Emigration of subadult lions

Abstract

Factors relating to whether subadult lions, Panthera leo, left or stayed in their natal pride were examined for 122 subadults living in Serengeti National Park and Ngorongoro Crater, Tanzania. The 10 variables considered were: sex, age, age-set composition and size, relations with adult males and with adult females, food availability, competition with other pride members, mating opportunities, pride size and population density. The emigration of subadults was influenced by their age and sex, but was most highly correlated with the entry of unfamiliar adult males to the pride. Subadult males always left; subadult females became peripheral or left, unless they were able to mate with the new males. Early mating by such females did not result in early parturition, and may be a sociosexual mechanism allowing them to remain with the pride after a male take-over. If no new males entered the pride, subadults tended to remain, despite increasing aggression from pride members. They did not mate with close relatives, but some left the pride either temporarily or permanently to mate with unfamiliar partners. Pride size was not correlated with subadult emigration, but high population density appeared to facilitate it.