Wednesday, February 3, 2010

Nutria In The Marsh

Photo: Steve Hillebrand/USFWS

Nutria are present in Beaver Creek Marsh.  They are a semi-aquatic rodent native to South America, similar in size to a beaver, but with a round tail instead of the beaver’s flattened tail.  You may see them swimming slowly in the creek, along marsh banks.  Nutria were introduced into the NW between 1899 and the 1930’s and were raised for pelts on more than 600 farms in Oregon and Washington.  In the 1950’s the market for nutria fur diminished and growing operations were closed, with animals being released or escaping into the wild.  Since adults have few predators (coyotes, dogs, and humans), nutria populations increased in wetlands and conflict with humans became common.  Nutria are primarily herbivorous and can consume 25% of their weight in a day.  Nutria are messy eaters on succulent, lower portions of plants and often leave large amounts of uneaten vegetation floating in the water.  They build dens in marsh banks.  These two habits can cause extensive damage to marsh vegetation and surrounding banks.

There are several signs of nutria that can be seen in the marsh.  At night, when nutria are primarily active, you can hear them call, sounding like a small child.  When we first heard them at night, we thought they were a bird and called them the “maa-birds”.  But one night I was walking on the road along the marsh and saw a nutria that was vocalizing.  Then it was clear who the “maa-bird” was.  We have seen large patches of bulrush cleared from the marsh by nutria.  This clearing created open water which has persisted for many years.  You can see mounds of dirt and vegetation piled along canals in the marsh and these are platforms that nutria rest and feed on.  

Digging by nutria to form dens in marsh banks occurs along the county road that runs through the marsh.  Occasionally, the bank forming the shoulder of the road collapses and you can see where a nutria den undermined the bank.  These holes in the shoulder can be a problem for vehicles that pull off to the side of the road.  

Posted by michael

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