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Otter scat may be the key to counting otters

Monday, August 24, 2009 | 12:01 a.m. CDT
University of Missouri master's degree candidate Rebecca Mowry holds an electrophoresis gel rig in her lab in Tucker Hall. Mowry is conducting research to gauge Missouri's river otter population by extracting DNA from samples of otter scat.

COLUMBIA — To the hum of laboratory machines, Rebecca Mowry pours a steaming beaker of liquid gel into a pristine plastic plate to prepare a DNA test. You would never know that she is working with poop.

How to count river otters — which are nocturnal, secretive, intelligent and hard to trap — is a question that has intrigued biologists with the Missouri Department of Conservation since they began reintroducing otters to state streams in the early 1980s. After more than 20 years and much controversy, they still haven’t come up with a good answer.

This is where otter poop and Mowry, 25, a master’s student in MU’s fisheries and wildlife program, come together. Scat, a term biologists use to describe animal feces, is something every animal leaves behind, and in the case of otters it is relatively easy to find.

Mowry's previous jobs have included trapping and radio-collaring wolves in Mexico and bobcats in California. Working with otters, another carnivorous mammal, was right up her lane, but she almost didn’t take the job.

She was worried about losing time in the field, but she wasn't worried about working with scat. “It was hard at first, because this is a lab job,” Mowry said.

Mowry is trying to develop a method for determining how many otters are in Missouri, but she has spent only one day on the rivers where the playful critters live.

“I have never seen an otter in Missouri,” Mowry said. Yet she hopes to be able to tell how many individuals are on a specific stretch of river, what sex they are, how far they travel and even some details about their social behavior.

Instead of counting otters in the field, she is extracting DNA from the scat collected by a team of scientists hired by the conservation department.

DNA extraction has become a common practice for wildlife biologists seeking to understand more about a species, said Jeff Beringer, a resource scientist for the conservation department.

The conservation department over 11 years, beginning in 1982, released 845 otters into Missouri waterways, spending $1.5 million in the process. The department stopped releasing otters into Missouri rivers in 1993 because of the program's success. Since the reintroduction, otters have taken off, and current population estimates range from 11,000 to 18,000. The public’s reception of the animals has been mixed.

Some are thrilled with the return of an animal that had once been common in the state but whose population had been reduced to only a handful of animals by 1936.

Others, however, are angry about otters decimating fish populations in streams and, particularly, in stocked farm ponds. A small population of otters can wipe out fish populations in a matter of days, or even hours.

Debo McKinney lived most of his life on the Big Piney River but wanted to retire on the Roubidoux River because of its renowned fishing. After years of searching for the right property, he found one.

Then the otters were reintroduced. Now, he says it has some of the worst fishing in the state.

"I suppose it's all right," McKinney said about Mowry's project. "They can tell them how many's there, but that's not going to control them."

Beringer, however, said "the jury is still out on when otters affect fish numbers. I think they do in some situations, but in others they don’t.”

Beringer believes the problem is simply a lack of information. “There’s probably more we don’t know than we know.”

Without a solid understanding of otter populations, it's difficult to know how they affect fish populations. That's why the Missouri Department of Conservation is funding Mowry’s research.

Last year the department gave MU $40,000 to conduct the research, and it already has approved another $30,000 for next year. That money goes toward lab expenses, a stipend for Mowry and a tuition waiver for Mowry.

MU has provided lab facilities, and it gave Mowry an intern through the Life Sciences Undergraduate Research Opportunities Program. It also pays 15 percent of Assistant Professor Lori Eggert’s time to advise on the project.

Conservation biologists now count otter latrines and the number of scat piles in each latrine to extrapolate relative numbers of otters in different rivers. For example if River A has 23 scats per river mile and River B has 60 scats per mile, then River B has more than twice as many otters than River A. But this doesn’t give biologists a solid number.

Mowry is extracting DNA from more than 1,400 samples of scat collected by conservation researchers. The team worked on eight different rivers in southern Missouri, including the Roubidoux, Current, Courtois, Maries, Big Piney, West Piney and Niangua rivers, and the Osage Fork of the Gasconade River.

Through multiple steps in the lab, Mowry first extracts and then genotypes DNA from the scat. The genotypes allow her to identify individual otters. Every sample is labeled with its original location, so Mowry will determine how many individuals used each latrine and how far those individuals travel.

“You can tell a lot about an animal with very little contact with the animals,” Mowry said.

When she is done she will know how many latrines, how many scat piles and how many individual otters were in the area. From there, she plans to develop a model that will allow biologists to correlate latrine and population numbers.

Mowry expects to have numbers by the end of the September. She began her research in fall 2008 and has until May to come up with a model and write her thesis.

Wearing flip flops, shorts, an MU T-shirt and her hair in ponytail, Mowry seems to have adjusted to her indoor environment as she hurries back and forth finishing preparations for a test. She has come to appreciate the indoor work, noting that the fieldwork for this project, which was done by another team, was done in January. The one day she went out with the team she fell in the partially frozen river.

But mostly it is the promise of this method that has lured her into the new environment. The same techniques could be used on any biological material from any species.

“The rest of the lab works on elephants and wild horses, but the techniques are mostly the same,” Mowry said.

Reactions to her work with animal scat vary. “In general people are more surprised you can get DNA from it,” Mowry said. “Some people think it's gross.”


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Comments

Y K August 24, 2009 | 10:09 a.m.

Good Luck to you.

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