Sunday, May 25, 2008

Rescued river dolphin often face a tough return to the wilderness

An old dolphin named C6 fought off a shark attack, was successfully rehabilitated and released by human rescuers — only to choke on an exotic fish and die in the Indian River Lagoon.

A baby dolphin named Carter who wouldn't leave his dead mother also was cared for and then released, only to disappear into the lagoon without a trace.

The cases represent the successes of healing and releasing lagoon dolphins but also the harsh reality of the wild that can thwart the best of human intentions. The story of these two dolphins was chronicled by Harbor Branch Oceanographic Institute scientists and researchers in their latest paper, published in the journal Aquatic Mammals.

"Our skills and our methods to rehabilitate this dolphin (C6) ... were right on the money," said Steve McCulloch, a veteran dolphin researcher and marine mammal stranding program manager at Harbor Branch. "C6 and Carter have taught us a lot about how to do a better job next time."
Scientists say such research is the key to helping the species survive.

"What we're trying to do is understand these animals a little better," said Dr. Gregory Bossart, chief marine mammal veterinarian and head of pathology at Harbor Branch. "Our research is starting to establish some footholds."

At the same time, he said, "the take-home message here is releasing animals back into the wild is not as easy as we thought or as Hollywood portrays."

The article suggests although the expense of saving a dolphin can reach $100,000, "the contribution to conservation may be more indirect though public exposure, education and scientific research ... rather than as numerical additions to non-endangered populations."

The C6 story began in 1980, when the dolphin was first documented during a population survey of the lagoon mammals.

C6 was captured with another male dolphin, C7, and both were given brands with those numbers for future identification.

The males worked together in a "coalition" for years to find, protect and mate with the best female dolphins.

"This is Mother Nature's way of making sure the dolphin population retains stronger genetic codes," McCulloch said.

But on Aug. 30, 2000, a local resident called about a dolphin bleeding to death on a boat ramp at McWilliams Park in Vero Beach.

"He was melting down," McCulloch said.

C6 endured six months of rehabilitation, but there was a debate whether the geriatric dolphin would survive if released. Dolphins usually live about 25 years in the lagoon. C6 was 24.

"Aside from old age, he was in good shape," McCulloch said. "I mean he fought off four bull sharks."

During pre-release tests, C6 made clear it was ready to go home when it darted at McCulloch in the water and broke two of the researcher's ribs with its powerful snout. The dolphin broke another researcher's ribs shortly afterward.

C6 was released in the same area where it was rescued.

In three days, C6 swam 80 miles north and, somehow, found partner C7 once again.

"These dolphins, they have 100 million years of instinct. That's something I never discount," McCulloch said.

But then, 100 days after its release, C6 swallowed a fatal meal.

Known as a black chin tilapia, the fish that's invasive to the lagoon uses its spine to lodge itself in a predator's mouth. The tilapia dies but so does the predator. Researchers believe the fish sacrifices itself for the good of its own species by taking one more predator out of its environment.

The story of 1-year-old Carter was much shorter.

It was found Aug. 9, 2003, near the same park as C6, trying to suckle from his deceased mother.
Carter was nursed to health in three months and released back into the lagoon. Radio transmissions from its tag ceased seven days later.

"We still to this day are hoping we might find evidence," McCulloch said.

Whatever happened, dolphin releases are "not a cut-and-dry, black-and-white program," McCulloch said. "Each dolphin is distinctly different."

Quick "Facts about Dolphins"