The International Fund for Animal Welfare, in Yarmouth, is calling this week’s stranding event on the Cape the largest known mass stranding of bottlenose dolphins ever documented in the northeastern United States.
Reports came in with the low tide, around 5:30 Monday morning. About 30 dolphins were stranded between First Light Beach and Ellis Landing, in Brewster.
IFAW responders were able to re-float most of the animals, but they estimated five died before they arrived.
Early Tuesday morning saw about 20 dolphins stranded again – likely the same animals. But rescuers were able to successfully get them all back to deeper water.
IFAW reports seeing bottlenose dolphins closer to the Cape in recent years. Bottlenose dolphins are large, weighing 600-700 pounds, and generally considered an offshore species. So, while there have been larger strandings of other dolphin species, it’s more unusual for bottlenose dolphins.
Two of the dolphins were fitted with satellite tags, allowing the rescue team to monitor the pod's movements in real time. Tuesday evening, the dolphins were traveling together and away from the shallows of Wellfleet, toward Orleans and Brewster. By Wednesday the tagged dolphins were tracked in deeper water, about two miles northwest of Sandy Neck Beach, swimming with a pod of dolphins that hadn’t stranded.
According to IFAW, the Cape — and particularly the "hook" around Wellfleet and Eastham — is one of the world's most frequent hotspots for mass strandings. That’s due to its unique geography, and expansive tidal flats, with major tide fluctuations.
Dr. Sarah Sharp, who is the lead veterinarian at IFAW, said there were big tide fluctuations in play, with a 13-foot vertical change. She said that allows animals to get into places that they then can't get out of once the tide drops. She also noted an abundance of bait fish close to shore is another factor likely drawing them in.
Dr. Sharp specifically noted one thing that is not a factor in these strandings is offshore wind turbines. She said there are no turbines in Cape Cod Bay and she’s not aware of any science that would suggest turbines are a contributing factor to these stranding events. Dr. Sharp added that mass strandings have been happening on Cape Cod for thousands of years.
