Helpful gardeners or destructive beasts? Hedgehogs could be the last thing standing in the way of restoring native wildlife.
Most New Zealanders are aware of the current predator problem, with possums, rats and stoats taking the cake for the biggest pains, but what about cute little hedgehogs? Are they really as innocent as they look or are they discretely unravelling the very fabric of our treasured native wilderness? Some scientists went on a hedgehog hunt to find out.
Now imagine the magnificent Ōtamahua: an 80 hectare island smack in the middle of the flooded volcanic crater of Lyttleton Harbour, completely uninhabited by people, but instead populated by some weird mini chickens with fancy hairdos. Back in the day, European explorers hadn’t decimated local wildlife populations yet, and the island was teeming with now extinct koreke New Zealand quails, inspiring them to call this place Quail Island.
Quail Island is a recreation reserve run by the Department of Conservation (DOC) and is being restored to a natural landscape after being formerly farmed. In this programme, the Quail Island Trust and DOC teamed up with a plan to eradicate all exotic pest mammals from the island. Scientists were ready to restore the island to its original splendour by bringing back native insects, lizards and birds, but one thing could be standing in the way of this; the island is dominated by European hedgehogs, and they’re not going down without a fight.
So what’s the deal with hedgehogs? Everyone seems on board with killing every invasive pest mammal out there like it’s a glorified action movie. Oddly, people tend to feel very differently about these freaky little spike balls. Unlike other mammals that were introduced in New Zealand, people love them. This is because they can be seen helping around the garden, happily munching on slugs and snails, which are considered pests. But it’s difficult to understand exactly how these slug-munchers are impacting native wildlife, all we know is that we have gravely underestimated them.
What else is on the dinner menu for these hedgehogs? Aside from the snails and slugs in your garden, they enjoy eating native beetles of all sizes, with a side of millipedes, and then moth larvae and earthworms for dessert. Some have even developed a taste for weta. Hedgehogs also snack on lizards and the eggs and chicks of ground-nesting birds. The hedgehogs are hungry and this is a bad situation for these vulnerable species.
In the distant future, the year 2000, researchers from Lincoln University decided to go to war with the hedgehogs. They did so using their most powerful weapon of all: science and the pursuit of knowledge. They tested their techniques on local hedgehogs before heading into battle on Ōtamahua Quail island. The scientists discovered that they could entice the hedgehogs with a feast of their favourite foods. They tested baits like “kitekat chunky fish cat food” and quail eggs.
(It is worth noting that while the original quail island quails went extinct, they were replaced by introduced California quails, which is convenient because the island didn’t have to renamed.)
Once the scientists got to Quail Island and came face to face with these adorable monsters, they realized that unlike other invasive mammals, hedgehogs were pretty chilled out. They didn’t mind being caught and released again, which meant that it would be possible to remove them from the island without bloodshed. At this point, the animal rights activists may be cheering and the conservationists may be booing. Not killing them means putting them somewhere else. Instead of removing the problem, we are just relocating it.
So the Lincoln researchers got to work running around the island, setting up 53 hedgehog traps. Since there was actually no such thing as a hedgehog trap at this point, they used their smart brains and decided to use traps for other pests which were known to catch hedgehogs by accident. The systematic trials led the scientists to the conclusion that one of the most effective baits for catching hedgehogs was something called “Chunks of Tasti Dinner Dog Roll”. You just can’t make this stuff up. Cat food and peanut butter were similarly popular among hedgehog audiences but surprisingly, quail eggs were not!
Here’s the bad news: hedgehogs had made themselves at home across every kind of habitat on the island. Also, the number of hedgehogs being caught each night didn’t decrease over the course of the 11-day study, leading the scientists to conclude that there were far more hedgehogs on the island than they had previously thought.
The baited traps were placed across all habitat types on the islands, but had much less success around pine and macrocarpa forests. The traps had the most success in catching hedgehogs in grassy and scrubby areas. Could this be the hedgehog headquarters?
This research provided some important insights into the possibilities of eradicating hedgehogs. They figured out which food is preferred and which types of cages work best. They found that the hedgehogs didn’t hang out in pine and macrocarpa forests as much because there weren’t as many insect snacks for them in there.
This study found that live trapping hedgehogs is possible but it is inefficient. The project took 75 hours of work and only managed to remove 24 hedgehogs, that’s 3 hours per hedgehog! The scientists suggested switching to lethal traps because these Houdinis are clever masterminds and they could be escaping from the live traps.
Are there other options? Some have suggested recruiting the help of our best friends, dogs. On another island, dogs were used to find and kill possums. Hedgehogs are smelly and hunting dogs can find them easily without even being trained. The only caveat is that dogs do have to be trained to ignore other species, especially native birds like the precious little white-flippered penguin, another resident of Quail Island.
On the mainland of Aotearoa New Zealand, hedgehogs were found in densities of 5 hedgehogs per 1 hectare of land (which is the size of 2 rugby fields). This is probably not the case on Quail Island because it is so dry, but nonetheless it will take a lot of effort to remove these destructive little creatures.
This is one case study for the eradication of hedgehogs. While the current focus is on eradicating other predator species, may this serve as a warning that we can’t forget about the humble hedgehog when we talk about predator control.
This article was prepared by Master of International Nature Conservation student Lindsay Wood as part of the ECOL608 Research Methods in Ecology course.
Research Article Source: Kavermann, M., Bowie, Michael H., Paterson, Adrian M. (2003) The eradication of mammalian predators from Quail Island, Banks Peninsula, Canterbury, New Zealand. Lincoln University Wildlife Management Report series. https://hdl.handle.net/10182/683
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