As a new pet owner, you may be amazed at the variety of rat colors available to choose from. But did you know that these colors follow specific genetic guidelines? The laboratory rat, or Rattus Norvegicus, was the first mammal used for laboratory research, resulting in extensive genetic studies regarding the inheritance of many traits, including coat color. Let’s discuss the basics of rat color genetics and explore some of the possible colors and patterns you may encounter in your furry companion.
Understanding Rat Color Genetics
Rat colors generally follow Mendelian genetics, meaning that genes have varying degrees of dominance or recessiveness. By using a Punnett Square, which is a visual representation of Mendelian genetics, you could predict the color of your rat’s coat by determining which traits are dominant and which are recessive. However, rat color also has other factors that determine the shade, such as the location of the gene on the chromosome, as well as modifying genes called polygenes. These factors give rats their incredible array of colors and patterns.
The Role of Tameness in Rat Color
Interestingly, a rat’s color can also be influenced by its degree of tameness. In an experiment involving selective breeding for tameness, researchers found that over time, piebald rats with irregular patches of two colors became more common in the population. The study also found that rats with more white in their coats were determined to be more tame. Solid-colored rats, on the other hand, became much rarer.
Exploring Rat Colors and Patterns
Here are some of the variations of rat colors and patterns that you may come across:
White rats come in two types: pink-eyed albino and black-eyed white. While the albino mutation was the first mutation of rats, it is now common due to the breeding of millions of laboratory rats specifically selected for albinism. Pink-eyed whites may have weaker eyesight and an impaired sense of smell and motor skills compared to pigmented rats, but they do have a similar lifespan.
The hooded rat is a descendant of the brown rat and has become more interestingly patterned through breeding. The most common pattern is the black and white hooded rat, but they can also be found in blue, chocolate, champagne, orange, and red agouti.
Siamese rats have darker faces, ears, feet, and tails, which emerge in colder areas through a process called acromelanism. The Siamese gene is recessive, which means breeding two Siamese rats results in an all-Siamese litter. Breeding a Siamese rat to an albino rat, however, results in Himalayan rats.
Agouti rats are wild rats that have been selectively bred for a brighter coat color. They have three distinct color bands of black, brown, and grey on each individual hair, and their ideal coloring is a rich chestnut with dark grey at the base mixed with black. Their belly color is silver.
A distinguishing feature of Dumbo rats are their larger and circular ears, which sit lower on their heads than non-Dumbo rats. The Dumbo gene is recessive but can be combined with any type of coat color or texture.
Russian Blue Rats
The Russian Blue Rat is a newer color of rat that appeared in the 1990s and has a distinctive slate blue color similar to blue mice and cats. The color of each hair is unevenly dispersed along the shaft, with the tips being darker than the base.
Berkshire rats have two colors, a top color and a white belly. The top color can be any color from black to grey, brown, or fawn, but a strong delineation between the top color and the white belly is required. A black Berkshire rat will also have white feet and tail.
Rats Make Awesome Pets
It doesn’t matter what color rat you get – rats make awesome pets. They are loyal, friendly, playful, charming, clean, and smart. As a new pet owner, with all of the amazing varieties of rat colors available, you’re sure to find one that strikes your fancy. Do you have a pet rat or a preferred color for a pet rat? Let us know in the comments!
Jacob, H. (1999). Functional Genomics and Rat Models. Cold Spring Harbor Laboratory Press
Coat Color, Temperament, and Domestication
Wade, N. (2006). “Nice Rats, Nasty Rats: Maybe It’s All In The Genes.”
American Fancy Rat and Mouse Association
Kuramoto, T., Nakanishi, S., Ochiai, M., et al. (2012). “Origins of Albino and Hooded Rats: Implications from Molecular Genetic Analysis across Modern Laboratory Rat Strains.”