New research off Cape Breton sheds light on pilot whale behaviour

New research from Dalhousie University in Halifax could lead to a better understanding of mass strandings of pilot whales.

The long-running study was conducted between 2018 and 2021 off the coast of Cape Breton Island and its results recently published in the scientific journal Animal Behaviour.

Globally, hundreds of pilot whales have died in the last few years after becoming stranded on beaches. A group of 11 pilot whales was found in Port Hood, N.S., this summer, eight of which died. In Australia in 2020, the majority of a 470-strong pod of pilot whales found stranded off the country’s southern coast died. Later in 2022, most of the 230 whales that were found stranded on the remote west coast of Australia’s island state of Tasmania died, as well.

Elizabeth Zwamborn is a PhD candidate at Dalhousie and one of the researchers. She spoke to Information Morning Cape Breton’s Steve Sutherland last week about the findings.

Their conversation has been condensed and edited for clarity and length. 

Maybe you could start by telling us how frequent mass strandings are in pilot whales compared to other species.

Pilot whales are actually the No. 1 most-stranded species worldwide. Part of this reason is because they tend to come onshore en masse, sometimes in the hundreds.

The largest stranding of long fin pilot whales on record was actually at the Chatham Islands near New Zealand and it was over 1,000 individual stranding in that particular event. 

This might be a little foreign to us because we have smaller strandings in Nova Scotia and not so frequently. The last one, indeed, was this year in Port Hood in June.

What were the questions that you set out to answer?

Pilot whales get their name from this idea that there’s a pilot or lead individual. We often think of it during strandings. People might say, ‘oh there might be a sick leader or the oldest female might be sick,’ but in reality, we don’t know how they make decisions and we don’t know whether there is a lead individual. 

And that information is really important when it comes to both studying the live whales but also what happens during these strandings.

What did you do to study that?

Technology can be a curse, but it can also be great. And in this case, drones have allowed us to really look into the lives of whales and dolphins, particularly when they’re near the surface. So, the pilot whales will spend at least a couple minutes near the surface just breathing. Before, with the boat, you could only see them when they popped above the surface to take a breath. With the drone, we can now follow them. 

We’re able to tell a couple of things such as where the whales are in the group, who is initiating that dive or leading that dive and what exactly is going on between the individuals within a group.

How did you handle the logistics?

It’s a lot of boats, a lot of drone time, a lot of early mornings, a lot of late evenings. 

So, you’d send the drone, you’d find a pod and then observe. What did you observe?

We noticed that when the whales dive, you can look at the timing, the consecutive whale. So when the lead whale goes and then you look at the timing of when each other individual does that deep dive and joins in. And that would tell us a lot about what was happening.

We looked at whether they were following a leader, which would be indicated by whales quickly following the first whale.… So, you have the first whale dive and then, all of a sudden, all these whales following it. 

We looked, also, to see whether there might be some sort of quorum or threshold that needs to [be] met. Maybe, three whales dive and then everybody else thinks that it’s a good time to dive. So, we looked for that too and we didn’t see that. 

It looks like the pilot whales are following leadership, but then our question was who is leading and is there anything that we can learn about where they’re leading from or what they might be doing.

And?

First of all, we found that the females are leading most often. Anybody in the group can, in theory, lead. The mature males, the juveniles could lead, but they very seldom initiated the dive. This might be a little bit predictable in the sense that we’ve learned from killer whales that the matriarchs or those older females tend to lead because they have a lot of valuable knowledge about where to find food when food is scarce and other pieces of information like that.

We also learned that these leaders were almost always leading from the left or right flank, so the outside periphery. There were a few exceptions in there, but the vast majority of them were leading from these outside positions, which is kind of weird because you think that something might lead from in front or from the centre. That’s a human centric view on it, of course.

We have to sit down and think for a second, ‘why would you lead from the side?’

The closest thing we can think about is cattle drives.

You have these riders in the back that, of course, [are] driving the whales forward. But you also have people on horseback on the left and right flanks on the side, and they’re really important for the cohesion or keeping all the cows together.

We think that, probably, the whales that are leading these dives are very likely also playing an important role in keeping everyone together. Watching out for if calves would stray outside or if individuals would get too loosely spread because before a dive it might be important to dive together. 

And then also from that side position you can watch for predators or other threats like maybe vessels approaching too closely or something like that.

Just out of curiosity, was it the same individual leader for each group? You mentioned that sometimes it was juveniles, sometimes it was males, but mostly it was females. Did you find a consistent leader for each group of whales?

Unfortunately, due to the fact that there’s 3,000 to 4,000 pilot whales that come and use Cape Breton waters in the summer, we did not get to drone the same group on multiple days very often. That’s a study that needs to happen. 

Scientists do something called ‘focal follows,’ which means you take a group and you follow them for the day, and you collect consecutive information on these dives that they’re doing, and that would be able to tell us whether there’s one individual, a particular individual in the group, that’s leading most often.

In what ways could this help inform, for instance, responses to mass strandings?

There’s a very strong link between what we’ve learned and what we could potentially do better in mass strandings, particularly something called pre-stranding. You might have heard of this big stranding that happened in Australia a couple of months ago. The whales were seen before the stranding, all huddled together for several hours. 

Mission to rescue whales stranded off Australian coast

Featured VideoA rescue mission is underway off the coast of Australia, for about 270 pilot whales stranded on a sandbar. Ninety of them have died, but 25 have been saved so far.

A decision was made not to do anything because they were worried about driving them onto the beach by accident. 

But perhaps using this idea of how they make decisions, we might be able to guide them out more efficiently by not only having boats behind them, but also placing boats or some sort of vessel on the side of them to keep them together as you drive them offshore. We don’t know exactly what happens when pilot whales strand. It can be caused by us humans, but it’s also often natural in these areas called ‘whale traps,’ where the bottom is just so shallow and sandy that they can’t navigate properly.

We’re starting to understand how they make decisions in the wild, what bad decisions or lack of decision is happening before they get themselves into these stranding situations.