Wildlife

Oil Spill Aftermath: Dolphins Still Affected

Bottlenose dolphins swimming in waters affected by the Deepwater Horizon oil spill are dying earlier and birthing fewer calves than dolphins living in other areas, a new study shows.

Just 20 percent of pregnant dolphins in Barataria Bay — a part of the Gulf of Mexico that was most heavily tainted by oil from the spill — gave birth to surviving calves, much lower than the 83 percent success rate in other dolphin populations, the researchers found.

In addition, just 86.8 percent of the Barataria Bay dolphins survive every year. In comparison, this "annual survival rate" is 95.1 percent for dolphins near Charleston, South Carolina, and 96.2 percent for dolphins in Florida's Sarasota Bay, the researchers said.

"This dolphin population, as well as other dolphin and whale populations that were exposed to the DeepwaterHorizon oil, will take a long time to recover," saidstudy lead investigator Lori Schwacke, a wildlife epidemiologist with the National Oceanic and Atmospheric Administration.

The researchers followed the dolphins for nearly four years (47 months), and found that the dolphins in Barataria Bay had an approximately 60 percent lower pregnancy success rate compared with dolphins at a reference site, Schwacke said. What's more, 57 percent of the pregnant females that did not successfully have calves were sick with moderate to severe lung disease.

A female dolphin known as Y01 pushing a dead calf in waters affected by the Deepwater Horizon oil spill. This behavior is sometimes seen in females when their newborn calves do not survive.

Stranded whales euthanised

Several pilot whales which stranded on Stewart Island had to be put down to minimise their suffering. The pod, made up of 29 pilot whales, was found stranded at Doughboy Bay on Tuesday by a pair of trampers and it was another two days before they could raise the alarm via a water taxi due to the remote location.

Two Department of Conservation staff flew to the bay to assess the situation and found just eight of the whales still alive. Stewart Island ranger Phred Dobbins said the decision had to be made to euthanise them. "Refloating them was not an option given the length of time they had been stranded in hot, dry conditions," he said. “With the tide well out, we saw little hope of keeping the animals alive until enough rescuers could be flown in to assist."

The whales will be left to decompose naturally on the beach and visitors are advised to avoid the area and avoid swimming near them.