Anacapa Island, located only about from the urbanized coast of
Southern California], provides a critical habitat for
seabirds,
seals such as
California sea lions, and several
endemic plants and animals.
Great white sharks, feeding on seals, are found in the waters of the Channel Islands, including Anacapa. The island has a somewhat diverse flora, including around 150 native plants, including 16 endemics (two of which are unique to the island) plus many
introduced species.
Birds Anacapa has around 69 species of birds. The island's steep lava rock cliffs incorporate numerous caves and crevices that are particularly important for the increasingly rare seabird
Scripps's murrelet (a threatened species known as Xantus's murrelet until 2012). The cliffs are also an important location for the
ashy storm-petrel. The largest breeding colony of the
California brown pelican in the United States, and one of only two in California, also occurs on Anacapa Island. This is where the brown pelican has been able to recover dramatically from near-extinction in the 1970s. The islets of Anacapa also host the largest breeding colony of
western gulls in the world. Western gulls begin their nesting efforts at the end of April, sometimes making their shallow nests just inches from trails. Fluffy chicks hatch in May and June and fly away from the nests in July.
Mammals, reptiles, and amphibians The only native land mammal on the island is a unique subspecies of deer mouse (
Peromyscus maniculatus anacapae), which occurs on all three islets but nowhere else. (
San Clemente Island in the southern Channel Islands also has an endemic subspecies of deer mouse.) Anacapa has two native reptiles: an endemic form of the
side-blotched lizard (
Uta stansburiana hesperis) and the less-common California alligator lizard (
Elgaria multicarinata multicarinata). There is one amphibian, the
Channel Islands slender salamander (
Batrachoseps pacificus). Marine mammals and other marine life abound on Anacapa.
Vegetation Anacapa's prolific and dense vegetation was once dominated by the showy giant coreopsis (
Leptosyne gigantea) previously named
Coreopsis gigantea, an erect, shrubby perennial with a stout, succulent trunk growing to some tall. The main trunk grows up to thick and often resembles a small tree. During its blooming season, March to May, it bursts forth with a mass of showy, bright yellow flowers and green leaves. Giant coreopsis provided shelter and perches for seabirds and land birds, and nesting habitat for many. The prolific seeds provided abundant food for the endemic Anacapa deer mouse, and for many small birds. The island's stands of giant coreopsis, as well as all the other plants of its coastal bluff community, were devastated by sheep grazing in the late 1800s and early 1900s, rabbit browsing in 1910-1950s, and by large-scale destruction of native vegetation associated with facility and road development by the
United States Coast Guard during construction and manning of the Anacapa Light Station. Only small patches and individuals of native plants remained.
Malacothrix junakii is a rare species of
aster known by the common names Anacapa Island desert-dandelion, Junak's desert dandelion, and Junak's malacothrix that is endemic to Anacapa, where it is known from just two occurrences. It occurs in the coastal scrub of the island and was described to science as a new species in 1997.
Introduced species Introduced mammals on Anacapa Island included
domestic cats,
sheep, rabbits, and black rats. Black rats (
Rattus rattus), also known as ship rats, had a major impact on wildlife on Anacapa Island, including seabirds such as Scripps's murrelet, reptiles and amphibians, intertidal and terrestrial
invertebrates, and vegetation. Before a rat eradication program in 2001–2002, more than 96 percent of Scripps's Murrelet nests on Anacapa were attacked by invasive rats. The rats were certainly introduced sometime prior to 1939 (when they were noted by
National Park Service researchers Sumner and Bond), probably in supplies brought onto the island for
sheep ranching or building the lighthouse. The National Park Service says there is evidence they were present in 1907. A 1979 study noted that they could have been introduced from a
shipwreck, such as that of in 1853.
European rabbits were introduced to East Island either as an emergency food supply for lighthouse personnel during
World War II or as pets. They were present from the 1940s until at least 1965. No rabbits were recorded from Middle or West Anacapa. Domestic cats were introduced to Anacapa as pets of the fisherman "Frenchy" after whom Frenchy's Cove on West Island is named. In 1966, there remained a small population. Sheep were grazed on the island for many years. There are records from the 1870s through the 1930s. Many writers reported that in the absence of springs on Anacapa sheep would lick the moisture that accumulated on each other's fleeces from the coastal fog. The native flora was affected by the
forage grasses that farmers introduced to feed their flocks, and by soil-compaction caused by the sheep's hooves. Reproduction of ground-nesting species such as the
meadowlark and
horned lark is also thought to have been harmed by grazing. After completion of the lighthouse and associated facilities, the U.S. Coast Guard planted two types of iceplant on East Anacapa Islet: red-flowered iceplant (
Malephora crocea) and sea fig, also called freeway iceplant
(Carpobrotus edulis x aequilaterus). Both species are highly invasive. The National Park Service has initiated a restoration project to eradicate all of the ice plant by 2016, the centennial of the
National Park Service Organic Act.
Restoration Vegetation on Anacapa began to recover after the removal of sheep about 1938 and rabbits in the 1950s. Black rats were successfully eradicated from Anacapa Island by 2003, under a controversial program that involved an aerial application of the
rodenticide brodifacoum with the assistance of
Island Conservation. This was the first time a rodenticide had been applied aerially in
North America (the technique was pioneered in
New Zealand). One complicating factor was the presence of the native deer mouse subspecies (
Peromyscus maniculatus anacapae). This was the first time that biologists had attempted to eradicate one rodent species from an entire island where an endemic rodent was present. A tool called Population Viability Analysis, or PVA, is a species-specific method used to assess the probability of a population's extinction in a given number of years. Based on the result of a study, PVA determined that a population of 333 deer mice had a high chance of survival. Approximately 300 deer mice were captured prior to the application of rodenticide and reintroduced after poison levels had dropped, which was about three months. The program cost about $1.8 million. A study after the eradication project showed that nesting attempts by Scripps's murrelets on Anacapa had more than doubled, average hatching success was up from 42 to 80 percent, and average nest predation was down from 52 to 7 percent. Only four months after the rodenticide applications,
Cassin's auklet (
Ptychoramphus aleuticus) began nesting on Anacapa. This was significant as there were no previous records of the bird nesting on the island and it is known to be highly susceptible to rat predation. ==Climate==