Volunteers monitoring a protected nesting site at Mass Audubon's Wellfleet Bay Wildlife Sanctuary recently turned up a hatchling unlike any they typically find: a diamondback terrapin with two fully formed heads, six legs and a single shell.
The hatchling, weighing just 5.2 grams, was transferred to the Cape Wildlife Center in Barnstable, which is run by New England Wildlife Centers, for observation. Staff say the condition, known as bicephaly, occurs when an embryo begins to split into twins but stops short of fully separating, leaving two heads and often two parallel digestive and nervous systems sharing one body.
In this terrapin's case, the two heads operate largely independently: each surfaces for air on its own schedule, and veterinary staff say both appear to have functioning appetites, feeding on blood worms and food pellets placed in their enclosure. The animal's unusual anatomy means staff have had to pay close attention to make sure both sides are getting enough to eat and neither is being out-competed by the other.
"Our veterinary team will be closely monitoring the little terrapin as we learn more about how their two heads and bodies work together," the center said. Staff plan to eventually perform a CT scan to better understand how the animal's circulatory and nervous systems are organized internally.
Bicephalic reptiles are exceptionally uncommon, and the Cape Wildlife Center said it has encountered only two comparable cases in the past five years, making this hatchling one of a small handful ever documented at the facility. Outside veterinarians describe survival past the first few weeks as especially rare for two-headed turtles, since coordinating movement and feeding between two heads sharing one body can prove fatal early on. For now, the hatchling is defying those odds, one bite at a time.