Donkey Color
Part
III of a series on equine color genetics.
By Tracy
Williams
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| At
this point in our series on equine color genetics, we pause
from discussing the modifications to basic horse colors to encounter
briefly the less defined world of donkey color, which is not
well-documented. However, as donkey breeding gains ground, the
importance of understanding color genetics increases, and with
time the quality of our information should improve as well.
For now, we believe donkey color is similar to horse color,
and this hypothesis provides a beginning to unlocking the many
mysteries of donkey color.
Donkey
Colors
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Grey
dun, the most common donkey color, is characterized by a flat
bluish-grey body color, pale points and - usually - dorsal,
shoulder and leg striping. |
While
many of the terms you have learned in our previous two articles
still apply to donkeys, there is one important distinction.
For horses, the points refer to the mane, tail, lower legs and
ear rims. For donkeys, however, the points refer to the muzzle,
eye rings, belly and upper/inner legs while the trim refers
to the mane, tail and ear rims. In addition, donkey colors are
less varied than horse colors, but, like horses, some of the
shades tend to blur together making exact classification difficult.
Grey Dun
Grey dun is a wild donkey shade characterized by a
flat, bluish grey to beige color and is the most common donkey
color in most breeds and regions. Usually but not constantly,
the grey dun color is accompanied by variable striping: shoulder,
dorsal and leg stripes. More consistently, grey duns have pale
points, similar to mealy horses; dark points are recessive and
rare. Grey duns are dissimilar to both grey and dun horses.
They do not progressively whiten with age like grey horses do,
and they typically have less red in their coats than dun horses
and are less consistent with striping patterns.
Black
Black is another common donkey color and is usually accompanied
by light points, which do not disqualify them from being labeled
“black” as they would in a horse (possibly would
be termed brown instead of black). However, some black donkeys
maintain faint striping, and these are referred to as “smoky”
instead of black.
Bay
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Unlike
horses where bay is the most common base color, it is much more
occasional in donkeys. Bay in donkeys can be dark enough to
be almost black but is usually characterized by a reddish brown
body and black (or dark) trim, but they are typically less red
than a bay horse. A bay donkey with a red body, black trim but
light legs is called russet instead, and these donkeys confuse
our understanding of these genetic mechanisms.
Brown-black
Somewhere between bay and black is a shade referred to as brown-black.
These donkeys are nearly black, but they still retain red or
tan on the ears, face and back. |
Black
donkeys often have pale points, which would disqualify them
from being labeled truely black if they were horses.
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Chestnut/Sorrel
In donkeys, sorrel is a more commonly used term than chestnut,
and these animals are characterized by varying shades of red
on the body and pale points. Manes and tails can be anywhere
from dark red to almost flaxen, and the dark-maned sorrels maintain
light legs, which makes them difficult to distinguish from russets.
Sorrels often display dorsal, shoulder or leg striping.
Red
dun
Red dun donkeys have pale red bodies with striping but are difficult
to separate from sorrels that are also often red and striped.
The palest of this group are sometimes called rose duns.
Brown/chocolate
This is a rare shade, characterized by a chocolate brown body
color and a black mane and tail. It is probably related to
bay genetically.
Ivory
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Ivory
in donkeys is much like cream in horses except that it is
much rarer. These donkeys have cream bodies, blue eyes and
maintain faint striping.
The
interrelationships of donkey color are harder to classify
than in horses because it has not been as well-studied.
Currently they are grouped into axes of color, arranged
from dark to light in the patterns we think they fall in.
• Black to smoky to grey dun
• Black to brown to chocolate to brown dun to grey
dun
• Black to brown-black to bay to russet to sorrel
to rose dun
Ivory is isolated from these axes.
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Cream
donkeys mimic cream horses; they have pale bodies, usually
blue eyes and maintain a faint striping pattern. |
Patterns of White
Horses have more existing white patterns than donkeys, but
donkeys do display several colorful designs, some similar
and some unique from the horse. They also can have minor
face and leg markings though these are less common than
in horses and are sometimes confused with light points.
Roan
Although roan donkeys are often mistakenly called grey,
they lack characteristics of either grey or roan horses.
Grey horses typically whiten with age, while roan donkeys
advance only modestly to a white stage and typically stabilize
before they become all white. The roan pattern also affects
the donkey’s head and legs, whereas in horses, these
areas stay dark. Roan dilutes black to blue roan, sorrel
to strawberry roan and grey dun to roan. However, because
roan can lighten the legs it can be difficult to determine
the original background color. There are two subtypes of
roan in donkeys: frosted, which does become progressively
white with age, and frosty roan, which appears in white
hairs on the head and legs only.
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Spotted
In horses, multiple genes cause multiple types of spotted
patterns; however, donkeys are much simpler – all patterns
are referred to as spotted and seem to be variations on a
single design, a combination of two horse patterns. Like tobiano
horses, white can cross a donkey topline, and like the frame
patterned horses, it exists in horizontal patches. A unique
feature of donkeys is that they often have color spots within
white patches.
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Spotted
patterns in donkeys are often horizontal in character - much
like the frame pattern in horses
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White
White donkeys are extremely rare. They are characterized by
white hair, pink skin and dark eyes and are distinctly different
from ivory.
Genetic
Control
While the genetic control of donkey color has not been well-studied,
it is probably similar to genetic transmission in horses.
Dun
Locus
Grey dun, the most common donkey color, is a bit of a phenomenon
because it is a wild-type color; in most domesticated groups,
wild-type color is rare, not a dominant force in the species.
Grey dun color is caused by a single, dominant gene (Dn+)
and dilutes dark colors to light. A grey dun is actually a
diluted black background. If a donkey is recessive for the
Dun gene (Dnnd), dark colors are allowed to emerge.
Extension
Locus
The extension locus in donkeys is similar to that of horses.
A homozygous recessive genotype at the extension locus (Ee)
for either horses or donkeys eliminates black in the coat
resulting in a sorrel animal with light points.
Agouti
Locus
The existence of russet donkeys makes bay genetic control
difficult to classify. It is probably controlled by the Agouti
locus although differently than horses. The dominant gene
(AA) causes a true bay with red body and black trim, and the
recessive, wild-type gene (Aa) causes a black body with black
trim. Possibly there is an intermediate form at this locus
that causes brown-black donkeys. Genetic control at this locus
needs more study.
Albino
Locus
Because ivory donkeys are similar to cream horses, it is tempting
to assign them similar genetics. However, a horse who carries
just one of the dominant cream alleles reacts with a bay or
chestnut background to create a buckskin or a palomino. Donkeys
don’t seem to produce these shades of yellow. This could
be due to the rarity of sorrel and bay donkeys, or it could
mean that the cream gene is actually recessive in donkeys
instead of incompletely dominant as it is in horses.
Pangaré
Locus
The Pangaré locus controls whether or not donkeys have
dark or light points. The dominant, wild-type form of this
gene (Pa+) creates light points, and a donkey that is homozygous
recessive (Panp) at this locus will have dark points.
Spotted
Locus
Spotted patterns are caused by a single, dominant allele,
SpaS. It is likely that a homozygous dominant genotype at
this locus is lethal to donkey embryos.
While
donkeys clearly are capable of producing widely varied color,
shade and pattern, much like horses, the mechanics behind
their production is not well-understood. Hopefully, as donkeys
gain popularity in this country, more research will be dedicated
to unraveling the mysteries surrounding donkey coat color
classification and genetic control.
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Tracy
Williams is a gradusate of Colorado State University
with degrees in Equine Science and Journalism. She is
a freelance writer and photographer living in New Mexico.
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