Doctor of Philosophy
Dr. Christopher G. Guglielmo and Dr. M. Brock Fenton
Migration is perhaps the most poorly understood aspect of bat biology and the underlying physiological basis is virtually unstudied. Although distantly related, bats and birds are both endothermic flying vertebrates and bird migration physiology has been studied for decades. Therefore, I used migratory birds as a model system to make predictions regarding the physiological ecology of bat migration.
First, I compared brain size of migratory and sedentary bat species. Migratory species have smaller brains which suggests the costs of carrying and maintaining a large brain are incompatible with the demands of migration. Next, I studied silver-haired bats (Lasionycteris noctivagans) during migratory stopover. Bats arrived at the site with fat stores comparable to migratory birds, rarely foraged, and had short stopover durations. I proposed that bats use daily torpor to minimize energy expenditure during non-flight periods, thus sparing fuel stores for migratory flight. Finally, I compared body composition and flight muscle physiology in migrating and non-migrating hoary bats (Lasiurus cinereus). Changes in digestive and exercise organ sizes, the composition of adipose stores, and increased catabolic enzyme activities all reflected the increased energetic demands of migration. Sex-specific changes in muscle membrane fatty acid composition and the expression of fatty acid transport proteins suggest pregnant females are subject to different pressures than males.
The energetic demands of bat migration lead to many physiological changes as observed in migratory birds. However, several factors specific to bats (especially heterothermy and the timing of reproduction) result in bat migration as a distinct phenomenon compared to birds.
McGuire, Liam P., "Physiological Ecology of Bat Migration" (2012). Electronic Thesis and Dissertation Repository. 431.