Age and Sex Influence Seed Dispersal of Native and Non-Native Plants by Lion-Tailed Macaques

Abstract

Seed dispersal is a critical process in tropical forests. While interspecific variation is relatively well studied, intraspecific variation, as a consequence of differences in body size, foraging behaviors, and ranging patterns, remains understudied. Among vertebrates, primates play a critical role in seed dispersal and exhibit behavioral differences between age and sex categories, making them a suitable study system for intraspecific variation in seed dispersal. Lion-tailed macaques, an endemic frugivorous primate in the Western Ghats Biodiversity Hotspot, provide an excellent model for such studies. Here, we examined the influence of age and sex on (a) diversity of native and non-native fruits consumed; (b) quantity of native and non-native fruits consumed; (c) number of seeds dispersed; (d) movement rates; and (e) seed deposition substrates in lion-tailed macaques. We conducted over 320 h of focal animal sampling in two troops, distributed evenly across adult males, adult females, and subadult males. In both troops, adult males and subadult males consumed a greater diversity of native fruits. While adult females consumed a higher diversity and greater proportion of non-native fruits, subadult males consumed a higher proportion of native fruits. In one troop, subadult males dispersed fewer Ficus seeds than adult females. We found significant differences in relative proportions of non-native species consumed across age-sex categories, though the patterns varied across troops. Our study highlights that the relative differences across age-sex categories may differ across troops, which suggests an idiosyncratic contribution by different age-sex categories across different troops in seed dispersal and consequent recruitment of their food plants.