BOSTON—Scientists are struggling to explain the stranding of
31 dolphins and a pilot whale off the coast of Massachusetts since the start of
the year, including some found with brain deformities or chronic diseases.
Eight Atlantic White-sided dolphins were found on Tuesday,
following 23 dolphins, a pilot whale and a seal discovered since January 1 in
the hook-shaped Cape Cod region and its maze of sandbars and marshes that are a
magnet for tourists in summer.
The number is unusually high, according to the Cape Cod
Stranding Network that oversees rescue efforts. It typically averages 200
rescues a year, compared to 31 rescues performed in the last 10 days alone.
At least 14 of the dolphins have died, including two which
were euthanized, the network said. The strandings involved Atlantic White-sided
dolphins and so-called common dolphins, neither of which are endangered.
Scientists say it’s unclear why so many of the dolphins have
been stuck. About 100 dolphins beached themselves in roughly same area on Cape
Cod over six weeks last winter.
Sarah Herzig, who oversees rescue work at the CCSN, said they
may have become beached during a recent full moon that affects tides or that
unseasonably warm water could have affected the migration of fish that they
typically feed on.
Initial studies showed some suffered chronic diseases.
Katie Pugliares, who dissects dolphins at the CCSN to
determine how they died, said she had seen a range of chronic diseases including
peritonitis, or fluid buildup in the intestinal cavity, and lymph node
inflammation.
She also found chronic brain deformities and brain lesions,
which could have been caused by encephalitis, parasites or bacterial infection
of the brain.
Pugliares added that it cannot be known for sure which
infections caused the animals to die until pathology results return from the
laboratory, which can take weeks or months.
She declined to specify how many of the dissected animals
suffered from the conditions she found but added that the diseases may have been
a result of being stranded instead of actually causing the mammals to beach
themselves.
"Sometimes the ones that die have symptoms associated with
strandings because when they strand, they become sick," she said.
Herzig said some of the pregnant females which rescue workers
are trying to save were faring poorly.
Tony LaCasse, spokesman for the New England Aquarium, said
marine biologists are finding that some of the dolphins are suffering from
underlying conditions different from previous years but that the strandings were
still being studied.
"If animals are under food stress, it might be opportunistic
for certain infections to take hold," he said.
He added that some kind of viral outbreak, environmental
conditions and bacteria in the water could have also been contributing factors.
Dolphins typically exhibit empathetic behavior by not leaving sick dolphins
in their school behind, and this also may explain why so many became stuck,
LaCasse and other scientists contacted by Reuters said.
