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The Ontogeny of Gap Crossing Behaviour in Bornean Orangutans (Pongo pygmaeus wurmbii).

Chappell J, Phillips AC, van Noordwijk MA, Mitra Setia T, Thorpe SK - PLoS ONE (2015)

Bottom Line: Our results suggest that gap crossing varies with both physical and cognitive development.Smaller individuals also crossed disproportionately large gaps relative to their size, by using support deformation.Our results suggest that orangutans acquire the full repertoire of gap crossing techniques, including the more cognitively demanding ones, before weaning, but adjust the frequency of the use of these techniques to their increasing body size.

View Article: PubMed Central - PubMed

Affiliation: School of Biosciences, University of Birmingham, Birmingham, United Kingdom.

ABSTRACT
For orangutans, the largest predominantly arboreal primates, discontinuous canopy presents a particular challenge. The shortest gaps between trees lie between thin peripheral branches, which offer the least stability to large animals. The affordances of the forest canopy experienced by orangutans of different ages however, must vary substantially as adult males are an order of magnitude larger in size than infants during the early stages of locomotor independence. Orangutans have developed a diverse range of locomotor behaviour to cross gaps between trees, which vary in their physical and cognitive demands. The aims of this study were to examine the ontogeny of orangutan gap crossing behaviours and to determine which factors influence the distance orangutans crossed. A non-invasive photographic technique was used to quantify forearm length as a measure of body size. We also recorded locomotor behaviour, support use and the distance crossed between trees. Our results suggest that gap crossing varies with both physical and cognitive development. More complex locomotor behaviours, which utilized compliant trunks and lianas, were used to cross the largest gaps, but these peaked in frequency much earlier than expected, between the ages of 4 and 5 years old, which probably reflects play behaviour to perfect locomotor techniques. Smaller individuals also crossed disproportionately large gaps relative to their size, by using support deformation. Our results suggest that orangutans acquire the full repertoire of gap crossing techniques, including the more cognitively demanding ones, before weaning, but adjust the frequency of the use of these techniques to their increasing body size.

No MeSH data available.


Related in: MedlinePlus

Frequency (per observation day) of three categories of take-off support, for different ages of orangutans.AF = adult females (Juni and Kerry), AM = adult males (Gismo and Preman).
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pone.0130291.g004: Frequency (per observation day) of three categories of take-off support, for different ages of orangutans.AF = adult females (Juni and Kerry), AM = adult males (Gismo and Preman).

Mentions: Different age-classes of orangutans also appeared to differ in their choice of takeoff support while crossing gaps (see Fig 4 and Table 2). In this study use of lianas was at a relatively low frequency for individuals of all ages, but is lowest for the youngest and oldest individuals. The most striking trend is the increase in frequency of use of trunks with age, and the corresponding decrease in frequency of use of branches. A Pearson chi-squared test showed that frequency of use of take-off supports with age differed significantly from the expected distribution (Chi-sq = 144.76, df. = 18, p<0.0001). Inspection of the standardized cell residuals showed that individuals aged 1–4 years old used branches more frequently than expected and trunks less frequently than expected, while this pattern was reversed for adult females and males.


The Ontogeny of Gap Crossing Behaviour in Bornean Orangutans (Pongo pygmaeus wurmbii).

Chappell J, Phillips AC, van Noordwijk MA, Mitra Setia T, Thorpe SK - PLoS ONE (2015)

Frequency (per observation day) of three categories of take-off support, for different ages of orangutans.AF = adult females (Juni and Kerry), AM = adult males (Gismo and Preman).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4495978&req=5

pone.0130291.g004: Frequency (per observation day) of three categories of take-off support, for different ages of orangutans.AF = adult females (Juni and Kerry), AM = adult males (Gismo and Preman).
Mentions: Different age-classes of orangutans also appeared to differ in their choice of takeoff support while crossing gaps (see Fig 4 and Table 2). In this study use of lianas was at a relatively low frequency for individuals of all ages, but is lowest for the youngest and oldest individuals. The most striking trend is the increase in frequency of use of trunks with age, and the corresponding decrease in frequency of use of branches. A Pearson chi-squared test showed that frequency of use of take-off supports with age differed significantly from the expected distribution (Chi-sq = 144.76, df. = 18, p<0.0001). Inspection of the standardized cell residuals showed that individuals aged 1–4 years old used branches more frequently than expected and trunks less frequently than expected, while this pattern was reversed for adult females and males.

Bottom Line: Our results suggest that gap crossing varies with both physical and cognitive development.Smaller individuals also crossed disproportionately large gaps relative to their size, by using support deformation.Our results suggest that orangutans acquire the full repertoire of gap crossing techniques, including the more cognitively demanding ones, before weaning, but adjust the frequency of the use of these techniques to their increasing body size.

View Article: PubMed Central - PubMed

Affiliation: School of Biosciences, University of Birmingham, Birmingham, United Kingdom.

ABSTRACT
For orangutans, the largest predominantly arboreal primates, discontinuous canopy presents a particular challenge. The shortest gaps between trees lie between thin peripheral branches, which offer the least stability to large animals. The affordances of the forest canopy experienced by orangutans of different ages however, must vary substantially as adult males are an order of magnitude larger in size than infants during the early stages of locomotor independence. Orangutans have developed a diverse range of locomotor behaviour to cross gaps between trees, which vary in their physical and cognitive demands. The aims of this study were to examine the ontogeny of orangutan gap crossing behaviours and to determine which factors influence the distance orangutans crossed. A non-invasive photographic technique was used to quantify forearm length as a measure of body size. We also recorded locomotor behaviour, support use and the distance crossed between trees. Our results suggest that gap crossing varies with both physical and cognitive development. More complex locomotor behaviours, which utilized compliant trunks and lianas, were used to cross the largest gaps, but these peaked in frequency much earlier than expected, between the ages of 4 and 5 years old, which probably reflects play behaviour to perfect locomotor techniques. Smaller individuals also crossed disproportionately large gaps relative to their size, by using support deformation. Our results suggest that orangutans acquire the full repertoire of gap crossing techniques, including the more cognitively demanding ones, before weaning, but adjust the frequency of the use of these techniques to their increasing body size.

No MeSH data available.


Related in: MedlinePlus