Mexican Free-tailed Bats

Thursday, August 16, 2012

As I mentioned in my post yesterday, I specifically walked the Museum Reach of the San Antonio River to try to photograph the Mexican free-tailed bats as they emerged from under the IH-35 bridge over the river at sunset. This was the first time I have tried to photograph bats and I knew it presented a number of challenges: the relatively dim light, the fact that bats fly fairly fast and I'm not familiar enough with their habits to anticipate their movement.

I consider my initial attempt something of a success, but know I can improve on it in future attempts. The goal of this series of photos is to convey the best I can, the awe of watching thousands of bats emerge into the darkening sky:

Here are a few interesting facts about Mexican free-tailed bats:

- The bats spend the winter from mid-October to early spring living in caves in Mexico and Central America. This is their mating season.
- In the spring the bats migrate north into the Southwestern United States, especially Texas and Oklahoma with the largest population concentrated in Texas.
- When they form their colonies after arriving at their northern destination, they separate into all male bachelor colonies and maternity colonies where the females give birth and raise their pups. Males are not involved at all in the rearing of the young bats.
- The IH-35 bridge colony is a bachelor colony with an estimated 20,000 bats.
- Bracken Cave in Comal County north of San Antonio is home to the largest maternity colony of Mexican free-tailed bats in the world. It is estimated that 20 million bats live in Bracken Cave during the summer.
- The 100 million bats living in Central Texas are estimated to eat 1,000 tons of insects per night. Most of the insects they consume are agricultural pests.
- The Mexican free-tailed bats are called "free-tailed" because, unlike other bats, about a third of their tail extends beyond the tail membrane.