Body Condition, Hatchling Sex Identification, and Somatic Growth of the Mojave Desert Tortoise, Gopherus agassizii
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Authors
Walden, Margarete
Issue Date
2022
Type
Dissertation
Language
Keywords
Alternative Title
Abstract
The Mojave desert tortoise, Gopherus agassizii, has been experiencing sustained population declines across most of its range in the last 50 years. While some current threats to population persistence are known, such as habitat fragmentation and wildfires, whether this species is vulnerable to or resilient to climate warming is poorly understood. As a wide-ranging herbivorous reptile inhabiting large areas of public lands in the desert Southwest, land managers are increasingly concerned with identifying areas of its range where populations will be able to persist into the next century so as to prioritize conservation efforts. This species performs an essential ecological role as an ecosystem engineer that burrows into the soil and creates refugia for numerous species such as the burrowing owl that does not construct its own burrows. The Mojave desert tortoise inhabits desert valleys where increasingly, large-scale renewable energy installations, transportation infrastructure, and suburban expansion are occurring. To address conservation concerns, it is necessary to identify climate drivers of population vital rates in order to predict population dynamics on the landscape under future climate change scenarios. In this dissertation, I investigate body condition and fat storage as potential indicators of individual fitness. I validate a method to identify sex of day-old hatchlings so as to understand the effect of climate on sex ratios in wild nests. Finally, I predict how somatic growth rate and asymptotic body size, two important predictors of fecundity, will likely change in the second half of the twenty-first century. The findings of this dissertation will assist population modeling efforts and continued research into ensuring population persistence of this important desert reptile.