Today’s Wonder of the Day was inspired by Andy. Andy Wonders, “Why is the pink dolphin pink?” Thanks for WONDERing with us, Andy!

Is there anything more majestic than a dolphin? They’re one of the smartest animals on Earth, with beauty and grace to match their intellect. It’s a great thrill to watch dolphins leap from the ocean into the air. They’re easy to spot, with long beaks, round heads, and bright pink skin!

Wait. Pink skin? Aren’t most dolphins grey? And long beaks? If you’ve seen many saltwater dolphins, that may not sound quite right. But we’re talking about a specific freshwater dolphin. The Amazon river dolphin, to be exact!

The Amazon river dolphin is also called the boto. It lives in the basins of the Amazon and Orinoco Rivers of South America. When the rivers flood, they fill thousands of miles of the rainforest. This expands the boto’s habitat. During rain seasons, botos can be seen swimming through and around flooded tree roots and other plants of the rainforest. 

It’s the boto’s looks that really set it apart from other dolphins. Special vertebrae make it able to steer through trees by bending at 90-degree angles. Its beak is longer, and its forehead much rounder, than those of most dolphins you’ve likely seen. They’re also a bit smaller, at around eight feet and 450 pounds. And yes—many Amazon river dolphins have bright pink skin!

What makes their skin pink? That’s the real mystery. Experts still disagree over what causes botos to turn pink. However, they do know that all Amazon river dolphins are born grey. Some of them—usually males—turn pink later in life. And often, they grow pinker as they age.

This leads some experts to believe the pink skin is scar tissue. Male botos are known to fight a lot. They may turn pink as their bodies accumulate battle scars. This would also explain why botos become pinker with age. After all, older dolphins have likely been in more fights and gained more scars.

Other scientists believe the boto’s pink skin is pink to help it hide from predators. After all, the mud of the flooded rainforest floor often takes on a reddish color. It would make sense for botos to develop pink skin in an attempt to blend in. 

And blending in is definitely something many botos are interested in doing. Many of them tend to be very shy. That makes it difficult for experts to know just how many of them there are. When botos do show an interest in humans, though, they’re very friendly. They’re sometimes known to play with children in shallow water. 

If you believe local legends, botos go to great lengths to be friendly with people. A South American myth claims that Amazon river dolphins have the ability to turn into human beings. The story goes that they can be seen walking near water at night, wearing hats to cover their blowholes.

Unfortunately, not all people are quite so friendly to botos. They often run into trouble with fishermen. Some fishermen use boto as bait for fish. Others kill them because they see botos as competition for fish. Many botos are also accidentally killed each year when they’re caught in fishing net meant for smaller fish.

Would you like to see a boto one day? How about one disguised as a human being? That old story may not be true, but there’s still something magical about these bright pink dolphins! 

Standards: NGSS.LS1.A, NGSS.LS2.C, NGSS.LS4.C, CCRA.R.4, CCRA.L.3, CCRA.L.6, CCRA.R.1, CCRA.R.2, CCRA.W.4, CCRA.SL.1, CCRA.SL.2, CCRA.W.3, CCRA.L.1, CCRA.L.2, CCRA.R.10

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