The degree to which non-human primate behaviour is lateralized, at individual or population levels, remains controversial and over the last century, the issue of brain lateralization in primates has been extensively researched and debated, yet no previous study has reported eye preference or head turning in great apes. This thesis examines three different expressions of hemispheric asymmetry in lateralized behaviours: hand preference for bipedal tool use, eye preference, and auditory laterality. It is reported that bipedalism induced the subjects to become more lateralized, but not in any particular direction. Instead, it appeared that subtle pre-existing lateral biases, to the right or left, were emphasized with increasing postural demands. Eye preference was assessed when animals looked through a hole, using one eye, at an empty box, a mirror, a picture of a dog, a rubber snake, food biscuits, bananas, a rubber duck and a video camera. Main effects of stimulus type were reported for direction of eye preference, number of looks, and looking duration, but not for strength of eye preference. A left-eye bias was found for viewing the rubber snake and a right eye bias was found for viewing the bananas. In addition, a significant shift in eye preference took place from the initial look to subsequent looks when viewing the snake. The results reported are not consistent with the literature for other primate studies. Lastly, auditory laterality was assessed using the Hauser and Andersson (1994) head turning paradigm. Chimpanzee and American crow calls were broadcast to subjects from 180° behind them and directional head turning was recorded. No difference in turning direction or latency was found. This lack of result was attributed to the methodology and underlying assumption that head turning is directly related to hemispheric asymmetries and not influenced by any other processes.

Several aspects of Orang-utan development were Followed from 7-63 weeks. Housing care and feeding are described. Deciduous, dentition and weight data are recorded, and compared with human and chimpanzee data. Physical development was in advance of Homo sapiens. Motor development was studied by (i) intercoordination of discrete limb/body movements. Ever-more complex behaviour stemmed from accretion or intercoordination of previously seen behaviour, or arose de novo, (ii) General motor development showed a gradual mastery of more complex actions, (iii) Gessel testing of motor development and comparison with other Hominoidea revealed this Orang-utan to be in advance of the human infant. Development was more similar to Gorilla than Chimpanzee, yet was in many respects more extended than the chimp. This is explained by the small Gorilla and Orang subject number, and variability within Primate species. Piagetian cognitive development was tested using a battery of sensorimotor tests. The Orang-utan was in advance of the human infant, except in the Stage VI Stick test, which was never achieved. An alternative to Piaget's explanation of certain sensorimotor behaviour is advanced. There was, generally, a shorter (though complete) sensorimotor period in the Orang. Contrary to human data, there was no synchronicity in achievement of the same stage over different tests. This is explained by the species' different ecological/evolutionary histories. A phylogenetic scale of Piagetian accomplishment is suggested. Visually directed grasping was achieved at 3 1/2 months, before H. sapiens, and after the chimpanzee. Several new grasping behaviours are described, many of Piaget's observations are confirmed, and several are not. Development of hand to mouth, visual following and visual-auditory coordination are charted.

The Critically Endangered Hainan gibbon (Nomascus hainanus) is the world’s rarest ape, with a single population of an estimated 25 individuals surviving in approximately 15 km² of suboptimal forest within Bawangling National Nature Reserve, Hainan, China. The existing biological evidence-base for the species is inadequate for conservation planning, precluding evaluation of appropriate recovery actions. I derived comprehensive new baseline data on Hainan gibbon ecology, behaviour and genetics to clarify the species’ biology and population status, and inform urgently required conservation management for the species. Rigorous re-evaluation of Hainan gibbon spatial requirements indicated the species’ home range is much smaller than previously estimated (c. 1.5 km²) and in line with closely related Nomascus species in similar ecological conditions. Molecular assessment of the genetic status of the surviving population within the context of the species’ historical genetic diversity revealed that the Hainan gibbon has suffered a significant decline in genetic diversity following its past population bottleneck. The current population also shows a high level of relatedness and male-biased offspring sex ratio. Predictive models examining reportedly ‘anomalous’ Hainan gibbon ecological and behavioural traits within a phylogenetic framework indicated that large, polygynous groups may be evolutionarily characteristic for the species, but home range requirements are influenced by both intrinsic factors and current extrinsic conditions. Finally, Population Viability Analysis demonstrated that the species is highly likely to become extinct in the near future without active management, and that multiple actions mitigating extrinsic threats, enhancing habitat carrying capacity and improving survivorship will be required to reduce extinction risk. Together, these findings suggest that landscape-level management actions and intensive manipulation of the population may be necessary to safeguard the future of the Hainan gibbon. This research also has wider implications for improved understanding of gibbon ecology and conservation of species of extreme rarity.

This thesis aimed to document the behavioural response of zoo-housed chimpanzee and gorilla groups, in Belfast Zoological Gardens, N. Ireland, to visitors. This aim was important, in light of previous research in the area that suggests animals, particularly primates, show behaviour indicative of anxiety in the presence of zoo visitors. However, there is little evidence to suggest that this finding can be extended to how chimpanzees and gorillas respond. Additionally, although in general evidence is in favour of a 'zoo visitors as a form of stress' hypothesis, there is support for two alternative hypotheses. Specifically, a few studies have revealed that zoo animals may behave with behaviour indicative of enrichment, while there is other support for a habituation hypothesis, that is, zoo visitors are of no consequence to the animals. Thus, this thesis developed appropriate ethograms for the two study species (chimpanzees and gorillas) and used them to document the behaviour of these animals during differing periods of visitor density. Opportunistic data collection was coupled with experimental manipulation to investigate behavioural changes in chimpanzees and gorillas in response to visitors. The results suggested that both groups responded to the presence of visitors, and subsequently ruled out a 'habituation to visitors' hypothesis. However, in general the thesis found that chimpanzees and gorillas differed in their response. Chimpanzees tended to show behaviour indicative of enrichment whereas gorillas exhibited behaviour indicative of stress. Although these results were in general supported throughout each experiment conducted in the thesis, more research is undoubtedly required to investigate how other primates, indeed animals how other animals, respond to visitors both at this zoo and others.

No description available.

The future survival of the orangutan is extremely uncertain; as hunting and deforestation continue to exert pressure on surviving populations, new threats such as climate change and potential disease transmission are emerging that may exacerbate an already critical situation. The potential impacts of these threats were investigated in this thesis using modelling approaches, to provide insights that will be valuable for planning effective conservation strategies. Anthropogenic factors were identified as important determinants of the current range of the orangutan, while resting time also appeared to be a key constraint on orangutan distribution patterns. This may be related to a greater reliance on fallback foods in degraded habitats, leading to increased digestion times and hence excessively high resting time demands. In the future, anthropogenic effects were predicted to continue to have an important influence on orangutans, particularly as they were found to be extremely sensitive to habitat degradation across the whole of their current range. In contrast, climate change was not predicted to be a major threat to the orangutan, although large increases in rainfall could lead to considerable range reductions. Abstract ii Modelling disease spread revealed that although potential superspreaders were identified in the orangutan population, the orangutan social system was extremely robust against disease transmission, irrespective of the model or disease parameters used. As such, vaccinations were not predicted to be useful. However, modelling disease transmission within a chimpanzee community suggested that orangutans living in a more gregarious manner, for example, in rehabilitation centres, may be highly susceptible to disease spread. Overall, although climate change and disease transmission were not predicted to be strong pressures, the extreme vulnerability of the orangutan to further habitat degradation across its range suggests that the development of even relatively minor threats could have important ramifications for the survival of the species.

No description available.

Orangutans are the only great ape to live an almost completely arboreal lifestyle, spending the majority of their time in the canopy of the tropical forest. The orangutans’ large size and habitual arboreal lifestyle means they are uniquely constrained by the mechanical properties of their canopy habitat. It is therefore necessary to have knowledge of the mechanics of trees and the wood material of which they are made in order to gain a greater understanding of orangutan ecology. This thesis begins with an investigation into the bending failure of three temperate tree species. Observations and electron microscopy of the fractures of hand bent branches were coupled with mechanical tests of the branch structures and the wood material. It was shown that the fracture mechanisms observed were related to the anatomy and consequent mechanical properties of the wood material. Light woods buckled due to their low transverse compressive strength, whilst denser woods tend to break in greenstick fracture, in which the fracture is diverted longitudinally at the midline, due to the low tangential tensile strength of the wood material. Three neotropical tree species were investigated in the same way and it was shown that all species tested failed in greenstick fracture with the modes of failure explained, at least in part by the differences in their wood anatomy and mechanical properties. These results were used to inform an investigation of orangutan nest architecture. The compliance of the nest structures was measured and the morphology, mechanical properties and modes of fracture of the nest elements were recorded. It was shown that nests were slightly more compliant where the orangutans’ weight was situated. Orangutans built the structural part of the nest by selecting, half breaking and weaving together thicker more rigid branches. However, the nest lining was generally made from completely detached narrower and less rigid branches. This suggests orangutans have a degree of technical knowledge, selecting the correct material for a certain construction role. In order to achieve a greater understanding of the mechanically complex canopy substrate that the orangutan inhabits, a study in to the mechanics of the canopy substrate was performed. Direct measurements of compliance and frequency of oscillation were taken from a range of tropical branches used by orangutans. It was shown that compliance increases dramatically towards the tip of branch and that branch diameter is the most effective branch morphological trait for predicting compliance levels. This study allowed a greater understanding of how these properties may affect orangutan ecology. To address whether conditions are present for energy storage and return during bouts of orangutan bipedalism, measurements of compliance and branch oscillation times were used in conjunction with analysis of video footage of orangutans. It was found that long step times of orangutans fall between the minimum and optimum step times for energy return, calculated from mechanical properties of bipedal supports. These results were supported by videos demonstrating in-phase branch movement and step kinematics. These results suggest that local diameter is the single most useful trait to predict the strength and rigidity of tropical branches, and their compliance and oscillatory frequency. This suggests that this is the cue used by the apes, and helps validate the assumptions made by previous researchers investigating arboreal primate locomotion. They also suggest that the conditions do exist in the natural environment that may facilitate energy storage and return on compliant branches during bipedal locomotion.

An animal’s locomotor abilities facilitate its interactions with the surrounding environment. Extant hominoids (apes) have evolved diverse ranges of locomotor strategies which allow them to exploit terrestrial and arboreal habitats despite their large body size. However, hominins (modern humans and their ancestors) are traditionally defined by their restriction to upright, bipedal posture and locomotion. Reconstructions of locomotor capacity in fossil hominoids allow investigation of the evolution of extant ape locomotion; yet these reconstructions rely on detailed understanding of the relationships between morphology, locomotor behaviour and the environment in extant apes. This thesis explores variation in locomotor behaviour and skeletal morphology among extant apes in order to shed light on these relationships. Studies of chimpanzees, gorillas and modern humans reveal considerable mechanical variation in gait, and demonstrate the importance of considering environmental context in ape locomotion. Anatomical studies find reduced reliability of inferring locomotor capacity in fossil hominoids due to significant variation among extant apes in skeletal predictors of habitual bipedality and estimations of joint range of motion. These studies highlight the importance of behavioural flexibility in determining hominoid locomotor capacity, and suggest that fossil hominoids were less constrained in their locomotor repertoires than previous reconstructions imply.