Populations of isolated woodrat declining

It lurks in remote, rock crevices in one area of the Lehigh Gorge State Park. The small creature is a recluse, rarely seen during the day.

Its name alone causes many people to mistakenly disregard it as vermin – something to be exterminated.

The woodrat, unlike the common Norway rat, is native to Pennsylvania. At one time it inhabited 41 counties, but a variety of factors have caused populations to dwindle. Today, the woodrat is limited to a handful of counties and the species is listed as threatened in the state.

Most of the remaining woodrat numbers are concentrated in the southwestern and southeastern parts of the state. There are pockets of isolated populations scattered in the east and northcentral regions, including Lehigh Gorge State Park in Luzerne and Carbon counties.

According to Pennsylvania Game Commission biologist Kevin Wenner, the agency surveyed the northeast region for woodrat populations in 2005. Because the small, nocturnal mammals spend most of their time underground and are seldom seen, PGC technicians combed through remote rock crevices looking for crumbled leaves and twigs – the remnants of a woodrat food cache.

“We didn’t find any fresh activity, but before a site is ruled out we livetrap it,” Wenner said.

Last summer, the last ditch effort paid off at Lehigh Gorge when an adult lactating female woodrat was trapped.

In an effort to ensure the female woodrat’s survival and aid other woodrats in the location, Wenner and other PGC personnel lugged sacks of acorns to the remote rock outcrop for the woodrats. The acorns were dumped deep into the rock crevices where they would be found by any woodrats in the area. The agency will follow up their work with more livetrapping this August.

“The woodrat represents a unique habitat type, but the species is facing a big challenge in the northeast,” Wenner said. “The woodrats here are so far removed from other populations, and there’s no new genetics in this area. That warrants introducing new woodrats to the area to help the population.”

A three-year study, partially-funded by a Game Commission State Wildlife Grant, and being led by Indiana University of Pennsylvania (IUP), is attempting to shed light on the daily and seasonal movements of woodrats. Work will include radio-telemetry, DNA profiling and mark-recapture trapping.

Wenner said development and habitat fragmentation are likely the biggest culprits for the decline of the woodrat. The species can only travel a mile or two, and roads that intersperse through remote forested areas prevent woodrats from mixing with other populations.

The decline of the American chestnut tree is another factor because chestnuts were a primary food source for woodrats. There are also concerns that parasites and diseases from other species, like raccoons, may have an impact.

“Pennsylvania once had a solid woodrat population from Maryland to New York, but development and forest fragmentation have changed that,” said Cal Butchkoski, Game Commission small mammals biologist. “They now are extirpated in New York, and also Connecticut. It’s fair to say woodrats have been under siege for a long, long time.”

If the woodrat is going to make a comeback in the northeast, Wenner said it will most likely be limited to Lehigh Gorge State Park.

“Every other area in the northeast that historically had them has been ruled out,” he said. “Their potential to expand out of the state park is small because the forest has been so chopped up.