Age and sex influence seed dispersal of native and non-native plants by Lion-tailed Macaques Macaca silenus

Abstract

While interspecific variation in seed dispersal, a critical ecosystem process in tropical forests, is relatively well-studied, intraspecific variation as a consequence of differences in body size, foraging behaviours, and ranging patterns among age-sex categories within a species is relatively understudied. Among vertebrates, primates play a critical role in seed dispersal and exhibit behavioural differences between age and sex categories, making them a suitable study system for intraspecific variation in seed dispersal. Lion-tailed macaques Macaca silenus, an endemic and predominantly frugivorous primate species in the Western Ghats Biodiversity Hotspot, provide an excellent model for such studies. We examined the influence of age and sex on 1) the diversity and 2) the quantity of native and non-native fruits consumed, 3) the number of seeds dispersed, 4) seed dispersal distance, and 5) seed deposition substrates in lion-tailed macaques. We conducted over 375 hours of focal animal watches, distributed evenly across adult males, females, and subadults. Our findings showed that subadults consumed a higher diversity of native and non-native fruits than females and males. They dispersed fewer Ficus seeds than females. We found differences in the proportions of non-native fruits in the diets of different age- sex categories. Males consumed more Coffea liberica, whereas females and subadults fed on Coffea and Lantana. We found weak evidence suggesting that males were more likely to disperse Ficus seeds on trees, which are suitable substrates for Ficus establishment. Our study highlights that age and sex significantly influence seed dispersal patterns of native and non- native species by an endemic, frugivorous primate species with potential influence on recruitment.