Bats: Plentiful, Diverse, & Threatened in AZ
By Jeremy D. Krones
Bats (Chiroptera) are an integral part of any landscape, especially in our corner of the Southwest. However, relatively little is known about them in Arizona.
Of the roughly 45 bat species in the United States, nearly 60% live in Arizona, and most of those live at least part of the year on the Mogollon Rim. Bats are predators, pollinators, seed dispersers, and ecosystem managers, and much of what we love about our landscape depends on these small, flying mammals.
Just ask Clarissa Starbuck, a doctoral student at Northern Arizona University focusing her studies on bats and the impact of wind farms on their migration routes.
For Ms. Starbuck, her passion for bats began at seven when she wrote a short story about a bat. Her academic career has since led her to Northern Arizona University to work under Dr. Carol Chambers, professor of wildlife ecology in the School of Forestry, researching the habits and migration patterns of bats with relation to key landscape features, and if wind turbines would potentially be placed near those features.
The end goal of her current research project is to create a predictive map that will show what areas and landscape features of northern Arizona are going to have higher bat use than other areas. That map will then help wind energy companies plan their developments to best mitigate potential bat deaths from colliding with the turbines.
Despite the height of wind turbines playing a large role in the debate between turbines and the impact on birds and bats, it is not part of Ms. Starbuck’s research because she is not looking specifically at the effects of wind turbines. Ms. Starbuck explained, “It seems like turbines keep getting higher and higher all the time, because the higher you put the blades, the windier it is. But, it seems that the higher they are, the more bats are killed.”
Ms. Starbuck is looking at the contiguous open spaces of the Bar T Bar Ranch to perform much of her research.
Research on the Ranches
The ranches are no stranger to such research; Ellen Parish, who now sells beef in Flagstaff for the Flying M Ranch, started her relationship with the ranch nearly 10 years ago as a researcher for Western EcoSystem Technology, Inc (WEST). WEST was contracted by wind power companies to survey the bat and bird populations on the ranches for wind towers.
Ellen’s work required her to go out to certain sites once a month in the winter and once a week in the spring and autumn, to collect data. This data was recorded and sent to the WEST labs for analysis. Sites were primarily around water tanks.
Both the contract and research ended in 2010. No wind turbines have been built on the Flying M or Bar T Bar ranches.
Dr. Chambers has been teaching at NAU for 20 years, and got into bats because her first graduate student was studying how the invasion of junipers into grasslands was affecting bats.
The student found that there was more activity around areas with higher tree and shrub density. That is probably due to the high population of bugs in and around trees, Dr. Chambers explained.
However, the high density of trees is not always a good thing:
“If you are removing trees from areas that were originally grasslands, then you're basically restoring that system. Yes, you might be removing habitat, but that probably wasn’t habitat that bats had counted on in the past. It gets tricky when habitat has been shrinking because of development.”
She also said that there is still a lot of piñon-juniper habitat in the region, so the grassland restoration the ranches do isn’t doing much damage to the bats.
An additional outcome of Ms. Starbuck’s research will be more information about how bats move across northern Arizona. Not many specifics are known about the migration patterns of bats in this region, except that some bats will just migrate short distances based on elevation and others will travel farther, much like birds do.
Most bats use echolocation to communicate and navigate through the landscape, although Ms. Starbuck did say that despite ‘common knowledge,’ bats can see fairly well and echolocation is not always the best way to track bats.
She hypothesizes that bats might navigate using large landscape features that they can see, like cliffs, valleys, and rivers, as well as echolocation for smaller features.
The Mexican free-tailed bat (Tadarida brasiliensis) and the hoary bat (Lasiurus cinereus) are two species that migrate longer distances, and use those larger features as roosting sites.
Ms. Starbuck has a hypothesis that proximity to cliffs and waters could be major factors in where bats fly on their migration. Cliffs are good roosts for bats, and for water Ms. Starbuck explained, “It’s kind of a dry place, but bats need water to live just like everything else.”
Bats that fly longer distances are usually pretty fast, but not very agile. Dr. Chambers’ first grad student would compare bats to airplanes: some are more like bombers, which move very fast but have a harder time maneuvering tight corners, whereas biplanes don’t move nearly as fast, but are more adept at tight turns.
“If you look outside at a tree, imagine a moth or a butterfly flying up and flapping around the tree. Some bats have that type of agility. Other bats really don’t,” said Dr. Chambers.
Most bats don't like to land on the ground to capture bugs; they hunt bugs by flying through the air and capturing them either in the air or by swiping them off of branches and leaves.
However, there are some species that do hunt from the ground, like the Pallid bat (Antrozous pallidus), which can be found at altitudes lower than Flagstaff.
Dr. Chambers gave a hint for how to identify a Pallid bat:
“If you have a porch outside your house and you see the remains of scorpions in a little pile during the summer, that might be a night roost for a Pallid bat having dinner.”
The Threat of White Nose
One of the biggest fears of bat researchers in North America is the white nose disease.
Over six million bats have died from the disease, transported by a fungus of the same name, since its first discovery in 2006, in a cave in New York. Since then it has progressed west, to eastern Texas and Oklahoma. The fungus apparently ‘jumped’ to Washington State last year.
Researchers like Dr. Chambers and Ms. Starbuck fear that the fungus will be in Arizona very soon, and are scrambling to collect as much data on bats as they can before these populations are affected. Dr. Chambers explained that we know more about bats in the eastern US because those bats aggregate in larger hibernacula, which are the clusters in which bats sleep during the winter.
Arizonan bats collect in smaller hibernacula, which Ms. Starbuck says could contribute to a slower spread of the white nose disease, but also contributes to a lower level of understanding about bats in the Southwest because research and collection is more difficult.
With the specter of white nose looming, any data on bats is valuable to the greater community. For those of us not in the field, there are many ways to support bat research and conservation, including advocating the protection of their habitats and food sources.
Please contact the Diablo Trust office for links and documents to learn more.