Two-headed snakes do exist, but they are rare and do not tend to survive in the wild. These snakes are born as a result of an embryo that had split into two to form twins but stopped midway through the process. Such creatures generally do not survive because the two heads are each in competition with one another for prey and will even try to kill each other. In captivity, two-headed snakes have a much better chance of survival. For example, a two-headed snake named Thelma and Louise at the San Diego Zoo survived for 16 years. The occurrence of two-headed snakes is rare, with about 1,000 documented cases in history.
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