Building on previous studies, John Haskell (Utah State University) and colleagues Mark Ritchie (Syracuse University) and Han Olff (Wageningen University), looked at how animals forage for food based on their body size and how the food is distributed in the environment. Their model predicts home range--the area an animal uses throughout its life--as a result of body size and the structure of the environment.
"What we found is that an organism's body size is a key determinant of how often it can be expected to encounter food in its environment," says Haskell. "Resource density is often scale-dependent, that is, it changes with the scale of measurement. The food density you see at one square meter changes when you zoom out to one square kilometer."
The researchers assert that measurement scale is related to body size. Haskell explains that bigger animals measure the environment with bigger 'rulers.' While a mouse might look at the world one foot at a time, a moose can look at an acre at a time. Because these animals perceive their environment at different scales, they see different amounts of resources. In general, the researchers assert, food density decreases with increasing body size.
Haskell elaborates: "If I walk out into the meadow below my house, I find a high density of grass. But as I move up out of the meadow into the surrounding sagebrush, the grass density gets much lower.
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Contact: Nadine Lymn
nadine@esa.org
Ecological Society of America
5-Aug-2002