A surge in strandings of dolphins, other marine mammals on Cape Cod

— -- Dolphin strandings on Cape Cod in Massachusetts are unusually high this year, with a particularly significant increase in the number of females with calves getting beached, a marine-mammal rescue organization said.

Seven dolphins, two pregnant, that were rescued Friday from the mudflats of a river on Cape Cod are among the most recent marine mammals that were found stranded in the area.

In strandings, marine mammals — including dolphins, whales, porpoises and seals — come ashore, alive or dead.

The hook-shaped Cape Cod, which juts out about 70 miles into the Atlantic Ocean, is one of only a few places in the world where mass strandings — two or more whales, dolphins or porpoises getting beached at the same time — occur regularly, according to the International Fund for Animal Welfare, which regularly responds to strandings on Cape Cod.

The seven dolphins found stuck in the mudflats in Wellfleet, Massachusetts, were freed Friday by more than a dozen rescuers from the group, with the help of Wellfleet town staffers, Kerry Branon, a spokeswoman for the IFAW told ABC News in an email.

An examination by a veterinarian and experts at the site found the dolphins to be healthy. "Ultrasound exams showed that two of the females were pregnant," Branon said. The seven dolphins were taken by trailers to another beach, "where they were successfully released."

The IFAW documented the release on Facebook Live.

"Cape Cod is a global hot spot for dolphin mass strandings," Brian Sharp, a manager at the IFAW, wrote in a March 1 press release. "Unlike strandings in recent years, these recent events appear to be somewhat different."

"One significant difference is that these dolphins are primarily females with calves, versus the norm over the last decade of a high proportion of young males. These females and calves seem to be exhibiting higher levels of stress and shock, and many are not surviving the initial physical impacts of the strandings like dolphins have in previous years," he wrote.

Sharp added, "Due to the high number of stranded animals, our team of experts is investigating each event and hopes to know more once results from clinical test are received."

Earlier last week, two dolphins — a mother and calf — were found in a shallow creek on Cape Cod, and five more dolphins were discovered later in the day, he wrote. The mother and calf were treated for shock and transported for release. Three of the other five dolphins died shortly after their stranding, but the remaining two were released.

That was just one day of a busy week for the IFAW's marine mammal rescue and research team, which Sharp heads. In one week beginning Feb. 22, it responded to seven strandings of dolphins and harbor porpoises, saving 20 animals.

Marine mammal standings are generally attributed to a variety of causes.

Many species of whales and dolphins are highly social animals that, like humans, depend on the group to survive, according to an IFAW fact sheet.

"This group mentality that is so helpful to these animals at sea can unfortunately cause otherwise healthy animals to strand en masse when they are near shore. When one animal enters shallow water or strands, the entire group may follow," the fact sheet states.

Marine mammals may become stranded when they swim too close to shore to pursue prey or avoid predators like sharks. Extreme weather can also play a role.

Last month in New Zealand, hundreds of pilot whales became beached along a remote area of coastline in one of the country’s worst strandings on record. Many of them died before rescuers were able to save them.

Some scientists and conservation groups say climate change and its effect on sea temperatures and the frequency of extreme weather events pose a severe threat to marine mammals. Whale and Dolphin Conservation, a U.K.-based wildlife charity, says climate change may be one of the biggest threats facing whales and dolphins today.

"The climate is changing fast — so fast that some whale and dolphin populations may be unable to adapt," the organization says on its website. "Changes in sea temperature, freshening of seawater, acidification, sea level rise, loss of icy polar habitats and the decline of food sources are just some of the many threats posed by climate change."