Female philopatry and its social benefits among Bornean orangutans

Abstract

Female philopatry in mammals is generally associated with ecological and sometimes social benefits, and often with dispersal by males. Previous studies on dispersal patterns of orangutans, largely non-gregarious Asian great apes, have yielded conflicting results. Based on 7 years of observational data and mitochondrial and nuclear DNA analyses on fecal samples of 41 adult Bornean orangutans (Pongo pygmaeus wurmbii) from the Tuanan population, we provide both genetic and behavioral evidence for male dispersal and female philopatry. Although maternally related adult female dyads showed similar home-range overlap as unrelated dyads, females spent much more time in association with known maternal relatives than with other females. While in association, offspring of maternally related females frequently engaged in social play, whereas mothers actively prevented this during encounters with unrelated mothers, suggesting that unrelated females may pose a threat to infants. Having trustworthy neighbors may therefore be a social benefit of philopatry that may be common among solitary mammals, thus reinforcing female philopatric tendencies in such species. The results also illustrate the diversity in dispersal patterns found within the great-ape lineage. Female philopatry in mammals is generally associated with ecological and sometimes social benefits, 1 and often with dispersal by males. Previous studies on dispersal patterns of orangutans, largely non-2 gregarious Asian great apes, have yielded conflicting results. Based on seven years of observational 3 data and mitochondrial and nuclear DNA analyses on fecal samples of 41 adult Bornean orangutans 4 (Pongo pygmaeus wurmbii) from the Tuanan population, we provide both genetic and behavioral 5 evidence for male dispersal and female philopatry. Although maternally related adult female dyads 6showed similar home-range overlap as unrelated dyads, females spent much more time in association 7 with known maternal relatives than with other females. While in association, offspring of maternally 8 related females frequently engaged in social play, whereas mothers actively prevented this during 9 encounters with unrelated mothers, suggesting that unrelated females may pose a threat to infants. 10

Variation in developmental arrest among male orangutans: a comparison between a Sumatran and a Bornean population

“…We can therefore exclude logging as a general cause for possible island differences in morph ratios. Furthermore we can exclude differences in dispersal between populations of the two islands as recent studies convincingly showed that on both islands males are the dispersing sex, whereas females are philopatric [24,29,60-62]. …”

Reconstructing the demographic history of orang‐utans using Approximate Bayesian Computation

“…; van Noordwijk et al . ). The third model (IM2‐GR) additionally allowed the two populations to change size exponentially after the population split and corresponded largely to the favoured model in the genomic study by Locke et al .…”

“…; van Noordwijk et al . ), mitochondrial markers contain information about population split times without the confounding influence of gene flow. In contrast, Y‐chromosomal loci should have more power than autosomal markers to reveal low levels of male‐mediated gene flow.…”

Male orang-utan bimaturism and reproductive success at Camp Leakey in Tanjung Puting National Park, Indonesia

“…exist in a semi-solitary society with roving promiscuity (van Schaik and van Hooff 1996), in which the relatively smaller, philopatric home ranges of females are enveloped by those of dispersing adult males (Galdikas 1985a;van Noordwijk et al 2012). Such males exhibit bimaturism, expressing one of two morphological forms (Fig.…”