Tail Autotomy Is Associated with Boldness in Male but Not Female Water Anoles

Photo by Lindsey Swierk

Although most people use “personality” to describe human characteristics, animals also exhibit personality traits, which behavioral ecologists categorize as aggressiveness, exploration, activity, sociability, and boldness. Each personality trait is linked to inherent trade-offs that could affect one’s overall fitness, and may differ between the sexes due to different life history strategies. Boldness is a personality trait that includes behaviors such as risk-taking, response to predators, and resistance to being handled. It is assumed that bolder individuals are more likely to “take chances” and forage under predation risk compared to less bold individuals, whereas less bold individuals may spend more time scanning for predators and less time foraging.

Austin Carriere (The University of Oklahoma), Dr. Lindsey Swierk (Binghamton University – SUNY), Dr. Bree Putman (California State University San Bernardino) and I investigated the sex differences in the trade-offs between boldness and predator avoidance in water anoles (Anolis aquaticus), using the voluntary shedding of the tail (tail autotomy) as a proxy for predation risk. This project involved a two-year mark-recapture study, morphological data collection, and behavioral trials. We conducted and recorded boldness trials in the field for all captured adult anoles, and we analyzed the video footage in the lab. We quantified boldness as the latency for a lizard’s head to emerge from a refuge into a novel environment.

Fig 1. Adjusted survival curves showing how tail break (yes or no) affected time to head estimated from the Cox proportional hazard model in a) female and b) male water anoles. Survival rate is the proportion of individuals still in the refuge.

We found that there were sex-differences in the costs of boldness, as tail autotomy was positively associated with boldness in males but not in females. Tail autotomy has been shown to have serious fitness consequences in lizards; therefore males likely suffer a higher cost of boldness. We also found that males tended to be more likely to show evidence of tail autotomy. Our results could be due to the fact that lizards exhibit a polygynous mating system, wherein males defend territories to acquire mates, and so males may exhibit bolder behavior to increase their reproductive success. However, the trade-off of boldness in males is the higher probability of tail autotomy, probably due to increased exposure to predators or more involvement in aggressive encounters with conspecifics. Our study contributes to the understanding of sex differences in behavior within an ecological context.

Source: Talavera, J.B., Carriere, A., Swierk, L., Putman B.J. Tail autotomy is associated with boldness in male but not female water anoles. Behav Ecol Sociobiol 75, 44 (2021). https://doi.org/10.1007/s00265-021-02982-w