From The Art and Popular Culture Encyclopedia
Webbed toes is the common name for syndactyly affecting the feet. It is characterised by the fusion of two or more digits of the feet. This is normal in many birds, such as ducks; amphibians, such as frogs; and mammals, such as kangaroos. In humans it is considered unusual, occurring in approximately one in 2,000 to 2,500 live births.
There are various levels of webbing, from partial to complete. For example, the rare Hose's Civet, a viverrid endemic to northern Borneo, has partially webbed feet. Most commonly the second and third toes are webbed or joined by skin and flexible tissue. This can reach either part way up or nearly all the way up the toe.