Wednesday, March 2, 2011

Aquatic Wonders

Nature Watch

By Susan Thurn,
Cable Natural History Museum

I owe an apology to a gray truck. It was over the weekend, while driving home from Hayward, that I spotted a river otter along the Namekagon River. I turned on the blinkers, braked quickly, and quickly pulled over to the side of the road, perhaps angering the truck behind me. It was irresistible, the opportunity to view an animal that is so amazing and enjoyable, watching them bound across the ice. I had to stop and share the observations with my family!

River otters are part of the weasel family. Comfortable in water, they have a tapered body that streamlines them for successful swimming, webbed feet, sharp hearing and scent abilities, and a sense of touch that gives them good dexterity. Their lungs are complex, with a larger right lung and different lobes in both sides, designed for aquatic breathing. Their airway is also shorter to improve breathing for this diving mammal. Even their mouth is designed well, with sharp canines for biting their prey, and large molars for breaking the hard shells of clams and other mollusks. River otters can dive down to 60 feet deep, can swim underwater for up to four minutes, and move almost 1200 feet underwater. One last amazing adaptation is that they dry themselves by rubbing on the ground, which also maintains the insulation value of their fur.

On land, otters can walk, bound, or slide, which is part of what makes them seem so playful, and what my family observed this otter doing. They slide across the snow or ice, mud banks and vegetated slopes, quickening their pace in efficient travel. They will excavate beaver dams to access water and in winter, use any opening in the ice.

Where do they sleep? Otters create a den or hole at the water’s edge, with many openings that allow them to enter or exit the water in several places. These exits also give them greater access to their prey.
When hunting, river otters will lunge quickly from an ambush to catch their food, or chase after prey. What is on their menu? They will eat small fish while floating at the surface, but take larger fish to the shore for their dining pleasure. Crayfish is another favorite food, according to scat that has been observed. They will also eat frogs, clams, mussels and snails, fruit, reptiles, amphibians, small mammals, and aquatic insects. They even eat plants and birds.

The river otter is more social than most animals in the weasel family. They fish together. They are playful, chasing or wrestling with each other. They will play catch and release with live prey. They communicate with chirping sounds, grunts, or even high pitched screams when mating or fighting.

I envy those who live along the water and have the occasional or frequent observations of this lively and fascinating mammal. Please post your own otter stories at the Museum’s blogspot listed below to share the wonder of this amazing creature that lives in our own back yards.

For over 42 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and exhibit, “In a New Light” photographic exhibit focused on the St. Croix National Scenic Riverway. Find it in Cable at 13470 County Highway M. Also discover us on the web at, on Facebook, or at our blogspot, to learn more about our exhibits and programs.

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