Tag Archives: Food sharing

News coverage: Killer whale grandmothers help their pods endure

I was surprised to see the sudden surge of news coverage explaining the important role that orca grandmothers play in our Northwest resident pods.

A new research paper adds statistical support to our understanding of why female orcas live long beyond their reproductive years. The new findings are certainly worthy of coverage — although I have never seen a news story about orca research snapped up all at once by the New York Times, Washington Post, Science magazine, National Geographic, London Daily Mail and South China Morning Post, as well as CNN, BBC and Seattle broadcasters.

Most news outlets broke the story within hours of Monday’s publication in the journal “Proceedings of the National Academy of Sciences.” The sudden news blast resulted from a coordinated effort to keep the story under wraps until the right moment, noted Ken Balcomb, the dean of orca research in Puget Sound who provided data and observations for the analysis.

Ken told me that he has rarely seen such widespread interest in killer whale research. A news release promoting the new findings about orca grandmothers was coordinated by the universities where the leading researchers are employed, namely the universities of Exeter and York, both in the United Kingdom. A timed embargo was imposed on the release to make sure no news reporter got the jump on anyone else.

The new findings are especially interesting, as they support the idea that orca grandmothers have much in common with human grandmothers, playing a nurturing and leadership role within their family groups. Also, the endangered Southern Resident orcas have been gaining worldwide attention as they teeter on the brink of extinction. For example, many people have not forgotten the image of Tahlequah (J-35), the 20-year-old orca mom who carried her dead calf around for 17 days last year.

The pronounced role of grandmothers in caring for their grandcalves has long been understood by orca researchers, but the statistical analysis in the new study clearly shows that “the death of a grandmother reduces the survival of her male and female grandoffspring in the two years following her death,” the research paper states.

A calf whose maternal grandmother dies is 4.5 times more likely to die within the next two years when compared to an individual with a living grandmother, the report says. Furthermore, an individual who loses a post-reproductive grandmother is 1.5 times more likely to die than one who loses a grandmother who is still producing offspring.

In the vast majority of species, females lose their ability to reproduce as they approach the end of their lives. But orcas and a few other toothed whales, as with humans, go through menopause and stick around for many years after they can no longer produce offspring. Grandmothers who do not have to care for their own calves seem to provide extra benefits, including an important leadership role, the new research suggests.

“We suspect when breeding grandmothers are supporting their own calves, their movement and activity patterns are constrained and they are not able to provide support and leadership in the same way as post-menopausal females,” states the paper’s lead author, Stuart Nattrass of the University of York, in the joint news release issued by Exeter as well as from York University. “Also, grandmothers with their own calves will be busy caring for their own calves, and be able to invest less in their grand-offspring, compared to post-menopausal grandmothers.”

It has long been known that killer whales generally stay with their mothers from the time of birth until they die, so that multiple generations of related orcas travel and forage together. Mothers tend to share food with their offspring into adulthood, especially their sons who need more food to survive.

Ongoing studies with unmanned aircraft, or drones, are designed to identify patterns of food sharing and socializing that can contribute to long-term survival.

“A lot of our information is based on historical surface data,” Ken noted. “The new drone work has shown a lot more detail, including underwater contacts that we could not see before. Food is important, but so is socializing.”

Grandmothers have been seen to support their grandcalves, sometimes staying with a calf while its mother is gone for a while. Elder females, often post-menopausal, are known to be the leaders of the matriarchal groups. Their knowledge of where to find fish to eat may be the key to success for the pod — especially in this time of food shortage, as the orcas range over wider areas to find new hunting grounds.

The new study explains for the first time in quantitative terms how older grandmothers can enhance the survival of the young members in the family group, thus providing an evolutionary benefit to pods containing post-reproductive females. The data show why the pattern persists over time.

In fact, the study even looked at survival rates when food was more or less available. It turns out that the loss of a grandmother carries even more risk to a youngster when food is scarce, as we are seeing under current conditions in the Salish Sea, according to Dan Franks, of the Department of Biology at the University of York and senior author on the paper.

“The death of a post-menopausal grandmother can have important repercussions for her family group, and this could prove to be an important consideration when assessing the future of these populations,” he said in the news release. “As salmon populations continue to decline, grandmothers are likely to become even more important in these killer whale populations.”

As food grows more scarce, the pods have been splintering into smaller groups, according to Ken Balcomb. That leads to less socializing with other pods and presumably less opportunities for mating. The need for new calves to replenish the population seems paramount, but survival of the existing orcas during a food shortage is no small consideration. Some studies suggest that a high rate of miscarriage occurs among pregnant females when food is scarce, and we know that pregnancy requires increased caloric intake.

The new analysis was based on 36 years of data about the southern resident and northern resident killer whales collected by Balcomb’s Center for Whale Research along with Canada’s Department of Fisheries and Oceans.

Ken’s overall message has remained the same when it comes to the future of the southern resident orcas. It all has to do with getting more salmon, especially chinook salmon, their primary prey species.

“Unless we do something about the prey resource, we will be seeing problems for the next 20 years,” he said. “There is never going to be a big population even if nobody dies. We are not solving the problem now, and we will be damned if we will be able to solve it 10 years from now.”

Headlines about grandmother orcas in stories this week: