Tail colour

What it does

Crossing two of them

Its gene carrot

Gene key

horsegenetics.tail_color

Priority

114 (magical band)

Alleles

Tlsld Tlstrp n

Combinations

6, all carryable — 4 outcomes

Outcomes

wild, solid, striped, solid-striped

Default allele

n

Wild frequency

Tlsld 2.0%, Tlstrp 1.5% per allele

Founder draws

1 × nextFloat()

Deterministic

no — the colour is per-copy

Shows on a foal

yes

Twin locus

Mane colour

Everything mechanical is on the mane page

The two genes share one implementation (HairColorGene), so the combination table, the per-copy colour, the epigeneticsForCopy trick that makes the heterozygote work, and the “paint toward, not with” rule are all documented once, on mane colour. This page is the differences.

It shows on a foal, and the mane does not

The foal mesh has a TAIL part and no MANE part (see body space). So a coloured tail is visible from birth and a coloured mane arrives with adulthood — which makes the tail the earlier of the two to read off a young horse, and makes a foal with a striped tail and no mane colour an entirely ordinary sight rather than a bug.

The tail is a different shape, and the painter knows

A mane is a long thin blade and a tail is a short fat one, and both are rotated out of the world axes by their rest pose. Rather than hard-coding an axis per gene, HairPattern works out the part’s own axes from its bounds and runs its bands across the longest one. That is why one painter serves both loci, and why it will serve a third if the family grows.

Why it is a separate locus

Folding mane and tail into one gene would make a horse with a red mane and a blue tail impossible to breed. It also halves what the family is worth: two loci with two independent per-copy colours each is four colours across one horse, before anything else it carries is considered, and that combinatorial room is the whole reason these genes were designed as a set.

It is the same rule the white-pattern loci follow from the other direction: only alleles at the same locus compete for a slot. Mane and tail plainly do not.