LEILA FADEL, HOST:
Sharks have a reputation among humans for being terrifying.
(SOUNDBITE OF JOHN WILLIAMS' THEME FROM "JAWS")
FADEL: But a new study on shark behavior reveals that they might have an affinity for one another.
JUERG BRUNNSCHWEILER: Which many people would say - if you ask them, are sharks social, they would say, probably not; I don't think so. Why would they? But why wouldn't they be?
FADEL: It's a question that Juerg Brunnschweiler wanted to answer when he first started studying sharks 20 years ago.
BRUNNSCHWEILER: There was this rumor of bull sharks turning up and swimming around together in pairs.
FADEL: Bull sharks are known to be one of the most aggressive species and responsible for the majority of nearshore attacks. But he suspected that there might be a softer side to this pugnacious aquatic predator. So he observed them up close in Fiji.
BRUNNSCHWEILER: Open, free dives - no cages. We never use cages. Two dives on a day in the morning. So you go out. You typically jump into the water at 9 o'clock. And then you start feeding, the sharks are coming in. You do a 35-minute-to-40-minute dive. Then you go up on the boat. You do a one-hour surface interval. You go back down, a second dive at the very same site. You do feeding again.
FADEL: And he said it got interesting sometimes.
BRUNNSCHWEILER: Some of these sharks really have a very strong personality. And they're sneaky, and they maybe try to get a piece of food which - you know, coming from behind and try to sneak in and, you know, bump you slightly and in a gentle way. One of the sharks would actually grab the pole and, you know, drag it away - or the bin with the fish in it.
FADEL: After 20 years of diving and observing the same 100 sharks, he also noticed something.
BRUNNSCHWEILER: If we see certain pairs or group of individuals, they show up together with the same specimen, then you could say that there's something going on. They maybe move around together, or it's not random.
FADEL: While Brunnschweiler won't call it friendship, he's confident the sharks are social creatures. And his ultimate goal is to change perceptions and fears around sharks. Transcript provided by NPR, Copyright NPR.