Every other Friday, the Outside/In team answers a listener question about the natural world. This week's question comes from Liz in Pittsburgh, Pennsylvania.
"Why do albino animals have red eyes?"
Producer Felix Poon went looking for the answers.
Transcript
This has been lightly edited for clarity.
Felix Poon: Albino animals tend to attract a lot of attention. In 2024, the Lakota held a special ceremony for the birth of an albino bison. There are lots of states that outlaw the hunting of albino deer. And when a white gorilla named Snowflake was born at the Barcelona Zoo, people visited in hordes. Part of the fascination is that there just aren’t a lot of albino animals out there.
Alex Funk: Albino animals in nature are rare, the same way that animals who are missing their front leg are rare. It has negative consequences for the survival of animals in the wild.
Felix Poon: This is Alex Funk. He’s a PhD student at Macquarie University in Sydney, Australia, where he studies cane toads, and more recently albino cane toads. Albinism is a genetic condition that reduces the amount of melanin in the skin, hair, and eyes. The condition can also occur in humans, but since we’re talking about evolutionary fitness in the wild, we’ll just stick with animals today.
For a long time, researchers assumed albino animals are rare because they can’t camouflage. After all, being seen in the wild often means being eaten. But Alex thought there might be more to it than that. So he designed a study where he created a bunch of albino toads using genetic modification. And when he measured their growth and survival rates, things looked pretty good. But when he raised those albino toads in the same cage as non-albino toads, or what he calls the “wild types.”
Alex Funk: The albinos barely grow, and the wild types grow like gangbusters.
Felix Poon: This was surprising, because these toads were raised in captivity without any predators around. So, what gives?
Felix Poon: It didn’t take long for Alex to figure it out. All he had to do was watch them eat their daily meal of termites. The wild type toads were able to catch the termites with their tongues most of the time. But, the albino toads?
Alex Funk: The albino toads would just be wildly striking, missing, falling over, and all sorts of comical stuff.
Felix Poon: It turns out, albino toads don’t have very good vision. We’ll get to why in just a minute. But first, this brings us back to our listener’s question: Why do albino animals have red eyes?
Alex Funk: That red is just the reflection of the blood vessels in your eye and the tissue in your eye.
Felix Poon: Of course, other animals’ eyes have blood vessels and tissue, but they also have melanin which gives them color. Without that melanin, those blood filled capillaries are plain as day. And unfortunately for Alex’s toads, that lack of melanin doesn’t just translate to red eyes. It also translates to bad eyesight. I won’t get into the science of why, other than to say that a lack of melanin in the eyes affects something called stereopsis. That’s the ability to see in three dimensions.
Alex Funk: So that's why you see, in my experiment, the toad's striking and missing constantly because they can't really see very well in 3D.
Felix Poon: And the problems for albino animals’ eye sight don’t just end there. Just like melanin protects the skin from UV radiation, it also protects the eyes. Without that protection, an albino individual’s vision can decline faster than non-albinos. All of this is why it can be tough to be an albino animal in the wild, and why humans sometimes get involved trying to protect them. Just ask the albino squirrels of Olney, Illinois, where they’re kind of the town’s unofficial mascot. They even have legal right of way on local streets and sidewalks.
If you’d like to submit a question to the Outside/In team, you can record it as a voice memo on your smartphone and send it to outsidein@nhpr.org. You can also leave a message on our hotline, 1-844-GO-OTTER.
