Dolphins form largest alliance ever found

The development of alliances was a behavioural leap forward that helped humans become the dominant species on earth. Alliances are not uncommon in nature, occurring in lions, horses and primates such as chimpanzees. However, a much more rare occurrence is a step above simple alliances, which is to say alliances with other alliances. For a long time, this method of sharing and communicating was thought to be unique to humans - something that put us above the rest of the animal kingdom. However, a recent study has found that one other group of animals is now displaying this behaviour: the population of bottlenose dolphins in Shark Bay, Australia. Will Tingle has been talking to Stephanie King, of the University of Bristol, and Richard Connor, of the University of Massachusetts at Dartmouth, about why these alliances need to exist, and how they may have come about.

Stephanie - As a male dolphin in Shark Bay, what's really important is to find females to mate with so you can have lots of offspring, you can pass on your genes. But it's a population where there are lots of animals, right? So the density's really high. It's a big population. And each year there are only a few females available to have offspring because many of them already have calfs that they tend to look after for a number of years before that calf becomes independent. And so you have all these males competing for just a few females. So as a male dolphin, in order to get access to females, you need to form these alliances. You need to work together to find females that are ready to have offspring, to mate with. You need to keep that female with you, and you may need to impress her to mate with you. But to do that, you have to work together. You have to work with other males in order to secure access to that female and to defend her if rival alliances come in, rival males come in, and try to take her. And as a male dolphin in Shark Bay, if you are not in an Alliance, then you secure few, if any paternity. So you sire few, if any, offspring

Will - And this, as you say, is remarkably complex behavior. Do you think there are environmental factors behind the development of this or did it just sort of happen?

Richard - Well as Stephanie was saying, there is a very high density here and it may be as simple as, if you're going to run into your enemies you better be with your friends. So they have these pairs and trios. They go around, the males, go around in pairs and trios to form these consortships with individual females. But that's not enough for them because two pairs or trios can take a female from them. So they have these second order alliances of four to 14 males that we've learned over the years are the core social unit of the male dolphins. They're basically lifelong commitments and it's within these groups that they formed the pairs and trios. And then the more recent discovery is that these second order alliances have relationships with other second order alliances to form third order alliances, and then males bonds with their third order allies are really important for their success.

斯蒂芬妮- - -这是一群之间,这是tween alliance cooperation, that's so interesting and so exciting because typically in the animal kingdom social birds and mammals will interact within their groups, and interactions between groups are hostile. So you are in competition with other groups and the interactions between groups are competitive. There is conflict, they are hostile. And yet here, we're seeing that the dolphins in Shark Bay are behaving strategically while it's in their benefit to form these cooperative relationships with other alliances. So we have this between group cooperation, and that is something that we only see in our own society, so in humans.

Will - Is there something about Shark Bay that allows these dolphins to develop their behavior?

Richard - There's two reasons probably that the dolphin society here is so much more complex than other places where they've studied bottlenose dolphins inshore. So Shark Bay is really a marine biologist paradise. It has the largest seagrass beds in the world and those seagrass beds support a lot of everything. We see tons of dugongs out there, lots of sea turtles, and lots of dolphins. That combined with their slightly smaller size means that again, they're a higher density. And so they're bumping into each other a lot and they need to maintain these complex relationships. And so if there is damage to those seagrass beds from climate change events, yeah I mean we'd hate to watch this incredible society become simplified and see the damage to the bay over the next few decades

Stephanie - Protect your marine sea grasses, protect your marine environment.