Published: June 6, 2019

3 Questions with a Scientist: Hopping Rats

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These two new species hop like tiny kangaroos, snack on earthworms, and live in incredibly biodiverse sky islands.

Mammals curator Larry Heaney and collaborators in the Philippines identified two new species of tweezer-beaked hopping rats (that are nothing like our Chicago rats). Heaney has been studying mammals in the high-elevation forests of the Philippines since 1981.

A man stands in the middle of a tropical forest, with bright green plants and mosses surrounding him. He holds a walking stick and poses for the camera.

“Sky islands” sound like something from science fiction. What are they, and what’s it like doing fieldwork there?

It’s an island of habitat: these are places up in the mountains where the environment is very different from lower elevations. Lots of plants and animals increase in biodiversity when you go up in elevation. That’s true for Rhynchomys rats in the mountains of the Philippines. There’s a strong correlation between the height of the mountain and the number of native small mammal species.

In these sky islands or cloud forests of the Philippines, the feeling is very similar to what you would experience if you were out in the Olympic Peninsula of Washington State or at the top of the Smoky Mountains. It’s cool, wet, and foggy. It’s very quiet except for bird calls. We have a rule in camp that you have to use headphones if you want to listen to music or the news. It’s very focused on getting the work done, and I enjoy the peacefulness.

We build our camps on the edge of the mountain, often on very steep slopes. For our tents, we have to build platforms to sleep on so that we’re not rolling down the hill. Food has to be stuff that’s transported easily and is fairly robust. We eat simply but well; I have a big bowl of oatmeal for breakfast. There’s a lot of rice, canned fish, and canned meat. SPAM is considered a delicacy in camp.

The view from a mountaintop, with nearby trees in the foreground that have spiral branches and green and orange leaves. There are farther mountain ridges in the background, covered in forest and partially obscured by cloud.

Mount Mingan, where one of the two newly identified hopping rats lives.

These tweezer-beaked hopping rats seem pretty different from our Chicago rats. True?

The rats in Chicago and other cities and towns around the US are not native, they were brought here accidentally. They’ve been evolving to get good at living with and off of people for thousands of years. And they stink to high heaven! They’re very, very different from these animals in the Philippines. Rhynchomys, the tweezer-beaked rats, aren’t aggressive and they stay as far away from people as they can get. They’re also docile and very cute.

And the Rhynchomys hop; they’re unusual in their locomotion. They make trails in the mossy ground and patrol those trails for earthworms day and night. If you’ve ever tried to catch an earthworm, maybe as a kid, you know that they are very difficult to pull out of the ground. If it feels a vibration, it zips back into its hole. These hopping rats are trying to be very quiet and move quickly. When they find an earthworm, they pounce.

Side-by-side illustrations of two rats, in similar positions perched on their hind legs. The rat on the left has darker gray fur, and the one on the right is more light brown in color. They both have long, narrow snouts.

Illustrations of the two new species, Rhynchomys labo (left) and Rhynchomys mingan, named for the mountains where they live: Mount Labo and Mount Mingan.

Velizar Simeonovski

What’s it like doing research in the same place for many years?

All along, this has been a fully collaborative project with colleagues in the Philippines. We do fieldwork together, and when possible, they come and do work here at the Field Museum. There are some people I started out with 30 years ago, and now I’m working with their students or even their students’ students. It’s a generational relationship that's very enjoyable and productive.

The Philippines’ Department of Environment and Natural Resources has done a lot to make it possible for us to do our work. It’s not just providing the permits to allow us to do fieldwork there. They use our data and discoveries like these two new species to officially protect natural areas. The “old growth” in the Philippines—mature or undisturbed forests—is down to about six percent of what it once was because of logging, most intensively up through the 1980s. But the good news is that newer, secondary growth is steadily increasing. I see the Philippines’ conservation efforts as a success story in progress.

Negaunee Curator of Mammals Larry Heaney studies species in island ecosystems, particularly on Luzon Island in the Philippines. He co-authored a paper with American and Filipino authors on two new species of hopping rat in the Journal of Mammalogy: "Two new species of shrew-rats from Luzon Island, Philippines."