Why are dead dolphins washing up on Delaware’s beaches?

May 29, 2019 GMT

LEWES, Del. (AP) — Watching dolphins playfully swim along the horizon can be a treat for Delaware’s beachgoers, but sometimes people get a much closer look at marine life for unfortunate reasons.

That’s what has been happening along the Delaware coast recently, with 12 dead dolphins washing up on bay and ocean beaches over the last couple of months.

They included a decomposed bottlenose dolphin calf found on the coast near Wilmington Avenue in Rehoboth Beach on May 25 and another at Cape Henlopen State Park on Memorial Day.

“I’m not seeing anything out of the ordinary whatsoever at this point,” said Suzanne Thurman, executive director of the Lewes-based Marine Education, Research and Rehabilitation Institute. “It’s always note-worthy, but it’s not a spike.”

It remains unclear what caused many of those deaths because most of the dolphins that washed ashore were largely decomposed by the time MERR officials arrived. In an ocean filled with predators and scavengers, as well as the sun beating down on hot days, it can often be a challenge to get good enough tissue and fluid samples to figure out what happened.


When MERR experts can do a full necropsy of the animal, which is akin to an autopsy, the carcass is then composted, Thurman said. In other cases, especially when something like a whale washes ashore and is too heavy to be relocated, it will be buried safely on the beach so it can take a new place in the beach ecosystem and food web.

Thurman said she was able to gather some samples from an adult striped dolphin that recently washed ashore at Middlesex Beach, between Bethany and South Bethany beaches.

“That’s more unusual,” she said of seeing a striped dolphin. The last time Thurman saw a striped dolphin wash ashore in Delaware was in 2002, when five were stranded at the Indian River Inlet during a strong snow storm, she said.

The 12 dead dolphins MERR has responded to so far this year included eight bottlenose dolphins, three harbor porpoises, one common dolphin and one striped dolphin. Some were found along Delaware Bay beaches in the area of Bowers Beach and Slaughter Beach in late April while others were found along the ocean beaches.

A 13th dolphin could have been added to the list when it washed ashore in Lewes on May 26, but MERR experts didn’t get a chance to check it out because beachgoers pushed it back into the water, Thurman said.

People certainly mean well,” she said, urging people to never touch a dead or stranded marine animal. “If an animal is stranding onshore, it means something is wrong with it and it needs assistance. The average person isn’t going to be trained to look for certain things that can give clues about the overall health of an animal.”

It’s also against the law to interact with protected marine mammals. That’s why people need to keep their distance, while in the water or on land, for their own safety and the safety of the animals.


“They’re certainly out there living their lives and frolicking,” Thurman said. It may sound fun to swim with dolphins, but in the wild and at this time of year, mothers are nursing their calves and just a nudge from a 1,000-pound expert swimmer can mean bad news for the even the most skilled water-lover.

If a dolphin calf is struggling in the water, that’s a good sign that sharks also may be present. Anyone who spots a marine mammal or sea turtle stranded or in distress should keep their distance and call MERR’s 24-hour hotline at 302-228-5029.

Thurman said it’s quite common to see calves in the area in May and June. Bottlenose dolphins, one of the most common species along the Delaware coast, usually give birth to one calf at a time and are known to nurse them for three to six years.

While deceased dolphins are sad news, the numbers are not out of the ordinary. This time last year, Thurman was concerned about an uptick in bottlenose dolphin strandings. Thirteen had washed ashore in a matter of a few weeks. No definitive common denominators were discovered, she said.

The most notable issue with dolphins stranding in Delaware was between 2013 and 2015, when a disease called Morbillivirus sparked an unusual mortality event among bottlenoses. During that event, more than 1,600 of them stranded along the East Coast from New York to Florida. Delaware saw 74 of those during that two-year span, according to data from the National Oceanic and Atmospheric Administration.

While it will be hard to say what happened to the dolphins found so far this year, it is likely a combination of natural causes and interactions with fisheries activities. Three adult dolphins found at the bay beaches did show signs of getting caught in fishing line, Thurman said.

Delaware sees an annual average of about 17 strandings a year. Last year there were 21, she said.

But Delaware is not alone in dealing with these.

Earlier in May in Florida, two dolphins stranded on the beach with their bellies full of trash. One, a male bottlenose dolphin, had eaten a 24-inch-long plastic shower hose, nozzle and all. The other, a female rough-toothed calf, was found to have two plastic bags and a balloon fragment in her stomach, according to the Fort Myers News-Press.

Plastics pollution in the ocean will be the focus of MERR’s celebration of World Oceans Day on June 8. It will include a beach cleaning and guest speakers offering insight on how individuals can reduce their own footprint. For more about the event, which will be from 9 a.m. to noon at the MERR office at 801 Pilottown Road in Lewes, go to www.facebook.com/events/2363348780389995.


Information from: The News Journal of Wilmington, Del., http://www.delawareonline.com