Researchers studying orcas have made a remarkable discovery about the relationship between females and their male offspring. It seems that mother orcas continue to feed their sons well into adulthood to help them survive, and the mothers do this at great sacrifice to themselves, reports the BBC. The study in Current Biology looked at killer whales in the Pacific Northwest, where a staple of their diet—Chinook salmon—has been in increasingly short supply, per the New York Times. Massive males of the species sometimes struggle to find enough to eat, and they're not as nimble as the smaller females when it comes to chasing a salmon underwater, explains NPR. Thus, it's mom to the rescue.
The mother orca will dive, "catch a salmon, and bring it up to the surface and actually bite half of the fish off and leave that half for her son," says researcher Michael Weiss of the Center for Whale Research. "So she's sharing a huge amount of food." The team found that mothers don't do just do this for newborns—the pattern continues all through life, and orcas usually stick together in familial bonds. The smaller amount of food mom consumes isn't the only issue—females with sons are about half as likely to have another calf compared to females with daughters or no offspring at all.
"We wanted to find out if this help comes at a price and answer is yes," says Weiss. "Killer whale mothers pay a high cost in terms of their future reproduction to keep their sons alive." Another telling stat explains the importance of the behavior: Male orcas over age 30 are eight times more likely to die during the year following their mother's deaths, presumably because they no longer have mom to provide food. As Quartz puts it succinctly, "orcas are all mama's boys." (More discoveries stories.)
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