Cats and Triffids
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JANE: So, Alan, you were telling me about how cat-friendly New Zealand is, and how
Kel in Her Natural Habitat
your cats wander freely around outside.
ALAN:�� Yes, they go wherever they wish to go. The only fly in the ointment is that they might kill native birds and reptiles which (since New Zealand has no native predators) are quite easy prey. However, my cats mostly bring home rats, mice, and sparrows, along with the occasional blackbird. They’ve almost never brought home anything native.
JANE: That���s interesting ��� and good.�� I was avoiding bringing up the fact that domestic cats are ��� in most parts of the world ��� an invasive species, because lots of people don���t want to face the fact that beloved Tabby is not a natural part of the wilds.�� I���d heard that the kiwi bird was being endangered because it was being hunted by domestic cats.�� Is there any truth to this?
ALAN: Indeed there is. And it isn’t just kiwis ��� we have many unique species, some of which do indeed hover on the brink of extinction as a result of predation.
JANE: Is there anything that can be done?
ALAN: There is a movement in New Zealand to make it illegal for cats to wander unaccompanied. An eccentric millionaire called Gareth Morgan is particularly vocal about this and has put a lot of money into the campaign, so far to no avail.
JANE: Interesting.�� I could see why it would be hard to enforce, although if animals are ���chipped��� there, the way it���s becoming common here (it���s required in Albuquerque, even for indoor-only cats), it would be possible to trace the owners of unsupervised animals and fine them.
If you could catch the cat, of course, and hold it long enough to read the chip.
ALAN: Chipping is a legal requirement for dogs, though not (yet) for cats. However, while cats are certainly responsible for killing some native wild life, cats are actually far outnumbered by rats, weasels, stoats and ferrets ��� introduced predators that live freely in the wild and which are much more destructive of the native wild life than are well-fed domestic moggies.
JANE:�� I���m guessing that rats came via ship, uninvited, but do you know how the weasels, ferrets and stoats got there?�� What were they introduced to predate upon?
ALAN: That’s a bit complicated. In the mid-nineteenth century rabbits were brought to New Zealand for both food and sport. Being rabbits, they immediately had a huge population explosion and got out of control, to the despair of the farmers whose crops they were eating. So in the 1880s, stoats, weasels and ferrets were deliberately introduced in a vain attempt to try and curb the rabbit population. Unfortunately, the stoats, weasels and ferrets seemed to prefer dining on native New Zealand animals rather than on rabbits, and so the rabbits remain a problem to this day!
JANE: Australia had a problem with rabbits, too.�� I recall a truly horrible description of hordes of rabbits dying in the summer drought that was the centerpiece of one of Arthur Upfield���s novels.
How does New Zealand cope with these feral predators?
ALAN: We have a government department (the Department of Conservation, known as DOC) whose brief is to look after the native wild life. To that end, they have put a lot of effort into making many offshore islands predator free, and these are kept as sanctuaries for the wildlife. There are also several areas on the mainland that are enclosed by predator-proof fences which are maintained as sanctuaries.
JANE: Does this technique work well?
ALAN: Yes it does. Their greatest success has been with the black robin. By 1980 there were only 5 black robins left alive, and there was only one breeding pair. The female was called Old Blue. To try and reverse the decline of the robin, DOC implemented an ingenious conservation effort. Every time Old Blue laid a clutch of eggs, they were removed from her nest and given to a tomtit to foster. Then Old Blue, having lost her eggs, would lay another clutch…
JANE: That���s really neat ��� although the tomtits must have been confused.�� How did this work out?
ALAN: Today, there are more than 200 black robins ��� all descended from Old Blue and all living safely on a predator-free island. Old Blue herself lived to be 14 years old, a true matriarch.
JANE: Mother of her race, indeed.�� Of course, without much genetic diversity, they���re still a very fragile population ��� rather like cheetahs.�� Still, given the option, it���s a good effort.
Although I applaud the program to save the black robin, it isn���t really dealing with the invasive species ��� instead, it���s imprisoning the victims.�� I don���t know if any similar efforts have been made in the U.S.�� (although some of our readers might).
Here in the Southwest, where I live, the issue of invasive species of plants is a serious one ��� especially given the scarcity of water. A good example is the tamarisk, also called the salt cedar.�� It was brought to the U.S. in the early 19th century, valued both for its appearance and for its ability to thrive in salty soils.
However, tamarisk is a heavy water user that propagates more easily than many native plants in the bosque�� (that���s what we call the forested areas along the rivers here in New Mexico).�� As a result, there are entire areas that are nothing but tangles of tamarisk.
Currently, there is an effort being made to eradicate tamarisk and replace it with native plants, but it���s not easy.�� Whenever I see them, I���m reminded of your iconic (in that it���s the source of your nickname) SF novel: Day of the Triffids, because, like the creatures in Wyndam���s novel, tamarisk was introduced for many good reasons and proved to be a plague.
Does New Zealand have its own triffids?
ALAN: Indeed it does ��� gorse has been here since the early nineteenth century. Charles Darwin recorded seeing it in 1835 and it was very well established then. It was originally introduced to be used for hedging on farms, but it quickly got out of control. It loves the conditions here and it spreads like wildfire. In summer, the hills are covered with yellow blooms as far as the eye can see, and so are the farmers’ fields. Everyone hates it and millions of dollars are spent trying to control or eradicate it, with little success.
There used to be a wonderful advert on TV for a spray that could be used to control gorse outbreaks. An angry farmer is shown flying his helicopter over his fields and spraying the gorse, swearing and cursing at the terrible weed. But the spray takes a long time to work, of course, and the farmer simply can’t contain his impatience and his anger. So, in a fit of fury, he turns his helicopter upside down and uses the rotor blades to trim the gorse right back to the ground. Then he flies home, satisfied with a job well done. The name of the spray is superimposed on the picture and a voice-over suggests that it might be better to use the spray instead of trying to turn your helicopter into a massive weed-eater…
I haven’t seen the advert for several years now which is a pity. I always enjoyed it!
JANE: Definitely creative and amusing���
There���s a lot more to be said about the subject of invasive species, both in your country and mine.�� Shall we continue next week?
ALAN: Yes, let’s.
