Wanted: Two stealthy dogs with a penchant for biting joggers.

Plano Animal Services staff have been trying to catch them since August, when a jogger reported a bite. Officials suspect the dogs are responsible for eight bite cases, starting with one in May.

No one knows their gender or their names, but the father of a 12-year-old bite victim has dubbed them Bonnie and Clyde, after the famous outlaws.

"They're just running away from people," Dray Pavey told KTVT-TV (Channel 11).

According to Plano officials, one of the dogs is an Australian cattle dog whose instinct to nip at cows' heels is triggered by the sight of joggers.

"Nearly every bite involves a person running, with the dog approaching from behind, biting the back of their leg, and then running off when confronted," the city said in a detailed statement seeking the public's help in finding the dogs.

Plano staff said they have spent lots of time and money trying to catch the hounds. They sent out media alerts, warned neighbors and postal carriers, and placed traps in yards where the dogs had been seen. When that didn't work, they hired a trapper and bought special equipment. Still, nothing.

The city created a map to keep track of sightings, but even that hasn't helped. It shows the dogs roaming an area of 20 square miles — 10 times larger than the territories of urban coyotes, according to Plano officials.

Report Sightings of Evasive Dogs to 9-1-1. https://t.co/ppZirO3EUk pic.twitter.com/zkJoQkXfgF — City of Plano (@cityofplanotx) January 20, 2017

So how can it be this hard to catch two dogs?

For one, the city says, they're quick learners. The dogs caught on to the sound of the city's animal control trucks and flee as soon as they hear them, according to Plano officials. They also avoid fenced backyards and dead ends.

Here is the city's advice if you see the dogs:

Immediately call 911 to report all sightings.

Do not approach the dogs. Watch which way they go. If they are lying down, keep people away from them as much as possible.

Be aware of your surroundings, especially when jogging or walking. Typically, the dogs will approach from behind.

If Plano Animal Services staff is seen in the area, stay indoors and away from windows. Do not ask to help.

In short, don't mess with Bonnie and Clyde.

Pavey told Channel 11 that he just received a bill for his son's shots. The bite cost his family $3,800 after insurance, he said.