WELLFLEET, Mass. — The thin, swoop-and-dip whistles that Atlantic white-sided and common dolphins emit may help humans save them from stranding, based on a study in Wellfleet Harbor.
“The idea of this was prevention,” said Woods Hole Oceanographic Institution biologist Laela Sayigh, the study co-leader, of the potential use of dolphin sounds along with factors like tidal state, lunar cycle and wind speed to predict – and avert – a mass stranding.
In the last two years, a grant-funded underwater data recorder off Jeremy Point has gathered 15 to 30 minutes of sound for every hour, including what are believed to be dolphin whistles, fish swimming by, boat motors and other noises. Study team members have been sorting through the data and matching the whistle information, when possible, with dates of reported sightings of Atlantic white-sided and common dolphins in the harbor and with documented mass stranding events.
“The goal was not to develop a system but to test its feasibility,” Sayigh said.
The need for an advance warning is great, stranding experts say.
The International Fund for Animal Welfare has responded to 389 standings in the region this year, as of Friday, marking the busiest season on record. While there is heavy stranding activity along the Cape Cod Bay shores from Barnstable eastward, Wellfleet Harbor tends to be a hotspot, often for mass strandings of two or more adults together.
The causes of strandings are not known but theories include the animals making navigational errors given their usual offshore habitats and the tidal and water depth changes that occur along the bay’s shoreline.
“Earlier detection, interception and redirection (of the animals) could reduce animal stress,” said IFAW stranding technician Kathryn Rose. IFAW could use an early-alert system to herd the animals away from shallow waters and potentially prevent strandings, Rose said. Avoiding strandings would protect shellfish beds and other ecosystems that can be damaged, as well as saving time and money for both IFAW and the town of Wellfleet.
An average estimated cost of a response to a stranding was not available, due to the unique circumstances in each case, IFAW spokeswoman Melanie Mahoney said.
“It was quite an ordeal, and quite an expensive one,” Wellfleet Harbormaster Michael Flanagan said, recalling a stranding of pilot whales several years ago off Lieutenant Island.
Out of the 100 distinct sound “contours” recorded between August 2016 and April off Jeremy Point, Sayigh and other team members are still determining which ones meet the criteria for being a type of dolphin whistle unique to each animal, called a “signature” whistle. The data appear to show, though, that a few days before a stranding and at the time, dolphins emitted signature whistles more often than other whistles in their repertoire.
Also, as a stranding event loomed, the data appear to show that the dolphins emitted their signature whistles more frequently.
“The next step, if we can find the funds, is to get the system to where there is a real-time alert for significant numbers of dolphins in stranding hot spots such as Wellfleet Harbor,” said WHOI marine researcher and veterinarian Michael Moore, also a study co-leader, whom Sayigh credits with the idea of creating an advance warning system for mass strandings.
The idea of listening for dolphin signature whistles prior to strandings in Wellfleet Harbor came from scientific studies in Florida, which Sayigh participated in, where bottlenose dolphins had produced signature whistles in higher rates during brief capture-and-release health assessments.
After a study of 17 mass strandings from 1990 to 1999 on Cape Cod, marine mammal experts learned that healthy stranded animals could be transported and released in deeper waters. Prior to that, the animals would have been killed to alleviate their pain and suffering.
“People are extremely concerned,” Flanagan said of the response of bystanders to strandings. Most people know to call the IFAW stranding hotline right away, he said. “If not, it’s the first thing I do,” Flanagan said. “Then we respond. The birds go after them and try to kill them. We try to assist the best we can and help them out until IFAW arrives.”
Information from: Cape Cod (Mass.) Times, http://www.capecodtimes.com