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Field Notes

bat facts

World’s Most Mammals?

Where can you find the most mammals in any single location on the planet? The answer is…in Bracken Cave. We recently visited the cave and were stunned by what we saw.

Well, if you are looking for the highest concentration of mammals in the world, look no further. Seriously? We imagined the most mammals in the world would be in Africa on the Serengeti during the Great Migration. All those wildebeests, zebras, and gazelles coming together, but we were wrong.

So where is this cave and why should we care?

Bracken cave

Visiting bats at Bracken Cave. Photo: Teresa Nichta/Merlin

Bracken Cave

It turns out, the largest concentration of mammals anywhere in the world is right here in the United States, in Texas to be exact. And what mammal would be in Texas in large numbers?  You probably wouldn’t have guessed bats. And yes, bats are mammals.  Bats happen to be one of the most important mammals/animals on the planet. But more on that in a minute.

Bracken Cave

A Brazilian free-tailed bat. Photo: Merlin Tuttle

Every spring, fifteen to twenty million female Mexican (also called Brazilian) free-tailed bats descend on Bracken Cave near San Antonio, Texas.  They all come from Mexico with one purpose, to give birth to a single pup (baby bat), raise their baby and then go back to Mexico. So it is not only the largest group of mammals in one location, it is also the largest maternity ward. Very cool.

Bats are Mammals and Great Mothers

First, it is helpful to remember bats are our only true flying mammal.  They make up about 20% of all mammal species. Generally, females have only one pup a year, making them one of the slowest reproducing animals. This makes bats even more vulnerable if catastrophe strikes.

Bracken cave

A mother little-epauletted fruit bat carrying her pup in flight in Kenya.

But back to Bracken Cave. Inside the cave, the babies are packed onto the cave walls to the tune of 500 per square foot. That is a lot of baby bats. And unfortunately, only about 50% of the babies survive. Flying collisions, predators (think hawks, carnivorous beetles, snakes, raccoons, and a bunch of other critters), all take a toll on the little pups.

Luckily, bats are some of the best mothers of all. They groom, nurse, and teach their youngsters to fly and protect them as best they can.

All the while, they are eating literally tons of insects every night, helping keep mosquito and other pesky insect populations at bay. In a single night, the bats from Bracken Cave can eat 140 tons of insects, saving farmers thousands of dollars in unneeded pesticides for their crops.  How impressive is that!

Merlin Tuttle

Bracken Cave

Merlin Tuttle calling a Little big-eared bat to his hand for mealworms

Bracken Cave is owned by Bat Conservation International (BCI) who limits access to the cave in order to minimize disruption to the bat colony. The property surrounding the cave was saved from development through a joint effort by BCI, The Nature Conservancy,  and the City of San Antonio. Talk about a conservation success story.

We had the honor of visiting as a guest of the world-renowned bat expert, Merlin Tuttle (the founder of Merlin Tuttle’s Bat Conservation) and his wife, Paula. Merlin has done more to save bats worldwide from wrongful persecution and harm from false myths than any other human so it was quite an amazing experience to be visiting the caves with Merlin and some of his team.

For us, it was one of the most moving, mind-blowing experiences either of us have ever had. Ever! Who knew 20 million (give or take a few million) bats live in a cave and come roaring out every night in search of insects. And each one of those bats is caring for a pup inside the cave when they return at dawn.

We also learned more about Merlin’s continued conservation initiatives through his website (where you can see some additional amazing photos) and his inspiring, informative book, “The Secret Lives of Bats”.

Bat Myths

So what are a few of these myths and misconceptions? Here we go:

Myth 1: Bats get caught in your hair. No, they use echolocation to find insects, often swooping to catch a bug but avoiding a collision with you.  They are not faintly interested in your hair.

Myth 2: Bats suck your blood. Well, out of 1,200 bat species, only 3 are vampire bats (all 3 are in Latin America) and generally suck the blood of cattle, not humans.

Myth 3: All bats have rabies. Yes, some do carry rabies as do all mammals, but less than 1/2 of 1% of bats have rabies. The World Health Organization reports 99% of all deaths from rabies comes from dog bites. Only 1-2 people die a year from rabies from bat contact. However, if you find an injured bat or one in your house, be sure to call a local rescuer for instructions to prevent injury to you or the bat.

Bracken Cave

A Gray Long-eared bat emerging from a woodpecker cavity in Europe

Myth 4: Bats are grotesque looking and wicked. Actually, they are quite cute, very gentle and smart creatures. As we now know, they are great mothers. But they also share their food when another bat is hungry and babysit young pups when the mom is out foraging.

Myth 5: Bats are creepy and have no purpose. Oh, but this is one of the biggest myths. Some bats can eat 1,000 mosquitos (and other flying insects) an hour, reducing the need for pesticides.  Other bats, fruit bats, disperse seeds and pollinate a number of things we eat every day including avocados, bananas, and nuts. They also produce bat droppings called guano which is an amazing nitrogen-rich fertilizer (and no, you can’t get rabies from touching bat poop).

Bracken Cave

A lesser long-nosed bat pollinating saguaro cactus in Mexico.

Bats Need our Help

White-Nose Syndrome

With all the good things bats do for us, they need our help to survive and flourish. Many bat populations worldwide are in danger of extinction from a variety of factors. In North America, bats are dying from a deadly fungus called white-nose syndrome. While there is no known cure, many caves and mines inhabited by bats are being closed to the public to limit the spread of the fungus. You can help by not disturbing bats especially while they are hibernating and providing habitat for them.

Wind Turbines

Other challenges for bats are wind turbines. They kill tens of thousands of bats each year. You can help by supporting utilities implementing conservation plans to minimize bat strikes (which also helps our bird populations) and put pressure on utilities that do not have a plan in place.

Find out if your current provider uses wind turbines and what their bat conservation plans entail. For example, Duke Energy services our area with 20 wind farms throughout the country. They are implementing procedures to minimize bat deaths from turbine blades based on years of research by slowing down the blades during specific time periods. It is not perfect, but a start in trying to protect bats and birds.

Bat Houses

Bat houses can be very helpful to provide bats with much-needed habitat. We are installing one in our backyard which will hopefully house 200 bats. You can buy one or even build your own. Instructions are easy and it is a fun project with kids. Plans can be found at The National Wildlife Federation website (see below Resources for a link).


And don’t use pesticides or at least minimize their use. Chemicals not only hurt the bats but kill the insects they eat.

Bats and Art

So what else are we doing to help bats? Dale has created a number of bat sculptures which we are using to raise awareness and funds for bat conservation. “Cliff Hanger” recently sold and a portion of the funds were donated to The Bat Sanctuary to help their rescued bats. They were instrumental in saving a number of bats from under bridges in Houston when the rivers flooded from Hurricane Harvey.

Dale also got a number of ideas for bat sculptures from our visit at Bracken Cave. All the money raised from future bat sculptures will be used for bat conservation.

And of course, by writing articles like this one,  we hope to improve the negative image many people have of bats. Let us know if we have helped you understand the importance of bats better.

bracken cave

Cliff Hanger, a bat sculpture by Dale Weiler

Bat Conservation

Lastly, join or support organizations that promote, protect, and provide education about bats. We support Merlin Tuttle’s Bat Conservation, Defenders of Wildlife, The Bat World Sanctuary, and Bat Conservation International which all have specific programs for bat conservation. Learn all you can and you will be impressed by our one and only flying mammal.

The Most Important Mammal?

We believe bats are one of, if not the most important, mammal on the planet!  Help us debunk the myths, provide habitat and spread the word about these incredibly beneficial creatures. Become a bat advocate and make a difference in wildlife conservation.


Bat World Sanctuary: List of local bat rescuers

White Nose Syndrome

DukeEnergy: ‘Bat man to the rescue’, an article on Tim Hayes’ efforts to save bats from wind turbines

The National Wildlife Federation: How to build bat boxes Bat houses to buy endorsed by Merlin Tuttle

The World Health Center: Information on Rabies

“The Secret Lives of Bats” by Merlin Tuttle

The Nature Conservancy