Wildlife baddies: The Hedgehog

21:07, Jul 09 2012

(Disclaimer: I'm sure this is going to create a lot of angry, grumpy hedgehog lovin' posts... but prepare yourselves... your friend Mrs Tiggywinkle is a conservation criminal in this country.)

When early European settlers brought their crops to NZ, they also accidentally imported many of the bugs, slugs and insects that came with them - meaning we quickly needed a creepy-crawly cure. It came in the form of a prickly pest-buster - the lovable hedgehog.

So well loved, in fact, for its ability to snuffle up slugs and snails, that guards on trains took boxes of them on train trips and shook them out at every stop to encourage these hedgehog helpers to go forth and multiply. Which they did. Repeatedly. There are now two to four hedgehogs per hectare in most of New Zealand, and in some places twice that. (I once found one under my Therm-a-Rest when I was camping out up the Hunter Valley at the head of Lake Hawea and my two less-than-gentlemanly ranger colleagues had taken the only bunks in the two-man hut!)

So, for the past 100 years we've gone along with the idea that the bumbling hedgehog is some kind of garden helper, slurping up bugs and contributing positively to our lives.  Which in garden terms, may be true.

BUT...

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Be warned, in this country the humble hedgehog is not the do-gooder you've been led to believe.

Instead their appetite for invertebrates is eating our native wildlife out of house and home in some places, they make a tasty lizard lunch out of our reptiles, and they even gobble up the eggs of ground-nesting birds. And if that stuff doesn't disgust you, they have also been seen scavenging on fellow squashed hedgehogs on the side of the road, like some kind of macabre spiky four-legged zombie.

Let's start with their enormous appetites. An individual hedgehog can hoover up bugs and beetles at an incredible rate, sometimes more than a tenth of their weight in a single evening. In addition, the crossover between the hedgehog's diet and that of the kiwi is up to 80 per cent in some places - meaning the hungry hedgehogs are putting kiwi on a crash diet. (One hedgehog was found with 283 weta legs in its stomach!)

It took me a while to get my head around how a stumpy-legged hedgehog could catch and eat a far swifter skink or a gecko, until I remembered the hedgehog's nocturnal habits. At night-time when hedgehogs are hunting, the cold-blooded (more correctly ectothermic) lizards are listless and slow so they make easy pickings for the hedgehog hunter. The 'hogs simply sneak up on the sleeping lizards and start chewing.

Hedgehogs are well known for their love of ground-nesting birds' eggs, but their omnipresence and their impressive fecundity has meant that the sheer number of these animals has had a significant impact on some of our native birds' nesting success. Nest "security footage" over five years in the Mackenzie Basin showed that hedgehogs were responsible for 20 per cent of egg predation of three native braided river bird species, including the endangered black stilt.

It's not that hedgehogs are inherently bad creatures - it's just that like many of the other introduced predators, they are simply in the wrong place here. That's why it might be fairer for our native wildlife to help keep their numbers down by trapping them. Hard to do after a century of Beatrix Potter conditioning, but I reckon if killing hedgehogs can help give our native wildlife a helping hand, then it's worth a go.

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