ScienceShot: What's That? Climate Change Could Stifle Bat Chirps
As the planet warms, some bats will find it harder to locate and track their airborne prey, a new study suggests. The distance that sound travels before it becomes too weak to hear depends on a number of factors, including its frequency and the temperature and humidity of the air: In general, higher frequencies are more quickly stifled in warmer air. Researchers estimate that if air temperature rises 4°C—an increase within the range estimated by some climate models during the 21st century—the volume of space in which tropical bats can effectively find and track prey may decrease as much as 10%. For echolocating bats living in temperate ecosystems, prey detection volume might shrink as much as 21%, the researchers report online today in the Journal of the Royal Society Interface. To compensate for these losses, bats could either chirp louder, chirp at a lower frequency, or forage for longer periods each day—changes in behavior that would likely impose substantial costs. But temperature isn't the only climatic factor affecting the attenuation of sound, the researchers note. A complex interaction of call frequency, temperature, and humidity determines how far the sound waves travel before they're squelched. So while many bats will find life more difficult in a warmer world, some—those that echolocate at frequencies below 35 kilohertz in temperate ecosystems and below 95 kHz in the tropics—will find they can locate and home in on prey across a larger volume of space. With some of the winged predators being winners in the climate change lottery and others ending up losers, the balance of bat species in some ecosystems could shift significantly.