Vandals defaced a new Banksy graffiti piece stenciled on a Brooklyn wall, scrawling “we don’t need more rats!’ in blood-red capital letters near the artwork.

The head of the beaver had also been chipped off. The handwritten message near the piece was signed “Math.”

Banksy’s work was being guarded by four men in the wee hours Friday, but by daylight they were gone, the wrecked piece left unattended.

It’s the second Banksy piece to be defaced in a week after a vandal spray-painted over his artwork in Red Hook on Monday.

Bansky, a well-known British graffiti artist,  stenciled the piece on a wall in East New York as part of his month-long “residency” in New York, where he’s putting up his work on various public walls.

On Thursday, a couple of savvy Brooklyn street entrepreneurs have started charging $20 a pop to take pictures of the Bansky beaver.

The amateur curators used cardboard to shield the artwork, vowing to remove the covering only for a price.

“I’m trying to get some bread,” a man said in a video posted on YouTube Thursday. “This is my neighborhood. If you wanna take a picture, it’s gonna cost something.”

Later in the day, a man who called himself a Banksy “fan” stopped by with a hammer and chisel and attempted to remove the art from the wall, ­according to the Web site Animal New York.