National Geographic Grantee Whitney Friedman is studying some of the smartest creatures in the sea- dolphins. Their complex alliances and social interactions may be more similar to humans than any other species. Follow her expedition on Explorers Journal as she joins a 30-year study on male alliances among bottlenose dolphins in Western Australia’s Shark Bay.
The Journey to Shark Bay
It’s sunrise somewhere over the Pacific ocean. At almost midnight 14 hours ago, I departed from Los Angeles International Airport. I never quite get over the bizzare effect of crossing the international date line: its been pitch black since we departed, and this year, the 6th of August will never occur for the passengers aboard this plane.
My destination: Shark Bay, Western Australia. It takes a minimum of 35 hours of direct travel to arrive at this remote destination half-way around the world from where I began. But the destination is well worth the long journey. In addition to the 24 species of sharks, 10000 dugongs, 300+ species of fish, and many more animals that inhabit the UNESCO World-Heritage site, Shark Bay is home to a resident population of bottlenose dolphins currently estimated at about 5,000 individuals.
An international team of researchers have studied the dolphins since the early 1980s when the research was spearheaded by an ambitious duo of then-recent university graduates, Richard Connor and Rachel Smolker. This will be my fourth year joining Dr. Connor’s team to study the social relationships among these resident dolphins; in particular among the adult males.
Nested Alliances of Bottlenose Dolphins
Over the last thirty years, Connor and his colleagues have uncovered a “nested” alliance structure among adult males in this population whose complexity is likely more similar to that of humans than to any well-studied mammal – terrestrial or aquatic.
Especially during the mating season in Shark Bay (beginning in just a few weeks!) male bottlenose dolphins form pairs or trios to ‘consort’ individual adult females. Estrus females are a limited resource during the mating season, and encounter rates among males are frequent in this dense population. This recipe is thought to contribute to frequent conflicts among the males.
But rather than keeping the fight between each pair or trio of males, when fights erupt other males porpoise in from afar to join – and they take consistent sides. You see, in addition to belonging to a pair or trio (sometimes stable for over 20 years!) most males also belong to a “second-order” alliance — a group of up to 14 males that have also been found to persist for nearly two decades. These males work together during such mating competitions to aid in the defense or theft of estrus females from males in other second-order alliances.
As if this wasn’t complex enough, we also find examples of second-order alliances that spend time together and occasionally join forces against other groups. That’s right: a third level of alliance!
An ‘Open’ Social Network
These alliances reside within a huge “open” social network of bottlenose dolphins that stretches over the ecologically diverse Eastern and Western Gulf of Shark Bay. The variable underwater microhabitats of flats, channels, and gradually sloping embayment plains support different species of fish, and though the dolphins share general foraging tactics, many also have specialized foraging tactics particular to the region of they bay in which they spend most of their time.
These specializations are thought to contribute to a network of overlapping but relatively stable homeranges for groups of male and female dolphins. This gives researchers in Shark Bay a very unique opportunity to reliably seek out particular individuals among a free-ranging population of cetaceans; if we want to find the group of six males we call “The Crunch Bunch” we know to look around an area east of our research base.
This exciting combination: nested alliances within a mosaic of overlapping home-ranges, in which neighboring groups often forage together one day and compete the next, and the accessibility of this near-shore population makes this site one of the most unique and exciting places to study the social lives of this fascinating non-human species.
Meet the Boys
This season I’ll be focusing on how the males within two “second-order” alliances – the “Primas” and the “Krokers” – establish and maintain their relationships. These two groups have been studied since the mid-90’s, when the two young alliances formed. We find these two alliances frequently as they inhabit the channel just offshore of our research base at Monkey Mia, WA.
The Primas and Krokers represent extremes of second-order stability: since their formation in the mid-90s the Primas have consisted of two stable trios who consort females almost exclusively within these trios. The Primas also have an occassional 7th member, “Barney”, who rarely seems to make his way into consortships. The geographically-related Krokers have fluctuated in group size from a maximum of 14 to the current low of 10 individuals. They tend to form more stable pairs, but consort females in trios – often meaning a rotating third individual.
The Krokers and Primas are often found together in social and foraging situations, and have been seen to work together during mate competition – pegging them one of best groups to study to further understand the making of 3rd order associations.