16 Fascinating Photos Of Two-Headed Animals Found In Nature

Published August 5, 2017
Updated November 9, 2023

From turtles and snakes to cows and pigs, two-headed animals are not only astounding but perhaps not quite as rare as you might think.

Two-Headed Animals Turtle
Calf Eating
Bearded Dragon
16 Fascinating Photos Of Two-Headed Animals Found In Nature
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Strange though it may seem, two-headed animals have been documented among many different species, although most tend to fall within the realm of turtles, snakes, and traditional livestock animals such as cows, sheep, and pigs.

While their appearance can certainly be shocking, the cause of their bicephalic bodies is nothing more than genetic mutation and cellular displacements, as the BBC writes.

When you see a two-headed, or polycephalic, animal, you're actually looking at a set of twins that failed to separate after fertilization. This can result in the conjoining of twins when a gene known as "sonic hedgehog" or "SHH" is increased during embryonic development, which can cause the head or face to widen, often resulting in two faces. When a group of cells known as organizers becomes triggered, two entirely separate heads can form, resulting in individual necks stemming from a single body.

So, what causes such genetic abnormalities? Depending on the species, there is a wide range of proposed explanations.

When it comes to sharks, for example, of which there have been many mutations witnessed, researchers look to a variety of possible factors ranging from metabolic disorders and infection to pollution or overfishing, the latter of which can lead to a limited gene pool resulting in physical abnormalities. Some also blame rising water temperatures, although research is still being conducted in an effort to truly understand how these changes might affect genetics.

Despite the recent influx of two-headed marine life being reported, polycephalic animals are believed to have been around since the early days of human civilization, perhaps inspiring ancient myths and tales that tell of multi-headed beasts slain by heroic protagonists of their time.

However, many of these two-headed animals don't live beyond the embryonic stage, and those that do survive birth typically don't make it more than a few weeks or months, though there are exceptions to the rule.

See some two-headed animals that did survive long enough to be photographed in the gallery above.

After this look at two-headed animals, check out 29 of the most unbelievably weird animals on planet Earth. Then, have a look at Earth's rarest animals.

Krissy Howard
Krissy Howard is a New York-based freelance writer. She regularly contributes to Runt of the Web and her original humor has appeared on The Hard Times, Reductress, and The Hairpin.
John Kuroski
John Kuroski is the editorial director of All That's Interesting. He graduated from New York University with a degree in history, earning a place in the Phi Alpha Theta honor society for history students. An editor at All That's Interesting since 2015, his areas of interest include modern history and true crime.