Anole Annals

Brown anole eating a curly tail lizard. Photo by Joseph Wasilewski.

We’ve had a number of posts concerning predation by curly tail lizards on brown anoles, in the Bahamas, Florida, Cuba and elsewhere. Now comes a report from near Miami that the brownies aren’t just sitting back and taking it. Rather, they’re rounding up vigilante posses to track down and consume baby curlies, hitting the predator’s population where it’s vulnerable. Ok, perhaps that’s a stretch, but in a recent note in Herpetological Review, Krysko and Wasilewski publish the first report of Anolis sagrei preying on Leiocephalus carinatus, revealing that the ecological interactions between the two species are more complicated than previously thought: we already knew that curlies prey on brown anoles and that the two species also compete for some of the same insect prey (making this an example of the phenomenon of intra-guild predation),  but this study raises the possibility that the interaction–and its likely ecological and evolutionary consequences–could be substantially more complicated. One might think that because of the massive size advantage of the curly-tails, the effects must mostly be one-way; however, the massive population size differential between the two species means that brown anoles, in theory, could greatly affect curly tail populations as well. Although the effects of curly tails on brown anoles have been studied, the opposite experiment has not been done. Of course, previous work on tiny Bahamian islands indicates that curly tails substantially reduce brown anole populations, but maybe dynamics are different in larger and more complicated ecosystems. Personally, I wouldn’t bet on it, but who knows?

Battling green anoles. Photo from http://dmcleish.com/Maui2009/AnoleFight/DSC_0278.jpg

Both theory and empirical examples from many types of organisms indicate that animals alter their fighting behavior based on the outcome of previous fights. That is, if an animal won its previous fight, it is likely to win its next one, whereas previous losers are likely to keep on losing. In a new paper in Ethology, Garcia et al. examine whether such winner and loser effects occur in the green anole, A. carolinensis.

To create winners and losers independent of their innate fighting ability, the investigators first staged encounters in which one lizard was 40% larger than the other. Because size is a very good predictor of encounter outcome, they used this method to create animals which had won or lost their first encounter. Indeed, most of the larger animals won in these matches. Then, in the second round, they placed individuals of the same size together, one of which had won its previous encounter and the other that had lost.

Results did not support the hypothesis: probability of winning was not affected by previous experience: winners in the first round were no more likely to triumph in the second round than were first round losers. However, there was one interesting finding: losers that had put up a good fight in Round 1 were likely to win Round 2, whereas those who hadn’t continued to lose. Two possible explanations are either: 1) that the feisty losers were intrinsically more aggressive and couldn’t overcome the size disadvantage in Round 1, but when paired against similar-sized animals, were able to use their aggressiveness to overpower their opponent; or, second, that this is an example of a variation of the “loser effect,” only that it is not the outcome of the fight, but the quality of it, that matters. Losers who put up a good fight might still feel emboldened and thus do well in the future, whereas losers that lose badly may continue to lose in the future.
Mark J. Garcia, Laura Paiva, Michelle Lennox, Boopathy Sivaraman, Stephanie C. Wong, & Ryan L. Earley (2012). Assessment Strategies and the Effects of Fighting Experience on Future Contest Performance in the Green Anole (Anolis carolinensis) Ethology, 118, 821-834 DOI: 10.1111/j.1439-0310.2012.02072.x