North American beaver ("Castor canadensis") have re-colonized Martis Creek. The Emeryville Shellmound is also notable for its remains of beaver ("Castor canadensis"). Not surprisingly, the river is excellent habitat for beavers ("Castor canadensis"). Muskrats are much smaller than beavers ("Castor canadensis"), with which they often share their habitat. North American beavers ("Castor canadensis") historically flourished on the river. The California golden beaver ("Castor canadensis subauraticus") was historically extant. Beaver, "Castor Canadensis", was common in pre-colonial times. It has been controversial whether beaver ("Castor canadensis") were native to San Diego County. Beavers (Castor canadensis) are ubiquitous around Thompson, with a few residing in the city limits. Beaver ("Castor canadensis") and muskrat ("Ondatra zibethicus") are occasionally seen swimming in tidal creeks. Some common wetland species seen today include the Beaver ("Castor canadensis"), River Otter ("Lutra canadensis"). North American river otter ("Lontra canadensis"), American beaver ("castor canadensis") and snowshoe hare ("lepus americanus").