Genetic hybrids are the result of two animals of differing species mating to form a new species. Species from different parts of the world end up crossing paths for a variety of reasons. Whether it be due to invasive species colliding with locals, habitat destruction, or being placed in captivity, new hybrid species are formed that would not have existed otherwise. In many cases, they would never have existed without humans (for better or worse).
Here are three of the most interesting ever discovered…
#1: Hybrid “Super Snakes” Discovered in Florida Everglades
Over 30 years ago, various pet snakes were released in the wild in Southern Florida. These invasive species, most notably the Burmese python, have established growing populations, decimating the native species in the process.
Florida’s battle against invasive species got a lot tougher when a new hybrid snake was found lurking in the Everglades.
A recent US Geological Survey (USGS) study on the genetics of invasive pythons has revealed that a number of the snakes in the Everglades are actually a hybrid between two species orginally from Southeast Asia — the Burmese python and Indian rock python.
Burmese pythons, which have colonized the state in recent decades, are colossal constrictors generally found near water, while the agile, more aggressive Indian rock python spends the majority of its time on high ground. The resulting hybrid could lead to something of a “super snake,” a well-adapted reptile suited for both swamps and dry land. And, in fact, South Florida’s Burmese pythons have been spotted in both environments.
“When two species come together they each have a unique set of genetic traits and characteristics they use to increase their survival and their unique habitats and environments,” USGS geneticist Margaret Hunter told the Guardian. “You bring these different traits together and sometimes the best of those traits will be selected in the offspring. That allows for the best of both worlds in the Everglades, it helps them to adapt to this new ecosystem potentially more rapidly.”
This phenomenon, where the best traits from both parents are enhanced in the hybrid offspring, is known as “hybrid vigor”. What this means for the snakes in the Everglades, though, is still unclear.
This isn’t the first time the idea of a super snake in Florida has come up. Back in 2010, reports of a possible hybrid between Burmese pythons and African rock pythons — which have been known to attack humans — stoked fears that it could give rise to an unusually aggressive super-predator.
But as alarming as this all sounds, the researchers say that a new reptilian terror isn’t necessarily taking over the state. In fact, they believe the interbreeding between the Burmese and Indian pythons likely happened before they became established in the area.
Still, the findings suggest that it will likely be even more difficult to reduce the already staggering python population than scientists had originally thought.
#2: Grizzly-Polar Bear Hybrids
As global temperatures rise, ecosystems and the species they harbor are adjusting in response. Many habitats are either shifting their boundaries polewards—or disappearing altogether—sending wildlife into new regions, where they interact with resident creatures in surprising and often unprecedented ways.
When this geographic collision is between two closely related species, they sometimes cross-breed, leading to the emergence of an entirely new species. Perhaps one of the most fascinating examples of this is the grizzly-polar bear hybrid: the “pizzly” or “grolar” bear.
Brown bears (Ursus arctos)—of which grizzlies are a subspecies—and polar bears (Ursus maritimus) are different species with different adaptations to their respective ecosystems, but they are closely related. Polar bears diverged from brown bears less than 500,000 years ago—not long at all on an evolutionary timescale—and the two animals retain enough genetic similarity that they can interbreed and produce fertile offspring.
When the hybrid offspring come from a polar bear father and a grizzly bear mother, the hybrid is typically called a “pizzly” bear, a portmanteau of “polar” and “grizzly.” When the parentage is reversed? A “grolar” bear.
Much of what we know about “pizzlies” and “grolar bears” comes from hybridization in captive conditions, specifically in zoos. In these situations, the hybrids are often the result of the two bear species cohabitating in the same enclosures. Around seventeen of these hybrid bears are known to exist, mostly in European zoos.
The hybrids present as an amalgamation of the key characteristics of their parents. Their fur isn’t white or brown, but a dingy, creamy blond. They have long necks like polar bears, but hunched shoulders like grizzlies. Their feet are partly covered in fur, intermediate between the bare paws of grizzlies and the fuzzy feet of polar bears. Their heads blend together the sleek features of polar bear heads and the thick, rounded features of grizzly heads.
In regards to behavior, though, the hybrids more resemble their polar bear parents, hurling large toys and stamping on objects in a similar fashion. They also lie down with their hind limbs splay-legged—a distinctive polar bear pose.
Pizzlies and grolar bears are undoubtedly striking curiosities, but how regularly do they show up in the wild? Not that often. Many purported hybrids end up being purebreds of one of the two bear species. In 2016, a bear shot in Nunavut, Canada was thought to be a hybrid based on its cream-colored coat, but genetic testing later determined that it was just a grizzly with a rare, blond coat.
However, true hybrids have definitely turned up in the wild in recent years. One of the most famous cases also comes from Nunavut, but a decade earlier. In 2006, an American hunter shot what was thought to be a polar bear (for which he had a hunting permit), albeit with strange features.
After much drama and the possibility of incurring fines and jail time for targeting a species for which he had no permit, the hunter was let off the hook by genetic testing results, which confirmed that this was a special case: a wild grizzly-polar bear hybrid, thought to be the first ever recorded. In 2010, another bear—this time from the Northwest Territories—was confirmed by genetic testing as a three-quarters grizzly hybrid.
These hybrid bears come from areas in northern Canada where grizzlies and polar bears are crossing paths with increasing frequency as grizzlies encroach on polar bear habitat. A large part of this upswing in grizzly and polar bear encounters is likely due to climate change.
Grizzlies don’t typically stray north of the treeline in the Arctic, and permafrost is too frigid for them. But as permafrost rapidly melts and prey moves poleward into polar bear-inhabited coastlines, grizzlies are bumping into polar bears and mating with them. Likewise, as sea ice wanes, polar bears will likely find themselves stuck in terrestrial locations filling with a slow creep of grizzly invaders.
Rather than “grolar bears” taking over the Arctic, the real risk is that what we know as polar bears will simply be absorbed into a tide of grizzly DNA through successive crossbreeding events. While research suggests that the possibility of climate change-induced hybridization is still low for most species, it is already threatening animals like cutthroat trout, and could someday pose a similar extinction threat to polar bears if it continues unabated.
#3: Meet the Liger: Half Lion, Half Tiger and the World’s Largest Feline
Meet the world’s largest feline: the liger. While ligers are certainly something to marvel at, you’ll never found one outside of a zoo—they’re a man-made hybrid cross between a male lion and tigress, something that would never occur in nature.
Ligers look something like a striped lion. They tend to inherit the tawny brown fur from their lion fathers and the dark stripes from their tigress mothers.
As a result of this union between the tiger, the largest and heaviest feline, and the lion, the second largest, ligers tend to be much larger and heavier than their parents. In fact, the largest feline in the world according to the Guinness Book of World Records is a liger named Hercules, who weighs 922 pounds and measures 11 feet in length and 4 feet at the shoulder. He resides at Myrtle Beach Safari, a wildlife attraction in South Carolina.
Unfortunately, ligers face a host of challenges. Like many other unnatural hybrids, ligers often die in the womb or prematurely. If they do make it to adulthood, they are genetically or physically sterile and unable to reproduce.
They also suffer from a variety of uncomfortable genetic defects and diseases associated with both lions and tigers, such as neurological problems, cancer, arthritis, and organ failure.
For these reasons as well as the lack of conservation value and the threat to the mother tigress during birth, ligers are banned in most zoos and animal sanctuaries; and those that choose to breed the animals are frowned upon by big cat conservationists around the globe.
Watch the video below to see a liger in motion: