The feeding ecology and activity budget of proboscis monkeys

Abstract

A group of proboscis monkeys (Nasalis larvatus) consisting of an alpha-male, six adult females, and several immatures was observed from May 2005-2006. We collected over 1,968 hr of focal data on the adult male and 1,539 hr of focal data on the six females in a forest along the Menanggul River, Sabah, Malaysia. Availability and seasonal changes in plant species consumed by the focal monkeys were determined by vegetation surveys carried out across an area of 2.15 ha along 200-500 m trails in riverine forest. A total of 188 plant species were consumed by the focal monkeys. The activity budget of members of our study group was 76.5% resting, 19.5% feeding, and 3.5% moving. Young leaves (65.9%) and fruits (25.9%) accounted for the majority of feeding time. Over 90% of fruit feeding involved the consumption of unripe fruits and in the majority of case both the fruit flesh and seeds were eaten. Although fruit eating was rare in some months, during other times of the year time fruit feeding exceeded the time devoted to young leaves. We found that monthly fruit availability was positively related to monthly fruit eating and feeding activity, and seasonal fluctuations in dietary diversity were significantly affected by fruit eating. These results suggest that fruit availability and fruit-eating behaviors are key factors that influence the activity budget of proboscis monkeys. Earlier assumptions that colobine monkeys are obligate folivores do not apply well to proboscis monkeys and certain other colobines. Our findings may help contribute to a better understanding of the dietary adaptations and feeding ecology of Asian colobines.

Regurgitation and remastication in the foregut-fermenting proboscis monkey ( Nasalis larvatus )

“…Proboscis monkeys are the largest foregut-fermenting primates and ingest a diet consisting of various proportions of leaves and fruit [21]. They are endemic to Borneo and inhabit mangroves, swamps and riverine forests.…”

Use and Selection of Sleeping Sites by Proboscis Monkeys, Nasalis larvatus, along the Kinabatangan River, Sabah, Malaysia

“…We found that individuals appeared to select sleeping trees with more mature leaves, unripe and ripe fruits than surrounding trees. By referring to a previous study conducted in the Kinabatangan region [Matsuda et al, 2009] as well as to our feeding records at sleeping sites, we noticed that more than 80% of the trees (sleeping, surrounding and control) belonged to species that proboscis monkeys are known to consume. However, it is too early to be sure that food abundance is a significant factor in sleeping site selection, as we considered leaf, fruit and flower abundances for all tree species present in our plots, whether they were consumed or not by proboscis monkeys at that time.…”

“…Future studies should investigate in depth the 'food proximity' hypothesis, by recording the distance between sleeping trees and the last and first feeding trees of the day. It is known that food availability, especially of fruits, influences proboscis monkeys' daily path lengths and activity budget [Matsuda et al, 2009[Matsuda et al, , 2014, and may impact their sleeping choices as well.…”

“…We (V. Thiry) conducted behavioural observations from 17.00 h -the time of day when groups start to settle at their sleeping site locations -until 18.00-18.15 h. We used the instantaneous scan-sampling method [Altmann, 1974], with a 15-min interval. During each scan, the observer recorded the age-sex class of each individual, its behavioural activity (resting, feeding, moving, other [Matsuda et al, 2009]) and its height in tree (0-10 m; 11-20 m; 21-30 m; Bennett and Sebastian [1988]. Moreover, we differentiated adult females that were alone from those carrying an infant.…”

A Short Cut to Mushrooms – Red Langur (Presbytis rubicunda) Consumption of Terrestrial Fungus

“…A large part of the species range is in peat swamp, an extremely threatened ecosystem [Prentice and Parish, 1991;Rieley et al, 1997;Harrison et al, 2007Harrison et al, , 2011Miettinen et al, 2012]. The subfamily Colobinae consists of predominantly leaf-eating primates [Chivers and Hladik, 1980;Oates et al, 1980;Kool, 1986;Duc et al, 2009;Matsuda et al, 2009] and has evolved gastro-intestinal adaptations to exploit this abundant resource [Bauchop and Martucci, 1968;Chivers, 1994]. A multi-chambered stomach containing a microbe suspension in the foregut, plus a capacious stomach chamber and elongated caecum simultaneously neutralize toxins and effectively break down plant wall cellulose, facilitating digestion of the high quantities of fibre, protein and vitamins generally contained within leaves and other less digestible foods [Bauchop and Martucci, 1968;Kay et al, 1976;Chivers, 1994;Kay and Davies, 1994;Tsuji et al, 2013].…”