Bats generate a measurably distinct aerodynamic footprint to achieve lift and maneuverability, quite unlike birds and contrary to many of the assumptions that aerodynamicists have used to model animal flight, according to University of Southern California aerospace engineer Geoffrey Spedding.
The researcher, together with a multi-institutional team of scientists found that bat flight is quite different from bird flight, particularly at very small scales. They based their findings on new measurements of aerodynamic performance in the wing beats of a small species of bat.
"Bats with a body mass of 10 30 grams or about the weight of one or two teaspoons of sugar and tip-to-tip wing spans of 25 30 centimeters about the length of a human hand generate very different wakes," he reported in the May 11, 2007 issue of Science.
"The tell-tale tracks in the airflow caused by the wing beat have a very different pattern for bats, and this difference can be traced to the peculiar upstroke," he continued. "That, in turn, is likely caused by the collapsible membrane of the bats wing, which needs to maintain some degree of tension."
His research groups findings are presented in an article titled "Bat Flight Generates Complex Aerodynamic Tracks." Coauthors included A. Hedenstrm, L. C. Johansson and M. Wolf of Lund University, Sweden; R. von Busse of the University of Munich, Germany; and Y. Winter at Bielefeld University in Germany.
Bats constitute about 20 percent of mammalian species, but not much attention has been paid to them because of their nocturnal habits. Most bats eat flying insects, consuming up to their body weight each night. Their agility and tremendous ability to maneuver in flight is accentuated by their ability to locate prey using an advanced echo-location system, which is basically a sonar operated by ultrasound.