John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
More than a dozen colonies were spotted propagating like thunderstorms.
OK, not that bat signal. But radar did detect the presence of more than a dozen bat “storms” Monday, as thousands of the creatures flapped into the night to hoover up hairy, delicious bugs.
“The Bat Signal is strong tonight!” writes the National Weather Service’s office in Austin/San Antonio. “Each Orange circle shows an area where bats can be seen on radar tonight.”
Summer is bat season in Texas, with millions of the creatures flocking there for warm-weather hunting. While the populations at Austin’s Congress Avenue Bridge and San Antonio’s Bracken Cave are legendary—the latter’s thought to hold the world’s biggest clump of bats, with some 15 million creatures—this radar footage reveals many other colonies, each represented by a circle. (There’s also a miniature one in Austin’s airport.) The weather service offers up more on why they appear on radar, and how meteorologists distinguish them from rain:
[S]ome nights they show up better depending on how sensitive our radar is, or whether the bats slowly come out or come out all at once.
The fact that the returns are short lived and only show up on the lowest level of our radar scan are two big factors. Showers and storms tend to be tall so we see those on multiple radar levels. Also the distinct doughnut shape is another thing we watch for. We know that is bats.
Folks skeeved out at the thought of sky-darkening tsunamis of bats should remember that, without them, they might be covered in writhing bodysuits of mosquitoes. The horde living in the Bracken hole, for instance, consumes an estimated 140 tons of insects each summer night—the weight equivalent of nearly five adult gray whales.