“…non-agouti hair is of a solid color which is black in the absence of dilution from other genes. This is one of the very first mutations from agouti, the fur lacking the yellow/red banding in the individual hairs.”
The a Locus
Agouti, the natural coloring in rats and most furred mammals, is the dominant base color trait in the wild. It is a multi-colored fur with banding in each individual hair of brown, black and tan, a dark gray base and black guard hairs with shades of grey on the belly often giving a nice silver appearance. Pet lines often tend to be brighter then their wild counterparts.
On the other end of the A locus, the non-agouti hair is of a solid color which is black in the absence of dilution from other genes. This is one of the very first mutations from agouti, the fur lacking the yellow/red banding in the individual hairs. Black is recessive to Agouti, how ever it is dominant to all other colors.
Origins
The exact origins of the recessive black mutation are unknown, but it is most certainly one of the first mutations and has occurred in both lab and wild rats long before the fancy alongside albino rats. That is to say this is a naturally occurring mutation in the wild, unlike most mutations that we work with today in pet rats which were mostly discovered by breeders in the last 20 years. Experiments as early as 1885 recorded by H. Crampe included the albino, non-agouti, and piebald mutations.
In 1901, the first ever show for fancy rats saw a Black Even Marked owned by Mary Douglas win and were the first standard added. Oddly enough it wasn’t until 1902 that an Agouti was entered and standardized.
The black mutation actually has some more interesting effects then just it’s color though. A difference in the Agouti protein inhibits MSH binding which not only results in the production of red-yellow pigments but also effects the behaviors of the animal. Do to this black rats tend to be calmer and more easily handled. It is not surprising then to find out that around 80% of laboratory rat strains are homozygous for non-agouti.
Cross-Genetics
As the base color locus all rats are either Agouti or Non-Agouti(Black), therefor this gene plays a big role in all colors.
STANDARDS
AFRMA [US] –
“AGOUTI – The color to be a rich chestnut with dark slate at the base of the hair. Coat is evenly ticked with black guard hairs. Belly color will be silver gray. Eye color is black.
BLACK – Color is a good solid black throughout, showing no rustiness or white hairs. Eye color is black.”
RMCA [US] –
“AGOUTI – The color is a rich chestnut with dark slate at the base of the hair; coat is evenly ticked with black guard hairs; belly color is silver gray with black eyes.
BLACK – Deep lustrous black, devoid of rustiness or white hairs with black eyes.”
NFRS [UK] –
“AGOUTI – To be a rich ruddy brown, evenly ticked with black guard hairs. Base fur dark grey to black. Belly fur to be silver grey. Foot colour to match top. Eyes black.
BLACK – To be a deep solid black, devoid of dinginess and white hairs or patches. Base fur to be black. Foot colour to match top. Eyes black.”
Howie is a Black Berkshire.
Howie, 1y4m
A Black Irish doe from some of our first litters.
BBR Sablinova x Skyler Doe [Black Irish]
Kehypoints
- Agouti coloring is the naturally occurring wild type.
- Black is most likely one of the first mutations of rats, predating the fancy and occurring naturally in the wild.
- The first fancy rat show in 1901 was won by a black marked rat.
- Black rats are generically more docile by nature, how ever well breed rats of either genotype can have great temperaments.
A Final Thought
Agouti and black rats are the oldest colors, and are the base for all the different color variations we have today in the rat fancy.
Bibliography