This episode is sponsored by Awesome Socks Club, a socks subscription for charity! Click the link in the description and sign up between now and December 11th to get a new pair of fun socks each month in 2021.

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Now, lots of animals pretend to be other animals either to scare off predators or lure in their prey. But the spider-tailed viper takes this to an almost unbelievable level. The snake's tail looks and moves like a spider to lure hungry birds close in.

Most snakes are what we call ambush predators. So, they sit still and wait for something edible to amble by, relying on stealth and a speedy strike rather than chasing down their prey. 

And that works great! If your preferred meal is something that happen by pretty often. But the spider-tailed viper has a taste for birds and birds are a little bit flighty. So evolution has outfitter these guys with a little something extra for tempting birds within striking distance - a fantastically spidery tail.

Now, interesting tail shapes are pretty common amongst snakes, just think of rattlesnakes that use their tails as warning buzzers or sorts. And there are other snakes, especially vipers, that use something called caudal luring. They wiggle their tails kinda like worms to draw in hungry critters. Some of these caudal luring snakes even have tails that are a different color from the rest of their body so that the lure stands out while the body blends in. But the spider-tail viper takes this up a notch with an impressive tail lure that looks and moves just like a spider. Spiders are tasty treats for many birds, so by looking like a spider the viper gets its prey to drop its defenses - a phenomenon biologists refer to as aggressive mimicry.

The lure itself is just a bunch of frilly scales. A baby snake of this species starts out with a normal viper tail. But as it grows up, the scales on the tip of its tail get more elongated, and the last two scales well up and become big and round, forming what looks like the body of a spider. Then, it's just a matter of the perfect dragging motion.

And spider-tailed vipers have also altered their behavior to ensure they catch their prey. Like, spider-tailed vipers are most active in Spring and Fall, when lots of migrating birds are passing through their habitat. And unlike their closest relatives, which are all active at night, spider-tailed vipers are all diurnal. For their strategy to work, they need to be awake during the day, when spider-hunting birds are.

Understanding how this amazing form of mimicry developed could teach us more about selection and evolution in other snakes, like how the rattle snake's famous rattle developed. But, we still know very little about this snake. It's from a remote region of Iran and was only described as a unique species about 15 years ago. Currently, the IUCN red lists it as data-deficient, meaning we don't even have enough information about it to know how it's doing overall. So, we've got a lot of great reasons to keep studying this awesome snake.

Now, before I go, I want to talk about one more awesome thing, the Awesome Socks Club! It's a charity sock subscription started by Hank and John Green, and if you sign up, then every month of 2021 you'll get a nifty pair of socks. Each month's pair will be designed by a different designer, so they'll all be fun and unique. But the best part is that 100% of after-tax profit will go to decrease maternal and child mortality in Sierra Leone. So, your stylish feet will be doing some real good in the world. The catch is, you can only subscribe until December 11th! So, if you want in on this awesome club, you want to click the link in the description sooner rather than later.