A National Taiwan Normal University research team has published a paper on lizards’ autotomy rates, real predation pressures and the long-term cost of tail loss.
While it was suspected that caudal autotomy, or the self-amputation of the tail, is related to lizards’ survival, the relative lack of research of the action under natural conditions has been the main obstacle to verifying the theory, said the paper, published on Jan. 18 in the Proceedings of the Royal Society B journal.
The research team began a capture-mark-recapture (CMR) program in 2006 using the the sexually dichromatic Takydromus viridipunctatus, commonly known as the Formosan grass lizard, to compile an index, Lin said.
The team used the indices and a contemporary bird census mega-dataset of four predatory birds, based on Chinese Wild Bird Association data from 1970, as predictors to examine the association between tail loss and predation pressure, said Lin Jhan-wei (林展蔚), the lead author who is a doctoral student at the university’s Department of Life Science.
The team also estimated the survival cost of tail loss and alleviation by regeneration under natural conditions through CMR modeling, Lin said.
The researchers found that smaller birds, such as shrikes and kestrels, were the major cause of autotomy, while larger birds, such as the cattle egret, caused a depopulation of lizards, Lin said.
The survival rates of lizards after autotomy dropped to 20 to 30 percent compared with those that still had tails, Lin said, adding that after regeneration the mortality rates returned to a baseline, showing the relationship between the lizard’s tail and its survival.
“This study ... increases our understanding of the cost-benefit dynamics of caudal autotomy and further explains the maintenance of this trait as an evolutionarily beneficial adaption to long-term predator-prey interactions,” the paper said.
Lin said he would continue researching how the lizard’s tail facilitates its movement.
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