Professor’s Research Ties Bat Populations to Global Warming

UNC Professor Rick Adams

UNC Professor of Biological Sciences Rick Adams holds an epaulleted fruit bat during a 2009 research trip in Kruger National Park in South Africa. Emily Snode photo courtesy of Rick Adams

Researchers in the School of Biological Sciences at the University of Northern Colorado have shown that bat populations are highly susceptible to climate change in arid regions of western North America and act as canaries in a global coal mine for climate-induced changes in regional ecosystems.

In a paper just published in the prestigious journal Ecology, UNC Professor Rick Adams compiled 13 years of data on bat populations in Colorado. Comparing numbers of reproductive females captured each year to data on average summer high temperatures, precipitation and stream flow rates, he found that female reproduction declined in years of drought.

In the most severe drought years, female reproduction dropped below 50 percent. In non-drought years, female reproduction was between 89-90 percent. Because most bat species only give birth to a single young per year, such declines can be devastating to population numbers.

The most important variables for supporting successful reproduction were higher precipitation and greater stream flow rates, providing pools of necessary drinking water for lactating females producing milk for their offspring. Bat milk is composed of 76 percent water.

In 2008, Adams and graduate student Mark Hayes ran an experiment where they marked reproductive and non-reproductive females from a maternity colony and measured how many times each group visited to drink an artificial water source. Females that were lactating milk for their young visited 13 times more often to drink water than did non-reproductive females. These results were published in the Journal of Animal Ecology.

Because climate change models predict increased drought conditions for western North America, bat populations are likely to decline significantly in the future.

Adams, author of the award-winning book Bats of the Rocky Mountain West," conducts research in mammalian ecology, focusing on the evolution and ecology of bats. He’s also co-authored two books on bat ecology and contributed numerous articles on the subject to scientific journals. He earned his master’s and doctorate degrees from the University of Colorado.

Importance of Bats to Global Ecosystems
- They compose 22 percent of all living mammal species.
- They’re important components of ecosystems worldwide.
- There are 45 species in North America, with the majority occurring in the western portion of continent.
- There are 18 species in Colorado.
- They consume metric tons of insects every night including mosquitoes and agricultural pests.
- The cost of loss of bats just in terms of agriculture is estimated to be in the hundreds of millions of dollars per year.
- Bats in the western United States are primary pollinators for saguaro and organ pipe cactus that are keystone species in the region.
- They are important as conduits of energy and nutrients into cave, mine and cliff-crevice ecosystems that house some of the most unique biodiversity on earth.
- Bats are important components of food webs, acting as prey for many other predator species such as owls and other raptors as well as mammalian and reptilian carnivores that prey on them in their roost sites.
- They are important indicators of ecosystem health and declines in their populations signal eventual declines in many other species they share habitats with.

Video: Monitoring Bats
Adams’ research included using an infrared video camera to capture images of bats accessing an artificial water source to help determine how often lactating females visited. View short video clip (no audio).