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 NPR.