Roans and Dalmatians
A Roan guinea pig is one with white hairs that are intermingled with any other colour. As such, the guinea pig does not appear to have 'solid' colouring. A guinea pig can be entirely roaned, or have a patch of roan colouring anywhere on their body. Regardless of the amount of roan colouring, that guinea pig should always be regarded as carrying the roan gene.
Dalmatian guinea pigs are similar to roans in that they also have white hairs intermingled with another colour. Dalmatians are usually black or chocolate. They have dalmatian spots which do not appear as a solid block of colour; the spots of black or chocolate are also intermingled with white hairs. Dalmatians can also appear to have roan colouring anywhere on their body. True Dalmatians aren't seen as often as Roan guinea pigs, but should still be regarded as carrying the Dalmatian gene.
It becomes confusing when someone is unsure as to whether their guinea pig is actually a Roan or Dalmatian, or whether they just have white colouring on their body. There is no sure-fire way to tell whether a guinea pig is actually Roan or Dalmatian; in theory any guinea pig with even one white hair could be a Roan! It is also worth remembering that a completely white guinea pig with a few coloured hairs could also be a Roan. The guinea pigs with these unobvious markings are usually referred to as 'Hidden Roans'.
Chester here is a Strawberry Roan Rex boar. You can see how the white hairs intermingle evenly with the coloured hairs on his face
Daphne is probably a 'Hidden Roan'. She appears completely white, but has a few cream hairs on the side of her face. Her eyes are also blue, a colour usually linked to Roan guinea pigs.
Roan and Dalmatian guinea pigs should not be regarded as unhealthy. On the contrary they are completely healthy and have no health problems that are linked to their breed. They can occur, it seems, out of anywhere, often to two parents that seem to have no Roan or Dalmatian colouring themselves. Each Roan and Dalmatian carry two genes; the 'normal' gene and the 'Dal' or the 'Roan' gene which is indominant. To illustrate how genes are passed down, I will refer to the Dal or Roan Gene as 'y', and the normal gene as 'X'.
Lethal guinea pigs occur out of parents that both carry either the Roan or the Dalmatian gene.
For a lethal guinea pig to be born, a Roan to Roan, Dalmatian to Roan or Dalmatian to Dalmatian mating will have happened. As each Roan or Dalmatian guinea pig carries two genes each (as explained in the section above), each guinea pig that is born from their mating will have a 1 in 4, or 25% chance, of being born a Lethal. The other babies have a 50% of CARRYING the Roan or Dalmatian gene, or a 25% of NOT having the Roan or Dalmatian gene at all.
Lethals - yy (25%)
Carriers - Xy (50%)
Others - XX (25%)
So as you can see from above, if you are fostering or have a pregnant sow come into your care who you suspect to be a Roan or Dalmatian, and they have been bred with another Roan or Dalmatian, you don't need to panic just yet. Each baby from this mating has a 75% chance of being born entirely healthy.
However it is unfortunate that we do see a lot of Lethal babies being born and most have them have occured due to accidental matings or unknowledgeable breeders. It is a huge mistake to make; the babies that are born as Lethals usually have numerous health problems that causes a great deal of suffering. Their health problems usually include:
The prognosis for Lethal guinea pigs varies greatly! Problems can range from mild to severe or even fatal. Some are born dead, and some die at a few days old. Sadly a lot of Lethals are born to people who have perhaps purchased a pregnant guinea pig from a pet shop, or to someone who doesn't know what to do with these poorly babies. Therefore they don't recieve the special attention that they require leading to death. It has been reported that some Lethals lead almost full lives, but obviously they require a great deal of attention, including regular dental work and religious hand feeding.
- Micropthalmia - This means, literally, small eyes. In Lethals the eyes can be smaller than usual, sealed shut or even non-existent. Obviously this means the guinea pig will be blind. It is worth saying that you can have guinea pigs with micropthalmia and blindness who are not Lethals.
- Dental problems - These range from very mild to very severe. Teeth can overgrow, grow lopsidedly and even fall out. This appears to be a huge cause of death in these pigs as it affects their eating.
- Physical deformities
- Lack of coat colour - Lethal guineapigs are always white.
- Other - it is said that lethal guinea pigs often have unseen deformities inside their bodies, most usually the GI tract which again affects eating and absorption of nutrients.
Whimsy, a healthy and happy Roan sow.