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Photo: Lynn Mc Bride

The Eckert James River Bat Cave Preserve, located outside of Mason, Texas, boasts one of the few caves in the United States which
the Mexican Free-tailed bat (Tadarida Basilensis Mexicana)
chooses as a nursery site for the birth and rearing of its young. 
It is one of the largest maternity colonies known to exist.
The nightly emergence of these bats from the cave
during the summer months is an awesome natural spectacle
which should be appreciated by everyone at least once in their life.

t.jpg (3422 bytes)he first time I saw the cave, I was surprised at its small size and unassuming appearance. It didn’t have the grandeur of Carlsbad Caverns in southeastern New Mexico, nor did it contain the intricate limestone formations typical of such caves. What was all the excitement about?  What this cave lacks in size, it makes up for in another very special way. It is the summer home to an extremely large number of bats, an estimated four to six million of them.

The Mexican free-tailed bat is so named because its tail extends beyond the membrane which surrounds it, making the talk partially "free"; most species of bats have their tail completely enclosed by this membrane. There are six species of free-tailed bats in the US. This species is migratory, spending the northern winter months in caves throughout central Mexico. The female bats begin to arrive in Texas in late February and early March, most already pregnant. Migratory groups from Mexico are continually arriving from this time until early June. By the end of June, most of the females will already have given birth. The males also migrate, but play no part in the raising of the young. They tend to form smaller "bachelor" colonies under bridges or in old buildings. One can find males in caves with the females in the early part of summer, but they tend to leave as the babies are born.

Mexican Free-Tailed Bats are insectivorous, feeding mostly on moths and beetles. They prefer to forage high above the ground, having been found at altitudes of almost 10,000 feet. The bats consume enormous amounts of insect nightly, some of them notorious agricultural pests lie the fall armyworm moth and the corn earworm moth. Nursing mothers can consume more than their body weight of insects in a single night. They make use of echolocation, a sophisticated type of "bat sonar", to locate and capture their insect prey.

Caves are almost always chosen as maternity sites of the Mexican Free-Tailed Bat. Not all of the caves in Texas are suitable for this purpose, a reason why the Eckert James River Cave is so vital to the ecology of the species. For a cave to be suitable as a maternity site, it must fulfill certain requirements such as; the proper humidity, ventilation and veiling height before the bats consider using it.

After the babies (called pups) are delivered in June, it takes about five to seven weeks for them to start flying on their own. Up until this time, they are totally dependent on their mother’s care. They are born hairless and nurse on milk supplied by the mother. The pups are placed in a separate roosting area for the adults within the cave, termed a "crèche. The mother bats have the uncanny ability to locate and feed their biological offspring when they return from their nightly feeding forays. Both odor and vocalizations play a part in reuniting both mother and pup.

As the young become independent, they must learn to fly and fend for themselves. By September, some of the bats already start to leave Texas for their winter roosts in Mexico. Come late October, the cave is virtually empty. The famous colony under the Congress Avenue Bridge in Austin is also a maternity roost for the Mexican Free-Tail Bat, though the population there is considerably less than that at the James River Cave (around 750,000). This is one of the instances where a man-made structure also serves as a maternity site. There are other maternity caves scattered throughout ventral and south central Texas, mainly in the Hill Country.

Besides the Mexican Free-Tailed Bat, the James River Cave also supports a sizable population of the cave bat or cave Myotis (Myotis Velfer). While numbering far less than the Mexican Free-Tail (an estimated 20,000), this species also uses the cave to rear its young. The cave Myotis young are born earlier then those of the Mexican Free-Tail Bat. It is also an insectivorous species, but tends to forage closer to the ground among the trees and bushes than the Mexican Free-Tail Bat.

The specialized cave environment has produced a community of living organisms which rely on the bats and bats’ droppings (guano) for survival, and is termed a "guano ecosystem". There are millions upon millions of carnivorous beetles (Dermestes Carnivourous) living and feeding on the cave floor. There are also various species of ticks, mites and other beetles which live in the cave, some of which are unique members of these "guano ecosystems". The guano itself supports a bacterial fauna which only recently is being appreciated for its diversity and usefulness to people.

In 1990, the James River Cave was donated to the Nature Conservancy of Texas (TNC) by Richard Philip Eckert and Virginia Eckert Garret. The Eckert family has been ranching the land surrounding the cave since the early 1900’s. The preserve is now cooperatively managed by TNC and Bat Conservation International (BCI) The cave’s value as a maternity roost for the Mexican Free-Tail Bat was recognized early on by W. Philip Eckert, who passed this appreciation on to his descendants. Today the cave is one of the few in Texas both protected as a nature preserve and accessible to the public.

The Eckert James River Bat Cave Preserve is located approximately 16 ½ miles south of the town of Mason, in Mason County, Texas. Part of the drive to the cave is paved but the rest will require negotiation of dirt roads and some stream crossings. The final stretch crosses the James River itself, the crossing is accessible to passenger vehicles most times of the year. A pamphlet with detailed directions and a map to the cave can be found in several locations throughout Mason. The Information Center kiosk on the courthouse green in the center of town is probably the easiest place to pick up one. Most of the restaurants and convenience stores around town also have maps. A visit to the Mason Chamber of Commerce, located on the courthouse square, will not only provide directions to the cave, but can also give additional information about the preserve and other sites of interest around Mason.

The evening emergence of the bats is impressive at any time of the year, but the end of July and early August, when the young bats begin to fly, provide especially prime viewing experiences. Not only are there peak numbers during this time, but visitors are usually treated to sights of predators, such as; red-tailed hawks, snakes and raccoons feeding on the emerging bats. By this time the bats are also exiting the cave much earlier than in the beginning or end of the summer. Being quiet when visiting the cave is important so as to minimize disturbance to the bats, and will allow a better opportunity for seeing other wildlife in the vicinity.

The preserve will also be opened one or two Saturday mornings a month for visitors to watch the return flight of the bats. The in-flight is equally impressive, though quite different from the evening emergence. The bats fly into the cave from high altitudes, traveling at high speed. Some people liken the event to water being poured into the mouth of the cave. Please call the preserve manager in Mason for specific dates and times.


The Eckert James River Bat Cave Preserve is open to the public free of charge from Thursday through Sunday from 6 PM to 9PM during the summer only (usually from mid-May to mid-October). Peak visitation periods are on holiday weekends, so if you are from the local areas, try planning your visit to the cave at other times. Out of town visitors mostly come on Friday and Saturday nights. Thursday and Sunday evenings tend to see the smallest crows.

The site is southwest of Mason, near State Highway 290, in Mason County.
Open mid-May to early October for interpretive tours Thursday-Sunday, 6 p.m.-9 p.m. Some sunrise tours of the bats returning from their nocturnal hunts also are offered.
8 acres
The preserve is open to visitors each summer when the Conservancy offers an interpretive program.
How to Prepare for Your Visit
For more information, call Anne Casselman, Bat Cave Steward, at (915) 347-5970.

From the southeast side of Mason town square on Highway 87:
· Follow the highway south about 1 mile to FM1723 and turn right.
·After 4.8 miles, turn right on FM 2389.
·Cross 2 bridges over the Llano River and turn right on James River Rd.
·Watch for deer and cattle on road. Pavement ends.
·Continue on the James River Rd. past the paved turnoff to the right, cross the James River at the ford and drive about a half-mile to a sharp left turn.
·The gated entrance to the Bat Cave Preserve is on the right at this curve. Follow the road to the parking lot.

For more on the Bat Cave visit the Nature Conservancy website here: