A video of an alligator in West Tennessee captured by a TWRA worker quickly went viral, garnering more than 10,000 shares within eight hours of its posting.

The sighting is unusual, since alligators are not native to Tennessee, but the animal is not the only non-native species to migrate to Tennessee. Armadillos and a subspecies of cougar native to the Western United States have both been confirmed in the Volunteer State.

"Critters are just looking for new territory," TWRA spokesman Matt Cameron said. "The populations grow to the point where wherever they're existing, that habitat can't support them anymore, so they start moving out into other areas just to see if they can make a living there."

The alligator in TWRA's video likely didn't travel far.

Mississippi has a well established, breeding population of alligators. Cameron says nearly 750 alligators were harvested last year in Mississippi. The alligator in TWRA's video was in Fayette County, which sits on the Mississippi-Tennessee state line just east of Memphis.

"They can make it in colder water than people realized and obviously we're seeing that right now in West Tennessee," Cameron said.

Cameron says alligators have been spotted occasionally in West Tennessee for 10 years.

"We've seen manatees as far north as Memphis, bull sharks documented all the way up to Illinois, so a lot of things go up and down the Mississippi River, so it's not too surprising to see alligators," Cameron.

Armadillos Expanding Eastward

Another non-native species has established a much larger population.

TWRA says armadillos have only been in Tennessee for around 30 years.

The armored animal can be hunted year-round with no bag limit, but most armadillo sightings in Tennessee occur after the animal becomes roadkill.

A breeding population of armadillos exists in West Tennessee and has grown into the midstate.

Armadillos have been spotted as far East as the Cumberland Plateau, but Cameron says those animals have moved with human help.

"Every one of them from what I understand was a road kill and had been associated with vehicles that had been from the western part of the state, or even the western United States," Cameron said. "They could come on over, but I don't think they can survive very cold winters, so to have them right here in the mountains where we're standing is probably unlikely. The ridge and the valley could probably expect some armadillos there at some point."

Cougars Making a Comeback

After disappearing from the landscape, cougars are making a comeback in Tennessee.

The Eastern cougar was native to Tennessee, but in 2011 the US Fish and Wildlife Service concluded the subspecies was extinct.

However, TWRA has confirmed a cougar subspecies considered a cousin of Tennessee's native cat has been spotted in Tennessee 10 times since 2015.

"As a wildlife biologist, I think it's exciting to know that an animal we once had is probably going to make a return into Tennessee, but to have a breeding population of those, it would take decades," Cameron said.

Unlike the reintroduction of elk, which TWRA has strategically planned and managed, the cougar comeback is the product of nature.

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All 10 confirmed cougar sightings have been in West and Middle Tennessee.

DNA testing from one cougar in West Tennessee suggested that the cat was related to cougars in the Black Hills of South Dakota.

"Animals are expanding. It's exciting in a lot of ways, but I don't think we'll ever any of those three in large numbers in East Tennessee," Cameron said.