Tail regeneration after autotomy revives survival: a case from a long-term monitored lizard population under avian predation

Abstract

Caudal autotomy in lizards has intrigued scientists for more than 100 years. Because of the relative lack of literature under natural conditions, the complicated association among field autotomy rate, real predation pressure, the long-term cost of tail loss, and the benefit of regeneration remains equivocal. In this study, we conducted a 7-year capture-mark-recapture (CMR) programme with a wild population of a sexually dichromatic lizard, Takydromus viridipunctatus We used autotomy indexes and a contemporary bird census mega-dataset of four predatory birds as predictors to examine the association between tail loss and predation pressure. We further estimated the survival cost of tail loss and alleviation by regeneration under natural conditions through CMR modelling. We found that large and small avian predators affect lizard survival through the following two routes: the larger-sized cattle egret causes direct mortality while the smaller shrikes and kestrels are the major causes of autotomy. Following autotomy, the survival rate of tailless individuals over the next month was significantly lower than that of tailed individuals, especially males during the breeding season, which showed a decline of greater than 30%. This sex-related difference further demonstrated the importance of reproductive costs for males in this sexually dichromatic species. However, the risk of mortality returned to baseline after the tails were fully grown. This study indicates the benefit of tail regeneration under natural conditions, which 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 ecology and evolution of autotomy

“…via regeneration or muscular compensation) or maintained over time (e.g. Lin et al, ). Since the costs of autotomy and regeneration have been thoroughly reviewed previously (Maginnis, ; Fleming et al, ; Bateman & Fleming, ; Higham et al, ), we aim here to build upon these previous reviews by summarizing new findings and novel approaches to studying the negative consequences of autotomy.…”

“…For instance, a seven‐year long mark–recapture study coupled with statistical modelling quantified the costs of autotomy on survival in a lizard ( Takydromus viridipunctatus ) population. Because of the study's design, these predatory pressures could be attributed to specific bird species (Lin et al, ). These new results provide a compelling and complete multi‐component approach to understanding the costs of autotomy.…”

What is known and what is not yet known about deflection of the point of a predator’s attack

“…During tail regeneration, digestive performance can also be affected, as protein income needs to be maximised (Sagonas et al 2017). However, despite initial costs of reduced survival rate associated with autotomy, tailless lizards' mortality risk does return to baseline following tail regrowth (Lin et al 2017). Apparent changes in feeding rate and digestive efficiency are again, though, inconsistent costs across autotomotizable reptiles and can depend somewhat on associated behavioural responses (Bateman & Fleming 2009).…”

Opsin gene expression regulated by testosterone level in a sexually dimorphic lizard

“…The East Asian Takydromus lizards, comprising about 20 species, present substantial variation in their courtship systems, even among closely related species 45 , 46 . Takydromus viridipunctatus might be the most well-studied species in this genus, and is commonly found in regions of northern Taiwan 47 . In grasslands of early succession stage, they sometimes form huge population size in high density.…”