There are many different varieties of pet rat, each with characteristic features. They all descend from Rattus norvegicus, the Brown Rat. Selective breeding has been used to emphasise some of their features and minimise others.

Varieties of pet rat include the double rex rat, the dumbo rat, hairless rat, odd eyed rat and satin rats. There is also the tailless rat. There are standards for the appearance of these varieties described by the American Fancy Rat And Mouse Association.

Standard rat. This variety has short glossy hair which is short.
Tailless rat. These have no tail at all.
Rex rat. This type has curly hair and whiskers.
Hairless rat. Unsurprisingly these have no hair.
Dumbo rat. This variety has particularly big ears which are situated on the sides of the head, rather than the top.
Satin rat. Satins have a longer, thinner coat which has a sheen.
Bristle coat rat. Bristle coats have a coarse and stiff coat, like a brush.

These are the seven varieties which are recognised. Each of these seven are split into 6 sections according to markings and colour. There are many different colours and markings described within these groups which are standardised. Breeders may create other colours which are not in the standard list.

Wild rats

Wild rats are either of the variety Rattus rattus or Rattus norvegicus. These are known commonly as the black rat and the brown rat respectively. These are larger than mice and have broader faces and coarser features. Brown rats are more common in the UK but pockets of black rats still exist.