Rescuers from the New England Aquarium and the Cape Cod Stranding Network responded to two separate dolphin stranding incidents involving a total of seven animals on July 17 and 18, 2006. Both strandings occurred on First Encounter Beach in Eastham, MA, on the bay side of Cape Cod. All of the animals involved were Atlantic white-sided dolphins, and all were successfully transported to Herring Cove Beach in Provincetown, where they were released.
A pod of approximately 20 white-sided dolphins was initially sighted in the waters off Wellfleet on July 16, and again on the morning of the 17. In the late morning of July 17, two animals from the group stranded on First Encounter Beach in Eastham. One of the dolphins was male, and the other female. Both appeared to be adults with no obvious signs of injury or illness.
The Cape Cod Stranding Network was the first responder to the incident, with veterinarians and biologists from the New England Aquarium's Rescue and Rehabilitation Department following close behind. Veterinarians from the Aquarium performed advanced blood tests on the dolphins to make sure that they were healthy enough for transport. The dolphins were then carried by hand on special stretchers to waiting animal ambulances and animal transport vehicles and driven north to Herring Cove Beach where they were released at approximately 4:30 p.m. The steep gradation of Herring Cove Beach makes it an ideal release point, as animals are quickly able to return to deep water .
At about 11:00 a.m. on July 18, five additional Atlantic white-sided dolphins stranded on First Encounter Beach in Eastham. Three of the animals were adults and two were juveniles. According to New England Aquarium Stranding Program Coordinator Connie Merigo, it is impossible to tell for certain whether the two incidents involved dolphins from the same group. "Really, we have no way of identifying individual animals in the water, so it's very difficult to determine if the animals we're seeing from one day to the next are the same group. White-sided dolphin pods can be quite large and fluid, as well," said Merigo.
Once again, the Cape Cod Stranding Network responded, followed by veterinarians and biologists from the New England Aquarium. The animals were transported on stretchers to waiting animal ambulances and animal transport vehicles and taken to Herring Cove Beach, where they were successfully released at about 4:00 p.m.
Three dolphins—one animal from the first stranding and two from the second—were fitted with satellite tags before being released. Satellite tags are wallet-sized computers with GPS capabilities that track the dolphins' location and transmit data by satellite to Aquarium computers when the dolphins surface for air. Some tags, including one of the two used on July 18, also transmit data including water temperature and the depth and duration of dives.
Support from town officials in Eastham, Wellfleet, Truro, Provincetown and the National Park Service was instrumental in ensuring the timely transport and release in both incidents.
Dolphins can strand for many reasons, and experts are not always able to identify a single cause for a stranding. Contributing factors can include poor weather, illness, parasites or injury. But many strandings appear to be simply accidental. Dolphins are open ocean creatures, and may be caught unawares by the coastal tide, which can drop water levels by as much as 10 feet in Cape Cod. Shallow, silty conditions in shoreline areas compound the problem by reducing the effectiveness of the animals' echolocation. "When this happens, the animals begin to stress out and panic, just like people lost in the woods," explains New England Aquarium spokesperson Tony LaCasse. "The dolphins are literally left behind by the tide."
It is likely that there are other contributing factors in strandings that humans do not yet understand.
Track updated : 7/20/06
No signal from 54736 today. Number 5, a male, is supposed to broadcast today. I still have hope. there is an inset in this map that shows an enlargement of the area just east of Sandy Neck and Barnstable Harbour. Please note the times. There is a hint that they might have found each other, BUT it is only a hint. Future days will tell more of the story.
Track updated : 7/21/06
We have heard from 54736 again. It appears to have hooked up with 49783 which is the same animal that he was released with. 54736 is a male; 49783 is a female. The animal released on Monday the 17th (49786) is off to Stellwagen Bank.
54736 and 49783 are very close to shore in the evening - just something to be aware of.
In the future we'll program the tags a bit different to get more daytime signals.
Track updated : 7/25/06
After an exciting and stressful weekend, all of the animals are out of Cape Cod Bay, at least as of 0700 GMT this morning. With any luck they'll stay out there.
Track updated : 7/26/06
The three dolphins continue to stay out to sea. 49786 is way out by the North Channel of Georges Bank. Number 5 and Number 3, 54736 and 49783 respectively, seemed to have turned back southward towards Cape Cod Bay. They, this morning, were ~13 km west of Provincetown, MA. With any luck they'll stay out there.
Track updated : 7/27/06
Thankfully 49783 and 54736 have moved out into the basin between Stellwagen Bank and the mainland. 49786 is still out by the northern channel of Georges Bank hopefully there is good fishing out there. I'll be decoding the dive data from 54736 this week so we can get some insight into his diving abilities since he was released.
Track updated : 7/28/06
I have decoded some of the dive data from 54736. This is one of the animals that was released on the 18th of July in a group of five. The data covered from the 18th till the 27th. All of the dive activity up to the 22nd took place between 0 and 10 meters. After the 22nd the dives started getting progressively deeper and using more of the water column down to ~ 150m on the 27th. As far as dive durations are concerned, most of the dives are in the 420 second (6-7 minute) range. The longest dive lasting just over 20 minutes. The temperatures he is spending time in range from 12 - 21 deg C with most of the time spent between 15 - 18 deg C.
Track updated : 7/29/06
More movement today by 49783 and 54736. They have moved to the eastern side of Stellwagen Bank while 49786 has moved to the distant western edge of German Bank off Nova Scotia. Very shortly, the maps (updates) will come out every other day, instead of every day. This is due to the tags broadcasting every other day for 14 days.
Track updated : 8/21/06
We are getting some remarkable tracks from these animals. They are using practically the entire Gulf of Maine with a tendency of travel around German and Browns Bank area. 49783 still is tending to stay in the less deep areas like Stellwagen, Jeffreys and Cashes Ledge.
We are quite pleased at the outcome so far ... 36 days for 49786, 35 days for 49783 and 54736.