New Zealand has some of the strictest pet quarantine and import laws in the world, and for good reason. Being mammal-free until the arrival of humans, New Zealand was once home to a diverse population of endemic wildlife species. Throughout its history, the increase in the human settlements has threatened the native wildlife. Added to that were the non-native animals that were brought from other continents which became dominant species putting the endemic or native species at a disadvantage or driving them to extinction. One such extinction event occurred when cats were brought to an island with a rare species of flightless birds. Here’s how Tibbles the cat killed a rare species of birds to extinction.
Lyall’s wrens, or Stephens Island wrens, are an extinct species of small, flightless birds with olive-brown plumage. They had been widespread throughout New Zealand until the settlement of the Maori and from 1894 were only found on Stephens Island.
The Lyall’s wren is the best known of around five flightless passerines. Passerines are songbirds with a notable feature of having three toes of their feet pointing forward and one pointing backward to make perching easier. These birds used to mainly inhabit islands but unfortunately are all now extinct and in spite of conservation efforts. While the Lyall’s wren was widespread in all of New Zealand prehistorically, it became extinct when the Maori settled on the island and introduced the Polynesian rat and other non-native animals which preyed on the birds. It is believed that the birds soon drifted to the nearby Stephens Island which was connected to the mainland back when the sea levels were lower.
The birds were first spotted by the assistant lighthouse keeper, David Lyall, of Stephens Island and named after him. His cat, Tibbles, used to bring him carcasses of the birds that nobody knew existed until then.
June 1879 marks the beginning of human activity on Stephens Island. Until then, the wildlife grew and evolved without intervention. By 1894, the land was surveyed and the lighthouse was built. Soon, David Lyall moved into his post with his cat Tibbles which would sometimes bring back the carcasses of the wren. Lyall himself had only seen the bird alive twice and described it as a nocturnal creature. He called it the “rock wren” as it would be “running around the rocks like a mouse and so quick in its movements that he could not get near enough to hit it with a stick or stone.”
Being interested in natural history, Lyall sent specimens to naturalist Walter Buller, who identified them to be a new species. Zoologist Walter Rothschild also received nine more specimens through the curio dealer and taxidermist Henry H. Travers.
Walter Buller, a naturalist who was well-known in the field of New Zealand ornithology and the author of A History of the Birds of New Zealand, received the specimen from Lyall in June of 1894. He sent it to London so that the artist John Gerrard Keulemans could make a lithograph plate to accompany its description. Lyall finds further specimens and sells them to Henry H. Travers who then sells them to zoologist and politician Walter Rothschild. Both Buller and Rothschild made descriptions of the wren before its extinction. They were described to have olive brown plumage with an yellow stripe through the eye. The females had a grey underside, while in males it was brownish-yellow with the body feathers edged with brown.
Though Tibbles is often blamed for the extinction of the Lyall’s wren, there were other feral cats on the island that hunted the flightless bird for food. It is believed that a pregnant cat brought to the island escaped resulting in feral cats becoming a new invasive species.
Cats were not native to New Zealand. In fact, except for a three species of bats, New Zealand did not have any land-based mammals until the Maori and the Europeans started arriving. The introduction of these new mammals permanently altered the distribution of the native wildlife. Though the effects of feral cats on native species are not well-documented, it is believed they were responsible for the extinction of six local species of birds and 70 subspecies. There had also been a dramatic decrease in other native wildlife populations including that of rabbits, short tailed bats, black stilt, kakapo, and the North Island saddleback which were brought back through conservation efforts and legal euthanization of feral cats.
The account of Tibbles being the sole reason for the extinction of Lyall’s wren was actually a claim by Walter Rothschild. Later in 2004, the research of Galbreath & Brown and Medway uncovered the actual story that it was the work of more than one cat. According to the research, the cats were introduced in Stephens Island between February 17 and 20, 1894, by the Europeans who arrived there to build and work in the lighthouse. A pregnant cat escaped resulting in the increase of cat population as an invasive species. By 1925, all the cats on the island were exterminated and only 16 to 18 specimens of the Lyall’s wren exist, including subfossil bones, that were collected by Lyall, Tibbles, and professional collectors.
[sources: Wikipedia, BusinessInsider, NZBirdsOnline]