Individual variation in nest size and nest site features of the Bornean orangutans (Pongo pygmaeus)

Abstract

Nest construction is a daily habit of independent orangutans for sleeping or resting. Data on their nests have been used in various ecological studies (e.g., density estimation, ranging behavior, evolution of material culture) because they are the most observable field signs. We investigated nest size and nest site features of Bornean orangutans in the wild during 10 months' fieldwork at three sites in East Kalimantan, Indonesia: Kutai National Park, Birawa, and Meratus. To examine individual variation, we followed 31 individual orangutans and recorded the 92 nests they made for nest size (diameter) and nest site features (height of nest above ground, tree species used for the nest site, the diameter and height of the tree, whether the nest was new or reused, and nest location within the tree). Analyses taking age-sex classes of the focal individuals into consideration showed significant age-sex differences in nest size and location, but not in nest height or nest tree features (diameter, height of tree, and height of lowest branch). Mature orangutans (adult females, unflanged and flanged males) made larger nests than immatures (juveniles and adolescents). Flanged male orangutans with larger nests used stable locations for nesting sites and reused old nests more frequently than immatures. The overall proportion of nests in open (exposed) locations was higher than in closed (sheltered) locations. Flanged males and immatures frequently made open nests, whereas adult females with an infant preferred closed locations. The good correspondence between nest size and age-sex classes indicates that nest size variation may reflect body size and therefore age-sex variation in the population.

Nesting Ecology of a Small Montane Population of the Nigerian/Cameroon Chimpanzee (Pan troglodytes ellioti) in Nigeria

“…This suggests that within NNFR, chimpanzees are wary of predators due to either historical or current threats, or most likely a combination of both. Nest height has been found to increase in response to predation [Rayadin and Saitoh, 2009], which implies that choosing to build nests in smaller than average trees, which are theoretically more accessible to all predators, is a trade-off between escape from predators by nesting in large trees, the advantages of nesting on steep slopes to avoid disturbance and see who is coming, and other factors such as quality of sleep.…”

Pre-Sleep and Sleeping Platform Construction Behavior in Captive Orangutans (Pongo spp.): Implications for Ape Health and Welfare

“…Day sleeping platforms are similar in function for chimpanzees, bonobos and orangutans and serve as quickly constructed rest points throughout the day (Brownlow et al 2001;Ancrenaz et al, 2004). Mature orangutans (unflanged and flanged males and females) have been observed making larger sleeping platforms than immatures (Rayadin and Saitoh, 2009). Both flanged and immature males frequently make open, exposed sleeping platforms, whereas parous adult females prefer sheltered, closed sleep sites (Rayadin and Saitoh 2009).…”

“…Mature orangutans (unflanged and flanged males and females) have been observed making larger sleeping platforms than immatures (Rayadin and Saitoh, 2009). Both flanged and immature males frequently make open, exposed sleeping platforms, whereas parous adult females prefer sheltered, closed sleep sites (Rayadin and Saitoh 2009). …”

“…Systematic behavioral and mechanical studies on wild orangutan sleeping platform construction have increased our understanding of wild great ape sleep ecology [Russon, 2007;Rayadin and Saitoh, 2009;van Casteren et al, 2012van Casteren et al, , 2013], yet no such counterpart for captive studies has been published to date. The goal of this study was to provide a more systematic characterization of captive ape sleep-related behavior by documenting pre-sleep (i.e.…”

Kin, Daytime Associations, or Preferred Sleeping Sites? Factors Influencing Sleep Site Selection in Captive Chimpanzees (Pan troglodytes)

“…With the exception of the typically more solitary orang-utan [Rayadin and Saitoh, 2009], wild great apes generally sleep socially, with some degree of species specificity in nesting groups [Fruth and Hohmann, 1996]. For instance, gorilla groups remain intact when they make their night nests, whereas bonobo daytime parties ('unit groups') often congregate to form larger nesting parties [Fruth and Hohmann, 1996;Mulavwa et al, 2010].…”