Hog-Nosed Rat Found in Forest

Deep in the forested mountains of Sulawesi, Indonesia, researcher Jacob Esselstyn found something quite curious in his trap. A furry rodent had a pink snout resembling that of a hog; underneath, its lower incisor teeth were a remarkable length.

An Assistant Professor and Curator of Mammals at the Museum of Natural Science at Louisiana State University, Esselstyn realized immediately that he discovered a new species of rat.

Hog-nosed rat put in pocket, Esselstyn hiked back to camp to show his team, a member of which was Kevin Rowe, Museum Victoria Senior Curator of Mammals. Though, what seemed like an individual discovery proved not to be; Rowe had, at the same time, come across his own hog-nosed rat.

“He was very close to our camp and he started shouting and he immediately told the other people around there about it,” Esselstyn tells BTR. “I was out of earshot at that point and had my animal independently and I just decided to be more discreet about it.”

Rowe’s rat news consequently circulated to Esselstyn upon his return back to camp.

“I calmly said ‘oh I have seen that before,’” he remembers reacting, “and they scoffed and I pulled one [rat] out of my pocket.”

Rowe also knew at once that the mysterious rat had to be a new species. After he and Esselstyn reunited, they “started making a list of the morphological characters that would be useful to include in the formal description.”

Beyond its distinctive flat nose and forward-facing nostrils, this shrew rat is also characterized by its long hind legs and large ears, not to mention some “curiously” long pubic hairs. The incisor teeth are especially long for a shrew rat, plus the creature lacks a coronoid process, which is a jaw muscle attachment that most mammals have. Back in the laboratory, after the scientists performed DNA testing, they determined that the hog-nosed rat was so genetically different that it merited its own genus.

The formal name for the hog-nosed rat is Hyorhinomys stuempkei. The researchers caught a total of five of them while in Sulawesi.

“I assume our capture rate is relative to the abundance,” Esselstyn notes.

Perhaps the volcanic mountain island of Sulawesi is rich in hog-nosed rats and other offbeat species–but what brought these mammal curators so far out to this remote place to begin with? As Esselstyn explains, he and Rowe were attracted to the isolated Central Indonesian area because they were interested “in documenting the diversity of shrews and rats that live on the island and investigating the relationships.” Some questions they set out to answer included how many species live in a particular place, the variation of species that live up and down mountains, and whether or not the animal communities are made up of species that are closely or distantly related.

Out in the actual field of this barely-researched island, trying to solve such proposed puzzles only ended up being more puzzling, due to the immense number of individual pieces.

“We went there wanting to answer fairly specific questions and then pretty quickly figured out we couldn’t answer any of those questions until we figured out how many species are actually there,” says Esselstyn, “and that’s going to keep us busy for a while.”

Additionally, several conditions play into making mammal-related discoveries, including what locals care to share. Previously, when Rowe and Esselstyn were in Sulawesi, their guides had caught a particular water rat and were debating about whether to expose it.

“Villagers knew that this species existed but scientists did not,” says Esselstyn, “that happens sometimes but it’s always a surprise when it does.”

The guides eventually did bring the Sulawesi water rat–which locals had used as a talisman for fire protection–to the attention of the researchers. Rowe and Esselstyn then observed several characteristics common to water rats and other semi-aquatic mammals, like short ears that don’t get cold in the water and fur that keeps liquid away from their skin.

What’s interesting, though, is the way that this particular species of water rat developed these traits independently. Esselstyn tells BTR that the Sulawesi water rat is actually more closely related to the hog-nosed rat than to the semi-aquatic rodents that live in New Guinea and Australia.

“It’s a good case of convergent evolution,” he notes.

The scientists plan to head back to the mountains of Sulawesi in January with the hopes of finding more clues to solve their mounting biological riddles.

“This is a pretty clear signal that there’s a lot we don’t know about small mammals in places like Sulawesi, for documentation of diversity,” explains Esselstyn.