A 5.2-gram diamondback terrapin hatchling with two distinct heads was found at a protected nesting site in Wellfleet and taken to the Cape Wildlife Center. Photographs posted by the center show the rare condition known as bicephaly, which occurs when conjoined twins fail to fully separate during development. Veterinarians will closely monitor the terrapin’s appetite, growth and behavior. Diamondback terrapins are a threatened species in Massachusetts, and this is the center’s second such case in five years.
Rare Two-Headed Diamondback Terrapin Hatchling Discovered on Cape Cod
The hatchling's two heads are the result of a rare developmental condition known as bicephaly that can occur in reptiles and other animals (Cape Wildlife Center)
A tiny, two-headed diamondback terrapin hatchling weighing about 5.2 grams was discovered Thursday at a protected nesting site in Wellfleet, Cape Cod, and transported to the Cape Wildlife Center by staff from the Mass Audubon Wellfleet Bay Wildlife Sanctuary.
The Cape Wildlife Center posted three photos of the hatchling on Facebook showing two distinct heads — a rare developmental anomaly called bicephaly. The center said its veterinary team will closely monitor the terrapin as they study how the two heads and single body coordinate movement, feeding and growth.
The baby turtle is only the second case of bicephaly that the Cape Wildlife Center has seen in five years (Cape Wildlife Center)
What Is Bicephaly?
According to National Geographic, bicephaly results when conjoined twins fail to fully separate during embryonic development. The condition is rare but is most often reported in turtles and snakes; it can also occur in other species.
The Cape Wildlife Center noted this is only the second bicephalic terrapin it has seen in the past five years. In 2021, a widely shared photo showed a similarly unusual hatchling — nicknamed a "McNugget-size" turtle — that had two heads and six legs.
The turtle is reportedly behaving normally, according to New England Wildlife Center CEO Zak Mertz (Cape Wildlife Center)
Many two-headed animals face higher mortality because of physical challenges such as competing for food or inadvertently injuring one another, though reptiles sometimes survive longer than mammals in such situations, National Geographic reports. For now, the Cape Wildlife Center veterinarians are monitoring the hatchling’s appetite, growth and behavior to assess its prognosis.
Diamondback terrapins are considered a threatened species in Massachusetts, which adds conservation interest to the discovery. New England Wildlife Center CEO Zak Mertz told CBS News that the hatchling appears to be behaving normally so far and that both heads and sides are "looking very good."
The Cape Wildlife Center’s veterinary staff have treated several unusual cases in recent years, from an owl found inside a resident’s bathroom to the rehabilitation of a coyote pup and surgical care for a goose. The team says each uncommon case provides learning opportunities for animal care and conservation.
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