Pictures: Rare White Giraffe and Other Unusually Pale Animals

Albino and leucistic animals abound in the animal kingdom, from squirrels to crayfish.

Omo, the rare white calf recently spotted in Tanzania’s Tarangire National Park, is one special snowflake.

But unusually white animals in other species—from eagles to bears to crayfish—are often seen in nature. There are three ways this can occur: albinism, leucism, and isabellinism.

True albinos are unable to produce any kind of pigment, hence their white coloration and pink eyes: Blood vessels normally masked by eye color show through. (See "Pictures: Special Albinos and Unusually White Animals.")

Albinism is a recessive trait, meaning both parents must pass the mutation on to their offspring. Snowflake, an albino lowland gorilla, had parents that passed on copies of a gene found in other albino animals like mice, horses, and chickens.

Leucistic animals are mostly white but can produce some pigment. For example, many still sport color in their eyes. Two white spider monkeys recently spotted in a Colombian rain forest likely have this condition.

A third condition is called isabellinism, in which a genetic mutation leaches the color out of pigmented penguin feathers. Animals that have isabellinism are different from albino animals because they can still produce pigment.

Leucistic and isabelline are sometimes used interchangeably to describe the pale brown or "blonde" coloration of penguins with this condition.

Keep clicking to see our roundup of albinos and other white animals.

—Christine Dell'Amore