Chances are that if you see a dog walking down the street alone with no human, you immediately think “whose dog is that?” and may try to help the dog find its way home. If you see a cat in that same situation, you may not think anything of it. It is just another outdoor cat parading around.
However, we need to start thinking more of it when we see these outdoor cats. Ecosystems are facing biological littering of outdoor cats. The overabundance of domestic cats that are allowed outdoors by irresponsible pet owners leads to an increase in outdoor cat populations, a decrease in biodiversity, and a decrease in eco-stability.
So, let’s talk about those outdoor cats. This is essentially the same prompt I received from my Wildlife Management professor during the first week of class. Ironically, as I was walking to my car to drive to school that same day, I was greeted by an outdoor cat. This interaction made my morning, so my thoughts on outdoor cats were particularly warm and fuzzy going into this class discussion. This did not last for long. Very quickly I was informed of the drastic dangers outdoor cats pose to the environment and wildlife populations.
The next semester I took Wildlife Conservation with the same professor. During the first week of class, we read an article titled “Pick One: Outdoor Cats or Conservation” which served as an extremely informative introduction to this topic. This article left such an impact on me. In layman’s terms, this article explains the issue that outdoor cats have become an invasive species that are leaving colossally detrimental impacts on wildlife species and their natural habitats. Outdoor cats threaten wildlife species, pollute the environment through fecal matter, and are capable of spreading zoonotic diseases. Let’s dive into this a bit deeper.
Wildlife Declines:
Cats are instinctive killers. Whether for sport or food, outdoor cats act as invasive predators that are killing mass amounts of wildlife, endangering the status of many species, and even forcing others to extinction. When it comes to birds, outdoor cats are the most significant anthropogenic causes of bird mortality. It is estimated that outdoor cats are responsible for more than 1 billion bird deaths annually. Read about how to protect birds from outdoor cats here in this CritterFacts article!
While bird species are declining, cat populations are tripling. This means that an increasing number of cats are predating upon a declining number of birds – and birds are not even the worst of it. Mammals are the group of vertebrates that are most impacted by domestic cat predation in the U.S. Cats kill twice as many mammals as they kill birds. A cat’s prey is made up of 69% mammals, 24% birds, and 5% herpetofauna. In combination with habitat loss, cat predation has led to an overwhelming amount of wildlife decline and extinctions worldwide.
Species that dwell on islands are particularly vulnerable to predation by cats. Cats can quickly dominate these areas while their prey is confined with no escape. A book titled Cat Wars: The Devasting Consequences of a Cuddly Killer shares a story that puts domestic cat predation in a dumbfounding perspective. Chapter one of this book describes Stephens Island; an island where the only human population is one lighthouse keeper at a time. Since being the only human on an entire pristine island can get quite lonely, one lighthouse keeper named David Lyall decided to bring his cat with him for some company.
David let his cat roam free – his pregnant cat. Where the cat population was originally zero, David introduced his domestic cat in an invasive species-like manner to raise that population to one. The domestic cat population rose once the pregnant cat gave birth and exponentially took off from there. Within two years of David bringing his cat to Stephens Island, the Stephens Island wren, a flightless songbird, became extinct.
David, an avid bird watcher, was devasted by this occurrence. He took it into his own hands to rid the island of the cats and the subsequent destruction they unleashed. It took the introduction of one pregnant cat to cause an entire species of bird to go extinct in less than two years, and twenty-six years for the island to be rid of cats. Understating what happened on this island is a more comprehendible way of realizing what is happening globally.
Chapter four of “Cat Wars” notes that a single outdoor cat kills: 177-200 mammals per year; 30-48 birds per year; 4-12 reptiles per year; and 2-5 reptiles per year. Given that these are numbers just for one cat in a year, and there are roughly 100-150 million outdoor cats just in the United States… I am scared that math will break my calculator.
Environmental Issues by Fecal Pollution:
Outdoor cats contribute significant amounts of fecal pollution to the environment. This leads to bacterial loading of soils, streams, and coastal waters. “Pick One: Cats or Conservation” reports that owned and feral cats in a Californian community of about 12,000 households contributed an estimated 106 tons of feces to the environment each year, in an area just less than 30 square kilometers. Fecal pollution is an easy route for disease to spread to wildlife and humans. This is especially of concern in human-dominated environments.
Disease Transmission:
Outdoor cats come into contact with numerous other animals and humans, making it easy for zoonotic diseases to spread. The federally endangered Florida Panther is susceptible to contacting an immune deficiency disease known as feline panleukopenia (feline parvovirus) from domestic cats. Passed through domestic cat feces, Toxoplasmosis is a disease that has infected more than 50 bird species worldwide. Not only are cats capable of serving as a rabies vector species, but they are now the most common domestic animal carrier of rabies. They can also spread roundworms, salmonella, hookworms, and protozoan parasites.
Now you might be wondering: What about TNR (trap, neuter, and release) programs? Do these programs not aim to reduce the number of outdoor cats and combat this whole issue? The answer is to this is yes, this is the aim of the program, however, there are a few fallacies of TNR that make the program almost entirely unsuccessful in this effort. There are three key failures of TNR programs from a wildlife management and cat management perspective. First, TNR programs do not address or combat wildlife declines. Once these cats are released, they will continue to hunt wildlife – sterile or not and hungry or not.
The same idea stands for the second notable failure of TNR programs: fecal pollution and the potential for disease transmission are not reduced. Once again, these cats are released after surgery and continue to contribute to fecal pollution and spread disease. Third, TNR is not effective in reducing cat population numbers. Previously mentioned was that there are 100-150 million cats in the U.S. There is simply no way to sterilize all of these cats, especially when cats can have up to three litters per year and four to six kittens per litter.
Even though the cats released cannot reproduce, they can still return to their cat colonies where immigration causes the populations to increase. As it has come into the conversation that TNR programs are not effective in tackling this issue, actions with lethal outcomes have been put in place.
Eradication of outdoor cats by lethal means gives me a heavy heart and I wish TNR programs could be the be-all-end-all solution, but it does not prove to be that way. Trust me, I am quite the cat lady myself. I even type this article as I peer at my screen over my indoor cat resting on my chest. This is why it is even more depressing to me that once these cats are released back outside, not only is conservation still threatened, but the welfare of that cat is at stake as well. My first indoor cat lived to be 18 years and it is crazy to think that I may be in my thirties before my current cat truly starts to age.
What a cozy, peaceful, and long life indoor cats hold. The same cannot be said for outdoor cats. Outdoor cats hold an extremely short lifespan of about two years. This number breaks my heart, but it does make sense. Outdoor cats are susceptible to disease, serve as prey for other animals, and run the risk of anthropogenic fatalities. Not only can outdoor cats be struck and killed by cars or predators, but they can be killed at the hands of humans who view outdoor cats as nuisances and pests. Outdoor cats have an overall poor quality of life.
It is common for those who let their cats free outdoors to believe that their cat is not part of this issue. Many will say that their cat is an angel and would never kill an animal because they just do not have it in them, or because they are fed at home. However, they do have it in them – quite literally. It is in their DNA to hunt, hungry or not.
Cats are also subsidized predators, meaning that they can be fed by their owners at home and also catch meals for themselves outside. Even if owners do recognize that their cats will drop off a “present” at the front doorstep every once in a while, the claim is still made that their cat does not kill enough to put a dent in the stability of wildlife populations. To that, it is important to note that cats are not going to bring every one of their kills home. Owners may only see that their cat kills 1 bird or 1 chipmunk now and then, but in reality, their cat is killing those 177-200 mammals per year, 30-48 birds per year, 4-12 reptiles per year, and 2-5 reptiles per year.
In 2008 the IUCN named the domestic cat to be one of the world’s most invasive species. Outdoor cats can be regarded as an invasive species because they: occupy a large geographic range, outcompete previous niche inhabitants, and reproduce exponentially. So, like the title of the article that sparked my passion for this topic, when picking either outdoor cats or conservation… let us instead pick indoor cats for the sake of conservation and the sake of cat welfare.
