Elizabeth Paul

INTRODUCTION:
Colour is one of the most important advantages that alpacas have over other fleece bearing animals. When I first bought into alpacas, nearly seven years ago, I fell in love with a beautiful grey female and was determined to try and breed more greys. I found no-one was able to help me do this, as the patterns of colour inheritance in alpacas seemed to be one big mystery. As a biologist with some knowledge of genetics, I felt I had the necessary background to investigate this further. What began as a simple personal goal has evolved into a seminar, titled “The Alpaca Colour Key” which I have presented regularly to Australian alpaca breeders since November 2002. I have combined models of inheritance, together with pigment studies and pedigree data, to try to form a more complete view of colour inheritance in alpacas.

PIGMENTATION:
Coat colour in mammals is almost entirely dependent on the presence or absence of melanin pigment granules in the hair and skin. There are two types of melanin, eumelanin (black/brown) and phaeomelanin, which is yellow. Melanin is concentrated in the skin epidermis, at the base of hair follicles, and in the retina of the eye. Colour in these areas is determined by the size and shape, as well as the type, number and distribution of granules. Melanin is based on the amino acid tyrosine. Mammalian pigment granules consist of melanin, attached to a protein.

The most important role of pigment is protection of the animal from UV light, but different patterns of pigment across the animal also provides disguise protection from predators or prey, warning patterns, or sexual maturity status. Pigment also plays a role in other systems including hearing.

USES OF COLOUR:
Unlike birds or even reptiles, mammals are rather restricted in their use and expression of colour. Most mammals come in drab browns and greys, with the occasional black and white combination. Many young animals have different colour patterns to the adults of their species. Very often they are spotted, striped or both. Sometimes this is for protection or concealment from predators, but it may also communicate the juvenile state to adults, causing them to modify their social responses. Adult male animals may have more intense colouration or bolder patterns than females and juveniles. This is partly for protection of the females and young, but it also advertises the male as fully mature, desirable to females and a threat to other males. Often such patterns may still be dull to our eyes, but the animals are programmed to notice subtle differences.

Colour in different patterns can also form a warning system within a group. Rabbits and many deer have a bright white under tail, which they flick to warn other members of their group of danger. Black and white skunks need no introduction; they fluff out their stripes and tail to make themselves look bigger and less of an easy target to predators. Generally, the larger the animal, the less need it has for protective colour patterns, although giraffes are perhaps the standout exception (in more ways than one!)

VARIATIONS:
In the wild, the pattern and colour of a particular species may be very constant, or it may be quite variable. Sometimes the variability has little consequence to the animal’s survival; and sometimes it may be lethal. At a glance, all zebras look the same, but each individual zebra has a pattern of stripes as unique to itself as a fingerprint. Foals and their mothers know each other’s stripe patterns, the same as a human child knows its own mother’s face in a crowd. A zebra born without stripes, if ever there was one, would very likely be abandoned by its mother, since it has no stripes to initiate her recognition response. The striping on zebras, while it does not conceal them on the open plains, confuses an approaching predator with a dazzle of shifting lines. An all white or all black zebra would easily stand out in such a situation.

All white predators are also at a disadvantage, unless they happen to be polar bears in the Arctic wilderness. White tigers are relatively common in zoos and theme parks, but they are almost non-existent in the wild. They all trace back to one white male, which was taken from the wild in the 1950’s and bred to yellow females. Eventually some of his mates produced several white cubs. There is also at least one group of very pale or white lions. As lions are social cats, they have been able to survive as a group, where one on its own might not.

Animals that vary too much from the norm may also be unable to attract a mate because of the sexual requirements of that species. Leopards however, have a melanistic form, which is no bar to either hunting or to mating (probably because leopards are most active at night). Black leopards are at no particular survival disadvantage, compared to spotted ones.

Whatever the wild situation, in a domestic environment such as a farm, animals with unusual patterns or colours are more likely to be saved and nurtured, than discarded. Foxes and mink produce a range of colours when farmed, which are never seen in the wild. The usual colour for wolves is greyish, but domestic dogs come in many colours. Here also, colour is no bar to mating.

BASIC MELANIN PRODUCTION:
Melanin is manufactured by special cells in the body called melanocytes, which arise from the neural crest area of the embryo. Cells derived from the dorsal or top part of the embryo, are the ones that will ultimately develop into melanocytes. These migrate to their destinations through the epidermis during the embryonic stages of development. Any delay in this migration may affect the final colour pattern. Pigmentation is generally more intense around the head, along the back of the neck and the top of the back, than the belly region of an animal. Mature melanocytes insert pigment granules into the base of the hair shaft as it grows out of the follicle.

CHANGES IN PIGMENTATION:
Melanin production involves a number of other biochemical agents, and any alteration to the sequence, or to the components will have an effect on the final product, and therefore the colour. For example, albinism is the result of the animal’s genetic inability to form tyrosinase, the enzyme required to convert tyrosine in the first step of pigment production. This is a homozygous recessive condition. The albino animal will never develop pigment, but can be shown to have melanocytes present in the skin. Other genes cause a switch between the production of eumelanin and phaeomelanin; still others cause a grouping or clumping effect of the granules themselves to produce a diluted final effect.

The level of activity of the melanocytes can also be altered, as in the change from dark summer coat to light winter coat of the snowshoe hare and Arctic fox. This change is initiated by the changing day length between summer and winter. Cold temperature can also have an effect on pigmentation. The Himalayan rabbit has a white coat, but the extremities are black, due to the lower temperature in those areas. If a Himalayan rabbits’ fur is shaved off and an icepack applied to the shaved area, the hair that grows back will be black. Ageing causes a permanent reduction in melanocyte activity in the hair follicles.

Drawn from “The Alpaca Colour Key” by Elizabeth Paul November 2002.