Changes

So, whilst in the UK, the feral cat population is perhaps 15% the size of the pet cat population, in the USA these populations are similarly sized and in Australia feral cats outnumber pet cats by a factor of 10-20 to one.

So, whilst in the UK, the feral cat population is perhaps 15% the size of the pet cat population, in the USA these populations are similarly sized and in Australia feral cats outnumber pet cats by a factor of 10-20 to one.

Trap-neuter-return (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>.

Trap-neuter-return (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].  

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. Australia also has a diverse population of prey species that have evolved in the absence of an equivalent predator to ''Felis silvestris''.

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. Australia also has a diverse population of prey species that have evolved in the absence of an equivalent predator to ''Felis silvestris''.