Woodrats: A Disappearing Sign of Healthy Forests

  • A woodrat caught in Latrobe, Pa., where IUP scientests are tracking population size. Photo: Jennifer Szweda Jordan

  • Researchers trek into the woods to document to reclusive woodrat. Photo: Jennifer Szweda Jordan

  • This woodrat was captured to be weighed and documented before being released. Photo: Jennifer Szweda Jordan

  • The Allegheny woodrat prefers rocky outcrops common in Appalachian states. Photo: Jennifer Szweda Jordan

April 19, 2013

Jen Hoffman was worried about a new mom that might be trapped in the woods. She hiked swiftly up a hill to get to her as fast as possible. The mom—is an Allegheny woodrat, a species whose population is on the decline.

“It's not like the rat you're going to have in your garage,” Hoffman said. Many of the Allegheny woodrats keep their soft grey coats clean and sport dark brown stripes under their fluffy tails. 

Early morning in a forest near Latrobe, Pa., Hoffman was one of a team of researchers trapping and examining woodrats. Her colleague Joe Duchamp, assistant professor of biology at Indiana University of Pennsylvania, peered into a cage where the lactating female was trapped.

“If you had a squirrel in here, it'd be going crazy right now,” Duchamp said, as he coaxed the rat into a pillowcase to be weighed.

Other than researchers, cavers are the most likely humans to spot Allegheny woodrats because the animals are nocturnal and live in remote spots, but also because their populations are disappearing.

In 2009, there were about 50 groupings of rat populations in Pennsylvania that had vanished—mostly in Central and Eastern PA. More have disappeared in the last several years. Population declines have been occurring in the Northeast and also the far west range for the species—southern Indiana.

They are disappearing in part because widened roads, mining operations, and homes and farms have been developed between their territories, preventing the species' spread. It makes them prone to unhealthy inbreeding. And there are other problems.

“If you look at the species range, it matches the American chestnut, so that was probably an important food,” Duchamp said. “The chestnut pretty much disappeared. More recently, gypsy moths have taken out some oak species. That’s contributed to some of the loss of food. There's a third factor—raccoon roundworm.”

If the Allegheny woodrats contract raccoon roundworm, a parasitic worm that lives in the intestine, it destroys their nervous systems.

The woodrats are an important link in the ecosystem—a food to predators like owls. Plus, the items they bring from forests into caves allow insects and fish there to survive. Perhaps the woodrat's most significant job, though, is that it’s an important indicator species—a sign of forest health. While there are many ways to evaluate the trees, plants, and other parts of this woodsy ecosystem, the woodrat is one of the best judges.

“The proof that it is quality forest habitat is that the wildlife that lives there can actually live there. If the wildlife can't survive there, there's something else missing,” said Duchamp.

Based on that, IUP professor Jeff Larkin said that it’s clear there’s a lot missing now.

“In the worst case situation, and I fear that in many parts of Pennsylvania we're actually at this point now,” Larkin said in 2009. “We will actually have to move individuals from one habitat site to another.”

While researchers have not yet moved the woodrats, there are several locations where doing so appears increasingly necessary. In a few weeks, the researchers will also be conducting additional studies about genetics and the effects of inbreeding. Their inital results are currently available.

Conservation coverage is funded by the Richard King Mellon Foundation. The series features interesting animals, plants, and habitats in our region and considers how they're faring in a changing environment.

This story was first published August 12, 2009.

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Transcript

We've come to the last feature about a creature in our series on endangered and threatened Pennsylvania wildlife. It may be an unlikely critter for you to care about, but it's an important indicator of forest health. The Allegheny Front's Jennifer Szweda Jordan reports.

Nat. Sound Hiking

JORDAN: Jen Hoffman is worried about a new mom that might be trapped in the woods. Hoffman's swiftly hiking up a hill to get to her as fast as possible. The mom -- is an Allegheny Woodrat. Don't grimace now -- as Hoffman says many people do when she tells them she studies the species.

HOFFMAN: It's not like the rat you're going to have in your garage. They're not going to be anywhere near human habitation. You'll see. They're sweet.

JORDAN: In the early morning in a forest near Latrobe in western PA, Hoffman's one of a team of researchers trapping and examining woodrats. And, it turns out, they are kind of sweet. I'm not normally a fan of rats, but as Hoffmann points out, I'm probably thinking of the invasive and aggressive Norway rat. But many of the Allegheny woodrats keep their soft grey coats clean and dark brown stripes under their fluffy tails. When Indiana University of Pennsylvania Assistant Professor Joe Duchamp guides me to the cage where the lactating female is trapped inside, I get gaga like I do over puppies and babies.

JORDAN (IN FOREST): OH MY GOODNESS

JORDAN: Duchamp puffs to get her to run to one end of the trap.
Nat. Sound Duchamp puffing breath
JORDAN: He slips a pillowcase over the other end and scoots her inside the bag. He weighs and examines her identity based on tags they've earlier placed in her ears.


DUCHAMP: These are nice to work with for rodents -- if you had a squirrel in here, it'd be going crazy right now.


DUCHAMP: 405 with the bag.


JORDAN: Minus the pillowcase, the rat's 290 grams -- about 10 ounces. Duchamp lets the rat go, and she scurries away on rubbery little footpads, zipping up and over rocks before I can snap a picture. This is why you might walk through these same woods regularly and never see a woodrat. Besides being quick, they're nocturnal. And they definitely don't take the beaten path. They live around hard-to-reach lunar landscapes of jutting rock ledges and dunes of disintegrated sandstone. Opossums, salamanders and turtles are some of their neighbors we see today. And that's not all.


Other than researchers, though, cavers are the most likely humans to spot the rats. The little guys sometimes climb into their backpacks for a snack. But another reason you might not see the rats is because they're on the decline in Pennsylvania and other states.


DUCHAMP: They go up to the Northeast as far as their species range. All the way as far west into southern Indiana. They go far south into Georgia. They pretty much follow the Appalachian range. Population declines have been occurring in the Northeast and also the far west.


JORDAN: They're disappearing in part because widened roads, mining operations, and homes and farms have been developed between their territories so they can't spread out. It makes them prone to unhealthy inbreeding. And there are other problems.


DUCHAMP: If you look at the species range, it matches the American chestnut, so that was probably an important food. The chestnut pretty much disappeared. More recently, gypsy moths have taken out some oak species. There's a third factor -- raccoon roundworm.


JORDAN: Woodrats are quite literally packrats. They pick up food and store it in caches in caves. But they also store things they can't use, like spent shell casings from hunters. Or things that can even kill them ñ like raccoon feces that contain edible seeds. If the rats contract the raccoon roundworm, it destroys their nervous systems.


There are now about 50 groupings of rat populations in Pennsylvania that have vanished -- mostly in central and eastern PA. So the commonwealth is spending 99-thousand dollars for three years of study on the woodrat. It's an effort to examine and stop the decline that's taken the woodrat completely off the map in some states.


Duchamp and colleague Jeff Larkin are part of a big push to keep the Allegheny Woodrat off the federal endangered species list.


LARKIN: We know that listing species is a costly endeavor ñ- there's costliness to taxpayers, and industry, and loss of economic potential because you might have a particular species on a property.


JORDAN: Besides the financial concerns, the woodrat's an important link in the ecosystem -- a food to predators like owls. And the items they bring from forests into caves allow cave insects and fish to survive. And the woodrat is an important indicator species ñ- a sign of forest health. While there are many ways to evaluate the trees, plants, and other parts of this woodsy ecosystem, the woodrat is one of the best judges.


DUCHAMP: We can look at maps and see where the forests are. The proof is that the wildlife that lives there can actually live there. If the wildlife can't survive there, there's something else missing.


JORDAN: Larkin says keeping forests intact and connected is the best option for woodrat survival.


LARKIN: In the worst case situation, and I fear that in many parts of Pennsylvania we're actually at this point now, we will actually have to move individuals from one habitat site to another.


JORDAN: Researchers are also experimenting with giving the rats acorns, wheat, and oats in years when the forest doesn't provide as much food. That keeps the females healthy and able to reproduce earlier in the season -- about two litters of pups a year.


Today's a good day for the researchers and the rats.


Nat. Sound Rat's SQUEAK


JORDAN: The trapped ones are all healthy. To get a picture of the genetic health of the greater population, Hoffman takes a little genetic sampling from the ears.


HOFFMAN AND DUCHAMP: Give him a squeeze ñ CLIP. Perfect. No blood? No blood. We try to give them a nice little squeeze as we do the more invasive stuff. Kinda how theyíll pinch your arm when they'll give you a vaccination.


JORDAN: Researchers are hoping this temporary pain for the woodrat will help the fuzzy little creatures survive for years in the forests -- even though many of us will never see them.


For The Allegheny Front, I'm Jennifer Szweda Jordan.