Community gardens, parks and green roofs within densely populated North American cities may hold unique benefits for bats. The bats, in turn, provide numerous benefits for us. They eat mosquitoes and other pests (sometimes consuming half their own body weights), disperse seeds to spread greenery and pollinate important plants. Many urban types can be found roosting in street trees, office buildings and (of course) belfries.
A study published in July in Global Ecology and Conservation found that green roofs on city buildings, planted with native grasses and shrubs, attract arthropods that bats like to nibble on. Biologist Kaitlyn Parkins, a research assistant for New York City Audubon, set up acoustic detectors, which can pick up bats’ echolocation calls, at four sites around the city. She expected to see two or three species foraging over the roofs. She was surprised to discover that five — big brown, little brown, eastern red, hoary and silver-haired bats — flew in for the late-night buffet.
“Bats that do well in cities are generalists” in their flying and roosting habits, Parkins said. The brown varieties search for prey in open spaces, then snuggle in the nooks and crannies of buildings — the older and cobwebbier, the better. The red, hoary and silver-haired prefer to rest in city trees.
Some species have been seen foraging around street lamps, waiting for bugs drawn to the light. But for others, light pollution in a city that never sleeps may throw off their circadian rhythms, a recent analysis published in Mammalian Biology found. Those bats spend more energy avoiding brightly lit areas. For a high-metabolism mammal, that means more stress in finding food and a place to rest, said Micaela Jemison, communications manager of Bat Conservation International, an advocacy group based in Arlington, Va..
This week, Jemison and other bat advocates are taking advantage of the spooky holiday to raise awareness about the winged creatures. This is the second Annual Bat Week, and organizers hope to end it with a record-breaking Halloween: They'll help volunteers at events around the country build bat houses, with a goal of making 5,000 in one day.
The efforts may lean on bats' spooky reputation, but Jemison hopes most people realize that folk tales about bats thirsting for human blood are just that. “We are not interesting to bats at all,” she laughed. “We’re just another obstacle for them to get around.”
Also false: The old myth about bats getting tangled in your tresses. Jemison said that misconception came about in the 17th century, when people believed that bats, since they flew like birds, also made nests and would pluck out human hair to build them. (The fact that people also wore gigantic wigs back then might have had something to do with it.)
Even more reasonable concerns, like rabies, are generally overblown. Bats shouldn't be allowed inside of your home, and you definitely shouldn't try to handle them, but they're unlikely to get you sick: While most cases of rabies in the United States can be traced to bats, only about two cases occur each year. Research suggests that less than 1 percent of bats actually carry the fatal disease.
Parkins, the biologist, said we have a lot to learn about our nocturnal neighbors. When she carried her acoustic detectors on the New York City subway, she found that riders were curious about bats in their neighborhoods. “People may know they’re around,” she said, “but they’re still kind of cryptic.”