Land of giants

WHY NZ CRITTERS LIVE LARGE
Last updated 13:16 02/11/2012

The moa and the Haast's eagle might be gone, but plenty of giants remain in Aotearoa.

New Zealand plays host to a range of invertebrates that display all the characteristics of island gigantism.

Island gigantism occurs when in the absence of constraints (such as predators), native species grow larger than in other places.  In New Zealand, the 'land without teeth' where wildlife evolved for 80 million years without any terrestrial mammals (except for the bats), invertebrates were in a (mammalian) predator-free nirvana, having the perfect opportunity to grow enormous. And many of them did.

Take the giant land snails, mostly of the Powelliphanta and also Paryphanta genus. These snails can grow to an enormous size, with some Powelliphanta snails reaching the size of a hamburger.

Mokihinui giant snail (photo: DOC)

Of course being a giant snail requires a giant appetite, which is why the carnivorous giant snails tend to like to suck worms up out of the soil like spaghetti (for your entertainment, here is that amazing video of it again!).

What of course is the most fulfilling meal for a giant snail is a giant worm.

So this one is probably a good enough feed for a giant snail...

giant earthworm (Bay Bush Action) (photo: DOC)

The 'North Auckland worm' was found on Little Barrier Island, as well as other islands in the Hauraki Gulf, and even turned up near Warkworth recently. They can grow to 1.4m long, and over one centimetre thick.  They are very rarely seen, preferring to hang out under the ground, and also exhibit bioluminescence, meaning they glow in the dark. Apparently you could read by the light of one of our giant worms - making them extra cool in my book!

Probably the most famous giant invertebrate we have in New Zealand is the giant weta. One female giant weta from Little Barrier/Hauturu weighed in at 71grams and gained the title of the world record holder for heaviest insect on earth.

Giant weta (photo: DOC)

We have eleven species of giant weta in New Zealand, and in my experience they are more docile than the more common tree weta.  Giant weta also have this amazing over-constructed look about them, making them almost cartoon-like in their appearance.

Giant weta are the classic example of species growing larger in the absence of predators, and in New Zealand's case, taking the the ecological niche that rodents fill in other countries. Problem was, when rodents came to Aotearoa, they dined out on the weta, relegating many of the gentle giants to offshore islands (or in the case of the Mahoenui giant weta - tucked inside dense gorse bushes, like in this video).

The gigantism of our native invertebrates has always fascinated me and I've been lucky enough to see and hold giant weta, robust grasshoppers, leaf-veined slugs and kauri snails.  Their awesome ecology is part of the reason I'm so passionate about predators (the impact they have) and giving our native wildlife a chance to thrive without introduced mammals.

What about you guys? Have you ever seen any of our miniature giants? Which ones? I'd love to hear about them.

» Please feel free to email me to send me your questions, feedback, ideas or photographs for In Our Nature blog posts. You can also join the In Our Nature Facebook page.

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