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

Abstract

The choice of a sleeping site is crucial for primates and may influence their survival. In this study, we investigated several tree characteristics influencing the sleeping site selection by proboscis monkeys (Nasalis larvatus) along Kinabatangan River, in Sabah, Malaysia. We identified 81 sleeping trees used by one-male and all-male social groups from November 2011 to January 2012. We recorded 15 variables for each tree. Within sleeping sites, sleeping trees were taller, had a larger trunk, with larger and higher first branches than surrounding trees. The crown contained more mature leaves, ripe and unripe fruits but had vines less often than surrounding trees. In addition, in this study, we also focused on a larger scale, considering sleeping and non-sleeping sites. Multivariate analyses highlighted a combination of 6 variables that revealed the significance of sleeping trees as well as surrounding trees in the selection process. During our boat surveys, we observed that adult females and young individuals stayed higher in the canopy than adult males. This pattern may be driven by their increased vulnerability to predation. Finally, we suggest that the selection of particular sleeping tree features (i.e. tall, high first branch) by proboscis monkeys is mostly influenced by antipredation strategies.

Combining drones and satellite tracking as an effective tool for informing policy change in riparian habitats: a proboscis monkey case study

“…; Thiry et al. ). This is particularly the case for groups with vulnerable or small individuals, that is, reproductively active groups (such as the focal group of this study), as opposed to all‐male groups (Thiry et al.…”

“…This is particularly the case for groups with vulnerable or small individuals, that is, reproductively active groups (such as the focal group of this study), as opposed to all‐male groups (Thiry et al. ). The removal of trees changes the composition and structure of both edge and interior forest, as well as exposes the newly created edge to different environmental conditions (Broadbent et al.…”

“…Proboscis monkeys tend to sleep near rivers as protection against predation (Thiry et al. ), and generally do not travel more than a half day's journey away from water before returning back (Matsuda et al. ).…”

Sleeping site and tree selection by Sichuan snub‐nosed monkeys (Rhinopithecus roxellana) in Baihe Nature Reserve, Sichuan, China

“…Outside of the 200 m boundary from sleeping sites, we considered as non‐sleeping sites. At sleeping sites, trees were separated into sleeping center trees and surrounding trees (Anderson, ; Thiry et al, ). Sleeping center tree s were trees in which R. roxellana were observed to spend the night and also identified through the location of fecal pellets (Cui et al, ; Zhang et al, ).…”

“…On a smaller spatial scale, the characteristics of sleeping trees are also important, particularly for arboreal primate species (von Hippel, ; Hankerson, Franklin, & Dietz, ). They have been shown to select different characteristics of sleeping trees to (1) make access more difficult for terrestrial predators, that is, tall emergent trees (Bitetti, Vidal, Baldovino, & Benesovsky, ; Cui, Tai, Lin, & Wen, ), higher first branches (Liu & Zhao, ; Li et al, ), and crowns without lianas (Barnett, Shaw, Spironello, MacLarnon, & Ross, ; Fei et al, ; Phoonjampa, Koenig, Borries, Gale, & Savini, ); (2) enhance their field of view to better monitor the surrounding environment, that is, less shrub cover (Hankerson et al, ), close proximity to riverbanks (Bernard, Matsuda, Hanya, & Ahmad, ; Thiry et al, ); (3) provide escape routes by utilizing arboreal connectivity between surrounding trees (Bernard et al, ; Fan & Jiang, ; Hankerson et al, ); (4) shelter from extreme climatic conditions in both tropical and temperate habitats, that is, utilizing dense canopies (Cui et al, ; Xiang, Nie, Chang, Wei, & Ming, ); palm trees and tree hollows (Heymann, ). Sleeping site and tree selection can also be influenced by other factors, for example, group size (Anderson, ; Bitetti et al, ) and to minimize parasitic infections (Feilen & Marshall, ).…”