The response of lions and spotted hyaenas to sound playbacks as a technique for estimating population size

Overall, 217 lions (>1 year) Panthera leo (Linnaeus) and 2069 spotted hyaenas (>8 mo) Crocuta crocuta (Erxleben) responded to broadcast vocalizations, call‐ins, during six surveys in the Masai Mara National Reserve, Kenya.
Carnivore response varied seasonally and was significantly higher and more uniform when migratory prey were absent. Variation in wildebeest abundance, by affecting food availability, was the only significant predictor of response. Variability in response with overall prey abundance was higher for lions than hyaenas. Lion response occurred within a radius of 2·5 km, was independent of age and sex but dropped virtually to zero whenever lions possessed a carcass at the time of broadcasting.
An independent total census recorded 547 lions (all ages) in the Reserve, 9·96% of which were nomads. This proportion increased by 7·94% following the influx of migrants and raised lion (>1 year) density from 0·292 to 0·320 lions/km². The call‐in estimate of 0·294±0·009 (95% c.l.) lions/km² practically equalled the total count. The high precision and low bias (−0·224%) of this estimate imply that call‐in surveys are reliable and may be employed to effectively monitor carnivore populations in the long term. Under simple random sampling, covering about 20% of an area would seem adequate to produce reliable density estimates.