River Otter
Drawing of a river otter from Canva.
As likely the most elusive aquatic mammal in Pennsylvania, the North American River Otter (Lontra canadensis) is seldom seen but a treasured member of our aquatic systems. With a range expanding across the majority of North America, populations of river otters are stable or increasing throughout Pennsylvania. Though, not long ago, it was a very different story.
Before the 20 th century, a deadly combination of overharvesting, poor water quality, and habitat encroachment by humans resulted in a 75 percent decrease in North American River Otter populations. In Pennsylvania, river otters were never fully extirpated, though their populations were greatly reduced; water pollution from industrial and sewage waste and strip mine runoff made many of our streams, lakes, and rivers unsuitable for aquatic life. Thanks to strict anti-pollution laws and consequently improved habitat quality, reintroduction efforts, trapping regulations, and legal protection, river otter populations recovered during the late 1900s.
Nowadays, river otters are found in all of Pennsylvania’s major river systems and are only missing from watersheds with poor water quality. The presence of river otters can indicate the quality of our waters. River otters maintain an omnivorous diet, including fish (carp, trout, minnows, suckers), mussels, snails, crayfish, snakes, turtles, and frogs. Otters will also eat insects, worms, aquatic plants, roots, and even small birds and mammals. Pristine water which can sustain various life forms is thus essential for river otters, whose diets are comprised mainly of aquatic life.
River otters are skilled swimmers, with magnificently effective physiological adaptations. Otters can dive approximately 35 to 50 feet, swim about a quarter-mile without coming up for air, reach speeds of about 7 mph, and stay underwater for about four minutes at a time. When underwater, valve-like structures seal their ears and nose and a reduced pulse allows them to stay submerged for a long period of time. Otters have an acute sense of hearing, keen sense of smell, and excellent underwater sight. Long whickers act as sensors when searching for food in murky water. With wide, webbed feet, two layers of fur, and an insulating fat layer, otters are built for life in the water. River otters rarely fall prey to other animals, due to their vigilance and agility both in water and on land. As a member of the weasel family, otters also have anal musk glands which produce a powerful odor when frightened or to purposefully mark their scent.
Otters are famously playful and curious creatures. By wrestling, playing with food, sticks, and stones, or sliding around on the snow, river otters can socialize and learn hunting techniques. These elusive creatures are not often seen by humans, but their role as a top aquatic predator and an indicator species for the quality of our waterways makes their presence invaluable. Those who are lucky enough to spot them in the wild are unlikely to forget it.
To continue reading about the North American River Otter, visit https://www.pgc.pa.gov/Education/WildlifeNotesIndex/Pages/RiverOtter.aspx
Written by Faith Forry — April 7, 2021
