Why are pests such a problem for our fauna and flora?
Everybody knows stoats, rats and possums are pests – but what is it exactly that they do? How is it that these tiny creatures can have such a large effect on our flora and fauna?
Stoats are related to weasels and ferrets – which are both also considered pests in New Zealand. These troublesome mustelids have been in the country since they were introduced in the 1880s in an effort to control the rabbit and hare population.
These days, stoats are considered the biggest threat to our birdlife.
Stoats live just about everywhere - in high altitudes, forestland, on farms, in the scrub - so there is nowhere that’s truly safe for birds. Even when stoat numbers are low, they can cause considerable damage to bird populations by preying on young birds such as kiwi. They not only killing nesting mothers, but destroy the eggs as well, which has devastating effects on small populations.
Stoats also eat rodents, insects, rabbits, hares, lizards, hedgehogs, and even fish and crayfish.
Rats were also introduced to New Zealand, and while some were brought here on purpose, plenty have found their way in without being invited as well. There are three types of rat in New Zealand, and all of them are a threat to our beloved ecosystem.
Between them, they eat and destroy a plethora of flora and fauna. Norway rats (also known as brown rats) are quite large and are capable of killing adult nesting seabirds, as well as any other animals that live on the ground. For birds and animals that live high up off the ground, the threat comes in the form of the common rat (sometimes called the ship rat), which is a strong climber and therefore capable of reaching nests in branches. The Pacific rat, which is known as the kiore here, feeds on eggs and chicks as well as insects, lizards, fruits and seeds and therefore removes food sources from our other species.
For now, New Zealand controls the population of rats through poison drops, pest-proof fences and trapping.
Unfortunately, possums were also introduced to New Zealand, and have had a major impact on our native species. They were brought here for their value in the fur trade, and while these pests continue to be hunted for their pelts, their populations are a constant threat to wildlife around the country.
Here, there are no real threats to possums other than humans and they can live just about anywhere that doesn’t receive too much rainfall or is too mountainous.
While possums are a serious threat to our birds, one of the biggest problems with this pest is that they feast on native plants as well. They have been known to demolish entire canopies of trees such as kowhai, rata, titoki, totara and kohekohe by eating the new growth on each tree. As such trees are also homes to our native birds and other wildlife, this also has a flow-on effect that disturbs these lifecycles as well.
New Zealanders who often travel in rural areas will see plenty of possums on the roads, and will often even aim to hit the pests with their cars! Hunters are always on the lookout for possums, and trapping and poisoning are also used to keep the population under control.
Tristan Cullen - Passionate Conservationist