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Mitigating the impacts of pet cats (Felis catus) on urban wildlife

Hall, Catherine (2016) Mitigating the impacts of pet cats (Felis catus) on urban wildlife. PhD thesis, Murdoch University.

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Pet cats are a very important part of life for many people and provide companionship to millions of people worldwide, from small children to the elderly. However, wandering pet cats may affect wildlife populations through direct predation, competing for prey with higher order consumers, spreading disease to wildlife and humans, exerting sub-lethal effects such as changes in parental behaviour or reduction in clutch size of prey caused by the fear of cat predation, hybridising with wild felids or breeding with stray and feral cats to maintain feral populations. In addition, they may annoy neighbours by disturbing dogs, attacking pet birds, spraying, digging in gardens, fighting (including with other pet cats) and walking on cars. Pet cats that are allowed to wander are also at risk from disease, fights with other animals that may lead to injury infection, and from traffic accidents (one of the leading causes of pet cat mortality). Despite these risks to wildlife and their pets, many cat owners in Australia and other countries such as the UK and New Zealand are reluctant to restrict their cats to their properties at all times. The primary aims of this thesis were to investigate several different precautionary approaches to reducing the risks proposed by predatory interactions between cats and urban wildlife and determine what precautionary measures the wider community considers acceptable.

In association with colleagues from Australia and overseas, I assessed the social attitudes in Australia, the USA, the UK, New Zealand, Japan and China towards pet cats and cat ownership and responsibilities with a detailed survey. We found significantly different results between all countries, indicating that if any legislation was to be imposed regarding pet cats unique approaches would be required in each country. We confirmed that many cat owners will not keep their cats inside, and therefore other methods to prevent wildlife capture and reduce pet cat roaming behaviour are appropriate.

I then examined the effectiveness of the anti-predation collar cover the BirdsbeSafe® (BBS) in reducing predation by pet cats on birds. A range of different colours and patterns are available for this device and I found that some patterns (red and rainbow) were effective at reducing predation on prey with good colour vision (birds and herpetofauna) by 47 – 54%. However, yellow collar covers were not effective at reducing cat predation on birds. The BBS had no effect on the numbers of mammal prey captured. This device is useful for cats that catch many bird or herpetofauna prey and either do not catch, or their owners would like them to catch, mammals such as rats and mice. It is not suitable in areas where there are sensitive small mammal populations. Ninety-six per cent of cats adapted to the BBS within two days, indicating that it will not upset or impede on the welfare of the vast majority of cats as long as collars are correctly fitted and checked regularly.

Previous research on the anti-predation device the CatBib and my own research on the BBS indicated that these devices may alter the roaming behaviour of some pet cats, in most cases with cats reported as staying closer to home. This potentially provides another incentive for owners to fit their cats with these devices to reduce their wandering behaviour. I tested this hypothesis on 30 pet cats wearing either the CatBib or BBS with the use of GPS collars. In addition, I collected data from cats wearing GPS collars but no anti-predation device to determine factors that influence roaming behaviour. I found that neither the CatBib nor the BBS significantly changed the roaming behaviour of pet cats, supporting claims by the manufacturers of the CatBib and the BBS that the devices reduce hunting success while not restricting other behaviours. Thus they do not offer an option to owners wishing to restrict their cats' roaming. The most significant predictor of pet cat home range was housing density, with pet cats living in more rural locations travelling significantly further than pet cats in areas of high housing density.

In order to reduce uncertainty over factors that affect cat predation I used a meta-analysis and mixed linear models to compare all of the studies that used radio-telemetry or GPS to examine cat roaming behaviour. I found that despite most individual studies showing that male cats have larger home ranges than females but no statistically significant difference between the two, comparing all the data concluded that male cats do have significantly larger home ranges than females. I also found that mature cats (over 8 years old) have smaller home ranges than younger adult cats (2 – 8 years old), desexing has no influence on roaming behaviour, husbandry practices (providing vet treatment and socialising cats with humans) did not impact roaming behaviour, and cats living in areas with low housing density (e.g. farm cats or pets on rural properties) had larger home ranges than cats in higher housing density areas.

Ultimately, the best solution to prevent pet cats from impacting wildlife and for their own protection is to keep them confined to their owners’ properties at all times. Since this is an unpopular option, education campaigns are required to change the community practices and attitudes towards pet cats so that owners either become more accepting of confinement or more willing to use predation deterrents. Since there are significant differences between different countries in how people perceive cats and the impacts of their wandering behaviour, different approaches are required in different locations. In Australia, and possibly New Zealand, people may change their behaviour based on the effects cats have on some wildlife. However, in countries such as the UK, campaigns should focus on the benefits to cat welfare.

Publication Type: Thesis (PhD)
Murdoch Affiliation: School of Veterinary and Life Sciences
Supervisor: Calver, Michael and Bryant, Kate
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