Yes, blood. Blood out the eyes. It's a display that's as impressive as it is shocking — in a last-ditch effort to ward off predators, several species of horned lizards will increase the blood pressure in vessels surrounding their eyes, to the point that they actually rupture, gushing five-foot fountains of hemoglobin at the faces of coyotes, bobcats, and other beasts of prey native to the Sonoran desert.

Write UT Austin biologists Eric Pianka and Wendy Hodges:

At least four species of horned lizards (but not all species), coronatum, cornutum, orbiculare and solare, squirt blood from their eyes when attacked, especially by canine predators such as foxes and coyotes. The canine will drop a horned lizard after being squirted and attempt to wipe or shake the blood out of its mouth, clearly suggesting the fluid has a foul taste. Older horned lizard phylogenies suggest that blood squirting behavior either evolved independently 4 times or it evolved only once and was then lost in subsequent lineages.

Growing up in southern Arizona, horned lizards were a common sight in my backyard, and the desert washes surrounding my house — and while I'd always heard tell of their blood-squirting abilities, I never actually got to see one autohemorrhage in person. But as far as I'm concerned, the video up top serves as a pretty good alternative to seeing it live.

More on horned lizards here.

Via WTF, Evolution — a tumblr that continues to deliver on the promise integral to its title.