Friday, January 11, 2008

Crazy About Bats!

Bats, the Chiroptorium, and bat researchers.

The Chiroptorium is our man-made bat cave. Chiroptera is the order for bats in the family of Mammals, which is the origin for the first part of the name Chiroptorium. The second part of the name "torium" comes from the end of auditorium which is a large place for a gathering. So, Chiroptorium is a large place for bats to gather. In March each spring, Mexican Free-tailed Bats (Tadarida brasiliensis) arrive in large numbers from their winter homes in Mexico, Central and South America. Because our cave is a nursery colony, most of the bats are pregnant females. They leave each evening as the sun sets to find food, which is lots of flying insects, especially moths.

In the middle of June one baby is born to each mother bat. The babies, naked, pink and flightless, are deposited in a contiguous area on the ceiling or wall of their cave. The heat generated by all the close bat-bodies (up to 400 per square foot) help to keep them warm. Mothers leave their babies in the cave when out hunting for food at night. Each mom relocates her baby by calling to her pup when she returns. As she gets close she can also smell her offspring. Her milk is rich and high in fat, and her baby grows quickly, and within a month the pups are nearly as big as an adult, furred and ready to fly and feed on their own.

Dr. Gary McCracken on the left in the above photo, has done a lot of research in Texas, which has increased our understanding about Mexican Free-tailed bats, how they live, what they eat, and how important they are to agriculture. Using weather balloons with echolocation sensors on them, he was able to find out that free-tailed bats find and fly into clouds of migrating moths that they love to eat, and which provide them with important nutrition. These moths lay their eggs on corn, cotton and other crops, and the caterpillars eat the developing plants. Therefore having bats eat lots of moths before they have a chance to lay their eggs is beneficial to farmers.

The huge colonies of Mexican Free-tailed bats in Central Texas live mostly in caves, but are also found under bridges like the Congress Avenue Bridge in Austin, and in culverts. When an continuous stream of bats emerge in the evenings for many minutes, and even hours, it is hard to imagine how many bats are flying in front of you. Until the last few years there was no way to accurately count the numbers, until Dr. Tom Kunz, from Boston University, on the right in the picture above, developed a method using infrared video photography and computers. A continual infrared image of the bats emerging from the mouth of a cave, in which the warm bodies of the bats appear like little white dots moving against a dark background is read by a computer and the total number calculated.

One of Dr. Kunz's post-doctoral students, Dr. Nickolay Hristov, shown with his new Belgium sheep-dog three month old puppy, Coda, and another graduate student, seen below, Louise Allen came to The Bamberger Ranch in 2004 and conducted a count. The next spring they started a regular once a month count of our bats during the time the bats are in Texas. I remember the early counts were below 10,000 bats. However, we were thrilled when we realized that there were babies in the cave, which meant that even though the numbers were small, we had a nursery colony. Each year since then the numbers have increased dramatically and this year after the babies were flying the number reached 121,000.

Louise Allen-Hristova, who is now married to Nick, had also been researching the effects of stress on the growth of young bats. She has finished collecting information for her dissertation, and is now writing it. She will be awarded her Ph.D. soon.

Another doctoral graduate students of Dr. Kunz that has worked on our counts is Jon Reichard, seen above with his wife Jen who is an 8th grade science teacher. That's J. David Bamberger smiling on the right.

The research by Dr. Kunz's team has included counts on many of the Central Texas caves as well as Carlsbad Cave in New Mexico. This has added an important chapter to our knowledge of bats. We certainly thank them for their work here at Bamberger Ranch Preserve, and for their friendship.

Bat Conservation International (BCI), whose headquarters are in Austin, has a great deal of information about bats in Texas that is available to the public, both on line and in books that are for sale from their bookstore, which is also on line. In the months when there are nightly emergences from the Congress Avenue Bridge over Lady Bird Lake, there are specialists from BCI there to tell you about the lives of bats and how important they are to humans. It is a wonderful show, and I recommend that you get out and see it.


Eugenia said...

I'm dying to see the bats one day!! It sounds amazing. Your blog is great, Margaret!

Elizabeth Joy said...

What an interesting blog! I know my son would love to come see your bats. I have a theme going on at my blog on Wildflowers in Winter. If you interested come on over for the details and join the fun.