Modelling the Effect of Fences on the Viability of Spatially Structured Populations of African Wild Dogs
Although fences often have positive effects by protecting land from urban sprawl, poaching or encroaching livestock, they may also have negative effects related to animal movement and demographics. The African wild dog (Lycaon pictus) is a large, group-living carnivore that has some of the largest home ranges recorded among terrestrial carnivores, and it also disperses over long distances. This species can therefore be expected to suffer from the negative effects of fences due to restricted movement. We used stochastic population models to investigate the effect of varying levels of fence penetrability on the viability of spatially structured wild dog populations. We evaluated the effect of fences in both a source–sink scenario, in which we assumed one large source population and several smaller sink populations, and a metapopulation consisting of a range of subpopulations of equal size. The demographic effects of fences were higher in the source–sink scenario than in the metapopulation scenario, unless all subpopulation connections in the metapopulation were fenced. Metapopulations were also more sensitive to the effect of fences if they had a large number of connections. Although our study showed that fences can have negative effects on the viability of spatially structured wild dog populations, conflicting empirical data from South Africa suggest that these conclusions may not apply to all management scenarios. We recognize that these conflicting data are caused by the relative effects of the strength of density-dependent population regulation inside of fences and the mortality rates outside of fenced areas. While acknowledging that we only considered the direct demographic effects of constraints in animal movements caused by fences, we suggest that large protected areas are still the best way to manage for viable populations of large carnivores in most situations.
We are grateful to Mark Boyce, Matt Hayward and Kyran Kunkel for helpful comments on this chapter.
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