Getting Informed...About Grullas By Kris Enloe (1999, revised 2002)

This color has caused more controversy and raised more tempers than any other in the stock horse world.  Roan, gray, brown and dun horses are advertised as "grulla" all the time.  Some grullas are advertised as roan, gray, brown and dun.  Because it is such a rare color, it is easy to mistake a grulla for a different color, or a different color for grulla, especially if you have never seen one.  Then to add to the confusion, there are many different shades with twice as many shade names.  The following information comes from long-time associations, equine genetics researchers, and grulla breeders.  It should help clear up some of the misnomers and misrepresentations about the color.  The context should be taken in terms of stock horses, specifically quarter horses.  There are coat pattern genes such as overo, tobiano and appaloosa that will vary the appearance of the color further. Grulla?  Grullo?  Blue Dun?  Lilac Dun?  Silver Dun? Lobo Dun? Olive Dun?  Chocolate Dun? Black Buckskin? Slate? and on and on and on...Most of you have heard at least a few of these names when referring to grulla.  Here, straight from the major associations, are definitions of the color:

American Quarter Horse Association (AQHA) - Grullo.  Body color smoky or mouse-colored (not a mixture of black and white hairs, but each hair is mouse colored); mane and tail black; usually has a dorsal stripe and black on lower legs.    The AQHA pronounces it "grew-yo", and if you register a horse through the AQHA it will come back with a color of G-R-U-L-L-O.   However, the AQHA does not have a preference towards pronunciation when speaking, and "grew-ya" is also an acceptable form.  Grew-la is not.

American Buckskin Registry Association (ABRA) - Grulla pronounced "grew-ya".  Body coat slate colored (bluish gray as the blue heron) from light blue gray to a brownish shade.  Points and dun factor markings are black.  Dorsal stripe required.  The color Grulla is the rarest of all horse body coat colors.  The word Grulla is Spanish and translated into English is "crane".

International Buckskin Horse Association (IBHA) - Grulla pronounced "grew-ya".   Grulla is an intense color.  The body color is described as mouse, blue dove, or slate colored - with dark sepia to black points.  Grullas have no white hairs mixed in the body hairs.  The hide of a Grulla is comparable to that of a dun and is well pigmented to withstand heat and sunlight.  Grulla horses have the dorsal stripe and in most cases have shoulder stripes and leg barring.  Grulla is considered one of the most predominant species of the "dun factor".  Grulla should not be confused with roan or gray colors.    

Genetics behind the color
Quick genetics lesson -  Genes are located on strands of DNA.  Two alleles meet at a specific point (called a locus) to form a gene. A foal receives an allele for a gene from each parent.  The two combine and you have a  gene.    At this time, data on the horse has not been mapped for all genes.  Therefore, much of the data and analysis available is an educated guess based on progeny tests rather than actual allele/gene analysis.  The following genetic description comes from the University of California - Davis, a leader in equine genetic research.

Genetically speaking, most scientists would agree that a grulla is the same as a black horse - with one exception.  Grullas have at least one (heterozygous), and could have two (homozygous), dominant dun-factor allele(s) called the "D" gene.  This gene dilutes the coat color to a mousy gray and adds dun factor to the horse's body.  The D gene also changes a sorrel to red dun, a palomino to dunalino, and a bay or brown to dun.  The "D" gene in homozygous form does not intensify the dilution of the coat like the creme gene.  It has not been proven to intensify the amount of dun factor on the horse either.  A grulla may also be homozygous for black points. 

The genetic mapping of a grulla horse's color is believed by the University of California-Davis to be E?D?CCaarrgg where capital letters are dominant, small letters are recessive, and ? may be either dominant or recessive.   Dominant alleles mask recessive alleles, meaning recessive alleles will only be displayed when they are in the homozygous form.

What are these genes?

Just How Rare Are Grullas?

Extremely!  Until the break-off of Bay Roan as its own color, Grulla was easily the rarest color registered by AQHA.  The grulla color numbers are growing.  As of 2002, AQHA also evaluates each Grulla/Blue Roan case (meaning a horse that carries both genes), individually.  Some horses that were historically registered as Blue Roan in the past, are now registered as Grullos with roan characteristics in the markings area of the papers.  According to its color experts, AQHA prefers  a horse exhibiting both the dilution of dun or creme, and the roan gene to be registered as its base color with the additional roan markings comment.  This is done for tracking purposes.  However, it should be noted that many grulla enthusiasts consider this a detriment, because the roan gene is statistically passed on to 50% of the offspring, thus diminishing the purity of the grulla color.  You may want to consider this before making a grulla roan purchase. 

In 1996, .5% of all AQHA horses were registered grulla.  Several things have been speculated to have contributed to the percentage rise in registered grullas.  Specialized breeders of the color, a strong marketing plan by foundation quarter horse breeders, and more buckskin registries and shows are all believed to have increased awareness and popularity in the color.  Spikes in grulla numbers can also be attributed to stallion promotion and successful show stallions of the dun and black colors.  As the numbers of grullas registered through the AQHA increases at a higher percentage than other colors, it does draw speculation that grullas are starting to be bred more for color.  The effects of this practice may de devastating, and are often referred to as  "The Black and White Epidemic".  This problem ran rampant through the paint horse community in the 1980's and early 1990's.  Breeders that solely mate horses for the purpose of reproducing a specific color often disregard conformation, pedigree and disposition.

Data compliments of the AQHA, 2001, 2002 and 2003.

Color Variations in Grulla

Grullas come in many different shade varieties. Ways to avoid identifying a horse as grulla when it is not

Grullas come in many shades and can change drastically during the seasons.  Grullas are also the hardest coat color to catch on film and pictures can change the actual appearance of the horse.  If your attempting to purchase a grulla, or identify a horse as grulla, make sure you know what to look for in the grulla color.  A grulla should have a darker head then body (so do blue roans).  A grulla should have a uniform mousy color to its back and hip.  If the cape over the hip is multi-colored (black and white or black and brown), you may have a roan or a brown.  Duns can sometimes be distinguished by a brown or a red toned head that is darker then its body.  Gray horses almost always start to gray at the neckline or the top of the forehead and around the eyes.  A gray horse will have a gray head and as they age, their head may appear even lighter than the body.  It is possible for a gray horse to be born a grulla, but if it turns gray (one of the parents must have been gray for a horse to turn gray), it is recognized by the AQHA as a gray.  Roans will start to turn roan in a similar way that grays turn gray.  If possible, know the color of the parents.  Ask yourself, is it possible for them to have a grulla foal?  Gray and roan parents can be tricky because you may not be able to distinguish the base color of the horse.    What is always true:  One parent must have black points and one parent must have dun factor.   Almost any combination of parents  can produce a grulla if the above is true.  However, the closer the parents are to the grulla color, i.e. grulla, black, or dun, the more likely the horse is to be grulla.

Color Comparison Quick Reference

Common Phrases Heard Around the "Grulla World"
In order to reproduce the grulla color, you must have a grulla parent -
False.  A grulla can be produced by a variety of different colored parents.  The only requirements; at least one parent must have black points, and one parent must have dun factor.  Of course, odds of reproducing grulla are significantly increased if at least one parent is grulla.

All Grullas must have a dorsal stripe - True.  Although the description by the AQHA states a dorsal is not required, there are no known grullas that exist without one.    What about the "Creme" gene?  Well, the creme gene does not affect the black color, or if it does, it is only slightly to produce a "smoky black". 

All grays are a good way to produce grulla - False  Although gray may appear to look similar to the grulla in color, it does not necessarily produce the grulla color.  To know if a gray will be a good grulla producer, one must know the base color -  which can be anything from grulla to sorrel.  A gray with a grulla base color is more likely to produce a grulla foal.  However, statistically at least 50% of the gray horse's offspring will turn gray and should be registered as gray.

If a horse is born grulla it will stay grulla - Most likely.  There are some cases where a foal is born grulla and it will turn dun, black, blue roan or gray, but in general, if the foal's parents are not gray or roan, the foal will stay the grulla color.  There are rare instances when a foal will be born the same shade as a normal black foal and it will shed off the foal hair to become grulla.  These foals are always born with noticeable dun factor, especially a deep black dorsal stripe and they grow up to be extremely dark grullas.  There are also rare cases where foals are born a "questionable" dun color and will shed foal hair to a normal grulla color.

A grulla horse must have both a Dun-Factor (D) gene and a Creme (Ccr) gene - False, but highly debated.  A grulla may have both genes, but the genes are inherited separately.  Some researchers believe the existence of the creme gene will lighten the overall coat, but the University of California at Davis disagrees.  They plainly state "The creme gene will not affect the black body color".

Silver Horses are Double Dilutes -  Maybe.  What is a silver horse?  Everyone has a different definition.  The University of California at Davis believes the dun factor gene does not intensify in the homozygous form.  There are horses in existence that are known to be heterozygous dilutes that are clearly the same color as other homozygous dilutes.