A rare two-headed baby diamondback terrapin has been discovered at a protected nesting site in Cape Cod, Massachusetts. The hatchling, which has two fully formed heads attached to a single body, was found in Wellfleet last month by representatives of the Mass Audubon Wellfleet Bay Wildlife Sanctuary.
It was subsequently transferred to the Cape Wildlife Center in Barnstable on September 17 for specialist care. The turtle weighs just 0.18 ounces, roughly the weight of a nickel, and is being closely monitored by veterinarians because of the potentially serious complications associated with its unusual anatomy.
The condition, known as bicephaly, occurs when a single embryo does not completely separate during the development of identical twins, resulting in two heads sharing one body. The Cape Wildlife Center said it had encountered only two other bicephalic terrapins over the previous five years, making the latest discovery particularly rare.
Rare tiny baby turtle with two heads discovered in US
“While we’ve encountered this unusual condition before, every case gives us another opportunity to learn more about these fascinating animals’ anatomy and physiology,” the centre said. “For now, our team is monitoring this little one’s (two’s?) appetite, growth, and behaviour closely.”
Research has found that two-headed turtles can experience abnormalities affecting the skull, face and spine and are often smaller than normal hatchlings. Their unusual anatomy can also interfere with essential functions such as movement and feeding, making survival more difficult. A 2021 study examining two-headed and partially duplicated sea turtles highlighted the significant challenges faced by animals born with the condition.
Scientists believe bicephaly may result from a combination of genetic and environmental factors. Zak Mertz, chief executive of New England Wildlife Centers, which includes the Cape Wildlife Center, said available research indicated that both genetic and epigenetic factors could contribute to the condition.
“Our understanding based on the available research is that bicephaly is caused by both genetic and epigenetic factors,” Mertz said. “It may have to do with the relatively long lifespan of the turtles, their preference for returning to the same nesting sites, and a limited gene pool due to their conservation status.” He said environmental conditions could also influence the development of the abnormality.
Rare tiny baby turtle with two heads discovered in US
“It may also be influenced by environmental factors, such as the temperature, humidity during incubation, physical characteristics of the nesting sites, or potentially even things the parents are exposed to in the environment,” Mertz said. The two-headed terrapin is not the only example of bicephaly recorded in wildlife. Other reported cases have included a two-headed porpoise found off the Netherlands and a double-headed dolphin discovered on a beach in Turkey.
Researchers say the rare hatchling could provide an opportunity to learn more about how such developmental abnormalities occur and what they may reveal about the health of turtle populations and their habitats. Diamondback terrapins live in brackish marshlands along the Atlantic and Gulf coasts of the United States, where fresh and salt water mix. The species is classified as threatened under the Massachusetts Endangered Species Act.
For now, veterinarians at the Cape Wildlife Center are continuing to monitor the hatchling’s growth, feeding and behaviour as they assess whether it can survive despite its unusual condition. Mertz said: “It is fascinating and an area that certainly merits more study. We are excited to care for these two and learn as much as we can to inform future study in the process.”