The world's most poisonous deer, hands down, is Odocoileus toximortica, the North American spotted whitefoot. Native to forested or mountainous terrains, the whitefoot can be found in most regions of the US and Canada. It is thought to be the only carnivore of family Cervidae.
The bite of the whitefoot is a dual-tiered assault. Its venom carries two distinct toxins that begin affecting its prey immediately. One, a tetrodotoxin variant, causes gradual paralysis of the major muscle groups. The other bonds with white blood cells to produce a strong alkaline (pH of 13+) which dissolves internal organs from the inside out. In many cases, the whitefoot starts to feed while its victim is still alive.
Lithe and graceful, the whitefoot is perhaps the swiftest of the even-toed ungulates, able to silently outrun wolves, horses, even snowmobiles. It augments its keen low-light vision with a pair of infrared receptors on its snout, much like a pit viper. Survivors of whitefoot encounters have often remarked that the animal was able to anticipate their actions, and at times seemed to know where they were going before they made a move.
Such survivors are few and far between. Once it gives chase, the whitefoot rarely backs down, and has demonstrated an ability to remember specific prey (including humans) for years. Zoologists believe that the whitefoot holds grudges longer than any other animal, with the possible exception of Pelodytes pugilistis, the Iberian punching frog.