Seed dispersal by proboscis monkeys: the case of Nauclea spp.

Abstract

Frugivorous vertebrates, such as primates, are important dispersal agents in tropical forests, although the role of folivorous colobines is generally not considered. However, recent studies reported seed dispersal by endo-and epizoochory in colobine primates, including the proboscis monkey (Nasalis larvatus), suggesting the role colobines play in seed dispersal might have been underestimated. In the Lower Kinabatangan Floodplain, in Sabah, Malaysian Borneo, we investigated whether seeds were still able to germinate after being ingested by proboscis monkeys. Faecal samples (n = 201) from proboscis monkeys were collected between 2015 and 2017. Intact seeds belonging to eight plant species were found in 77% of the faecal samples. Nauclea spp. was the most abundant plant species, accounting for 98% of all intact seeds. This study is the first to conduct germination trials on seeds defecated by proboscis monkeys. Higher germination success was recorded in ingested Nauclea spp. seeds than in control seeds, from both ripe and unripe Nauclea orientalis fruits (P < 0.001). Therefore, we suggest that proboscis monkeys play a role in seed dispersal, by enhancing the germination success of defecated seeds, for at least some plant species. Similar to other colobines, although proboscis monkeys may provide a lower contribution to seed dispersal (low seed diversity over short distances) than other sympatric frugivores, this study emphasises that proboscis monkeys do contribute to the dispersal of intact seeds, such as Nauclea spp., in potentially suitable riverine habitats.

Endozoochorous seed dispersal by golden snub‐nosed monkeys in a temperate forest

“…seeds (length <2 mm) were higher than those of control seeds for both ripe and unripe fruits that were ingested by proboscis monkeys (Thiry et al . 2019). In Indonesia, compared with the controls, lower germination success was recorded in Ficus spp.…”

“…2013; Thiry et al . 2019), and Javan lutungs ( Trachypithecus auratus ) (Tsuji et al . 2017) are all endochorous seed dispersers.…”