The condition when a species has more than one head is called polycephaly. Specifically if there are two heads it’s called bicephaly, while having three heads is tricephaly. There is no record in history of any species having more than three heads.
While having two heads is extremely rare, it can affect any vertebrate. Bicephaly has been reported in turtles, lizards, humans, snakes and other creatures. Although it’s more common for reptiles to be bicephalic because they produce a large amount of offspring and most reptiles lay eggs. These eggs are then exposed to environmental conditions which affect the development of the embryo inside.
However, bicephaly can result from both genetic and environmental anomalies during the development of an embryo. Either an embryo splits in two (which is how identical twins are formed), or it splits incompletely and that’s what causes conjoined twins in humans. But in the case of two-headed animals, two separate embryos fuse together but only partially.
The Two-Headed Baby Loggerhead Turtle
Baby loggerhead turtles have a lot of danger between them and adulthood. Their chances of survival on the beach are extremely low, with constant threats from hungry birds, crabs, and small animals. But once they’re in the water it doesn’t get any easier for them, as seabirds, fish, and sharks pose just as much of a threat. Not to mention, two heads on one body only makes the journey that much harder.
Under the US Endangered Species Act (ESA), all populations of this turtle species are currently listed as endangered or threatened. That’s why sea turtle patrol groups all over the world help protect this vulnerable animal by monitoring its hatcheries and preventing threats while aiming to keep everything natural for the creatures by letting nature take its course as they travel into the sea.
Recently, while a sea turtle patrol on Hilton Island in South Carolina was monitoring sea turtle hatchlings they found an extremely rare oddity. To their surprise, there was a little hatchling with two heads, which they named Squirt and Crush after Nemo’s reptilian pals. Believe it or not, this was not the first bicephalic turtle they found. About 15 years prior they found their first-ever two-headed turtle.
The conservationists did not collect the bicephalic hatchling to hold in captivity, instead, they released it into the sea along with its brothers and sisters. Unfortunately, the baby turtle struggled to crawl due to its abnormally-shaped shell and it’s unknown whether or not it will survive in the big scary ocean as the survival rate of healthy hatchlings is already normally low. The reality is, somewhere between one in 1,000 and one in 10,000 are estimated to actually survive to adulthood.
The turtle’s discoverer, Jayme Davidson Lopko, wrote in a Facebook post:
Sea turtle patrol follows rules set by the State Department of Natural Resources which calls for us to protect the nests and turtles but to also allow as natural a process as possible. We do not take hatchlings off the beach to raise or rehabilitate. This little guy is on his own just like his brothers and sisters that came from the nest and like they have been doing for millions of years. Good luck and safe travels special guy!
The Two-Headed Western Rat Snake
A two-headed snake must be up on the top of the list with the five-legged lamb of world’s most unusual pets. Meet Gumbo and Filo: the pet bicephalic snake from Louisiana. The twins belong to Tanee Janusz, who sits on the board for the local Master Naturalist Program. Gumbo and Filo became part of Janusz’s family, when a friend offered the pair to her. The friend, also on the board, originally found them slithering around his backyard.
Even though the twins share a tail, a digestive and reproductive tract, they have distinct personality traits and often struggle to control the direction of their body. Both of them are feisty but Gumbo is the more dominant of the two.
Janusz says caring for them is not much different to caring for a regular snake:
The only difference is making sure that their water bowl is not too deep as the dominant head will drag the non-dominant head down into the water.
Polycephaly is estimated to affect one in every 10,000 snake births. Janusz believes that despite the condition, Gumbo and Filo will survive the lifespan of most western rat snakes, which is 10 years in the wild and 20-25 years in captivity.
The Two-Headed Baby Deer
Not far from the Mississippi River, a mushroom picker in Minnesota came across a two-headed fawn while searching for delicious fungi. This is believed to be the first known conjoined twin fawns that have reached full term and were delivered by the mother. There have been other conjoined fawns seen before but only in utero.
Gino D’Angelo, who co-authored a paper on the fawns in the journal The American Midland Naturalist, explains:
Their anatomy indicates the fawns would never have been viable. Yet, they were found groomed and in a natural position, suggesting that the doe tried to care for them after delivery. The maternal instinct is very strong.
Since the fawns were in impeccable condition, scientists had the opportunity to carry out a full necropsy on them. The scientists performed a CT scan on the baby deer, in addition to a dissection. They discovered that the twins were both females, with two separate heads and necks that converged about halfway down the rib cage. Their fur, heads, and legs were perfectly normal and there was even an almost perfect spot pattern running down their neck.
Internally, tests proved that their lungs had never breathed oxygen, which confirmed that they were stillborn. The twins shared one liver but had extra spleens and gastrointestinal tracts. While they had only one pericardial sac, they had two hearts.
There have only been five official cases in history of polycephalic deer, with two of these in white-tailed deer, but both of them were fetuses that were never delivered. D’Angelo said, “It’s amazing and extremely rare, we can’t even estimate the rarity of this. Of the tens of millions of fawns born annually in the U.S., there are probably abnormalities happening in the wild we don’t even know about.”
The Two-Headed Neotropical Fruit Bat
The male conjoined bat twins were found under a mango tree in the forests of the Viana municipality in southeastern Brazil. Since their discovery in 2001, the twins have been placed in a solution of 70% ethanol to help preserve their tissue, until a proper scientific investigation could be made. After spending years in the Laboratorio de Mastozoologia, scientists from the State University of Northern Rio de Janeiro have finally taken up the honor of studying this unique specimen.
Since the placenta was still attached to the bats shared body, the researchers believe they were either stillborn or died shortly after being born. However, even if they would have survived, it’s unlikely that they would have lived longer than a few days with all the dangers that mother nature holds.
X-rays and ultrasonic images of the bats reveal that they share two complete forelimbs and two complete hind limbs, just like a regular bat. However, they have two separate spines that branch down into a single lumbar region (the bottom of the spine). They have only one penis and two separate similarly-sized hearts.
This is just the third pair of conjoined twin bats that have ever been recorded in history. In humans, conjoined twins vary from region to region, one in every 200,000 in the US have it while it may be as high as one in 2,800 in India. Archaeologists have even discovered records of conjoined humans dating all the way back to the sixth millennium BCE.
