For instance, the continent is home to more than 378 mammal species, which range from the rain forest-dwelling tree kangaroo to the venomous platypus.

Brian is one of these lesser-known marsupials. He's an eastern bettong—essentially, a mini-kangaroo.

"They absolutely bounce around like a kangaroo," says Kate Grarock, an ecologist at the Woodlands and Wetlands Trust, a nonprofit that manages two nature reserves in Australia's capital city. "They're pretty darn fast."

Brian—"our cheeky little spokesman"—was rescued about three years ago, after his mom threw him out of her pouch during a routine health check by biologists, Grarock says. "It doesn’t happen often," she notes. "We always try to reunite the baby with its mother, but sometimes we can’t." (Read about an "extinct"