“The powers that be wouldn’t listen to me until it got down to six penguins,” said Mr. Marsh, whose long-unused birth name is Allan. “They were desperate.”

The farmer’s simple solution — deploy a particularly territorial breed of sheepdog to scare the foxes away — became local legend and, in September, the subject of an Australian film, “Oddball,” which fictionalized the story and made a lovable hero of one of the dogs. The strategy is now being tried elsewhere in Victoria, in hopes of protecting other indigenous species from non-native predators.

Dozens of Australian mammal species have gone extinct since European settlers began arriving in the late 18th century, bringing cats, foxes and other predators new to the ecosystem. A recently announced plan to cull millions of feral cats, which the government says prey on more than 100 threatened species, drew new attention to the problem while infuriating some celebrity advocates of animal rights.

Little penguins, the smallest penguin species, were once common along Australia’s southern coast. But when red foxes were imported for sport hunting in the 19th century, they found the tiny, flightless birds to be easy prey. (So did cats and dogs.) The penguins’ colonies on the mainland began disappearing, which is why most are now found on islands.

Middle Island, near the city of Warrnambool in Victoria, was home to a deafening population of the birds until the late 1990s and early 2000s, when tidal patterns and increasing sedimentation began to make the small, uninhabited island accessible from the shore. Foxes made their way there, and the birds offered little resistance.