Much has been said about a mother’s bond with her young, but little is known about the biological glue that ties males to their offspring. Now Canadian scientists show that when male mice interact closely with their babies, their brains grow new neurons that help them recognize their pups weeks later, when they have grown into adults.

Male mice who stay with females during and just after pregnancy spend their time nuzzling in the nest. Those animals were able to recognize offspring after they grew up, but mice removed from the nest after the litter was born could not, Gloria Mak and Samuel Weiss of the University of Calgary in Alberta, Canada, found. Fathers that stayed with the new litter also showed a burst of new neurons in two regions of the brain linked to the ability to differentiate odors – the olfactory bulb and the dentate gyrus. What’s more, those neurons preferentially responded to the offspring’s smell.

In females, the hormone prolactin induces new neuron birth during pregnancy or after exposure to male hormones, so the researchers wondered whether the same hormone was at play with males too. Indeed, males lacking the prolactin receptor didn’t produce new neurons and were unable to recognize their offspring. When neurogenesis was induced with another hormone, however, recognition was restored. The study appeared online in Nature Neuroscience yesterday, and the researchers speculate that the same mechanism might work in humans, too.