This was a bad summer for North Atlantic right whales, with 17 deaths in waters off Canada and the U.S.
Some of those deaths happened when the whales were struck by ships, but others happened as a result of whales becoming entangled in fishing gear. There are only about 450 of the whales left in the world, and entanglement is now the leading cause of death for them.
What happens to many whales after entanglement has been something of a mystery. Now, stress hormones found in the whales’ feces may be providing some clues.
A new study in the journal Endangered Species Research looked at 125 whales over 15 years, and shows that those that remain tangled in fishing gear for long periods of time — months, or even years — have extremely high levels of the stress hormones in their poop.
Maine Things Considered Host Nora Flaherty interviewed Elizabeth Burgess, a marine biologist at the Anderson Cabot Center for Ocean Life at the New England Aquarium, who says those hormone levels aren’t just bad for individual whales, they’re bad for the population as a whole.
Burgess: This study is the result of 15 years of work, and throughout that time we’ve been able to establish a baseline of what a normal healthy whale looks like and what that profile for cortisol, the stress response comes out as in the feces. What we’re doing is kind of like using feces instead of blood, because blood is very difficult to collect from the whales — we’re getting an indicator of the internal health of the whale. While whales can occasionally be seen entangled, and we know that there’s physical damage, by having a look at the stress profile in the feces, what we’re getting at is what’s happening inside the body, so a whole-animal response. What we’re seeing with entangled whales that are chronically entangled for, on average, six months, is we’re getting sky-high levels of cortisol as a stress response. These are orders of magnitude, so they’re not minor elevations, and this is quite different to what we see in a whale that has been struck by a ship. Those whales tend to die very quickly, and so the cortisol levels in the feces that we see in those animals actually match what we see in a normal whale. That is because that stress response hasn’t had time to get through to the feces.
Flaherty: Obviously swimming around for a long time entangled with fishing gear presents its own dangers, infection and so forth. But the stress it creates also has some fairly profound effects, correct?
Yes, absolutely. By seeing these these sky-high hormone levels, we’re seeing that these animals are suffering terribly. It’s not just the external physical trauma that we can see visibly, or when we see a dead whale washed ashore, but there is a very strong internal response. It really speaks to the welfare of these animals.
Do these high stress hormone levels have effects on things like breeding?
Absolutely. A heavily mounted stress response is going to impact body condition and energy reserves of these animals, so we start to see emaciation in the population, and then further down the track it really affects reproduction. For females, they tend to breed less, which is going to further impact the population because if we’re not getting new calves into the population, then we’re not going to see that population growth. This year we’ve had 17 deaths of North Atlantic right whales and only five calves born. These heavy impacts on the population are really not sustainable.
North Atlantic right whales have been protected for more than 40 years. But unlike some other large whale species they’ve not really bounced back. Why is that?
These whales travel along the entire Eastern Seaboard — really very urban habitats — so management for this species, they have quite a high interaction with human impacts from shipping and entanglements. This year particularly, entanglements has been quite a big issue because what we’ve seen is a shift in their distribution. With warming waters in the Gulf of Maine — the Gulf of Maine has actually had an unprecedented increase in water temperature — that’s affected the food source of this whale. So the whales are moving farther north and potentially farther offshore, and they’re encountering new areas that previously may not have had strong management protocols in place. That’s that’s why we think we’re seeing quite high incidences of entanglements this year.
How few whales do you get down to before the population becomes not viable?
That’s a really great question, and we don’t really know. But currently, at less than 450 and with a projected trajectory of decline, we’re really getting into very scary territory of losing this species. Some modeling papers are predicting that we probably have 20 years left at this current rate of decline. We really are in a very dire situation.
What does your research suggest in terms of steps to protect the whales, and how confident are you that those will be taken?
This study is really important because it raises awareness of the suffering that these animals are going through. But it also helps us establish information about what we can expect to see in this population. From this study we’re getting very important information about the very chronic levels of stress in a right whale, and we can use this information to help monitor those living whales and try and highlight early warning signs of impacts in the population before we start to see these mortalities. If we’re able to get an early warning sign of seeing a strong stress response across the population, then we can use that to really engage a management practice or a management change. At the moment what we’re doing is we’re really engaging with the fishing gear, we’re having open conversations about some solutions that we can come up with so that we can continue fishing, but that we’re not entangling right whales and we’re not further endangering the population. These are ongoing discussions both at the government level and with industry and the fishermen that are out there.
This interview has been edited for clarity.
