In the past, the Chatham Islands swarmed with animal life. Marine birds and mammals came ashore to breed or roost, bringing nutrients to enrich the soil. The forests were alive with bird and invertebrate life.
Waterways supported huge numbers of wetland birds and fish. The shore was a treasure trove of shellfish, crustaceans, fish and birds. Harvesting, large-scale clearance of vegetation (especially forest) for farming, and human-imported animals have taken a large toll on the wildlife.
Rats, mice, pigs, possums, hedgehogs, cats and dogs consumed innumerable indigenous animals and their food supplies. Cattle, sheep, goats, pigs, horses and possums have reduced the complex indigenous vegetation cover to scattered fragments. These animals are now controlled in most areas on the Chathams protected for conservation.
Mammals
Prior to human arrival, the only mammals at the Chatham Islands were marine creatures: seals, whales and dolphins. Seals and whales, formerly abundant, were hunted to near-extinction, especially during the nineteenth century. They have made a slow comeback since. Now it is possible to see fur seals at several breeding colonies and haulout sites. Sighting sea lions, leopard seals and elephant seals is a matter of chance encounter around the coasts. Whales and dolphins are regularly seen at sea.
Birds
Chatham petrel chick,
Pitt Island
Several bird species have become extinct since humans arrived at the Chatham Islands.
They include a penguin, a swan, a duck, several ducks, several flightless rails, a fernbird and a bellbird.
Endemic sea birds that have survived include toroa (northern royal albatross) which also breeds at Taiaroa Head near Dunedin, Chatham Island tāiko (now confined to one tiny population), tōrea (Chatham Island oystercatcher) found around the shores, Chatham Island shag and Pitt Island shag, and Chatham petrel.
Chatham petrel was confined for many years to Rangatira Island until 2002-05, when DOC began establishing a second population on Pitt Island. In 2008 work started on establishing a third population by moving chicks from Rangatira Island to artificial burrows within the Sweetwater Conservation Covenant, in the south of the main Chatham Island. This was the first return of an endangered bird species to the main Chatham Island, made possible by landowners Liz and Bruce Tuanui, and the Tāiko Trust, who predator-proof fenced the two and a half hectare Sweetwater Covenant with the aim of restoring seabirds to the site. This includes the critically-endangered Chatham Island tāiko which was successfully transferred there for the first time in 2007.
Parea (Chatham Island wood pigeon)
Surviving endemic land birds include parea (Chatham Island pigeon), Chatham Island warbler, Forbes' parakeet, Chatham Island snipe, Chatham Island tūī, Chatham Island tomtit and black robin. None of these birds are common and recovery programmes are underway for the most threatened of them.
Many sea bird species are still quite common around the Chatham Islands. Buller's mollymawk, prions, skuas, sooty shearwaters, storm petrels and little blue penguins are most likely to be seen at sea. Around the coasts, those most frequently seen include black-backed gull, red-billed gull, white-fronted tern, shags and skuas. Banded dotterel and pipit are often on the shore too.
Te Whanga Lagoon and the freshwater lakes and swamps of Chatham Island provide extensive habitat for wetland birds. Most common are black swan, black shag, mallard and grey ducks, pūkeko, welcome swallow, pied stilt and various migratory waders. In open country (farmland, bracken and shrubland), introduced finches and songbirds are common, as are harrier, spur-winged plover and buff weka.
Weka, imported from Canterbury (where they are now extinct) around 1905, have proliferated to such an extent that they are regarded as something of a pest at times, and are also a favourite seasonal menu item.
Birds of the forests include kākāriki (red-crowned parakeet), parea, Chatham Island warbler and Chatham Island fantail. Chatham Island tūī and Chatham Island tomtit are now largely confined to Pitt Island. Tūī were successfullly translocated from Rangatira Island to the south-west Chathams in 2009, but have yet to breed.
The common skink, an endemic Chatham species, is almost extinct on the main islands, but remains common on Mangere Island and Rangatira, as well as a few other outlying islands.
Invertebrates
Of around 800 species of insects described so far on the Chatham Islands, about 20 percent are endemic. In the past, the Chathams would have been absolutely bustling with invertebrates, nurtured in the nutrient-rich environment. Glimpses of this plenitude can be had at night on Rangatira, where in summer the forests swarm with spiders, cockroaches, weta and beetles.
Habitat destruction and introduced mammals have led to the loss of such invertebrate riches on the inhabited islands. On Chatham Island and Pitt Island, the most you are likely to encounter nowadays are great quantities of flies, orb-web spiders, and red admiral butterflies.
Pitt Island longhorn beetle
Threatened invertebrates of the Chatham Islands include the Rangatira spider, Chathams giant click beetle, giant stag beetle, soft speargrass weevil, Pitt Island longhorn, "Thotmus" weevil and giant stick insect. Most survive only on island refuges, whilst some are hanging on in forest reserves on the main islands.
Freshwater fishes
All freshwater fishes in the Chatham Islands are indigenous. They include both longfin and shortfin eels, lamprey, common bully and redfinned bully, common smelt and four galaxiid fish: giant kokopu, banded kokopu, koaro and inanga. The young of the smelt are harvested as whitebait. A new species of mudfish, endemic to the Chathams Islands, was recently discovered in a land-locked lake on the southern tableland.
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