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New Rodent Discovery Another Piece in Evolutionary Puzzle

Most people tend to avoid rats like the plague, but not so for Dr. Jake Esselstyn and his colleague Dr. Kevin Rowe. They not only pursue rats in the wild - they're discovering new species.">Hog-Nosed Rat from">WRKF News on Vimeo.

When asked about their discoveries, Dr. Esselstyn had a hard time keeping track: "(We discovered) one new rat in 2014 I believe, another rat in 2012 – oh no, two other rats in 2015, or 2014, that I forgot about…So, several!”

Dr. Jake Esselstyn is Curator of Mammals at LSU’s Museum of Natural Science, and his colleague Dr. Kevin Rowe is Senior Curator of mammals at Museum Victoria in Melbourne, Australia.

Since 2010 the pair has worked with Indonesian scientist, Dr. Anang Achmadi (Curator of Mammals at Museum Zoologicum Bogoriense, Research Center for Biology at the Indonesian Institute of Sciences) to study the diversification of rats from Asia to Australia.

Their main focus: the island of Sulawesi, in Indonesia.

“Sulawesi is a remarkable place geographically," said Dr. Rowe. "It’s really like four continents coming together but not quite connected, (and) all isolated by deep ocean channels.”

And as for the rats? Well, Dr. Rowe said, "they’re the only non-flying mammal to make the crossing from Asia to Australia besides humans.”

This makes Sulawesi a continental crossroads. Meaning, they’re discovering new endemic rat species on Sulawesi that’ve been isolated for millions of years. In fact, almost 86% of all mammals on Sulawesi aren't found anywhere else.

And their discoveries have been pretty amazing. Their latest species to be described and published in the Journal of Mammalogy is the hog-nosed rat, Hyorhinomys stuempkei, which they discovered in 2013.

With a nose like a pig and long tusk-like teeth, Dr. Esselstyn said Hyorhinomys is not your average rat.

“They have long hind limbs" said Esselstyn, "so we think they hop. The claws on their hands are more like fingernails than they are like claws, and we’re not sure why that is.”

But, Dr. Rowe said, that’s why they’re on Sulawesi: to find answers to questions like this, and not just to find new rats for the sake of discovery.  

“It’s about trying to understand" said Rowe, "what are the environmental requirements for species on this island and how isolation on an island allows evolution.”

Both Esselstyn and Rowe agree, though, that Hyrorhinomys is only the latest. They predict that there will be more rats to come from the island of Sulawesi.