Eastern side blotched lizard

Uta stansburiana stejnegeri

Ecological and microevolutionary perspectives of tail autotomy in lizards

Antipredator traits often exhibit considerable variation among populations. As the level of antipredator responses should theoretically be fine-tuned to predation pressure, antipredator traits provide excellent opportunities to study the mechanisms that drive phenotypic variation among populations. Autotomy is a striking example of a widespread yet costly antipredator strategy that exhibits extensive geographic variation. Among all known cases of autotomy, tail autotomy in lizards represents probably the most common and best studied examples. Lizard populations can differ extensively in how readily autotomy would be induced. However, whether this variation is a product of selection remains unclear. Moreover, whether the variation in tail vertebral morphology has anything to do with the facility of autotomy is also unknown. My dissertation therefore aims to address the following two questions:

(1)Does tail vertebral morphology affect the facility of tail autotomy across lizard species?

(2)Do populations under different predation pressure differ in the facility of tail autotomy?

I am currently collecting data. Stay tuned!

Anolis gundlachi

Individual variation in locomotor recovery ability in tailless green anole lizards Anolis carolinensis

In a previous research by Gillis et al. (2009), they found that tailless green anoles (Anolis carolinensis) suffered from reduced in-air stability and, in some most extreme cases, disastrous landings. Since green anoles commonly autotomize their tails as a defense mechanism, we are interested in whether tailless green anoles are able to recover from lower in-air stability before their tails can regenerate substantially. Specifically, we would like to test whether locomotor recovery is facilitated with more locomotor experience and through time. To address this question, we used three treatment groups and monitored their in-air stability for five consecutive weeks. The first (control) group had intact tails and were subject to weekly jumping trials. The second group had their tails 80% removed and were subject to jumping trials only in the first and the last week. The third group also had their tails 80% removed and were subject to jumping trials weekly.

    Below is a figure showing the extent of in-air body rotation, a measure of in-air stability, in the three groups throughout the study period. Some individual did have the ability to improve in-air stability through time, whereas some individuals showed no sign of improvement. Interestingly, the acquisition of locomotor experience did not seem to matter. Our finding showed that some green anoles suffered from lower in-air stability for a prolonged period of time, which can have serious fitness consequences. How do green anoles compensate for lower in-air stability in nature (e.g., changes in habitat use and behavior) following tail loss would be the next question to ask.

C-Y Kuo, Gillis GB, Irschick DJ. 2012. Take this broken tail and learn to jump: the ability to recover from reduced in-air stability in tailless green anole lizards [Anolis carolinensis (Squamata: Dactyloidae)]. Biological Journal of the Linnean Society 107: 583-592  pdf

Loading effects on jump performance in green anole lizards

Many animals, including lizards, often have to move with additional burdens, mainly in the form of voluminous eggs/offspring or bulky food items. This is not an easy task as the weight gain can be up to 150% in some species! In one recent project, we studied the effect of such load-carrying on jump performance in a natural jumper: green anole lizard. Using artificial loads, we found that anoles cannot take off as fast and jump as far when they were loaded with an additional 30% of body mass, which was equivalent to the weight gain after a regular meal. The ability to land near the intended point, however, was not compromised. Our results suggest that a regular meal can pose a locomotor challenge for green anoles (Anolis carolinensis). Our next step would be to know how green anoles cope with this challenge. Will their movement pattern in the field change as a response to weight gain? Will they adopt different escape strategy if they are pursued by predators right after a meal? We hope to find the answers to these interesting questions in the near future.

C-Y Kuo, Gillis GB, Irschick DJ. 2011. Loading effect on jump performance in green anole lizards Anolis carolinensois. Journal of Experimental Biology 214: 2073-2079    pdf

The effects of tail loss on foraging and escape behaviors

The ability of actively shedding tails is common in lizards. In some species, 70% of the individuals in a population have once lost their original tails. Moving without a tail can have disadvantageous consequences, declined running speed or inability to jump properly, that result in higher vulnerability to predators. On the other hand, energy requirement tends to increase during tail regeneration, which likely leads to higher foraging activity levels.

    To understand the effect of tail loss on behaviors, we used yellow-chinned anole Anolis gundlachi in Puerto Rico as study species. We found that tailless lizards seemed to perch higher and moved significantly longer distances within our observation period, suggesting higher foraging effort. On the other hand, although tailless lizards did not change their timing of escape and did not flee further before stopping, they tended to run directly upwards without spiraling to the other side of the perch surface, which was observed more often in tailed lizards. We suspected that, instead of being more cryptic, the lizards increased their foraging effort to acquire more energy for tail regeneration in the face of low predation risk at our study site. More work is needed to clarify the role of ambient predation pressure in determining the outcome of behavioral change after tail loss.

Morphology and resource use of two agamid lizards

For my master’s thesis, I studied sexual dimorphism in two congeneric agamid lizards that co-occur in northern Taiwan. I also collected data on their resource use. It turned out that one species, Japalura swinhonis, are more sexually dimorphic than the other species, J. polygonata xanthostoma. Despite morphological differences, the two species occupied similar perch habitats and utilized the same set of food items. The two species might be competitors at my study site because subsequent observations showed that the population of J. polygonata xanthostoma was declining. It would be very interesting to elucidate the ecological relationship between the two species. Also, both species have conspicuous color patterns at their throat region. Those color patterns might serve as sexual signals, but no one really knows. I would like to unravel the function(s) of those color patches in the two agamid lizards.

C-Y Kuo, Y-T Lin, Y-S, Lin. 2009. Sexual size and shape dimorphism in an agamid lizard, Japalura swinhonis (Squamata: Iguania: Agamidae). Zoological Studies 48(3): 351-361 (cover)    pdf

C-Y Kuo, Y-S. Lin, Y. K. Lin. 2007. Resource use and morphology of two sympatric Japalura lizards (Iguania: Agamidae). Journal of Herpetology 41(4): 713-723    pdf

Japalura swinhonis

Japalura polygonata xanthostoma