Kirsten Tyler, a (recently graduated) undergraduate from UMass Boston, has spent the past few months working to better understand patterns of tail autotomy in urban populations of Anolis cristatellus (along with me and Liam Revell). We wanted to know if tail autotomy frequency differed between the urban and natural sites I have sampled over the past 3 years. Kirsten analyzed nearly every X-ray (almost 1000!) I have taken during my Ph.D. work here at UMass to determine the tail loss frequency and pattern (how many remaining vertebrae in autotomized tails) of urban and natural Anolis cristatellus. She was able to determine if lizards had autotomized tails because the tail regrows as a rod of cartilage instead of vertebrae — something easily seen on an X-ray. We anticipated that differences in predator composition in urban areas (e.g. more ground dwelling generalists such as cats) could lead to altered predation pressure or efficiency compared to nearby natural areas.
The results of Kirsten’s study are intriguing. We found that autotomy rates are higher in urban populations in all of the municipalities sampled. Averaged across all sites, 67.9% of lizards in urban sites and only 49.6% of lizards in natural sites had autotomized and regenerated tails. We also found that the amount of tail remaining differs between urban and natural sites, but that this effect was mediated by perch height (note: the poster below was completed with preliminary results). In general, lizards in urban areas retained more of their tails when they were captured on higher perches whereas the converse was true for natural lizards.
Kirsten presented her preliminary results in the poster shown below in partial fulfillment of her Honor’s research here at UMass. She is hoping to start graduate school this fall and I look forward to seeing more of her work. We have also submitted this research as a manuscript for publication. I’ll write a more thorough post about it when it is published!