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dolphins

    CLIMATE

    Scientists Say ‘Cold Pulse’ Is Linked to Surge in Dolphin Strandings

    Warming water changes the food supply, leading animals closer to shore

    By

    PROVINCETOWN — Cape Cod has always had more dolphin strandings than anywhere else in the world. But 2024 was the worst year for strandings ever recorded here, and scientists have been trying to figure out why. Now they think they’ve found the reason: a “cold pulse” — a rush of colder, fresher water from the north, shocking the climate change-warmed Gulf of Maine.

    An Atlantic white-sided dolphin stranded in Wellfleet on June 28, 2024 was part of the largest mass stranding in U.S. history. (Photo by Jack Styler)

    The Cape is one of the dolphins’ prime feeding grounds, and its shape, shallow waters, fast currents, and big tidal fluctuations are some of the reasons strandings are common here. But it’s been hard to account for last year’s dramatic increase. According to the International Fund for Animal Welfare (IFAW), whose marine mammal rescue team is based in Yarmouth Port, there were a total of 376 dolphin strandings in 2024 — more than six times the annual average of 57. That year also included the largest mass stranding in U.S. history, when 146 dolphins stranded in Wellfleet Harbor on June 28.

    Glen Gawarkiewicz, associate scientist of physical oceanography at Woods Hole Oceanographic Institution, said the cold pulse threw off the ocean ecosystem and likely disrupted the dolphins’ offshore food sources, forcing them to seek food in shallower water, which put them at greater risk of stranding.

    Scientists are still studying the cold pulse to understand its precise cause, Gawarkiewicz said. But they know that, with climate change, “the system is getting much more impulsive now. We can get these big anomalies.”

    Oceanographers saw a significant drop in ocean temperatures across the Atlantic starting in August 2023, and it got more extreme starting in April 2024, Gawarkiewicz said. The cold water appears to have flowed from the Grand Banks and the Labrador Sea, he said, and caused temperatures to drop by 5 to 9 degrees Fahrenheit, from the coast to the edge of the Gulf Stream all the way down to the Carolinas. “I hadn’t seen anything like that before in the 40 years I’ve been going out to sea,” he said.

     

    Both Warmer and Colder

    According to Nick Record, senior research scientist at the Bigelow Laboratory for Ocean Sciences in Boothbay, Maine, pulses of cold Labrador water have always been a regular occurrence in the Gulf of Maine, but climate change has made them more extreme. The water now shifts from warm to cold more quickly. And because the Gulf of Maine is so much warmer now, the cold water is more of a shock. That cold water, he told the Independent in an email, “would have been normal temperature 20 years ago or so.”

    An aerial photo shows Wellfleet Harbor’s intricate inlets along Lieutenant Island Road, where the Wellfleet Fire Dept. and a team from IFAW rescued 11 bottlenose dolphins stranded in September 2024. (Photo courtesy Wellfleet Fire Dept.)

    The Gulf of Maine has been getting warmer since 2010, so when the cold pulse arrived, all the creatures who were accustomed to warm water were unable to adapt to the rapidly dropping temperatures. “The whole ecosystem was in a chaotic state,” Gawarkiewicz said, and many species left to find more comfortable habitats.

    Warm-water species, such as black sea bass, disappeared; and squid, which usually arrive in May, were nowhere to be found. “For a number of dolphin species, squid are an important food,” Gawarkiewicz said. This left the predators with no food and forced them to forage closer to shore. “The fact that everything lower in the food chain was so disrupted — I had to think that had a dire impact on dolphins,” Gawarkiewicz said.

    Lesley Thorne, an associate professor of marine and atmospheric sciences at the State University of New York at Stony Brook, agreed with Gawarkiewicz. “Over the long term, you’ve got some of these warmer-water species moving further north,” she said. “But at the same time, you’ve got this anomalous year oceanographically, which is really altering foraging conditions in parts of the Northeast.” This combination, she said, may have been the cause of the mass dolphin strandings.

     

    Already a ‘Hot Spot’

    The cold pulse adds a new challenge in a place that is already a stranding hot spot, according to Scott Landry, director of the marine mammal entanglement response program at the Center for Coastal Studies.

    The formation of the cold pulse in early 2024 shown along North America’s Atlantic coast. Blue areas are colder than average, red areas are warmer. (Illustration courtesy Oceanography Society)

    Cape Cod’s extreme tides are one reason: it’s easy for dolphins that are searching for fish in shallow water here to get stuck when the tide goes out. “The fish head to the beach, and therefore maybe the dolphins also accidentally head to the beach,” Landry said.

    “On Cape Cod, the currents are fierce,” said Landry, and that can make strandings worse. Following the curved shape of the Cape, the currents flow counterclockwise around the Bay, often bringing tired, hurt, or sick dolphins into Wellfleet Harbor. Then, because the harbor is shallow, the dolphins may get stressed and panic, causing them to get more stuck.

    Overall, Cape Cod’s hook shape also acts as a trap, Landry said, making it difficult for dolphins to navigate out.

    According to Landry, another reason that dolphins strand a lot is that they are very social animals. Dolphins live in family groups called pods that usually stay together for life. Landry said that if one dolphin in a pod is ill or confused and goes in to shore, the rest of the pod may follow and strand as well.

    Changes in the dolphins’ food sources are another problem. As climate change has made Cape Cod’s waters generally warmer, some shallow-water fish from the south that were once rare here have become more common, Landry said. This change forces dolphins to choose between the risk of being stranded and the risk of starvation.

    Dani Stone, a veterinary technician with IFAW, agreed, adding that during last year’s strandings, “We know that there were a lot of bait fish in the water close to shore.”

    Scientists do not think wind turbine development is a cause of any whale or dolphin strandings. Landry said that he has done surveys within wind energy development areas south of Martha’s Vineyard and has never noticed a whale or dolphin behaving abnormally in those zones.

     

    On High Alert

    Strandings put dolphins in a very vulnerable situation. On land, “they have a lot of gravity pushing down on organs that would normally be buoyant,” which can be lethal, Stone said.

    An illustration by Provincetown 6th-graders participating in a photojournalism and writing exchange with students in Newtok, Alaska, led by Emily Schiffer and Katie Baldwin Basile, with funding from the Local Journalism Project. (Illustration by Estella Boulin, Jada Buchanan, Daequan Channer, Javi Ganas, Jayla Graybill, Layla Guyette,
    Nora Harrington, Bettina Markowski, Deborah Markowski, Shania Marriott, Steven Meserve, Aiden Porter, Daisy Rios, Lola Schiffer-Kehou, Brandon Stefani, Brianna Walker, and Kimora Wright)

    If you see a dolphin on the beach, Stone said, do not feed it or touch it. Instead, stand by the dolphin, call IFAW, and report it. When IFAW volunteers arrive, they make sure that the animal is healthy and check for entanglement in fishing gear.

    IFAW usually releases the animals at Herring Cove Beach in Provincetown because there the water is very deep close to shore, ensuring that the dolphins can swim freely. Dolphins are moved by trolley to vans for transport. And IFAW makes sure dolphins are in good condition before being released back into the ocean.

    It is unclear whether dolphin strandings around Cape Cod will keep getting worse. “If there’s a lot of food here next year, then yes, the strandings, I bet, will be worse,” Landry said.

    “We’re all hoping that it was just an anomaly,” Stone said of the surge in strandings last year. “But we are all mentally prepared for it to be just as bad. We’re all on high alert here.”

    Staff reporter William von Herff worked with five Provincetown IB Schools students to research and write this story.

    WILDLIFE

    Dolphins’ ‘Signature Calls’ Could Predict Strandings

    A 2021 study done in Wellfleet Harbor suggests a possible early warning system

    By

    WELLFLEET — The unique sounds known as “signature whistles” that all the dolphin species found in Cape Cod waters use to identify themselves may be the key to finding out about dolphin strandings — like the one that took place at the Gut in Wellfleet Harbor on June 28 — before they even happen.

    IFAW volunteers rescuing a stranded dolphin near Powers Landing in Wellfleet on July 2. (Photo by Steven Bliss)

    Cape Cod is a global hotspot for dolphin strandings. Stacey Hedman, communications director at the International Fund for Animal Welfare (IFAW), which manages stranding responses on the peninsula, said the 10-year average is 315 strandings per year. And most of them happen here: 75 percent of Cape Cod’s mass strandings (in which more than two dolphins strand) occur in Wellfleet, Hedman said.

    Scientists do not know why dolphins strand. Without a clear cause, these events are very difficult to anticipate, according to Molly Dent, an instrument specialist at Mote Marine Laboratory and Aquarium in Sarasota, Fla. And because they are usually a surprise, it takes time for responders to arrive, which puts dolphins at increased risk of injury or death.

    Preventing dolphin deaths was the motivation behind Dent’s research into Wellfleet Harbor strandings as an undergraduate at Hampshire College in 2021. Her goal was to identify factors that preceded strandings to help rescuers predict when they would happen.

    A key component of her research was a collection of acoustic recordings from a buoy located about a quarter mile east of Jeremy Point. The recordings, made between 2014 and 2020, were mostly collected by her adviser, Laela Sayigh, who is a professor of animal behavior at Hampshire and a research specialist at the Woods Hole Oceanographic Institution.

    Dent compared the recordings with data from IFAW on nearby strandings. What she found was that, except in cases of very few dolphins stranding, the sounds dolphins made during the 48 hours before strandings were different from the animals’ ordinary calls.

    The key difference was those so-called signature whistles. Though these noises sound like any other dolphin sound to the human ear, Dent said, marine mammals use them to identify themselves to one another. They give these calls in many circumstances, such as between a mother and calf, when a dolphin is returning to its pod, or when they experience stress.

    Dent found that, on recordings from the day of or immediately before a stranding, an average of 82 percent of dolphin whistles are signature whistles. On other days, the average is only 54 percent. Dent thinks this is likely because dolphins are more stressed in the lead-up to a stranding.

    Dent and Sayigh wanted to use their findings to develop a warning system that would send an alert to IFAW when signature whistles are more prominent, the idea being to learn about imminent dolphin strandings before they happen. But identifying the whistles was time- and labor-intensive. Dent had to slow the recordings down to 25 percent of normal speed and scan the results through a spectrogram — a visual depiction of the sound’s frequency — to find the whistles. Then there was more work to be done to identify which of the whistles were signature whistles specifically. If there was a high concentration of dolphin sounds, five minutes of a recording could take a whole day to analyze, Dent said.

    A Feasible Approach

    A warning system would need to be automated, Dent said, with a computer trained through machine learning to identify different dolphin noises in real time. Before the researchers could begin that step, though, they ran out of funding to pursue the project further.

    Their idea, however, is “quite feasible,” said Christopher Clark, senior scientist emeritus at the Cornell Lab of Ornithology. He has studied marine mammal bioacoustics for 48 years and was not involved in Dent’s research.

    “We aren’t having to invent new technology,” he said, pointing to the Lab of Ornithology’s Merlin Sound ID app, which can identify 1,382 species of birds from their vocalizations in real time. He suspected that such an early warning system would cost in the range of six figures. “We’re not talking about tens of millions of dollars,” he said.

    Clark did note that the study was ambiguous as to whether signature whistles are an effective predictor of dolphin strandings, but he said that implementing such a system would be a good way to determine whether they are. Even knowing that a pod of dolphins is in the harbor at all could be useful information to responders, he said.

    Brian Sharp, the director of marine mammal rescue at IFAW, told the Independent in an email that he, too, believes there is potential in a system like this. Knowing that a stranding may be about to occur could allow IFAW volunteers to herd animals into deeper water before low tide and stage equipment and responders in key areas.

    Sharp thought one challenge might be for a system to distinguish between multiple simultaneous strandings from the same group of dolphins. One lone dolphin stranded on Eastham’s Thumpertown Beach in the early morning hours before the mass stranding happened in the Gut.

    Five Days of Strandings

    After the mass stranding in the Gut on June 28, a few dolphins continued to come ashore in the following days, Sharp wrote.

    On June 30, approximately 20 dolphins stranded in Brewster, with three dying before IFAW could intervene. The following day, IFAW was monitoring five or six animals in Wellfleet Harbor; one stranded and was transported in a dolphin rescue van and released into water at Herring Cove Beach in Provincetown.

    Tuesday, July 2, saw more strandings, with one dolphin on Rock Harbor Beach in Orleans, one on Boat Meadow Beach in Eastham, and 11 more in Wellfleet. The Orleans and Eastham dolphins were “humanely euthanized after showing signs of distress,” Sharp wrote, as were two of the Wellfleet animals. The other nine were released at Herring Cove.

    Of the 125 dolphins that stranded over a five-day period, approximately 20 died naturally and seven were euthanized. One dolphin was released at Herring Cove with a tracker and was later reported tracking around four miles northeast of Marshfield. IFAW believes it to be part of the same group and that this particular stranding is now over.

    Editor’s note: An earlier version of this article, published in print on July 11, incorrectly defined a mass stranding as involving more than one dolphin rather than more than two. The mass strandings in Wellfleet occur not just in the harbor but also in other locations in town.

    WELLFLEET HARBOR

    Stranding Stirs Dolphin Rescue Effort at ‘the Gut’

    125 Atlantic white-sided dolphins are trapped at low tide

    By

    WELLFLEET — Last week’s mass dolphin stranding here is thought to be the largest in at least a quarter century, and its causes may never be fully explained.

    Stranded dolphins were covered to protect them from sunburn. (Photo by Jack Styler)

    One hundred twenty-five Atlantic white-sided dolphins were found beached in the area between the Herring River and Great Island known as “the Gut” on the morning of June 28. Staff and volunteers with the International Fund for Animal Welfare (IFAW) rushed to Wellfleet from across the Cape to help. Ten of the animals had already died before rescue teams arrived.

    Scott Landry, director of the marine animal entanglement response team at the Center for Coastal Studies in Provincetown, told the Independent that determining why dolphins strand this way is the “million-dollar question that we don’t have answers for.”

    Dolphins are highly social animals, Landry said, “so, people tend to think that because one animal strands, the rest of the group will strand with them.” He thinks the pod likely came into Cape Cod Bay to feed on herring and menhaden. The Atlantic white-sided dolphin typically spends most of its life in deep water far from the coast.

    Stacey Hedman, IFAW’s director of communications, said the event was the largest of its kind in at least 25 years, but strandings are common in Wellfleet, especially around the mouth of the Herring River and Wellfleet Harbor. IFAW has 150 trained volunteers on Cape Cod and responded to 268 strandings last year in southeastern Massachusetts.

    “Cape Cod is a hook and Wellfleet is another hook within that,” said Hedman. “They’re not sick; it’s not climate change. We do this nearly every week, or definitely a couple of times per month.”

    IFAW responded in April to the stranding of 11 Atlantic white-sided dolphins in Wellfleet, three of which were in the Gut. Ten dolphins were saved after a seven-hour rescue operation.

    A Community Effort

    During last Friday’s efforts, at least 25 IFAW staff and 100 volunteers raced out onto the flats. Dolphins that were completely out of the water were covered with damp sheets to keep them wet and protect them from sunburn. Volunteers flipped partially submerged dolphins, which can weigh up to 500 pounds, to make sure their blowholes were out of the water and prevent them from drowning.

    Rescuers assess the situation. (Photo courtesy IFAW)

    In addition to the IFAW teams, rescuers from the Center for Coastal Studies, AmeriCorps of Cape Cod, the New England Aquarium, and Plymouth-based Whale and Dolphin Conservation came to help. Some nearby homeowners donated sheets and offered their laundry machines to muddy responders. At one point, there were not enough flotation devices to match the number of people willing to go into the rising water.

    Jerry Houser, who was visiting from Los Angeles and renting a house on Chequessett Neck Road with friends, saw the scene unfold from the porch where his group had been drinking coffee and looking over the Gut. He said it went from a “beautiful, serene thing with dolphins swimming in the water” to what “ended up looking like a war zone when all the water was gone.” By noon, their back yard had become the headquarters for the animal response teams.

    Misty Niemeyer, the on-scene incident commander for IFAW, said if the number of dolphins stranded had been smaller, she would have tried to extract them using a mobile rescue unit, which can hold up to nine animals at once. But because there were so many, she instructed her team to provide supportive care while waiting for high tide.

    By 2:15 p.m., the Gut had filled again with water deep enough that the dolphins could swim. From shore, volunteers could see pods looking for an escape route but sometimes swimming in the wrong direction. IFAW staff and volunteers waded in, splashing at groups venturing close to shore to drive them back into deeper water.

    By 3 p.m., a team of IFAW staff, Wellfleet Harbor workers, and paddleboarders began to herd the dolphins out of the channel and toward the harbor. They used boat engines and underwater noisemakers and slapped the water with their hands, according to Brittany Tilton, a staff member at the harbormaster’s office. Their efforts continued all afternoon.

    One witness said the receding tide revealed what looked “like a war zone.” (Photo by Jack Styler)

    “We went until the sun set, and we couldn’t see fins anymore,” said Tilton. By the end of the day, Tilton said most of the dolphins appeared to have made it out. At sunrise the next morning, however, IFAW volunteers were back, trying to save dolphins found stuck in the shallow waters near the Wellfleet pier.

    The operation carried over into day three on Sunday as IFAW returned to assist six or seven dolphins still in Wellfleet Harbor. One dolphin “was in poor condition,” so IFAW responders “humanely euthanized” it, according to a statement from Katie Moore, IFAW’s deputy vice president of rescue.

    “This is not only important for the welfare of that animal, but also helps us to be more successful in herding the remaining animals out,” Moore wrote. “The very social nature of these dolphins means that they will stick together even in a bad situation. By removing individuals that are not well, the group may be more easily moved offshore.”

    Hedman said the dead dolphins’ bodies often undergo necropsies and are sometimes donated to universities.

    On Sunday afternoon, IFAW responded to another stranding of about 20 dolphins in Brewster. Three had died of natural causes before they arrived. IFAW Director Brian Sharp said it was considered part of the same mass stranding, as some of the dolphins in Brewster on Sunday were part of the group in Wellfleet on Friday.

    An Emotional Toll

    All IFAW volunteers must complete a nine-hour training course and attend annual refreshers. Still, many volunteers appeared stunned by the sheer number of stranded animals.

    Teams arrive to help the stranded dolphins. (Photo courtesy IFAW)

    “I don’t pray, but if you do, it’s not a bad thing to do,” said IFAW volunteer Jeff Blaustein, who was watching the scene as the tide came in. “It’s heartbreaking.

    “People say, ‘Are they stupid? Why do they get stuck? Why do they get stranded?’ ” said Blaustein. “You ever kayak here? I kayak here every day. And I get lost over there, and I don’t know which way is out.”

    Jacob Dalby, the farm manager of Holbrook Oyster who often harvests in the waters near Great Island, said the area near the Gut can go from about 10 feet deep to just sand and mud quickly.

    “The tides are fairly extreme right now,” said Dalby. “It rushes out and rushes back in.”

    Animal strandings have long been a fact of daily life in Wellfleet. According to Dalby, Blackfish Creek in South Wellfleet is named after the pilot whales that used to strand there.

    “It was a huge community event when it happened,” said Dalby. “Everyone would hit the beach and start rendering all the fat when this happened 100 years ago.”

    Last weekend proved that strandings are still a community event, even if the reason for the people coming together has changed completely.

    THE SCUTTLEBUTT

    Dolphins and Cruise Ships Find Our Hidden Harbors

    Notes on playing safely as the season begins

    By

    Not much to report on the fishing front, as the water is still a bit too chilled to get things percolating. Striped bass continue their slow, deliberate trek to the north, but the word from the Canal and South Shore, where they first show up, is that it’s still pretty quiet.

    It’s 40 degrees and breezy as I write this. The weather this week looks like it will be a bit cooler than last week, which could slow the bass migration down somewhat. We are hoping these fish do not spend the entire spring on the South Shore and in Boston Harbor, as they have done for the past two years. There were enormous schools of pogies (menhaden) there, which held the bass for most of the summer; what we got was peripheral fish instead of the main body.

    A disturbing event took place in Texas this past week that is worth mentioning. A bottlenose dolphin stranded itself on Quintana Beach, just south of Galveston. There are a variety of reasons for dolphin strandings. Sometimes they’re just in the wrong place at the wrong time — here, in Wellfleet Harbor at low tide, for example. But it can also mean the dolphin is sick.

    Beachgoers in Texas, noticing the dolphin struggling, approached it to bring it out to deeper water. First mistake. Then, as they got it into deeper water, they attempted to ride it. Which stressed the animal so much that it died. There are no words to accurately describe the ignorance displayed by these people in their endeavor to entertain themselves.

    White-sided dolphins off Long Point. (Photo by Mike Rathgeber)

    Our white-sided dolphins have a tighter social dynamic than the bottlenose dolphin that stranded in Texas, and our dolphins will often follow the lead of an alpha, so strandings here frequently involve more than one animal. For the untrained person who happens to come upon a stranding, what you need to do is contact IFAW’s marine mammal rescue hotline, 508-743-9548. Please, let the experts handle this delicate situation.

    Humans should never initiate play with a dolphin in the water under any circumstances. Many years ago, I was a supply boat captain for offshore drilling rigs in the Gulf of Mexico, and we were often asked to tie up to the rig and wait for orders. On very hot days, while standing by, we would dive off our boat to go for a swim and cool off. Every now and then a few bottlenose dolphins would come over to check us out and play. They loved to charge at us and, at the last minute, swim underneath us. But that was their game, not ours. We let them be and did not interfere with their play. Usually, after a few minutes of this, they would swim off to do something else. These are extremely intelligent mammals who have reasons to do what they do. My guess is they are smarter than the humans who tried to ride them in Texas.

    On the subject of play, we’ll be visited twice by the Ocean Navigator this week, once on Wednesday (though rough seas coming across the bay may mean they head straight from Newport to Boston) and again on Saturday.

    Although it is marketed to cruise-goers as a ship that’s small enough to “easily navigate hidden ports,” this 299-foot 1,580-ton vessel with a crew of about 80 and carrying about 200 guests is too big to dock here. It will instead drop anchor outside the breakwater and be tendered.

    The season has begun.

    STRANDINGS

    Responding to Stranded Mammals

    By

    Tracks left by marine mammal rescuers were visible from the air after three common dolphins were found stranded at Bee’s River Marsh, near First Encounter Beach in Eastham on January 2. By the time a team from the International Fund for Animal Welfare (IFAW) arrived at the scene, all three dolphins had died.

    Dolphin strandings are not uncommon in the winter and early spring, but there have been more than usual so far this year, said Olivia Guerra, stranding technician and the Marine Mammal Rescue and Research division of IFAW.

    Common dolphins, like other pelagic marine mammals, are accustomed to the open sea. “They don’t understand tides,” said Guerra, so when their food source swims close to the shore, stranding becomes a risk.

    Between Christmas and New Year’s Eve, IFAW responded to 40 cases of stranded marine mammals. Most of them were dolphins, Guerra said, but one was a humpback whale found at Race Point in Provincetown.

    On Jan. 3, IFAW responded to three live dolphins stranded behind the Audubon Sanctuary in Wellfleet; one dolphin died before responders arrived but two were relocated and released at Herring Cove. On January 10, the team responded to another live stranding in Wellfleet, at the Herring River Gut. The female common dolphin was tagged and released at Herring Cove.

    The best thing to do if you encounter a stranded marine mammal, said Guerra, is to keep back, keep quiet, and call the IFAW hotline: 508-743-9548. —Tessera Knowles-Thompson

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