Current Nature: What Whales Can Teach Us About Living a Long Life

In the past couple of weeks, there has been a flurry of humpback whale activity around Nantucket. They have been splashing around the south shore, putting on a show for those lucky enough to catch a glimpse. These sightings usually coincide with a boom of Sand Lance fish off Nantucket’s coasts; in the past few years the Sand Lance population has been booming, bringing more whales to Nantucket's waters to feed. If you’re anything like me, you’ve been keeping a close eye on where the whale action has been (via The Current’s Instagram) in the hopes of spotting one yourself. While I have yet to see one, I’m glad to know these magnificent creatures are close by.

Most species of whales have a complex and vital social structure, centered around family relationships. Humpbacks are no different, these whales live in social groups called pods. These pods can be made up of three to 60 individual whales, depending on the local population, and family ties. Every distinct population of humpback whales have a completely different dialect (songs and calls), culture, feeding practices, and migration routes depending on where in the world they live.

Currently, there are 14 distinct populations of humpback whales around the globe, with each population made up of many pods. The whales we see feeding around Nantucket are a part of the West Indies population. This population breeds in the West Indies and feeds along the East Coast of the United States and Canada.

Despite the differences between each population, every pod has a similar social structure. Each pod is led by a central matriarch, called a cow, she is the grandmother of nearly all the calves in the pod, the mother of nearly all the adult females in the pod, and the leader of the group. Once the calves reach sexual maturity the females can either stay with the pod or go off and form one of their own. Males, also known as bulls, will leave and join other young bulls to form a juvenile pod. One day, these bulls may join a pod of their own and become the dominant bull that protects the pod and sires most of the calves. But don't forget who the real leader of the group is: Grandma!

The matriarch (grandmother) of the group is especially important as she is the one who will teach the young calves to hunt, where to feed, protect them, and teach the mothers (her daughters) how to care for their young.

These matriarchs act as midwives for their daughters during labor and babysitters long after. The survival rate of calves who have a grandmother present is four to five times higher than calves who do not have a grandmother present.

These intricate relationships between mother, grandmother, and calf give us a glimpse into just how similar humans and whales truly are. The long-lived nature of both humans and whales allude to just how vital grandmothers are to the success of the species. In most cases, the lifespan of an animal ends shortly after it can no longer reproduce. One reason for this is because most young can take care of themselves right after birth. Extra parental care wouldn’t increase the young's survival rate so there is no evolutionary pressure for the adults to live longer. This is not the case for humans and whales who, when born, require an immense amount of care. So, having family members that live 80-90 years on average, long past reproductive age, would ensure more members can help care for the young, increasing the success of the species overall.

This phenomenon has been dubbed "The Grandmother Hypothesis." This hypothesis has also been used to explain why both female humans and whales have evolved to undergo menopause after passing reproductive age. Having this life stage where a female is unable to reproduce eliminates competition between generations for mates or other breeding resources. Now, grandmas can provide support to the younger members of the group, all of which increases the success of the species overall.

As the feeding season draws to an end, the humpback whales will leave the waters of Nantucket and head to the West Indies to breed and rear their young in the winter months. They will then migrate back to their North Atlantic feeding grounds, with the new young in the spring. So, make sure to head out to the south shore soon for a chance to see the humpback whales before they head south for the winter. If you do spot them, remember that the matriarch is probably nearby looking after the young ones, as a grandmother's work is never done (thanks grandma!).

Stay tuned for more editions of Current Nature, a bi-weekly column featuring seasonal topics, natural history information, and advice on the outdoors from the staff at the Linda Loring Nature Foundation.