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→The Impact of Predation
==The Impact of Predation==
==The Impact of Predation==
''Felis silvestris'' is a native species in most of Africa, Europe, central Asia, India, China and Mongolia. In these regions it forms a natural part of local ecology. Due to mutual tolerance between cats and humans, the density of cat populations can be much higher within and around human communities than in rural areas.
In a study of domestic cat predation in the UK, the estimated mean predation rate was estimated at 18.3 per cat per year, with 65% of households reporting no prey brought back in a given year (falling to 22% when averaged over several seasons <ref name="Thomas">Thomas, R.L., Fellowes, M.D.E, Baker, P.J. (2012) Spatio-Temporal Variation in Predation by Urban Domestic Cats (''Felis catus'') and the Acceptability of Possible Management Actions in the UK. ''PLOS One''. 7(11), 1-13.</ref>. The same study found that only 20% of cats returned 4 or more dead prey annually. A retrospective study by <font color="red">Bowen</font color> found an average prey return rate of 3.3 birds and 12 rodents per cat per year for households where cats had outdoor access. 44.6% never returned a bird, and 39.6% never returned a rodent.
The amount of birds observed in a garden correlated significantly with the amount of environmental enrichment provided in a garden (bird feeders, scattered food and nesting boxes), as well as the amount of natural features present (long grass, trees, wild flowers, bushes). Of particular note was a correlation between bird numbers and indicators of active gardening, such as the presence of a greenhouse, vegetable patch and compost heap. However, he number of birds caught did not correlate with scores for the amount of birds observed in the owner’s garden. This is supported by findings from Thomas ''et al''<ref name ="Thomas" /> that reported numbers of five bird species was not correlated with level of their predation. The predation of robins was just significantly correlated with observed numbers (p=0.046). This may relate to some aspect of the vulnerability of this species when feeding and nesting, but the result would also become insignificant when measures are applied to counteract the problem of multiple comparisons.
The study by Thomas<ref name ="Thomas" /> also showed a significantly negative correlation between mean annual predation rate, cat population and housing density; the number of prey returned was lower in high residential and cat population density.
In a study by <font color="red">Bowen</font color>, 62% of cat owners indicated an interest in encouraging more cats in the garden, with 48.1% of those giving a positive response also indicating that owning a cat prevented them from doing so. Those who reported that having a cat restricted their ability to attract birds to the garden provided similar numbers of bird tables and hanging feeders, but significantly fewer bird boxes and scatter feeding opportunities for ground feeding birds.
It appears that improving a garden to attract and support bird numbers does not increase the general risk of predation, and cat owners should be encouraged to do so.
However, ''Felis silvestris'' is a native species in most of Africa, Europe, central Asia, India, China and Mongolia. In these regions it forms a natural part of local ecology. Due to mutual tolerance between cats and humans, the density of cat populations can be much higher within and around human communities than in rural areas.
''Felis silvestris'' is not a native species in the Americas or Australia, so that the impact it might have on wildlife in those regions may be considered much more serious and intrusive to local ecology. For example, it is estimated that i the USA free-ranging domestic cats kill 1.4-3.7 billion birds and 6.9-20.7 billion small mammals each year <ref name ="Loss">Loss, S.R., Will, T., Marra, P.P. (2013) The impact of free-ranging domestic cats on wildlife of the United States. ''Nature Communications''. 4 (1396).</ref>.
''Felis silvestris'' is not a native species in the Americas or Australia, so that the impact it might have on wildlife in those regions may be considered much more serious and intrusive to local ecology. For example, it is estimated that i the USA free-ranging domestic cats kill 1.4-3.7 billion birds and 6.9-20.7 billion small mammals each year <ref name ="Loss">Loss, S.R., Will, T., Marra, P.P. (2013) The impact of free-ranging domestic cats on wildlife of the United States. ''Nature Communications''. 4 (1396).</ref>.
Based on the most recent estimate, the UK feral cat population is perhaps 15% the size of the pet cat population, whereas in the USA these populations are similarly sized and in Australia feral cats outnumber pet cats by a factor of 10-20 to one.
Based on the most recent estimate, the UK feral cat population is perhaps 15% the size of the pet cat population, whereas in the USA these populations are similarly sized and in Australia feral cats outnumber pet cats by a factor of 10-20 to one.
TNR programmes have been shown to be effective in a number of studies <ref>Levy, J.K., Gale, D.W., Gale, L.A., (2003) Evaluation of the effect of a long-term trap-neuter-return and adoption program on a free-roaming cat population. ''JAVMA''. 222, 42-46.</ref> showed a 66% reduction in population size over an eleven-year period in one free-roaming population. In the UK, nationwide trap and neuter programmes of this type have been in operation for more than a decade. In the UK and Germany, levels of neutering are generally high, which helps to limit population growth<ref>Heidenberger, E. (1997) Housing conditions and behavioural problems of indoor cats as assessed by their owners.'' Applied Animal Behaviour Science''. 52, 345-364.</ref>. Similar programmes are now also being run elsewhere by organisations such as International Cat Care in [http://www.icatcare.org/potugal/delegates/inside-the-centre Portugal] and [http://www.icatcare.org/in-action/sudan Sudan].
TNR programmes have been shown to be effective in a number of studies. Levy, et al <ref>Levy, J.K., Gale, D.W., Gale, L.A., (2003) Evaluation of the effect of a long-term trap-neuter-return and adoption program on a free-roaming cat population. ''JAVMA''. 222, 42-46.</ref> showed a 66% reduction in population size over an eleven-year period in one free-roaming population. In the UK, nationwide trap and neuter programmes of this type have been in operation for more than a decade. In the UK and Germany, levels of neutering of pet cats are also high, which helps to limit population growth<ref>Heidenberger, E. (1997) Housing conditions and behavioural problems of indoor cats as assessed by their owners.'' Applied Animal Behaviour Science''. 52, 345-364.</ref>. Similar programmes are now also being run elsewhere by organisations such as International Cat Care in [http://www.icatcare.org/potugal/delegates/inside-the-centre Portugal] and [http://www.icatcare.org/in-action/sudan Sudan].
However, the most significant factors in the maintenance of a large feral population are climate and the availability of prey. The temperate climate of Northern Europe limits kitten survival, compared to the warmer climate of Australia and parts of the USA. Australia also has a diverse population of prey species that have evolved in the absence of a predator equivalent to ''Felis silvestris''.
==References==
==References==