Snakes are among the most feared animals on the planet. There are over 3,000 different species, from the four-inch Barbados threadsnake to the 40-foot anaconda. These legless, scaly vertebrates, found in almost every biome, can slither, swim, and even fly. Some snakes are born with two heads, while others can reproduce without males. Their unique qualities make them some of the weirdest animals to be found anywhere in the world.

01 of 07 Some Snakes Have Two Heads Life On White/Photodisc/Getty Images A few rare snakes are born with two heads, though they don't survive long in the wild. Each head has its own brain, and each brain can control the shared body. As a result, these animals have unusual movements as both heads try to control the body and go in their own direction. One snake head will sometimes attack the other as they fight over food. Two-headed snakes result from the incomplete splitting of a snake embryo that would otherwise produce two separate snakes. While these two-headed snakes don't fare well in the wild, some have lived for years in captivity. According to National Geographic, a two-headed corn snake named Thelma and Louise lived for several years at the San Diego Zoo and produced 15 single-headed offspring.

02 of 07 Video Cameras Have Recorded Snakes "Flying" Jerry Young/Dorling Kindersley/Getty Images Some snakes can glide through the air so quickly it looks like they're flying. After studying five species from Southeast and South Asia, scientists were able to determine just how the reptiles accomplish this feat. Video cameras were used to record the animals in flight and create 3-D reconstructions of the snakes' body positions. The studies showed that the snakes can travel up to 24 meters from a branch at the top of a 15-meter tower with constant velocity and without simply dropping to the ground. From the reconstructions of the snakes in flight, it was determined that the snakes never reach what is known as an equilibrium gliding state. This is a state in which the forces created by their body movements fully counteract the forces pulling down on the snakes. According to Virginia Tech researcher Jake Socha, "The snake is pushed upward—even though it is moving downward—because the upward component of the aerodynamic force is greater than the snake's weight." This effect, however, is temporary, and ends with the snake landing on another object or on the ground.

03 of 07 Boa Constrictors Can Reproduce Without Having Sex CORDIER Sylvain/hemis.fr/Getty Images Some boa constrictors don't need males to reproduce. Parthenogenesis is a form of asexual reproduction that involves the development of an egg into an embryo without fertilization. A female boa constrictor studied by North Carolina State University researchers has had offspring through both asexual and sexual reproduction. The baby boas that were produced asexually, however, are all female and bear the same color mutation as their mom. Their sex chromosome makeup is also different from the sexually produced snakes. According to researcher Dr. Warren Booth, "Reproducing both ways could be an evolutionary 'get-out-of-jail-free card' for snakes. If suitable males are absent, why waste those expensive eggs when you have the potential to put out some half-clones of yourself? Then, when a suitable mate is available, revert back to sexual reproduction." The female boa that produced her young asexually did so in spite of the fact that there were plenty of male suitors available.

04 of 07 Some Snakes Steal Venom From Toxic Toads Yasunori Koide/CC BY-SA 3.0 A species of non-poisonous Asian snake, Rhabdophis tigrinus, becomes poisonous due to its diet. What do these snakes eat that causes them to become poisonous? They eat certain species of toxic toads. The snakes store the toxins obtained from the toads in glands in their neck. When facing danger, the snakes release the toxins from their neck glands. This type of defense mechanism is usually seen in animals lower on the food chain, including insects and frogs, but rarely in snakes. Pregnant Rhabdophis tigrinus can even pass the toxins on to their young. The toxins protect the young snakes from predators and last until the snakes are able to hunt on their own.

05 of 07 Long Ago, Some Snakes Ate Baby Dinosaurs This is a life-sized reconstruction of a fossilized dinosaur nest discovered with Titanosaur eggs, a hatchling dinosaur, and a snake inside. Sculpture by Tyler Keillor and original photography by Ximena Erickson; image modified by Bonnie Miljour Researchers from the Geological Survey of India have discovered fossil evidence that suggests that some snakes ate baby dinosaurs. The primitive snake known as Sanajeh indicus was about 11.5 feet long. Its fossilized skeletal remains were found inside the nest of a titanosaur. The snake was coiled around a crushed egg and near the remains of a titanosaur hatchling. Titanosaurs were plant-eating sauropods with long necks that grew to an enormous size very quickly. The researchers believe that these dinosaur hatchlings were easy prey for Sanajeh indicus. Due to the shape of its jaw, this snake was unable to consume titanosaur eggs. It waited until the hatchlings emerged from their eggs before devouring them.

06 of 07 Snake Venom May Help Prevent Stroke Brasil2/E+/Getty Images Researchers are studying snake venom in the hope of developing future treatments for stroke, heart disease, and even cancer. Snake venom contains toxins that target a specific receptor protein on blood platelets. The toxins can either prevent blood from clotting or cause clots to develop. Researchers believe that irregular blood clot formation and the spread of cancer can be prevented by inhibiting a specific platelet protein. Blood clotting occurs naturally in order to stop the bleeding when blood vessels become damaged. Improper platelet clotting, however, can lead to heart attack and stroke. Researchers have identified a specific platelet protein, CLEC-2, that is not only needed for clot formation but also needed for the development for lymphatic vessels, which help to prevent swelling in tissues. They also contain a molecule, podoplanin, that binds to the CLEC-2 receptor protein on platelets similarly to the way snake venom does. Podoplanin promotes blood clot formation and is also secreted by cancer cells as a defense against immune cells. Interactions between CLEC-2 and podoplanin is thought to promote cancer growth and metastasis. Understanding how toxins in snake venom interact with blood may help scientists develop new therapies for those with irregular blood clot formation and cancer.