Environmental DNA and drones offer a window into migratory bat habits
by Shaena Montanari
Every year, the Mexican Long-nosed Bat (Leptonycteris nivalis) migrates from central Mexico to northern Mexico and the southwestern United States, stopping to feed on nectar from succulent flowers along the way. However, species numbers are declining, and researchers think this may be connected to a decline in agave, their primary nectar source.
Bat Conservation International scientists and collaborators are using innovative technological approaches to monitor agave plants in the U.S. and Mexico to better understand how to protect this precious food source for the endangered nectar-feeding bat.
These emerging technologies, environmental DNA (eDNA) and drone surveys, are “less invasive ways to track their movements and where they’re feeding,” says Mylea Bayless, Bat Conservation International’s Chief of Strategic Partnerships. She says this is lower risk for bats since it is not necessary to catch or handle the animals.
Dr. Kristen Lear, Bat Conservation International’s Endangered Species Interventions Specialist, says Mexican Long-nosed Bats, many of them pregnant females, migrate over 700 miles, making it very difficult to study them and their movements. Because they primarily move at night and are difficult to catch, Bat Conservation International has turned to a new application of eDNA sampling to figure out where exactly they are stopping to feed when they migrate.
“The migratory corridor is critical to protect, but we actually don’t know where the migratory corridor is yet,” Dr. Lear says.
This is where eDNA comes in handy. When agave plants bloom, a stalk grows from the
center of the plant, reaching heights of over 10 feet. These stalks are filled with hundreds of nectar-filled flowers that are perfect food for bats. In collaboration with Shippensburg University and Northern Arizona University, Bat Conservation International is developing a method of sampling agave flowers for traces of DNA from bat saliva or hair to figure out whether a bat has visited the flowers to feed on the nectar.
Now, Dr. Lear and her colleagues are piloting this method of eDNA sampling from agave plants in Big Bend National Park in Texas, home to an important Mexican Long-nosed Bat maternity roost. They are working in collaboration with the Texas Parks and Wildlife Department on these sampling efforts.
Drone surveys also come in handy for getting a bat’s-eye view of agave plants from the air. This work is being done in northeastern Mexico with Bat Conservation International partner Especies, Sociedad y Hábitat, A.C. (ESHAC), an environmental non-profit in Mexico, in collaboration with local ejidos (communal farming areas) and CONANP (Mexico National Commission for Natural Protected Areas). The goal is to survey the overall health of agave habitat in the bats’ migratory corridor.
Dr. Lear says it is necessary to assess the health of agave habitat because it is threatened by urban expansion, wildfires, and climate change. Getting a detailed understanding of agave health is typically done through on-the-ground transects, says Bat Conservation International Researcher Dr. Ana Ibarra, who explains the effort “takes a lot of human power and a lot of time.” With the new drone technology, Bat Conservation International and partners will be able to rapidly assess habitat quality and identify priority restoration areas to protect the Mexican Long-nosed Bat.