Cross-species adoption in wild animals is very rare but that’s not to say it never happens.
The instinct to reject any baby other than the mother’s own is strong, even in animals of the same species. But occasionally, for unknown reasons, a strange bonding will occur.
There is a theory posed by evolutionary biologist Richard Dawkins, known as ‘the selfish gene’, that says all actions in nature stem from genes attempting to replicate themselves.
So animals will, above all, protect themselves and their immediate relatives, rather than exhibiting generosity towards a creature not of their kind.
Not everyone agrees with this theory and examples of one animal adopting quite a different species add weight to genes not being the only driver in animal behaviour.
In 2014, scientists studying bottlenose dolphins in the waters of French Polynesia noticed an odd-looking calf in one particular pod. A closer look proved the youngster to be a baby melon-headed whale, happily swimming and interacting with the bottlenoses, being looked after and protected by the pod.
It stuck close to one mother, who also had her own calf, and it was even seen to suckle from her. The young melon-head stayed with the pod for three years, until it was old enough to fend for itself.
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The researchers believe the orphaned cetacean turned up at exactly the right time to be caught up by the mother dolphin’s strong maternal instincts following the birth of her calf.
They also think the determination of the melon-head to ‘become’ a bottlenose and adopt their forms of play and other behaviours helped it to become accepted by them as a legitimate member of the group.
Another scientifically documented case of inter-species adoption occurred in 2004 in Brazil. Members of the Department of Experimental Psychology at the University of São Paulo observed a marmoset infant within a troop of wild capuchin monkeys.
The baby appeared to have been fully accepted by the group and was looked after by two of the females, being fed and groomed with the capuchin youngsters. This is doubly unique because marmosets, alongside other very small monkey types, are usually on the menu for capuchins.
Does intraspecies adoption exist?
Much more common than one species adopting the young of another – though still a bit of a rarity in the wild – is a mother adopting a youngster born to another mother of the same species.
Animal mothers generally favour only the baby they gave birth to and will reject all others. Sometimes, though, a mother will accept responsibility for someone else’s offspring, if the conditions are right.
This happens more often in domesticated animals – a sheep can be persuaded to take on an orphaned lamb, for instance – but it can also happen in nature.
In December 2025, researchers who had tagged a young polar bear, the single cub born to its mother, were surprised to see a second, untagged cub suddenly accompanying the two.
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That the mother had taken on its care when it was either abandoned or lost its birth mother was a partial disproving of ‘the selfish gene’. The fact they were the same species, however, supports the theory that survival of that species as a whole also plays a part in animal motivation.
Northern elephant seals off the coast of California are regularly battered by stormy seas and lose contact with their young in the turbulent waters. In many cases, these lost pups are taken on by another elephant seal mother, especially if she has lost her own baby in the same incident.
Seemingly, a mother’s instinct to care for a child, any child, governs all in animals who invest everything in a single birth.
Top image: a bottlenose dolphin pod in Raja Ampat. Credit: Cavan Images/Henn Photography/Getty Images
