A Grandmother’s Work is Never Done

| by Ocean Wise

A pack of killer whales cut through the Salish Sea, on the hunt for salmon. In the lead was Granny, the charismatic matriarch of J-pod: a group of Southern Resident killer whales who patrol the waters off the Pacific Northwest coast of British Columbia and Washington. Sometimes referred to as “the Energizer Bunny,” Granny was a tireless leader who chose her pod’s travel route, sought out Chinook salmon, and kept her family close, often summoning stragglers with a slap of her tail.

Hot flashes and night sweats are a luxury in the wild where animals rarely live beyond their reproductive years.

Granny was literally a grandmother. She likely went through menopause around 45 years of age and then she lived another 60 years, reaching an estimated 105 years old. Male killer whales typically expire around 29 years old, but even if they live longer, they don’t surpass their reproductive years. Menopause is very rare in nature, well-documented in only a few species like humans and short-finned pilot whales. Hot flashes and night sweats are a luxury in the wild where animals live just long enough to reproduce. On the Pacific Northwest, salmon are the most visible example of this, washing up dead and bloated on riverbanks shortly after they spawn. So, why did Granny reach such an esteemed age?

Two members of J-pod, Granny’s Southern Resident group of killer whales off Washington and British Columbia.

It turns out killer whale retirement isn’t all that leisurely. Granny played a key role in J-pod’s survival, helping her daughters raise their young while passing along decades of ecological wisdom. But older female elephants also provide for their social groups while continuing to reproduce and pass on genes. So, what makes killer whales different?

Granny outlived all her children, but she continued to care for the rest of the pod.

In a 2016 paper, University of Exeter behavioral ecologist Darren Croft proposed an explanation for menopause that focused on reproductive conflict between the generations. A grandmother’s calf is 1.7 times more likely to die than her daughter’s, if both give birth at the same time. A grandmother struggles to shore up the energy to survive the physical demands of raising a calf; she needs 42% more food! This is especially difficult for grandmothers who are busy helping other pod members.

A drone image of the famous Granny from above.

This leads to another explanation for menopause, one favoured by marine mammal biologists like Lance Barrett-Lennard who heads Ocean Wise’s Marine Mammal Research Program. In species like humans — and killer whales — the young rely on their mothers for care and learning for many years. As a female ages and her odds of dying increase, her offspring have less and less chance of reaching an age where they can survive without her. At some point, a female will leave more living descendants by putting her remaining energy into caring for her existing offspring rather than by producing more. According to this view, menopause is a trait that evolved to maximize females’ lifetime production of viable offspring.

Male killer whales require a lot of help from their mothers, particularly among Granny’s Southern Residents. When researchers first began to study Granny and J-pod in the 1970s, she was almost always seen with an adult male named Ruffles, thought to be her son. By supporting Ruffles throughout his life, Granny ensured that he could reproduce and further her line without the extra work of caring for more mischievous youngsters of her own. Granny outlived all her children, but she continued to care for the rest of the pod. After Ruffles’ passed, she extended her motherly instinct to the other young males in her pod. Unlike killer whales, elephants don’t go through menopause because male elephants leave their mother’s group – they simply aren’t around for their mothers to help.

Sadly, Granny passed away in 2016, leaving scientists uncertain about the fate of J-pod. However, two remaining females, Slick and Princess Angeline, have probably reached menopause already and could take on Granny’s role as post-menopausal provider. How they step into these leadership roles will determine J-pod’s survival in the coming years.