Alpha Bison: The Quieter Bellow Wins The Females
Megan Wyman has earned the right to call herself a cowgirl; she's spent four summers in the Great Plains of Nebraska, much of it riding in the back of a pickup truck chasing after bison. But it's sound, not trophies, that she's after.
Wyman studies animal communication.
"I am trying to decipher exactly what a sexy, dominant bison male sounds like," she says. "More specifically, I am trying to decode bison bellows."
Wyman wants to know what acoustic qualities — frequency, duration, loudness — mark a male who is, you might say, a bon vivant with the ladies during mating season. Wyman thinks a male bison uses his bellow to defend his female(s) from other males, and also perhaps to influence the female to choose him as a mate.
Just what kind of bellow marks a good mate is still a mystery. Wyman's data suggest that "high quality" bison males bellow more quietly than "low quality" males, which is not what she expected. Wyman, a student at the University of California, Davis, published some of her findings in the November 2008 issue of the journal Animal Behavior.
Besides bellows, bison have a variety of sounds they make; sometimes it's just rapid, noisy breathing, sometimes it's like a motor revving up, and sometimes it's a low rumble. Cows and calves also communicate with each other with soft, short "tonal" calls.
This year, Wyman is headed off to Great Britain and New Zealand to record another species: red deer.
"Amazing sounds," she says. Based on her bison recordings, that's easy to believe.
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STEVE INSKEEP, host:
We have some new wild sounds from our series that let's us listen to the natural world around us. And our source this morning is a graduate student named Megan Wyman. She spent four summers studying an animal that once seemed to be on its way to extinction. She listened to bison in Nebraska, and she studied how male bison established their authority using a variety of grunts and snorts.
(Soundbite of bison snorting)
Ms. MEGAN WYMAN: We would go out everyday in the morning in a open-bed truck and we would drive out into the middle of the bison herd. We (unintelligible) with select bison, and this is a bison who is bellowing. He's either guarding a female or he's challenging another male. And we would start recording. And we'd do this for about 20 to 30 minutes until we feel we have enough bellows to kind of accurately know what sort of information he's giving.
(Soundbite of bison bellowing)
Ms. WYMAN: There's different parts of the call. Some will be long, some will be short, some have higher pitch or lower pitch, some are very grumbly and rough and some are high and wheezy.
(Soundbite of bison snorting)
Ms. WYMAN: Some have flat tones and others move up and down. And each of those is saying something in particular, we think, about the relative strengths or quality or fitness or motivation of that male to fight other males and to gain access and matings to females.
(Soundbite of bison snorting)
Ms. WYMAN: What we just heard there was what we call a bison fighting storm. A female may run through the herd, and when she does this, it attracts the attention of other males. And they'll start following and chasing her and other bison. And then when she stops, these males will stop and they'll start bellowing back and forth and they'll start pawing at the dirt and wallowing in the ground.
(Soundbite of bison bellowing)
Ms. WYMAN: And then they'll start fighting. And what they're trying to do is figure out who's the most dominant male so they can then gain access to the female. And there'll be huge clouds of dust. There'll be males head-butting each other, horning each other, and there'll bison hair flying through the air. It's quite a sight to see.
(Soundbite of bison bellowing)
Ms. WYMAN: It's really amazing. Sometimes they would walk right past us and they'd be within arm's distance away and they're bellowing so loud it hurts your ears. And they're just really majestic and makes me feel like you're part of an ancient world.
(Soundbite of bison bellowing)
INSKEEP: Megan Wyman recorded these wild sounds. NPR's Christopher Joyce brought the series to us, and you can find photos of Wyman's bison at NPR.org.
(Soundbite of music)
INSKEEP: This is NPR News. Transcript provided by NPR, Copyright National Public Radio.
