Hanging out with the right dolphins

The friends we make when we’re young can potentially have significant effects on later life. Think back, did the children you hung out with at school lead you into difficult situations? Did friends of your parents have any impact on you at all? Did the things you learn in the playground help you in later life?

Your answers may vary, but it is likely there are some important social lessons you learnt from these early days that have affected your adult life.

The same is true of other socially complex, long lived species. Like humans, these species possess large, metabolically expensive brains, which require large amounts of time to develop. This leads the young of socially complex animals taking a longer time to mature than less socially complex animals.

There have been several studies on how social interactions during adulthood such as alliances and other long term social relationships can have significant effects on many aspects of such an animal’s life, such as survival, social dominance or reproduction. Far fewer studies have looked at the effect of socialising during development can have on later life.

Recently a long term study of bottlenose dolphins in Shark Bay, Australia, has demonstrated how the social interactions of calves can have significant effects on their survival into adulthood. Bottlenose dolphins are a useful species for such a study for a variety of reasons. Firstly they take a while to reach adulthood, drinking their mother’s milk until they are about four years old and not becoming sexually mature until about 10 – 15 years old. Once a calf has been weaned, they must fend for themselves. They do however, remain in the general area where they are born, leading to lifelong connections.

Researchers have been carrying out boat based observations of groups of dolphins in Shark Bay since 1984 and can identify individuals by marks on their body and dorsal fin. This particular analysis produced some interesting results.

This early sociality likely helps males prepare for later life by developing their social skills in a lower risk environment. It also allows them to make alliances that may be useful in later life. Since adult female bottlenoses do not form alliances, sociality has no effect on their likelihood of survival.

However, male calves which socialised a lot with older juvenile males after weaning were found to have a far lower probability of survival. It is likely that these older males are source of stress for younger males, harassing and intimidating them. This reduces the likelihood of having to compete with them for resources and mates in later life.

These results demonstrate how early socialising in males can provide them with benefits in later life, either through competitive advantages or by allowing them to learn useful life skills. Bottlenose dolphins must spend the first ten years of their life in a potentially difficult social environment before they can reproduce.

Learning how to deal with all its complexities is vital for an individual’s survival. The authors of this study show that scientists interested in animal sociality must examine all stages of its life history in order to understand how its effects. It also shows the value of tools such as the construction of social networks for such work.

Reference: Early Social Networks Predict Survival in Wild Bottlenose Dolphins www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0047508

Image Credits: Wikimedia commons

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