Today I would like to introduce you to the hoatzin. These birds live along the rivers of northern South America. They’re kinda derpy, they’re clumsy, they stink, and they have some really unique features. And I’m not talking about that cool crest they sport!
If you already know hoatzins, you most likely know them for their retention of their dinosaur clawed fingers – at least when they are juvenile. But they don’t use these claws for fighting or killing. Hoatzin nests are built above rivers for a reason. When a predator comes too near the nest, baby hoatzins save themselves by jumping out of the nest and belly flopping into the water. They use their dagger hands for climbing out of the river and up the tree again. As they grow feathers they lose their hands, apparently to fit in with all the other modern avians. Peer pressure, am I right?
And while that is enough to find this species fascinating, it isn’t the end. They’re folivores, animals that primarily eat leaves! Now, this is actually a minor problem, because leaves are not very energy rich and contain a lot of cellulose. Most animals that eat leaves usually have either complex stomachs (cows, sheep, whatnot) or very low metabolism (sloths, koalas, etc). These solutions are generally not good for birds since they need to fly, which is probably why most birds aren’t folivores. But hoatzins? They’ve got it covered. They get their leafy nutrition fix by having a huge crop. In most birds, this is like a storage pouch in their esophagus. This is usually where they store food to regurgitate for their young. But the hoatzin’s crop is not only huge, it also is host to some pretty powerful bacteria that breaks down the nibbled foliage. This process ferments the leaves and makes it digestible. It also gives the hoatzin their signature stank.
The hoatzin funk is probably one of the reasons they’re fairly successful. People don’t hunt them because, well, ew. They aren’t hunted by other animals because, well, ew. Their babies are probably more of a tasty morsel as they have yet to develop the stank, but their belly flop strategy probably makes hunting them a hassle for solo hunters. Because of this, they’re pretty tame and unsuspecting. And for birds, they seem to hate the idea of flying. In fact, they’re horrible flyers. Their diet and huge crop interfere with the development of their flight muscles, and having little need for escape or aerial hunting, their flying capacity has gone to shit. Probably the only reason they haven’t gone flightless is because their food is in the trees and flying awkwardly to another branch is better than just falling out of the tree every time they lose their balance. And let’s face it, they aren’t particularly graceful in the climbing department either.
Gah, they’re just so adorkable! I love them!