Category Archives: Mammals

The Fascinating Lives of Mexican Free-tailed Bats

© J. Scott Altenbach, University of New Mexico

Guest author:  Amy Sugeno

Here in the Texas Hill Country, we are lucky to enjoy many natural wonders: nesting Golden-cheeked warblers, migrating monarchs, and Texas alligator lizards, to name just a few.  But did you know central Texas is also home to the largest concentrations of Mexican free-tailed bats in the United States? There are at least 11 major seasonal roosting sites in central Texas, each of which are home to at least 500,000 Mexican free-tailed bats. In fact, an estimated 100 million Mexican free-tailed bats call central Texas their summer home! A few of these sites are available for public viewing, and visitors come from all over the world to witness their spectacular evening emergences.

Although a small percentage of Mexican free-tailed bats overwinters in Texas, most begin arriving to Texas in the spring (around mid-March) from their wintering grounds in Mexico, Central America, and possibly even as far south as South America. Females seek out one of only a handful of maternity sites to raise their young, called pups, which are born in early to mid-June. In these maternity sites, such as the ones at Congress Avenue Bridge and Eckert James River Bat Cave Preserve, the temperature and humidity must remain relatively stable in order for the pups to survive. Inside of a maternity cave, temperatures can reach upwards to 100 degrees or higher, especially where the highest densities of pups congregate, sometimes up to 500 pups per square foot.

© Thomas Kunz, Boston University

After a gestation period of 4-6 weeks, the pups begin to fly, usually around the end of July and beginning of August. It is at this time when the most spectacular emergences occur. With nearly twice as many bats needing to emerge each night to feed, they must emerge earlier in the evening, which makes them easy to see. And if they are easier for humans to see, they are also easier for birds of prey to see! Red-tailed and Swainson’s hawks and peregrine falcons are fairly common aerial predators, and watching them swoop and dive into the stream of emerging bats is a stunning sight. After the sun goes down, Great-horned owls pick up where the hawks and falcons left off. On the ground, several different snake species, raccoons, ringtails, and foxes all visit during emergence time to try and catch a low-flying or fallen bat or a bat whose wing has become impaled on the branch of a shrub.

The life history of Mexican free-tailed bats is full of fascinating facts: they can forage up to 1 mile high; they can fly up to 60 mph; mothers can find their own pup from the hundreds of thousands or millions of other pups in the roost; they can eat their own weight each night (they mostly eat moths); and they can survive in maternity roosts with ammonia levels high enough to kill a human!

And this is only the beginning. If you’d like to learn more, the best (and most fun!) way is to visit one of the fantastic viewing sites in our area. The two closest ones which are open to the public and offer educational presentations are Old Tunnel State Park and Eckert James River Bat Cave Preserve. If you want to explore further afield, Devil’s Sinkhole State Natural Area, Frio Bat Cave, and Stuart Bat Cave in Kickapoo Caverns State Park are great places to go.

Happy batting!

© Thomas Kunz, Boston University

Open House this weekend!

We’ve all set!  Covered areas in case the rain falls west of 281, a fire pit to keep us warm, really cool activities, and a grill for the hot dogs. New activities added:  Robert, the reptile guy who’s bringing some of his favorite pets, Craig the “butterfly guy” and Robyn, the bee keeper who’s bringing some tasty treats.   Hope to see you there!

UHLNC flyer Oct 18

Camouflage: Nature’s Fashion Statement with a Purpose

Guest contributor:  Phil Wyde

Have you ever wondered why animals look the way they do;  why there are so many small brown birds;  why a fawn has white splotches on its sides;  why a zebra has black and white stripes?  Nature has given each a coloration and shape to help them survive and produce future generations.

Mama owl guarding the nest at Reveille Peak Ranch. (Courtesy of Jim Baines)
Mama owl guarding the nest at Reveille Peak Ranch.
(Courtesy of Jim Baines)

Continue reading Camouflage: Nature’s Fashion Statement with a Purpose

Scavenger Hunt for Young Naturalists

Eastern bluebird nesting in a tree.  (Courtesy of Jim Baines)
Eastern bluebird nesting in a tree.
(Courtesy of Jim Baines)

The nature center recently had the pleasure of hosting fifth graders from Highland Lakes and second graders from Lago Vista, along with parents and teachers.  Led by nature center members, they  hiked along the lake and trails, hunting for beaver signs, lovely song birds (such as the bluebird above), interesting water birds, unique rock formations, wildflowers and other cool Texas plants.

Lichen vs Moss vs Rock (Courtesy of Paula Richards)
Lichen vs Moss vs Rock, with naturalist Mike Parker.
(Courtesy of Paula Richards)

For the day, they became the  naturalists, complete with filling in their own field guides, exploring the wilds of the Texas hill country.

Young naturalists working on their field guides. (Courtesy of Paula Richards)
Young naturalists working on their field guides.
(Courtesy of Paula Richards)

They found different types of cactus, and even looked at bugs that spend their entire lives on cactus and produce an amazing red dye.  They discovered a tree that makes Texas BBQ so delicious, the mesquite tree, and a plant whose berries make wonderful jelly, and whose leaves were used by Indians to make a tea for upset tummies.

A young scientist hard at work! (Courtesy of Paula Richards)
A young scientist hard at work!
(Courtesy of Paula Richards)

They even found an usual resident for this time of the year:  a pair of Canadian geese nesting on an island near the lake shore.

Canadian goose on nest.
(Courtesy of Jim Baines)

These young naturalists also spent time at different nature stations.  They learned about beavers and their habitat, including a model of a beaver den, which they could explore.

Good thing this is a model, otherwise he'd be very wet! (Courtesy of Phil Wyde)
Good thing this is a model, otherwise he’d be very wet!
(Courtesy of Phil Wyde)

Did you know that a beaver’s teeth continue to grow their entire life and that the black willow is their favourite tree?  Did you know that the entrance to their home is under water but the living quarters is nice and dry? Want more?  (link)

Learning about how a beaver fur protects them in and out of the water. (Courtesy of Paula Richards)
Learning about how a beaver fur protects them in and out of the water, with naturalist Sharon Drake.
(Courtesy of Paula Richards)

At another station, they learned about how animals become masters of camouflage to survive.  Some blend in with their environment such as rabbits whose fur blends in with the shadows in the forest, or walking sticks shaped like the branches and twigs they climb.  Swallowtail caterpillars actually mimic a common green snake to discourage those who may think they’re a tasty morsel.  For more, try this link.

Learning about the importance of camouflage. (Courtesy of Paula Richards)
Learning about the importance of camouflage, with naturalist Phil Wyde.
(Courtesy of Paula Richards)

At the third station, bees were the sweet topic.  They discussed the importance of bees in the environment, how they pollinate plants, make honey, and build their hives. Sadly, honey bees colonies are endangered, and are less than half of what they were in the 1940s.  Did you know that more that 85% of plant species require pollinators, and that one of every three bites of food we eat comes from plants that depend on honey bees and other pollinators?  Without bees, how would we feed our families?  While scientists are still trying to figure it all out, there are some simple things each of us can do (link).

Right on!  The importance of the honey bee. (Courtesy of Paula Richards)
Right on! The importance of the honey bee, with naturalist Billy Hutson.
(Courtesy of Paula Richards)

Miss Arlene, our friend from the wildlife rehabilitation center, showed the children baby opossums whose mother had been hit by a car.  They were still too young to be released.

Baby opossum sipping milk.
(Courtesy of Phil Wyde)

She also brought young bunnies who were ready to be released back in to the wild, which she did.   She taught the children how a mother rabbit builds its nest, and brought a nest roof made of grasses.  She showed them how to use flour and a sieve to see the tracks of creatures who visit their yard.

Baby rabbit heading home to the wild. (Courtesy of Phil Wyde)
Baby rabbit heading home to the wild.
(Courtesy of Phil Wyde)

As always, the children were excited to learn about these wild creatures and how to be kind and careful when around them.

I know! I know! (Courtesy of Phil Wyde)
I know! I know!
(Courtesy of Phil Wyde)

By the end of the day, the children, parents and teachers were tired but full of all they had seen and learned.  One student commented that he thought it was going to be boring, but he’s really glad he came and wanted to know when he could come again!  All in all, a very good day!