A review of spotted hyaena population estimates highlights the need for greater utilisation of spatial capture-recapture methods

Abstract

As apex predators with a regulating effect on interspecific competitors and prey demographics, monitoring of spotted hyaena (Crocuta crocuta) population trends can provide a reliable indicator of ecosystem health. However, the ability of current survey techniques to monitor carnivore densities effectively are increasingly questioned. This has led recent studies to advocate increased application of spatial capture-recapture (SCR) methods to estimate population density for large carnivores. We reviewed the literature regarding methods used to estimate population density for spotted hyaena since 2000. Our review found that SCR methods are underutilised for estimating spotted hyaena density, with only eight published studies (13% of articles assessed) using an SCR approach. Call-in surveys were the most frequently used method, featuring in 47% of studies. However, 63% of studies that used call-in surveys could not estimate a site-specific calibration index. The calibration index estimates the distance and rate at which the focal species responds to audio lures and, as response rates are impacted by site-specific ecological and environmental factors, studies that could not calibrate this index are likely inaccurate. Further application of SCR techniques will allow more robust estimation of spotted hyaena density, reducing uncertainty and potential overestimation that limit inference from existing survey methods.