There’s a new little bad boy in town!

AS the world’s smallest dog breed and weighing just four pounds or so, you wouldn’t think Chihuahuas were terribly scary — or would you?

Well, some dog experts reckon that following a wave of aggressive Chihuahua behaviour in the USA, these little guys are the most-dangerous canines around.

One professional dog trainer in the States reckons Chihuahuas have now got such a bad reputation that they are filling up the unwanted shelters, while other potentially-ferocious breeds are lapped up.

Perhaps several high-profile incidents involving these little pooches have led to this unexpected state of affairs.

In 2014, it was reported that packs of Chihuahuas were terrorising a neighbourhood in Arizona, running wildly through the streets and chasing kids.

Maryvale in Phoenix was the location, and the dog gangs comprised 10 to 15 at a time.

The little dogs not only made life miserable for youngsters who were just wanting to ride their bikes — they even pursued cars and adult pedestrians.

One problem is that many of the dogs had never been spayed or neutered, so they would be out and about, looking for potential mates.

Despite their small size, Chihuahuas do exhibit an aggressive nature at times, and often have no worries about going up against far larger dogs.

The previous year, a six-year-old girl ended up in hospital after a Chihuahua attack.

This was in Salem, Oregon, when five of the dogs ran over, leapt up and bit the little girl’s shoulder.

She and her father were walking to her school when it happened, and a school crossing guard helped chase the dogs away.

The animals were placed in quarantine, then later evaluated to see if they could be adopted or would have to be put down.

Locals said it had been bound to happen, as neighbours had already observed the Chihuahuas behaving badly.

Several more familiar scary breeds have been characterised this way over the years.

Rottweilers were once described as time bombs on legs, pit bulls were called a public health hazard, and the bloodhound was dubbed a “terrible beast” by the great Russian writer Fyodor Dostoevsky.

But none of them would have dreamed the cute Chihuahua might be next!

Another American expert got many dog owners to make contact and report dogs’ behaviour, choosing from over 30 of the most-popular breeds.

The Chihuahua was reported as by far the most aggressive, while pugs, collies and some spaniels were described as the most friendly, non-aggressive dogs of all.

Nobody is quite sure how or exactly when they began to change into the little terrors we see today.

One thing’s for sure, and that is that the Chihuahua was once upon a time far more obedient, calm and meek than it is now.

In the Aztecs’ time, they would sell the dogs as food and never have a minute’s trouble with them as they took them to market.

They also, believe it or not, used live Chihuahuas as hot water bottles when someone was ill and laid up in bed!

If you tried that today, the little darlings — ahem — would probably bite your ankles!