Infanticide across Apes: A Metanalysis of Life History Traits to Estimate Risk in Orangutans (Pongo spp.)
Category: Oral Presentation
Author(s): Juliette Suarez Robles
Presenter(s): Juliette Suarez Robles
Mentors(s): George Wittemyer, Sarah King, Nelson Gathuku
Infanticide is most commonly observed in species with slow life history traits, where females have long intervals between births; by killing dependent offspring, males may cause females to return to estrus sooner and thereby increase their own reproductive opportunities. Orangutans, in particular, are known for their extensive parental care, as they are characterized by having the longest gestation length among primates after humans. In species with extended gestation and lactation lengths as well as delayed weaning, such as orangutans, the incentive for infanticide is expected to be especially strong because the dependent offspring suppress female fertility for prolonged periods. Orangutans exhibit some of the longest inter-birth intervals (IBI) among mammals, making them a key system for evaluating the Sexual Selection Hypothesis of infanticide. In this study, comparative data from both great apes (Hominidae) and lesser apes (Hylobatidae) are used to test whether variation in life history traits—particularly gestation length, weaning age, and inter-birth interval (IBI)—can predict the likelihood of infanticide in orangutans, despite no occurrence having been documented in wild populations. Statistical models are applied to assess which life history traits in apes show higher probabilities of infanticide occurrence. The results aim to clarify whether the predicted relationship between longer developmental periods, reproductive timing, and infanticide risk is consistent across the ape phylogeny, providing broader insight into the evolutionary drivers of this behavior.