Dolphin stranding puzzle

After having never seen a common dolphin stranded on Virginia shores, Susan Barco has now seen seven of the animals euthanized in a three-day period after finding their way into too-shallow water.

Three common dolphins were spotted struggling on the beach near Back Bay Wildlife Refuge on Sunday, and four were seen in the mud flats of a bay-side Eastern Shore creek on Wednesday.

Despite the efforts of the Virginia Aquarium Stranding Response Team, all seven had to be put down, said Barco, senior scientist and stranding coordinator for the Virginia Aquarium and Marine Science Center.

About three weeks ago, three more common dolphins made their way all the way up the Nansemond River into downtown Suffolk, Barco said.

The appearance of common dolphins that far inland, and in the Chesapeake Bay, marks a rare occurrence. These are not the bottlenose dolphins often spotted just offshore in Virginia Beach and up the rivers and creeks around Hampton Roads.

n fact, Barco said she knows of no other reported mass strandings of common dolphins in Virginia. The species typically swims closer to the continental shelf, which starts about three miles offshore, and beyond, Barco said.

Including the stranding of two pygmy whales late last year, the two incidents this week mark an odd run of strandings in Virginia.

“I’d say it’s normal to have a mass stranding once every three years,” Barco said. “Now we’ve had two in three days and three in the last few months.”

Answers about why the strandings happened are hard to come by, Barco said. There are often as many hypotheses about why dolphins and whales get beached as there are strandings, she said.

She and a network of scientists are performing necropsies on some of the dolphins, analyzing their blood, organs and brains to look for any hint of sickness or pathology.

The differences they’ve found so far point to the difficulty in pinning down a reason for the strandings.

All of the dolphins stranded on Sunday had full stomachs, while none of the dolphins found on Tuesday had any food in them. All of the dolphins on Sunday were mature females, but only one from Tuesday was a mature female. The others were young and one was still nursing.

Jim Brantley, environmental public affairs office with the Navy’s U.S. Fleet Forces Command in Norfolk, said Navy sonar could not be at fault.

He said no sonar activity had taken place in the seven days prior to the strandings, and before that the first activity had been more than 200 nautical miles away.

Barco said stranded dolphins can be rescued if they are found and attended to soon enough. But the longer they are out of the water, the more damage their organs suffer and the harder recovery they face if they make it back in the water.

In these two cases, the response team had to euthanize all of the dolphins because they had suffered too much, Barco said.

She said people near the water should keep their eyes open.

“We want people to keep their eyes out for unusual aggregations of animals in unusual spots,” she said. “We hope we’ve seen the last of it, but history tells us to be vigilant.”

The Virginia Aquarium Stranding Response team is a group of mostly volunteers who rush to the scene of distressed dolphins, whales, turtles and seals.

If you see a stranded animal, you can call the team’s 24-hour hot line, 757-437-6159.