This post first appeared on August 26, 2012
I want to thank everyone for their patience. I have been called away to deal with family issues more than usual this year, and I apologize that I have once again gotten off-track. Barring any further complications, the current topic of color oddities will return tomorrow.
In the meantime, I wanted to share a link to a really interesting dog. Recently a puppy was discovered with the same pattern as a siamese cat. This coloring is a form of partial albinism and is caused by a mutation of tyrosinase, one of the enzymes involved in producing pigment. The mutation makes the enzyme temperature sensitive, so that the warmer parts of the body are pale while the cooler areas (like the extremities) are dark. For that reason, pretty much any mammal with this type of mutation is going to look much like the cats. In addition to cats, the pattern is also found in rabbits, mice, guinea pigs and rats like the ones pictured above. (The photo was taken by Diane Özdamar, whose wonderful gallery of rat photos can be found here.)
Up until this one was found, there was no evidence that dogs had a similar mutation. The puppy was said to have been found on the streets of Russia, but he disappeared before he could be tested. A photo of him can be found here. I wish I knew more, but that is all the information I have. Perhaps there are more like him somewhere in Russia. It would be a shame to lose the color now that it has occurred.