Orcas give up having more calves to care for their adult offspring

() — It’s no secret that parenthood can be demanding and sacrifices are often made for the sake of offspring. But for female orcas, the role can be especially difficult.

New research suggests that female killer whales may be giving up further offspring for their male offspring, even as adults.

The investigation, published this Wednesday in the Current Biology magazinefocused on a group of killer whales known as the “southern resident” population, off the coast of Washington state and British Columbia.

He Whale Research Centerwho participated in the study, has been observing the group since 1976.

This is an unusual species, as males and females remain with their mothers for their entire lives. However, the “cost” of caring for the mother is higher in the case of sons.

Michael N. Weiss, director of research at the center and a postdoctoral research associate at the University of Exeter, said in a press release: “We have known for over a decade that adult male killer whales depend on their mothers to stay alive, but it’s never been clear whether mothers pay a price for it.”

The data revealed “a strong negative correlation between the number of surviving weanlings of females and their annual probability of producing a viable calf,” according to a news release. And the result remained the same regardless of the age of the son.

“The magnitude of the cost that females take on to care for their weaned children was truly staggering,” Weiss said. “Although there is some uncertainty, our best estimate is that each additional surviving pup reduces the chances of a female having a new calf in any given year by more than 50%. This is a huge cost to care for the pups. [adultos]”.

Share the food

The researchers don’t know why female killer whales are less likely to reproduce in these cases, but they suspect that sharing food with their adult offspring may mean the mothers have to survive on less.

Sam Ellis, a researcher in animal behavior at the University of Exeter and a co-author on the paper, told on Thursday that the nature of the mother’s care largely revolves around her diet of Chinook salmon.

“Really the key to this form of care is sharing food,” he explained. “We think a lot of caregiving is physically providing food for your adult children,” she said, though they also lead them to the source of nutrition.

“Having a daughter doesn’t affect her chances of reproducing, but having a son of any age has a negative impact on the mother’s chances of reproduction,” Ellis said.

According to the team, this finding is very rare.

“It’s further evidence of how special (and perhaps unique) the mother-infant bond is in killer whales,” Weiss said.

Ellis added: “There are many examples [en mamíferos] of maternal care and maternal investment in young calves. But in all the examples that have been studied so far, once the hatchling reaches maturity, that reversal seems to stop.”

“We know that children whose mothers die have a really high probability of dying the following year,” he said, adding that while female orcas can live to be 80, males are “very lucky to make it to 40.”

Southern residents are critically endangered, so the study could have important implications, according to the researchers.

Ellis noted that the team wants to further study the long-term effects the findings could have on orca populations.

Luke Rendell, a professor of biology at the University of St. Andrews in Scotland, told that the study, in which he was not involved, was “fascinating.”

“Open a new window… [a] the way in which the evolutionary dance between the interests of individuals and genes constantly interacts with ecology and sociality”.

“Many will smile at the jokes about children in need, but also, I hope, will ponder whether the parallels run deeper in this long-lived and highly social mammal. Such insights are only possible through dedicated, long-term studies, often underappreciated by the funders of the investigation”.