NIGHT FLYING MISSIONS VS MEXICAN FREE-TAILED BATS - Twenty million tiny bats living 11 miles from Randolph pose a giant risk to base aircraft

  • Published
  • By Alex Salinas
  • 12th Flying Training Wing Public Affairs at Joint-Base San Antonio-Randolph, Texas
Located about 11 miles northwest of Joint Base San Antonio-Randolph, Texas, is the true "bat cave." Bracken Cave nests millions of migratory Mexican free-tailed bats from March to October and is the largest bat and mammalian colony on earth. The majority of the bats in Bracken Cave are females nursing their babies, so every evening during these months they emerge between 6 and 8 p.m. to feed. Because of the sheer volume of these tiny winged creatures, base training aircraft can find themselves battling the bats for airspace.

The bats, flying southeast, are on a collision course with bugs like cotton bollworm moths and army cut-worm moths being pushed from crops southwest by winds, according to Mike Pacheco, U.S. Department of Agriculture wildlife biologist for Randolph.

During fiscal 2013, Randolph reported six bat strikes occurred during flights, according to Air Education and Training Command's Flight Safety Division. That followed zero in 2012 and nine in 2011. Because the incidents were single-body collisions, the aircraft did not experience significant damage, AETC safety said. This is partly because of Randolph's limited scheduling of nighttime flights -- when the bats are most prevalent.

Maj. Kevin Douglas, 12th Flying Training Wing flight safety officer, said flying ceases on base at 5:30 p.m. except for the T-1 Jayhawk, which is the only aircraft with a nighttime flying requirement.

Under 12th FTW Instruction 13-204, a local flying regulation, bat procedures are implemented one hour prior to sunset and 30 minutes after sunrise from April 1 to Oct. 31 -- ironically ending the day after Halloween.

The procedures essentially help serve as a real-time warning system for airborne pilots.

However, the bats at Bracken Cave are not the only reason why Randolph does not operate a large flying mission during the night, but research that began more than four decades ago contributed to that decision.

In 1974, the flight safety office determined that sharing the surrounding airspace with bats was best suited for the Randolph flying mission, said Dr. Larry Guzy, a professor at State University of New York at Oneonta.

During the early 1970s, Guzy assisted an animal behavior expert named Leonard Ireland, then an assistant professor at Oakland University with a doctorate in psychology, who helped establish a Randolph bat avoidance program in 1971.

Guzy and Ireland joined forces to study the bats at Bracken Cave and their effect on night mission training with T-37 Tweets and T-38 Talons after initial research was conducted by Ireland.

In a manuscript published in 1973 titled "The Bat Hazard to U.S. Air Force Aircraft," Ireland and his colleague, Timothy Williams, chronicled their experiments that led to the initiation of the bat avoidance program.

"It wasn't until the safety officer at Randolph mailed an unknown sample of remains from a plane to Tim Williams at the Smithsonian that he realized it was fur belonging to a bat and not a bird," Guzy said.

Their first observations began Oct. 20, 1967.

"During the summer of 1968, evening pilot training flight patterns at Randolph were altered to avoid the immediate areas of large bat roosts," the manuscript stated. "In August 1971, we initiated a bat avoidance program based on real-time radar observations."

Observations of bat flights from Bracken Cave were made with the ASR-6 search radar at the San Antonio International Airport and with the FPS-77 weather radar at Randolph, the report confirmed.

"When ... activity was first noted on the search radar, the radar operator informed both the T-38 flying safety officer at Randolph and the operator of the weather radar of the position and size of the bat flight by telephone," the document stated. "The weather radar operator determined, if possible, the maximum and minimum altitudes of the bat flight and reported this information to flight safety."

Each year from 1967-1971, the average number of bat strikes that occurred was 31, which were responsible for 80 percent of summer nighttime strikes.

Ultimately, the research in the report concluded that the bat avoidance program was "partially effective" -- 16 bat strikes were reported at Randolph in the summer of 1972 and 19 bat strikes were reported during the summer of 1973, a statistically significant decrease from the average number of strikes recorded previously.

Despite radar technology, a part of the Mexican free-tailed bat's lifestyle still baffles experts.

"In 1974, we found, as previously identified, that the bats' flying behavior was too unpredictable to be able to identify a pattern that was safe for night training missions," Guzy said. "One problem that we still have is not knowing how many bats in the air does it take to obtain a radar return."

Thus, the decision to share airspace was made.

The aircraft most susceptible was the T-38, which "flew during the day and the bats flew at night," Guzy said.

Guzy also provided a copy of a Wingspread article dated July 18, 1974.

The article, titled "'Batman' Comes to Randolph," reported how Ireland -- dubbed "Batman" -- and Guzy's research on Bracken Cave was pertinent to the flying mission.
The article also explained the importance of the bats' presence to the surrounding area, and a reason why getting rid of them to make way for airspace would be a bad idea. The millions of bats that emerge from the cave eat several tons of insects per night, the article stated.

Based on research in 2006, this produces savings of about $740,000 to cotton farmers in south central Texas, specifically in the Winter Garden area, whose crops would otherwise be damaged by the presence of too many moths, said Bob Locke, Bat Conservation International director of publications.

The cotton crop area is worth $5.5 million.

Nationwide, bats save farmers $3.8 billion per year in potential crop damages and pesticides farmers do not have to use, said Fran Hutchins, BCI Bracken Cave coordinator.

The only real concern regarding flying is the times when the bats leave and enter the cave, Pacheco said.

From a spectator's viewpoint, the bats, which leave in groups and not all at once, travel in lines resembling a serpentine shape.

Locke said that an oft-used estimate of the number of bats in the Bracken Cave roost is 20 million, but no one knows the exact figure because there are not any current reliable methods to count the bats.

Ireland remarked at the sight in 1974.

"Often we see clouds 30 miles long and 20 miles wide coming out of Bracken," he said.

Fast forward 38 years from the exploits of "Batman," Pacheco commented on his role in the bird air strike hazard program on base and how the program pays homage to separate research undertaken by Guzy on bird strikes in 1973, as well as to the original bat avoidance program.