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‘Don’t let your cat outside’: Q&A with author Peter Christie

American alligator and an invasive Burmese python in Everglades National Park by Lori Oberhofer, National Park Service

  • Journalist Peter Christie has published a new book about the effects that pets have on wildlife and biodiversity.
  • In addition to the billions of birds and small mammals killed by free-roaming pets each year, the wild pet trade, invasive pets, disease spread and the pet food industry are harming biodiversity and contributing to the global crisis.
  • Christie calls the book “a call to action,” and he says he hopes that humans’ love for their pets might extend to wild species as well.

The statistics capturing the effects that pets have on wildlife are mind-boggling. Cats in the United States alone kill at least 1.3 billion birds and up to 22.3 billion small mammals a year, according to a 2013 study in the journal Nature Communications.

Cats and dogs “are now the most abundant carnivores on the planet,” journalist Peter Christie says. Despite being a generally well-fed lot, these animals’ basest instincts often prevail when they’re allowed to roam free in the wild spaces around our homes, hiking trails and beaches.

But the impacts don’t stop there. In his new book, Unnatural Companions: Rethinking Our Love of Pets in an Age of Wildlife Extinction, Christie examines not only the rampages of the predators that warm themselves on our hearths, but the far-reaching tendrils of the wild pet trade, the pet food industry, and the contentious politics that often dictate our approach to solving — or not — a significant piece of the puzzle of the global disappearance of species.

A 2019 report from the U.N.’s Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) cautioned that 1 million species of plants and animals faced possible extinction. Other research corroborates the scale of those numbers. A 2017 paper in the journal Proceedings of the National Academy of Sciences found that almost one-third of vertebrate numbers are on the decline worldwide.

Domestic cats kill billions of small mammals and birds every year. Image by Stiopa via Wikimedia Commons (CC BY-SA).

Humans’ fondness for animal companions is partly to blame, Christie says in an interview with Mongabay. The book chronicles his reporting on the issue, from the swampy Everglades in the U.S. state of Florida to an ecological park in Mexico City to cities in his native Canada. Along the way, he sketches out a unique web of characters: scientists dueling over the sanctity of life, passionate pet advocates, and government agents. The debate is contentious, in some cases involving attacks on science that mirror those by Big Oil or Big Tobacco. And solutions, it seems, require a delicate touch with the part of the human psyche that makes us so fond of the animals we share our lives with, while also conveying the urgency necessary to save the diversity of life on Earth, including ourselves.

Christie writes that he would prefer his book to be a “call to action” rather than a screed condemning pet owners for their choices. After all, he’s no stranger to the joy of pet companionship himself. His relationship with his dog Maggie serves as a touchstone throughout the book, the bond stretching beyond the home office they often share while Christie is working.

“None are more aware than pet owners of the mystery and satisfaction behind our ties to other species,” he writes. “This vast pet-owning community of the world’s greatest animal lovers — my community — is essential to solving these problems. My wish is for this book’s readers to finally recognize our place as pet keepers and animal lovers as the best hope for a new conservation nation. In times of extraordinary environmental change and with a wild world more delicate than ever, nature — the nature to which our pets and other animals belong — needs us.”

The interview was edited for length and clarity.

Unnatural Companions was released May 21. Image courtesy of Island Press.

Mongabay: Where did the idea for Unnatural Companions come from?

Peter Christie: I had been aware of the cats-versus-birds controversy that has been ongoing for many years and that recently flared up following [conservation scientist] Peter Marra’s article in 2013 and subsequent book. It’s a live issue in the conservation community where I work regularly. And then I was hired by Maclean’s magazine to write a short article about Canada’s decision to ban the import of pet salamanders in an effort to stem the spread of a fungal disease that was ravaging parts of Europe as a result of the pet trade. It was that sort of coincidence, putting those things together, that made me think about the wider picture. After doing a review in the literature, I realized that nobody had done a big picture, a wider review of what pets were costing in terms of the conservation consequences. That’s when I began to put all the pieces together and discovered the startling fact that they’re a significant factor in biodiversity loss.

Can you give a sense of the scale of the problem with pets and the effects on wildlife?

The short answer to that question is enormous direct and indirect effects. If you look at the approximately [estimated] 500 vertebrate extinctions that have happened in the last hundred years, pets and pet keeping has been treated as a main cause in probably between a quarter and a third of those. That’s a significant number of extinctions. The number of species that are now listed as threatened on the IUCN Red List, hundreds of them are being menaced by pets. For some of them, pets are the primary threat to the species’ continued existence — 63 extinctions due to cats, 11 due to dogs that we know of as the primary cause, 90 or so presumed and confirmed extinctions of frogs as a result of chytrid fungus spread probably by pets. The numbers are really quite extraordinary, and that doesn’t even count the trade in parrots and reptiles that’s devastating those populations as well.

I most often think of cats as taking a toll on wildlife. But as you point out, there are other effects that pets and pet ownership have on wild animals. What are some of those other effects?

The ones I deal with principally in the book are pets, as you’ve mentioned, as predators, the common ones being dogs and cats. They are now the most abundant carnivores on the planet. But there are other effects and impacts that have been equally or more devastating. Invasions is a big one: The spread of animals around the world is disrupting ecosystems and having devastating effects on native wildlife by non-native wildlife. The pet trade raiding of jungles and rivers and other waters to take exotic pets out of the wild and into the pet trade is having a profound effect. We have the impacts of the pet food industry on forage fishes and the protein production through farming that’s devastating habitats. Finally, one I touched on earlier, which was the spread of pet-borne diseases to wild animals.

Feral street dogs in Russia. Image by Andrew Currie from Toronto, Canada via Wikimedia Commons (CC BY-SA).

As you mention, there’s been research out recently showing the scale of these problems with billions of small mammals and birds affected. Still, you also say this is something that we’ve known to one degree or another for a relatively long time. Has there been any progress toward dealing with these issues, or are the problems just getting worse?

That’s a good question. It would be fair to say that it’s getting worse everywhere. But some places are more responsive than others. Australia and New Zealand have taken some fairly drastic, and some argue draconian, steps to eradicate predatory invasions by pets. They have bounties on feral cats in Australia, for example, and they have invested a lot of money and time into a plan to eradicate feral cats and foxes from the coastal islands within the next few years. The U.K., on the other hand, they are much more hands-off in terms of acting to try and stem feral cat predation. Similar to the United States, it’s much more of a contentious issue. So it really depends on the jurisdiction and whether or not that steps are being made.

But, I think there’s some reason for optimism. In the United States, at least, there are trap, neuter and release programs that people some people swear by, and those are being frequently implemented.

The feral cats example seems to have been politicized in a way. You’ve got people on both sides of a rather contentious issue.

I think this goes to the heart and the purpose of the book. It is contentious, and I think battle lines were drawn early in this whole debate. The scientific community simply stated the facts initially. I suppose the underlying messages about control and eradication may have been quietly in between the lines. But many groups reacted adversely, and some battle lines were drawn. In this book, I really wanted to point out the issues faced by conservation because of pet ownership, but I wanted principally to try and find a way, or at least argue for a way, for pet people and conservationists to come together under a common banner of caring for these sentient vertebrates that give people such pleasure, whether they’re cats in their houses or [the wildlife that people watch]. I’m trying to find a middle ground.

The issue really has been polarizing one and, and, you know, Pete Mara, as much as I love him, some of his [views] on extermination [make] a lot of biological sense in many respects. But that may be missing part of the sociological picture that we need to consider if we’re going to move forward with effective conservation measures on these touchy issues.

Marc Bekoff, as you point out in the book, has interesting ideas on what he calls “compassionate conservation.”

Dr. Bekoff and others like him [share] a view that all sentient life is sacred, and that, as he would say, simply killing is off the table. Most conservation biologists, I think, would respond that, while laudable, that’s a really difficult program when you’re facing a problem like these invasions of pets as non-native invasives in these ecosystems. These places get completely disrupted. It would be like responding to coronavirus without any attempt to eradicate the virus. We have to do what we can to mitigate the problems because it really comes down to a life for a life.

A domestic or feral cat with a rabbit. Image by Eddy Van 3000 via Wikimedia Commons (CC BY-SA).

One of the emblematic examples seems to be the Burmese pythons in Florida’s Everglades, and the significant impacts they’re having there. But you found that they’ve come up with an interesting solution to that problem.

Beginning back three decades or so, people began to notice the appearance of exotic reptiles, in particular, Burmese pythons, in Everglades National Park. A few sort of turned up here and there and started to raise concerns. Shortly thereafter, they noticed that these animals were actually growing quickly and quite large. Now, a few decades later, there are hundreds of thousands and perhaps close to a million large Burmese pythons thought to be occupying Everglades National Park and waterways throughout the Everglades in South Florida. This has just devastated mammal populations and even other reptile populations throughout the Everglades, basically transforming the top predator from the normal alligator to these huge pythons.

Authorities began by putting a bounty on these things. But nowadays, the park, as well as the South Florida Water Management District that’s responsible for the restoration of the Everglades, hire these guys, these basically freelance snake hunters who go out into levee roads of South Florida and drive up and down looking for evidence of snakes. They run out into the marsh and wrestle them when they see them. They dispatch them, and they get paid for their time and paid for the snakes they bring in.

The book draws connections between these issues with pets and the global biodiversity crisis. How closely tied together are these issues?

If you think about biology as this big machine that gathers up the sun’s energy and converts it into a usable form that creatures and eventually people use to thrive and survive on the planet, the research has essentially shown that more species are just better at handling, managing and converting the sun’s energy, right from its initial capture of life by plant life to its translation into other forms of biological energy through the consumption of plants and then the consumption of plant eaters by others. The more species that are doing that, the more efficient it becomes — not just additively, but in fact, when you add different species, they actually can make the whole system more efficient. There are cumulative effects to the efficiency in this sort of biological process, so more is better in terms of keeping the world thriving and full of energy.

What this means on the ground is essentially, a forest with more tree species will give you a better yield than a forest with a single tree species. As you can see, in terms of feeding people or creating wood for building or fires, this can be fundamental in terms of translating biology into usable resources that humans need and rely on.

The wildlife trade in the book plays a pretty prominent role. What’s the scale of that problem globally?

The wildlife trade is many billions of dollars in size, and the illegal trade alone is considered second only to illegal narcotics in terms of the amount of money and people and resources involved in it. The pet trade of course is a fraction of that because of course much of the wildlife trade is the trade in body parts for medicines.

But nevertheless, sensitive creatures like rare parrots, other birds, mammals and reptiles are really susceptible. In the bird world, for example, work has been done in Indonesia that, of the once-common native birds, 14 of these birds are now really facing annihilation, and pet keeping has been attributed as a main threat for 13 of them. So it’s a significant piece, particularly for rare, exotic creatures. Rarity becomes a thing that adds interest and value in the marketplace. So unfortunately, the forces that inspire people to trap and trade in animals are also the same ones that are the result of our poor conservation of these animals, so it’s a bit of a cycle.

A school of sardines in the Philippines. Image by TANAKA Juuyoh (田中十洋) via Wikimedia Commons (CC BY).

How about the pet food industry? What are the issues there?

There are two principal issues I touched on in the book. One is the beef cattle industry, which is a large part of why we’re losing tropical forest areas in places like the Amazon where these areas are being cleared for cattle ranches just to feed a prodigious appetite for meat around the world. It so happens that the pet food industry consumes about a third of meat-based protein that humans eat in North America at least. That’s a significant amount. Obviously, a lot of that would be material that’s not prime meat that we eat. A lot of that would be discarded anyway. But even so, there’s a continuing trend in giving pets choicer protein sources — muscle flesh and those kinds of things. So it’s actually a growing problem. [Land-use change] required for [cattle ranching and feed crop farms] is the number one cause of biodiversity loss around the world.

The second one is the forage fish issue. The forage fishery is the largest fishery in the world. It’s the fishing of small anchovies and other small schooling fish that have a capacity to produce a lot of young and then feed a lot of creatures including people. We eat mountains of these fish.

However, larger and larger numbers of forage fishes are being used to furnish our pets with protein. There’s obviously cat food, but fishes are also used for fish oil that’s sprayed on kibble and for many other products related to pet nutrition. Just the sheer amount of fish that’s going out to feed these animals is significant and having a dramatic impact on forage fishes. How dramatic is somewhat of an open question because forage fish numbers cycle dramatically, but there is evidence that overfishing of the forage fishery is having a downstream effect on animals such as seabirds that rely on these fish to feed their young. These seabirds are among the most threatened birds as a group in the world, so it’s a potentially significant phenomenon.

You mentioned the spread of diseases as a result of keeping pets. How does that relate to the current COVID-19 pandemic?

In two ways. One is the obvious: the science is becoming very clear that these coronaviruses arise from wild animals and other creatures. They arise in the case of wildlife principally because we’re careless. Through loss of habitat, we’re squeezing these creatures into smaller and smaller areas where these diseases can propagate even more rapidly. Then, we’re going into these places and trapping and bringing these animals out or interacting with them because we have roads through and other developments going on. We’re more in the face of these species. I think the authors of last year’s IPBES nature survey suggested it was a perfect storm for these viral transfers. Obviously, pet ownership is complicit in this, particularly because, of course, the trapping within the forest is part of this exotic animal trade. It brings these animals to markets and makes this potential a lot greater.

The flip side, which is a side that I’m interested in, is that people are really enjoying their pets in this period. They’re being isolated with their pets and spending time with their animals and gaining to a new eye to appreciating what it means to have an animal for company and to share their existence with another sentient creature. The upside, I would hope through the book, is that these pet owners who are aware of this at least are in a position to be more positively inclined to think about life in a similar manner as other creatures on this planet that make it a less lonely place. Perhaps saving them would just in itself be a positive emotional benefit. That positive emotional benefit in turn would ultimately result in the lowered risk of these kinds of disease outbreaks and spread.

An American robin (Turdus migratorius), common prey for house cats in the United States. Image by Mdf via Wikimedia Commons (CC BY-SA 3.0).

What are some of the things that pet owners can do minimize the impact that pets have on wildlife and biodiversity?

We talked about predatory animals — keep your dogs under control and on a leash when you’re on a beach or in a wildlife area. Don’t let your cat outside. I hear the argument many times that, “My cat has to go outside. It’s gonna go crazy if it’s inside.” Then you can use bells and cat bibs, which do cause reductions in the success of these cats preying on birds and small mammals. You can pay attention to the pet food you’re buying to make sure it’s been sourced properly. Check with your veterinarian on pet nutrition. You don’t need excessive amounts of protein, particularly for dogs, in the food that you buy. Those kinds of things can all make a difference.

If you are buying exotic pets, you want to make sure that you’re not just going for rarity as a commodity. You want to know where the animal is sourced and whether you can verify this sourcing. Those kinds of things can ultimately make a difference.

I think, ultimately, we need pet owners to flex their muscles for the industry and see if we can get a sort of certification system going so that the industry itself is doing a lot of this policing, in terms of pet foods, where pets are sourced and how pets are disposed of. It’s a huge industry, more than $160 billion around the world. It’s a significant player and growing fast. It would be pretty straightforward if they could be inspired to put in place some of the controls to get these conservation measures in order to lower the biodiversity costs.

I don’t know how Pollyanna it is, but in a perfect world I’d like to find a way to convince pet owners that we’re all on the same side. That would be a really big first step in terms of moving solutions to this problem forward.

I’m acutely aware of the danger of alienating pet owners, and it’s such a big population — about two-thirds of American households. That’s a significant number. If we could just convince even a few of them that we share the same passion, we may make a lot of inroads in terms of being receptive to restrictions that put biodiversity losses at the top of the priority list.

Banner image of an American alligator and an invasive Burmese python in Everglades National Park by Lori Oberhofer, National Park Service via Wikimedia Commons (Public domain).

John Cannon is a staff features writer with Mongabay. Find him on Twitter: @johnccannon


Ceballos, G., Ehrlich, P. R., & Dirzo, R. (2017). Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines. Proceedings of the National Academy of Sciences, 114(30), E6089-E6096. doi:10.1073/pnas.1704949114

Loss, S. R., Will, T., & Marra, P. P. (2013). The impact of free-ranging domestic cats on wildlife of the United States. Nature Communications, 4(1). doi:10.1038/ncomms2380

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