Kin selection and gorilla reproduction

Abstract

Surveys on captive gorillas indicate that males at the blackback (subadult) age are capable of reproducing, and often do. Such information further suggests that male reproductive success decreases dramatically after reaching adulthood at approximately 13 years of age. Field data support the present hypothesis that this early breeding behavior is not idiosyncratic, but a reproductive strategy based on kin selection. The dominant male permits subadult and subordinate males to remain in the troop, breed with receptive females and assist in infant defens. Infanticide is practiced by adult males during aggressive intertroop encounters to hasten the female's return to receptivity, and thereby facilitate her transfer to their troop. The proposed hypothesis and a review of current field data are used to develop criteria for a captive breeding plan.