Effects of a protection gradient on carnivore density and survival: an example with leopards in the Luangwa valley, Zambia

Abstract

Human activities on the periphery of protected areas can limit carnivore populations, but measurements of the strength of such effects are limited, largely due to difficulties of obtaining precise data on population density and survival. We measured how density and survival rates of a previously unstudied leopard population varied across a gradient of protection and evaluated which anthropogenic activities accounted for observed patterns. Insights into this generalist's response to human encroachment are likely to identify limiting factors for other sympatric carnivore species. Motion‐sensitive cameras were deployed systematically in adjacent, similarly sized, and ecologically similar study areas inside and outside Zambia's South Luangwa National Park (SLNP) from 2012 to 2014. The sites differed primarily in the degree of human impacts: SLNP is strictly protected, but the adjacent area was subject to human encroachment and bushmeat poaching throughout the study, and trophy hunting of leopards prior to 2012. We used photographic capture histories with robust design capture–recapture models to estimate population size and sex‐specific survival rates for the two areas. Leopard density within SLNP was 67% greater than in the adjacent area, but annual survival rates and sex ratios did not detectably differ between the sites. Prior research indicated that wire‐snare occurrence was 5.2 times greater in the areas adjacent to the park. These results suggest that the low density of leopards on the periphery of SLNP is better explained by prey depletion, rather than by direct anthropogenic mortality. Long‐term spatial data from concurrent lion studies suggested that interspecific competition did not produce the observed patterns. Large carnivore populations are often limited by human activities, but science‐based management policies depend on methods to rigorously and quantitatively assess threats to populations of concern. Using noninvasive robust design capture–recapture methods, we systematically assessed leopard density and survival across a protection gradient and identified bushmeat poaching as the likely limiting factor. This approach is of broad value to evaluate the impacts of anthropogenic activities on carnivore populations that are distributed across gradients of protection.

Testing the effects of anthropogenic pressures on a diverse African herbivore community

“…, Rosenblatt et al. , ), and prey depletion within the national park itself is notable in this case. Depletion of large herbivores in KNP is linked to long‐term illegal bushmeat poaching at unsustainable levels (Overton et al.…”

“…, , Rosenblatt et al. ). In KNP, a comparison of carnivore diets now and 50 yr ago showed that the importance of relatively abundant smaller‐bodied herbivores has increased, whereas the importance of larger‐bodied herbivores has decreased (Creel et al.…”

The relative effects of prey availability, anthropogenic pressure and environmental variables on lion (Panthera leo) site use in Tanzania's Ruaha landscape during the dry season

“…Poaching and displacement by livestock are known factors contributing to prey depletion (Ripple et al ., ), which can be even more detrimental to carnivores than direct anthropogenic mortality (Rosenblatt et al ., ). These effects can alter lion populations (Henschel et al ., ), and are likely limiting lion occurrence in the village lands.…”

Changes in African large carnivore diets over the past half‐century reveal the loss of large prey

“…Although many African ecosystems have maintained all of their large carnivores, the lion Panthera leo , leopard Panthera pardus , cheetah Acinonyx jubatus , and African wild dog Lycaon pictus are all considered vulnerable or endangered, and all show decreasing population trends (IUCN, ). Threats to these carnivores vary among species and populations, but common problems include habitat loss and human encroachment on protected areas (Riggio et al., ; Ripple et al., ; Watson, Becker, Milanzi, & Nyirenda, ), legal and illegal direct killing (Becker et al., ; Creel et al., ; Hofer, Campbell, East, & Huish, ; Ogada, Woodroffe, Oguge, & Frank, ; Packer et al., ; Whitman, Starfield, Quadling, & Packer, ), and prey depletion (Estes et al., ; Fa & Brown, ; Ripple et al., ; Rosenblatt et al., ).…”

“…It is well-recognized that depletion of prey populations is occurring in many ecosystems, mainly due to habitat loss and illegal harvest (Bolger, Newmark, Morrison, & Doak, 2008;Fa & Brown, 2009;Ripple et al, 2015;Western, Russell, & Cuthill, 2009), and a recent review found that 65% of large carnivores have experienced an increase in the proportion of their prey that is considered vulnerable, threatened, or endangered (Wolf & Ripple, 2016). In short, it is widely recognized that prey depletion can be a strong driver of carnivore declines (Fuller & Sievert, 2001;Karanth & Stith, 1999;Midlane, 2014;Ripple et al, 2015;Rosenblatt et al, 2016). Despite this recognition, there has been little direct research on the manner in which prey depletion alters the diets of large carnivores.…”