More than 2,000 species of plants and animals can be found within the park. However only three mammals are endemic to the islands. The Deer Mouse, Spotted Skunk, and Channel Islands Fox are the only endemic mammals. Other animals in the park include Island Scrub Jay, harbor seal, California sea lion, island night lizard, barn owl, American kestrel, horned lark and meadowlark and California brown pelican. Marine life ranges from microscopic plankton to the endangered blue whale, the largest animal ever to live on earth.
One hundred and forty-five of these species are unique to the islands and found nowhere else in the world. Over time some vertebrate species evolved into distinct subspecies on the islands. Channel Islands National Park supports a diverse terrestrial flora, including many rare, relict, and endemic species, as well as many nonnative species. Due to environmental conditions and isolation from the mainland, many of the plants that are native on the California mainland do not grow on the islands.