The Atavism

Sunday, June 13, 2010

Sunday Spinelessness - Protecting the katipo

New Zealand has a pretty benign fauna. We have no snakes, no carnivorous mammals bigger than our little bats and, ever since Haast's Eagle was the driven to extinction, the apex of our natural food webs has been occupied by the karearea. The karearea is the native falcon, and a fierce predator, but it holds no threat to humans. In fact, we only have one native animal capable of doing people any harm, a venomous spider known as the katipō. So, some people were a little surprised to hear the katipo had been added to list of "absolutely protected" animals included in the wildlife act, the same level or protection offered to kiwis and the tuatara.

A female katipō, photograph is CC 2.0 from Jon Sullivan

The katipō's name is a testament to the punch its bite packs, it translates as "night stinger". Actually, the fact the species has a māori name at all sets it apart from our other spider species, the rest of them fall under the name pūngāwerewere. The katipō certainly deserves special recognition, it's a cousin to the black widow and the redback and its neurotoxic venom can produce the same suite of symptoms that make those spiders feared the world over.

Although the katipō's bite is excruciatingly painful, the spider's unique ecology means they seldom bite humans. The katipō is very closely related to the Australian redback (the two can still hybridise) but whereas the Australian species is a generalist that lives in amongst rocks and logs and human debris, the katipō has become a specialist. It builds its web in driftwood and grass on sand dunes. That specialised lifestyle has been the katipō's undoing. In the last hundred years the total area of sand dunes in New Zealand's coastline has decreased by 70%. Not only has most of the katipō's habitat been destroyed in the last hundred years, most of the the remainder has been degraded. We introduced marram grass to sure up dunes that have been disturbed by agricultural and urban development. While that grass does a great job of collecting sand and holding up dunes, it's also very invasive and the katipō doesn't much care for it (preferring the relatively sparse growing native sedge pingao).

Marram grass isn't the only invasive species driving the katipō's decline, a distantly related South African spider called Steatoda capensis has become widespread in New Zealand. S. capensis is another generalist which has not trouble getting by in marram filled dunes and breeds more quickly than the katipō. Add the damage done by recreational activities like quad bike riding to the pressures already listed and you start to realise why there are eight populations of katipō left it the South Island.

There is no doubt that the katipō is threatened with extinction. Adding it to the list of species protected under the Wildlife Act* gives DoC the ability to post scary sounding warnings around remaining habitat, and to prosecute people who willfully damage that habitat. But it's clear from a few comments around the web that not everyone is on board with saving the katipō. Why should we try and hold on to our only dangerous animal? The risk posed by the katipō is really infinitesimal, they aren't living on your downpipes or your living rooms. Even if you wander into the sand dunes you'll have to go out of your way to find a katipō and get it scared enough to bite you. New Zealand's biota is already so depleted by human enduced extinctions, it really would be shamefull to lose another species because of ill informed fear.

* Reading the actual law really does my head in, I think it means for the purposes of that act terrestrial vertebrates are protected unless other wise noted, and inverts are not unless specially picked out.

And a wee note for all the spineless fans (there are some, right?..), next Sunday I will be in a series of airports on my way to the USA for the Evolution meetings in Portland. So, Sunday Spinelessness will take a break 'till early July.

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Posted by David Winter 5:57 PM


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