Animals of Muir Woods
A deep redwood canyon is a specialized habitat. The tannins in redwood bark and leaves repel insects, and the dense shade limits flowering and fruiting plants, so food is scarce for many species. What lives here is adapted to that constraint. The result is a short list of animals, but a specialized one: tiny pollinators, tree-cavity-dwelling bats, salmon returning to spawn, and a few iconic birds like the pileated woodpecker and northern spotted owl.
Download the Muir Woods Wildlife Checklist (PDF)Mammals: Bats
Researchers have observed ten species of bats in Muir Woods National Monument, nearly two-thirds of the bat species found on California’s central coast. Five are listed as Federal Species of Concern.
Bats roost in the cavities of giant redwoods: day roosts for sleeping, night roosts for resting between foraging flights, and maternity roosts in the warm months. Though often called “mice with wings,” bats are more closely related to primates than to rodents. Outside of humans, they are the longest-lived mammals for their size in North America. Most species use echolocation to hunt insects, and many function as pollinators and seed dispersers. Bat populations are declining worldwide, which makes a protected old-growth stand like Muir Woods especially valuable habitat.
Developed areas can support a few common bats such as the Mexican free-tailed bat and the big brown bat, but the high diversity in Muir Woods is unique to protected, ecologically intact forests.
Bat Species Observed in Muir Woods
Yuma myotis
Myotis yumanensis
Fringed myotis
Myotis thysanodes
California myotis
Myotis californicus
Long-legged myotis
Myotis volans
Silver-haired bat
Lasionycteris noctivagans
Big brown bat
Eptesicus fuscus
Western red bat
Lasiurus blossevillii
Hoary bat
Lasiurus cinereus
Townsend’s big-eared bat
Corynorhinus townsendii
Mexican free-tailed bat
Tadarida brasiliensis
Birds
Over 50 species of birds have been identified in Muir Woods across a year. Their abundance and song patterns vary with time of day, season, and weather. Spring mornings bring the greatest variety. Two species stand out: the northern spotted owl (federally threatened) and the pileated woodpecker, both of which favor old-growth forest with large snags.
Birds are relatively scarce compared to more open Bay Area habitats. The redwood’s tannins deter insects, and the canopy’s deep shade limits the flowers and fruits that support seed- and nectar-eating species. A 1923 Superintendent’s report put it bluntly:
“Birds, as is generally the case in a redwood forest, are conspicuous by their absence. Steller’s jay being the only bird seen in any numbers.”
A century on, the observation still holds. That said, patient birdwatchers regularly spot winter wren, varied thrush, chestnut-backed chickadee, and Pacific wren along the creek.
Download the Muir Woods Bird Checklist (PDF)Invertebrates
Visitors often comment on the apparent lack of wildlife in Muir Woods. A magnifying glass reveals the opposite: life in the redwood forest is abundant, just smaller than most people expect. From butterflies and banana slugs down to microscopic springtails, invertebrates play a central role in breaking down duff, pollinating understory flowers, and feeding the larger animals that do live here. Look for banana slugs along the boardwalk after rain. They are one of the easiest native invertebrates to spot.
Fish: Salmon and Steelhead in Redwood Creek
Muir Woods is home to two salmonid species: coho (silver) salmon and steelhead. Both are anadromous. Adults return to Redwood Creek in winter to spawn.
Coho salmon
Oncorhynchus kisutch
Adults typically in the creek December through January. Coho hatch in Redwood Creek, rear there for about a year, then migrate to the Pacific for roughly 18 months before returning to spawn.
Steelhead
Oncorhynchus mykiss
Follow the coho, usually late January through early March. Steelhead migrate upstream from the sea to spawn, then return to the Pacific.
Biologists conduct periodic fish surveys in Redwood Creek to monitor three critical life stages (juvenile, smolt, and adult) at both the population and individual level. In summer 2014, young coho were transferred to the Warm Springs Fish Hatchery at Lake Sonoma as a precaution against local extinction. More recently, 2024-2025 spawner surveys in Redwood Creek exceeded expectations, a hopeful sign for the population’s long recovery.
Frequently Asked Questions
Will I see a lot of wildlife at Muir Woods?
Not in the obvious, large-mammal sense. The forest is too dense and too food-limited for big game. You are more likely to notice banana slugs, Steller’s jays, varied thrushes, and the occasional salamander. Patient birdwatchers see the most.
Are there bears or mountain lions in Muir Woods?
Black bears are not resident in Marin County. Mountain lions are present in surrounding Mount Tamalpais State Park but extremely rarely seen inside the monument.
When can I see spawning salmon?
Coho salmon typically return December to January; steelhead late January to early March. Heavy winter rains trigger the runs.
Can I feed the wildlife?
No. Feeding animals inside the monument is prohibited. Human food does not give wildlife the nutrients needed to survive winter, and habituated animals become problems.