A Beaver in New York City?

A beaver? In New York City? Is that all there is to it?

Yes, except for two bits of biological trivia:

First, the beaver is the official mammal of New York state. It appears on the seal of New York City, as a symbol of industriousness.

Second, no beavers have been confirmed in the city limits since the early 1800s. The advance of human civilization presumably drove them away, out into the country where they faced less pollution and fewer fur trappers.

But a beaver's "lodge" -- a shelter made from twigs and mud -- has been spotted on the shore of the Bronx River, a once-fetid stream that runs through the city's northernmost borough.

And now, biologists from the Bronx Zoo have taken pictures of the male, 2- to 3-year-old beaver that presumably built it.

Signs of Life

"There were a couple of reported sightings last summer, but everyone thought it was a muskrat," said Eric Sanderson, an ecologist at the Wildlife Conservation Society, which runs the zoo. The beaver lodge is on a section of the river that runs through the zoo grounds.

"And then, over the winter, some of the staff were walking around getting some exercise, and saw gnawed trees, and wondered, 'What's that?'"

He laughed. "We don't do surveys for beavers because we had no idea they come here."

To nature lovers, the find is testimony to the hardiness of a species that, by rights, ought to be in retreat. Perhaps the larger message, they say, is that cities -- even big, crowded ones like New York -- can get better.

The neighborhoods along the Bronx River do not exactly remind one of Yellowstone. The Bronx is crowded, mostly paved over, and includes some of the city's poorest neighborhoods.

The river runs parallel to a heavily used parkway. Until a few years ago, much of it was a dumping ground for garbage and used tires. Oil from leaky cars washed into the river whenever it rained. Chain-link fences run along its shores.

$15 Million Cleanup

Rep. Jose Serrano, a New York Democrat, got $15 million in federal money to clean up the river. The project was not expected to make it swimmable, but it apparently now is -- if you're a beaver.

Where did the beaver come from? It was not available for interviews -- beavers are generally nocturnal creatures that prefer to stay away from people.

But biologists speculate that it could have come from Westchester County, to the north, which includes upscale, landscaped suburbs, and turns relatively rural as one travels farther from the city.

Lest you think of beavers as cute, cuddly little animals, they're classified as rodents. But even so, a beaver, less than 10 miles from Times Square?

"It is surprising, even for us -- and our business is wildlife conservation," Sanderson said. "We're not sure where its source population is, but it's nowhere nearby. It made quite quite a journey to get here."

"And I think one sort of take-home point is that nature often does things that are surprising to us, if we give it half a chance to come back."