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September 2013, Volume 11, Number 9
Computer models for endangered bats

The rare, nectar-eating Mexican long-nosed bat (Leptonycteris nivalis) is listed as endangered by the United States and Mexico, with reported population declines of up to 50 percent in the past 10 years. Conserving this important species is especially challenging because reliable information about its numbers, habitats and distribution is in short supply.


Emma Gomez-Ruiz removes a Mexican long-nosed bat from a mist net in Mexico. Photo courtesy of Eder Hernandez-Ruiz

In Mexico, where long-nosed bats are thinly scattered along the length of the country, pregnant females migrate northward each spring along "nectar corridors." They follow the blooming of agaves, their primary source of nectar and plants for which they are important pollinators. Some of these bats migrate across the international border into the southwestern United States. The nectar corridors, however, are not well defined, so their protection is often problematic.

Texas A&M graduate student Emma Gomez-Ruiz, with support from a Bat Conservation International Student Research Scholarship, is working to fill in some key research gaps for the species – and to demonstrate the potential of new computer modeling for identifying critical habitats for wildlife. Her study reached from the northeastern Mexico states of Coahuila and Nuevo Leon northward into West Texas in the U.S.

Public databases now provide a wealth of data on animal and plant species, as well as topographical and climate records, while increasingly sophisticated modeling software improves our ability to combine and interpret such data.

Food availability (agaves) and cave conditions for roosts are the two main qualifications for critical sites. Gomez-Ruiz documented the distribution and status of agaves, which are also an important food source for other nectar-eating bats in the region. She also plans to use her computer models to explore the likely impact of climate change on these bats.

Current threats include the disturbance of roosts and loss of food sources due to expanding agriculture and overharvesting of wild agave for tequila and mescal. Wildfires also sometimes destroy agaves, and such beneficial bats are often intentionally destroyed under the erroneous belief that they are vampire bats.

Gomez-Ruiz began modeling the potential distribution of agaves in the study area by obtaining data from the Global Biodiversity Information Facility and Mexico's Red Mundial de Información sobre Biodiversidad. She expanded those results by searching the scientific literature and added topographical layers of elevations, slope and soil, plus climate data. Then she conducted on-the-ground research.

She used DesktopGarp, a software package developed by the University of Kansas Biodiversity Research Center, to analyze and predict the distribution of six agave species, ultimately building a single map of agave diversity. To that, she overlaid published "presence data" of Mexican long-nosed bats and began to visualize a potential migratory corridor for the bats.

During the first year, Gomez-Ruiz and her team visited a series of study sites to document agave density, cover and status. They also used mist nets at four initial locations to confirm the bats' presence, capturing and releasing about 130 bats of eight species, including 39 Mexican long-nosed bats.

The resulting nectar-corridor map suggests that areas with higher agave richness overlap with the known maternity/roosting sites for the long-nosed bats in its northern range. The research continues as she confirms and fine-tunes these initial results.

And, Gomez-Ruiz notes, "by taking advantage of available databases and powerful ecological modeling tools, then expanding on the results with on-the-ground research, we are beginning to answer key questions that should enhance the conservation of these endangered, border-crossing bats. And we are proving the value of these tools in identifying the most critical sites for the investment of always-scarce conservation resources for Mexican long-nosed bats – and for bats around the world."

This continuing study earned Emma Gomez-Ruiz the Denmark-based Global Biodiversity Information Facility's 2013 Young Researcher Award. BCI Members can read the complete story of her innovative work in the Fall 2013 issue of BATS magazine.

You can help BCI support vital bat conservation research like this around the world. Please visit www.batcon.org/donatescholarships
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All articles in this issue:
Computer models for endangered bats
The rare, nectar-eating Mexican long-nosed bat (Leptonycteris nivalis) is listed as endangered by the United States and Mexico, ...

More New Bat Species
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Unless otherwise noted, all images are copyright ©Merlin D. Tuttle and/or ©Bat Conservation International