Dolphins in New Jersey?

A group of bottlenose dolphins has been confounding humans since it took up residence in two rivers near the Jersey shore six months ago. Now that it’s winter, some people are worried the dolphins will never make it out.

Three dolphins have died out of the original group of about 15 that spent the summer and fall in the Shrewsbury and Navesink rivers north of Asbury Park.

Federal wildlife experts say the remaining dolphins are healthy, and should be able to make it through the winter if they stay. They cite the cases of dolphins that successfully spent winters in Massachusetts, Virginia and even northern Scotland.

But some worry the dolphins will meet the same fate as four that drowned in the Shrewsbury River in 1993 when ice closed in on them.

“It would seem to me that the natural habitat for dolphins in the winter when it gets cold is much farther south in warmer waters,” said U.S. Rep. Frank Pallone Jr. (D-N.J.). “Isn’t it stressful for them to be in this colder environment? Since they are mammals, what happens if the ice freezes over and they can’t breathe?”

The National Oceanic and Atmospheric Administration, which has jurisdiction over the dolphins, doesn’t plan to intervene unless they appear to be in imminent danger.

“This is a normal sort of way of life for these critters,” said David Gouveia, marine mammal program coordinator for the agency’s fisheries service. “We’re optimistic that things are going to work out just fine.”

Others are not as confident.

“We have seen the disastrous consequences when dolphins remain in the area during the winter months,” said state Sen. Sean Kean. “Now it’s up to NOAA to determine a course of action to try to get the dolphins back to the ocean before it’s too late.”

Looming over this debate is the history of dolphins that have wound up in the Shrewsbury. In at least two instances, dolphins lingered too long in the river and died when rescue attempts went awry.

Still, dolphins can handle cold weather, said Randall Wells, dolphin research program manager for the Chicago Zoological Society.

“There are examples of the Navy using dolphins in very cold situations with ice around, and a naturally occurring population of dolphins off the coast of northern Scotland, where ice reaches into the water and snow is in the mountains nearby, and these animals get by fine,” he said. “Blubber is a pretty amazing substance in these animals; it’s able to maintain body temperatures quite well.”

Teri Rowles, lead veterinarian for the Fisheries Service and leader of the National Marine Mammal Health and Stranding Response Program, predicted the Shrewsbury dolphins will be able to keep part of the river unfrozen by their constant surfacing to breathe.

She said there is no reason for a risky intervention like netting the dolphins or trying to coax or scare them out, especially while they are acting normally and appear to be healthy.

“We are letting these dolphins be wild dolphins,” Rowles said.