Research team in Iceland includes scientist from Dalhousie University
A rare sighting of a killer whale mothering a newborn pilot whale is either a touching adoption story or a disturbing case of kidnapping, says a Dalhousie University researcher.
The pair were spotted swimming together off the coast of west Iceland in August 2021. Researchers say it's the first time an orca has been documented caring for the offspring of another species.
Elizabeth Zwamborn, a PhD candidate in biology at Dalhousie in Halifax, was part of the research team that recently published their findings in the Canadian Journal of Zoology.
Her conversation with Maritime Noon host Bob Murphy has been condensed and edited for clarity.
You can listen to the full interview here:
Elizabeth Zwamborn, a PhD candidate at Dalhousie University in Halifax, tells us about her research into an orca in the waters off Iceland that adopted — or perhaps abducted — a newborn pilot whale calf.
What did you see, or what did the researchers see, when it came to the condition of the calf?
It was what we would categorize as emaciated, meaning that its fat layers were not in good condition. It obviously hadn't fed recently, and this is not really something that surprises us because a killer whale without her own calves probably wouldn't be able to nurse.
Orcas are often seen in pods. How many were seen in this particular case, and maybe describe how they were positioned in relation to this calf.
This is a group of three well-known individuals that travel together, very likely a mother and her two offspring, both a male and a female. But we're not quite sure because studies of the western Iceland killer whales have been fairly recent, just the last decade or so. What was seen is that this young calf was travelling in what we call "echelon" position or mother-calf position, right up alongside the female killer whale. That indicates caring because that position, that mother-calf position, is quite energetically taxing for the female killer whale as she pulls that newborn along in her slipstream.
You might assume it is a lovely warm story about altruism and parenting, but in fact it could be something different than that. What are you surmising?
Well, there are two possibilities. One is that she came across this orphan pilot whale calf that wasn't doing well, and that's the story we all think about, right? This lovely warm adoption story. But there's also a decent chance that she actually abducted this calf from a group of pilot whales. Off Iceland, there's been quite the interaction between both species and oftentimes pilot whales are seen chasing the killer whales. We don't know the reasons for it, but if there's a chance that there might be a female orca here and there that tries to take a calf from the pilot whales that would certainly give them reason to chase.
Is it possible the calf is easy prey, or could they use perhaps the calf to draw other pilot whales close to them?
They're mainly fish-eating killer whales there. They do eat a few other things … but predominantly this group has been seen foraging on herring … So it's very unlikely that they're trying to draw pilot whales in. The other thing is that if the calf was prey, we wouldn't expect it to be in that mother-calf position that is requiring energy from that female orca to keep it there, so it did not look like a prey situation.
How would the pilot whale calf be feeding during this time?
It's a newborn, so it's very young, likely within a month of age. And it would need to nurse from an individual that is able to nurse it. So if the killer whale had had a calf of her own that was stillborn or that died shortly after birth she might have been able to nurse. But there's a chance that this female killer whale just can't reproduce, and so if she kidnapped a pilot whale calf then it would be very unlikely that she'd be able to provide any food for it whatsoever.
So what's your best hunch at this point as to what you and the team were actually witnessing?
Of course, it's hard to tell without being there from the beginning. But this particular female killer whale Sædís has been seen interacting with pilot whales in a very unique way, where the pilot whales chased the killer whales, they stopped, and then the killer whales turned around back toward the pilot whales. And this repeated itself multiple times. So it looked like there could have been an attempt, perhaps, to take another calf. There was newborns within the group.
We know that other species, like bottlenose dolphins, will abduct calves … In fact, there was another case of this last summer where another female killer whale in the south was seen with a newborn pilot whale calf. So two sightings in two years is quite the eye-opener for us and what might be going on between these pilot whales and killer whales.
I think the biggest thing is we can't jump to conclusions right now … We only had this brief interaction with the pair. We're looking for, as we go through time, more evidence of this occurring or to be able to observe them over a longer period of time.
Do we know what happened to the pilot whale calf?
Sædís, the female killer whale, returned again without the calf the next year, so we're pretty sure that given its condition and her history of not having calves, it's very likely that it perished fairly soon after it was observed.
With files from CBC Radio's Maritime Noon
Credit belongs to : www.cbc.ca