The authorities in Colorado have warned residents to keep their children and small pets inside the house as a six-foot long Nile monitor lizard had escaped from a house in Colorado mountain community. 

A black lizard, known as Dino, somehow managed to break its nylon leash near Woodland Park, Monday, about 85 miles southwest of Denver and ran away, said Teller County Sheriff Mike Ensminger.

"These lizards are pretty muscular and can be aggressive," Ensminger told Reuters. "As cold-blooded creatures, monitors need to sun themselves to maintain body heat, so animal-control officers are searching rock outcroppings during the daytime hours.

The Denver Zoo which recently housed a Nile Monitor said that these African Nile monitors have long sharp claws, and powerful jaws that compress down their prey.

The zoo authorities said that these monitors feed on carrion, crocodile eggs, fish and birds, when they are out in the wild but in captivity they will eat small rodents and fish.

These Nile Monitors have a split tongue that they use to test the air for the smell of prey, and their thick and hard tail gives them the dragon-like look.

Denver veterinarian Kevin Fitzgerald, who is a specialist in reptile medicine, told Reuters about the problems that these reptiles have posed as an insidious species in Florida.

Fitzgerald explained that the monitor lizard will find some small mammals or birds to survive out in the wild of Colorado for a while, but the monitor will freeze to death once the temperatures in the mountains of Colorado drops in late summer or early autumn.

Also the reptile has to protect themselves from predators such as foxes, coyotes, mountain lions and even large raptors.

About the 'ethical and moral' issue of importing exotic animals for people to keep as pets, Fitzgerald asked, "why do we allow somebody to keep a subtropical, African species in a basement at 8,000 feet (2,400 meters)?".

But Sheriff Ensminger, said that it is not illegal to own a monitor in Colorado, so unless Dino harms someone, the authorities cannot lodge criminal charges against the owner.