Grandmothers. The matriarchs of family units, our female elders are some of the most influential individuals in our lives, both as children and as we grow into our own in adulthood. Could this special dynamic be present in other species besides humans? This question became a prominent topic of discussion in the science community in early December, when a study published in the Proceedings of the National Academy of Sciences, specifically focused on a fascinating finding:
Data suggests the theory that orca grandmothers play a crucial role in helping their grandchildren survive.
Let’s dive into the highlights of the study, published just last month. While studying orca populations in the Pacific Northwest’s Salish Sea between Vancouver and Washington state over the course of 40 years, scientists found that the presence of grandmothers in orca pods is a key predictive component in determining the likely survival rate of juvenile orcas. Essentially, orcas with grandmothers around were noted to have better odds of surviving than those without grandmothers. Since orca communities are tight-knit and organizationally highly matriarchal, it can be deduced that older female orcas provide key survival knowledge (such as locations of plentiful food sources) that significantly boost their group’s chances of survival.
It’s important to remember that orca pods are big, but not huge: these animals thrive in close communities of up to 40 individuals and often engage in teamwork when hunting for prey. While both male and female orcas thrive in these groups, their survival rate and relevant reproductive trends are what prove most fascinating. As with most other mammals, male orcas don’t experience a “phase out” of their reproductive abilities. For the most part, they can produce offspring their entire lifespan, which for most of them is around 50 years old. Female orcas, however, have been reported to live up to the age of 90 years old. Here’s where things get interesting.
Orca ladies are one of only five species of mammals known to experience menopause.
The other four? Belugas, narwhals, short-finned pilot whales, and human beings.
Menopause for orcas occurs around the age of 40, cutting their reproductive years down to only a portion of their actual lifespan. The eyebrow-raising question is clear—through an evolutionary lens, what positive role could older female orcas play once they’ve surpassed their reproductive years, let alone for another 40-50 additional years after that? One popular theory in the scientific community is what’s known as the “grandmother hypothesis.” Kristen Hawkes, an American anthropologist who studied modern hunter-gatherers in Africa, theorizes that human grandmothers play a crucial role in the survivorship of their grandchildren, specifically by providing a source of childcare and guiding the group to accessible food supply sources. Could a similar theory be applied to orca populations?
According to recent research, this may be likely. The study of Pacific Northwest orca populations showed that older female orcas who have gone through menopause are more likely to dedicate time to their grandchildren than females who haven’t yet gone through menopause, likely in part due to the fact that these individuals aren’t under pressure to care for their own offspring anymore. This increased accessibility also meant that the loss of a grandmother could impact orca families in a hugely negative way: in the same populations studied, the risk of death for juvenile orcas rose drastically in the years immediately following a grandmother’s death. This risk was especially intensified when food sources like Chinook salmon were less than plentiful, suggesting that the older female orcas are extra helpful to have around during times of higher stress due to lack of food availability. According to Daniel Franks, one of the senior authors of the orca study, the effect doesn’t just impact grandcalves as babies either—the loss of a grandmother can impact orcas even when the grandcalves reach adulthood.
The “grandmother effect” theory seems to be an unexpected yet incredibly powerful evolutionary strategy. There’s much more research that’s needed to further understand the familial dynamics of these cetacean communities, and scientists believe findings like these could be key to understanding how best to help conserve and recover struggling orca populations. To better understand these family functions, however, we’ve got to protect the species at stake. Without them, the foundation of their communities and what makes them so special may forever remain a mystery.
I couldn’t help but think that even as adults, the loss of a grandmother can be incredibly difficult for orcas. It reminded me how much I, even as an adult, was hugely impacted by my own grandmother, who was one of my best friends. She was an essential figure in my life as long as I can remember, and when she passed away last year, it affected both myself and my entire family immensely. It’s without question that my grandmother filled an irreplaceable role in the structure of the family that raised me into the person I am today, and knowing that dynamic may be similar for orcas, my favorite animals, was mind-blowing for me.
Perhaps, in a world that seems overwhelmingly complex at times, the creatures we feel most different from aren’t so different from us after all. And where we can find similarities between our own experiences and those of wildlife, we may become more likely to feel connected to the natural world … and ultimately (I hope) much more driven to save it.