Date of Award

5-2019

Document Type

Thesis open access

Department

Biology

First Advisor

Michele A. Johnson

Second Advisor

Kevin Livingstone

Third Advisor

David O. Ribble

Abstract

In many lizard species, the ability to autotomize (lose) the tail allows for immediate survival in the face of predation. However, tails are often used in communication and energy storage, and so tail autotomy can thus decrease an individual’s overall fitness. In this study, I examine this tradeoff in species that use the tail differently. I predict less frequent tail autotomy in species that use the tail for social display or energy storage, as a full tail is particularly valuable. In species that primarily display the tail in an anti-predatory context, I predict the frequency of tail loss will be higher, as the tail is made especially vulnerable to autotomization. I studied seven lizard species that vary in tail use: greater earless lizards (Cophosaurus texanus) and curly tail lizards (Leiocephalus carinatus) use tails frequently in display; Mediterranean house geckos (Hemidactylus frenatus) and crested anoles (Anolis cristatellus) use tails occasionally; and green anoles (Anolis carolinensus), Texas spiny lizards (Sceloporus olivaceus), and Texas spotted whiptails (Aspidoscelis gularis) almost never include tail movements in display. I observed lizards of each species in the field to quantify the use of the tail in social contexts, and performed predator simulation trials to quantify tail use in anti-predatory contexts. I calculated the energetic content of the tail using bomb calorimetry. I found that the frequency of tail autotomy varies from 20-60 % of individuals across the seven species, and lizards that use their tail in a social context also tend to do so in an anti-predatory context. Finally, I found that total energy content in the tail is positively associated with tail loss frequency across species. By studying lizard tail loss, we can better understand the evolutionary trade-offs involved in balancing the benefit of predator evasion with the cost of tail loss in social and energetic utility.

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