Beschreibung:
<p>So far only a few studies have documented that food limitation regulates numbers in large ungulate populations. In this review I evaluate recent predator-ungulate studies to 1) assess the role of predators in regulation of ungulate populations, and (2) whether the outcome of such interactions could be predicted from predator-prey models. Recent studies suggest that environmental productivity plays a role in predator-prey interactions. In order to test this hypothesis I evaluated predator-large ungulate biomass data along a northsouth gradient from arctic to tropical ecosystems (3). (1) Several cases of limitation by predators were found. But in the majority of cases, in heterogeneous and seasonal environments, nomadism, prey refuges and differential prey-age vulnerability by the dominant ungulate species may have counteracted regulation by predators. In the more impoverished arctic and northern environments food-chains in some instances lacked predators and ungulates were food-limited, as were predators at low prey densities. In most instances predators were limited by territoriality. (2) Empirical evidence was only rarely (and in most instances untested) in agreement with predictions from predator-prey models. (3) Support for the hypothesis that higher environmental productivity facilitates predator regulation of ungulates was not evident. Studies so far suggest that spacing behaviour by ungulates due to environmental heterogeneity could be the single most important factor to counteract regulation by predators.</p>