Spatially explicit camera trap-based lion monitoring in Tanzania's Selous–Nyerere landscape

Abstract

Recent years have seen the emergence of spatially explicit capture-recapture (SECR) modeling as the recommended tool to monitor lion populations. In this study, we apply this method to camera trap data collected within Tanzania's Selous–Nyerere landscape, which is considered one of the species' few remaining strongholds in Africa. We estimated lion population density through SECR modeling of camera trap data from seven sites within Nyerere National Park (NP) and Selous Game Reserve (GR), the largest protected areas in the complex, to examine variation in lion population density. Our findings reveal lion population densities ranging from 0.33 (95% CIs: 0.12–0.91) lions over 1 year of age per 100 km² in the dry eastern Miguruwe sector of Selous GR to 6.27 (95% CIs: 4.18–9.39) individuals over 1 year per 100 km² in the prey-rich lakes area of the Matambwe sector of Nyerere NP. Dry season lion density in the system appears to be primarily driven by prey availability, which is itself principally determined by the productivity of miombo woodlands. However, evidence of human impacts and lower than expected densities at some sites suggest that anthropogenic pressure may be affecting Selous–Nyerere's lion population, particularly in areas close to boundaries. We show that camera trap-based monitoring combined with SECR can be a valuable tool to monitor lion populations in remote areas, particularly as it allows for simultaneous monitoring of other large carnivores, provides insights into wider mammal communities, aids the identification of threats, and can form the basis of sustainable offtake quotas. Our findings also demonstrate the importance of direct monitoring to understand how carnivore populations are faring and inform evidence-based conservation management.