The hormone that makes gray seal moms nuzzle up to or ignore their round seal babies has been discovered in a recent study. It's possible the finding will hold evidence for understanding why human maternal behavior exists on a spectrum.
That hormone is oxytocin, which has already been associated with maternal love in studies of humans and captive animals - but a link has never before been found in wild subjects in their own habitat.
Research fellow Kelly Robinson, of the Sea Mammal Research Unit at the United Kingdom's University of St. Andrews, led a team that included scientists from University of Durham in a study of gray seals on the island of North Rona in the North Atlantic.
During the two years of research, Robinson recorded the seals' maternal behavior shown toward pups during the raising period on an island (uninhabited) 50 miles west of the Cape Wrath area.
The scientist tested the mother seals' blood for oxytocin levels and found that the higher the hormone level in a seal with offspring, the nearer that she remained to her new pups. Individual mothers ranged from zero to 30 meters from pups - but again, those that stayed nearest to the young ones showed the highest oxytocin concentrations.
"Some gray seal mothers are much better at raising pups than others, even when allowing for differences in the mother's age and size and, as a result, some pups on a breeding colony die while others thrive. Studying the role of oxytocin, a hormone that regulates maternal behaviour, offers some insights into why such differences in individual behaviour occur," Robinson said.
The team also established that oxytocin concentrations were a good deal lower in non-breeding seals than in seals with dependent offspring in early or late lactation. These numbers were not related to the mother's amount of nursing before the sample was taken or to the amount or intensity of nursing the mother allowed.
When the key hormone is in place, it reduces the chances of mothers and pups becoming separated during the lactation period. Starvation caused by such separation is actually the highest cause of pup mortality in gray seals.
The study findings were recently published in the journal PLOS ONE.
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