Just off the mouth of the Mississippi, a rare breed of Chinese deer has found a new home--and new hope--for its embattled species. Further east, the gopher tortoise, one of nature's expert diggers, recovers from catastrophic population decline brought on by human encroachment and habitat loss. Track the exciting efforts to revive some of the lesser-known animal empires.

Off the southern coast of Australia, a group of western grey kangaroos enjoys life on the predator-free and aptly named Kangaroo Island. Further south lies Phillip Island, a refuge for the smallest species of penguin in the world. Journey to some of the animal world's more welcoming natural enclaves.

Sometimes, a species' survival hinges on inhabiting an area that isn't theirs. From the ubiquitous brown rat to the seals of Pier 39 in San Francisco and the flying foxes of South Eastern Australia, meet nature's unwelcome guests who've found a way to impose themselves onto new and unlikely environments.

While seafaring elephant seals and tundra-traversing caribou are impressive travelers, monarch butterflies may be the most amazing migrators of all. Theirs is a cross-generational journey that involves laying their eggs en route, dying, and relying on offspring to finish the trip. Join us as we map their epic travels.

When domestic animals escape into the wild, some revert back to their origins and thrive. From wild donkeys in Bonaire to feral pigs in the Bahamas to the wild horses of Assateague, each has found success by reclaiming ancient codes of social living. But can their new environment sustain them forever?