Anole Annals

Writing in Biology Letters recently, Alex Gunderson (Tulane University) leads a study revealing that incubation temperature does not underlie the thermal tolerance limits of resulting lizards; individuals which hatch from eggs incubated in hot conditions are not able to withstand hotter air temperatures as adults, relative to lizards hatched from cooler incubation temperatures. A preliminary discussion of the relationship between incubation conditions and adult thermal physiology was put forward as a potential explanation for observed divergence in thermal physiology between crested anoles (A. cristatellus) in Puerto Rico and an introduced population in Miami, Florida USA (Leal & Gunderson 2012), “Additional studies are needed to explore the possibility that incubation temperature can influence the [thermal tolerance limits] CTmin of A. cristatellus.” Below is the abstract and the main figure from the paper, enjoy!

Abstract
Extreme heat events are becoming more common as a result of anthropogenic global change. Developmental plasticity in physiological thermal limits could help mitigate the consequences of thermal extremes, but data on the effects of early temperature exposure on thermal limits later in life are rare, especially for vertebrate ectotherms. We conducted an experiment that to our knowledge is the first to isolate the effect of egg (i.e. embryonic) thermal conditions on adult heat tolerance in a reptile. Eggs of the lizard Anolis sagrei were incubated under one of three fluctuating thermal regimes that mimicked natural nest environments and differed in mean and maximum temperatures. After emergence, all hatchlings were raised under common garden conditions until reproductive maturity, at which point heat tolerance was measured. Egg mortality was highest in the warmest treatment, and hatchlings from the warmest treatment tended to have greater mortality than those from the cooler treatments. Despite evidence that incubation temperatures were stressful, we found no evidence that incubation treatment influenced adult heat tolerance. Our results are consistent with a low capacity for organisms to increase their physiological heat tolerance via plasticity, and emphasize the importance of behavioural and evolutionary processes as mechanisms of resilience to extreme heat.

Eggs at different temperatures did not produce adults capable of tolerating different temperatures. Here, Fig 1. shows the upper limits of heat tolerance of adult brown anoles (A. sagrei) hatched from eggs incubated under different thermal treatments.

Leal, M. and Gunderson, A.R., 2012. Rapid change in the thermal tolerance of a tropical lizard. The American Naturalist, 180(6), pp.815-822.
Gunderson, A.R., Fargevieille, A. and Warner, D.A., 2020. Egg incubation temperature does not influence adult heat tolerance in the lizard Anolis sagrei. Biology Letters, 16(1), p.20190716.

In reporting a case of tail bifurcation in a Bahamian brown anole (A. sagrei) from south Eluethera, Sebastian Hoefer and Nathan Robinson (The Cape Eleuthera Island School), write in Herpetology Notes proposing so!

“Another interesting observation was that this individual was particularly easy to capture and did not attempt to escape. The lack of avoidance could be explained by the anole being stunned due to stress at the time of capture. Alternatively, it could be that multiple tails infer higher energetic costs than a single tail. In turn, this could negatively affect the individual’s activity patterns or ability to avoid predators.”

Hoefer, S. and Robinson, N.J., 2020. Tail bifurcation in a Brown Anole, Anolis sagrei (Duméril & Bibron, 1837). Herpetology Notes, 13, pp.333-335.

Two anoles duking it out. Photo from sciencesource.com

Give the elaborate and charistmatic behaviours of our favourite lizards — anoles — many researchers have attempted to piece apart the intricacies of anole social dynamics. In a recent study in Zoology, Glenn Borgmans (University of Antwerp) tests whether dominant adult male American green anoles (A. carolinensis) – dominant in relation to other males – are actually at an advantage, for example by establishing priority access to food or other resources, or if risks associated with being the big boss in town outweigh any perceived benefits, like an increased likelihood of injury due to aggressive male-male interactions. You can read all about it here!

Abstract
Male Anolis carolinensis lizards will fight and form social dominance hierarchies when placed in habitats with limited resources. Dominance may procure benefits such as priority access to food, shelter or partners, but may also come with costs, such as a higher risk of injuries due to aggressive interaction, a higher risk of predation or a higher energetic cost, all of which may lead to an increase in stress. While most research looks at dominance by using dyadic interactions, in our study we investigated the effect of dominance in a multiple male group of A. carolinensis lizards. Our results showed that dominant males in a multiple male group had priority access to prey and potential sexual partners but may run a higher risk of predation. We could not confirm that dominant males in a multiple male group had a higher risk of injuries from aggressive interactions or a higher energetic cost by being dominant. Overall our results seem to indicate that dominant male A. carolinensis lizards in a multiple male group obtain clear benefits and that they outweigh the disadvantages.

Dominant lizards ate more food items (left; A) and hid less (right; B) than more submissive individuals.

Borgmans, G., Van den Panhuyzen, S. and Van Damme, R., 2020. The (dis) advantages of dominance in a multiple male group of Anolis carolinensis lizards. Zoology, 139, p.125747.

They do! Rodríguez-Cabrera and colleagues report in the latest issue of Euscorpius: Occasional Papers in Scorpiology on predation on scorpions in Cuba. In addition to the A. homolechis and A. sagrei shown above (left and right, respectively), A. equestris was also observed eating a scorpion.