Ecological characteristics of bats in Mesa Verde National Park


Ecological characteristics of bats in Mesa Verde National Park,

or, How I spent my summer at a sewage lagoon

By Apple Snider

At least 16 species of bats occur among the cliffs and old-growth forests of Mesa Verde National Park in southwestern Colorado, but we know little about the ecology and status of these secretive, nocturnal animals.  I am studying the roosting habits of the Western long-eared bat (Myotis evotis), and the food habits of three closely related Myotis species.  Learning where bats roost is vital to their conservation because it helps natural resource managers know what areas to protect.  Results from my study will provide bat and fire ecologists, as well as resource managers, with some of the first ecological information about the roosting ecology of the Western long-eared bat in Colorado, the food habits of Myotis species in old-growth piñon-juniper woodlands, and the relationship of these characteristics with stand-replacing wildfire.

To learn where bats roost during the day, I needed to catch them and attach tiny radiotransmitters to their backs.  The best way to capture bats in an arid location like southwestern Colorado is to stretch mistnets, fine nylon nets, over water sources.  When the bats fly in to drink, they get tangled in the netting, and I quickly remove them.  Water is a scarce commodity in Mesa Verde, and recently has become even more difficult to find.  Over the past seven years, more than half of the park has been burned by stand-replacing wildfire.  Since the fires swept through, most of the springs, seeps and waterholes in these burned areas have been silted in by erosion and runoff.  Areas where biologists had set up mistnets in the park in the early 1990s are now dry.  So where were we to place our mistnets?  Here’s where things got a little tricky, or at the very least, stinky.  The park has four very dependable sources of water—sewage lagoons!  The water from every shower, load of laundry and toilet flush in the park drains to a lagoon.  One member of the field crew jokingly put a sign in the bathroom, “Flush twice for the bats!”  And so it came to be that we spent most of our nights setting up nets around the perimeters of sewage lagoons.

We were thrilled to discover that working at the lagoons was not as smelly as we had anticipated, and most importantly, there were plenty of bats to be found there.  During the past two summers, we captured over 2,000 bats of 15 species, including two species new to the park—Spotted bat (Euderma maculatum) and Yuma Myotis (Myotis yumanensis).  A sample of the Western long-eared bats we captured were marked with radiotransmitters and tracked to their day roosts.  Most of the roosts were located in cliffs and rock crevices.  The remaining roosts were in piñon trees, juniper trees and downed logs.  This is good news in a habitat so prone to wildfire; fires don’t damage the cliffs and rock crevices the bats frequent.

Within the park, little is known about the insect prey of these bats, and in particular the effects of wildfire and potential fire prevention management activities like tree thinning and prescribed burns.  The second part of my study focuses on insect prey dynamics in burned and unburned forests, and the food habits of Myotis species in the park.  Previous studies have found that more insect species are found in recently burned areas than in unburned areas.  By examining insects collected in burned and unburned forests, and comparing the insects found there to ones found in the bats’ fecal pellets, I am trying to learn if bats are foraging on insect prey unique to the burned forest.  So far, we have identified over 15,000 insects in 14 orders and 70 different families.  There appears to be a significant difference between the insect families collected in burned and unburned forest.  I identify insects found in the fecal pellets to Order, or Family level when possible.  I have found one to seven different kinds of insects in each guano sample.  The most common insects present have been moths (Lepidoptera) and beetles (Coleoptera).  Other insect orders I’ve found include flies (Diptera), wasps (Hymenoptera), true bugs (Hemiptera) and lace wings (Neuroptera).

I’m finished with the field work aspect of my research, and now I have many hours in the lab ahead of me.  I miss the dramatic, colorful sunsets in the park, hiking to bat roosts in remote locations, and especially seeing bats every night.  I bet you can guess the one thing I don’t miss—the sewage lagoons!

Special thanks to the Organization for Bat Conservation, Dr. Ken Wilson, Dr. Paul Cryan, Dr. Tom O’Shea, Dr. Ernie Valdez, Dr. Boris Kondratieff, Laura Ellison, Dan Neubaum, and the many field and lab assistants who have helped me conduct this research.

© 2012 Organization for Bat Conservation