Detecting declines of apex carnivores and evaluating their causes: An example with Zambian lions

Large carnivores are in rapid global decline, with a broad array of consequences for the ecosystems they inhabit. To efficiently detect and address these declines requires unbiased and precise demographic data. Unfortunately, the characteristics that make large carnivores extinction-prone also pose serious challenges to obtaining these data. Rapid survey methods exist, but provide only relative measures of abundance, cannot detect declines before they become large, and provide little or no information about the causes of decline. African lions (Panthera leo) are declining throughout their range, making accurate monitoring of remaining populations urgent. We provide statistically rigorous estimates of population size, trends, survival rate and age–sex structure from Zambia’s South Luangwa lion population from 2008 to 2012, just prior to cessation of hunting in 2013. Mark-recapture models fit to data from intensive monitoring of 210 individual lions in 18 prides and 14 male coalitions indicated a declining population, low recruitment, low sub-adult and adult male survival, depletion of adult males, and a senescing adult female population. Trophy hunting was the leading cause of death, with 46 males harvested. Based on these data we recommend continuing the hunting ban at least to 2016 to allow recovery, with substantially reduced quotas, age-limits, and effective trophy monitoring mandated thereafter should hunting resume. Similar data from intensive monitoring of key Zambian lion populations is required to evaluate effects of the hunting ban and provide management guidance. Effectively integrating intensive long-term monitoring and rapid survey methods should be a priority for future management and monitoring of carnivore species.