Just when you think the world has all the rats it needs, LSU researcher Jacob Esselstyn has discovered a new one — a carnivorous water rat — in central Indonesia. The species was previously known only to the locals in the western highlands of Sulawesi Island.

“We knew right away it was a new genus,” says Esselstyn, 40, who was part of the discovery team. “There are no semi-aquatic rats in that part of the world.”

The short-eared, thick-furred rodent measures 4½ to 5 inches, not counting its tail, which has long hairs on the bottom, helping it dive for its dinner — the insects found on the stream bottoms, says Esselstyn, who is curator of mammals at LSU’s Museum of Natural Science. The new rat has been officially christened “Waiomys mamasae” meaning “water rat of Mamasa.”

The locals keep the rats, which are killed and preserved, in their homes as protective talisman, Esselstyn says.

It shows, the researcher says, that there are lots of mammals in the world to be discovered. A couple of years ago, Esselstyn was part of a group that found a worm-eating rat. And he’s not done yet.

“I’m working on another rat now,” he says, but is mum on the details.