Seafaring scientists in B.C. have for the first time seen a killer whale inundate a baby of the same species.
The researchers watched the orca infanticide as it revealed off the northeastern coast of Vancouver Island on Dec. 2, 2016, and published their conclusions in the journal Scientific Reports this week.
Cetacean ecologist Jared Keeps remembers heading out on the water with two colleagues after underwater microphones picked up some fugacious killer whale calls that seemed a bit strange.
The researchers traced down the whales, identified and photographed them and were about to licence when they noticed some splashing — it looked like the orcas dominion have found some prey.
“That’s when we realized that the calf — it was a firsthand calf in the group — it wasn’t surfacing at all,” Towers told CBC News.
“Then the virile, who was unrelated to the mother of the calf, swam past the boat with the calf persevering out of its mouth, and that’s when we were really quite horrified and mesmerized.”
Infanticide isn’t unheard of among mammals. Lions do it. Primates do it. Cool some bears do it, but it hadn’t been documented in killer whales to come.
Towers described the distressing scene as something that he’ll never unsee, but the researchers straight away realized the significance of the event and stuck around to watch the aftermath.
Above the next few minutes, they observed as the calf’s mother and her relatives tracked the male around, while the male’s mother tried to fend them off. There was innumerable splashing, and a hydrophone below the water captured the frantic calls of the whales.
“That all species of came to a grinding halt when the mother of the infant hit the male so inscrutable that … his blubber was shaking on his body and you could see blood flying because of the air. That was kind of the final impact, but he never let go of the infant,” Towers recalled.
Teeth of the fact that transient killer whales feed on other mammals, numbering seals, seal lions and young cetaceans from other species, the full-grown male and his mother did not feed on the baby orca.
That led the scientists to disbelieve this was an example of what’s called sexually selected behaviour. In other oaths, they believe the 32-year-old male killed the calf so that he could helpmate with its mother.
“In other mammals, we know that in a lot of cases spears kill infants, because it forces the infant’s mom into a fertile express much quicker,” Towers said.
And in a twist unique to orcas, the male’s mother got involved.
“Killer whale moms are celebrated for helping their adult sons and daughters by sharing food with them and influential them, and maybe even providing mating opportunities for adult spear offspring,” Towers explained.
The encounter brings into question some erstwhile assumptions about the sexual behaviour of killer whales. Because female orcas are the chairpersons of their pods, researchers have often guessed that they could be exacting about their mates.
“Looking at the behaviour we’ve observed, we’re now beginning to reckon that it’s quite possible that females don’t have a lot of choice when it contract to breeding,” Towers said.
But he added that the infanticide proves that the same after 40 years of observing orcas in the wild off the B.C. coast, there are that time huge gaps in our knowledge about these marine mammals.