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Thesis Abstract – Saftler (2008)


Is the Foraging Success of Sceloporus occidentalis Related to Seasonal Variation in Prey Availability and Locomotor Performance?

Author and college:

Shayni Saftler, Harvey Mudd College


April 30, 2008


Bachelor of Science in Biology


Stephen Adolph, Harvey Mudd College


The ecological diversity of lizards has been thoroughly studied, and in particular, foraging mode has received a great deal of attention. Many studies have pointed out interesting differences in locomotor performance related to foraging mode on a broad interspecific scale. Surprisingly, however, there is little data on the factors that influence individual variation in foraging success of lizards or any other animals. A number of physiological, morphological, behavioral, and ecological factors can potentially influence the foraging success of lizards. In this study I investigated the physiological and ecological factors affecting the foraging success of the Western fence lizard (Sceloporus occidentalis). Fence lizards are sit-and-wait, generalist insectivores. I predicted that (1) seasonal variation in the abundance of insects would affect the overall foraging success of fence lizards, (2) foraging success would be a repeatable measurement for fence lizards, and (3) locomotor performance would be a key factor affecting individual foraging success of fence lizards. To test these hypotheses, I captured fence lizards in the field, estimated foraging success from fecal production, and measured sprint speed as an estimate of locomotor performance. Estimated foraging success scaled with body mass0.739, while estimated locomotor performance scaled with body mass0.1. I found no significant correlation between seasonal variation in prey availability and overall foraging success or between locomotor performance and individual foraging success. The sample size of recaptured lizards was too small to accurately calculate the repeatability of foraging success; however, the available data from this study, as well as from another study on the consumption rate of crickets by fence lizards in the lab, suggest that fence lizards are individually consistent in their foraging success. Also, it appeared that lizards caught in the spring, when prey were most abundant and temperatures were hottest, consistently consumed more than enough energy to meet their daily demands. Ultimately, these results have interesting implications for the importance of environmental conditions in the foraging success of lizards, and suggest that there may not always be a link between locomotor performance and fitness.

For more information:

Contact Stephen Adolph – stephen_adolph@hmc.edu

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