On a Sunday evening in late April, Ellen Pehek pushed apart a thicket of tall reeds at the edge of a murky Staten Island pond, searching for one of New York City’s rarest animals.

The pond, in a marshy area along an access road near a cluster of Amazon and IKEA warehouses, didn’t look like anything special. But Dr. Pehek, a retired city parks department ecologist, felt confident that the Atlantic Coast leopard frog was nearby.

“That’s where I’ve seen them before,” she said. “We found roadkill on the road right near there, and I know we caught tadpoles in the pond in the past.”

Few people would associate this desolate section of the borough’s West Shore with rare amphibians. But Staten Island is one of just three counties in New York where the Atlantic Coast leopard frog, a species identified less than 15 years ago, is known to live. This spring, the state’s Department of Environmental Conservation added the frog to its endangered species list — the first addition of a New York City resident since 1999. The designation, coming as the federal Environmental Protection Agency was seeking to weaken habitat protections nationwide, galvanized efforts to protect the frog’s habitat from further encroachment.

As the sun retreated behind the Goethals Bridge, Dr. Pehek crouched in her thigh-high rubberized muck boots and orange insulated jacket, listening.