Neglected seed dispersers: endozoochory by Javan lutungs (Trachypithecus auratus) in Indonesia

Abstract

Leaf monkeys are known to be leaf eaters, and thus, their potential role as seed dispersers has been neglected. However, they do also feed on fruits. To examine the role of leaf monkeys as endozoochorous seed dispersers, we studied the Javan lutung (Trachypithecus auratus) in Indonesia. We compared multiple aspects of seed dispersal processes (amount and diversity of seeds ingested, dispersal distance, and germination rate) of lutungs with that of the sympatric long‐tailed macaque (Macaca fascicularis). Over the study period, 54 percent of the lutung feces contained intact seeds, which was equivalent to the macaque feces contained seeds (62%). Seeds of at least six plant species were detected in the lutung feces, which was less than those found in the macaque feces (>19 plant species). The main species of seeds defecated by both lutungs and macaques was Ficus spp. (seed size: 0.7 mm). Seed shadow, estimated from travel distance (range: 1–299 m) and gut passage rate (24–96 h), had a unimodal‐distribution with a peak at 51–100 m, and was shorter than that reported in published accounts of macaques and other similar and smaller sized frugivores. Finally, germination rates of Ficus spp. seeds ingested by both lutungs and macaques were lower than that of the control seeds. These results imply that the dispersal effectiveness of lutungs would be lower than that of the sympatric primate frugivores. However, at a population level, lutungs could play a significant role as seed dispersers for the small‐seeded species, and therefore, more research into their frugivorous habits is warranted.

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

“…This result differs from a previous study on another colobine, the Javan lutung (T. auratus), where lower germination success (only 5%) was observed in defecated Ficus spp. seeds than in control seeds (10%), suggesting that lutungs are not efficient fig dispersers (Tsuji et al 2017). In our study, differences are particularly striking under shade conditions (first 60 days) where the seeds ingested by proboscis monkeys started to germinate earlier and faster than the seeds extracted from fruits: at d 60, 54% of ingested seeds had already germinated, as opposed to only 7% of the control seeds (from ripe and unripe fruits).…”

“…The presence of N. orientalis seeds has already been recorded in the faeces of another colobine primate, the Javan lutung (T. auratus) in Indonesia (Tsuji et al, 2017). In our study site, silvered langurs (T. cristatus) are also known to consume N. orientalis fruits.…”

“…We focused on seed dispersal by endozoochory and aimed to investigate whether seeds were still able to germinate after being ingested by proboscis monkeys. We predicted that (1) small intact seeds would be found in proboscis monkey faeces, as reported by Matsuda et al (2013) and because small seeds might be less damaged by mastication and pass intact through the animal gut (Corlett and Lucas 1990;Norconk et al 1998), and (2) due to their feeding habits (preferring unripe fruits over ripe fruits), the seeds defecated by proboscis monkeys would experience lower germination rates than control seeds (collected directly from fruits), such as reported in the colobine Javan lutung (T. auratus) (Tsuji et al 2017).…”

“…in McConkey 2018)) and via epizoochory (Rhinopithecus roxellana (Chen et al 2018)). Even though seed germination trials were not conducted (Matsuda et al 2013;Nguyen et al 2013;Chen et al 2018) or dispersed seeds showed low germination success (Tsuji et al 2017), authors suggested that the role colobines play in seed dispersal might have been underestimated. In regard to the wide distribution and biomass of Asian and African colobines, colobine primates might play a considerable role in seed dispersal of some plant species (Matsuda et al 2013;Corlett 2017;Tsuji et al 2017).…”

Habitat suitability analysis reveals high ecological flexibility in a “strict” forest primate

“…We here present data on a population of Javan lutung (Trachypithecus auratus), a colobine monkey endemic to the Indonesian islands of Java, Bali and Lombok that has been studied intermittently since the 1970s ( Table 1). The only long-term research has been conducted at a rainforest site in western Java, Pangandaran, where annual rainfall exceeds 3000 mm and where there is a lack of distinct dry/wet seasons [5][6][7][8][9][10]. Shorter studies, typically up to 1 year in duration, have mainly been conducted in other rainforest sites (Mt Gede-Pangrango, 3000 mm: [11]; Mts Dieng, 4000 mm: [12]; Mt Bromo-Semeru, 3500 mm: [13]; Table 1).…”