By JANET McCONNAUGHEY/The Associated Press
NEW ORLEANS (AP) — Whatever is killing baby bottlenose dolphins in the area affected by the BP oil spill seems to be worst along the Mississippi and Alabama coasts.
Of 20 dolphins found dead along coastal Alabama, 16 — or 80 percent — were stillborn, premature or newborn calves. Babies made up 14 of 21 dolphins found dead in Mississippi, two of six found in the Florida Panhandle and only four of 30 found in Louisiana, where the coastal oil impact was greatest.
Although the oil spill is still being investigated as a possible cause of the deaths, that pattern might move it lower down the list, said Ruth Ewing, a veterinary pathologist with the National Oceanic and Atmospheric Administration in Miami.
“To me, it would still have to be considered, but would make it less likely,” she said.
But Randall Wells, head of the Sarasota Dolphin Research Program, said he couldn’t say whether it shows anything at all. Sick animals can swim long distances and winds and currents can wash them ashore a long way from where they died, he said.
“That leads to problems when trying to understand what they were exposed to, whether it be a disease, an environmental contaminant of some type or a biotoxin,” said Wells, whose program is a collaboration between the Chicago Zoological Society and Mote Marine Laboratory.
The difference between Louisiana and the other three states “is interesting, but it’s probably too early to make too much of that,” he said.
Ewing said naturally occurring biotoxins being investigated include domoic acid, which is known to cause “abortion storms” — large numbers of stillbirths and premature births — in sea lions. Produced by algae and plankton blooms, domoic acid doesn’t appear to affect shellfish or filter-feeding fish, but can damage the brains and nervous systems of marine mammals and people.
Bacteria on the list include leptospirosis, known to cause abortion storms in seals or sea lions as well as in farm animals, and brucella, which has been linked to at least one dolphin abortion, Ewing said. Another strain of brucella is known to cause abortion storms in herds of both domestic cattle and wild wildebeest, she said.
If bacteria caused the abortions, numbers also might vary from state to state depending on patterns of immunity, she said.
She didn’t consider the cold winter a likely cause, noting that extreme heat is more likely than cold to bring on stillbirths and premature births in land animals.
Another possibility is that the Alabama dolphins included more young mothers than the other groups — first pregnancies are the most likely to go wrong, she said. “If you’ve got a lot of young mothers, it’s possible you’re going to have a high rate of calf mortality associated with that.”
Nearly 70 dolphins that washed up in east Texas in March 2007 also included an unusually large number of calves, but the bodies were too decomposed for a cause to be determined.
And it may not be just one cause, Wells said. “Trying to identify a single cause may be looking in a wrong direction,” he said.
The causes may be natural, human-created or a combination, he said. “What you end up with is something that puts them over the threshold, and leads either to unusual mortalities or abortion storms.”
The number and variety of possible causes means many different samples must go out to many different laboratories, he said.
“A lot of people are trying to push a button and come up with what’s behind this. But that’s just not the way these investigations go,” he said.