There are two types of alpaca - huacaya (with crimpy sheep-like “wool”) and suri (with silky dreadlocks). Suri are much rarer than huacaya, estimated to make up between 6 and 10% of the alpaca population. The suri is probably rarer because it is less hardy in the harsh South American mountain climates. The style of its fleece offers less insulation against the cold - the suri fleece parts along the spine, exposing the animal to the cold unlike the huacaya fleece which provides excellent cover over the backbone.
Most suri in Peru are white in colour. This is because many years ago the Peruvians decided to breed for a white commercial fleece market, so the other colours died out or were culled. The quality of the white suri fleece was improved by selective breeding, and when the Peruvian government allowed Peru to export alpacas most exported animals were therefore white.
Estimates vary, but it is reckoned that coloured suri make up only around 6% of the world suri population. Coloured suri are therefore quite rare.
A few years ago it was discovered that just one gene controls the fleece type, and that the suri gene is dominant over the huacaya gene. If the animal carries the suri gene it will therefore present itself as a suri, even if it is also carrying a recessive huacaya gene. These are known as heterozygous suris, in other words, they are heterozygous for the suri gene.
If a suri alpaca has inherited a copy of the suri gene from both parents it will be homozygous for the suri gene. If an alpaca is homozygous for the suri gene all its progeny will be suri, regardless of whether the other parent is suri or huacaya.
To learn more about homozygosity and heterozygosity, click here.