Do cats control the population of urban rats?
For centuries, we’ve thought of our feline friends as a useful ally in the war against rats, particularly in urban environments. But are they?
A study published in Frontiers in Ecology and Evolution (Parsons et al., 2018) aimed to determine the impact of feral cats on an established colony of 120-150 city rats in Brooklyn. The researchers used cameras to document both cat and rat behaviour over a five-month period. In the 259 instances of hunting behaviour in the cats, only 20 resulted in actual rat predation attempts and only 3 of those were successful.
The study concludes that there is no evidence that cats directly suppress rat populations. Like other predators, cats have an energy budget: prey options are weighed against the potential danger and energy expenditure (Parsons et al., 2018). With that mind, it is understandable why cats choose to hunt birds and smaller rodents, such as mice, instead of city rats which are much larger and have sharp teeth to defend themselves.
The study did find an indirect impact of cats on rats: the odour of cats deters rats from coming out in the open to search for food and water. This indirectly decreases the chances of successful reproduction for rats, but it’s not clear that it’s enough to affect the size of the population. It may, however, partly explain why we think cats do control rats, since if cats are around, rats will avoid coming out in to the open.
The authors speculate that the misconception that cats control populations of city rats may also be attributed to the fact that there is public confusion between what are considered mice and what are considered rats (Parsons et al., 2018). Cats prefer to actively hunt mice (20-35 g) as they are smaller and less well-armed than city rats (which have sharp teeth and can weigh up to 10 times more than mice). As a result, only the largest and the strongest cats would risk attacking a rat, especially when there are much easier food sources available to cats (birds, smaller rodents, human food scraps) in the city.
We may think cats help control the local rat population, but the science doesn’t support that conclusion. To keep our cats safe and protect local wildlife, pets and wildlife need to be kept separate for the benefit of both. After all, cats can be prey as well as predators.
To read the full study, click here.
This article was authored by Aly Hyder Ali, a Nature Conservation Intern at Nature Canada.
Bonnington, C., Gaston, K. J., & Evans, K. L. (2013). Fearing the feline: Domestic cats reduce avian fecundity through trait-mediated indirect effects that increase nest predation by other species. Journal of Applied Ecology, 50(1), 15-24. doi:10.1111/1365-2664.12025
Parsons, M. H., Banks, P. B., Deutsch, M. A., & Munshi-South, J. (2018). Temporal and Space-Use Changes by Rats in Response to Predation by Feral Cats in an Urban Ecosystem. Frontiers in Ecology and Evolution, 6. doi:10.3389/fevo.2018.00146