One of the most beloved critters of Putah Creek is the North American river otter. This charismatic, semiaquatic mammal has been spotted all along Putah Creek, from the Putah Creek State Wildlife Area below Lake Berryessa to the Yolo Bypass. These furry friends are not just found along Putah Creek, but across most of Canada and the United States. They can be found in warm and cold waters across low and high elevations.
The North American river otter has a long, slender body that is coated in two layers of thick fur. Their dense undercoat protects the otter from the cold and the coarse outer layer is coated in water repellant oil that is secreted from glands. An otter’s powerful tail is thick and long, which helps them navigate through the water. While their legs are relatively short, they can run up to 15 miles per hour on land. Their feet are webbed, which propels them through the water.
River otters are excellent predators. Their diet primarily consists of fish, but they eat just about anything that can be found in or along the water. This includes crustaceans, snails, insects, birds, shellfish, frogs, rodents, and turtles. Otters have several adaptations that allow them to be efficient and deadly predators. They have excellent eyesight above and below the water. A third transparent eyelid, also known as a nictitating membrane, protects their eyes as they swim. Their small nostrils and ears can close underwater. River otters can hold their breath for up to eight minutes, by slowing their pulse to a tenth of their normal heart rate.
While river otters work hard hunting, they also like to play hard. Rivers otters often exhibit playful behavior such as mud sliding, burrowing in mud, and waterplay. Otters tend to live alone or in pairs but often socialize in groups. They communicate via vocalizations, touch, posturing, scent-marking, defecation, and urination.
Otter sightings are quite common along Putah Creek, but visitors are also likely to come across other types of evidence of otter activity. This includes otter tracks, imprints from belly slides, and scat, also called spraints. Otter tracks typically show five toes with claws and the imprint of the webbing between their toes. Spraints stand out from other types of scat due to poorly digested fish scales and crawfish parts. The next time you visit the creek, be on the lookout for the playful, charismatic, and powerful North American river otter!