North American Beaver ( Castor condenses) have maintained a presence in the Lake Wingra watershed for years. Never very numerous, they occasionally block little tributaries to Lake Wingra and build their lodges along the shoreline. The center of beaver activity and location of their lodges moves around the Lake and surrounding marshes in response to the abundance of their favorite trees and shrubs, and perhaps also varies in response to other factors of beaver life and the environment we are not aware of.
In the past year or so beaver have built a little dam on a spring-fed tributary to Lake Wingra on its north shore. This is how it appeared in early February.