Science

Thermal constraints on chameleon feeding

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Thermal constraints on chameleon feeding performance: contrasting species along an environmental temperature gradient

***UPDATE***: I've now surpassed my goal but I can still use additional donations! All additional funds received will be be used to expand this project to include comparison to other species of different genera from other countries! Thank you everyone who has contributed so far!

Background

For my doctoral dissertation research under Stephen Deban at the University of South Florida’s Department of Integrative Biology, I have been studying the effect of temperature on feeding in chameleons. Elastic recoil projects a chameleon’s tongue with extremely high performance, while tongue retraction is powered by muscle contraction directly. The contrasting mechanisms of tongue projection and retraction provide a control as well as a comparison between an elastic recoil powered and muscle-powered movement during each feeding event. We’ve discovered that while this elastic recoil mechanism minimizes the thermal dependence of tongue projection, tongue retraction exhibits strong thermal dependence. This allows chameleons to project their tongues with explosive performance, even at temperatures that see sympatric lizards remaining inactive as they are unable to capture prey at such a low body temperature.

Previous research has shown that both adaptation and acclimation to low muscle temperature in species from cold environments are known to mitigate thermal effects in muscle-powered movements at low temperature. However, because low thermal dependence results in a wider thermal performance breadth, natural selection might act differently on movement types that benefit from lower thermal dependence (i.e. elastic recoil powered movements) than it would on movement types that experience higher thermal dependence (i.e. muscle-powered movements).

What I want to do

I want to travel to South Africa to work with Krystal Tolley from the South African National Biodiversity Institute to examine how temperature effects elastic recoil powered movements as opposed to muscle-powered movements in South African dwarf chameleons (Bradypodion sp.). Filming feeding sequences at multiple body temperatures from five key Bradypodion taxa, I will be able to look at thermal effects on feeding performance in species from both hot and cold habitats, as well as species exhibiting both a year-round activity pattern and a period of winter torpor.

Why travel to South Africa?

Because Bradypodion are restricted from export, collecting them under provincial permits and conducting this research in South Africa is more feasible than attempting to export them and conduct this research in the US. Further, this allows for collaboration with local expertise and for the opportunity to collect specimens under temporary capture permits and subsequently return said specimens to their collection site.

What will this research tell us?

We expect to find that tongue retraction performance will be optimized to different temperatures depending on the thermal environment each species is found in while tongue projection performance will not be optimized or optimized to a much lower degree. The results of this research will provide insight into how selection pressure impacts elastic recoil powered movements (tongue projection) as compared to muscle-powered movements (tongue retraction). Further, it will help us understand how animals incorporating elastic recoil powered movements cope with environmental constraints and how the thermal dependence of performance traits for these movement types impact the biogeography and survival of these species. Finally, this research will add to our body of knowledge on how chameleons (and other organisms) may adapt to climatic shifts, and/or how their current distributions may be affected in the future. All this will be done without needing to permanently remove specimens from their natural habitat.

How will the final information be used?

We expect that the results of this research will be presented in talks at scientific conferences, will be written up in an article for a peer reviewed scientific journal, and will be included in the final chapter of my doctoral dissertation.

Is this research feasible from a funding and permitting perspective?

Yes, this research is definitely feasible. Our research has already been approved by the Ethics Committee at the South African National Biodiversity Institute and by the Institutional Animal Care and Use Committee at the University of South Florida. Further, our research permits have already been submitted to the provincial authorities and we expect no problem with their issuance. Finally, partial funding for travel and accommodation expenses for this project has already been obtained and additional funding applications for the remainder of travel and accommodation expenses have been submitted. I just need a few more donations for other costs to make this project a reality.

What will funds be used for?

Donations will help pay for temporary housing setups for up to 30 specimens at a time while they are being filmed feeding at a range of body temperatures, for LED light panels needed for filming, and for travellers insurance for the high-speed camera. Whether I meet or fall short or our goal, those funds will be used to study temperature effects of feeding in dwarf chameleons in South Africa. If I raise more than 100% of our goal, the additional money will be used to expand this project to include comparison to other species of different genera from other countries! RocketHub is not an investment or charity – you fuel our project, I provide you with rewards. Every contribution at any amount will help and thank you for supporting my research!