That naughty nutria
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Learn how a deceptively cute rodent from South America is wreaking havoc in the waterways of this country.
By Metro naturalist James Davis
From Argentina to Portland – a rodent's story
It was a dark and stormy night in the Louisiana marsh when the nutria got their big break. For more than two years, the large rodents had been living and multiplying in an "escape-proof" pen on Avery Island, home of tabasco king E. A. McIlheny, the man who had brought them to the United States from their native rivers of Argentina. When a hurricane hit the Gulf Coast in 1940, the rising waters flooded the pen and about 150 nutria paddled off to freedom in America and found nutria paradise – great habitat and very few predators. In just two months, some were found 65 miles away. Multiplying at a rodent's rate, they quickly populated a large area of Louisiana marsh.
Then the bizarre nutria scam of the 1950s greatly extended their range and secured their permanent status as an introduced animal alien. Unscrupulous nutria breeders fooled hundreds of Americans into buying breeding stock for producing nutria fur. There never was any real market for the fur, and when people realized they had been had, many set the animals free. Hence, nutria became well-established in a dozen states and reached a huge population. At first, the worst impact was thought to be the considerable damage they caused to rice and sugar cane crops in the south. Now it is clear that they also destroy marsh habitat and have a negative impact on native muskrats. Louisiana has spent millions of dollars over the last few years trying to develop an effective way to control nutria, including trying to make eating nutria meat popular. Louisiana marsh pig, anyone? How about gaucho burgers?
How to identify a nutria
As interesting as the nutria's history is, the first thing people usually ask when they see one is "How can you tell it's not a beaver or a muskrat?" No one book really covers this, so I have come up with my own system from the bits and pieces of information I've gathered and from years of observing all three species at Smith and Bybee Wetlands Natural Area. Yep, right in the middle of North Portland I've seen all three swimming around at the same time. Has anyone else?
Learn more about Smith and Bybee Wetlands Natural Area
If you see a beaver's tail, that takes care of that – it's totally unique. If you see a nutria or muskrat out of the water, its tail can help identify it as well. If the animal has what looks like a big, thick rat's tail, it's a nutria. The muskrat tail is similar, but it is not as big, has more hair and is flat vertically (not horizontally like a beaver's). Although hard to judge, overall size is another good clue. If the critter you see is smaller than a cat, it's a muskrat; if it's clearly bigger than a cat, it's a nutria.
When a muskrat swims, it thrashes its tail back and forth behind it and it looks like its head is being chased by a swimming snake. You don't see nutria tails very much when they swim, but if you do, part of it will just arch out of the water a bit and won't be moving much. I've never seen a beaver's tail when it was swimming, have you?
Most often all you see is a dark head moving through the water. What then? The nutria's head is the easiest to identify because it has several light areas while beaver and muskrat heads are a solid dark brown. Nutria have big, white whiskers, which are pretty obvious, and they often have lots of gray hair around their mouth, making them look like a hoary marmot or a man with a graying goatee. Perhaps the easiest field mark to see is a patch of lighter fur, usually tan to orange, at the base of the nutria's ears. Look at the shape of the head – a beaver's head will be big, chunky, squared-off and flat; a muskrat's head looks a lot more pointed and "ratty."
Chow time
Beaver and muskrat mean business when they swim – they just swim in a straight line toward where they are going. Nutria seem to wander around a lot and are the only one of this rodent trio that I have seen eating while floating. In the summer at Smith and Bybee Wetlands Natural Area, you can actually see nutria chowing down duckweed by swimming at the water's surface and stuffing plants into their open mouth with their paws.
See for yourself
For more information about about wildlife watching trips at Smith and Bybee Wetlands Natural Area, read the Metro GreenScene... More