[edit]
NASA satellite image
Great white shark off Isla Guadalupe
Great white shark off Isla Guadalupe
Further information: Guadalupe Island Biosphere Reserve
Guadalupe Island was a major destination for Russian and American fur hunters seeking the Guadalupe fur seal (Arctocephalus townsendi) in the 18th and 19th centuries. Captain Auguste Duhaut-Cilly reported in 1827 that a Sandwich Islands (Hawaiian Islands) brig "had spent several months there and collected three thousand sealskins". The northern elephant seal (Mirounga angustirostris) was also ruthlessly hunted for the oil in its blubber.
Northern elephant seals were thought to be extinct by 1884 until a remnant population of eight individuals was discovered on Guadalupe Island in 1892 by a Smithsonian expedition, which promptly killed several of them for their collections. The northern elephant seals managed to survive, and were finally protected by the Mexican government in 1922.
Guadalupe shares the California chaparral and woodlands ecoregion with the Channel Islands of California in the United States, but the island was at one time practically denuded of all plants higher than a few centimeters by up to 100,000 feral goats.
Originally brought to the island in the 19th century by European whalers and sealers for provisions when stopping over, the population eventually eliminated most vegetation; the number of feral goats declined to a few thousand. Before this collapse, the main impact of the feral goat population was about the turn of the 19th/20th century. Naturalist A. W. Anthony wrote in 1901:
"It is directly due to the despised Billy-goat that many interesting species of plants formerly abundant are now extinct, and also that one or more of the birds peculiar to the island has disappeared, and others are following rapidly."
After the crash, the feral goat population once again grew, this time more slowly, until it had reached the new, lower carrying capacity at maybe 10,000–20,000 in modern times. The island had been a nature conservancy area since August 16, 1928, making it one of the oldest reserves in Mexico. Extirpation of the feral goats was long envisioned, but logistical difficulties, such as island size and lack of suitable spots for landing and encamping hunters and material, prevented this. In 2002, the Mexican government (including SEMARNAT) and the conservation group Grupo de Ecología y Conservación de Islas began extirpating the feral goats. In June 2005, after many years of false starts, the Mexican government had almost completed a round-up and evacuation of the remaining feral goat population. In 2007, the feral goat extirpation program ended (10,000 feral goats were killed). Guadalupe Island was designated a biosphere reserve on April 25, 2005.
French sea captain Auguste Duhaut-Cilly remarked on the tall trees on the north of Guadalupe Island as he sailed past on January 2, 1827. Of the four large tree species on Guadalupe Island (the Guadalupe palm, Guadalupe cypress, island oak, and Monterey pine), there were only old individuals left; the California juniper population had entirely disappeared. As the feral goats ate any seedlings that managed to germinate, no regeneration of trees was possible. Water, formerly plentiful as the common fogs condensed in the forests of the northern end of the island, today only occurs in a few scattered pools and springs. Because the springs were a critical emergency water supply for the human inhabitants, protective measures including feral goat fences were installed beginning in 2000, allowing new seedlings of many species to survive for the first time in 150 years. Seacology, a non-profit environmental group located in Berkeley, CA, provided funding to the Island Conservation & Ecology Group for the construction of 10 fenced exclosures to keep feral goats out of the most sensitive areas of Guadalupe Island.
In November 1850, U.S. Army Lt. George H. Derby passed the island on his expedition in the U.S. Transport Invincible. He described it thus: "This island is about 15 miles length and 5 in width. It is rocky + mountainous but capped with vegetation and is reputed to be thickly inhabited by wild goats of unusual size. Water is found upon the eastern shore and the Island is frequently visited by small vessels engaged in the capture of the sea elephant numbers of which animals are found upon its coast."
Many islands or marine species that reside on or near Guadalupe also frequent the Channel Islands, and vice versa. In stark contrast to the rampant extinction of terrestrial life that happened at the same time, Guadalupe was the last refuge for the northern elephant seal (Mirounga angustirostris) and the Guadalupe fur seal (Arctocephalus townsendi) in the 1890s. The island has been a pinniped sanctuary since 1975.
The movement of the cool, nutrient-rich water current promotes phytoplankton production and attracts both coastal and deep-water species, including spanish mackerel, yellowfin tuna and great white sharks.
Guadalupe is considered one of the best spots in the world for sightings of the great white shark (Carcharhodon carcharias), because of its clear water and large population of pinnipeds, their primary prey. Because of the aggregation of over 350 identified white sharks, the island has hosted a recreational cage diving industry from one boat in 2005, to as many as eight operators in 2019, bringing thousands of shark enthusiasts to the island. In 2019 the Mexican Department SEMARNANT suspended cage diving and sport fishing between May and December to evaluate tourism’s impact on the several hundred protected white sharks congregating there. The Mexican Government said the closure was intended to gather information to adopt the best sustainability practices that guarantee their conservation. As of January 10, 2023, cage diving with great white sharks at Isla Guadalupe, Mexico, is permanently prohibited. The Mexican Government’s ban covers all tourism inside the reserve, including film production and liveaboard diving.
The island has been recognised as an Important Bird Area (IBA) by BirdLife International.
Habitat types[edit]
Before the extirpation of the feral goats, surveys found eight major land habitats on Guadalupe:
Giant coreopsis (Coreopsis gigantea)
Cylindropuntia prolifera
Perityle emoryi
Pinus radiata cone
Flora of the coastal lowlands and rocky cliffs: mainly up to 200 metres (660 ft) above mean sea level (ASL), but higher on the steep cliffs. Largely unresearched due to difficult access, the cliffs might even harbor remnant specimens of the presumably extinct plants.
Succulent perennial herbs: 200–400 metres (660–1,310 ft) ASL, chiefly on the southern end and on the offshore islets, and in less steep areas towards sea level. Here, the highest number of endemic plants exist. Baeriopsis guadalupensis, Cistanthe guadalupensis, Dudleya guadalupensis, Hemizonia greeneana ssp. greeneana, H. palmeri, Nesothamnus incanus, and Stephanomeria guadalupensis are dominant endemics, and giant coreopsis (Coreopsis gigantea), a non-endemic native species, is also abundant.
Arid maritime shrubland: 400–600 metres (1,300–2,000 ft) ASL. Mainly in the southern portion around El Picacho. Native species occurring here include Ambrosia camphorata, Atriplex barclayana, Cylindropuntia prolifera and California boxthorn (Lycium californicum); none of these is endemic.
Herbland dominated by introduced plants: 600–800 metres (2,000–2,600 ft) ASL, mainly on the central plateau. This habitat is almost entirely a consequence of overgrazing; hardly anything of the original ecosystem remains. Dominant introduced plants are Avena barbata, Bromus berteroanus, great brome (B. diandrus), soft brome (B. hordeaceus sspp. hordaceus and mollis), red brome (B. madritensis ssp. rubens), tocalote (Centaurea melitensis), nettle-leaved goosefoot (Chenopodium murale), Filago californica, wall barley (Hordeum murinum sspp. glaucum and leporinum), crystalline iceplant (Mesembryanthemum crystallinum), M. nodiflorum, Polypogon monspeliensis and Sisymbrium orientale. The non-endemic natives dwarf coastweed (Amblyopappus pusillus), island false bindweed (Calystegia macrostegia ssp. macrostegia), Cryptantha maritima var. maritima, Filago arizonica, Gilia nevinii, California goldfields (Lasthenia californica), Pectocarya palmeri and Perityle emoryi as well as the endemics Cryptantha foliosa and Sphaeralcea palmeri can be found here also; some are still numerous. This probably was a mesic shrub/herbland before the goats destroyed the upland forest, upsetting the water supply. Native plants still found on Guadalupe, like Crossosoma californicum, laurel sumac (Malosma laurina) and the endemic Camissonia guadalupensis ssp. guadalupensis, presumably thrived here in former times, as would have such taxa as the native hoary-leaved ceanothus (Ceanothus crassifolius), wedge-leaved ceanothus (C. cuneatus) – and possibly also felt-leaved ceanothus (C. arboreus), which was found in 2001–2003 surveys –, Cammisonia robusta, red-flowering currant (Ribes sanguineum) and the endemic Hesperelaea palmeri, which have now disappeared from the island.
Guadalupe palm groves: 400–900 metres (1,300–3,000 ft) ASL on the northwest side of the island. There are hundreds of palm trees remaining, mainly in a single patch of this habitat. At least one other major palm forest existed at the western coast; it was still present in 1906 at "Steamer Point". As reproduction is presumably still ongoing, the species will likely recover in due time.
Guadalupe cypress forest: 800–1,000 metres (2,600–3,300 ft) ASL. Presently some 4,000 old trees, essentially limited to the central-northern part. Other cypress forests, such as a major stand NE of the present patch which was still extant in 1906, were destroyed by the goats early in the 20th century. There is still reproduction, but the water table appears to have declined to below the level required by the cypresses, and mortality of the old trees is high and can be expected to continue even after the removal of the goats.
Guadalupe palm – island oak – Monterey pine woodland: 900–1,000 metres (3,000–3,300 ft) ASL. This habitat has all but disappeared during the 20th century, due to the decline in numbers of the oaks and pines.
Guadalupe pine cloud forest with some island oak: restricted to above 1,000 metres (3,300 ft) ASL on the N-NE point of the island. The population of the pine has declined by about two-thirds during the last 35 years; it presently stands at about 130 old trees in the main population and about the same number scattered elsewhere. Reproduction is ongoing, with several hundred seedlings having successfully established themselves since 2000, and with the elimination of goat browsing, the pines will likely make a full recovery. The situation of the oak is direr; there are only 20 trees or so remaining (by about 1950, there were 100) and they appear past reproductive age. Not being restricted to Guadalupe, seedlings could be imported from elsewhere.
A ninth habitat type, California juniper woodland and extending on the central plateau below the cypress forest, was entirely gone by 1906. What other endemic lifeforms underwent coextinction with it will forever remain unknown.
Endemism[edit]
Animals:
Guadalupe fur seal (Arctocephalus townsendi)
Guadalupe fur seal (Arctocephalus townsendi) – only major breeding site
Townsend's storm petrel (Hydrobates socorroensis) – only known breeding site
The Guadalupe Monterey pine, almost extinct due to grazing by feral goats
Ainley's storm petrel (Hydrobates cheimomnestes) – only known breeding site
Guadalupe rock wren (Salpinctes obsoletus guadalupensis) – endemic
Guadalupe house finch (Haemorhous mexicanus amplus) – endemic
Guadalupe pipefish (Syngnathus insulae) – endemic
Guadalupe junco (Junco insularis) – endemic
Guadalupe caracara (Caracara lutosa) – endemic, extinct
Guadalupe ameiva (Pholidoscelis cineraceus) - endemic, extinct
Guadalupe Bewick's wren (Thryomanes bewickii brevicauda) – endemic, possibly extinct
Endemic spiders:
Habronattus gigas
Herpyllus giganteus
Kibramoa isolata
Sergiolus guadalupensis
Plants:
Baeriopsis guadalupensis – near-endemic
Brahea edulis (Guadalupe palm) – effectively endemic
Camissonia guadalupensis ssp. guadalupensis – endemic
Castilleja fruticosa – endemic
Cistanthe guadalupensis – endemic
Hesperocyparis guadalupensis (Guadalupe cypress) – endemic
Cryptantha foliosa – endemic
Deinandra frutescens – endemic
Deinandra greeneana ssp. greeneana – endemic
Deinandra palmeri – endemic
Dudleya guadalupensis – endemic
Dudleya virens ssp. extima – endemic
Eriogonum zapatoense – endemic
Erysimum moranii – endemic
Eschscholzia elegans – near-endemic
Eschscholzia palmeri – endemic
Galium angulosum – endemic
Githopsis diffusa var. guadalupensis – endemic
Hemizonia frutescens – endemic
Hemizonia greeneana ssp. greeneana – endemic
Hemizonia palmeri – endemic
Heteromeles arbutifolia var. macrocarpa – probably endemic
Lavatera lindsayi – endemic
Lupinus niveus – endemic
Marah guadalupensis – near-endemic or endemic
Perityle incana – endemic
Phacelia phyllomanica – endemic
Pinus radiata var. binata (Guadalupe Monterey pine) – near-endemic or endemic
Satureja palmeri – endemic; rediscovered in 2001–2003 surveys
Senecio palmeri – endemic
Sphaeralcea palmeri – endemic
Sphaeralcea sulphurea – endemic
Stephanomeria guadalupensis – endemic
Triteleia guadalupensis – endemic
Extinctions[edit]
Numerous taxa have gone extinct due to the habitat destruction by the feral goats, which in turn rendered the endemic fauna vulnerable to predation by introduced feral cats and adverse weather by depriving them of shelter.
There have been 5–6 extinctions of birds:
Guadalupe Bewick's wren (Thryomanes bewickii brevicauda), the late 1890s
Guadalupe spotted towhee (Pipilo maculatus consobrinus), the late 1890s
Guadalupe caracara (Caracara lutosa), 1906 – intentionally made extinct by humans, ironically because it occasionally preyed on young goats
Guadalupe red-shafted flicker (Colaptes auratus rufipileus), 1906 – the island was later recolonized by individuals of an extant mainland red-shafted northern flicker subspecies (which one is unknown)
Guadalupe storm petrel (Hydrobates macrodactyla), the 1910s
Guadalupe ruby-crowned kinglet (Corthylio calendula obscurus) – close to extinction (if, indeed, it still exists); it was not observed in 2000, despite thorough searches
Globally extinct plant taxa from Guadalupe Island are:
Castilleja guadalupensis
Hesperelaea palmeri
Pogogyne tenuiflora
and one species of plant incertae sedis
