A recent study led by researcher Alexandra Childs has shed light on a peculiar behavior observed among adult Galápagos Islands sea lions. Childs, a PhD candidate in behavioral and marine biology at the University of Bielefeld in Germany, expressed her surprise at witnessing fully grown sea lions continuing to suckle from their mothers. The study, published in the American Naturalist, revealed that approximately 11% of the sea lion population in the Galápagos exhibited this behavior, termed “supersuckling.”
According to Childs, most sea lions wean from their mothers between 1.5 and 4.5 years of age, just before reaching sexual maturity. However, the supersucklers defy this norm by persisting in suckling well into adulthood, with some individuals continuing the behavior up to 16 years of age. Childs likened this to humans breastfeeding into their teens or twenties.
The study, based on 20 years of data on Galápagos sea lions (scientifically known as Zalophus wollebaeki), suggests that this behavior could be a bonding mechanism. While supersuckling has been observed in other species of sea lions and seals, it is particularly pronounced in the Galápagos population. Andrew Trites, from the University of British Columbia, explained that such behavior is usually linked to food scarcity, where mothers provide additional milk to ensure their offspring’s survival and reproductive success.
Contrary to expectations, the study found that supersuckling occurred more frequently during periods of abundant food resources, indicating a potentially different reason for this behavior in the Galápagos sea lions. Further research is needed to fully understand the underlying causes of this unique phenomenon.