Ghosts in the WoodsIt occurred to me recently, after spotting a white-feathered American robin scampering along a dirt road, normal-colored robins alongside him, that in all my years of observing wildlife and working with wild birds as a rehabilitator, I’ve never seen any albino animals. Ever. Except in photos.
The robin I saw was far enough away that I couldn’t tell if it was albino (completely white), or leucistic (part white with some normal coloration). What I could tell, though, was that this robin was part of a flock, foraging for food on the ground, flying up into the trees as I drew closer. The bird’s life seemed relatively normal, even while its coloration was anything but.
Albino and leucistic animals lack melanin, the primary pigment that determines the color of the skin, fur, eyes, and feathers. Without melanin in the body, skin and eyes appear a reddish-pink as blood vessels are visible, and fur and feathers are white. Leucistic animals, which have a partial absence of melanin, will have normal skin and eye coloration, and may or may not have fully-white feathers or fur.
Beyond coloration, melanin is instrumental in the development of certain parts of the eyes, including the irises, retinas, eye muscles, and optic nerves. As a result, albino animals sometimes have vision problems, which in the wild can spell disaster.
From one biologists’ perspective, it’s hard to say for sure what life in the wild is like for albinos and leucistics. “There’s just not a lot of research on this,” said Kurt Rinehart, a doctoral candidate at the University of Vermont, and co-author of the book Behavior of North American Mammals. “In order to understand survivability for any population, you need lots and lots of animals.”
Steve Faccio, biologist at the Vermont Center for Ecostudies, said that of all the reported sightings of albinos that come in, about 90 percent of those are actually leucistic. According to data from Cornell Laboratory of Ornithology’s Project Feeder Watch – in which participants record what they’re seeing at their feeders – fewer than 1,000 leucistic birds were seen among the 5.5 million birds reported between 2000 and 2006, giving an idea to how small the leucistic population is.
an albino moose
A quick Google image search, however, might have you thinking otherwise. Type in “albino and leucistic animals,” and thousands of photos of white penguins, deer, snakes, and hummingbirds pop up on the screen. In some photos, a white mammal will be alongside normal-colored offspring.
“It’s definitely a heritable trait,” Rinehart said of albinism, but the traits necessary to create albino and leucistic offspring are “very recessive; it requires a very particular combination of genetic material to manifest.” Offspring would have a greater likelihood of being albino if born of two albino parents, Rinehart said, but the chances of two albinos existing in one wild population (let alone mating with each other) are incredibly rare.
The question of whether an off-colored exterior effects mate selection probably differs from species to species. For many mammals, Rinehart explained, much of how they interact with their peers and choose their mates has to do with smell, so in some instances, color may be of little concern.
“I’ve seen moose trying to mate with statues or anything that even remotely appears like a quadruped, so I don’t think color would dissuade them in the rut,” Rinehart said.
Birds, on the other hand, do pay attention to color. In a study on barn swallows, researchers noticed that the flocking birds would “gang up” on a leucistic swallow, Faccio said. “There was a lot of interspecies aggression among leucistic birds.” As for finding a mate, “leucistic and albino males might not have as good a chance as attracting a mate. Color is important in male birds.”
Fish may feel the effects of color, too. Rinehart said that at hatcheries, where thousands of fish are captive and therefore easily monitored, there are relatively large numbers of albinos and leucistics. In a study on the reproduction of guppies, albino mothers had smaller offspring than non-albinos, Rinehart said. Larger offspring tend to have higher survival rates, suggesting that “albinism may be linked to another aspect of biology – low size – that leads to low survival.” Rinehart said he would not be surprised if albinism compromises survival in other ways, too, in other animals.
an albino coyote
Faccio said there is differing evidence on survival rates from predators. “Some studies have shown albino animals are left alone by predators because they’re not recognized as prey, while some show they are more easily found, captured, and killed.” (I’d venture to guess an albino mourning dove might be easier prey for a cooper’s hawk.)
The unlikely appearance of that white American robin has shed a dim light on a hazy situation. The truth is, when it comes to understanding albino and leucistic animals, the facts are not (yet) black and white.