Wildlife on Alcatraz Island consists predominantly of birds. However, there are, apart from insects, a few land animals on "The Rock". These creatures include: Deer Mice: genus Peromyscus Banana Slugs: genus Ariolimax California Slender Salamander: Batrachoseps attenuatus Deer Mice: Peromyscus maniculatus Deer mice are believed to be the only mammals inhabiting Alcatraz Island. These noctural rodents typically vary from 7-10 cm in length, with a tail reaching between 6-12 cm.
Peromyscus feed on insects, berries and fruit. The mice on Alcatraz are particulary fond of food scraps left behind by humans on the isle. Many of the mice have been found trapped inside garbage cans they could enter but not exit from. A study of Peromyscus conducted on Alcatraz in 1994 found that some of the island's mice have an unusual light tan coat color as opposed to the darker coats predominant in mice populations throughout the rest of the San Francisco Bay area.
Banana Slugs: Arriolimax ssp. These, usually yellow-colored, creatures can be found in moist areas on Alcatraz. They can reach up to 15-20 cm in length. The slime produced by the slugs assists them in their movements, water retention and defense. Their diet is varied, consisting of vegetation, fungi and dead animals. Despite their apparently unsavory and slimey nature, the slugs are edible. Numerous "slug festivals" and "slug races" are held yearly. Part of these festivities often include slug recipe/cooking contests. California Slender Salamander: Batrachoseps attenuatus These animals can be found in moist sites on Alcatraz, especially under rotting wood. They range from 6-12 cm in length and have tiny feet. They resemble earthworms (except for their having feet) in size and color. These salamanders "breathe" through their skin. And, like other salamanders, they can easily snap off their tails if need be. Studies done on them on the island indicate that the salamanders are old and have low reproductive rates.