LIMUW | SANTA CRUZ ISLAND

Permanent Indigenous villages may have been established on the Channel Islands as early as 8,000 years ago.² The Chumash lived on the Northern Islands, and the Tongva on the Southern Islands.

The Island Chumash relied primarily on maritime resources supplemented with gathered island plant life and mainland plants acquired through trade, and so did little to disrupt the soil.² However, they did shape the island landscapes through periodic burning.⁷ The intentional and accidental transportation of nonnative species also left their mark, occurring along maritime trade routes that connected the islands to the mainland and to each other. Seaworthy driftwood-plank canoes called tomols³ carried the island Chumash across the channels, where they conducted a highly developed system of trade based around shell beads.⁸ This shell bead coinage was made primarily on Santa Cruz island⁹ from the shells of Olivella biplicata,⁸ a sea snail commonly called Purple Dwarf Olive.¹⁰ Some species like the Island Fox may have been brought between islands as pets. Other species, like Western Harvest Mice, were probably stowaways.⁴

European invasion and the establishment of the mission system were devastating for the Indigenous people of the Channel Islands. The Spanish contributed to the crash of the shell-bead economy by introducing Venetian glass beads.³ European diseases were introduced, killing two-thirds of the Chumash population on Santa Cruzin in less than a decade.³ Native burning practices were suppressed. Grazing by Spanish livestock and mission herds destroyed food plants.¹¹ Plagued by new diseases, with their economy unraveling and food sources disappearing, Chumash were forced onto missions, where they were further subjected to illness and horribly oppresive conditions; the industry and economy of the mission system relied on native labor.¹² The last of the Chumash left Santa Cruz Island in 1822, most for the Missions San Buenaventura and Santa Barbara.⁹ Today, the Chumash population numbers 5,000 strong, and some can trace their ancestry back to the Channel Islands. The only federally recognized Chumash Band is represented by the Chumash reservation at Santa Ynez.

In addition to native flora shared with the mainland, the Channel Islands have a high number of endemic plants: plants found nowhere else in the world. Endemic plants on the Channel Islands followed at least two divergent evolutionary paths. “Paleoendemics” are relict species that have persisted on the island long after their mainland counterparts perished.² Island Live Oak (Quercus tomentella)⁴ can be found in the mainland fossil record, as can Island Ironwood (Lyonothamnus floribundus).² Twenty-three-million-year old fossils of Island Ironwood can be found across the southwest.² Santa Cruz Island Manzanita (Arctostaphylos insularis) fossils can be found in Los Angeles’s La Brea Tar Pits.⁵ In contrast, “neoendemics” evolved in their new island habitats to create species distinctly different from their mainland ancestors.² For example, Island Big-pod Ceanothus (Ceanothus megacarpus s. insularis) is less dependent upon fire for germination than mainland species.^4,6

With nonnative vertebrates gone from Santa Cruz Island, the Nature Conservancy could now turn its attention to nonnative invasive plants, ranked as one of the largest threats to the island ecosystem.1 From the 1840s to the 1980s, when ranching and crop production were at their height, many nonnative plant species were established on Santa Cruz.³⁸ By 1995, 170 nonnative plants were considered naturalized on Santa Cruz, representing 26% of the island’s total flora.¹ In 2007, the Nature Conservancy identified 55 of these nonnative species as high priority weeds. Their following eradication efforts, targeting 24 of these species, included unconventional techniques. Weed technicians targeting Pampas Grass (Cortaderia selloana) fired herbicide-filled paintball shells at the plants from a small helicopter.³²

Although the removal of sheep, pigs, and cattle³⁹ from Santa Cruz Island has allowed for the gradual recovery of native plants, the removal of livestock also released weeds that had previously been held in check by constant grazing. The invasive perennial Fennel, first introduced to Santa Cruz in the 1800s40 responded very strongly to predation release. In 1991, it extended its range to 10% of the island’s area, growing thickest in areas most disturbed by grazing animals.³⁹ Fennel is especially insidious because of its allelopathic potential, producing biochemicals that impact the growth and germination of native flora.^6,39

Yellow Star Thistle (Centaurea solstitialis), California’s most common and one of its most highly destructive invasive weeds,² can also be found on Santa Cruz. Yellow Star Thistle is a European weed first documented in California in 1851² and on the island in 1930.⁴¹ In addition to fragmenting habitat and displacing native plants, Yellow Star Thistle can deplete groundwater and can poison and kill horses with a neurotoxin that causes “chewing disease.”²

On Santa Cruz Island pollination is influenced by the invasive Argentine Ant (Linepithea humile). A native of northern Argentina, southern Brazil, Uruguay and Paraguay,² the Argentine Ant can now be found on four of the Channel Islands: Santa Cruz, San Nicolas, Santa Catalina and San Clemente islands.⁴² A study on Santa Cruz island observed pollinator interactions on native plants, including Island Morning Glory. When present on Island Morning Glory, the highly aggressive Argentine Ant chased off native pollinators, including 11 species of native bees. By contrast, Monomorium ergatogyna, the most common native ant observed on the Island Morning Glory, is tiny and slow moving and therefore highly unlikely to disrupt pollination. Although eradication of Argentine Ants is difficult, the study did prove that when Argentine Ants were removed from Island Morning Glory plants native pollinators returned. At present, only 2% of Santa Cruz Island has been invaded by Argentine Ants.⁴³

The impact of feral pigs and sheep were felt most directly by the tender stalks, leaves and rootlets of native plants. However, these ungulates also played roles in the demise of a furrier Santa Cruz native: the Island Fox. The Island Fox is endemic to the Channel Islands and is the smallest fox species in North America, smaller than your average house cat. Adults are only 6.5 to 8 inches high, and weigh 2.5 to 6 pounds. Their tail makes up a third of their 23 to 27 inch long body.¹⁸ They are perhaps the most well-known example of island dwarfism,¹⁹ a phenomenon that also shrunk the Pygmy Mammoth of the Pleistocene.³

Subspecies of Island Foxes are found on six of the eight Channel Islands - all but the two smallest islands, Anacape and Santa Barbara.¹⁸ There is debate about how Island Foxes first found their way to the Northern Islands. Some contend that the foxes washed ashore, carried across the Santa Barbara Channel on flotsam and jetsam by a large storm. Others believe that they were transported across the channel by the ocean-bound Chumash.20 Regardless of their origin, there is little dispute that the Chumash dispersed the foxes throughout the islands and brought them to the more remote Southern Islands.²¹ The Chumash regarded the Island Fox highly enough to carefully bury them. Remains of 51 Island Foxes that appear to have been intentionally buried by indigenous populations were found on four of the Channel Islands. In some cases these foxes were buried alongside human remains; in others, the foxes were carefully folded head to tail and buried alone.²²

Populations of five of the six Island Fox sub- species began to decline sharply in the early 1990s, falling by as much as 95% on San Miguel, Santa Rosa and on Santa Cruz Island. By 2003, the adult fox population on Santa Cruz numbered between 75 to 100 adult foxes. The total Island Fox population was only 25% of what it had been between 1993 and 1994, reduced to around 1,300 foxes.²³ Following years of pressure from the Center for Biodiversity,²⁴ the U. S. Fish and Wildlife Service designated four subspecies of Island Fox as endangered in 2003: San Miguel Island Fox (Urocyon littoralis littoralis), Santa Rosa Island Fox (U. l. santarosae), Santa Cruz Island Fox (U. l. santacruzae), and Santa Catalina Island Fox (U. l. catalinae).²⁵

On Santa Catalina Island, the most highly populated and easily accessible of the Channel Islands,²⁶ the spread of canine distemper from introduced, domestic species was to blame.²³ (The island has over 4,000 residents and receives about 800,000 visitors per year.²⁶) On San Clemente, an island owned and administered by the U.S. Navy,²⁷ collisions with cars posed the greatest risk.²³ But on the Northern Channel Islands, the precipitous population declines were caused by the talons of a new island predator: the Golden Eagle.²³ Golden Eagles were only occasionally visitors to the Channel Islands until the early 1980s. Over the next 20 years, Golden Eagles became year-round Island residents, establishing their first nesting sites on Santa Cruz in the early 1990s.²⁸ The incursion of the golden eagles onto the Channel Islands was made possible because of a perfect storm of anthropogenic ecological disruption…

Until the 1980s, Golden Eagles had been kept from the Channel Islands by intensely territorial Bald Eagles. The Channel Islands were considered one of only two “breeding metropolises” for Bald Eagles in California. In the early 1900s, there were at least 24 nesting pairs on the Channel Islands, including five pairs on Santa Cruz Island.²⁹ Bald Eagles lived harmoniously with Island Foxes, feeding mostly on marine wildlife.³⁰ This ocean-based diet was the downfall of the Channel Islands Bald Eagle population. From 1947 to 1961 between 37 to 53 million liters of sludge were disposed at an ocean dump site only 15 km off the shore of Santa Catalina Island. This sludge contained a pesticide called DDT.²⁹ An estimated 1,800 metric tons of DDT were also discharged offshore of the Palos Verdes Peninsula from the Joint Water Pollution Control Plant outfall. In 1996, the Environmental Protection Agency designated this area as a Superfund site.31 DDT insidiously worked its way up the ocean food chain to Bald Eagles. The poison weakens the shells of Bald Eagle eggs, causing them to break before they hatch. Bald Eagle populations declined across the country, and were completely absent from the islands by the 1960s.³¹ With Bald Eagles gone, Golden Eagles were free to visit the Channel Islands without persecution. But the absence of Bald Eagles was not the only factor enticing Golden Eagles to set up permanent residence on the islands; the Golden Eagles discovered that the islands were rich with an abundant food source: feral piglets. On Santa Cruz Island, feral pigs created what is described as a “hyperpredation” scenario. Although feral piglets were the Golden Eagles’ primary food source, the eagles also dined on a wide variety of mammals and birds, including deer mice, sheep, ravens, American Kestrels, and,²⁸ most damagingly, Island Foxes. Island Foxes, active during the day,³² unaccustomed to raptor predation, and unable to find cover in encroaching nonnative grasslands,²⁰ were easy pickings for the Golden Eagle. The feral pig population suffered little from heavy Golden Eagle predation; pigs reproduce quickly, can bear young in any season, and are only vulnerable to the eagles as small piglets.³² Tiny Island Foxes, on the other hand, reproduce slowly. Less than 60% of mature female foxes produce pups each year on Santa Cruz, and those that do wean an average of only 1.5 pups.³² In order to save the Island Fox from extinction four distinct efforts had to be made. Feral pigs had to be eradicated, and were in 2007. Golden Eagles had to be removed from the islands, and the Bald Eagles had to be re-established. Lastly, the Island Fox populations themselves had to be replenished. Capturing and relocating the Channel Island Golden Eagles was not easy. The Nature Conservancy and National Park Service1⁹ began relocation efforts in 1999.¹⁶ Young and eggs were removed from nests.¹⁶ Initially, most adult eagles were captured using bownets, which were hidden, baited and manually triggered when an eagle was present. Over the

course of the following seven years, however, the remaining eagles became increasingly evasive. The final two birds were so tricky to capture, that captors branched out to more unconventional, although unsuccessful, methods including a fake egg filled with a sedative and a robotic dog dressed up as an Island Fox.¹⁶ The last Golden Eagles was finally captured in 2006, by Prohunt’s helicopter pilot and a net-gun operator well versed in the behavior of helicopter- pursued eagles.¹⁶ Between 1999 and 2006, a total of 44 Golden Eagles were relocated to the mainland.¹⁹ The re-establishment of Bald Eagles carried its own challenges. In 1980, the Institute for Wildlife Studies (IWS), United States Fish and Wildlife Service and the California Department of Fish and Game began a program to reintroduce eagles to Santa Catalina Island. Over the next six years, 33 eagles from northern California, Washington and British Columbia were released on Catalina at artificial nest sites called hacking platforms. Although many of the birds remained on the island and formed breeding pairs, DDT contamination continued to cause eggs to break. Although DDT had been banned from the US in 1972, lingering DDE (a metabolite of DDT) could be found in the fish, gulls and marine mammals that the Bald Eagles preyed upon. For the chicks to survive, eggs were removed from nests and hatched in captivity. Adults unknowingly incubated artificial eggs until researchers returned the safely hatched chicks to the nests.³¹ In 2002, the National Park Service and IWS began a re-establishment effort on the Northern Channel Islands. Between 2002 and 2006, the IWS released 61 eagles on Santa Cruz Island.³³ In 2006, two chicks hatched successfully on Santa Cruz, the first wild-born chicks to hatch on the Channel Islands in over 50 years.³⁴ The success on Santa Cruz prompted the transition away from hand manipulation on Catalina, which ended completely in 2009. Between 2006 and 2015, the IWS banded 107 naturally hatched chicks on Santa Cruz, Santa Rosa, Anacape, Santa Catalina and San Clemente Islands.³³ 2015 estimates put the current Channel Island Bald Eagle population at 41 individuals, most of which are breeding adults.³³ Also in 2002, the National Park Service began a captive breeding program for Island Foxes on Santa Cruz.²³ The program lasted six years. As of 2015, no known Golden Eagle predation had occurred for three years.³⁵ Today, more than 2,100 foxes live on Santa Cruz Island alone.³⁰ In August of 2016, the Santa Cruz Island subspecies and two others were removed from the Endangered Species list, making their recovery the fastest of any mammals listed under the Endangered Species Act.³⁷ The fourth subspecies, the Santa Catalina subspecies, was downlisted to threatened, as it still faces risks from the canine distemper virus.³⁰