Higher rate of strandings began in 2016
Karen Clark, director of the Outer Banks Center for Wildlife Education in Corolla, said only one beached whale recovered in the past several weeks was found in a condition allowing for a “complete examination.” That humpback whale, recovered in Corolla on Sunday, Feb. 17, had a necropsy performed by members of the Outer Banks Marine Mammal Stranding Network. Findings, Clark said, included “areas of what looked like hemorrhaging under the blubber on its dorsal surface or back.”
She added there was also reason to suspect “there were some bone fractures as well, underneath that.” These findings, she said, all tentatively point to the probable cause of death being a ship strike. “We have some histological samples that will be able to confirm that it was hemorrhage and not just post-mortem pooled blood. It’s very likely that it happened before death and that it was the cause of death.”
Other recent deaths include a humpback whale found the same day near Sandbridge, VA in the Back Bay National Wildlife Refuge, and another found on Feb. 12 north of Oregon Inlet near Nags Head.
A pygmy sperm whale was also found a week earlier in the waters off Nags Head.
Performing a necropsy on that whale, Clark said, "We found an area of bruising, but it also had a lot of worms in its stomach and so may have been compromised to begin with.” There were no broken bones indicating impact from a ship strike as the cause of death.
Being "compromised," Clark explained, the whale could have been in a weakened condition and “more susceptible to parasites and less able to run away from predators, which made a heavy blow to its side. That could have been a story that that animal was telling, but I didn’t feel that we had conclusive enough information to really determine that.” She said predators could include sharks or other larger marine mammals.
With an observed “uptick in larger humpback whales that were stranding,” NOAA declared an Unusual Mortality Event (UME) in 2017 and back-dated it to 2016, when the deaths really started. NOAA is now continuing to monitor this UME as an “ongoing event.”
“During the winter we do get a number of strandings," Clark said, "but to have three whales in the general region is not typical. The Outer Banks typically gets two or three humpback whale strandings in an entire year, and in one month we’ve gotten two of them.”
The one whale's cause of death has been declared a vessel strike, she added, but the others have not been determined.
Clark stressed the need to continue to monitor the strandings. “If anyone sees dolphins, whales or porpoises that have stranded on the beach," she said, "they should always report them, because it is always something worth investigating." Strandings should be reported to the Outer Banks Marine Mammal Stranding Network at 252-455-9654.
NOAA reports on its UME website —
www.fisheries.noaa.gov/national/marine-life-distress/2016-2019-humpback-whale-unusual-mortality-event-along-atlantic-coast — that the "elevated humpback whale mortalities" that started in January 2016 have continued to occur "along the Atlantic coast from Maine through Florida." A total of 84 have died in the past three years. The report adds that a "portion of the whales have shown evidence of pre-mortem vessel strike," but more research is needed. The monitoring and study will continue.