You Otter Know

By Jason Beale, Abbott’s Mill Nature Center Manager

Many mammals “see” the world through their sense of smell, much more than humans.  Despite our use of perfumes and colognes in our mating rituals, we generally refrain from advertising or marking our territories through the use of smelly bodily substances (urine, feces, etc.)  However, for many mammals, especially those with large territories or low population densities, scent marking is extremely important.  In this case, we’ll look at some Northern River Otter scent marks.

 

Scent mounds are usually placed at or near prominent landmarks, natural or otherwise.  This dock along Abbott's Pond is a reliable spot to look for River Otter and American Beaver sign throughout the year
Scent mounds are usually placed at or near prominent landmarks, natural or otherwise. This dock along Abbott's Pond is a reliable spot to look for River Otter and American Beaver sign throughout the year

We encountered the above leaf and debris mounds during our weekly Thursday walk on January 7th.  You can see the scrapes where the vegetation was removed to form the loose mounds.  Close inspection shows piles of scat, featuring numerous fish scales.

Otter scats vary in shape, but are usually loose piles of fish scale
Otter scats vary in shape, but are usually loose piles of fish scale

Otters are members of the Mustelidae (Weasel family) which are closely related to the Mephitidae (Skunk family).  While the skunks are renowned for their highly developed anal scent glands, weasels also possess them and may use them when disturbed and to mark territories.  The following photo shows the yellowish-white secretions that Otters often mark sites with.

Otter secretions look very similar to the American Beaver's castoreum deposits which they use to mark their own territories.  Beaver mounds are generally constructed from mud and aquatic debris and can be quite large after multiple uses.

Otter secretions look similar to the American Beaver’s castoreum deposits.  Beaver scent mounds are generally constructed from mud and aquatic debris and can be quite large after multiple uses, up to 2′ high.  As both species use the same habitats, look for other clues to aid in identification.

Scent mound in front.  Note the scraped area beyond.
Scent mound in front. Note the scraped area in the upper left.

Have fun exploring outdoors and trying to make “scents” out of what’s going on.  Feel free to attend our weekly, free Thursday birding and nature walk at Abbott’s Mill Nature Center in Milford.  We meet at 8:00 a.m.

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