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The story of an ordinary house cat and its dire effect on an entire species is a somber tale. It involves a lighthouse keeper on a remote island in New Zealand, his pregnant pet cat “Tibbles,” and a small, flightless bird—the Lyall’s wren.
Tiny Stephens Island, barely a half square-mile in size, was an obstacle in maritime navigation and the need for a lighthouse became immediately realized following a handful of shipwrecks in the 19th century.
The Stephens Island or Takapourewa Lighthouse was first lighted on January 29, 1894 and became one of New Zealand’s most powerful lights with a range of 18 nautical miles. It is also the highest elevation above sea level of any lighthouse in New Zealand. The lighthouse and associated dwellings include a boat landing ledge and vertical tramway up the sheer cliffs.
The Discovery of
Stephens Island Wren
Once the New Zealand Maritime had decided to erect a lighthouse on Stephens Island in the 19th century, they entrusted David Lyall, an assistant lighthouse keeper at the time, with the job of being the first keeper.
David Lyall brought his family—his wife, at least one son, and his pregnant cat—to Stephens Island in 1894. The isolated island, located in New Zealand’s Cook Strait, was a closed, pristine environment, owing to a lack of human activity. Lyall, being the amateur natural history enthusiast he was, was overjoyed at the prospect of living here. He knew there would be several species to uncover and study. Unfortunately, unbeknownst to him, bringing Tibbles along for the ride would prove to be a costly mistake.
Tibbles was equally excited—her feline instincts kicked in almost immediately upon her arrival. Cats, despite their domestication, retain strong predatory urges from their wild ancestors. This drive is not just about survival; hunting can also be a form of play and natural behavior to keep their hunting skills honed.
On Stephens Island, Tibbles found an environment rich with opportunities to indulge these instincts. With no prior exposure to this new predator, the native species, including the unsuspecting Lyall’s wren, were ill-prepared for a skilled Tibbles.
Among the prey the house cat caught was a curious bird—one that was found nowhere else and completely unknown to ornithology at the time. She would bring these birds (sometimes half-eaten and sometimes intact) back as “presents” for Lyall, who performed amateur taxidermy operations on intact samples and brought them to prominent ornithologists of the time, including one named H.H. Travers.
This bird, later named the Stephens Island wren or Lyall’s wren (Traversia lyalli), exhibited several unique characteristics. It resembled a mouse more than a bird, leading a concealed life, scurrying among logs and under rocks. Occasionally nocturnal, it had adapted well to the island’s environment with its large feet and short tail, which it used to navigate the dense underbrush rather than fly. Possibly due to abundant food or the lack of predators, the Lyall’s wren never evolved to fly. It was highly unique in this regard, being one of the few species of flightless songbirds.
This made it easy prey for Tibbles and her feral kittens born on Stephens Island not long after the Lyall family moved there in 1894.
Tibbles and Her Feral Babies Topple A Fragile Ecosystem
Before Tibbles and other predators arrived, the Lyall’s wren had adapted to a predator-free environment. Being flightless, it relied on its agility and camouflage to avoid danger. However, these adaptations did not match a predator like Tibbles and her offspring.
Cats, known for their reproductive efficiency, can have multiple litters per year with several kittens each. Tibbles may have had a litter of up to eight kittens, each capable of breeding within just four months. This rapid reproductive cycle led to a burgeoning feline population, unimpeded by natural checks and balances—the cats had no predators.
As these feral cats multiplied, so did their impact on the island’s fragile ecological balance. Each kitten grew quickly, learning to hunt and survive in the wild, honing skills that were devastatingly effective against the indigenous species like the Lyall’s wren.
Within just a year of the pregnant Tibbles’ arrival, the Lyall’s wren population had plummeted to non-existence. Unfortunately, by the time the effect these cats had on the birds was fully understood, it was too late. The few specimens previously collected and preserved by David Lyall were sent to various museums as the sole examples of the species. The last known sighting of a live Lyall’s wren was in 1895.
While it is easy to blame Tibbles for the total extinction of the Stephens Island wren, her predatory behavior was natural and instinctive. However, the fault lies with Keeper David Lyall, who inadvertently introduced such a predator into a delicate ecosystem. It was a catastrophic human error that wiped out an entire species.
This story appeared in the
Sep/Oct 2024 edition of Lighthouse Digest Magazine. The print edition contains more stories than our internet edition, and each story generally contains more photographs - often many more - in the print edition. For subscription information about the print edition, click here.
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