Tails of the City (out now in J. Herp.)

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Following up on my previous post about our work on caudal autotomy, I’m happy to share that our paper from undergraduate Kirsten Tyler’s senior honor’s thesis is out now (online) in Journal of Herpetology
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Kirsten analyzed the hundreds of X-rays I’ve taken of urban and natural anoles across Puerto Rico and found consistently higher frequency of caudal autotomy and regeneration in urban areas. With our current data, it is difficult to say whether differences in caudal autotomy are due to increased predation pressure, differences in predator communities, or reduced predator efficiency (or, likely, some combination of these).

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When the tail autotomizes it regrows as a solid rod of cartilage and not as distinct vertebrae. This is how we identified lizards with regenerated tails.

We know from the urban ecology literature that predator communities in urban areas are often very different from those in natural areas, both in abundance and composition. Urban communities are typically dominated by generalist (often non-native) predators like cats, raccoons, and dogs. We see this in Puerto Rico with respect to anoles. Although we do not present data on predator communities in this paper, in urban areas the predators tend to be grackle, dogs, cats, and humans. In contrast, in natural areas there are two anole specialist predators, the lizard cuckoo and Puerto Rican racer, as well as interspecific predation by larger species of anoles (e.g. Anolis cuvieri). It seems very probable that a specialized predator like a lizard cuckoo will leave far fewer escapees than a generalist urban predator like a cat, and so the higher rates of autotomy could simply indicate lower mortality following incidents with predators.

Of course, with shifts in predator communities comes shifts in predator efficiency, but also shifts in number of predation attempts possibly leading to elevated sub-lethal predation. The story is likely more complex still, but overall these results suggest that there is something different about lizard predation in urban areas. Future urban ecology research will help us understand exactly what that something is.

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Vicious urban predator in the background!

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