Sandy Wolf’s goal for the evening is simple: Tag 25 bats.
The tags are small, metal microchips, similar to the ones used to ID dogs and cats. Inserted under the skin, the tags allow her to record the bats’ location when they fly past an antenna placed at a roost entrance or other frequently visited area.
“Who knows if that will happen?” she says. “Sometimes we don’t get any (bats). Other nights we have so many we can barely keep up.”
But there’s nothing she or her research partner, Dave Dalton, can do about it. They just have to wait and see how many bats show up at the hummingbird feeders they’re monitoring at a home near Saguaro National Park on the eastern edge of Tucson.
The researchers are driven by a desire to understand the bats’ migratory routes, which will ultimately inform decisions by the U.S. Fish and Wildlife Service and other regulatory agencies on how to manage and protect bats on public lands.
For the past 15 years, Wolf has studied wildlife in urban Tucson and the desert Southwest—first as a researcher with the National Park Service and now as an independent researcher alongside Dalton.
Wolf is petite, with sandy blond hair and a warm smile. Around her neck hang her glasses and a headlamp to spot the bats in the dark.
She has a ceaseless curiosity about bats. “They’re just so cool,” she says. “There are over 1,000 species of bats, and they all eat, move and fly differently.”
These days, Wolf is focused on surveying and monitoring lesser long-nosed bats. Their colonies range from a few thousand to 50,000 individuals. The bats roost in caves in the outskirts of urban areas and in the mountains throughout southern Arizona and Mexico.
Enthusiasts for the lesser long-nosed bat—Wolf included—refer to them simply as “leptos” because they are the best-known members of the genus Leptonycteris.
Wolf’s current study revolves around two objectives. First, she wants to understand the extent to which the lesser long-nosed bats rely on residential hummingbird feeders in urban areas. Second, Wolf wants to understand the migratory routes of this species throughout southern Arizona and Mexico and ultimately determine whether the bats are adjusting their migration routes to gain access to hummingbird feeders.
But not just anyone can go out and catch these bats. Wolf and Dalton had to obtain permits and have their research plans approved by the U.S. Fish and Wildlife Service and Arizona Game and Fish.
Wolf’s long-term goal is to improve management of the species. “The better you understand the animal,” she says, “the better decisions you can make (to protect them).”
Trap, tag, release, repeat
By 7 p.m. about 10 students, researchers and friends have gathered to help tag the bats. With Wolf and Dalton leading the way, the group sets up three black, badminton-like nets called mist nets alongside three large hummingbird feeders.
A chair is positioned near each trapping area so Dalton and two other monitors can watch the nets and make sure any caught bats are quickly removed and processed.
In the garage are long tables where the four processers—Wolf and three mammalogists—are ready for action. In front of them are scales for weighing each bat, tapes to measure the forearm length and wingspan, sugar water to feed each bat, scissors to cut a small patch of hair on the back, sterilization equipment to minimize the risk of infection to the bat, and a hypodermic needle containing a passive integrated transponder (PIT) tag, which is injected under the skin of each bat.
Everyone who handles the bats wears thick gloves to avoid getting bit.
The first bat arrives at 7:45, well past sunset. Dalton and the other net monitors can’t see the bat approaching the feeder. Only after it’s caught in the net is it spotted flapping, trying to get free.
Dalton gingerly frees the bat. He holds its body and wings gently as he places it in a small cloth bag, where it can be contained and calmed as he carries it to the garage.
Processing the bat takes 15 minutes.
The bat is passed down the line. Each processer is responsible for a specific task to make the processing as efficient as possible. The bat is weighed, measured and offered sugar water. With a little coaxing, the bat drinks vigorously from a plastic dropper with its long, narrow tongue.
The PIT tags are about the size and shape of a grain of rice. Each tag contains a unique identification number. Antennas that read the tags are stationed at two hummingbird feeders. Wolf hopes this new method of tagging the bats will allow her and Dalton to monitor them with greater accuracy.
As the first bat is released, the processing team looks more at ease. Just in time for bat No. 2, followed closely by bat No. 3.
Mysterious migrations
Twenty-eight species of bats live in Arizona, but the lesser long-nosed bat is the only one that is endangered. The primary reason has historically been loss of habitat, says Scott Richardson, a supervisory biologist with the U.S. Fish and Wildlife Service.
But now a changing climate will very likely mean that higher average temperatures and prolonged droughts in the Southwest will put the bats’ food sources at risk. These nectar-feeding bats mainly eat the nectar and fruit of saguaros, organ pipe cactuses and agaves.
Little is known about the migratory patterns of lesser long-nosed bats, making conservation a challenge for wildlife managers. Wolf hopes that her monitoring efforts will uncover whether the bats migrate directly from their maternity roost in Mexico to the Rincon Mountains, on the east side of Tucson, or whether they take a roundabout route from other roosts in southeastern Arizona.
Taking a roundabout route could indicate that the bats are coming to the Tucson area specifically to make use of hummingbird feeders after their natural food sources are used up elsewhere. Such changes in migratory routes might have implications for the ability of the bats to adapt to changes in food sources and a warmer, drier climate.
Either way, understanding their life history, including their migration patterns, could help the long-term management efforts in southern Arizona.
Just getting started
Everyone in the group looks relieved when Wolf and Dalton call it quits and close the nets at nearly 11:30. Of the 12 bats retrieved from the nets, 11 are tagged. (One was deemed too small for tagging.) Ten are lesser long-nosed bats, and one is a related Mexican long-tongued bat, a species less common to the area.
It takes about 30 minutes to clean up the gear. Although tired, the group is satisfied with what they have accomplished. For Wolf and Dalton, this is just the first of four nights of tagging, during which they hope to tag a total of 100 bats.
Times are tough for wildlife researchers. Wolf and Dalton are self-funding their study, and the equipment they use is not cheap. Each antenna can cost $2,000, and they need several for their project.
But Wolf makes clear the value of this study: If they can get some good data and work out the techniques of tagging the bats and using the new antennas at the roosts, they’ll have a better shot at securing funding for next season.
Valerie Rountree is a reporter for Arizona Sonora News, a service provided by the School of Journalism at the University of Arizona. Reach her at yrountree@email.arizona.edu
Researcher Dave Dalton shows off a bat’s wing. (Photograph by Valerie Rountree)