The history of rats in New Zealand

New Zealand


Imagine a life without a single rat or mouse sighting. In fact, consider what it'd be like not to have any rodents in your entire country. Anyone who's had to deal with a rodent problem will think of that as a wonderful dream, but in fact, it was a reality for a while in New Zealand. There was a time when not a single rat, mouse, or other rodent was to be found in the entire country. That's obviously changed a lot over time. And it's undoubtedly going to change a lot in the future. 

To understand where New Zealand is heading we first need to look into a story filled with drama, high expectations, and dashed hopes. We'll see the wishes of the elderly as they look back on their lives. And we'll see the dreams of the youth crushed as they're denied a much-desired pet. It might all sound like the introduction to a fantastic work of fiction, but this is all part of the strange but true history of rats in New Zealand. 

Polynesian rat
“Pacific or Polynesian rat” by Cliff from Arlington, VA / Wikimedia Commons, CC BY-SA 4.0

1280 - The Polynesians Began an Era in New Zealand 

The Polynesians were some of the world's most adventurous explorers. They'd often load up their canoes for amazing treks across vast swaths of the Pacific ocean. These brave explorers would typically bring along everything needed to jumpstart a colony if they encountered promising land. 

The Polynesians were at the same time both idealistic explorers and utterly practical packers. These sailors would often bring along rat species when setting out to sea. This isn't so uncommon in and of itself. After all, rodents have been stowing away on boats for quite some time. What is unusual is the fact that the rat passengers were welcome guests on the Polynesian canoes. This is due to the fact that the Polynesians saw the rat as a good source of both meat and pelts, and it makes sense. Today we're well aware of how fast the animals breed. It's admirably practical for sailors focusing on survival to plan on farming a rat supply. 

Unfortunately, things would get a little out of hand when Polynesian sailors reached New Zealand. The animal that the sailors wanted to thrive did just that. However, things went a little more smoothly than anyone would have anticipated. This brings up a rather surprising fact about the area. New Zealand's ecology didn't have many native land mammals. At this point, the only land mammal in the area was one that also flew around — the bat. Even the bats were quite tiny when compared to what we find through most of the world. The rat's presence there was a huge change to the local ecosystem. 

It's worth remembering just how different mammals, reptiles, and birds really are. The introduction of a predatory mammalian rodent would have been a huge disruption to the ecology. However, it's also important to keep in mind that the rat species introduced by the Polynesians were a little different than what we normally think of. The Polynesian rat is known as Rattus exulans or kiore. Kiore can be destructive predators and pests, but we'll soon see that they're just the beginning of the area's rat-related woes.

1700s - The Legend of the Elusive Waitoreke 

The kiore had about 400 years to settle into its new home. Of course, at this point, people weren't spending much time carefully documenting local ecologies. But that doesn't mean there wasn't a sense of curiosity and adventure amid sailors of the time. In fact, in 1772 Captain James Cook made an odd comment in his ship logs. 

The captain was primarily focused on exploration on behalf of the British Empire. But Cook, like many captains before him, wasn't above putting some extra poetic flourish into his logs. As he entered this region he noted sightings of an odd mammal that seemed to be a cross between rodent and otter. Reports of this creature, soon to be nicknamed a waitoreke, would continue to the present day. 

Sightings of this otter-rat are particularly strange because there shouldn't have been much variety in the mammalian animal life of the region. There were only two land mammals at this point — the bat and kiore. Bats and the kiore are both relatively small. Not to mention that a bat has a very distinct shape. Meanwhile, otters are typically about three feet long. To this day we still don't have any hard evidence of what the waitoreke might be or have been. One of the reasons for the confusion comes from another notable event in the late 1700s. This marks the point when Pākehā settlers would accidentally introduce the Norway rat into the region. The introduction of the Norway rat would begin a mammalian growth cycle that would easily dwarf the existence of a waitoreke within the historical record. If such an animal ever existed, it would soon become just one of a multitude of different mammals in the area. 

house mouse

1800s – Two New Rodents Enter the Historical Record 

We find two huge events in the 1800s. The first involves the introduction of the house mouse. These rodents entered into the area in about as dramatic a fashion as we could imagine. An Australian ship crashed on the shore of Ruapuke Island. The mice survived the crash and quickly made themselves at home in the Aro Vally flat. 

The late 1800s saw the final rodent species enter the area. Nobody's quite sure how the common ship rat was first introduced. The species has a notable talent for making itself nearly invisible on long voyages, but however the rat made its way to the area, it would soon become especially notable. The ship rat is considerably smaller than the Norway rat, but what the ship rat lacks in size it makes up for in tenacity. The ship rat would soon become the most common rodent in the area. 

1900s - The Problem Becomes Impossible To Ignore 

At the end of the 19th century we were left with a region that now boasted four different disruptive rodent species. Saying that rodents were having a devastating effect on the environment would be an understatement. The inclusion of rat and mouse species created an entire army of small, rapidly breeding, rodents that could eat plants, insects and animals. 

Larger rat species like the Norway rat are even big enough to take down adult seabirds. And smaller rat species can use their tiny size and rapid pace to eat up food faster than native species can gather it up for themselves. The 20th century was the point where people finally noticed just how much of the native plant and animal life was falling prey to invasive species. 

The 21st Century – A New Start 

In 2015 New Zealand's government would launch the Predator Free 2050 initiative. The initiative seeks to put an end to invasive predators by 2050. By 2017 the country was particularly intent on solving the problem of invasive rodents, even denying household pets such as hamsters. 


2050 - A Distant but Achievable Goal 

Imagine an old man in 2050. He's laying in bed, remembering how hard his family worked to control the rats in their area. He thinks back to the region's rat history and what has been done within his lifetime. And he's able to really appreciate the fact that in 2050 the long journey of rat history in the area is at an end. 

This might seem like a distant dream. But we do have an example of a similar initiative that achieved full success. A province in Canada, Alberta, is totally rat free, and the hope is that within a handful of decades we'll be able to say the same of New Zealand. If so, it'll mark the end of a dramatic and strange history as various rat species entered and left the country.

There are other rat-free areas across the globe. While eliminating rats may seem like an unachievable task, the A24 trap is a step in the right direction to controlling rats efficiently.

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