harvests with highly male-biased sex ratios can lead to greatly reduced female fecundity (defined as the number of young born) and population collapse. These results are robust and suggest that present methods of harvesting may not be optimal or viable in the long term.