Domesticated Cats: Affectionate friend or deadly predator?

Domesticated Cats: Affectionate friend or deadly predator?

Domesticated Cats: Affectionate friend or deadly predator?

Cats have a reputation of being a harmless, friendly household pet. However, domesticated outdoor cats are recognized as a global threat to various wildlife species. They are considered one of the most dangerous non-native invasive species worldwide (Loss, Will, & Marra, 2013). An invasive species can be classified as any nonnative species that can cause ecological damage in new environments. Invasive species can cause populations of local flora and fauna to be decimated. In the case of domesticated cats, they have killed over 6.3 billion mammals in the United States (Loss et al., 2013) annually. 

In Canada, cats are considered one of the biggest threats to bird populations by Environment Canada. A study done by Environment Canada shows that over the last 40 years, Canada’s wild bird population has declined by 12 percent, with specific populations declining by 95 percent (Calvert et al., 2013).  The main bird species being affected includes the house sparrows, robins, and red-winged blackbirds (Vaghela, 2020).  Among the US countryside and suburbs, cats decimate the populations of many smaller mammals. These include rabbits, squirrels, native mice, and shrews (Vaghela, 2020).

The effects of cat predation can be cascading. The loss or extinction of any species drastically affects the surrounding environment. Birds, for example, play an integral role in nature itself, as they pollinate plants, spread seeds and control insect populations (Marra, 2016). With their loss, plant populations will be devastated as well, as birds and plants have a shared mutualistic bond (Sekercioglu, Daily, & Ehrlich, 2004). Similarly, the loss of other species can also lead to negative effects on their respective ecosystems and local biodiversity. 

So, what can be done to reduce the harm caused by domesticated cats? The simplest method is to keep your cats indoors. This not only benefits the small mammals and bird populations but cats themselves. The dangers outdoors for a domesticated cat are numerous. According to the Ontario SPCA, cats are susceptible to traffic, diseases like Feline Leukemia, roaming feral cats, and extreme weather conditions (Cook, 2019). By keeping them indoors, you reduce their chance of both harming other animals and being harmed in turn. 

For stray or feral cats, the solution is more difficult. Some believe that euthanasia of `feral cat colonies would be the most effective way to deal with this problem, like Marra (2016). In Toronto, there is a citywide program called Trap, Neuter and Return (TNR) which provides an alternative solution. The goals of this program, as per the City of Toronto (2021), is to reduce the number of feral cats euthanized while also reducing feral cat colonies. The program works by capturing feral cats, sterilizing them, and letting them back into the wild (Marra, 2016). The cats won’t reproduce so the population of the colonies will go down in the future. It is considered a more humane alternative. 

Regardless of your stance, this problem needs to be addressed directly. More awareness needs to be made about this situation for cat owners. It is often swept under the rug, due to cats being expected to hunt small wildlife. The major impacts of their hunting are glossed over. If you are a cat owner, keep your cat indoors and make sure it is neutered/spayed. That would be the most sustainable solution and by far the simplest. 


Calvert, A. M., Bishop, C. A., Elliot, R. D., Krebs, E. A., Kydd, T. M., Machtans, C. S., & Robertson, G. J. (2013). A synthesis of human-related avian mortality in Canada. Avian Conservation and Ecology, 8(2). 

City of Toronto. (2021, September 30). Trap, neuter, Return Program (TNR) for Feral Cats. City of Toronto. Retrieved November 29, 2021, from 

Cook, E. (2019, May 22). Keeping cats safe. Ontario SPCA and Humane Society. Retrieved November 29, 2021, from 

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).

Marra, P. P., & Santella, C. (2016). Cat wars the devastating consequences of a cuddly killer. Princeton University Press. 

Sekercioglu, C. H., Daily, G. C., & Ehrlich, P. R. (2004). Ecosystem consequences of bird declines. Proceedings of the National Academy of Sciences, 101(52), 18042–18047. 

Vaghela, A. (2020, July 7). Keep cats inside to reduce toll on birds, small mammals and other urban wildlife: Conservation experts. Capital Current. Retrieved November 29, 2021, from 

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