Most children, at some point in their lives, prefer one parent to another. Sometimes, favourites persist; kids become mummy’s boys, or a daddy’s girls.

A new study of rhesus macaques shows the same can be true for other primates.

When male macaques reach a certain stage in life, they prefer to hang around with their dads, and their dads with them.

They do so, researchers suspect, to help prepare for the itinerant lifestyle many male monkeys are forced to live.

Scientists know that primates often form stronger bonds between one sex over the other. Females, for example, often form closer ties with one another than males.

That was thought to be because females often remain in the groups they were born into, forming bonds with their relatives, whereas males of many primate species leave home when they reach maturity.

But this study, published in the American Journal of Primatology, is one of the first to show that primates form preferential bonds between relations of the same sex before they have even left the group.

Anja Widdig, Doreen Langos and Lars Kulik of the Max-Planck Institute for Evolutionary Anthropology in Leipzig, Germany studied rhesus macaques living wild on the island of Cayo Santiago, off Puerto Rico.

Rhesus macaques usually live across Asia, but a few were introduced to Cayo Santiago 75 years ago, and have lived wild there since, with scientists taking regular censuses of the group since 1956. That allowed Anja Widdig and colleagues to identify each monkey individually and record who spent time with who, and which monkeys were genetically related.

They found that young monkeys had an equal opportunity to mingle and interact with either parent when growing up. As they were developing, infant monkeys of both sex spent most of their social time with their mothers and her relatives. That isn’t surprising, as mothers tend to spend most time with their young after weaning, so the juveniles become more familiar with her and her relatives.

Young female monkeys formed particularly strong bonds with their female relatives.

But at the point of maturation, when infant monkeys develop into young adult monkeys, males very much became their fathers’ sons; preferring to spend time with their fathers and his relatives.

The young monkeys spent more time in this adult male company, grooming their fathers, brothers and cousins, and visa versa.

It is still not clear exactly why the young male monkeys do this; one idea is that it helps prepare the young males for later life.

Or it may allow them to form bonds with other male monkeys who will leave the group at a similar time. By becoming friendly, these males might be useful to one another as they try to establish themselves elsewhere.