Colorless Creatures

With its pale skin and light eyes, this IGUANA (above) stands out. Usually, iguanas are greenish brown. Those colors help the reptiles blend into the tropical forests in which they live.

So, why is this one white? It’s albino. Albinism is an inherited condition in which the body can’t properly produce colored chemical compounds called pigments. As a result, this albino iguana has white scales and yellow eyes.

Iguanas are not the only animals with albinism. People have spotted everything from lobsters to lemurs with skin, hair, fur, feathers, and scales that are mostly colorless. Without their typical coloration, these animals don’t usually fare well in the wild.

There’s something different about this iguana. The animals are usually greenish brown. Those colors help them blend into the forest. But this one’s pale skin and light eyes stand out. Why is this iguana white? It’s albino. Albinism is a condition where the body doesn’t produce colored chemical compounds called pigments.

As a result, this albino iguana has white scales and yellow eyes. Iguanas are not the only animals with albinism. People have spotted everything from lobsters to lemurs with albinism. Their skin, hair, fur, feathers, or scales are mostly colorless.

Albinism has been documented in at least 300 animal species in North America and in a wide range of species around the globe. But it tends to be rare—only one out of many thousands of individuals might have it. Albinism occurs in humans as well. About 1 in 20,000 people in the U.S. have albinism, though certain populations have higher or lower rates.

Part of the reason for albinism’s rarity has to do with the genetics of this trait. Units of hereditary material, called genes, control the production of pigments. Pigment genes have different versions, called alleles. People and most animals inherit one allele from each parent. Alleles associated with albinism are recessive, which means that an organism will show the trait only if it inherits two albinism alleles.

Many people—about 1 in 70—and many animals carry one allele for albinism and one for typical pigmentation. Because albinism is recessive, these individuals produce the pigments that lead to colorful skin and hair. But they are carriers of the trait, and two typical-looking carriers can have offspring with albinism.

Albinism has been observed in at least 300 animal species in North America. It also occurs in many species around the world. But within those species, it tends to be rare. Only one out of many thousands of individuals might have it. Albinism occurs in humans as well. About 1 in 20,000 people in the U.S. have albinism.

Albinism is an inherited condition. The way it’s inherited is part of what makes it so rare. Units of hereditary material, called genes, control the body’s production of pigments. There are many different versions of pigment genes. People and most animals inherit one copy from each parent.

Genes associated with albinism are recessive. That means that someone will have albinism only if they inherit those genes from both parents. About 1 in 70 people carry one gene for albinism and one for typical pigmentation. Because albinism is recessive, these people still have colorful skin and hair. But their children can potentially have albinism. Albinism in animals is inherited the same way.

Some evidence suggests that animals born with albinism don’t fare well in the wild. One reason is that a stark white animal stands out in its natural habitat, unlike one whose coloration blends into its environment. That makes it easy for predators to spot and catch an albino animal. Some studies, for example, have found that owls are more likely to spot and target albino mice than brown ones.

The sun is another potential danger for albino animals. The pigment melanin—which creates tan, brown, or black coloration in many animals—can be important for protection from the sun’s damaging ultraviolet (UV) rays. In people, exposure to the sun signals the body to pump up production of this pigment. That causes skin to tan, which provides some defense against burns. Animals and people with albinism, though, don’t produce this pigment. That makes them especially susceptible to sunburns and possibly deadly skin cancers.

Albino reptiles face special difficulties because they’re cold-blooded and rely on external heat to regulate their body temperatures. They often bask in the sun to warm themselves up. Albino reptiles can’t keep warm the typical way without the risk of sunburn. They tend to do better in captivity, where caretakers can provide artificial heat sources like heated stones to keep them warm.

Animals born with albinism don’t always survive in the wild. One reason is that a stark white animal stands out in many habitats. That makes it easy for predators to spot and catch it. For example, scientists have found that owls are more likely to hunt albino mice than brown ones.

The sun is another potential danger. The pigment melanin creates tan, brown, or black coloration in many animals. This can be important for protection from the sun’s rays. In people, exposure to bright sunlight signals the body to make more of this pigment. That causes skin to tan, providing some protection from burns. But animals and people with albinism don’t produce this pigment. That makes them especially vulnerable to sunburns.

Albino iguanas and other reptiles face special challenges. Reptiles are cold-blooded. That means their bodies don’t produce their own heat like ours do. They often bask in the sun to warm themselves up. But albino reptiles can’t keep warm the typical way without getting sunburned. They tend to do better in captivity. Caretakers can keep them warm in other ways, like by giving them heated stones.

Just because an animal’s coloring is pale doesn’t mean it has inherited albinism. “There are many naturally white animals, such as polar bears, that aren’t albinos,” says Murray Brilliant, a geneticist at the Marshfield Clinic Research Institute in Wisconsin. One big clue that an animal isn’t albino is dark-colored eyes. True albino animals don’t produce dark eye pigments.

An ongoing study of squirrels across the U.S. is showing how the occurrence of white fur compares with that of true albinism. The survey found that about 80 percent of the white squirrels studied have dark eyes. Only about 20 percent have the telltale red or pink eyes that show they’re truly albino.

“That pink color comes from blood vessels in the back of the eye,” says Brilliant. The same is true for albino rabbits and mice. Other species with albinism, including people and orangutans, don’t have pink eyes—although camera flashes can sometimes make it look that way in photos. Since humans and other primates have more types of eye pigments than other animals, those with albinism tend to have eyes that appear very light blue.

Eye pigments and the molecules involved in making pigments are important for healthy eye development. Without them, animals with albinism can have serious vision problems, which can make spotting prey or predators difficult.

People with albinism often have vision problems too. In his research, Brilliant has identified alleles associated with albinism in people. “Now we’re working on understanding how the genes function and developing therapies to enhance vision in people with albinism,” he says.

Just because an animal’s coloring is pale doesn’t mean it has albinism. “There are many naturally white animals, such as polar bears, that aren’t albino,” says Murray Brilliant. He’s a geneticist at the Marshfield Clinic Research Institute in Wisconsin. One way to tell the difference is to look at an animal’s eyes, he says. True albino animals don’t produce the pigments that make eyes brown, deep blue, or green. Instead, their eyes are red, pink, yellow, or pale blue.

In the U.S., scientists were curious how many squirrels with white fur were actually albino. They started collecting data on the color of their eyes. They’ve found that about 80 percent of white squirrels have dark eyes. Only about 20 percent have the red or pink eyes that show they’re truly albino.

“That pink color comes from blood vessels in the back of the eye,” explains Brilliant. The same is true for albino rabbits and mice. But humans and other primates with albinism don’t have pink eyes. Instead, their eyes tend to appear very light blue.

Eye pigments are important for healthy eye development. Without them, animals with albinism can have serious vision problems. That can make it difficult to spot prey or predators.

People with albinism often have vision problems too. In his research, Brilliant has identified genes associated with albinism in people. “Now we’re working on understanding how the genes function,” he says. “We’re developing therapies to enhance vision in people with albinism.”

ALBINO PEACOCK:
1 in 1,800

ALBINO PEACOCK:
1 in 1,800

ALBINO GRAY SQUIRREL:
1 in 100,000

ALBINO GRAY SQUIRREL:
1 in 100,000

ALBINO GALAPAGOS TORTOISE:
1 in 100,000

ALBINO GALAPAGOS TORTOISE:
1 in 100,000

WHITE GIRAFFE:
1 in 22,000

WHITE GIRAFFE:
1 in 22,000

ALBINO DEER:
1 in 30,000

ALBINO DEER:
1 in 30,000

ALBINO KANGAROO:
1 in 50,000

ALBINO KANGAROO:
1 in 50,000