In the 400 years since New York City's birth, the local wildlife has adapted to a life of fast food, pollution and isolation.

At a top secret location in Manhattan, within a large public park, is a tiny patch of moist hillside. Flecked with shade from a grove of young maple, oak, and black cherry trees, the area is bordered by a busy road and sits just across the street from a school. And yet, stalking the slope's meadows of moss and wildflowers, lounging among decaying logs and fallen leaves, is a population of New York City's most obscure inhabitants.

This is predator territory, and here lives a killer so rare and little-known, only a handful of New York City's eight million or so residents have ever seen one. "They will eat anything they can stuff into their mouths. They'll eat each other," says Ellen Pehek, a retired ecologist who spent 21 years working for the NYC Parks & Recreation's Natural Resources Group. With strong, crushing jaws and thick legs, these hunters have a muscular, almost-reptilian physique that evokes Komodo dragons. "If they were six feet (1.8m) long, we'd be running from them," she says.

The hunters in question are northern dusky salamanders, and they easily fit into the palm of a hand. Though they are rarely seen or thought of – even by park officials, according to Pehek – they are thought to have been living in this very spot for the best part of a century.

As New York City has grown up around them, the little amphibians have continued to eke out a living on an area of land significantly smaller than the footprint of any of the iconic skyscrapers now found just a short distance away. "I would say it [the hill] is maybe 75 yards [68m] across, and maybe 40 yards [37m] high," says Erik Baard, a journalist and author who runs the Nature Calendar, a blog about species that live in and around cities.

New York City is famous for its worldly, subway-riding pigeons and epicurean rats – such as Pizza Rat, who went viral for hauling a large slice of margherita pizza down a flight of stairs on the subway. But there are less familiar urbanites to be found too, ones which were in residence long before Western civilisation showed up. Coyotes routinely visit Central Park, where precious orchids bloom in the ground. Comb jellies pulse through the East River under Manhattan Bridge. And each spring, from Brooklyn to Queens, the prehistoric, tank-like horseshoe crabs haul themselves up onto beaches to mate and lay their eggs.

Though some of these organisms are continuing life as normal, it would be impossible to remain unaffected by the approximately one million structures that have popped up over the last 400 years, or the bustle of a cultural and economic metropolis. In fact, New York City's native wildlife is evolving, and fast. Some species have already diverged so much, they have unique physical and genetic characteristics.

In 1945, Carl Gans was out for a walk in Manhattan. While ambling down a hill – Pehek likes to think he was on his way to visit a local university – the young German-American herpetologist stumbled upon a population of northern dusky salamanders. Desmognathus fuscus is a species that needs ultra-pure water, shade, and personal space – particularly from humans. But there they were, in a public park, in a major city. And they were thriving.

Soon Gans had published his discovery in a scientific paper. He noted the exact location where the salamanders had been found – with the street, and details of their habitat – and called for them to be protected. But nothing happened. Eventually the sightings dried up, and after a while, most scientists believed that they had vanished from the area forever.

Then came Pehek. It was 2005 and she couldn’t help wondering, was it just possible that the salamanders might have managed to cling on, despite over half a century of further development? "I assumed not," she says, "but I grabbed a couple of people and we went out there."

The salamanders' favourite New York City haunt is what's known as a "seepage" – a miniature wetland that exists on a shallow slope, which is kept continuously moist by groundwater that flows over its surface. The dusky salamanders' Manhattan hill has its own little stream bordered by rocks, and the surface is coated with a thin layer of fallen leaves and mud.

"It was so fragile that if you stepped on it, you would slide down the slope," says Pehek. She doesn't remember finding the first northern dusky salamander of the day, because there were so many. "It was so exciting… we just kept finding them over and over," she says. The team even found a mother and her young, who had just hatched out of a little cluster of white eggs.

At one point, the dusky salamander was the most common variety in New York City. But now they are extremely rare, and Pehek has found just a handful of solitary populations. Pehek likes keep their locations a secret, to avoid any accidental trampling by curious members of the public.

By thoroughly scouring suitable sites, eventually she identified another group in the Manhattan park, around a mile (1.6km) from the first area – but separated by two bridges........

© BBC