AUSTIN, Texas (Reuters) - A drought in the state of Texas, where 1.5 million bats are living under a bridge in the city of Austin, has fueled a bat frenzy with locals gathering each night to view the nocturnal creatures.
The drought has destroyed crops in Texas and killed delicious pests that the Mexican free-tailed bats eat.
The lack of food means the bats leave home earlier than usual each night to find nourishment -- giving the locals more time to watch the normally-nocturnal critters fly before the sun goes down.
Each night they stream from under a bridge by the hundreds of thousands in a black cloud so large that it shows up on local weather radar.
"It's wonderful for people to be able to see them, and they are really spectacular," said James Eggers, director of education for the Austin-based Bat Conservation International. "But it's an indicator that things are a little tougher for the bats."
But naturalists do not see any negative long-term effects if the drought ends soon.
"If we just have one to two years of drought, it's a natural cycle and it's not going to affect the species as a whole," Eggers said. "What some scientists fear is that this is not a regular drought, but could be indicative of change coming because of global warming. If we have an extended drought for many years, that could affect the population of the Mexican free-tails."
An extended drought could be a double whammy for central Texas farmers, who depend on the bats to remove some 1,000 tons of insects and pests from the air each night.
A study in 2006 showed that area cotton farming, which was a $4.5 million-a-year industry at the time, saved some $750,000 a year from pestilence thanks to the Mexican free tails.
Experts say about 100 million bats live in Central Texas. The largest bat colony in the world, about 20 million, resides in a cave northwest of San Antonio. The Mexican free-tails summer in central Texas and winter in Mexico.
Around March, about 750,000 pregnant females come to downtown Austin and nest under the Congress Street bridge, just blocks from the governor's mansion.
A few months later, they have their babies and their numbers double to 1.5 million. The nightly spectacle, which draws visitors from all over the world, lasts through about October, when the bats return to Mexico.
The bats moved into Austin in the 1980s when the bridge, then 70 years old, was reinforced with beams that surprisingly turned out to be a perfect habitat for them.
After initial resistance Austin now welcomes the creatures. There is a huge bat sculpture next to downtown. The Official Drink of Austin is the Bat-ini and the bat conservation group moved its headquarters from Milwaukee to Austin.
The Texas Department of Transportation works closely with Eggers' group to adapt new bridges and roadways across Texas to attract bats.
In Austin alone, the bats bring in some $8 million from eco-tourism.
"The bats are our unofficial mascot," Austin resident Susan Floyd said. "Their return each spring marks the beginning of festival season. And, they're weird. Just like Austin. "
Editing by Greg McCune and Patricia Reaney