Nightly News | February 15, 2012
>>> for about the past month, a muddy shallow spot on the cape cod coastline has been the scene of tragedy and mystery, as more than 175 dolphins have beached themselves there experts are racing to try to save those that they can and to try to figure out why it's happening. our report here tonight from our chief environmental affairs correspondent anne thompson .
>> reporter: winter reveals cape cod 's stark shoreline and the stranding of dolphins. these majestic creatures coming to shore in record numbers, 177 and counting. the vast majority dead. katie moore of the international fund for animal welfare leads the team identifying, catalogs and in 53 cases, rescuing and releasing the dolphins. along a 35-mile stretch of the cape's interior coastline, the hook shape of the peninsula traps the dolphins in cape cod bay .
>> once in the bay, they can't find their way out.
>> reporter: here the rise and fall of the tide is dramatic, a difference of 13 feet where we walked. this winter, when the tide goes out, trouble comes in. a half mile offshore, this sand bar is a dolphin graveyard. so far we found six just in this area alone. researchers measure, take samples and tag each and every dolphin, hoping science can't decode the mystery. is there anything on this dolphin that would explain why it's stranded? there are lots of theories. the warm winter is one. when was the last time you saw ice in the harbor?
>> probably three years ago.
>> reporter: welsey harbor master has bigger worries.
>> it makes you wonder if there is something terribly wrong with the environment.
>> reporter: is it a feeding problem or the social nature of the dolphins? from her vantage point high above wellesly, peg needs no explanation.
>> it's part of their world and they know what they are doing and we don't. moore says the reason is critical.
>> they are sentinels, giving us a glimpse into the health of the ocean ecosystem as a whole and cape cod bay .
>> reporter: a boundful ocean keeping the secret to this mystery. ann thompson, nbc news, brewster, massachusetts.