Gray Wolf
Photo: Gary Kramer, USFWS, Creative Commons

A classic favorite movie in our house is Napoleon Dynamite, and here’s one of our favorite scenes:his drawing of a “liger.”

But were you aware that ligers really exist?

My friend Laura is one of my go-to scientists. She not only teaches AP Biology, but also POST-AP Biology, for high school seniors who can’t get enough Biology. Kids flock to take her classes. I ask her for help on pretty much all my books. (Here’s a post I did about inbred monarchs, with Laura’s help.)

So at dinner the other night, I asked her to help me define “species” for my dog book. Dogs are a subspecies of wolf, but I was getting all balled up trying to define that. It used to be so simple. A species used to be defined as similar organisms that could mate and produce fertile offspring.

But Laura explained that sometimes the barriers to reproduction to two species can be removed when habitat conditions change. “Species,” then, can be context specific. If the context changes, then two species can hybridize and become one.

For instance, explained Laura, take Lake Victoria cichlids. “Changes in light conditions due to pollution mean that two species of the genus pundamilia will mate when before they wouldn’t. Females pick mates based on their color. So in the polluted water, the females can’t tell the difference between the two species of male and will mate with either. The hybrid babies are just as fit (in the evolutionary sense–they are just as able to have babies) as mom and dad, so scientists think the two species will fuse back into one.”

In case you’re wondering, she’s talking about a genus of fish. (I had to look that up.)

What does this have to do with ligers? Well in part due to global warming, a major barrier to reproduction has been removed. Polar bears’ habitat is vanishing, so they’re moving south and mating with grizzly bears. So now there are:

Grolar Bears

Polar/Brown Bear adult hybrid. Rothschild Museum, Tring, England.
Sarah Hartwell (Messybeast) via Wikimedia Creative Commons Share-Alike

And whales and dolphins have mated and created:

Wolphins.

Second-generation wolphin female “Kawili Kai” (*23 December 2004) at Sea Life Park Hawaii, 9 months old. Offspring of first-generation wolphin female “Kekaimalu”
Photo by Mark Interrante via Wikimedia Creative Commons Share-Alike

And yes, lions and tigers have mated and created:

Ligers

Photo of male and female ligers (a liger is a cross-breed of a male lion and a female tiger) taken at Everland amusement park, South Korea.
Photo by Hkandy via Wikimedia Creative Commons Share-Alike

Here’s Laura in class, getting a surprise visit from her son, Matt, who is a “uniman.” Did I mention Laura is married to a unicorn?