The hormone that stimulates mothers to produce milk also triggers a vital instinct in them to nurture their young, Kiwi researchers have discovered.
To show this, the scientists looked at mice and the hormone prolactin, which is best known for its role in enabling milk production in mammals.
They then deleted prolactin receptors in the brains of the adult female mice.
While the mice were able to become pregnant and give birth normally, they abandoned their litters within 24 hours.
Study co-author Rosie Brown from the University of Otago's Centre for Neuroendocrinology said this showed prolactin was important in helping mothers form crucial bonds with their babies.
"This work is the first to show this hormone is a literal life saver in that it establishes and maintains the normal parental care that ensures offspring survival," she said.
It also could help to explain why some animal species abandon their young and why disruptions in the ability of prolactin to communicate in the brains of mothers may cause them problems bonding with their babies, she said.