Changing Planet

How beloved pets become invasive predators – an interview with Dr. Peter Marra

A Call to Action for the Birds of North America

Of all the human-caused direct mortality threats to birds, cats take the biggest toll, killing around 2.4 billion birds a year. Dr. Peter P. Marra, a leading ornithologist is the co-author, with Chris Santella, of the book Cat Wars: The Devastating Consequences of a Cuddly Killer (Princeton University Press, 2016). The book has been widely reviewed—and fiercely attacked by advocates for free-roaming cats. Grant Sizemore, director of American Bird Conservancy‘s Cats Indoors program, interviews Marra about the book and why addressing the cat problem is such an urgent concern for both bird conservation and public health.

Grant Sizemore: Why did you feel it was important to write this book?

Cat Wars: The Devastating Consequences of a Cuddly Killer. Click on the image for more information about the book.

Peter P. Marra: In spite of ABC’s dedication, the crisis with outdoor cats wasn’t getting enough recognition. The problem continues to get worse and worse, and many people aren’t even aware that there’s an issue—largely because of all the misinformation promoted by those who advocate for free-roaming cats. The book is an attempt to reach as many people as possible with the data and the science so we can reverse this problem.

GS: The media portrays this issue as “cats vs. birds.” Is that accurate?

PM: This is a people problem. Cats were domesticated and spread around the world by people. They become pets or pests depending upon people’s actions. The title Cat Wars refers to the battle created by a small but extremely vocal minority of activists who voraciously attack any science that points to the impact cats are having on wildlife and on human health.

GS: Birds face many hazards, including habitat loss, collisions, and pesticides. How big a problem is cat predation relative to other causes of bird mortality?

PM: We analyzed the mortality rates associated with direct anthropogenic or human-created threats to birds—including building or window collisions, cars, wind turbines, and cats—on a yearly basis. Cats are by far the leading cause of mortality, with around 2.4 billion birds killed per year. Collisions with buildings or windows kill as many as 599 million birds, automobiles kill up to 200 million, and so on. Given the sheer numbers of both common and rare birds that are affected by cats, it’s clear we need to direct a major effort at the outdoor cat problem.

GS: Cats are predators. Many people think it is natural for them to hunt birds. How do you respond to the argument that we shouldn’t try to change the natural order?

PM: Domestic cats are as much a part of the natural order as a cow, pig, or golden retriever. They are not a natural part of any ecosystem on the planet—and people have caused them to spread from the place where they were initially domesticated (believed to be Cyprus) to every place in the world, except the poles. Domestic cats are pets and should be cared for as such—kept indoors or under our control at all times.

GS: Why should cats be treated any differently than other predators, such as owls and hawks?

PM: Owls, hawks, and other native predators occur at low enough densities that prey populations are not overwhelmed. The density of domestic cats typically increases beyond the carrying capacity of any environment, leading to unsustainable levels of predation. Furthermore, domestic cats are not native predators, so our native species have not evolved in their presence, making them even more vulnerable.

GS: Should we distinguish between pet cats that go outdoors and feral cats?

PM: Neither should be allowed to roam free because of the harm they do to others (wildlife and people) and to themselves. Owned cats need to be treated like pet dogs. They should be kept indoors, on a leash or in a catio. Unowned cats, which have no owner to take responsibility, pose a risk to biodiversity and human health, and live dangerous, unhealthy lives. They need to be removed from the environment and put up for adoption, placed in a sanctuary, or euthanized.

GS: Do well-fed cats still kill birds?

PM: They still kill birds and other wildlife. There’s plenty of data supporting this fact. Well-fed cats are known as subsidized predators and kill not for food but likely because it is instinctual.

GS: One of the solutions many cities and states are being encouraged to implement to deal with feral cats is Trap, Neuter, Release (TNR). Is TNR an adequate solution?

PM: The evidence does not support TNR as a viable solution to removing cats from the landscape. The hope was that TNR would provide a no-kill alternative to a euthanasia model for removing cats from the landscape. But TNR fails from a number of perspectives. Ironically, it causes cats to be re-abandoned in an environment where they are vulnerable to harm in the form of collisions with cars, predation by coyotes or raptors, and disease. The cats continue to impact biodiversity and spread disease, and the practice actually encourages more people to abandon their cats.

American Woodcock by Mike Parr

GS: If not TNR, what are the solutions?

PM: There are no simple solutions. We have worked our way into a bind by allowing such irresponsible behavior with an invasive predator. Whatever the solution, it needs to be humane. We first need to put an end to the idea that it’s okay for owned cats to be let outside. For unowned cats the situation becomes more complicated. First, we need to identify the areas where cats pose the greatest risk—to biodiversity and to human health—and are in the greatest danger themselves. Cats need to be removed from these areas immediately. Once they’re removed, they can be adopted, put in a sanctuary or, as a last resort, euthanized.

GS: Cat Wars has been criticized for using the phrase “by any means necessary” with regard to feral cat management. Would you care to comment?

PM: That’s a perfect demonstration of why the title is apropos. That phrase was taken completely out of context. Here’s the complete version:

From a conservation ecology perspective, the most desirable solution seems clear—remove all free-ranging cats from the landscape by any means necessary. But such a solution is hardly practical given the legions of cats roaming the land—as many as 100 million unowned animals, plus the 50 million owned cats that roam—and the painful question of what to do with the cats even if they could be captured.

That last sentence makes it clear that the previous hypothetical is referring to capturing cats with non-lethal methods. One could say that the cat advocates are promoting their position using whatever means necessary, including unethical and deceitful approaches to what is a real problem.

Canada Warbler by Frode Jacobsen

GS: How does the recent study by Doherty et al., which finds that cats have caused far more extinctions worldwide than we previously thought, support the argument of Cat Wars?

PM: It makes the message of Cat Wars even more urgent. A single species extinction is too many. The recent paper reports that cats have contributed to 63 global species extinctions worldwide. Cats are now implicated in 26 percent of all reptile, bird, and mammal extinctions in this, the sixth mass extinction—also known as the Age of the Anthropocene.

GS: A concept called “One Health” holds that human, wildlife, and domestic animal health are all related. How do cats affect the health of the species around them, including humans?

PM: Cats carry and transmit an enormous number of pathogens—from rabies to feline leukemia to Toxoplasma—all pathogens that can impact wildlife, cats, and/or people. Toxoplasma gondii, the protozoan pathogen that sexually reproduces only in cats, has permanently infected over 22 percent of people in the United States and over 30 percent of the global population. Toxoplasma oocysts permanently lodge in human brains and can result in a variety of changed behaviors, potentially even mental illnesses ranging from bipolar disorder to schizophrenia.

GS: Cat owners can help by keeping their cats indoors, on a leash, or in an enclosed space like a catio. What can non-cat-owners do?

PM: Citizens, whether they own cats or not, should demand that towns, counties, and states not allow the presence of cat colonies, and that they make TNR illegal—or at least require cat colonies to be securely enclosed. They could pressure lawmakers to enforce licensing and leash laws for cats. It’s time we treat pet cats like pet dogs.

GS: Cat Wars presents an inconvenient but urgent truth. Are there any similarities between the reaction to the science of cats and the science of climate change?

PM: The pushback and deliberate denial of science by cat advocates is completely analogous to what we experienced with climate change deniers. We have been hampered by so-called confirmation bias, where people believe what they wish to believe, rather than fact. That has left us in difficult environmental and public-health situation that will cost lives and billions of dollars.

GS: What gives you hope?

PM: Nature is resilient—as long as we take action. We hope Cat Wars is that call for action. Given the declines we’re seeing with the birds of North America, removing a threat as significant as cats will give many of these remarkable species a chance to recover.

That’s the encouraging part of the cat issue. We can solve the problem.

Grant Sizemore is American Bird Conservancy’s Director of Invasive Species Programs. He has degrees in Zoology and Environmental Science from Miami University and an M.S. in Wildlife Ecology and Conservation from the University of Florida. Grant has worked toward wildlife conservation through policy, outreach, education, and years of research. He enjoys hiking, birding, and taking care of his (indoor) cat.

Copyright 2017 © American Bird Conservancy. All Rights Reserved.

Ovenbird by Greg Hormel, Natural Elements Productions

Related Voices posts:

Feral Cat Debate: The Case for Large-scale, non-lethal Interventions
Feral Cat debate: Trap-Neuter-Return Is Sound Public Policy
TNR Is Dangerous Both to Cats and to Other Animals
Big Love for Small Cats

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  • KimMarie

    I agree with Dr. Mara that TNR doesn’t work and that people should keep their cat companions indoors. And of course to spay and neuter cats for their well-being.

  • Craig Shapiro

    I couldn’t agree with Dr. Marra more:Cats belong inside, not roaming loose. My cats have been around a while–one’s 15, the other 12–and they’ve never set a paw outdoors. They’re happy, healthy and safe. I’m sure the cardinals, wrens and other birds who frequent my backyard applaud our choice.

  • Catgrrl63

    The solution is so simple–require that ALL cats be spayed, neutered, microchipped, licensed, and kept indoors. I don’t know why people are so resistant to this. Why do they think cats deserve any less protection than dogs?

  • LucyP

    Thank you for this important interview. Letting cats roam not only takes a terrible toll on birds and other vulnerable wildlife, it results in much preventable suffering for cats. Every day, cats are killed by traffic, poisoned, shot, and stolen, among other cruel fates. They are not wildlife and should never be left to roam as if they were.

  • DHK

    It becomes really difficult to have an intelligent conversation of this subject when fear tactics are being used.

    Take this from the article “Toxoplasma oocysts permanently lodge in human brains and can result in a variety of changed behaviors, potentially even mental illnesses ranging from bipolar disorder to schizophrenia.”

    Now consider this from an article published by Cambridge University “Cat ownership during pregnancy was not associated with PEs at age 13 years … or 18 years …. Initial univariable evidence that cat ownership at ages 4 and 10 years was associated with PEs at age 13 years did not persist after multivariable adjustment …. There was no evidence that childhood cat ownership was associated with PEs [psychotic experiences] at age 18 years.”

    Can we just get past the fear mongering and actually discuss this with facts?

  • debtor

    my old cat goes outside and has killed less than one animal per year the last four years. the last animal he ‘caught’ was a baby squirrel that fell from the nest. we followed proper wildlife procedures and he was repatriated with his mother later that day. and quite frankly i wished my cat would catch more tick infested lyme disease carrying mice. they’re all over and everyone but my stoopid cat is more likely to be eaten by a coyote than catch a baby mouse.

  • Liz D

    I agree. Cats, feral or otherwise, should not be allowed to roam freely. They are not to be faulted for their instincts but this problem exists solely because cat owners refuse to behave in a responsible manner. I say this as someone who is a lifelong cat owner and lover.

    Humans can limit the damage by keeping their cats indoors and fixing them to limit the population growth. Cats will live longer and they won’t fall prey to cars, interactions with wild animals and other mishaps.

  • Paula Wilson

    This is Insane!! How can we try to control Nature? Instinct teaches this small creature to hunt. Its purely survival. To impose a way to control nature is an upset to not only to humanity but to the animal kingdom. Lets all admit it. If you were left in a wilderness with the choice of starving or killing a pigeon. THE BIRD WOULD BE DEAD!! The same for cats.

    Sincerely a Hunter
    and Predator.
    Paula Wilson

  • IBrakeForBirds

    Dr. Marra is 100% correct. There seems to be confusion from some people that domestic cats are part of Nature. Well, domestic cats are no more part of nature than dogs, cows, pigs, horses, sheep, chickens or automobiles. Hence, the term DOMESTICATED. We are not trying to control nature, actually, the opposite. We are trying to mitigate the impact on nature from anthropogenic sources, of which the domestic cat ranks at the top of the list as a direct threat to wildlife and biodiversity. There is nothing natural about a well-fed cat needlessly killing, torturing and maiming wildlife.

    Healthy bird populations are essential to human welfare. As responsible pet owners and good stewards of our planet we must take every measure to limit our impact on the planet and the impact of those animals we introduced in places they never belonged and never existed.

  • Gary M. Peebles

    I blame humans for any destruction cats have caused in nature. We are supposed to have the superior intellect. Cats make superb pets but need to be controlled & I don’t think all cat owners are up to the task.

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