TUCSON (CN) – Standing in her back yard one morning, Bea Manderscheid noticed her hummingbird feeders were empty, an unusual sight because the tiny birds that sip the sweet nectar each day never finish it.
With a bit of sleuthing, she discovered the creatures that swooped in at night and slurped the sugarwater were tiny furry bats.
“One evening I saw a feeder swing and then I saw a flash – they’re so fast,” Manderscheid said.
She and her husband Gerry learned that the nocturnal guests that first visited their Tucson home eight years ago are lesser long-nosed bats, an endangered species in the United States.
The couple has fed the bats every year since, monitored and recorded their behavior to help conservation efforts in the Tucson area. The U.S. Fish and Wildlife Service credits citizen scientists like the Manderscheids for helping to improve the health of the species.
In early January, Fish and Wildlife Service announced that the migratory bat is stable and proposed to remove it from the endangered species list. When the lesser long-nosed bat landed on the list in 1988, there were believed to be fewer than 1,000 of them at about a dozen roosts, said Scott Richardson, a supervisory biologist with Fish and Wildlife.
The agency estimates that the population has recovered significantly, to about 200,000 bats at 75 roosts.
When the species flirted with extinction nearly three decades ago, human disturbance to the plants they feed on – agave, saguaro and organ pipe cactus – was largely blamed for the nocturnal mammal’s dwindling population.
“There were things that were affecting their forage – cattle grazing and fire and tequila harvesting,” Richardson said.
Conservation efforts such as the Manderscheids’ and modifications by tequila producers in Mexico to how they grow agave have gone a long way toward the species’ recovery, he said.
A 2015 lawsuit against Fish and Wildlife from the New Mexico Cattle Growers’ Association and other industry groups gave impetus to delisting of the species. Putting the bat on the endangered list restricted some aspects of cattle grazing, and ranchers for years had sought in and out of court to have the status of the bats reclassified – something Fish and Wildlife recommended in 2007 but did not propose until this year.
While a species’ delisting ends certain special protections under the Endangered Species Act, it also requires close monitoring for five years.
“We want to make sure we didn’t make the wrong decision,” Richardson said.
Tracking the Long-Nosed Bat
The Manderscheids’ hunt for their long-nosed seasonal visitors begins in the fall. Leaving south central Mexico in the spring, where the species is no longer endangered, the bats follow “nectar corridors” of blossoming plants to Southern Arizona.
The bats arrive in droves at the Manderscheids’ home on Tucson’s East Side by mid-September. They dive into four hummingbird feeders hanging from trees every night, until it’s time for their long-distance journey south in late October.
“We go through 10 to 12 pounds of sugar a week,” Gerry Manderscheid said.
The couple has fed and watched them closely to contribute written observations to a monitoring study involving several government entities and numerous volunteers.