(Cape Cod Times)
A shift in caring for stranded dolphins
By Mary Ann Bragg
mbragg@capecodonline.com
February 19, 2012 2:00 AM
When dolphins stranded in large numbers on Cape Cod beaches 25 years ago, they were usually killed to alleviate their pain and suffering.
It was only in the past two decades that marine mammal specialists began to successfully assist back into the water animals like the common dolphins, which have been grounding in great numbers along Cape Cod Bay since mid-January.
Research from the 1990s in Cape waters laid a path for what have become successful release techniques for stranded whales, porpoises and dolphins, and this year's use of satellite tags to track released common dolphins is extending scientific knowledge further, said research coordinator David Wiley at Stellwagen Bank National Marine Sanctuary. The sanctuary, with a staff office in Scituate, is administered by the National Oceanic and Atmospheric Administration.
"In the past, people believed that there was nothing you could do for them," Wiley said.
In recent weeks, the Cape has attracted international attention because of the unusually high number of stranded common dolphins. As of Friday, 179 had stranded along the bay's shoreline from Barnstable to Wellfleet in mass stranding events that have occurred almost daily, according to the International Fund for Animal Welfare, which has federal authorization to respond to strandings on Cape Cod.
Fifty-three of the dolphins, about 30 percent, have been successfully released into deep waters. The remaining 126 were found dead, died before or after release, or were euthanized.
By comparison, the total count for an entire year of stranded common dolphins, white-sided dolphins and pilot whales in Massachusetts peaked at just over 100 in 2006, based on data between 2000 and 2011, federal records show.
A mass stranding is defined as one in which two or more adult marine mammals are grounded together.
Tops for strandings
Cape Cod is among the top locations in the world, along with Australia and New Zealand, for naturally occurring mass strandings of toothed whales, according to Regina Asmutis-Silvia of the Whale and Dolphin Conservation Society, which has an office in Plymouth. Toothed whales are a subset of marine mammals that includes dolphins, porpoises and some whales.
In the U.S., strandings of pilot whales and other types of dolphins occur in the Florida Keys and along the Panhandle of Florida as well, according to marine mammal biologist Trevor Spradlin of NOAA.
"The whole Cape Cod experience, which is now being run nicely by IFAW, is really one that's been shared with the world in a very important way," Wiley said. "(It has shown) that the animals can survive, and what the methods are that you can use to ensure they will survive."
Study: They can survive
Wiley was one of the four researchers who provided that evidence, in a review of 17 mass strandings on Cape Cod from 1990 to 1999.
The study, published in the scientific journal Aquatic Mammals in 2001, suggested that with proper equipment and procedures, the animals could safely be transported to release sites of considerable distance.
The researchers also found evidence to suggest that the released animals did not inevitably re-strand, as was previously believed, and that it was possible to make a quick assessment of stranded animals to determine which ones were the best candidates for a successful release.
The researchers studied 376 stranded pilot whales, white-sided dolphins and common dolphins, and the subset of 73 that were released. Sixty of those — 16 white-sided dolphins, six common dolphins and 38 pilot whales — did not strand again after release, the report showed.
The study included the work of Greg Early, who was representing the New England Aquarium in Boston, Charles "Stormy" Mayo of the Provincetown Center for Coastal Studies and Michael Moore of the Woods Hole Oceanographic Institution.
The study didn't take on the larger task of determining whether the released animals survived over longer periods in the open sea, the report stated. The placement in recent weeks of temporary satellite tracking tags on 11 released common dolphins on Cape Cod is part of the effort to gain more information on their deep-sea survival, Wiley said.
Because of the expense, only a subset of the dolphins is tagged, but tracking a few can give researchers an idea where the larger group is headed, according to Brian Sharp of IFAW. The tags are designed to drop off the dolphin after a few weeks.
On Friday, six of the 11 satellite tags were still transmitting data and showed the dolphins "swimming outside of Cape Cod Bay and displaying normal behavior," said Michael Booth of IFAW. (Click to view a map of the routes taken by the satellite-tagged dolphins.)
Navigational error?
The common dolphins appearing this year in Cape waters are protected under the federal Marine Mammal Protection Act of 1972, but they are considered abundant worldwide, federal records show. The dolphins typically travel in large social groups, averaging several hundred animals, in deep waters and offshore.
On the East Coast of the U.S., they are more common north of Cape Hatteras, N.C., and during summer through autumn are often found in large groups northeast of Cape Cod.
"This particular situation that we're experiencing in 2012 is indeed more than what we've experienced in the past," said NOAA biologist Spradlin. "There are lots of theories — oceanographic features and the unique aspects of the geology of the Cape. This has been happening for hundreds of years, even before the Industrial Revolution."
Wiley said he believes this year's strandings on Cape Cod are "really more of a navigational error on the part of the animals," given their usual offshore habitat and the tidal and water depth changes that occur along the bay's shoreline.
"They stay in what they think is deeper water, and as the tide goes out it becomes shallower and shallower, and they become stuck," Wiley said.
Moore, also, is thinking about the causes of the strandings this year.
As a senior research scientist at WHOI, he serves as the veterinarian for IFAW's marine mammal rescue effort. He and his colleagues have performed necropsies on at least nine common dolphins from the recent strandings.
2-degree difference
Examining beached marine mammals is one of three ways the federal government can observe and assess the animals and manage their conservation, Moore said last week. The other two ways are to place an observer on commercial fishing vessels, and to conduct surveys to count them.
The information gleaned from the necropsies of the common dolphins, for example, is added to federal databases to allow for regional and national assessments of how the animals are faring, he said.
"My perspective at the moment is that we're not seeing anything unusual other than the numbers," Moore said of the Cape strandings. "There's no pattern of difference that's striking. Essentially what we're seeing is much more of the same. Obviously the numbers are substantially greater. Therein lies the question, more of the same but no different."
One marked difference that has been determined this winter is an increase in surface water temperature of the bay of 2 degrees Celsius, both Moore and Mayo said this week.
Mayo has documented the temperature change as part of his study of North Atlantic right whales in the bay.
"I wouldn't want to say that climate is driving this," Moore said. "But the climate is certainly different. The temperature has changed. The water is warmer this year than it normally is."
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