Cichlid Male Nannies Help Out, Especially If They've Been Sneaking

ScienceDaily (Oct. 12, 2011) — Subordinate male cichlid fish who help with the childcare for the dominant breeding pair are occasionally actually the fathers of some of the offspring they help to rear, according to new research from the University of Bristol published in the online journal PLoS ONE. This sneaky paternity increases the subordinate fish's investment in the offspring in their care.

The highly social cichlid fish Neolamprologus pulcher, endemic to Lake Tanganyika in Africa, live in social groups consisting of a dominant breeding pair and between 1 and 15 subordinates of both sexes that perform brood care, territory defence and maintenance. Subordinates are often distantly related or unrelated to the dominants.

Cooperative breeding of this kind has puzzled evolutionary biologists for a long time as it is costly and often does not generate obvious fitness benefits to subordinates. In the case of N. pulcher, the main benefit for subordinates to stay in a territory of dominant breeders seems to be the protection gained against predators provided by the large group members.

Previously, it was assumed that male subordinates never achieved paternity but the Bristol researchers suspected that, due to low relatedness between dominants and subordinates, mature male subordinates would attempt to father offspring and that achieving paternity would increase their helping behaviour.
The team, led by Dr Rick Bruintjes, tested this theory by studying groups of cichlids at Kasakalawe Point, Zambia and found that while dominant females were the mothers of 99.7 per cent of all offspring, the dominant males only sired 88.8 per cent. Subordinate females did not participate in reproduction, but male subordinates successfully gained paternity in 27.8 per cent of all clutches.
Furthermore, subordinate males that sired offspring defended more rigorously against egg predators compared to similar males that did not sire offspring, and they also tended to stay closer to the breeding shelter.

The study shows that the cooperative behaviour of the subordinate male fish has a direct fitness benefit for them -- that is, producing their own offspring -- as well as such indirect benefits as safety.
Dr Bruintjes said: "This is the first evidence in a cooperatively breeding fish species that the helping effort of male subordinates may depend on obtained paternity, which stresses the need to consider direct fitness benefits in evolutionary studies of helping behaviour."

http://www.sciencedaily.com/releases/2011/10/111012185628.htm

Sperm whales: the 12-metre-long babysitters

Underwater mammals in the waters of Azores solve their childcare issues in a spirit of mutual cooperation

Sperm whales may be the biggest predators that ever lived, but they have childcare issues too. The solution? A very big babysitter.


Here in the Azores, where I've spent the past two weeks diving with sperm whales off the island of Pico, a resident population of these remarkable mammals search for their main source of food: squid.

While the sperm whale is a natural submarine, able to dive a mile in depth for up to two hours, young calves still suckling their mother's milk (which is 60% fat, with the consistency of cottage cheese) cannot undertake such deep plunges. So while their mothers hunt for food, calves are cared for communally in what amounts to a cetacean creche. This accompanying image, taken by the accomplished underwater photographer Andrew Sutton, shows whale altruism in action. Only one of the four juveniles with this large female is hers; she may not even be genetically connected to the others.

João Quaresma of Espaco Talassa, our Azorean skipper, told me that to see four young with one female is unusual. "Calves start to feed themselves at around three or four years," he says, "but they've found whales up to the age of nine still suckling." Studies by scientists such as Dr Hal Whitehead of Nova Scotia University have shown that sperm whales organise themselves in highly complex societies, communicating in discrete dialects of sonar clicks, passing on culture learned matrilineally. Such behaviour reinforces what we are beginning to discover about the intelligence of these whales, which possess the largest brain of any animal.

Operating under special licence from the Azorean government which determines strict care for the whales' welfare, Andrew and I snorkelled with this group, watching them silently twisting and turning around one another in a physical expression of social solidarity. It was a salutary moment. In the 20th century, our species came close to driving the great whales to extinction. This week, the International Whaling Commission meets in Jersey to decide the fate of cetaceans around the world. Conservationists hope that they'll make the right decisions. Sometimes whales need more than a babysitter to help them – even when she's 12 metres long.

Philip Hoare

guardian.co.uk, Sunday 10 July 2011 19.59 BST

http://www.guardian.co.uk/theguardian/2011/jul/10/azores-whales-cooperative-childcare