Methods for lion monitoring: a comparison from the Selous Game Reserve, Tanzania

The Selous Game Reserve in Tanzania is believed to contain Africa's largest population of lions (Panthera leo), making it a popular destination for trophy hunters and photographic tourists. However, a lack of recent data has raised concerns about the conservation status of this iconic population, so we collected two types of population data between 2006 and 2009. First, we identified 112 individual animals in an 800 km2 study area in the photographic tourism part of Selous, giving a density of 0.14 individuals km?2. This density estimate was similar to results using the same method from 1997 to 1999, but the adult sex ratio has decreased from 1 male : 1.3 female in 1997 to 1 male : 3 females in 2009. Second, using buffalo calf distress calls, we conducted call-up surveys to census lions in three hunting sectors in the west, east and south of Selous and in the northern photographic area. Estimated adult lion densities varied from 0.02 to 0.10 km?2, allowing an overall population estimate of 4,300 (range: 1,700–6,900). Our results highlight the value of call-ups in surveying cryptic hunted carnivores but stress the importance of long-term projects for calibrating the responses to call-ups and for measuring trends in demography and population size.