Many of us at the Wildlife Trust of South and West are fond of our pets and there are quite a few of us with cats. The issue with cats is that they are a top predator and are responsible for killing plenty of birds and small mammals. As a cat owner myself I often struggle with the dilemma of how to reduce my cat's impact on my local wildlife. Clearly as pets, which are fed, they are at a much higher density than any natural predator would be that was regulated by food availability in the natural environment, so I feel I have an obligation to do what I can to reduce this unnatural advantage.
"Among the general public, large domestic cat populations combined with frequent observations of cats stalking and/or killing wildlife has contributed to a widespread belief that domestic cats kill large numbers of birds, and may have contributed to the marked population declines that have occurred in recent decades (Baillie et al., 2006). This perception is supported by research suggesting that cats may be responsible for one third of the mortality occurring in some local bird populations (Churcher & Lawton, 1987) and estimates, derived from scaling up local studies to the national level, that cats kill 25–29 million birds per annum in Britain (Woods et al., 2003)."1
This can be a very emotive issue as there is little empirical evidence that cats have a hugely adverse impact, the base data is just not there, however where cats are introduced their impact on wildlife is notable. And according to Woods et al "Churcher & Lawton (1987) calculated that in a single English village, cats were responsible for up to 30% of mortality in a house sparrow population and concluded that domestic cats were a major predator in a typical English village. They found that the average cat caught and brought home approximately 14 prey items over the 12 months of their survey."2
In this complex argument there is also the issue that a reduction in cats could see an increase in other predators such as rats, which also clearly have an impact on other wildlife, however they are part of the natural balance and do not have some of the unnatural advantages our cats have. I know my cat has been out on the hunt as he generally brings back the kills for me - however having found kills out in the field not far from my house I suspect that his gifts to me are only the tip of the iceberg. So a cat that never brings back a kill cannot be assumed to be benign.
There can be no doubt that Tiddles often brings us a lovely gift of birds and small mammals and in the current climate of wildlife declines the more we can reduce the damage our pets do the better. We as cat owners can take a little bit of action to reduce the kill count - particularly at this time of year when young birds are in nests and starting to leave.
Bells on collars are one potential way of reducing how many birds are affected however some recent BTO research has suggested that cats are particularly adept at ensuring they don't "jingle" too much. Changing the collars regularly may help as may particularly bright collars.
Limiting your cats ventures outside during nesting season is a sensible precaution3, ensure your pet has plenty of toys, food and water if this a course of action you want to take. I personally keep my cat in from the start of May until the end of June, ensuring he has plenty to occupy him in the meantime. I have also always kept my cats in at night throughout the year to limit their ability to attack roosting birds, although I may be having an impact on reptiles as a consequence.
According Woods et al "The number of mammals brought home per cat was signiﬁcantly lower when cats were equipped with bells and when they were kept indoors at night. The number of herpetofauna brought home was signiﬁcantly greater when cats were kept in at night."2 This is a complex situation and we appreciate that this can be frustrating to anyone trying to do their best for wildlife.
There are always concerns that bells and collars can harm cats if they get caught in trees, which is why perhaps some limitations on outdoor activities may be a preference to cat lovers.
Another approach to limiting your pets attacks is to use sonic cat repellents, especially around feeders, reducing the cat's ability to sneak up on the birds.
Also spreading the feeders around the garden and placing them in open places allows birds to spot potential predators, enabling them to flee.
Ultimately we should remember that us humans are having the greatest impact on wildlife, all our activities from deforestation to dumping vast amounts of carbon into the atmosphere means that everything we can do to reduce that impact is important.
1Sims, V., Evans, K.L., Newson, S.E., Tratalos, J. & Gaston, K.J. 2008. Avian assemblage structure and domestic cat densities in urban environments. Diversity & Distributions, 14: 387–399.
2Woods, M., McDonald, R.A. & Harris, S. (2003) Predation of wildlife by domestic cats (Felis catus) in Great Britain. Mammal Review, 33, 174–18 3Baker, PJ., Bentley, AJ., Ansell, RJ., and Harris S (2005) Impact of predation by domestic cats Felis catus in an urban area. Mammal Review V35 issue 3-4, pp. 302-312