Look what the cat brought in
Release Date 11 August 2009
Could your cat be affecting urban bird populations?
View the accompanying video
Research at the University of Reading suggests that, annually, domestic cats could be responsible for killing up to 2,500 prey animals per km2 in urban areas, significantly affecting some urban bird species.
The research looks beyond the major causes of bird population declines1, namely habitat destruction, habitat fragmentation and changes in land use and begins to analyse the contribution of cat predation. This is being done by quantifying their predation rates, hunting movements and home ranges.
Rebecca Thomas, a PhD student in Environmental Biology at the University of Reading, has recruited over 250 cats and their owners in twelve 1km² areas around Reading, as well as cat owners in other parts of the country –namely Nottingham and Brighton- collecting prey delivered by the cats from the participating households.
Previous research2 suggests that cats only return approximately 30% of their prey home. Rebecca is now using acceleration data loggers to monitor distinctive hunting behaviours in order to identify the proportion of prey returned relative to the total number killed. GPS tracking devices are also being used to determine the area over which a single cat is roaming and, hence, potentially impacting on wildlife in a local area.
Rebecca Thomas said: "In Britain, we have an estimated nine million pet cats, most of which live in urban areas. Given their extremely high densities it could be the case that cats are significantly affecting bird populations in these areas. For example, house sparrow numbers in urban areas have declined by 60% since the 1980s, most likely due to changes in urban habitats, but this is also one of the species most commonly killed by cats.
"For the first time, pet cats are being fitted with data loggers attached to a harness which will log their every movement and allow us to identify actions which have distinctive signatures such as eating, drinking and hunting. Correlating these data with the actual prey returned will give us a good idea of predation rates in urban areas."
In Reading, cat densities range from 158 cats/ km² to 626 cats/ km². Predation rates appear to be higher in spring and summer than other seasons, mainly because of the increased availability of juvenile birds. Preliminary results suggest that, over the course of the year, each cat is killing approximately 10 prey animals.
Species most affected are blackbirds, robins, house sparrows and other ground feeding birds, as well as wood mice, voles and shrews.
Rebecca Thomas concludes; "In urban areas, cats are found in much higher densities than would be the case for a wild carnivore. We also believe that birds tend to raise fewer young in urban areas than in natural habitats. This could make urban birds more vulnerable to high rates of predation. I hope my research will help us begin to understand how our pets are impacting on wild species."
The research is funded by NERCand supported by the University of Swansea.
Further information from Alex Brannen, Media Relations Manager, on 0118 378 7388 / 07834 006243.
Notes to editors:
An image of one of the Reading research group cats with a data logger harness fitted is available on 0118 378 7388 / 07834 006243.
1 The State of Europe's Common Birds report (2007) found that 45% of Europe's bird species had declined since 1980.
2 Kays & Dewan (2004)
3 Woods,Mcdonald & Harris (2003)