Wildlife of Saint Helena, Ascension and Tristan da Cunha

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Saint Helena, Ascension Island and Tristan da Cunha, as well the other uninhabited islands nearby, are a haven for wildlife in the middle of the Atlantic Ocean. The islands are or were home to much endemic flora and fauna, especially invertebrates, and many endemic fish species are found in the reef ecosystems off the islands. The islands have been identified by BirdLife International as Important Bird Areas for both their endemic landbirds and breeding seabirds. [1]

Contents

See Ascension scrub and grasslands, Saint Helena scrub and woodlands, and Tristan da Cunha–Gough Islands shrub and grasslands for more details of the World Wildlife Fund-designated ecoregions.

Reptiles

There are no crocodilians or snakes on the islands. However, many sea turtles occur around the islands and breed on the beaches seasonally. Saint Helena has a small, introduced population of Asian house geckos, possibly the result of stowaways on produce shipments or cargo.

Birds

Saint Helena

While Saint Helena is not as major of a breeding site for seabirds as Ascension is, it once had more endemic avian species prior to human discovery, all (but one) of which are now extinct; the wirebird (Charadrius sanctaehelenae) is a type of plover and is the national bird. It is called the "wirebird" due to its rather stilt-like, thin legs that look like wire. Extinct bird species on the island include both the large and small Saint Helena petrel, the Saint Helena crake, swamphen, dove, and cuckoo as well as, most famously, the St. Helena hoopoe.

Ascension

Ascension Island used to be home to many breeding seabirds; most are now all but extinct on the main island, and the main breeding site is on nearby rat-free Boatswain Bird Island. Over 10,000 birds breed on this tiny island, which is home to Ascension frigatebirds, red-footed, brown and masked boobies, red-billed and white-tailed tropicbirds (known as Boatswain birds), and petrels. The sooty tern, known locally as the wideawake tern because of its distinctive call, is the most common breeding seabird on the main island, and the airport is named after it. The Ascension crake and the Ascension night heron, both flightless landbirds, are now extinct. The largest native land animal is the land crab Johngarthia lagostoma (formerly Gecarcinus lagostoma). [2]

Tristan da Cunha

Nesocichla eremita, the Tristan thrush. Nesocichla eremita Smit.jpg
Nesocichla eremita, the Tristan thrush.

Tristan da Cunha has a number of birds on par with Ascension. Inaccessible Island and Gough Island are together a UNESCO World Heritage Site and a wildlife reserve due to the large number of breeding seabirds found there, including endemics. The birds include the Tristan albatross, Atlantic yellow-nosed albatross, sooty albatross, Atlantic petrel, great-winged petrel, soft-plumaged petrel, grey petrel, broad-billed prion, Tristan skua, brown noddy, northern rockhopper penguin, great shearwater, sooty shearwater, Antarctic tern, and Tristan thrush. The Inaccessible Island rail, the world's smallest living flightless bird, is endemic to Inaccessible Island. The Tristan albatross is also native to the islands of Tristan da Cunha, as well as the Atlantic petrel. Gough Island is home to the almost flightless Gough Island moorhen and the critically endangered Gough bunting. The brown skua is the top predator of the island's ecosystem, feeding on other seabirds as well as landbirds such as the Inaccessible Island rail. However, birds of prey such as the barn owl and the Amur falcon are occasional visitors.[ citation needed ] In 1956, eight Gough moorhens were released at Sandy Point on Tristan, and have subsequently colonized the island. [3] Patrick O'Brian, in the fourth volume of his Aubrey–Maturin series has the ornithologist Fortescue in discussion with Stephen Maturin speak of an indigenous gallinule he observed on the island. [4]

Mammals

There are no native terrestrial mammals on either Saint Helena or Ascension Island, but plentiful marine mammals, including cetaceans, such as orcas, humpback and sperm whales, and rough-toothed, bottlenose, and pantropical spotted dolphins. Over the centuries, several introduced mammals have gone feral, including domestic cats, dogs, mice, rats, and rabbits; donkeys and goats once inhabited the island, but no longer roam free. On Ascension, however, free-ranging donkeys and sheep, as well as invasive rats and mice, are still common; cats have been eliminated. Goats were, historically, introduced to Saint Helena by the Portuguese to provide passing ships with a source of fresh meat.

Tristan da Cunha is a key breeding site for subantarctic fur seals (Arctocephalus tropicalus) and southern elephant seals (Mirounga leonina); rogue leopard seals (Hydrurga leptonyx) have occasionally been sighted, as well, considerably further north from their typical Antarctic range. Feral cats were eradicated from Tristan da Cunha by 1974. [5] The RSPB is also developing plans for the eradication of detrimental house mice from Gough Island. [5]

Terrestrial invertebrates

About 1,100 species of terrestrial invertebrates have been recorded on Saint Helena, with over 400 of these being endemic, occurring nowhere else. Prosperous Bay Plain (the site of Saint Helena Airport) is the only known habitat for about 55 of these endemic species. The Saint Helena giant earwig is almost certainly extinct, with the most recent chitinous remains having been found in the 1990s. However, its presence is firmly cemented within Saint Helena folklore, and hopes linger on. [6] [7] [8] [9]

The central peaks of Saint Helena are home to an extraordinary set of ground beetles of the tribe Bembidiini, which are strikingly morphologically different from bembidiines found elsewhere. [10] They have been found to form a clade of genetically similar species, being related to Bembidion alsium from the Indian Ocean island of Réunion. The African Omotaphus is the sister-genera to Bembidion, suggesting that both the Saint Helena and Reunión beetles were derived from a single common ancestor, emerging from the same dispersal events from a now-extinct African lineage that was a sister to Omotaphus. [10] All of the Saint Helena bembidiine species are threatened by habitat destruction and invasive species, with some likely to already be extinct. [10]

The only venomous animal on Saint Helena is Isometrus maculatus , a scorpion from the family Buthidae. Restoration plans for Inaccessible Island include investigating the impact and feasibility of eradicating a known parasitic wasp, Ichneumon insulator. [5]

Marine life

Saint Helena and Ascension Island both have excellent and well-preserved coral ecosystems, which are very diverse and contain many endemic and unique fish species.

The following fish are endemic to Ascension Island:

The following fishes are found off of both Saint Helena and Ascension Island:

The following fish are found only around Saint Helena:

Green sea turtles make a 3,000-mile (4,800 km) journey every 3–4 years from Brazil to Ascension Island to breed. They have been a protected species on the island since the mid-20th century, and lay their eggs on the pristine and quiet beaches of the island. The turtles which survive to adulthood will return to breed at the same beaches.

Within the waters surrounding Tristan da Cunha, the Tristan rock lobster is an endemic crustacean species, appearing on the territory's coat of arms. Other marine life includes temperate-water fishes, as well as the aforementioned pinnipeds and cetaceans.

Flora

The flora of Saint Helena is particularly diverse, with hundreds of endangered endemic species. In recent years there has been a program to conserve and replant the great forest on the island, which was destroyed by human activity, causing widespread soil erosion. The Millennium Forest Project has been successful, and the forest is expanding rapidly.

There are a few plants endemic to Ascension Island also, these include the Marattia purpurascens , Asplenium ascensionis , Xiphopteris ascensionense , Pteris adscensionis , Euphorbia origanoides , and Sporobolus caespitosus . There are several other extinct species. Ascension includes large artificial forests planted over the past hundred years, mainly with introduced species, on Green Mountain. This has threatened the endemic species on the island. [11] [12]

The management plan for the Gough and Inaccessible Islands World Heritage Site includes actions to develop and implement a biosecurity plan for the islands. [5] This includes steps to manage and eradicate non-native species such as an ongoing programme on Gough Island to eradicate Sagina procumbens . [13] Eradication programs on Gough Island are ongoing and are expected to require years of "concerted effort". [14] There is also a programme on Inaccessible Island to eradicate New Zealand flax and other invasive plants. [5]

Conservation

Saint Helena

Most of Saint Helena's endemic birds became extinct after human habitation began. Still, wirebird breeding programs are ongoing, although numbers are still falling. The Millennium Forest Project has been highly successful and has boosted the chances of Saint Helena's treasured flora and fauna, and this is the main concentration of conservation on the island.

Important Bird Areas

Ascension

Conservation has been a big issue on Ascension Island, and the Ascension Heritage Society has been set up to help deal with the issues. There have been successful programs for protecting green turtles, and the charity has worked hard with the RSPB to protect the bird life on the island. The main activities going on at the moment are a cat and rat eradication program, along with attempts to breed the native plant species on the island.

Important Bird Areas

Tristan da Cunha

Tristan da Cunha has implemented several extremely successful conservation programs, most notably, the World Heritage Sites of Inaccessible and Gough Islands. The low human population, and lack of feral cats and other predators, has helped the recovery of species on the islands.

Important Bird Areas

Invasive species

A population of house mice is present on Tristan da Cunha. They are thought to have been accidentally introduced by 19th-century seal hunters who docked on the islands, and the mice have adapted by growing 50% larger than mainland house mice. [15] These mice consume seabird eggs and chicks (as they nest on the ground), killing an estimated 2 million chicks annually. [15]

Related Research Articles

<span class="mw-page-title-main">Tristan da Cunha</span> South Atlantic island group

Tristan da Cunha, colloquially Tristan, is a remote group of volcanic islands in the South Atlantic Ocean. It is the most remote inhabited archipelago in the world, lying approximately 2,787 kilometres (1,732 mi) from Cape Town in South Africa, 2,437 kilometres (1,514 mi) from Saint Helena, 3,949 kilometres (2,454 mi) from Mar del Plata in Argentina, and 4,002 kilometres (2,487 mi) from the Falkland Islands.

<span class="mw-page-title-main">Inaccessible Island rail</span> Bird species endemic to the south Atlantic

The Inaccessible Island rail is a small bird of the rail family, Rallidae. Endemic to Inaccessible Island in the Tristan Archipelago in the isolated south Atlantic, it is the smallest extant flightless bird in the world. The species was formally described by physician Percy Lowe in 1923 but had first come to the attention of scientists 50 years earlier. The Inaccessible Island rail's taxonomic affinities and origin were a long-standing mystery; in 2018 its closest relative was identified as the South American dot-winged crake, and it was decided that both species are best classified in the genus Laterallus.

<span class="mw-page-title-main">Gough Island</span> Island in the South Atlantic

Gough Island, also known historically as Gonçalo Álvares, is a rugged volcanic island in the South Atlantic Ocean. It is a dependency of Tristan da Cunha and part of the British overseas territory of Saint Helena, Ascension and Tristan da Cunha. It is approximately 400 km (250 mi) south-east of the Tristan da Cunha archipelago, 2,400 km (1,500 mi) north-east from South Georgia Island, 2,700 km (1,700 mi) west from Cape Town, and over 3,200 km (2,000 mi) from the nearest point of South America.

<span class="mw-page-title-main">Inaccessible Island</span> Island in Tristan da Cunha archipelago

Inaccessible Island is a volcanic island located in the South Atlantic Ocean, 31 km (19 mi) south-west of Tristan da Cunha. Its highest point, Swale's Fell, reaches 581 m (1,906 ft), and the island is 12.65 km2 (4.88 sq mi) in area. The volcano was last active approximately one million years ago and is now extinct.

<span class="mw-page-title-main">Nightingale Island</span> Volcanic island in the South Atlantic Ocean

Nightingale Island is an active volcanic island in the South Atlantic Ocean, 3 square kilometres (1.2 sq mi) in area, part of the Tristan da Cunha group of islands. They are administered by the United Kingdom as part of the overseas territory of Saint Helena, Ascension and Tristan da Cunha.

<span class="mw-page-title-main">Nightingale Islands</span> Island group in Tristan da Cunha archipelago

The Nightingale Islands are a group of three islands in the South Atlantic Ocean, part of the Tristan da Cunha territory. They consist of Nightingale Island, Middle Island and Stoltenhoff Island. The islands are administered by the United Kingdom as part of the overseas territory of Saint Helena, Ascension and Tristan da Cunha. The Nightingale Islands are uninhabited.

<span class="mw-page-title-main">Coat of arms of Saint Helena</span>

The coat of arms of Saint Helena, part of the British Overseas Territory of Saint Helena, Ascension and Tristan da Cunha, was authorised on 30 January 1984.

<span class="mw-page-title-main">Stoltenhoff Island</span> Island in Tristan da Cunha archipelago

Stoltenhoff Island is a small uninhabited island in the South Atlantic Ocean, part of the Nightingale Islands. It is the smallest of the Nightingale Islands, and is to the northwest of Nightingale Island itself. They are governed as part of Tristan da Cunha, an archipelago and part of the British overseas territory of Saint Helena, Ascension and Tristan da Cunha. The island is part of the Nightingale Islands group Important Bird Area (IBA), identified as such by BirdLife International as a breeding site for seabirds and endemic landbirds.

<span class="mw-page-title-main">Tristan albatross</span> Large seabird from the family Diomedeidae

The Tristan albatross is a large seabird from the albatross family. One of the great albatrosses of the genus Diomedea, it was only widely recognised as a full species in 1998.

<span class="mw-page-title-main">Boatswain Bird Island</span> Island off the coast of Ascension Island

Boatswain Bird Island, also spelt Boatswainbird Island, is a small island some 270 metres (300 yd) off the east coast of Ascension Island in the South Atlantic Ocean with an area of approximately 5.3 ha. It is administered from Georgetown on Ascension, which is part of Saint Helena, Ascension and Tristan da Cunha, an overseas territory of the United Kingdom. Boatswain Bird Island should not be confused with the nearby, much smaller, Boatswain Bird Rock, only about 10 by 5 metres in size, located 570 metres (620 yd) south-east of the island and 360 metres (390 yd) north-east of the coast of Ascension. The southern coast of the island has an impressive natural arch.

<span class="mw-page-title-main">Atlantic petrel</span> Species of bird

The Atlantic petrel is a gadfly petrel endemic to the South Atlantic Ocean. It breeds in enormous colonies on Tristan da Cunha and Gough Island, and ranges at sea from Brazil to Namibia, with most records at sea being to the west of the breeding islands, and along the subtropical convergence. Adults are about 43 cm long, powerful, large, stocky, dark in color with white belly. Their head can appear to be grey in worn plumage. Brown undercoating of wings and tail. These petrels can live on average of 15 years of age.

<span class="mw-page-title-main">White-bellied storm petrel</span> Species of bird

The white-bellied storm petrel is a species of seabird in the family Oceanitidae. It is found in Angola, Argentina, Australia, Brazil, Chile, Ecuador, French Polynesia, French Southern Territories, Maldives, Namibia, New Zealand, Perú, Saint Helena, and South Africa. Its natural habitat is open seas.

<span class="mw-page-title-main">Grey petrel</span> Species of bird

The grey petrel, also called the brown petrel, pediunker or grey shearwater is a species of seabird in the Procellariidae, or petrel family. It is pelagic and occurs in the open seas of the Southern Hemisphere, mainly between 32°S and 58°S.

<span class="mw-page-title-main">Tristan thrush</span> Species of bird

The Tristan thrush, also known as the starchy, is a species of bird in the thrush family that is endemic to the British overseas territories of the isolated Tristan da Cunha archipelago in the South Atlantic Ocean.

<span class="mw-page-title-main">Ascension Island</span> British Overseas Territory in the South Atlantic Ocean

Ascension Island is an isolated volcanic island, 7°56′ south of the Equator in the South Atlantic Ocean. It is about 1,000 miles (1,600 km) from the coast of Africa and 1,400 miles (2,300 km) from the coast of South America. It is governed as part of the British Overseas Territory of Saint Helena, Ascension and Tristan da Cunha, of which the main island, Saint Helena, is around 800 miles (1,300 km) to the southeast. The territory also includes the sparsely populated Tristan da Cunha archipelago, 2,300 miles (3,700 km) to the south, about halfway to the Antarctic Circle.

<span class="mw-page-title-main">Ascension scrub and grasslands</span>

The Ascension scrub and grasslands ecoregion covers the dormant volcano, Ascension Island in the Atlantic Ocean. As well as shrubs and grasses wildlife on the island includes a range of unique flora and fauna. In particular the surrounding islets are important havens for many seabirds. However the seabird populations on Ascension Island itself have been severely affected by introduced species, especially cats, which were the subject of an eradication campaign between 2002 and 2006.

<span class="mw-page-title-main">Geography of Tristan da Cunha</span>

Tristan da Cunha is an archipelago of five islands in the southern Atlantic Ocean, the largest of which is the island of Tristan da Cunha itself and the second-largest, the remote bird haven, Gough Island. It forms part of a wider territory called Saint Helena, Ascension and Tristan da Cunha which includes Saint Helena and Ascension Island.

<span class="mw-page-title-main">Introduced mammals on seabird breeding islands</span>

Seabirds include some of the most threatened taxa anywhere in the world. For example, of extant albatross species, 82% are listed as threatened, endangered, or critically endangered by the International Union for Conservation of Nature. The two leading threats to seabirds are accidental bycatch by commercial fishing operations and introduced mammals on their breeding islands. Mammals are typically brought to remote islands by humans either accidentally as stowaways on ships, or deliberately for hunting, ranching, or biological control of previously introduced species. Introduced mammals have a multitude of negative effects on seabirds including direct and indirect effects. Direct effects include predation and disruption of breeding activities, and indirect effects include habitat transformation due to overgrazing and major shifts in nutrient cycling due to a halting of nutrient subsidies from seabird excrement. There are other invasive species on islands that wreak havoc on native bird populations, but mammals are by far the most commonly introduced species to islands and the most detrimental to breeding seabirds. Despite efforts to remove introduced mammals from these remote islands, invasive mammals are still present on roughly 80% of islands worldwide.

<span class="mw-page-title-main">Tristan da Cunha–Gough Islands shrub and grasslands</span>

The Tristan da Cunha–Gough Islands shrub and grasslands is a terrestrial ecoregion which covers the Tristan da Cunha archipelago and Gough Island in the South Atlantic Ocean. The islands' remote location gave rise to many endemic species.

References

  1. ↑ "Important Bird Areas". BirdLife data zone. BirdLife International. 2012. Retrieved 2012-11-09.
  2. ↑ Richard G. Hartnoll, Annette C. Broderick, Brendan J. Godley & Kate E. Saunders (2009). "Population structure of the land crab Johngarthia lagostoma on Ascension Island" (PDF). Journal of Crustacean Biology . 29 (1): 57–61. doi: 10.1651/08-2992.1 .{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. ↑ "Gough Moorhens". Beauty of Birds. Retrieved 5 January 2019.
  4. ↑ Patrick O'Brian, The Mauritius Command, (1977) HarperCollins 1996 p.129.
  5. 1 2 3 4 5 "Tristan da Cunha: Invasive species data & legislation". GB Non-native Species Secretariat. Archived from the original on 2017-07-24. Retrieved 7 July 2014.
  6. ↑ Kidston Mill
  7. ↑ Ashmole, P.; & Ashmole, M.J. (2000). St Helena and Ascension Island: A Natural History. Distributed by Kidston Mill. 500 pp.
  8. ↑ Ashmole, P.; & Ashmole, M. (2004). The Invertebrates of Prosperous Bay Plain, St Helena. Report to the St Helena Government and the Foreign and Commonwealth Office.
  9. ↑ Ashmole, P.; & Ashmole, M. (2004). Guide to Invertebrates of Prosperous Bay Plain, St Helena. Report to the St Helena Government.
  10. 1 2 3 David R. Maddison; John S. Sproul; Howard Mendel (2020). "Origin and adaptive radiation of the exceptional and threatened bembidiine beetle fauna of St Helena (Coleoptera: Carabidae)". Zoological Journal of the Linnean Society. 189 (4): 1155–1175. doi:10.1093/zoolinnean/zlz150.
  11. ↑ Duffey, E. (1964). "The Terrestrial Ecology of Ascension Island". Journal of Applied Ecology . 1 (2): 219–251. doi:10.2307/2401310. JSTOR   2401310.
  12. ↑ Ashmole, P. & Ashmole, M. (2000). St Helena and Ascension Island: A Natural History. A. Nelson.
  13. ↑ Cooper, J. et al., "Earth, fire and water: applying novel techniques to eradicate the invasive plant, procumbent pearlwort Sagina procumbenss, on Gough Island, a World heritage Site in the South Atlantic", Invasive Species Specialist Group, 2010, Retrieved on 12 February 2014.
  14. ↑ Bisser, P. et al., "Strategies to eradicate the invasive plant procumbent pearlwort Sagina procumbens on Gough Island, 2010", Retrieved on 12 February 2014.
  15. 1 2 Law, Jessica (22 October 2018). "Ambitious plan to remove "mega-mice" to save millions of seabirds". Bird Life.
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