More strandings are expected after 129 dolphins beached themselves on Cape Cod in the last three weeks, with 92 dying in "the single largest stranding" of dolphins in the Northeast since at least 1999, the International Fund for Animal Welfare reported Monday.
On Sunday, four dolphins were stranded along Cape Cod's hook-shaped peninsula and were quickly helped back to sea. The Massachusetts peninsula sees many dolphin strandings each year, but the 129 since Jan. 12 is typically about what rescuers see over an entire year, based on records that go back to 1999, IFAW marine mammal rescue manager Katie Moore told msnbc.com.
"This event started on the 12th and is still continuing," she added at a press conference on Monday, noting that rescuers from IFAW and other stranding networks were deployed in "anticipation of more dolphins coming in."
The National Oceanic and Atmospheric Administration, which manages the rescue response, echoed the concern.
For common dolphins, the species that has been stranding in Cape Cod, "this is the largest, most protracted stranding event in recent decades," Teri Rowles, who coordinates NOAA's Marine Mammal Health and Stranding Response Program, told msnbc.com.
Most of the dolphins have appeared to be in good health, adding to the mystery of why so many have come ashore. Common dolphins are known to strand in groups due to their tight social structure, but given the large numbers this year, other factors such as weather and tides are being investigated.
Michael Booth / IFAW
IFAW rescuers respond to nine dolphins stranded in Brewster, Mass., on Feb. 1. All nine were able to get back out to sea.
"I don't know," Moore said when asked about causes. "It pains me to say those three words."
Asked if climate change might be a factor, Moore said she couldn't rule that out or in. As for the possibility of sonar or other human-made sounds disrupting the dolphins, she said no known sources existed inside Cape Cod.
Initial results of studies on nine of the dead dolphins "do not indicate any pattern," she noted.
This stranding "is not only out of the ordinary," she said, "but it takes a huge toll on our resources. It's hard labor."
Rowles noted that "Cape Cod is the hot spot in North America" for mass strandings, and that "there seems to be a lot of variability each year."
The large numbers have "made the response effort very difficult" and "left us confused about what's going on," IFAW biologist C.T. Harry earlier told NBC affiliate WHDH TV.
IFAW's satellite tracking system shows the routes of several tagged dolphins through Jan. 26. Cape Cod is at bottom center of the map.
IFAW has tagged several dolphins that survived with satellite tracking devices to see if they are leaving the area. So far at least, they have stayed in deeper waters.
IFAW on Friday briefed some U.S. lawmakers about the mass strandings and urged Congress not to cut the federal program that helps fund stranding research and response networks nationwide.
"If scientists do not have the funds to determine the cause of a mass mortality event, there could be a threat to public health without anyone knowing," IFAW President Fred O'Regan wrote on his blog last week.
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