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Our bats go south for the winter, eat bugs in the summer

Article by Charlie Green

Wildlife – November 1998 – Colorado Central Magazine

FOR A CHANGE from the issues which readers of this magazine can disagree over, I’d like to introduce one which we might all unite to support: bats.

Yeah, bats. Bats aren’t just Halloween cutouts; actually, around here, it’s rare to see bats that late in the year. They’ve usually migrated south before then. These are our invisible companions each summer evening. I’ve sat and watched them (on moonlit nights) both in the city and in rural Frémont county.

Bats are beneficial for humans in numerous ways — nearly all of them involve eating insects. One bat can eat 600 mosquitoes an hour, but I have to admit, like the rest of us, they prefer a more substantial meal — like a moth or a beetle, which they will often flip into their mouths with their tail while flying through the air.

The consumption of insects by a colony of bats will amount to hundreds of pounds of largely destructive insects, about half their body weight each day. I’m frankly envious of being able to eat that much and be so small.

Bats, as Batman pointed out in the movie, are not rodents.

They are the only flying mammals. Nor are they blind, even though they use echolocation (like the SONAR that submarines employ) to locate prey. Shine a light on a colony of sleeping bats and they will certainly respond. Otherwise predators would find them easy prey.

Our bat friends don’t attack people, but they will fly toward someone to escape a perceived threat or to eat a bug above the person’s head (and not get tangled in that person’s hair). Like all mammals, bats can get rabies (usually from being bitten by an ineffectual predator), but the percentage is much lower in bats than in other mammal species. The only way to get bitten by one of these gentle creatures is to pick it up without using gloves. I’d bite someone picking me up, too.

Actually bats can be gentled easily and get used to being handled. Like African hedgehogs, bats are cute and unique, but being nocturnal, they aren’t ideal pets. Besides, who’s gonna catch all those bugs for them to eat? Most bat handlers only keep bats while they heal from injuries, then release them back into the wild again.

In Central Colorado, we have the prestige of having the largest bat colony in the state. The inactive Orient Mine in Saguache County is home to about 100,000 free-tailed bats (near the north of their range) which eat about two tons of insects each night from the fields of farmers in the San Luis Valley. As a contrast, the colony in Carlsbad Caverns numbers about 350,000.

Bats and farms have gone together for hundreds of years. Before insecticides, bats and other insectivores were the only control for pests. Unknowingly or aware, the farmers of the Valley are allied with these creatures of the night.

Bats will fly many miles to feed for hours before returning to their daytime bedroom, so the Orient Mine colony patrols the whole length of the Valley (and maybe on the east side of the Sangres in the Wet Mountain Valley — more research is needed). Plus, their appetite for insects also benefits the forests at the edges of the valley. Nursing females, however, stay closer to home since they usually return once each night to nurse the solitary baby.

A visit to the Valley View Hot Springs, a clothing optional resort next door to the Orient Mine, is a treat for bat lovers (or the bat curious). At night from a comfortable spot in the big pool, the bats can be clearly seen (and heard by many with acute hearing, like my wife) above the soakers. Swirling and diving in the moonlight, bats catch the insects attracted by the hot water. I have observed the same effect above a charcoal grill or around a light in the Wet Mountains on a summer’s eve, albeit dressed somewhat more warmly (me, not the bats).

Old mines make the most comfortable man-made homes for bats since they evolved living in caves. None of Colorado’s bats are tree dwellers.

Most bats in Colorado are migratory, but if a cave or mine is deep enough, they will hibernate in them. No documented mines in Colorado have overwintering colonies, but that doesn’t mean it doesn’t happen. Bat researchers are still finding shafts with colonies and may find one containing a year-round family.

Unfortunately, mine shafts are being filled in at an increasing frequency for safety reasons, which is a valid consideration. But there are alternatives; the DOW and BLM are conducting a joint project to evaluate 60 mines for gating in lieu of closure in Colorado. A bat gate allows bats to slip between grates into the mine while it keeps predators and people out.

Many mines across the US are being gated, but a 3′ entrance can cost over $150,000. The budgets for public entities (BLM, Wildlife Departments, etc.) are wholly inadequate to meet the needs for this project; the BCI North American Bat Conservation Partnership gathers resources to assist them in saving the homes of countless bats.

WHAT CAN YOU DO for these fascinating and valuable creatures?

Well, it isn’t as easy to help bats as you would birds by putting out feeders. But they do need housing. Bats need specialized environments for living quarters: warm, dry, and dark. While we aren’t fully sure exactly what they like in housing, the North American Bat House Research Project is seeking those answers by enlisting volunteer researchers. I urge anyone who would like to assist in this project to contact them at:

And they’ll provide details on building your own bat house and mounting it where bats will be likely to move in and occupy it. There is a serious lack of bat houses in Colorado for research. This year I have added one more to the database; please join me.

What kinds of bats live in our neighborhood? There are five bat species found here, but 18 different species have been documented in Colorado.

The free-tailed bats (often called Mexican free-tailed bats, a common Texas bat) who live in the San Luis Valley are found only in the extreme SE and SW corners of Colorado.

The Valley connection reveals the ancestral background linking the Valley to the rest of the Rio Grande watershed.

The Big Brown Bat is a common bat in Colorado and is the largest bat in North America. I have seen these bats flying in the Texas Creek area — and they look like birds. These bats eat a bunch of bugs; I’ve only seen them when moths are abundant. Because of their size, they prefer a ¾” or larger crevice to live in.

But most Colorado bats are satisfied with ½” crevices.

Pallid bats are light colored and small. They fit well into bat houses and will form nursery groups if they like the house.

Little Brown Bats are also common bat house occupants. These little bats are not found in arid areas, eliminating a lot of Central Colorado. They will also form nursery groups in larger bat houses.

The Yuma Myotis is a shy little creature who invariably lives near water. They are found in the extreme southern part of the state. Little research has been done on the full range or habits of these bats.

Bats have been misunderstood, largely because of their nocturnal habits and secretive ways. While there are no records, I am sure more than a few insect attacks on our precious forests have been thwarted by these voracious predators.

All those moths which fly out of your car each morning are a staple of the unseen bats around us. So shoo them out the window knowing they might be a meal for a bat friend. But I still recommend swatting mosquitoes!

For more information try this website:

Or for a source of detailed information try:

Bats of Colorado: Shadows in the Night by D.M. Armstrong, R.A. Adams, K.W. Navo, J. Freeman and S.J. Bissell, available from the Colorado Division of Wildlife, 6060 Broadway, Denver, CO 80216, 303-297-1192, and published in 1995. This manual provides a good basic review of bat ecology, bats of Colorado, health issues and the importance of conservation measures to maintain and increase bat numbers.

Charlie Green is an old curmudgeon who is moving to rural Frémont county so he can watch the wildlife cavort, the roads get paved, and all the new neighbors move in.