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 Jan. 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.
Pregnant females
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.
(Por Julie Masis,
Planet Ark, 11/01/2007)