Thermal Infrared image of flying Brazilian free-tailed bats in Texas. Key to false colors: yellow (warmest), red (warm), green (cool), blue (coolest). (Credit: Thomas H. Kunz and Margrit Betke/Boston University)
— by Julia Darcey
Finding out if wind turbines kill bats requires more than a body count. To answer this seemingly simple question, scientists need to find out how bats migrate, why they migrate, how they fly, and what air currents they follow. The complexity and inaccessibility of aerial lifestyles often means that flying creatures, like bats, are poorly understood.
That is why Thomas Kunz, Director of the Center for Ecology and Conservation Biology at Boston University, proposed a new discipline called aeroecology at the “Integrative and Comparative Biology Symposium” in August. Aeroecology is the study of the interactions of organisms in and with the air. It’s difficult to think of the air as a habitat. But to a flying animal, the air is a landscape as complex as the ground below, filled with turbulence, currents, predators, prey, and even diseases. The study of aeroecology encompasses both the structure of the air and the organisms that migrate and feed within it. Or, as Kunz puts it: “Everything above the ground is fair game.”
Aeroecology is based at Boston University, but it draws on research from scientists all over the country, working in fields as disparate as atmospheric science, engineering, and computer science. Guided by aeroecology’s cross-disciplinary approach, biologists used to working from the ground are beginning to use common devices to observe animals in flight. For example, Doppler weather-surveillance radar can distinguish birds and bats from each other based on their flight speed. Other researchers are using tracking radar to identify and record movements of migratory animals. Thermal imaging cameras-which can capture the temperature profiles of warm-bodied animals that would otherwise be invisible at night-allow researchers to census populations of the nocturnal Brazilian free-tailed bat.
When using large-scale detection instruments, such as Doppler radar, it is impossible to identify species. One way to do this, Kunz says, is to learn exactly what the wing beats of each species look like. Kunz and his colleagues plan to learn this by sending different species of bats and birds into the sky in a small container attached to a weather balloon. When it reaches the target altitude, the container will open and the animal will fly out. This will allow Kunz to record the wing beat patterns of each species in its natural aerial environment. Kunz says that such research will help identify birds and bats in the air, especially at night.
Climate change and human expansion make understanding the fauna of the aerosphere more important than ever before. Thousands of bats and birds die each year from wind turbines, and these aren’t the only hazard that winged animals face. “The air space has been greatly altered by anthropogenic development-turbines, aircraft, lighted cities, skyscrapers,” Kunz says. “I am against further development before we know the potential consequences in each situation.” The unified approach that aeroecology advocates, Kunz says, will be vital to preserving the unfamiliar and dynamic world that exists above us.