Getting a grip on microhabitat use and ecological performance in the chameleon Furcifer oustaleti

Clark, Ryan M. (2019) Getting a grip on microhabitat use and ecological performance in the chameleon Furcifer oustaleti. MSc(Res) thesis, University of Nottingham.

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Aim: Identifying associations between phenotype and habitat use can elucidate how species have adapted to different local environments. Organism performance capacities are key functional links between morphology and habitat use. Yet, the idea that performance is optimised in specific environmental conditions remains an untested assumption for most habitats. This paucity of data connecting environment to individuals and their functional capacities hinders attempts to build fuller understanding of adaptive systems. With this in mind, I examined chameleon optimal grip performance and tested for relationships with microhabitat use and availability.

Location: Mahamavo forest region, northwest Madagascar.

Methods: Furcifer oustaleti were captured in the wild during diurnal surveys in June and July of 2017 and the diameter of their perch was measured. Random surveys were also used to determine the empirical distribution of available perch diameters in my research area. Individual grip strength was measured on wooden dowels of varying diameter. Grip strength was modelled as a hump-shaped function of dowel diameter to determine the optimum grip diameter for each chameleon. I used the empirical distribution of available perches to test whether chameleons perched closer to their optimum than expected if perch selection was random. I also tested whether individual grip optima were closer to the mode of the available perch diameter distribution than expected due to chance.

Results: Seven individuals showed grip optima within the range of dowel diameters tested, while five had the tightest grip on the smallest diameter tested. Larger, heavier chameleons with longer limbs had greater average grip strength, but did not select wider perches or have higher optimal grip diameters. Chameleons selected perches significantly wider than available perches—suggesting non-random selection of microhabitat. However, selected perches were not closer to grip optima than expected if perching was random with respect to grip optima. Optimal diameters were closer to the mode of available perch diameters than expected by chance.

Main conclusions: My findings provide the first tentative evidence that chameleon optimal grip diameters are commensurate with modal available perches in their habitat. Which factors determine chameleon perch selection remains an open scientific question. Further research on these topics should seek to test these findings with a larger sample size and on a wider dowel diameter range. Explaining functional links between chameleon grip–performance and perch characteristics in other species and habitats on Madagascar may help build a fuller understanding of the effects of forest restructuring on their ecology, and inform practical conservation of Malagasy herpetofauna in general.

Item Type: Thesis (University of Nottingham only) (MSc(Res))
Supervisors: Algar, Adam
Field, Richard
Keywords: Ecology, microhabitat use, performance, lizard, chameleon
Subjects: Q Science > QH Natural history. Biology > QH540 Ecology
Q Science > QL Zoology > QL605 Chordates. Vertebrates
Faculties/Schools: UK Campuses > Faculty of Social Sciences, Law and Education > School of Geography
Item ID: 55885
Depositing User: Clark, Ryan
Date Deposited: 08 Apr 2019 12:58
Last Modified: 07 May 2020 13:47

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