Several more dead seals washed ashore Tuesday in York County, adding to an unusual die-off that has local and federal experts searching for an explanation.

The discovery of at least 35 dead harbor seals on southern Maine beaches in the past three days, including 11 found Monday in Saco, comes amid an unexplained surge in the number of dead and stranded live seals in both southern Maine and New Hampshire in the past two weeks, the National Oceanic and Atmospheric Administration said. NOAA researchers are analyzing tissue samples taken from dead animals found in both states to try to determine if avian flu, harmful algal blooms or some other cause is behind the increase in the number of dead and sick seals.

“It’s obviously a cause for concern,” said Jennifer Goebel, a NOAA spokeswoman.

So far this month, 84 harbor seals have been found dead or stranded on southern Maine beaches, far outpacing the 10-year average of 38 strandings in the entire month of August, NOAA said. Many of the dead and stranded seals have been pups.

Whatever is killing the seals also may be leaving others sick or weak.

Maine rescuers took in two live stranded seals Tuesday, putting a midcoast rehab facility at capacity at a time when similar facilities across New England also are filled with an unusual number of sick or weak seals found stranded along the coast.

Goebel said scientists are looking for possible pathogens that have caused seal die-offs in the past, including avian flu and harmful algal blooms. In 2011, more than 160 seals were found dead on the coast from northern Massachusetts to Maine between September and December. Tests conducted on five animals showed they suffered from a bacterial pneumonia caused by a strain of avian influenza – H3N8 – that can be transmitted to seals through contact with seabird guano. 

Lynda Doughty, executive director of Harpswell-based nonprofit Marine Mammals of Maine, which responds to seal strandings, said her organization is working with NOAA to investigate the seal deaths.

That work includes thinking about different types of sampling to do on the seal carcasses and who else to bring into conversations about what is happening to the harbor seal population in the area, she said.

“We’re making sure we’re not leaving anything out,” she said.

Answers about the cause of the die-off are not likely to come quickly. Goebel said it will be several weeks before results are received from the tests being done by NOAA scientists.

Saco officials were first notified about multiple dead seals on the beach early Monday morning and lifeguards arriving for duty found a total of 11 carcasses on Bayview and Kinney Shores beaches.

Most of the seals found in Saco were harbor seal pups, although the ages of the seals varied widely, Doughty said. The seals were in various stages of decomposition and none of the carcasses were fresh, which makes it more difficult to determine when the animals died, she said.

The seal carcasses removed from the beaches in Saco were taken to Benson Farm in Gorham, which composts sea animals, including whales.

By Tuesday morning, Marine Mammals of Maine had responded to reports of four more seal deaths along the southern coast, including in Saco and Harpswell. The organization also took two live juvenile harbor seals found stranded on beaches to its facility in Harpswell for treatment.

Doughty said the arrival of those two seals put the facility at full capacity. The facility can accommodate four animals for long-term care and triages seals out to facilities in other states. But those out-of-state facilities are now also full.

“For this time of year, that’s unusual,” Doughty said.

She said it is normal for the facilities to be full in late May during harbor seal pupping season, but less common later in the summer when juvenile seals are more independent.

Harbor seal pups can swim at birth and can dive for up to two minutes when they are only 2 or 3 days old. Mother harbor seals raise their pups in nurseries that help protect the pups from predators.

Historically, about 30 percent of all harbor seal pups born in any year die that year, according to the New England Aquarium.

Marine mammal experts say people should report any dead or stranded seals spotted on beaches, but should stay at least 100 yards away and make sure dogs don’t go near the animals. Stranded or dead seals found between Kittery and Rockland can be reported to Marine Mammals of Maine at 800-532-9551 or to NOAA at 866-755-6622.

Seal #108, a young female pup about three months old, at the Marine Mammals of Maine rehabilitation center on Tuesday, August 14, 2018. The organization has responded to over 40 seals in the past three days, 37 of them dead, and 11 of them alive and they are trying to figure out the cause of the uptick in deaths. The organization’s rehab center is currently full with four seals, including #108 who they rescued at the end of June, and the rest of the facilities in the Northeast are at capacity as well. (Brianna Soukup/Portland Press Herald)