Male Tortoiseshell Cat Defies the Laws of Biology

Sep 1st 2009

A gender-bending kitten in England is grabbing headlines for its unusual markings -- and more notably, his sex. Eddie, a black and orange tortoiseshell kitten, was born male -- a "genetic impossibility," his owner, veterinarian Karen Horne, told the Daily Mail. Horne adopted the unusual male kitten after it arrived -- along with his three tortoiseshell sisters -- at her veterinary practice via a local cat rescue group.

The Daily Mail writes that the cat "overturns the normal laws of biology," and that's somewhat true. Tortoiseshell cats are nearly always female because two X chromosomes are required to produce the brindled black and orange coat coloring. Male cats have only one X and one Y chromosome, so it is "technically impossible" for them to inherit the tortoiseshell coloring, the Daily Mail writes. However, in extremely rare instances, a male kitten is born with tortoiseshell markings because it has an extra X chromosome (making it an "XXY"), according to VeterinaryPartner.com.

Just how rare is a male tortoiseshell cat? "Of eight million pet cats in Britain only a couple a year are born male tortoiseshells," reports the Daily Mail. At VeterinaryPartner.com, they estimate the odds at 1 in 3,000.

Eddie the kitten, named for the famed cross-dressing British comedian and actor Eddie Izzard, may be a "boy dressed in girls' clothing," his owner told the Daily Mail, but "so far, there are no signs of any gender confusion and he seems to be all there."