Reconsidering the Impact of Common Pets on New Zealand's Biodiversity

Buying a pet is always exciting... Pets provide both company and comfort. For a couple, they say it’s the final step before having a child. For families, it provides a great opportunity for enrichment. In fact, there’s a whole host of studies suggesting that owning a pet leads to a longer, happier, and more rewarding life.

It is, therefore, very difficult to write anything negative about pets. It's a positive experience for millions of Kiwis. I myself am a pet owner. So please, don’t for a second assume I come to this subject with any form of malice in my heart towards pets or their owners.

Maybe that’s where we've gone wrong in the past. We all remember Gareth Morgan’s public campaign to eradicate cats. The ‘why’ never really seemed to be a major part of what he spoke about. Or if it was, the narrative associated with the campaign obscured the message. The majority of Kiwis probably assumed he was an eccentric old man, not someone with a message we might want to hear.

How we present things does matter. I’m not advocating harming animals or forcibly removing much-loved pets from families. But I'd like to be responsible as a pet owner and understand the impacts my choices might have on the biodiversity of our country. Until now, this was not a matter I felt strongly about. It wasn't until I began to see patterns of evidence from a wide range of scholars that I felt compelled to question my long-held views about aspects of pet ownership.

So, with that in mind, let's examine three pets you might want to reconsider owning.

New Zealanders are often unaware of the damage their pets cause

Exotic Parrots in New Zealand: A Hidden Ecological Threat

Six percent of New Zealanders own a pet bird. Of those pets, 92% are exotic parrots. In the last 12 months, 331 have found themselves on the loose, either through escape or deliberate release. Though, in reality, those statistics likely underrepresent the problem, given they rely on owners self-reporting their losses.

New Zealand has some odd biosecurity laws when it comes to exotic parrots. It's illegal to import birds but not to breed or own them. Rather belatedly, regional governments are realising this presents a major ecological risk to our country.

Exotic parrots, such as lorikeets and parakeets, can pose a substantial problem to crops. Escapees in Europe have become a major agricultural problem, causing tens of millions of dollars in damage yearly.

The threat does not end there. Our own native parrot, the Kākāriki, is not doing well. Pressures from introduced pests have all but eradicated mainland populations. We have no idea what impact adding another parrot population to our nation would have. Would the remaining Kākāriki be able to survive if they had to compete with another parrot for resources? Would our other native birds suffer similarly?

The best-case scenario is that added competition complicates things for our native flora and fauna. The worst-case scenario is that it leads to unnecessary extinctions. New Zealand has been isolated from the rest of the world for 80 million years. This ecological divide means our native species have evolved limited protections against outside threats. Exotic parrots pose both a disease and parasitic risk to our native birds.

Exotic Parrots are a major disease threat.

Exotic Parrots in New Zealand: A Time Bomb Waiting to Explode

Many of us assume that physical characteristics would reduce the harm an introduced animal can have. How much harm can another parrot do? We have so many anyway. Unfortunately, in many instances, it magnifies the harm. Similar species often increase the risk of passing on disease or parasites. It’s theorised that avian flu may have contributed to the decline of the Huia. Moreover, it’s also believed that parasites from trout may have contributed to the extinction of the NZ Grayling.

Just three years ago, 5% of the worldwide Kākāpō population was lost to disease. Kākāpō, Takahe, Saddleback, and Little Spotted Kiwi are all deeply inbred. Kākāpō have been especially deficient in disease-resistant alleles. Do we really want to find out if diseases from exotic parrots can cross over and impact their populations?

Simulations run by the University of Auckland suggest that there is an almost complete certainty that Alexandrine Parakeets and Indian Ringneck Parakeets exist in large enough numbers to be breeding. Of equal concern is that these two species can hybridise, suggesting an escaped pair of mixed heritage could produce chicks and kickstart a population.

Several regional councils have taken action. Northland has implemented a programme to identify and track down escaped parrots, while Auckland is implementing measures to ban the sale and breeding of birds. Presently, though, there is no nationwide strategy to prevent birds from being bred elsewhere, nor to prevent their escape or deliberate release into the wild. There is also no legislative framework in place to deal with escaped populations that start reproducing, nor a government agency responsible for controlling exotic parrots.

One thing is likely: once they start breeding in numbers, it will be almost impossible to eradicate them. Northland City Council recommends that parrots have their wings clipped to reduce the likelihood of them travelling far upon escape. Given the biosecurity risks at hand, however, the best step forward is likely a nationwide ban on exotic parrots.

A Nationwide ban sounds extreme but could be necessary. 

Exotic Turtles: Red Eared Sliders and the Looming Waterway Crisis

The characteristics that allow exotic species to thrive as pets are precisely the same things that make them a threat to our biodiversity.

Red-Eared Sliders are a species of turtle native to Mexico. They can live for up to forty years, survive even in cold climates, and will eat almost anything. This makes them inexpensive and popular pets. It’s these attributes that also make them one of the 100 most invasive species in the world.

Deliberate and accidental escapees have been present across New Zealand for at least thirty years, possibly even longer. Until recently, this was not thought to be a problem. It was believed they could not breed in our cold climate. Red-Eared Sliders cannot produce fertile offspring in temperatures that frequently dip below 22 degrees Celsius.

New research has not only disproven this, but also suggests escaped females may have been breeding for more than twenty years. Presently, they cannot produce mixed-gender clutches in temperatures under 28 degrees Celsius. Currently, it’s believed they’re already breeding in some rivers in the North Island. Thankfully, though, new additions to the current population are all currently male.

Global warming is projected to change this. Forecasting suggests that summer temperatures will soon rise enough to enable female Red-Eared Sliders to hatch. Turtles have been discovered from Northland to Southland. Once temperatures rise, it seems unlikely we will be able to prevent Red-Eared Sliders from colonising all of our waterways.

Red Eared Sliders are colonising New Zealand

The Danger of Red Eared Sliders in New Zealand's Rivers

This poses a substantial biodiversity risk precisely because they’re so adaptive. Red-Eared Sliders' typical diet consists of plants, small fish, mollusks, small birds and their eggs, insects, gastropods, and small reptiles. A turtle population would be a death knell to the nesting colonies of our wading birds. It would also probably lead to the extinction of whitebait in New Zealand.

The repercussions could extend far beyond there. Turtles can be vectors for disease, extremely aggressive, and compete with native species for food. They can rapidly populate unconnected streams. Recently, one was discovered wandering through a paddock in Canterbury, kilometres from the nearest waterway.

It is imperative that we act before Red-Eared Sliders become established. The Auckland City Council has already moved to ban their sale. However, they have not banned individual ownership. Understandably, as no one wants to come between turtles and their owners. However, a licence for ownership might be a reasonable short-term step. Proceeds from this could contribute towards the control of wild populations.

A hundred and fifty years ago, our native fish, the Upokororo, was wiped out due to the introduction of trout to our rivers. Do we really want to roll the dice and see how another invasive species in our waterways will play out?

Red Eared Sliders could destroy our waterways

Pet Cats are destroying Native Bird Populations

New Zealanders know cats can harm our native birdlife. For the most part, we're aware that cats hunt and kill the occasional animal. Most, however, believe that responsible pet ownership should ensure that our cats don’t cause much harm to native birds.

According to Forest and Bird New Zealand, responsible ownership of a cat is defined as a neutered pet living indoors for the entirety of its life. Moreover, it should wear a bell around its neck at all times, and upon its death, the owner should give serious consideration to not replacing it. These steps should be enough to mitigate the cat from being a threat to native wildlife. Unfortunately, this type of cat ownership is not representative of the relationship most Kiwis have with their cats.

We vastly underestimate the damage a single cat can have. Pound for pound, they're the most efficient killing machines in the country. In fact, cats are considered one of the few apex predators living in New Zealand.

A recent study suggested that New Zealand pet cats are likely to roam far further from home than their owners think is possible. They also kill four times as much prey as they bring home and cause irrevocable damage to local native bird populations.

A 2009 study in Dunedin found that the average cat would bring home 13.6 dead animals a year. This represents nearly fifty animals killed annually. Critically, this was by well-fed cats; feral cats account for much higher kill counts.

Of even greater concern, 43% of these kills are native birds, while another 6% were native skinks and geckos. Pet cats are known to prey on seabird populations and baby penguins.

The impacts don't stop there; cats living in urban areas kill 18 million animals a year. Dunedin studies suggest that within the city, they've driven fantails to functional extinction. Tracking shows fantails repopulating the city from the surrounding countryside are typically killed before being able to establish viable breeding populations.

Pet Cats are leading to localised native bird extinctions

Kiwis and Their Pets: A Call for Responsible Ownership 

It's now believed that New Zealanders own in excess of 1.4 million cats. Despite our best efforts, pet cats are becoming feral cats at an alarming rate, leading to a population explosion. Surveys now suggest that more than 2.5 million feral cats inhabit our country.

Feral cats are notoriously shy, widespread, and almost impossible to eradicate. Cats can range from sea level to 2000 meters altitude. It’s believed that as New Zealand experiences warmer summers, they will shift more and more into Alpine environments. This could cause an ecological disaster. Our Alpine zone is home to many species that cannot survive in the presence of cats. These include, in excess of 160 species of threatened skinks and geckos, as well as Kea and Rock Wren.

There are few places in New Zealand unreached by feral cats. Remote regions, including the Mackenzie Basin, Stewart Island, and even Fiordland, have all become home to feline predators. Recently, a cat was sighted on the Milford Track, shocking researchers. It was not thought possible for cats to scale the rugged mountains surrounding the Milford Track.

Cats have been linked to the recent collapse of eastern Kea populations. They're also believed to have been complicit in the loss of Kokako, Kakapo, and Saddleback from Stewart Island. Feral cats wiped out the Stephen Island's Wren and the Stephen’s Island Piopio in the 1890s. They also slaughtered seventy percent of all known Kakapo in the 1980s. Moreover, recently a single cat killed a hundred native bats in seven days near Ohakune.

Cats have reached even the most remote parts of NZ

Navigating Pet Ownership and Biodiversity Conservation

Despite all this, feral cats are not listed as part of the Predator Free 2050 vision. This reflects the tension between the policy we need and existing relationships with pet owners.

Unfortunately, current research suggests the two are incompatible. Native bird recovery will only happen without the presence of feral cats, and feral cats will exist as long as pet cats do in New Zealand.

If rats and stoats are eradicated without cats, we may see unexpected consequences. Cats may begin to fill the ecological niche of stoats while switching to preying more heavily on native birds. Some short-term solutions that will help involve banning the ownership of cats unless they are neutered, as well as the registration of all pet cats.

At the heart of the problem lies the issue of human responsibility. The number of responsible cat owners is vastly outweighed by the number of negligent cat owners. Until this can be resolved, the presence of pet cats in New Zealand will be a threat to solving our ecological crisis. While the mandatory neutering and registration of all cats may assist in the short term, it is only a stop-gap solution.

Long-term, New Zealanders will need to wrestle with their relationship with cats, both what it is and what it may need to be. For presently, there seems to be no easy way to achieve both a future where our native birds thrive and widespread cat ownership.

How New Zealand chooses to decide that problem will determine the future our native birds are likely to have.

We need to be able to have tough conversations about cats as a nation

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