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Timothy Revell (PhD, 2005)
"The behavioral ecology of sleep in the Desert Iguana (Dipsosaurus dorsalis)." |
Contact
Department of Biological Sciences
Mt. San Antonio College
1100 N. Grand Ave.
Walnut, CA 91789
Phone: (909) 594-5611, extension 4231
Email: trevell@mtsac.edu
Tim and one of his lovely Desert Iguanas (Dipsosaurus dorsalis). As much as Tim loves lizards, I couldn't help but notice the shirt he was wearing when this photo was taken. Yeah...who doesn't like rattlesnakes? Photograph: Mandy Revell.
A full-time professor at Mt. San Antonio College since 1999, Tim teaches Animal Behavior, Marine Biology, General Biology, Microbiology, and Anatomy. His strongest interests include behavioral ecology, herpetology, and ornithology. For his master's thesis, he studied the use of creosote bush and saltbush by arthropods in the East Mojave Desert. As a PhD student he earned his degree the difficult way--part-time while working a full-time job. Even so, he managed to finish in just four years. Amazing.
Tim chose to study a topic virtually no one has considered for reptiles--the functions and consequences of sleep. He research focused on the Desert Iguana, one of his favorite lizards (I can't blame him...a gorgeous creature!). He began by studying its sleep characteristics in the field and then tested specific hypotheses in the lab. The findings proved to be very interesting.
Dissertation abstract
Although sleep is commonly observed in many animals, the basic function that sleep serves remains unknown. Although many physiological studies have addressed sleep, research considering the ecological aspects of sleep has received less attention. In this dissertation, I examined the behavioral and ecological correlates of sleep in the Desert Iguana (Dipsosaurus dorsalis). First, I conducted a field study to determine location and characteristics of sleep sites. Second, I investigated the general sleep patterns of iguanas in the laboratory and how these patterns were affected by changes in food and injury status. Third, I examined how sleep patterns in the laboratory were altered by the presence of a predator (Crotalus cerastes). Finally, I studied the metabolic savings of Desert Iguanas during sleep at three temperatures. I found that Desert Iguanas in the field utilize different burrows for sleep than for retreating from predators. Compared to retreat burrows, sleep burrows were smaller in circumference (10.4 cm vs. 19.6 cm, respectively) and had less plant cover (42.5% vs. 78.2%, respectively). Iguanas were more active in July (3.9 hrs/day) than in April/May (9.0 hrs/day), slept in deeper burrows in July (21.7 cm) than in April/May (6.1 cm), and frequently changed sleep site burrows (every 3 days). In the laboratory studies, I found that Desert Iguanas slept 14 hours per day and spent the majority of their time (50.2%) within their burrow. There was no difference in sleep patterns between well-fed and hungry lizards despite a significant change in weight. Tail injury resulted in increased sleep time. The presence of a sidewinder resulted in reduced sleep time and an increased number of asynchronous eye closures (ASEC) distal to the predator. Finally, I found that Desert Iguanas save approximately 25% more energy by sleeping than remaining alert. The results of these studies clearly demonstrate that the sleep patterns of Desert Iguanas are influenced by environmental circumstances and, therefore, models attempting to explain the evolution of sleep should account for such ecological factors.
Revell, T. K. 2005. The behavioral ecology of sleep in the Desert Iguana (Dipsosaurus dorsalis). Unpublished PhD dissertation, Loma Linda University, Loma Linda, California
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Last Revised: Tue, Jan 30, 2007