Color Genetics of Icelandic Sheep

 

One of my favorite things about Icelandic sheep is the huge variety of natural colors that they come in.

With so many different possibilities, the color genetics can seem complicated at first.  But once you understand the basics, it becomes very simple. 

 

· Colors: There are two basic colors, black and moorit (brown).

· Patterns:  Six different patterns alter the way the basic colors are displayed.

· Spots:  The possibility of spots add even more variety!

 

The Two Basic Colors:  Black and Moorit

 

Genetically, all Icelandic sheep are either black or moorit (brown).  Even if other patterns (such as the genes for white, gray, or spotting) alter or cover up the base color, it is still there and the sheep can pass it on to her offspring.

Identifying Moorit:

 

Moorit lambs look almost black when they are born, but quickly lighten up to their true color.  The three photos below show a moorit ewe lamb, immediately after birth, then at 17 days, then at 65 days.  See how much her color changed?

 

A good way to tell for sure whether your newborn lamb is black or moorit is to look at the skin around its eyes.  On a moorit lamb, that skin will be a rusty brownish color, while on a black lamb it will be pure black.

A black ewe and her fleece

A moorit ram and his fleece

Color Dominance:

Black is dominant over moorit, which means that if a sheep carries even one black gene, she will be black. 

 

A sheep that is homozygous black (carries two genes for black) can only have black-based lambs. 

A sheep that is heterozygous black (carries one black gene plus a hidden moorit gene) can pass either gene on to her offspring, meaning that it is possible for her to have either black or moorit-based lambs. 

 

A sheep must have two moorit genes (one from each parent) to be moorit.  This means if the sheep LOOKS moorit, you automatically know that she is homozygous for the moorit gene, and that is the only color gene she can pass to her lambs.

Pattern 2:  Gray

 

This pattern allows the sheep’s basic color to show through in her outer wool (tog), while the inner wool (thel) grows in white.  Depending on what her base color is, the sheep will be either black gray or moorit gray. When sheared, a gray sheep has a light-colored body with dark head and legs.

A black gray ewe and her fleece

A moorit gray ewe and her fleece.

The Six Patterns

 

There are six possible patterns that determine how the two basic colors express themselves on the sheep.  These patterns are:  white, gray, badgerface, mouflon, solid, and gray-mouflon.

 

Pattern 1:  White

 

Genetically, white is not a “color” in Icelandic sheep.  It’s a pattern that is overlaid on top of the sheep’s base color. 

 

Interestingly, sometimes the white pattern can have a “hole” in it that allows the sheep’s underlying color to show through.  This is useful for helping you figure out what color she carries under the white pattern.

 

Our white ewe Poppy, for instance, has a brown ear, which tells us that underneath her white pattern, her base color is moorit. 

 

This is different from the gene that causes spotting.

Pattern 3:  Badgerface

 

This pattern lightens the base color on the sheep’s body and causes a distinctive “badger-like” pattern on the face.  The chin, throat patch, inner ears, belly, legs, and under the tail remain dark.  Depending on what her base color is, the sheep will be either black badgerface or moorit badgerface.

 

The fleece of a badgerface sheep is an interesting mix of colors.  The outer wool (tog) is a pale, creamy off-white, but the inner wool (thel) is slightly darker, like a smoky, pale version of the base color.

A black badgerface ewe and her fleece.

Although the white spots on this spotted moorit badgerface ewe have almost entirely covered up her color and pattern, you can still tell she is a moorit badgerface because of the two-tone brown markings on her face.

Pattern 4:  Mouflon

 

Mouflon is the opposite of badgerface.  The sheep’s body remains dark, while the chin, throat patch, inner ears, belly, legs and under the tail are lightened.  Depending on what her base color is, the sheep will be either black mouflon or moorit mouflon.

A moorit mouflon ram and his fleece.

A black mouflon ewe and her fleece.

Pattern 5:  Solid

 

Solid essentially means “no pattern.”  The sheep displays its base color with no patterns to alter it.  The two sheep pictured under  the heading “The Two Basic Colors:  Black and Moorit” above demonstrate the solid pattern.

 

Pattern 6:  Gray Mouflon (single gene)

 

Because the Gray and Mouflon patterns are equally dominant (more about this below), a sheep may show both of them at the same time (2 separate pattern genes).  However, there is another pattern that expresses Gray Mouflon as a single gene.  Currently, this gene is very rare and found only in Iceland.

 

 

Pattern Dominance

 

White:  The pattern that produces white sheep is dominant over all other patterns.  If the sheep carries even one gene for white, the sheep will be white, no matter what other pattern she carries.  She can still pass that other pattern on to her lambs, though.  If the sheep is homozygous for white (carries two copies of the white pattern gene), all her lambs will be white, no matter who you breed her to.

 

Solid:  Solid is recessive to all other patterns.  If the sheep carries any other pattern, it will show up on top of the solid pattern.  A sheep must have two copies of the solid gene to appear solid.

 

Gray, Badger, & Mouflon:  These three patterns are co-dominant, meaning a sheep can express more than one of them at a time.  There can be gray-badgers, gray-mouflons, and badger-mouflons, each expressing characteristics of both patterns.  If you see a sheep that is expressing only ONE of these patterns, you automatically know the other pattern she carries is either a second copy of the first pattern (making her homozygous for that pattern) or else the recessive gene for the solid pattern.

A white lamb

A white lamb with heavy phaeomelanin

This ewe’s phaeomelanin has faded to its permanent adult shade.

A white ewe and her fleece

Identifying Gray:

 

The gray pattern is not obvious at birth.  Newborn lambs that carry the gray gene usually look like whatever other pattern they carry (solid, mouflon, or badger).

 

Often, the only way you can tell a gray lamb at birth is to look for “sugar lips” (a faint sprinkling of white near the lamb’s mouth.  Soon the white will begin show up around the eyes and in the under coat as well.

At first glance, this young lamb (left) looks solid moorit, but by the time she’s a week older (right), the white “sugar lips” are obvious even from a distance.  By the time she’s grown up, she will probably look like her mother, the moorit gray ewe pictured above.

 Because this lamb’s spotting pattern covered up the area where her “sugar lips” would have been, we didn't know for sure that she was gray until the sprinkling of white showed up around her eyes when she was a few weeks old.

“Frosted” Mouflon

 

There is a minor variation of the mouflon pattern, usually called the “frosted” mouflon, characterized by parts of the dark body fleece being “frosted” with paler brown and tan coloring.  This type of coloring is most frequently found in sheep descended from the AI ram Hnykill.

A plain black mouflon lamb (left) and his frosted black mouflon twin (right).

A plain moorit mouflon lamb (left) and his frosted moorit mouflon twin (right).

This gray-mouflon lamb displays both the pale undercoat of the gray pattern and the distinctive face markings of the mouflon pattern.

The double pattern on this badger-mouflon lamb has lightened both her upper and lower body, leaving her a beautiful, pale golden color all over.

A moorit badgerface ewe.

This gray-badger lamb looks very similar to a regular badgerface, but the presence of the gray pattern makes the undercoat of her fleece pale instead of smoky.

The Influence of Phaeomelanin

 

Most white lambs are born white and stay that color all their lives.  But some carry a minor gene that produces extra phaeomelanin, a pigment that gives them a distinctive tan color.  Phaeomelanin fades somewhat as the sheep grows up, leaving the fleece a beautiful “antique linen” shade. 

 

Other color/patterns can have phaeomelanin too, but it usually isn’t quite as noticeable as it is on a white sheep.

Spotting

 

Any color or pattern of Icelandic sheep can also come in a spotted variation.  The gene for spotting is a separate gene that overlays white markings on top of whatever other colors and patterns the sheep carries.

 

A sheep must carry two copies of the spotting gene to be spotted.  Sheep who carry only one copy of the gene don’t have spots, but they can still pass the gene on to their offspring to produce spotted lambs.

 

The extent and shape of the spots varies widely.  Some spotted sheep are mostly colored, with minimal white markings.  Some have big bold patches of white and color.  Others are almost entirely white, with just small amount of color remaining visible.

 

Even white sheep can be spotted, although you usually can’t see the spots against the sheep’s already white fleece.  In Iceland, some farmers breed for white sheep with extensive white spotting, because it is said to make the fleece extra white.

This sheep is spotted?  She sure is.  See the tiny little white mark on her left hind ankle?  It’s not much, but it still counts as a spot.

This gray-mouflon ewe is also minimally spotted, as evidenced by her white ankles and the white mark on her forehead.

This spotted black lamb exhibits one of the classic spotting patterns often seen in sheep with leadersheep bloodlines.

Depending on their shape, spotting patterns may look like white patches on a colored sheep, or colored patches on a white sheep.

On sheep with very extensive white markings, it can sometimes be tricky figuring out exactly what colors and patterns the sheep carries under the spots, because there is so little colored area left unspotted.

Even white sheep can be spotted—you just normally can’t see the spotting pattern against the white fleece.  But this white lamb has heavy phaeomelanin that makes her fleece be a rich tan color, allowing the spotting pattern of her white hind socks to show up vividly.

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