Research at Hobart and William Smith Colleges helps lay to rest a common misperception about these fascinating creatures.
(June 12, 2003) GENEVA, N.Y. — The observation that bats can avoid obstacles in total darkness using sound waves has led to the assumption that they are sightless—hence the oft-heard expression “blind as a bat.” Not true, according to research conducted on the campus of Hobart and William Smith.
Biology Professor Jim Ryan, working with William Smith junior Alyssa Carlson, has begun a series of studies aimed at uncovering the visual capabilities of two types of bats: Microchiroptera, which navigate using echolocation (emitting ultra-high frequency sound pulses that bounce off an object and return as echoes) and Megachiroptera, which use vision to navigate.
Bats have adapted to a unique suite of problems, not the least of which is the need to fly in a complexly cluttered environment at relatively fast speeds. “Many bats have solved these sensory problems by echolocation,” Ryan says. “Other bats lack the ability to echolocate and must, therefore, rely on vision to navigate their shadowy world.”
Ryan and Carlson compared the retinas of “micro” and “mega” bats using a scanning electron microscope, which allows the tiniest details of the retina’s cells to be photographed. They discovered dramatic differences in the design of the retinas in the two groups. While both groups can see, the retina of “mega” bats was complexly folded allowing many more rod cells (the cells responsible for sensing shades of gray) to be packed into the retina. Just how the retinal folding enhances their nocturnal vision remains to be determined.
The researchers plan to expand their studies to include other species of bats, to see if these patterns are widespread. They also are preparing a scientific publication on their findings and plan to seek additional funding to pursue their research.
Ryan came to Hobart and William Smith Colleges in 1987. He earned a bachelor’s degree at SUNY Oswego, a master’s degree at the University of Michigan and a Ph.D. at the University of Massachusetts. His research has taken him around the world, including Madagascar, where he spent three summers surveying the rainforest for what was to become Madagascar’s first national park. His efforts include conservation of mammalian biodiversity in Africa. He is the co-author of a college textbook on mammalian biology titled “Mammalogy.”
Carlson, a William Smith junior from Montgomery, N.J., is earning a dual major in biology and environmental studies. She is the past treasurer of the health professions club and past vice president of the biology club at Hobart and William Smith. For the fall semester, Carlson plans to study in Australia as part of an off-campus program sponsored by the Colleges.