They captured and radio-tagged bats from maternity colonies in 2009 and 2010, tracked their activity to determine foraging areas and roosts, and counted bats as they exited roosts. They captured 23 Indiana bats in 2009, of which 14 were adult females and the rest juveniles. They captured 26 bats in 2010, 20 of which were adult females.
Tracking the radio-tagged bats to roosts, they observed that the female bats didn't always return to the same roost. Applying their new approach to the data, "We were able to map a network of connections between the roosts," said Kniowski, who is in the interdisciplinary geospatial and environmental analysis program at Virginia Tech and works out of the Department of Fish and Wildlife Conservation.
A comparison of the 2009 and 2010 network maps revealed a dispersed roost area in 2009 and a dense network in 2010, with only the most central roosts reused in the second year. The roost area for the entire colony was more than 6.5 square miles in 2009 and less than a square mile in 2010, whereas the foraging area was about 14 square miles both years.
Some flexibility is to be expected in terms of roosting, given the transitory nature of snags, the researchers note in the article. "Roost conditions are very fleeting," said Silvis, who also did his master's research at Ohio State under Gehrt.
But the substantial dispersion of the roosts in 2009 could have been dangerous for the bats. The researchers simulated the removal of roosts to determine the robustness of the colony. Removal of only 5 percent of roosts in 2009 would have resulted in fragmentation of the network, whereas it would have required removal of half of the roosts to fragment the tightly knit network of 2010.
The researchers suggested in the article that they may have witnessed colony behavior changes associat
|Contact: Lynn Davis|