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Many cat owners are familiar with the "gifts" their feline friends are fond of giving, but if left unchecked, this behavior can be devastating.

Hosted by: Hank Green

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Sources:

https://www.notornis.osnz.org.nz/system/files/Notornis_51_4_193.pdf
https://www.allaboutbirds.org/the-obituary-of-the-stephens-island-wren/
http://www.oiseaux-birds.com/page-family-acanthisittidae.html
https://www.gns.cri.nz/Home/Our-Science/Earth-Science/Regional-Geology/The-Geology-of-New-Zealand
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4855539/
https://www.doc.govt.nz/nature/pests-and-threats/animal-pests/
https://www.australiangeographic.com.au/topics/wildlife/2017/10/the-weird-flightless-birds-of-new-zealand/
https://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10696945
(Intro)

If you've ever had a cat that lives outdoors, then you probably know the grisly, if well-intentioned, gifts they can be fond of giving, and if you think about all the cats loose in a city or a country, that quickly adds up to a lot of dead wildlife.  In fact, many conservationists are concerned that if left unchecked, the world's cat population could eat whole species to extinction, and they have a good reason to be worried, because that has happened before.  

Back in January of 1894, 17 people, including a lighthouse keeper named David Lyall and his family, moved to Stephen's Island, a small speck of land about 1.5 square kilometers in size nestled between the North and South islands of New Zealand.  Not long after, a lighthouse cat named Tibbles brought the humans a housewarming gift, a dead bird.  Now, Lyall was an avid naturalist and he'd never seen any bird quite like it, so he sent it off to a scientist in Wellington, the capital of New Zealand, to have it identified.  

Tibbles soon brought in another one and another, because, you know, cats.  Also because the birds had a trait that made Tibbles' job all too easy: they were flightless.  Scientists were able to deduce this from the shape of the breastbone and the short wings on the specimens which could only have been good enough for the occasional burst into the air, not prolonged flight, and this isn't unusual in New Zealand.  Many of the island's native birds lack the strong pectoral muscles needed for sustained flying and that's because the country's islands have been separated from other landmasses for the past 80 million years or so, and aside from a few dinosaurs very early on, they haven't had any big predators, so the birds that made their way could finally relax, kick back, and hang up their wings, confident that their flapping and fleeing days were over, in an evolutionary sense anyway.

Over time, evolution took its course and New Zealand became home to a whole flock of flightless birds like kiwis, takahe, and most of the birds in the family scientists would place the dead gifts from Tibbles into, acanthisittidae or "New Zealand wrens".  By the end of 1894, six months or so after the first specimen sent by Lyall, scientists in London declared the birds a new species, and scientists worldwide were eager for specimens of their own to display or study.

They would not get them, though.  Within a year or so of its discovery, the Lyall's wren, as the bird had come to be known, was declared extinct.  There were once several species of New Zealand wrens living all over the country.  Now there are two, and just like the Lyall's wren, the others that died simply couldn't survive their new neighbors, especially the furry ones.  

It all started with rats, which made their way to New Zealand aboard Polynesian canoes that arrived in the 13th century.  A few centuries later, Europeans and their stowaways and pets also made New Zealand home.  By the late 18th century, introduced rats, cats, stoats, and goats were either eating or outcompeting many of the native feathered fauna.  Dozens of bird species disappeared altogether, and by the 1890s, the Lyall's wren was down to one last population living on Stephen's Island.  Then came Tibbles.

Of course it's unfair to blame Tibbles alone for the total extinction of the Lyall's wren.  It's not like she killed the ones that once lived other islands and it's likely that she wasn't the only culprit on Stephen's Island either.  In the early 2000s, scientists combed through multiple sources, including the archives of the Natural History Museum in London and found evidence that by the late 1890s, the island was swarming with killer kitties.  These were probably Tibbles' offspring, as records suggest she may have been pregnant when she arrived in 1894 and she might not have been the only cat brought over, and within a few years, we know that there were many cats killing, like, everything on Stephen's Island.

Once it became clear that they were endangering the island's tuatara, a reptile found only in New Zealand, a one-shilling bounty was put on each of their furry heads.  Accounting for inflation, that's the equivalent of several US dollars per cat.  By 1912, over 700 cats had been killed and it still took another 10 years before the island was once again feline free.  

So in the end, the extinction of Lyall's wren probably wasn't because of just one serial killer cat.  It was more of a feline family business, and even then, the cats had some helping hands.  Records show that Lyall sold many of the wrens Tibbles brought him, at least 10 birds in the first year, to buyers that then sold them to private collectors in museums, and as news of the bird scarcity grew, their value only went up.  Tibbles and her descendents may have clawed and bitten their way through every Lyall's wren they could find, but they did so under the watch of several naturalists who were too absorbed in taxonomy to stop the carnage, and the extinction happened so rapidly that we know very little about the bird's behavior other than that it might have been nocturnal.

Between all of the killing and shipping and dissecting, it seems like everyone forgot to actually study the bird while it was like, you know, alive.  It's too late to go back and change what happened, but stories like these are why we are now much more careful about the species we transport around the world, because they can and do wreak some serious havoc, especially when we let them.

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