Active online survey focused on decline in muskrat numbers offers 'phenomenal data' according to PGC biologist, including numerous theories

Results to an online survey developed by the Middle Susquehanna Riverkeeper Association focused on finding trends and answers for potentially declining muskrat numbers across the state continue to highlight some of the same patterns seen by biologists.

The survey is still active and more feedback from trappers and other outdoor enthusiasts is encouraged.

So far, 91 percent of those surveyed indicated that water quality in the areas they spend time outdoors has either stayed the same or noticeably improved over the past decade. However, during the same time, 82 percent of those surveyed indicated either a population about the same or declining – 27 percent of all who were surveyed suggested they’ve noticed a drastic decline in the species over the past 10 years.

“What’s so interesting (and I’ve only made it through the first half) is that there’s a huge variety of reasons mentioned for decline, and not a single one that keeps coming up over and over,” said Pennsylvania Game Commission biologist and mammals specialist Thomas Keller. “This is obviously reflective of what we currently know (which is practically nothing) about the decline), but have many of the same thoughts.”

Among those suggested reasons for potential decline provided by survey takers are construction projects – as big as the Central Susquehanna Valley Thruway effort to smaller, more isolated projects such as a pipeline being placed in one individual’s land.

Other potential reasons for decline included a noticeable increase in predators, an upwards trend in flood events that impact the habitats drastically, a noticeable reduction in cattails (a favorite food item for muskrats) and some drought conditions.

Overall, so far, Keller suggested the info collected in the online survey created by the Middle Susquehanna Riverkeeper Association offers “phenomenal data.”

Most of those who have taken the survey so far are involved with trapping and collectively indicated spending considerable time outdoors in 17 of the state’s 22 designated wildlife management areas (73 percent). Of those who trap, an overwhelming majority (90.9 percent) suggested they primarily trap along streams. Other habitats with high engagement have included forests/wooded areas, marshes and rivers.

The consensus shared a definite concern for the species.

“The muskrat population is definitely on the decline,” shared one survey-taker. “Every year I see more and more blue herons on streams and ponds that typically had high muskrat levels. Often see old sign on opening day with no rats or fresh sign.”

Another suggested two main reasons for their decline: “1. Mink are common now and kill muskrats efficiently. 2. Small streams have been blown out by storms, leaving poor habitat for muskrats.”

“As someone raised on a fourth-generation family farm and who has heard from old trappers (about) the dramatic muskrat decline in the area, I believe the ‘disease’ angle is completely wrong,” said another survey-taker. “I believe the fertilizer and herbicides being used by farmers are entering the waterways and somehow affecting the plant life the muskrats need to survive, which then in turn causes them to be unable to survive in these waterways.”

“I do not have many as 15 years ago,” agreed another survey-taker. “I let them clean out the cattails and so they come and visit but then leave. I notice around that people are getting rid of their cattails on their properties. No cattails (means) no food for the muskrats.”

A different survey-taker mentioned communicating with former PA Game Commission wildlife biologist Tom Hardisky about the issue.

“Tom was doing a muskrat study in Pennsylvania. He was also in contact with other state Wildlife agencies (that were) conducting similar studies. Tom indicated to me before his study was complete that muskrats were found in water that was not cleaned up. A restored stream or river had zero to low population of muskrat,” he said. “Tom was leaning that 'clean water' may have something to do with the disappearance of muskrats. Unfortunately, Tom passed away before his sturdy was complete.”

The online survey is still available for more people to provide feedback, which is being shared with the game commission and other partnering groups in an effort to better understand the issue.

“Overall, in the past several decades, water quality has definitely improved as a whole and we have heard consistent reports of a noticeable increase in most aquatic mammal species – from mink to otters and everything in between,” said Middle Susquehanna Riverkeeper John Zaktansky. “So it is definitely odd to see such a large downward trend in the muskrat, and we really want to better pinpoint reasons behind that.

“Is it possible that an increase in emerging contaminants such as microplastics, PFAS and pharmaceuticals are somehow playing a role? Perhaps the muskrats are more sensitive to certain medications that pass through people and eventually into the water table. Things like birth control usage can increase estrogen levels in nearby waterways and maybe that is impacting muskrat reproduction more than it does other aquatic mammal species?” 

You can offer your own feedback through the online survey.