Do Hungry North Atlantic Right Whales Follow Their Noses?
Whales seem to find food by sniffing for a chemical cue. Scientists are hoping to turn this into an early warning system to help save the imperiled species.
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Onboard the Song of the Whale, spotting a cetacean comes with perks. “There is always a competition,” says Niall MacAllister, the boat’s skipper. Whoever sees the first whale, or the most whales, might be treated to a pint the next time the sailboat docks. Not that the people on this specially designed research vessel need extra motivation to watch for whales.
Since being built in 2004, the extra-quiet Song of the Whale and its crew have studied whales in western Europe, the Mediterranean, Greenland, and elsewhere. Right now, they’re off the coast of Massachusetts, where they’ve been trying to ensure a future for the North Atlantic right whale, a species in dire danger of extinction. That effort recently had them searching the water for a chemical clue they think might help predict the whales’ movements—and hopefully protect them from danger.
North Atlantic right whales have been called the “urban whale” because they live mostly along the bustling east coast of North America. Once nearly eradicated by whalers, the species bounced back to around 500 by the year 2010. But ship strikes and entanglement in fishing gear continued to plague the whales, and they encountered further trouble in the past decade when the warming ocean pushed their prey northward. Following their food, the whales suddenly showed up in large numbers in Canada’s Gulf of St. Lawrence.
“There weren’t any protections, and there wasn’t an expectation that they were going to be there. And it resulted in some pretty tragic deaths,” says Kathleen Collins, the marine campaign manager for the International Fund for Animal Welfare (IFAW).
As the whales had even more run-ins with ships, ropes, and other human hazards, the US National Oceanic and Atmospheric Administration (NOAA) declared an unusual mortality event starting in 2017. Today, there are thought to be fewer than 340 of the animals alive, with under 70 breeding females.
With the clock ticking, IFAW sent the Song of the Whale on a mission to follow the North Atlantic right whales up North America’s east coast. It’s a bid to learn what they can about the whales’ movements—including how to anticipate where they’ll be ahead of time.
In some ways, we know these whales intimately. Researchers can identify every living North Atlantic right whale by sight, and they maintain a catalog of the whales’ biographies. In other ways, though, the whales’ affairs are a mystery.
“One of the leading questions that we have in the larger scientific community is, Where are these right whales right now, and where are they going?” Collins says. “They’re notoriously hard to track.”
To protect them, it would be helpful to understand not just where the whales are now, but where they’re headed next. Scientists at NOAA’s Stellwagen Bank National Marine Sanctuary have put their hopes in the chemical dimethyl sulfide (DMS).
The molecule is made by phytoplankton, microscopic ocean algae. Its importance in understanding ocean food chains became apparent in the 1990s when Gabrielle Nevitt, a sensory ecologist at the University of California, Davis, was studying how certain Antarctic seabirds find krill to eat. The birds don’t seek out the fishy smell of the krill themselves, she found. Instead, the seabirds follow DMS. “They would track it like a little bloodhound,” Nevitt says.
Why follow DMS? The chemical tells seabirds that their prey are nearby having a meal of their own. DMS comes out of the tiny algae when krill or any other of the ocean’s miniature animals, called zooplankton, are eating them. “So as zooplankton crunch on phytoplankton, this DMS gas is just released into the water,” says David Wiley, a marine ecologist and research coordinator at Stellwagen.
Some fish also follow the smell of DMS to find food in coral reefs. Given the importance of DMS for various predators, Wiley and others wondered if right whales might be using the same cue.
Right whales are baleen whales, which means they fuel their massive bodies with minute crustaceans that they filter from gulps of seawater. We know what they eat, says Wiley, but “we don’t really know how whales find their food.”
Using a device that repeatedly tests the concentration of DMS in the water, Wiley and his colleagues have shown that higher concentrations of DMS correspond to denser patches of zooplankton. It’s not proof that whales, like birds and fish, follow the trail of DMS to find food. However, it shows that following that trail would work.
That’s why, this spring, Wiley joined the crew of the Song of the Whale to continue studying whether North Atlantic right whales are following the scent of DMS. As in his previous research, Wiley sampled the water for DMS. The team also recorded the locations of whales and, if they could, embarked on a smaller inflatable boat to sample the water closer to the animals.
Wiley says his preliminary data from this and other recent experiments shows that right whales—as well as another species called sei whales—are more likely to turn up in areas with higher DMS, suggesting they sniff the chemical out. “So far, all the data point to yes,” he says.
The crucial step will be to put this hypothesis into action. Now that Wiley and his colleagues have a strong suspicion that North Atlantic right whales are following DMS to find food, they hope their studies will reveal a specific threshold of DMS that predicts where the whales might soon come to feed.
If they can determine that, scientists could use sensing buoys or even satellite observations to gauge DMS concentrations in the ocean and warn local authorities, which could call for vessels to slow down or take other measures to limit the hazards to whales.
Such a system could someday join other ways scientists are trying to predict where whales will be, such as a project that tracks blue whales by modeling their movements based on environmental conditions, or one that finds humpbacks by looking for congregations of seabirds.
Nevitt, who discovered DMS sensing in seabirds, says working with DMS and getting timely, ecologically relevant measurements can be tricky. When it comes to following whales’ food, she says, “there might be less subtle indicators that are easier to measure.”
Whether it’s by following DMS or something else, efforts to predict North Atlantic right whales’ movements could help keep the teetering species alive so that future generations can spot them, too—perks or no.
“I’m optimistic that right whales, if left alone, can do fine,” Wiley says. “We just have to find ways to leave them alone.”