One of the most interesting features of many lizards, including anoles, is that they can willingly, and actively, lose their tails to escape predators. While it might seem counterintuitive to lose a large body part, it’s better than being eaten! Despite the obvious benefit of surviving another day, there are some costs associated with tail autotomy.
Amy Payne, a student in Michele Johnson’s lab at Trinity University of San Antonio, wanted to know whether the frequency of tail loss across 7 species was associated with predatory and social use of the tail as well as energetic content of the tail. For those that anole-inclined (which is why you’re here), Amy included A. cristatellus and A. carolinensis. She caught and measured hundreds of lizards, and made behavioral observations on them as well. She was then able to quantify how many lizard of each species had a lost/regenerated tail, as well as what proportion of each tail was lost.
Surprisingly, frequency of tail loss was not associated with using the tail in a social or predatory context. However, using there was an association between these two functions of the tail: species that used their tail for predatory use more also used their tail in social contexts more. There was no relationship between the frequency of tail lost and the proportion of the tail that was lost on average across species. But she did find some really cool results when looking at energetic content of the tail. Amy found that there was a significant positive relationship between frequency of tail loss and tail energy content. That is, the more energy that lizards have in their tails, the more frequently individuals in that species will have a lost/regenerated tail. While this seems opposite to what one might casually predict, Amy hypothesizes that the predator-distraction to survive function of tail autotomy is more likely to succeed if the tail is larger and more beneficial to the predator. In other words, if a lizard has a scrawny tail and drops it off for a predator, it is more advantageous for the predator to ignore the low-cal tail and just eat the lizard. This would put selection on species with low-energy content tails to be more prudent about when they drop their tails. These really interesting results open up some exciting areas for future research on the costs and benefits of tail autotomy!