Oct. 29, 2004 — Male bats with a natural talent for singing attract more female admirers, and some males and females even sing in secret, using sounds that are inaudible to humans and to other animals, two new studies of bats reveal.

The studies, both published recently in the journal Animal Behavior, reveal that bat communication systems, as well as their social lives, are far more complex than thought.

For the first study, biologists Susan Davidson and Gerald Wilkinson of the University of Maryland analyzed songs and other sounds produced by greater white-lined bats, Saccopteryx bilineata, located in Trinidad, in the West Indies. They also videotaped these bats in the wild to see how their calls and songs might influence behavior.

Greater white-lined male bats sing what the researchers refer to as bat "love songs." Female bats of the species just produce short calls.

Davidson and Wilkinson first determined that male songs consist of separate sounds, or mini tunes, within the overall vocalization. They classified these songs as being screechy, whiny, a combo screech-whine, short repeated notes, and long tonal sounds with some harmonics.

The scientists found that males singing to other males tended to screech, probably to define territory. Males interacting with females, however, produced longer, more tonal calls, reminiscent of the sounds that baby bats make.

The researchers say the baby link probably means the male bats are trying to soothe and to appease, which apparently is very attractive to a female bat, judging by the large following of female bats roosting in trees near talented male singers.

"Males differ in the complexity of songs they produce, and males with more complex songs have more females in their territories," Wilkinson told Discovery News. "A similar result has been observed for many birds in that individuals with larger repertoires attract more females. We are suggesting that differences in some aspect of male quality permits males to sing more complex repertoires."

For the second study, researchers Karry Kazial and W. Mitchell Masters recorded echolocation signals, above the human range of hearing, emitted by big brown bats, Eptesicus fuscus, which were caught on or near the campus of Ohio State University.

While prior research suggested bat sonar calls only were used for echolocation purposes, Kazial and Masters found that female bats who listened to both female and male ultrasonic sounds could distinguish, from the noise alone, whether the call was coming from a male or a female.

Whenever females heard sonar sounds from another female, they would call less frequently, likely to tune in to what the other female was communicating. According to the researchers, female bats interact mainly with other females in complex hierarchies during their lives, so that could be why they take more of an interest in echolocation sounds from their own sex.

However, the researchers also speculated that the sound of another female simply wasn't as exciting as listening to a male.

Kazial, assistant professor of biology at SUNY at Fredonia, agrees with the findings of the greater white-lined bat study.

She told Discovery News, "The connection of the two studies is in the idea that bat communication is more complex than previously documented, since research is finding a variety of social calls to be communicating territory defense and mate attraction, as well as sonar calls, previously thought to only function in prey capture and navigation, to also have a communication role."

She added, "Bats are very interesting animals that we continue to learn more about, and they should not be perceived as scary or pests. There are many unfortunate myths regarding bats. Bats, in general, provide many benefits to humans, including their consumption of insects, pollination of plants, and seed dispersal."