How A Single Cat Hunted to Extinction The Entire Species of Stephens Island Wren

David Lyall held his breath as he made the first incision straight down the belly of a little mouse-like olive brown bird that lay on his desk. Lyall, an amateur ornithologist, had never seen this bird before, and he knew he had to work fast and dry the specimen quickly before maggot infestation took place. For the next several hours, Lyall’s fingers worked swiftly and deftly as he pulled away the skin from the muscle, working his way from the abdomen to the back and tail, and then up towards the neck and the head, until he had detached the entire carcass from the skin. He even cut a small hole in the back of the skull and carefully scooped out the brain. Once he had removed all tissues, he packed the now empty body with sheep’s wool, stitched up the incision and placed the specimen in the window to dry in the sun.

Over the next few months, Lyall repeated this process several times creating at least 15 specimens of what is now known as Lyall's Wren or the Stephens Island Wren (Traversia lyalli). These specimens—which now exist in nine different museums around the world—are all that is left of this species.

Cats kill billions of birds and mammals around the world every year, and has been responsible for the extinction of dozens of species. Photo credit: vvvita/Shutterstock

David Lyall was the assistant lighthouse keeper of the newly opened lighthouse on Stephens Island, a small wind-swept island no bigger than half a square mile at the northernmost tip of the Marlborough Sounds, in the South Island of New Zealand. The lighthouse was opened in 1894, and shortly afterwards, David Lyall, along with sixteen other people arrived at their new outpost. A naturalist, Lyall looked forward to his new post on the largely unexplored and uninhabit­ed island, a place where he could pursue his passions. Because life as a lighthouse keeper was mostly of isolation, David Lyall also brought with him his pregnant cat named Tibbles, to give him company. Perhaps, Lyall even looked forward to Tibbles giving birth to a litter of kittens, unaware of the havoc they would unleash on the island’s bird population.

Cats are fantastic predators. In the book Cat Wars, authors Peter Marra and Chris Santella estimate that outdoor cats kill around 2.4 billion birds in the United States alone. A large number of these victims are killed not for food, but for fun. Cats are stimulated by the chase and even if not hungry, they will still kill. Sometimes domesticated cats who are allowed to roam freely outside will bring their owners small presents in the form of a killed bird or a mouse.

 

Shortly after David Lyall took position as the assistant lighthouse keeper at Stephens Island, Tibbles started bringing him such presents. Although Lyall had been on the island for only a short time, he could put a name to most of the birds Tibbles brought him, except for one peculiar specimen. This bird was small, olive on the back, pale on the breast, with body feathers edged with brown. It had a narrow whitish yellow streak above the eye, short wings, and a long, straight bill. Lyall had never seen this bird before, and for that matter, no biologists ever had. Sensing that he was on the verge of a new discovery, Lyall sat down one evening and by the light of a paraffin lantern, started to prepare the specimens. He sent a number of them to some of the most renowned ornithologists of the time, including Walter Roth­schild, Walter Buller, and H. H. Travers.

Walter Buller immediately recognized it as distinct species and began preparing a scientific description to be published in an upcoming journal. Walter Roth­schild, a British banker and zoologist, acquired several specimens from Lyall for a handsome price. It was Rothschild who suggested the scientific name Traversia lyalli in honor of David Lyall, the discoverer, and naturalist H. H. Travers, who helped him procure the specimens.

One of the surviving specimen of Stephens Island Wren. Every known specimen of this extinct species was delivered to a lighthouse keeper by his cat. Photo credit: New Zealand Birds Online

Another specimen of Stephens Island Wren displayed in the Carnegie Museum of Natural History in Pittsburgh. Photo credit: Avenue/Wikimedia

Meanwhile, the cat population in Stephens Island grew and they began to kill the birds in alarming numbers. The matter was made worse by the fact that the wren was flightless, who could only run low on the ground or hop from branch to branch. The bird was originally found all over New Zealand, but predators such as the Polynesian rat killed off nearly the entire population except for a small colony on Stephens Island. The birds probably migrated to this isolated island during the last glaciation when it was connected to the mainland. When the sea level rose, Stephens Island became an isolated safe heaven with no natural predators, until David Lyall arrived with his cat.

By February 1895, less than a year since Tibbles brought the first specimen, the wren had become impossible to be found. That same month Lyall wrote regrettably to Walter Buller that “the cats have become wild and are making sad havoc among all the birds.” By then, the bird was seen alive only twice. On March 16, 1895, an edito­rial in the Christchurch newspaper The Press reported, “There is very good reason to believe that the bird is no longer to be found on the is­land, and, as it is not known to exist anywhere else, it has apparently be­come quite extinct. This is probably a record performance in the way of extermination.”

Some historical documents, however, claim that a few specimens were seen after 1895, and that the wren's extinction may have been spread out over a slightly longer period of time, such as two to three years.

In 1898, Stephens Island got a new lighthouse keeper who, at once, requested the Marine Department for shotguns and ammunition to get rid of the island’s swarming feline population. Nine months later, he proudly reported that he had shot more than 100 feral cats. It took another 26 years, but by 1925 the island had finally become cat free.

Stephens Island as seen from D'Urville Island. Photo credit: LawrieM/Wikimedia

The Stephens Island lighthouse. Photo credit: maritimenz.govt.nz

The Stephens Island Wren. Illustration by Virginia Greene