As a kid, I knew these only as Mule Deer. Now they're referred to as Black-tailed (Mule) Deer, but that's not entirely helpful as there are two Pacific Coast sub-species of Mule Deer both called Blacktails. :S The ones in Northern California are the Columbia Black-tailed (Mule) Deer, Odocoileus hemionus columbianus. The others are also known as Sitka Deer. I don't know whether I would see the difference, but they're geographically separate.