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First Posted: 4/12/2013
Nick Forman wants to get to know the river otters in Northeastern Pennsylvania.
Every single one of them.
Forman, who is working toward his Masters degree in Wildlife and Fisheries Sciences at Penn State University, has spent the winter searching area streams and lakes for otter sign – namely latrines.
Latrines are areas along the water where otters deposit their scat. Forman said samples taken from the scat contain DNA which can be extracted to identify individual otters. The results can yield valuable information regarding population densities and abundance.
Extracting DNA samples from otter scat is part of a process called non-invasive genetic sampling. With a reclusive animal such as an otter, the process is one of the only sure ways to obtain population information.
“When you’re dealing with animals that are hard to spot or capture and tag or take blood samples, the non-invasive process allows you to monitor those animals without interfering with their daily routines,” Forman said. “Instead of trying to capture the animal and get DNA from a blood sample, you can pick it up through scat, similar to forensics.”
From January to early April, Forman searched for otter latrines in Luzerne, Wayne, Pike, Monroe, Carbon, Lackawanna and Susquehanna counties. He found otter signs in every county and collected 635 samples from approximately 130 latrines. Each site is revisited three times to create a capture history and population model.
For the next three months Forman will be in the lab extracting DNA from the samples. While it’s too early for results, Forman was surprised by the number of samples and variety of sites that he found in the region.
“I found sign in places where you wouldn’t expect to find an otter,” he said.
Top areas for latrine sites were places where the bank wasn’t eroded away and where white pines were present along the water. Forman surmised that otters are attracted to the white pines, and other coniferous cover for that matter, because the ground is sheltered from snow during the winter and they act as a landmark, appealing to the otter’s sense of smell.
To get a head start on the field work, Forman spoke to trappers, officials with the Pennsylvania Game Commission and private landowners to obtain leads on possible otter locations. He limited the field work to the winter months because the scat wouldn’t degrade quickly in the cold weather and otter populations are relatively stable, meaning there are no births occurring and little dispersal.
In Luzerne County, Forman found plenty of otter sign along the Nescopeck Creek and the Big and Little Wapwallopen creeks.
The research, which Forman said is a collaboration between Penn State University, assistant professor Dr. David Walter and the PGC, will last for two-and-a-half years.
Game Commission biologist Tom Hardisky said Forman’s findings will be incorporated into the otter management plan and the non-invasive genetic sampling technique is being watched very closely as a possibility to be used for other wildlife research.
“Finding a method to estimate densities without trapping otters has been a holdup for a long time,” Hardisky said. “The problem is you have to safely capture them and then re-capture them to collect any data. Using radio collars is very expensive and time-consuming as well.”
River otters in Pennsylvania are currently protected, but Hardisky said there is enough evidence from previous studies in the state to justify an otter trapping season on a limited basis. He said the management plan should be completed shortly and it’s possible that a proposal for a limited otter trapping season could be presented to the PGC board for the 2014-15 hunting and trapping season.
In the meantime, Forman will return to the area next winter to collect more DNA samples and get an idea of just how many individual otters are present on the northeast.