No, this is not a trick of the eye.
A rare two-headed baby turtle discovered at a protected nesting site on Cape Cod, Massachusetts, last month is surviving despite the long odds.
The hatchling is a diamondback terrapin weighing roughly as much as a nickel. The Cape Wildlife Center said on Facebook that it has bicephaly, an uncommon developmental condition in which an animal develops two heads.
The Mass Audubon Wellfleet Bay Wildlife Sanctuary brought the tiny turtle to the Cape Wildlife Center, where staff are providing care and monitoring its condition closely.
Bicephaly occurs when a single embryo does not completely divide during the development of identical twins, leaving two functioning heads attached to one body, according to Live Science.
The Cape Wildlife Center said it has documented only two other cases of bicephaly in the past five years, making this double-headed hatchling “especially rare.”
“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 center said.
For now, staff are keeping a close watch on the hatchling’s appetite, growth and behavior — or, as the center jokingly put it, the appetite and behavior of “this little one’s (two’s?).”
The discovery represents an unusually rare example of bicephaly in turtles, said Zak Mertz, CEO of New England Wildlife Centers, the organization that includes the Cape Wildlife Center.
“It is fascinating and an area that certainly merits more study,” Mertz told the outlet. “We are excited to care for these two and learn as much as we can to inform future study in the process.”
Mertz said available research indicates that the unusual condition may result from a combination of genetic and epigenetic factors.
He said the turtles’ relatively long lifespans, tendency to return to the same nesting sites and limited gene pool — linked to their conservation status — could all play a role.
Environmental conditions may also contribute, Mertz added. Possible influences include incubation temperature and humidity, the physical features of nesting sites and even substances to which the parent turtles are exposed.
Although two-headed animals are exceptionally uncommon, they are not unheard of. Recent examples include a two-headed porpoise discovered off the Netherlands and a double-headed dolphin found on a beach in Turkey.
A 2021 study titled “Two heads are not always better than one” found that double-headed or partially duplicated sea turtles often have serious craniofacial and spinal abnormalities. Craniofacial abnormalities affect the structure, bones and soft tissues of the skull and face.
The study also found that two-headed turtles are generally smaller than other hatchlings and face major survival challenges because of their abnormal anatomy.
Because bicephaly can threaten a turtle’s ability to survive, scientists say monitoring these rare animals can provide valuable insight into the health of the species and its habitat.
Diamondback terrapins live in brackish marshes along the Atlantic and Gulf coasts of the United States. In Massachusetts, they are listed as threatened under the state’s Endangered Species Act, according to the outlet.