Can you hear me now? Turns out the communication between members of one bat species is breaking up.
Large-eared horseshoe bats, Rhinolophus philippinensis (RINE-oh-LOW-fus FILL-uh-pin-EN-sus), come in three sizes. "[Each size bat] calls out using different notes," says Tigga Kingston, a biologist at Boston University. Bigger bats produce lower-pitch (how high or low a note sounds) whistles.
The bats may have developed their distinct notes to avoid food competition, says Kingston. That's because bats use echolocation to pinpoint food. The sound waves (vibrating energy waves) created by their calls bounce off prey and echo back to the bat. The large bats' whistles have long wavelengths (distance between a wave's peaks) that only bounce off jumbo insects. On the other hand, the smaller bats' short-wavelength calls hone in on smaller snacks.
The problem? Bats also whistle to communicate. Scientists suspect the animals tune out calls with a pitch unlike their own. That means two different-size bats don't connect and won't mate with each other. Result: The genes (units of hereditary material) carried by bats of different sizes won't mix in future generations. Eventually, the three sizes of bats may become so distinct that they'll be classified as separate species. Now that's a bad connection.
A note's pitch depends on the sound wave's frequency (number of vibrations per second). So each size bat calls in a different frequency. Use the article and graph to determine if a low-pitch sound has a high or low frequency.