You're down here for 13 hours straight - he brings a bit of home to it

Jeff Mullenbach, police officer

Since 11 September he has been on site helping the rescue workers to deal with the psychological and emotional trauma of the work.

In the presence of their furry friend, hundreds of labourers have been able to talk about the extraordinary stress of working at the site and the pressure it puts on their lives, in a way they often find hard with other humans.

Winning trust

One man who works in the morgue talked to Nikie for nearly an hour after a day when the remains of many of the victims had been found.

"People are nice, but dogs are different," explained Pat Sullivan, a fire-fighter from Staten Island.

Nikie gets a massage at the end of each day

Nikie is joined by his handler Frank Shane, who founded the non-profit group K-9 Disaster Relief.

"There's a special spot, I believe, in everyone that an animal transports you back to a child," said Mr Shane.

"In a disaster setting where your whole world has turned upside down and your trust wiped out, here comes an animal that psychologically transports you back to a period where you felt safe," he explained.

Special training

Following the attacks, several pet therapy organisations stationed dogs at the city's family assistance centres to comfort victims' relatives.

But few animals have the training and personality necessary to endure long hours in the cold and constant noise of Ground Zero.

The World Trade Center site is now almost cleared

Now aged seven, Nikie went through special training as a puppy to teach him the skills necessary for being a therapy dog - such as letting people approach him rather than sniffing or barking at strangers.

Police Officer Jeff Mullenbach said many of the workers have their own dogs, but rarely get to see them because of the long hours they spend at the site.

"You're down here for 13 hours straight - he brings a bit of home to it," Mr Mullenbach said.

Disturbed sleep

And Nikie works long hours too - 12 hours a day, five days a week.

According to Mr Shane, Nikie absorbs much of the worker's stress and pain. In the first few months he would howl in his sleep at night after a long day.

"He not only absorbed the stress, he had to release it," Mr Shane said.

But when he and his handler arrive home each night Nikie is given a massage to help him relax.

And Mr Shane takes him for regular check-ups at the vet and watches for signs that Nikie is getting too stressed.