Male dolphins build complex teams for social success

Mar 28, 2012

(PhysOrg.com) -- Male dolphins not only form a series of complex alliances based on their close relatives and friends but these alliances also form a shifting mosaic of overlapping geographic ranges within in an open social network, says a new study published in the journal Proceedings of the Royal Society B.

The study of in Shark Bay, , was led by Srdan Randic, a Master's student at the University of Massachusetts  and supervised by Richard Connor, a Research Fellow at the UNSW Ecology and Evolution Research Centre. The team includes UNSW geneticist Dr Bill Sherwin and Michael Krutzen, a UNSW alumnus now at the University of Zurich.

Male dolphins use physical contact - petting and rubbing each other – to cement their personal bonds. Earlier studies had shown that the Shark Bay dolphins form three different kinds of alliances, but the study shows that they also enjoy a unique combination of “nested” male alliances within an open social network - a pattern not described before in comparable animals or dolphin communities.

Groups of two to three males form “first-order” alliances that involve close relatives, such as cousins, co-operating to guard or act as consorts to females. Long-running studies by many researchers at Shark Bay have revealed that these small groups may persist for up to 20 years.

“Sometimes one of these first-order alliances is seen to assist another to gain access to a female, but on another day the same two groups may be opposed in a contest over a female,” says Sherwin.

Teams of four to 14 males cooperate in “second-order” alliances to attack other alliances and to defend against such attacks. Second-order alliances can persist intact for over 15 years and may be considered the core unit of male social organization in Shark Bay, the researchers say.

Finally, two or more “second-order” groups may team up from time to time to form a “third-order” alliance. The study tackled the question of how they choose to make these alliances.

Randic’s team was able to exclude the so-called “community defence model” used by chimpanzees, for example, in which semi-closed communities (ones that occasionally accept new members emigrating from other groups) are defended by males ranging across their group’s entire range.

Nor do they follow the “mating season defence model”, where males defend a tighter geographic range only in the mating season. At such times, the range of one male alliance would have little overlap with others but would have considerable overlap with the range of certain female individuals, notes Sherwin.

But the study found that even the largest dolphin alliances do not do this. The key difference with comparable species seems to be that they have an open social network, with a fission–fusion grouping pattern with strongly differentiated relationships, including nested male alliances.

“We have now shown that males, like females, exhibit a continual mosaic of overlapping ranges,” says Connor. “Humans, elephants and other mammals live in semi-closed groups with sex-biased dispersal but have relationships with other groups. So humans and elephants differ from the in that key respect of living in semi-closed groups, but have in common a nested relationship structure.

“All three have unusually low costs of locomotion, which would have allowed larger ranges, leading to interactions with larger numbers of individuals and groups, further complicating their social lives.”

Explore further: Male monkey filmed caring for dying mate (w/ Video)

Related Stories

Fighting for their attention

Apr 04, 2007

Mating strategies are straightforward in bottlenose dolphins, or are they? Much of the work carried on male-female relationships in that species to date show that males tend to coerce females who are left with ...

For male weta, big is better

Nov 18, 2011

(PhysOrg.com) -- For a male tree weta, size really is everything. In six of the seven species in New Zealand the males all sport a distinctly large head, and the bigger the head, the better the chance of mating.

Dating drought or purple patch? How males choose mates

Oct 11, 2011

(PhysOrg.com) -- Males decide how much effort they put into courtship and which females to court based on how many others they have recently encountered and how attractive they were, according to a new study into the mating ...

Recommended for you

Male monkey filmed caring for dying mate (w/ Video)

23 hours ago

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Orchid named after UC Riverside researcher

Apr 17, 2014

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

Apr 17, 2014

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

Apr 17, 2014

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 0

More news stories

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Male monkey filmed caring for dying mate (w/ Video)

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Researchers develop new model of cellular movement

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

Health care site flagged in Heartbleed review

People with accounts on the enrollment website for President Barack Obama's signature health care law are being told to change their passwords following an administration-wide review of the government's vulnerability to the ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.