Reproductive success of female leopards Panthera pardus: the importance of top-down processes

摘要

Long-term studies on large felids are rare and yet they yield data essential to understanding the behaviour of species and the factors that facilitate their conservation. We used the most extensive data set so far compiled on leopards Panthera pardus to establish baseline reproductive parameters for females and to determine the demographic and environmental factors that affect their lifetime reproductive success. We used comprehensive sightings reports and photographs from ecotourism lodges in the Sabi Sand Game Reserve, South Africa, to reconstruct life histories for 44 female leopards that gave birth to 172 litters over a 32-year period. Leopards appeared to exhibit a birth pulse; most litters were born in the wet season, particularly in December. Mean age at first parturition (n=26, mean +/- standard error=46 +/- 2 months, range=33-62) was older than previously recorded, possibly due to elevated intraspecific competition. Average litter size was 1.9 +/- 0.1 (n=140, range=1-3) and declined with maternal age. Age of litters at independence (n=52, 19 +/- 1 months, range=9-31) was inversely related to prey abundance but did not affect the likelihood of recruitment of offspring. Interbirth intervals differed following successful litters (in which at least one cub survived to independence; n=55, 25 +/- 1 months, range=14-39) and unsuccessful litters (n=46, 11 +/- 1 months, range=4-36), as did the time taken to replace litters. Variation in lifetime reproductive success was influenced mainly by differences in cub survival, which was related to maternal age and vulnerability to infanticide. Cub survival (37%) declined as females got older, perhaps because mothers relinquished portions of their home ranges to philopatric daughters. Male leopards were responsible for many (40%) cub deaths and females appeared to adopt severalstrategies to counter the risk of infanticide, including paternity confusion and displaying a period of reduced fertility immediately after a resident male was replaced. Our results suggest that the reproductive success of female leopards is regulated primarily by top-down processes. This should be taken into account in management decisions, particularly when managers are considering the implementation of invasive activities such as legal trophy hunting.