Cats versus rats in the city – a surprising winner

Cats are a staple in human culture. They have been fed by us, housed by us, even worshipped by us, and are still helping us with many of our problems today — ranging from controlling pests to just being a cute companion. Exactly for this reason, the cat (Felis catus) has been taken alongside man to almost all corners of the world, resulting in cats being one of the most widespread mammals (GISD, 2024). There are however some misunderstandings surrounding how we should use cats to our advantage, as they can negatively influence the dynamics of urban wildlife.

Cats as a control tool for rat pests

Cats are commonly considered as a control tool for rats in urban environments (Rattus spp.), which seems logical – 70% to 80% of prey brought home by domesticated cats consists of rodents (Baker et al., 2005; Kauhala et al., 2015; Yip et al., 2015). In Chicago, 1,000 feral cats were even released since 2012 in an attempt to release the city of its title of the ‘rattiest city in the United States’ (O’Gorman, 2021) – but there is no actual evidence that cats can suppress city rat populations specifically. Cats actually prefer defenceless and smaller prey (less than 250 grams). City rats are ten times heavier than mice, and they can be defensive when attacked, so they are not the usual go-to prey for cats. Instead of decreasing the number of rats in cities, research has shown that cats just cause temporal and space-use changes in rat behaviour, while the amount of rats in a city stays the same (Parsons et al., 2018).

Parsons and colleagues (2018) concluded this after observing the heavy pressure feral cats put on a rat colony in an industrial waste recycling site in New York City, US. This site provided more than enough food and hiding spots for the rat colony to thrive, but was regularly visited by the same five feral cats during the 79 days and nights the study lasted. The rats avoided the cats: for every 1% increase in the number of cats in this partly-enclosed urban ecosystem on a given day, it was 100 times less likely that a rat was spotted there. The presence of cats even caused less rats to be spotted the day after their presence. The cats stalked the rats 20 times out of 259 instances of behaviour recorded, and only actually preyed on the rats 3 out of 259 instances – with only 2 of those instances being successful and catching the rat. These numbers are not nearly significant enough to decrease the size of this rat colony (which was estimated at 120-150 rats), given the high reproductive rate of city rats. This however probably put enough stress on the rats to alter their behaviour and avoid the site on the days and the days after cats were spotted. This means that instead of cats causing a decrease in the number of rats, the rats just hung around elsewhere until the cats were gone.

How do we control rat pests?

But if the cats don’t even control the rat pests, is it worth it to purposefully set them out in urban environments, where they are known to hunt on native birds and mammals, causing detrimental effects on their population numbers (Kauhala et al., 2015)? I would argue that, no, this is not worth it. The loss of native species weighs heavier than their—and unsuccessful at that—attempts to decrease the rat population. Wouldn’t it then be smarter to deploy other, more successful natural predators of the rat, such as the bobcat (Lynx rufus), red-tailed hawk (Buteo jamaicensis), the coyote (Canis latrans) and the red fox (Vulpes vulpes)? Again, I think that this is not the way to go: these species will probably not effectively control the rat populations where they cause the most nuisance. Studies have shown that although all of these animals do show signs of synanthropy, they tend to avoid the highly urbanised areas. Instead, these species tend to stick to areas representing their natural habitats more, like urban green spaces, agricultural fields or close to city borders with less densely packed infrastructure (bobcat: Young et al., 2019; red-tailed hawk: Stout et al., 2006; coyotes: Gehrt et al., 2011; red foxes: Duduś et al., 2014). Of course it is always good to invest in more green spaces in the city for many reasons other than providing a safe haven for wildlife – we also experience many benefits from the ecosystem services provided, like improvement of human wellbeing (Kondo et al., 2018) and a cooling effect of the city (Aram et al., 2019).

Instead of solving the problem of rat pests by looking at natural predators, we could look at ourselves for the solution. Next to keeping our streets clean to prevent vermin from even showing up in the first place, Murray et al. (2018) found that rat traps in Chicago had the most success in neighbourhoods where there were the most complaints of rats. This was not influenced by socio-economic factors: public reporting directly identified areas of greater rat activity. This could be a great tool for targeted control efforts. 

In the end, the rat problem is our own to solve, as it is our own behaviour that attracts or deters rats.

References:

Aram, F., Higueras García, E., Solgi, E., & Mansournia, S. (2019). Urban green space cooling effect in cities. Heliyon, 5(4), e01339. doi:10.1016/j.heliyon.2019.e0

Baker, P. J., Bentley, A. J., Ansell, R. J., & Harris, S. (2005). Impact of predation by domestic cats Felis catus in an urban area. Mammal Review, 35(3-4), 302–312. doi:10.1111/j.1365-2907.2005.00071.x 

Duduś, L., Zalewski, A., Kozioł, O. et al. Habitat selection by two predators in an urban area: The stone marten and red fox in Wrocław (SW Poland). Mamm Biol 79, 71–76 (2014). https://doi.org/10.1016/j.mambio.2013.08.001

Gehrt, Stanley D.; Brown, Justin L.; and Anchor, Chris (2011) “Is the Urban Coyote a Misanthropic Synanthrope? The Case from Chicago,” Cities and the Environment (CATE): Vol. 4: Iss. 1, Article 3.

Global Invasive Species Database (2024) Species profile: Felis catus. Downloaded from http://www.iucngisd.org/gisd/species.php?sc=24 on 16-04-2024.

Kauhala, K., Talvitie, K., & Vuorisalo, T. (1 May 2015) Free-ranging house cats in urban and rural areas in the north: useful rodent killers or harmful bird predators? Folia Zoologica, 64(1), 45-55

Kondo MC, Fluehr JM, McKeon T, Branas CC. Urban Green Space and Its Impact on Human Health. International Journal of Environmental Research and Public Health. 2018; 15(3):445. https://doi.org/10.3390/ijerph15030445

Murray MH, Fyffe R, Fidino M, Byers KA, Ríos MJ, Mulligan MP and Magle SB (2018) Public Complaints Reflect Rat Relative Abundance Across Diverse Urban Neighborhoods. Front. Ecol. Evol. 6:189. doi: 10.3389/fevo.2018.00189

O’Gorman, E. (May 17, 2021). 1,000 Wild Cats Released In Chicago’s Alleys To Combat Rats. Patch. https://patch.com/illinois/chicago/1-000-wild-cats-released-chicagos-alleys-combat-rats 

Parsons MH, Banks PB, Deutsch MA & Munshi-South J (2018). Temporal and Space-Use Changes by Rats in Response to Predation by Feral Cats in an Urban Ecosystem. Front. Ecol. Evol. 6:146. doi: 10.3389/fevo.2018.00146

Stout, W. E., Temple, S. A., & Cary, J. R. (2006). LANDSCAPE FEATURES OF RED-TAILED HAWK NESTING HABITAT IN AN URBAN/SUBURBAN ENVIRONMENT. Journal of Raptor Research, 40(3), 181–192. doi:10.3356/0892-1016(2006)40[181:lforhn]2.0.co;2

Yip, S.J.S., Rich, MA. & Dickman, C.R. (2015). Diet of the feral cat, Felis catus, in central Australian grassland habitats during population cycles of its principal prey. Mamm Res 60, 39–50. https://doi.org/10.1007/s13364-014-0208-7