Some thoughts on 'designer ferrets'by Dr June McNicholas Recently I was asked what I thought about 'designer ferrets'. I have to say my first response was that I was a bit bemused why colour should be such an issue, and that my main concern would be for the welfare of the generations of kits bred in attempt to produce a particular desired appearance. However, the question prompted me to think about some of the factors governing coat colour in ferrets.
Leaving the more thorny problem of applied genetics aside for the moment, it seems that a lot of other information about coat variation is still uncertain. Why, for example, can the same animal change appearance and markings, not only seasonally, but frequently from one year to the next? I have many who, at three or four years old, bear no resemblance to the way they looked as kits or as younger adults. Perhaps ferrets, like their wild mustelid relatives, are more influenced by environmental factors than the majority of mammals. Temperature, feeding, breeding condition or hormonal changes through ageing or neutering all seem to affect secretions from skin glands that in turn affect coat colour and texture. Silvering of the coat seems to be associated with both ageing and reduced hormonal activity. Given the apparent absence of research into the relative influences of these factors, the question arises of whether the 'designer' kit would retain its desired colouration through to maturity? Would an owner still want it if it didn't?
As far as genetics are concerned, unlike mink, about which there is quite an extensive literature on colour genetics for obvious reasons, ferrets have not been the focus of research into colour breeding, so there is little published information to be drawn on. Incidentally, there is far less research on mammalian coat colour than you might think. The definitive source is 'Comparative genetics of coat colour in mammals' by A.G. Searle, published in 1968, although 'Colour inheritance in small livestock' (1978) by Roy Robinson is useful. As with other mammals, coat colour in ferrets is dependent on the genetic information passed from both parents to their offspring. Animals may have the same phenotype (physical appearance) but different genotype (genetic information) so the gene pairings may not produce the anticipated outcomes if only parental colour is taken into account. Genes may be dominant or recessive, the recessive genes remaining dormant unless the mating involves the pairing of two recessive genes. Dark coats appear to be influenced by pairings of dominant genes whereas albinism is the pairing of certain recessive genes. However, animals may carry recessive genes which may be passed on in subsequent matings. Thus polecat to polecat matings may produce a percentage of albinos if both parents carry the recessive gene for albinism. At this level it is really a question of knowing the breeding history and parentage of the animals selected for breeding.
However, there are other, perhaps even more important, factors. Intensity of coat colour and definition of markings are influenced by polygenes, groups of modifying genes which control the extent and colour markings such as masks, or the distribution of white markings on feet or throat. Other polygenes 'dilute' colours, such as in sandies with polecat markings. Many of the desired colours (siamese, himalayan, mitted or silvers) depend on the manipulation of polygene groupings as much as the genes for the main coat colour. By now, the genetic equations are becoming quite complex if you go in for the maths of it all! Add to all that the possibility of wanting to breed for eye colour as well as coat colour. Another set of genes to play with and incorporate into the equation! Nose pigmentation adds even more complexity. The percentage of kits in a litter to carry the desired colours and markings may be quite small so line breeding of closely related animals is usually adopted to reinforce the influence of shared genes. However, this reinforces all shared genetic influence, the good and the bad, sometimes with unfortunate results. For example, breeders of fancy rats have recently experienced difficulties when breeding for a lilac coat colour. Whilst the main coat colour could be obtained with very selective line breeding, inherited skin problems, increased infertility and temperament problems were found to be prevalent in some strains.
Colour breeding in many mammals is something of a minefield. In ferrets, it still seems like uncharted waters. However, if there has been sufficient research arising out of breeding programmes that can provide information about gene loci, the number which may be responsible for coat colour, nose pigmentation etc, the actions of recessive, dominant and incomplete dominance in genetic pairings, and the effects of polygenetic groupings for the control and distribution of coat markings and colour intensity, then it strikes me that the breeders of 'designer ferrets' should come forward and publish the evidence to support their claims. Such data would certainly be welcomed by scientific journals such as Applied Animal Behaviour amongst others.
I have no doubt that it will be possible to breed 'designer ferrets' once more is understood about ferret genetics and the interactions with seasonal and other factors which can influence coat colour. However, I'm less sure of whether the knowledge currently exists today, and I'm even more unsure of the desirability given the generations of kits that will be bred in the process. I've no objection to limited programmes of selective breeding for temperament, health and conformation, but should colour really be the main focus of a breeding programme?
(First published July, 1997)