Animal hybrids are becoming more common because of climate change

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AUSTIN (KXAN) – Animal hybrids are rare in nature. Most species are incapable of breeding with other species, and when they do they often can’t reproduce. Think of the mule, a donkey/horse hybrid that’s been around for centuries. Then you have the Pizzly Bear, a polar bear/grizzly bear hybrid that’s been slowly growing over the past couple of decades..

This hybrid, and possibly others like it, are a direct result of climate change. Polar bears, driven south as the arctic melts and their hunting ground vanishes, have encountered grizzly or brown bears that have been pushed north by warming temperatures. The two bears are actually distant cousins, having diverged genetically about five hundred thousand years ago, and are capable of opportunistically mating.

Dr. Larisa DeSantis (senior author) at the University of Alaska Museum of the North. (Courtesy: Larisa DeSantis)

“This hybrid may give us some hope in a world that’s changing,” says Vanderbilt University Associate Professor Larisa DeSantis, “maybe this intermediate form could confirm some advantages.” DeSantis studies the diets of prehistoric animals, like the sabretooth tiger and even the polar bear.

The extinction of the polar bear

“Essentially, what we found is that polar bears are hyperspecialized at what they do.” DeSantis says that polar bears are designed for the far north, with thick layers of blubber keeping them warm, but also for eating seal and pretty much only seal.

The polar bear’s new hunting grounds (northern Canada, Alaska, Russia, Norway and Greenland) aren’t one they’re suited for. Their mouths are long and made to poke through holes in the ice to snatch seal, which are soft and also covered in blubber. As opposed to the grizzly, polar bears can’t eat nuts, berries or even break bones.

Polar bear skulls from the University of Alaska Museum of the North. (Courtesy: Larisa DeSantis)

“Until the 20th century, they’ve been eating soft things. We may be at a tipping point where they’re getting desperate.”

The problem with hybrids

Again, animal hybrids are rare. “Every species need to sexually reproduce,” says Dr. Misha Matz, a biologist studying undersea coral at the University of Texas. Coral are one of the species facing extinction because of climate change. Warming seas have decimated populations around the world, killing the algae that coral feed on.

If there were any other species that would hybrid, coral would be a prime candidate. Their reproduction is a bit more chaotic. “They times it precisely to one night within a year,” Dr. Matz says. “Most corals form within a 15 minute window at a given location.”

In that window, all the coral will simultaneously release their reproductive material in the ocean. “You see the potential for everything mixing up a little bit.” While hybrid species do occur after this mass reproductive event, it is still really rare. Dr. Matz says that instead what happens is the sharing of traits.

“Typically, hybrids are not as able to adapt to their environment as the parent species.” DeSantis says.

The Pizzly Bear, which was first documented in 2006, doesn’t have as much blubber as the polar bear. This means it couldn’t survive in colder temperatures. Nor is its diet as versatile as a grizzly’s, which includes plant and animal life.

However, as the world keeps warming, this new hybrid species might be better suited for it. “The Pizzly may be our best hope for an arctic bear,” DeSantis says that the Pizzly Bear population has increased since first being documented. Researchers say that hybridization because of climate change will likely become more common in the coming decades, not only amongst bears, but other species as well.

She says more study is needed before we’ll know which bear could be the apex predator of the north.

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