Branch flexibility (compliance) presents a major problem for arboreal animals that travel and feed in the forest canopy. Branches taper towards their ends, but the narrowest gaps between trees are situated between the thin terminal branches of adjacent tree crowns. In theory compliant terminal branches may act as external springs adding momentum to jumps and leaps across gaps, but most previous research has suggested that compliant supports increase the cost of arboreal locomotion. Alexander (1991) showed that monkeys lose energy during take off and landing as branches bend under their weight and jumping lemurs generally lose contact with branches before they recoil, expending energy to deform supports but failing to exploit the elastic energy to aid momentum (Demes et al., 1995).
However, gibbons have recently been demonstrated capable of adapting their leaping strategy when utilising compliant substrates, indicating that primates can limit the negative, energy sapping, effects of substrate compliance even when not utilising the substrate for energetic gain (Channon et al. 2011). Further, we have found that orangutans use the elastic compliance in arboreal supports to reduce the energetic cost of gap crossing (Thorpe et al, 2007). They use tree-sway (in which they oscillate compliant tree trunks with increasing magnitude to bridge a gap), which was found to be less than half as costly as jumping, and an order of magnitude less costly than descending the tree, walking to the next tree and climbing it. Our observations suggest that wild orangutans actually use support compliance in many aspects of their locomotor behaviour (Thorpe et al, 2009).
Clearly arboreal primates differ markedly in their response to branch compliance and such variability is likely to have been central to evolutionary radiations of the order (Cant, 1994). The purpose of this PhD is to study the ways in which sympatric arboreal animals respond to or utilise support compliance, both in the wild and in captivity (using specifically designed arboreal assault-courses). We are interested in the strategies that different animals utilise when dealing with compliance, and how these strategies impact on their general ecology. The exact study species will be finalised as the project develops, but should include primates, other mammals and/or birds. The project is likely to include 1) biomechanical studies of locomotion (e.g. kinematics, kinetics, accelerometry, thermal imaging) allied with 2) studies of the functional anatomy of the study species (muscle cross sectional area, fibre length, fibre typing); 3) behavioural observations of locomotion and support use (e.g. which supports are selected for different types of locomotion) and 4) basic mathematical modelling of locomotion to tease apart differences in body size and posture from actual differences in biomechanical strategy.
The successful candidate will be based in Dr Susannah Thorpe’s lab in the College of Life and Environmental Sciences at the University of Birmingham. The project is however in collaboration with Prof Robin Crompton (University of Liverpool) and Dr Anthony Channon (Royal Veterinary College, Herts). The student will therefore benefit from exposure to a wide variety of researchers, research fields and techniques.
Candidates must hold, or expect to hold, a very good honours degree (at least 2.1 or equivalent) in a relevant subject (e.g. Biology, Physical Anthropology, Biomechanics or Engineering), though a Masters degree is highly preferred. The position is likely to involve substantial fieldwork as well as lab and zoo-based studies in the UK. Field experience would therefore be beneficial. The student will receive considerable training, but should also be enthusiastic, self-motivated and be able to work independently.
Channon A. J. Günther M. M., Crompton R. H. and Vereecke E. E. (2009). Mechanical constraints on the functional morphology of the gibbon hind limb. Journal of Anatomy 215, (4):383-400.
Crompton R. H., Sellers W. I., Günther M. M. (1993). Energetic efficiency and ecology as selective factors in the saltatory adaptation of prosimian primates. Proceedings of the Royal Society
Thorpe S. K. S, Crompton R. H., Gunther M. M., Ker R. F. and Alexander R. M. (1999) Dimensions and moment arms of the hind- and forelimb muscles of common chimpanzees (Pan troglodytes). American Journal of Physical Anthropology 110, 179-199.
Thorpe S. K. S, Crompton R. H. and Alexander R. M. (2007). Orangutans utilize compliant branches to lower the energetic cost of locomotion. Biology Letters 3, 253-256.
Thorpe S. K. S., Holder R. L. and Crompton R. H. (2007b). Origin of human bipedalism as an adaptation for locomotion on flexible branches. Science 316, (5829):1328-1331.
Thorpe S. K. S., Holder R. and Crompton R. H. (2009). Orangutans employ unique strategies to control branch flexibility. Proceedings of the National Academy of Sciences 106, (31):12646-12651.
Further information is available on Dr Thorpe’s research interests (http://www.biosciences.bham.ac.uk/labs/thorpe/index.htm), Birmingham’s research environment (http://www.biosciences.bham.ac.uk/study/graduate/PhD.htm) or by contacting Dr Thorpe ([email protected]).
Applications should be submitted using the University of Birmingham on-line postgraduate application, details of which can be found at http://www.postgraduate.bham.ac.uk/apply. Applicants should indicate they are applying to the “PhD Biosciences” programme for research into “Strategies that minimise the costs of arboreal locomotion in primates and other animals”. They should ignore the question “Briefly describe your research interest…”, but instead write a 1-page summary describing their research interests in, and experience relevant to, the advertised position, and email this directly to Dr Thorpe.
Closing date for applications: applications are invited ASAP
Award start date: 1st October 2012.
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