Comportamento de 500.000 morcegos brasileiros à noite em Carlsbad Caverns, Novo México

User: Nickolay Hristov, assistant professor of life sciences, Winston-Salem State University and the Center for Design Innovation, North Carolina

Project goal: Visualizing behaviors that occur in the dark

At 5 p.m. in Carlsbad Caverns National Park in New Mexico, visitors trickle out of the caves that are home to thousands of bats. No one was certain exactly what they did in the dark cavern because light from researchers’ headlamps and flashlights would perturb the animals’ natural behavior.

Hristov, working as a postdoc with Thomas Kunz and colleagues at Boston University, obtained thermal infrared imaging technology, which was originally developed for military use. Using the technology, they were able to see the bats in total darkness and record their movement—in blobs of color—from just 15 meters away, in the dark. Researchers attempting to study this cave-dwelling species have wondered about the size of the colonies, and how the individuals navigate in the presence of many other bats. Kunz’s group found that the number of the bats in caverns fluctuates by as much as a million, depending on the time of year. On a daily basis, the colonies appear to expand and contract to help adjust to ambient temperatures (Integr Comp Biol. 48:50–59, 2008).

Much of the work was done using single camera views, but “creative camera placement [of three thermal infrared cameras] can give a lot of information,” Hristov says. The researchers are now placing the cameras in specific positions in order to track flight trajectories in three-dimensional space.

To examine wider (kilometer-scale) distances of movement in the field, researchers might consider global positioning system telemetry tags that can accurately trace a bat’s flight route, allowing researchers to infer when it is eating or drinking. In some cases the data are overlaid onto geographic information system maps so that researchers can see the environmental context of the behavior. “In our studies, we know the specific tree branch the bat was using throughout the night,” says Ran Nathan, professor of ecology at the Hebrew University of Jerusalem. “All of these advances in technology give us data that [weren’t] available one to two years ago.” The tags run Nathan about $900 to $1500, and depending on species and application, are good for a few days when researchers sample the animal’s location once per second. Unfortunately, many of the units cannot be recovered.

Tips:

• Thermal infrared imaging and other imaging methods can be combined with 3D analysis to study collective group behavior not only in bats but in species ranging from butterflies to elephants, Hristov says.

• When considering telemetry and other field studies that capture aerial movement, don’t forget to account for the properties and dynamics of the atmosphere; consult an atmospheric scientist. Similarly for biologists studying sea animals—consult an oceanographer.

Source/Fonte: The Scientist.