A rare male calico cat named Sherman is looking for a home in California.

Calico cats are not a breed of cat. Calico refers to a cat with large blocks of  black, white and orange on its fur. 

Sherman is especially rare because of his sex. Calico cats are almost always female because of their genetics, Vet Medicine explains. Fur color in cats is a sex-linked trait. 

"Since females have two X chromosomes, they are able to "display" two colors (orange and black, or variations thereof) and white; creating the 3-color calico mix. Since males have only one X chromosome, they can only be orange OR black," according to Vet Medicine. 

Sherman, who is only four-months-old, recently arrived at the Humane Society Silicon Valley (HSSV) as a transfer from a full sister shelter, reported Patch. 

The chances of a calico cat being a male is less than 0.1 percent, Dr. Andrea Berger, a veterinarian at HSSV, told Patch.

"It's like a unicorn! I've been involved with shelters for 20 years and I have never seen one," Berger told Patch.