Research Problem Animals: Abundant Deer and Feral Cats

Problem Animals: Abundant Deer and Feral Cats

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By Anna Peterson

What Is the Problem?

Humans have always been ambivalent about other animals. We generally appreciate creatures who provide food, income, companionship, or entertainment and condemn those who cause physical danger, economic loss, or inconvenience. Their measure, in other words, rests largely on their contributions to our own interest. On the face of it, environmental ethicists should reject this anthropocentric approach, because despite our disagreements, we mostly agree that nature has value in and of itself, not just insofar as it makes life better or easier for humans. However, it turns out that like most people, we are selective about aspects of nature they like. Most environmental ethicists share an ecocentric perspective which prioritizes intact ecosystems, wild landscapes, and rare species and which measures individual creatures by their contribution to the greater good. Aldo Leopold summarized the standard that still dominates environmental ethics: “A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise” (Leopold 1949, 262). Most environmental ethicists judge animals by this rule, along with the whatever other “things” Leopold had in mind. This means that some traditionally reviled animals, like wolves, bears, and alligators, are good, while others – especially ones who are non-native, “invasive,” or feral – are wrong.

There are many types and degrees of problem animals. Some seem relatively innocuous, especially wild species who extend their range into new areas, such as coyotes or armadillos. Meanwhile, others are the targets of heated rhetoric and lethal action. Of these, some have few allies and can be demonized and killed without repercussions, such as Burmese pythons in South Florida or zebra mussels in the Great Lakes. In this paper I explore two which pose particularly complicated political, philosophical, and public relations dilemmas: white-tailed deer and free-roaming (“feral”) cats.

Each is problematic in a particular way. White-tailed deer are native to most of North America, and thus good in the right numbers, but bad when they become “overabundant” in a particular place. Free-roaming cats are intrinsically problematic for many environmentalists because they are domestic (“introduced”) predators who do not “belong” in wild landscapes. For both animals, heated debates rage over two key issues: their impact on wild ecosystems and the relative effectiveness of different management options. I explore these discussions here in order, first, to shed light on the ethical issues at stake regarding deer and cats, and second, to reflect on the often inconsistent and oversimplified ways environmental philosophers think about animals generally.

The Unwelcome Native

Presently as many as 30 million white tailed deer (Odocoileus virginianus) live in the United States, up from a low of around 300,000 in 1930. While many Americans see deer in positive terms – symbols of wild nature or perhaps relatives of Bambi – they are less beloved by others, particularly suburban gardeners and wildlife managers. From an environmental perspective, the problem is that overabundant deer destroy native plants, contribute to “regeneration failure” in native forests, and compete with less common wild animals by reducing their food sources (Levy 2006; Tilghman 1989). One author summarizes: “Deer overabundance has become such a common problem in many parts of North America that it probably will represent one of the greatest challenges facing wildlife professionals during the next millennium” (Warren 1997, 213).

To address this challenge, many conservationists support regulated deer hunts. However, pro-hunting policies raise a host of political, moral, and public relations issues that are just as challenging as the ecological problems. In particular, debates about hunting often pit environmentalists, who support ecologically “therapeutic” hunting, against animal welfare advocates, who prefer non-lethal management options (A. Peterson 2013, Varner 1998). This political division is reflected in the debate among environmental ethicists, who mostly agree that it is morally acceptable to sacrifice individuals for the greater ecological good, and animal ethicists, who assert that it is cruel to kill complex, sociable, and intelligent animals who have done nothing wrong except exist in their natural habitat.

Complicating the conflicts between environmental and animal advocates is the fact that the scientific evidence, to which both sides appeal, is not conclusive. Science weighs in on two specific questions: How much environmental damage do deer cause and how effective are various management solutions? (This foreshadows conflicts over outdoor cats, as I discuss later.) Proponents of hunting and other lethal approaches argue first, that deer cause significant harm to native forests, wildflowers, and other animal species and second, that regulated hunts are the best way to reduce the population to a more sustainable level. However, people opposed to “culling” assert that the data is not clear-cut on either point. They note, first, that it is difficult to isolate the damage caused by deer as a single species in complex ecosystems which are subject to many other stresses, mostly human-caused. Second, it is equally hard to assess different management options, including not only hunting but also contraception and relocation, because such projects (and the studies analyzing them) vary widely in geography, scale, and methodology.

Opponents of hunting as a solution to deer overpopulation often point out, further, that deer overabundance stems from the removal of predators, especially wolves and cougars, and development in former woods and meadows. All of these, obviously, result from human actions. Environmental thinkers sometimes acknowledge this fact but almost never dwell on it in their reflections on problem animals. Rather, they frame the animals themselves as the problem. The historical context may sometimes (though not always) be irrelevant to practical solutions, but as ethicists it ought to give us pause. Human culpability cannot be irrelevant to our reflections on the fate of forests and deer.

This leads to my next theme, the possibility that in thinking about problem animals, ecocentrism can become a cover for human interests. What I mean by this is that arguments about the “beauty, integrity, and stability” of ecological communities may confuse the interests of humans (even environmentally concerned ones) with the interests of nature. As an illustration, we can turn to Garrett Hardin, who discusses deer in the context of his larger “lifeboat” ethic:

It is easy for Homo sapiens to be impartial in managing another species. If a population of deer exceeds the carrying capacity of its domain, the intelligent human manager reduces the population. With overcrowding, it becomes compassionate to kill. We can agree that life is good, but one can have “too much of a good thing,” as John Sparrow (1977) has eloquently argued. If deer were fully conscious of their own situation, we would be naive to expect any individual animal to seek its own death; yet the interests of deer-posterity would be well served by a thinning out of the present generation, whether this is done by wolves or hunters (Hardin 1979, 336).

Pace Hardin, it is in fact not easy for Homo sapiens to be impartial. We always have a stake in ecological conflicts, and our interests are rarely identical to nature’s. Even as we agree that ecological complexity is good, we must also keep in mind that “it [is] not necessarily good for humans and for all aspects of nature,” in the words of James Gustafson (1994, 44). Writing from a theological perspective, Gustafson insists that the nature that God made is both good and not always partial to human interests. Hardin, in contrast, assumes that his is a “God’s eye view,” as though he were not situated in the midst of the problem and lacked a stake in its interpretation and resolution. There is a fundamental contradiction in the ecocentric position that, on the one hand, “life is valuable to the extent it contributes to biotic integrity or that all life is equal,” and, on the other hand, tacit acceptance of “the need to rank humans higher than their contribution to biospherical integrity,” as M. Nils Peterson writes (2004, 316). Because of our self interest as a species, environmental philosophers (with the benighted exception of Miss Ann Thropy) do not ever call humans “too much of a good thing.”

In sum, the real threat to forests is not deer, but humans. Since we hesitate to advocate the removal of humans from sensitive ecosystems, we blame other species and call ourselves “intelligent managers.” I am not proposing that we remedy this inconsistency with draconian measures against invasive humans. For a start, the humans who would suffer in such plans are very rarely the ones who are really to blame for environmental problems. Accepting responsibility will not magically lead to practical solutions, but nonetheless we ought not to pass lightly over our own culpability when we talk about deer overabundance.

The Cuddly Killer

Like white tailed deer, free-roaming cats are a frequent topic of debate among wildlife managers and conservationists. The problem, again, is that they damage ecosystems, primarily by killing native wild birds, rodents, and reptiles. Unlike deer, however, cats are not native wild animals. Many environmental advocates consider them merely another invasive exotic with no philosophical or moral significance apart from their negative impact on ecosystems. This is evident in a New York Times Magazine article about a 2007 case in which an environmental advocate shot cats to protect native birds (Barcott 2007). The article cites approving remarks from several environmental ethicists. Baird Callicott acknowledges the moral dilemma in killing one animal to help another, but ultimately sides with the cat-shooter: “From an animal-welfare perspective, confining cats and shooting the cat, in the Galveston example, is wrong. . . . [but] from an environmental-ethics perspective it’s right, because a whole species is at stake.” Holmes Rolston sees no need for nuance. He considers cats “an exotic animal that doesn’t belong naturally on the landscape,” while native birds “evolved as natural fits in that environment.” Because cats are exotic and not endangered, it is morally acceptable to kill them for the greater ecological good. He insists, further, that “Suffering – the pain of the cat versus the pain of the plover eaten by the cat – is irrelevant in this case.” As Rolston has contended elsewhere, individual lives and experiences do not matter; all creatures are judged on the basis of their contribution to biospherical integrity – except humans, who are “superior to the animals” (Rolston 1988, 64) – and thus, presumably, qualified to be impartial managers.

Most environmental philosophers agree with Rolston that domestic species are morally as well as ecologically problematic. In contrast, animal welfare advocates see feral cats’ domestic origins – and their resemblance to beloved companion animals – as a source of value. Cat advocates also point out that humans created the problem first by creating a domesticated species and then by abandoning pets. Our responsibility for the ecological damage caused by outdoor cats is thus greater than in the case of deer, which further complicates the discussion about management options. (It is interesting and worthy of further analysis that it is usually the animal welfare advocates, rather than conservationists, who emphasize human culpability.)

Even more than discussions about deer hunting, arguments about outdoor cats center on what the science says. The science, unfortunately, is again inconclusive, both about cats’ ecological impact or about the efficacy of various management options. The most heated debates center on Trap-Neuter-Return (TNR) programs, in which free-roaming cats are caught, neutered and vaccinated at a shelter or veterinary hospital, and then released in their original location. Supporters view TNR as a moderate program which stabilizes the population of outdoor cats without killing them. Opponents, including the Audubon Society and the American Bird Conservancy, believe TNR does not diminish the cat population enough to reduce the threat to native wildlife, especially songbirds. They prefer lethal control, at least in ecologically sensitive areas. Both sides cite copious studies to support their positions, suggesting that a simple appeal to the evidence will never solve the conflict.

This is partly because the data is genuinely complex and partly because partisans on both sides exhibit what social scientists call “confirmation bias.” Conservationists thus read the evidence through the lens of their prior conviction that cats are ecologically damaging and must be removed. For example, an article about Reunion Island in the Indian Ocean asserts an “immediate need to establish conservation procedures to reduce the feral cat population and so limit their harmful effects on petrels.” The “conservation procedures” should include “permanent poison baiting and trapping” (Faulquier et al. 2009, 334). According to the authors’ own research, however, petrels face numerous threats, the most significant of which is in fact light-induced mortality of fledglings. Cat advocates also read the data through their own lens, insisting that cats do not kill enough native animals to pose a serious ecological threat and that TNR is always effective. While this is probably true for disturbed urban or suburban settings, there is abundant evidence that in more fragile ecosystems, especially islands and coastal areas, cats are significant threats.

Related to the problem of confirmation bias is the use of socially constructed categories as though they were impartial and transparent. Apparently neutral terms such as exotic, native, and weed are not given by nature but invented by people. They are also fluid and changing. Today’s wetland was yesterday’s swamp; today’s invasive exotic was yesterday’s valued ornamental. And one person’s foreign predator is another’s beloved companion. Even the concepts of wildness and domesticity are far less permanent and objective than most environmental philosophers acknowledge. Like the divisions between species and varieties, the lines between wild and domestic animals (and plants) are thin, porous, and changeable. No creature makes this clearer than the domestic cat – who may not even be all that domestic, according to theories that Felis catus changed much less in the process of domestication than other species. Feral cats, by their very existence, put the lie to the notion that domesticity means dependence on humans.

Problem Animals and Environmental Ethics

Nonhuman animals are a kind of elephant in the room for environmental ethics. We have rarely done them justice, but they ought to be at the heart of our discussions about the value of nature and our duties to it. Too often, we describe, argue about, and root for a “biotic community” that is curiously devoid of individual members. First among the members we must acknowledge are humans: we are not impartial managers but self-interested, concretely embodied and located participants in the processes we are evaluating. Second, we ought to question our unsupported assumptions that other creatures are never, as Hardin writes, “fully conscious of their own situation.” The science is clear on at least this point, and to dismiss nonhuman agency is neither evidence-based nor impartial.

Problem animals expose and deepen the contradictions in our ideas about animals generally. They thus present an opportunity to for environmental ethicists to think more deeply and rigorously about the place of animals in nature and in our own work. They raise a host of questions that we should take to heart as we struggle to improve both our thinking about natural value and our efforts to preserve it: What is nature? Why do we value it? Does nature have interests and if so, can we ever identify these with clarity and separate them from our own? What is the moral significance of nonhuman agency? And what, after all, should humans do?

The ambivalence about animals in environmental ethics is related to the deep and unresolved tensions between animal welfare and environmentalism generally. While the two movements share some common goals, they diverge when conflicts arise between the interests of nature in general and those of particular animals. It is impossible to know fully the interests of others who are very different from us, particularly when that other is an abstraction like “nature” or “the biotic community.” Individual creatures, however, do have identifiable interests, for example in continued health, life, and social interactions. Ecocentrists often fail even to acknowledge the existence of nonhuman interests, however, or they reject them as insignificant compared to larger ecological goals.

My first argument, then, is that environmental ethicists should treat animals as central characters, not mere extras, in ecological processes. Second, we ought to foreground the fact that human actions lie at the root of environmental problems, including those “caused” by problem animals. We know that deer “overabundance” is due to human actions such as predator elimination, sprawl, and human overabundance, and that domestic cats live outdoors because people abandoned them (or their parents). Problem animals are anthropogenic harms, but too often environmental thinkers skip over the human part and foreground the animals’ culpability, making deer or cats face alone the consequences of their ecological sins. (It is ironic that nonhuman animals are held be active agents only when it is not in their own interests.)

My third argument concerns the role of science in environmental philosophy and advocacy, and particularly the need to acknowledge both the uncertainty of the evidence and the bias we bring to it. Ecocentrists often cite ecological science as the ultimate support for their positions, but in fact this science is not as clear cut, unilateral, or value-neutral as they suggest. In addition, we all interpret data through a lens of predetermined values and priorities. This means we give greater emphasis to evidence that supports our positions and less to that which undermines them, often without conscious choice or malicious intent. For example, environmental advocates often minimize or ignore the ways that problem animals, including even introduced predators like cats, become part of ecological communities and food webs. Cats frequently consume mesopredators, animals such a rats and snakes which are both prey and predators. Eradicating cats can lead to “mesopredator release” and explosions in the population of other introduced species, with “repercussions felt throughout the entire food web” (Cadotte 2009, 259). In sum, good science rarely supports the notion that there is a single villain whose removal will fix all our problems. (The exception, in this case, might be Homo sapiens.)

As environmental ethicists, we are in the business of complexity and nuance. Why do we cling to simple, often dualistic, stories about other animals? There are many reasons, including a desire for an unambiguous answer, a conviction of our own objectivity, and, for many, a real hatred of domesticated animals and other “vermin.” Unfortunately, our “impartiality” towards other animals is not matched by a full, rational assessment of our own role. It is easier to point fingers at a villain we can cull than to confront the unanswerable questions raised by human culpability. The task before us is not to find magic “win-win” solutions to the problems caused by overabundant deer or introduced predators, but rather to acknowledge that biases often shape our evaluations and proposals. In many cases, there may be no management solutions that are good for all concerned – humans, ecosystems, and individual animals. That practical challenge, however, should not lead us to accept simplistic and unsupported philosophical and moral claims.


Anna Peterson teaches social, environmental, and animal ethicss in the Department of Religion at the University of Florida.  Her recent books include Being Animal:  Beasts and Boundaries in Nature Ethics (Columbia, 2013) and Religion and Ecological Crisis: The “Lynn White Thesis” At 50, co-edited with Todd LeVasseur (Routledge, 2016).  Presently she is writing a book on material practice in ethical theory.

Works Cited
Barcott, Bruce. 2007. “Kill the Cat that Kills the Bird?New York Times Magazine (Dec. 2),

Cadotte, Marc W. 2009. “Editor’s Choice: Unintended Trophic Cascades from Feral Cat Eradication,” Journal of Applied Ecology 46, No. 1 (February): 259.

Chollet, Simon and Jean-Louis Martin. 2013. “Declining Woodland Birds in North America: Should We Blame Bambi?Diversity and Distributions 19, No. 3/4 (March and April): 481-483.

Gustafson, James. 1994. A Sense of the Divine. Minneapolis: Fortress Books.

Hardin, Garrett. 1979. “Response to William Aiken: Lifeboat Ethics?BioScience 29, No. 6 (June): 336-337.

Humane Society of the United States (HSUS). 2012. “The Outdoor Cat: Science and Policy from a Global Perspective.” Presented at conference. Los Angeles (December 3-4).

Jessup, David A. 2004. “The welfare of feral cats and wildlife.” Journal of the American Veterinary Medicine Association 225, No. 9 (November 1): 1377-1383.

Jordan, William R. III. 2003. The Sunflower Forest: Ecological Restoration and the New Communion with Nature. Berkeley and Los Angeles: University of California Press.

Kilpatrick, Howard J. and Andrew M. LaBonte, 2003. “Deer Hunting in a Residential Community: The Community’s Perspective.” Wildlife Society Bulletin 31, No. 2 (Summer): 340-348.

King, Roger. 2009. “Feral Animals and the Restoration of Nature.” Between the Species IX.

Levy, Sharon. 2006. “A Plague of Deer.” BioScience 56, No. 9 (September): 718-721.

Loss, Scott R., Tom Will, and Peter P. Marra. 2013. “The impact of free-ranging domestic cats on wildlife of the United States.” Nature Communications 4, no. 1396.

Marra, Peter and Chris Santella. 2015. Cat Wars: The Devastating Consequences of a Cuddly Killer. Princeton, NJ: Princeton University Press.

Peterson, Anna L. 2013. Being Animal: Beasts and Boundaries in Nature Ethics. New York: Columbia University Press.

Peterson, M. Nils. 2004. “An Approach for Demonstrating the Social Legitimacy of Hunting.” Wildlife Society Bulletin 32, No. 2 (Summer): 310-321.

Rolston, Holmes III. 1988. Environmental Ethics: Duties to and Values in the Natural World. Philadelphia: Temple University Press.

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Tilghman, Nancy G. 1989. “Impacts of White-Tailed Deer on Forest Regeneration in Northwestern Pennsylvania.” The Journal of Wildlife Management 53, No. 3 (July): 524-532.

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  1. Hello Anna Peterson, great article, thanks. I’m writing you from across town in Gainesville. My wife is an avid wildlife rehabber, and I an avid hiker, so there’s much above which we can relate to. Given we are both local, I’ll share a relevant local story.

    As I’m sure you know Gainesville has, like most of Florida, experienced explosive growth since I first arrived in Gainesville in 1970 to attend UF. What is now the Oaks Mall, a traffic jammed westside shopping hub, was in 1970 “way out in the country”. Since then we’ve bulldozed much of the county, erasing wildlife habitat with wild abandon, including um, the subdivision where I am writing this.

    There are some wild islands left here and there across the county, and my favorite is San Felasco State Park, a nature preserve on the northwest side of town. In recent years there has been some controversy about feral hogs in the park, and the main complaint seems to be arising from the “Friends Of The Park” bike club which has punched miles of trails through the north side of the park. The bike club folks appear to become more than a little hysterical when the hogs disturb their tidy trails, and a call for a mass extermination hog holocaust has arisen in some quarters. The local paper covered these concerns awhile back.

    Which is a long way of saying I entirely agree with your premise that “we ought to foreground the fact that human actions lie at the root of environmental problems, including those “caused” by problem animals.”

    A key problem I see, thanks in large part to my wife’s work, is that most of us have never had the opportunity to experience wildlife as individuals, and thus we abstract the issue by labeling them as a “species”. And then from that detached abstract experience we embrace for ourselves the self flattering role of God the manager of all things everywhere. And then we start getting in to various kinds of trouble as we attempt to perfect a system that has been managing itself for millions of years without our help.

    In the case of San Felasco our local state park, one solution might be to remove the trails. The park would still be open to any human who wished to experience it, but it would not be so easily accessible as to encourage visitation from masses of us who have no clue what the concept of wildlife preserve means.

    And the hogs? Already taken care of. If one spends enough time off the trails one sees the coyote families hunting the packs of tasty piglets. But, this would likely be easy to miss if one is zooming through the park with the iPod blasting in your ear at 30mph on a bike.

    In any case, we’re all part of the problem, me included. There are simply too many of us. All I can say in my own defense is that we didn’t have kids.

    My comments fail to give your carefully reasoned analysis the response that it deserves, but I thought perhaps in this instance I could contribute more by sharing a local story which speaks to your interest.

    Thanks again, and nice to meet you.


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