For the past nine days, an endangered female orca has alternately nudged her dead calf’s body along with her forehead and dived deep to retrieve it when it sinks, in an unusually long display of grieving off the coast of B.C.
The devotion that Tahlequah has shown to her dead calf has prompted researchers to worry about her own health as she risks exhaustion, malnutrition and separation from her pod while tending to the calf’s corpse.
The calf was born near Victoria on July 24, but died moments later; Tahlequah was spotted with the body on Wednesday near Tsawwassen, the residential B.C. community just north of the Canada-U.S. border.
“Is she getting enough rest is one concern,” said Jenny Atkinson, executive director of the Whale Museum in Friday Harbor, Wash. “Second concern is, carrying this calf, is she able to successfully forage? We do know that they prey-share, so it’s possible that her family is finding food and sharing with her. But she’s travelling an inordinate distance ... and that would be stressful and an intense cost of energy even for [an orca] in good condition. So we’re very worried."
There are only 75 southern resident killer whales, the pods of orcas that inhabit the area, remaining, with the figure continuing to dwindle over the decades. Researchers attribute the decline to a lack of chinook salmon, pollution and vessel traffic and noise. The last successful birth was three years ago.
Tahlequah, whose name was chosen by the Whale Museum’s adopt-a-whale program, is also known as J35, because she belongs to the J pod.
Marie Fournier, a researcher with the Victoria-based Cetus Research and Conservation Society, said another concern is that J35 is lagging behind the rest of her pod.
“She’s having to go down and get her calf and then catch up with her group,” Ms. Fournier said. "Especially with boaters, we’re trying to make sure they really slow down because she’s so far behind the actual group.”
It is common for a cetacean to mourn its young, but rarely for more than a few days. Ms. Fournier said orcas have an 18-month gestation period and hypothesized that J35 might have felt a stronger bond with her calf because it was alive for a time, however brief.
“We’ve never seen a killer whale hold her calf for this long before,” Ms. Fournier said.
For now, biologists can do nothing but observe the pair. This is because it is illegal to intervene, but also because orcas are so tightly socially bonded that an intervention could make the situation much worse, Ms. Atkinson said.
When J35 does finally release her calf, researchers hope to collect the corpse to find out why it died. But that won’t be easy.
“The tricky thing with deceased orcas is very rarely do they float and come ashore,” Ms. Atkinson said. “Typically, they’re going to sink. It is desired to be recovered if the family ever surrenders it, but it’s going to be hard.”
As well, the mother has occasionally been spotted without the calf’s body, raising the possibility that others in the pod take turns tending to it, Ms. Atkinson said. She added that it would likely take a full day or two for observers to be confident that the mother has separated from its calf.
Fisheries and Oceans Canada will assume responsibility of the corpse should it be retrieved on this side of the border. In the United States, the responsibility would fall to the National Oceanic and Atmospheric Administration.
Ms. Atkinson said a number of factors could have killed the calf.
“Was it a lack of food? A congenital defect? A built-up toxin load from mom?" she said. "It could have been acoustic trauma. We don’t know. Until they actually have the opportunity to do a necropsy on any of these animals, you don’t know what killed it. And a lot of times, after a necropsy, you still don’t have a final determination.”
Female orcas have been having pregnancy problems because of nutritional stress linked to lack of salmon. A multiyear study last year by University of Washington and other researchers found that two-thirds of the orcas’ pregnancies failed between 2007 and 2014.
With a report from Associated Press