Elsevier

Hormones and Behavior

Volume 93, July 2017, Pages 118-127
Hormones and Behavior

Endocrine differences among colour morphs in a lizard with alternative behavioural strategies

https://doi.org/10.1016/j.yhbeh.2017.05.001Get rights and content

Highlights

  • We compared circulating androgen, corticosterone and bite force of colour morphs.

  • The most aggressive orange morph had the highest levels of baseline androgen.

  • After stress, the orange and orange-yellow morphs retained high androgen.

  • Stress increased androgen in the least aggressive morphs (yellow and grey).

Abstract

Alternative behavioural strategies of colour morphs are expected to associate with endocrine differences and to correspond to differences in physical performance (e.g. movement speed, bite force in lizards); yet the nature of correlated physiological and performance traits in colour polymorphic species varies widely. Colour morphs of male tawny dragon lizards Ctenophorus decresii have previously been found to differ in aggressive and anti-predator behaviours. We tested whether known behavioural differences correspond to differences in circulating baseline and post-capture stress levels of androgen and corticosterone, as well as bite force (an indicator of aggressive performance) and field body temperature. Immediately after capture, the aggressive orange morph had higher circulating androgen than the grey morph or the yellow morph. Furthermore, the orange morph maintained high androgen following acute stress (30 min of capture); whereas androgen increased in the grey and yellow morphs. This may reflect the previously defined behavioural differences among morphs as the aggressive response of the yellow morph is conditional on the colour of the competitor and the grey morph shows consistently low aggression. In contrast, all morphs showed an increase in corticosterone concentration after capture stress and morphs did not differ in levels of corticosterone stress magnitude (CSM). Morphs did not differ in size- and temperature-corrected bite force but did in body temperature at capture. Differences in circulating androgen and body temperature are consistent with morph-specific behavioural strategies in C. decresii but our results indicate a complex relationship between hormones, behaviour, temperature and bite force within and between colour morphs.

Section snippets

Study species

The tawny dragon lizard, C. decresii, is a small, sexually dimorphic agamid lizard found on rocky outcrops of Kangaroo Island, Mt. Lofty Ranges and southern Flinders Ranges of South Australia (Houston, 1974). Males exhibit striking throat colour variation both within and between populations (Houston, 1998). In populations in the Flinders Ranges, males occur in four distinct throat colour morphs: orange, yellow, grey and orange-yellow, which can be objectively classified, independently of the

Factors affecting hormone concentrations

Morphs did not differ in most traits that could influence hormones concentrations. There were no differences between morphs in SVL (F3,112 = 1.74, p = 0.162, η2 = 0.03), the time of day at capture (F3,138 = 2.24, p = 0.086, η2 = 0.06) or the time it took to capture a lizard (F3,139 = 2.52, p = 0.061, η2 = 0.04); however there was a difference between morphs in their body temperature at capture (F3,154 = 4.19, p = 0.007, η2 = 0.15; Fig. 2) with the orange-yellow morph having a higher body temperature than the yellow

Discussion

We predicted that the behavioural strategies of C. decresii colour morphs would be reflected by differences in androgen and corticosterone concentration as well as bite force. All morphs showed a similar increase in corticosterone concentration in response to acute capture stress and did not differ in their adrenal stress response, measured as CSM. However, morphs did differ in baseline levels of androgen, with the orange, more aggressive morph having significantly higher concentrations of

Conclusions

Here we have shown that colour morphs of C. decresii differ in levels of androgen immediately after capture and following acute stress but do not differ in concentration of corticosterone, CSM or bite force. Our findings appear consistent with previously established behavioural differences of morphs (Yewers et al., 2016). The orange morph shows consistently high aggression and has a higher concentration of androgen immediately after capture than the grey or yellow morphs, and maintains high

Acknowledgements

We thank Sarah Pryke, Nina Svendin and Kristal Cain for help with hormone assays at the Australian National University. We are grateful for the field work assistance of Rachael Bartlett, Enrique Cruz, Fran Lyndon-Gee, Sarah Grogan, Jessica Hacking, David Hamilton, Jennifer Hetz, Molly Hunter, Claire McLean, Adnan Moussalli, Montse Sutulov, Tim Tan, Luisa Teasdale, Bryant Turffs and Peter Yewers. This work was funded by the Australian Research Council (DP1092908) to D.S-F., the Nature Foundation

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