Eastern Fox Squirrel (Sciurus niger)
The largest tree squirrel in North America, Bay Area populations frequently express a striking all-black (melanistic) coat that sets them apart from the rusty-orange form seen elsewhere.
San Mateo’s parks and neighborhoods are dense with Eastern Fox Squirrels — a non-native species that spread across the Bay Area after introductions in the early 20th century and now outnumbers native Western Gray Squirrels in many urban areas.