Pest control inside and outside the Sanctuary
Written by: Steffi Künstle, Bio-Security Ranger
If you are a passionate conservationist, you might have a trap – or even a whole trapline – on your property, or you might volunteer with a local trapping group. Your goal is usually to catch as many pests (mostly rats, stoats, and possums) as possible, and hopefully remove enough to give native wildlife a chance to flourish. Even if you are doing a great job, the challenge lies in the constant supply of invading pests into the area you are trying to protect.
Wouldn’t it be nice to just build a fence around the bush you are trying to save and finally lean back and enjoy the peace and quiet? Unfortunately, this is far from the reality. Even a fence can develop holes – especially a very long fence, like the 14 km one at the Brook Waimārama Sanctuary. We are surrounded by mature forest with tall trees just waiting to drop branches in the next storm. Our biggest worry is ship rats, which are abundant in the forest surrounding the Sanctuary. Another concern is weasels. They can squeeze through the smallest gaps and are excellent, agile climbers.
Once an unwanted intruder makes it into the Sanctuary, it’s like finding a needle in a haystack – nearly 700 ha of forest to hide in.
So where would you even start to look? This is why our pest surveillance network and regime look quite different compared to outside the fence. A tight network of over 2700 tracking tunnels is spread across the Sanctuary to detect a single rat. It’s not designed to measure pest abundance, but to detect the presence of even one.
Another challenge is that we don’t know who we are looking for. That’s not just about the type of mammal, but also the individual’s quirks and preferences. Just like us, rats, stoats, weasels, possums and others all have their own likes and dislikes. Outside fenced sanctuaries you can rely on what most individuals of a species are generally attracted to. Inside the Sanctuary, we need to prepare for any personal quirks, or the animal might go undetected and cause damage.
One example is lure preference. We alternate between peanut butter and chocolate spread in our rat traps and tracking tunnels, as some rats prefer nuttier flavours while others have more of a sweet tooth.
As you can see, knowledge is key. But what if we don’t know our intruders well? This is the case with the mysterious weasel (Mustela nivalis). Most research into traps, lures, bait palatability, and detection devices focuses on the more common and larger stoat (Mustela erminea). Yet they are quite different. Breeding biology, preferred prey, hunting style, and social behaviour all vary between the two.
Hopefully, in the future, this overlooked predator will receive more attention from scientists so we can learn more about weasel behaviour and ecology. That knowledge will go a long way in helping sanctuaries stay truly pest-free.
