Cats as invasive species by Hannah Lockwood - Invasive Species Week

Hannah Lockwood (pictured) is a PhD student at the University of Derby. Twitter: @Han_Lockwood

Domestic cats are an invasive, non-native species and occur on all continents around the World. Their effects as predators are particularly apparent on oceanic islands, where high species endemism and poorly developed predator defence strategies can lead to severe declines and extinctions of native species (Medina et al. 2011). However, in the UK, prey species have evolved alongside the European wildcat (F. s. silvestris) and mustelid species, exerting similar pressure on populations (Beaumont et al. 2001; Clegg 2017). Therefore, prey present in the UK are better adapted to either avoid predation (through crypsis, escape, or defence), or able to cope with losses (through high productivity rates) than on remote islands where prey species have not faced such predation pressures previously.  

Cats in the UK are mostly owned, although some small populations of feral individuals do persist in some areas. While our owned cats are generally well-fed at home, they can still be active hunters. This may be a particular problem for our native wildlife, as owned cat populations are not limited by a natural carrying capacity and, therefore, cat numbers can continue to grow and become more densely populated.

My research

My PhD research is firstly looking into the rate at which cats return prey home. Although this has been done before my many authors, this will give me a baseline for future extrapolations. This part of the study has, so far, been running for three years and will total 3.5 years once complete.

Secondly, we are deploying cat-worn video cameras to monitor all behaviour by cats when outdoors. This will allow us to compare the return rates on video to our larger return study. We can then look at the proportion of all prey captures returned home (on video) and extrapolate our larger return dataset to give an estimate of total prey captures in the UK.

The third section of my PhD looks into the impacts of predation by domestic cats on prey populations here in the UK. For this I will use mapping and population modelling techniques to see if cat density (or some other factor) may be causing a decline in our prey populations.

What the cat dragged in

‘What the cat dragged in’ is the title of my main research study which has been running since May 2018. We have now closed the project to new participants, so are not currently looking for any more cats. We have over 1,000 cats now registered, of all ages and backgrounds. So far we have found that most cats do not return any prey home each month, while some ‘super predators’ can return up to 60 prey items in a single month (although this is very rare).

I look forward to keeping you all updated as my results are analysed and published.

References

Beaumont M, Barratt EM, Gottelli D, Kitchener AC, Daniels MJ, Pritchard JK, Bruford MW (2001) Genetic diversity and introgression in the Scottish wildcat. Molecular Ecology 10: 319-336. doi:10.1046/j.1365-294X.2001.01196.x.

Clegg C (2017) The Scottish Wildcat. Merlin Unwin Books, Shropshire, UK.

Medina FM, Bonnaud E, Vidal E, Tershy BR, Zavaleta ES, Josh Donlan C, Keitt BS, Le Corre M, Horwath SV, Nogales M (2011) A global review of the impacts of invasive cats on island endangered vertebrates. Global Change Biology 17: 3503-3510. doi:10.1111/j.1365-2486.2011.02464.x.

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