The first hint that there was a problem with Pennsylvania’s muskrat population surfaced nearly 20 years ago.
In 2008, I spoke to legendary fur buyer and lure maker Nick Wyshinski, who operated a trapping supply business in Columbia County for more than 50 years. Back then, Nick handled more furs than anyone I knew, and he dealt with a lot of trappers. I asked him about the disappearance of muskrats, and Nick said the first time he heard of a problem was in 2001, when another trapper told him something wasn’t right.
“I didn’t believe him because at that time the muskrats were coming into the shop pretty good,” Wyshinski said.
In 2008, however, Wyshinski was firmly convinced that there was a problem with muskrats, but he wasn’t sure of a cause.
To find out more, I turned to another veteran trapper who also happened to be a respected biologist – Tom Hardisky.
Hardisky was a biologist with the Pennsylvania Game Commission and he was studying the muskrat issue very closely. He had a unique perspective on the matter as both a scientist and trapper. During our first conversation in 2008, Hardisky had a theory about the muskrat decline, but he had to rule out other factors first.
He wasn’t quite ready to stake his reputation on it at the time, but Hardisky believed disease and contamination weren’t causing muskrats to plummet. He suspected the cause to be environmental.
Could it be, Hardisky suggested, that improvements to water quality were actually hurting muskrats?
It was a theory that merited a closer look, Hardisky told me in 2008, and he continued to put the pieces together over the next several years as I documented his progress.
In 2010, Hardisky ruled out disease and contamination from heavy metals and pesticides. But he didn’t rule out predation, and that led Hardisky to zero in on another factor.
“The cause of high predation goes back to habitat,” Hardisky said at the time. “It all has the symptoms of a bigger problem – environmental changes. One of those changes is cleaner water.”
In the past, when runoff from farms and residential areas was discharged directly into waterways, the increased nutrient load caused vegetation along streams and rivers to flourish. In turn, muskrats benefited from a lush food source and thick cover.
Less nutrients entering the water means less of the elements – nitrogen and phosphorous among others – that boost plant growth.
Hardisky was on to something, and in 2011 I re-visited the issue again. This time Hardisky reported on the results of a recently completed PGC study examining nearly 9,000 muskrat pelts to determine any red flags with reproduction or recruitment. The findings showed that the age ratio between juvenile and adult muskrats (eight juveniles to three adults) was similar to data collected 30 years ago when muskrat populations were much higher. Because adults didn’t show an increase in the population, reproductive and recruitment issues were ruled out as reasons for the decline.
“That’s important because it helps us focus on other areas,” Hardisky said back then.
And again, the focus kept falling on improvements to water quality.
Hardisky continued to study the muskrat decline in Pennsylvania and across the northeastern United States. As the years went by, the data kept ruling out other potential causes.
Disease is an issue when populations are high, he said, so that wasn’t a factor. Parasite problems in muskrats are generally dictated by age, gender and habitat conditions and it isn’t a significant source of mortality, he added.
However, there was evidence of high predation on muskrats, and that served as a link to another problem. Hardisky believed that predation was merely a symptom in the decline of muskrats, and it was important to focus on the root cause.
In 2017, after years of studies, research and ruling out other factors, Hardisky was finally ready to label clean water as the root cause behind the muskrat decline. It’s a similar scenario to what happened to wild pheasants in Pennsylvania when clean farming practices resulted in less brushy areas and more wide open fields.
The cleaner things are, the less inviting it is for some species whether it’s pheasants on a farm or muskrats in a swamp.
In the case of the muskrat, there was no easy fix. After all, how does one advocate for dirty water?
“The importance of managing nutrient loads in water systems to benefit muskrats should not be underestimated. The lack of nutrient flushing may be the root cause of the muskrat decline in Pennsylvania and throughout its North American range,” Hardisky said in 2017.
Still, Hardisky was undeterred and he wanted to examine the feasibility of managing smaller wetlands for muskrats with intentional – yet limited – discharges of nutrients into the water.
Unfortunately, Hardisky passed away unexpectedly in 2018 and never had the chance to seek a solution for the muskrat decline.
He did, however, leave us with an answer and in my final interview with him, Hardisky predicted what the future may hold for muskrats. As streams and rivers continue to flow cleaner, he said, muskrats may one day become strictly a farmland species, inhabiting those areas where some level of nutrients enter the water.
“That’s probably what we’ll have to live with,” Hardisky said in 2018. “I’m just hoping we can hang on to what we have.”
- This story originally appeared in PA Outdoor News
Fantastic piece Tom ~ Well done!