As harbor seal pupping season picks up along the Maine coast, researchers continue to keep an eye out for signs of an ongoing outbreak of phocine distemper virus that has been killing seals.
So far this year, seal watchers in the Northeast have noticed an elevated number of grey seals stranded on beaches — which, for baby seals that have not been weaned, could be a sign that their mothers are sick — but they haven’t noticed the virus yet in seal pups.
Since last July, 2,290 grey and harbor seals have been reported sick or dead along the East Coast between Maine and Virginia, according to federal statistics that were updated last week. That is at least three times the number of any previous outbreak affecting seals that the National Oceanic and Atmospheric Administration has documented since 1991.
Of those strandings, 1,179 — more than half — have been reported in Maine. Massachusetts, the state with the second-highest total, has had 627.
NOAA keeps tabs on marine mammals and turtles, which are protected under federal law, and investigates the cause when any protected species experiences a concentrated number of deaths over any given time, which the agency calls unusual mortality events, or UMEs.
Phocine distemper virus, also known as phocine morbillivirus, does not affect humans but it can affect dogs and other pets.
Federally authorized groups in Maine such as Allied Whale at College of the Atlantic in Bar Harbor and Marine Mammals of Maine respond to reports of dead or distressed seals throughout the year. Their busiest time of year is in the spring, when harbor seal pups frequently are spotted alone along the shore while their mothers are feeding at sea. Those that are sick or appear to have been abandoned are taken to rehab centers and nursed back to health so they can be released into the wild.
Grey seals give birth in winter, generally from December through February, while harbor seals, which are more abundant in U.S. waters, generally are born from late spring until early summer.
So far in 2019, there have been 263 reported grey seal strandings between Maine and Virginia, which is approximately 80 more than the annual average from 2008 through 2017, according to Ainsley Smith, regional marine mammal stranding coordinator for NOAA. Grey seal strandings last year, in 2018, also were well above the 2008-2017 average, with 560 reported in the same multi-state region.
Of the 263 grey seal strandings reported so far this year, none have tested positive for the distemper virus, sometimes referred to as PDV, Smith said Wednesday. She said that several young grey seals have tested positive for antibodies that fight the virus.
“These animals had maternal antibodies for PDV,” Smith said. “This means that mom was exposed to PDV and survived, and shared protective antibodies through their milk to their pups. These antibodies only last roughly eight to 16 weeks and protect the pup during that time.”
Lindsey Jones, marine mammal stranding coordinator for Allied Whale, said Wednesday it is too early to tell if the ongoing virus outbreak is having an effect on Maine’s 2019 harbor seal pupping season. The group has responded only to four reported strandings of harbor seal pups in eastern Maine so far this spring, but typically responds to 50 each year between late April and early July.
Of those four, two stranded pups were born prematurely, one of which had to be euthanized, she said, which is not unusual. Another that was found May 11 on a Brooklin beach seems to be doing well at the Marine Mammals of Maine triage facility in Harpswell. Allied Whale staff left the most recent one alone on the beach for a couple of days until they determined it had been abandoned by its mother, according to Jones.
“It was losing weight and getting dehydrated,” Jones said. “It is rare to observe a mother harbor seal with its pup because the mothers spend most of their time in the water feeding to restore their energy stores after giving birth. A mother seal will not return to feed its pup if it senses humans or dogs near the pup.”
Federal law requires the public to stay at least 150 feet away from any seal beached along the shore. Marine mammal strandings anywhere in Maine can be reported by calling 800-532-9551. If the animal is anywhere on the coast between Rockland and the Canadian border, the stranding can be reported to Allied Whale at 207-288-5644, Jones said.