For a few weeks in February of 2003, a trio of River Otters lived on the island in the small pond in Northstar Park. They returned for at least one visit after that, but I don't believe they have been seen since. The otters were documented in Jean Jackman's Davis Enterprise column, At The Pond. Be careful not to confuse them with Muskrats that also frequent similar places but are typically smaller and more shy.
River otters can also be seen at the Vic Fazio Yolo Wildlife Area swimming in various canals. They enjoy barking at passerbys and swimming alongside your vehicle. They have also been spotted in Putah Creek near the Putah Creek Boulders. They can also sometimes be spotted outside town around Lake Solano County Park just west of Winters
Between mid-December 2009 and mid-February 2010, a river otter was seen occasionally at West (Area) Pond. The Pond's SW corner is the intake area from the streets and gutters surrounding the Pond. Trash like bottles and food wrappers, as well as water, flow into the Pond from that spot. At dusk on a very cold day in February, we spotted the otter swimming near the trash "collector" and then it swam north. It stopped briefly to handle a styrofoam cup that was floating on the surface before we lost sight of it. I have only minimal "I.D. photos to document it. I hope we all get to see an otter at West Pond again.
Two baby river otters were spotted underneath the railroad bridge on Putah Creek in March 2012. They appear to have a den there.
River otters have been spotted at the UC Davis campus arboretum in 2012 and it's been purported that the local adult duck population is part of their diet. A particular incident, perhaps involving an otter, was witnessed by a few passersby in November of 2012 at the Australian Collection of the arboretum where a duck was pulled under water by an unseen animal and dragged 20 meters, as evidenced by the trail of bubbles, to a brush area that was visually occluded.
That's right. Today my husband John told me he was in the Arboretum and saw an Otter and a White Heron. Together they were catching small fish. The White Heron was following the Otter; guess the Otter was showing the way to the fish and/or facilitating the White Heron's 'food job'. The Otter was causing a lot of water bubbles.
2013-06-05 12:01:11 I just saw one playing in the water today (6/5/13) right by King Hall —JennyBickford
2013-09-09 11:19:19 I just saw one playing in the water today right in the middle of Lake Spafford! —JenniferRutherford
2014-08-18 00:15:56 See my comment in Lake Spafford. We spotted river otters on 8/17/14, and they quickly killed and ate a duck. Poor ducky. —EricJensen
Isn't that called just called nature? Certainly ducks are not endangered. loneshark
2015-8-22 2 otters spotted in arboretum near equestrian center
2015-10-02 14:54:49 I just watched two river otters playing under the pedestrian bridge near RMI. —Frankencar
2015-12-29 15:22:56 Two otters. At the Arboretum. Around noon. Near the equestrian center. Playing in the water. —MichaelPlotkin