A quick perspective from the southern hemisphere: >From what I understand in Australia, cat laws are quite strict. By invoking 'private property' rights, land owners can react accordingly to any domestic animal on their land. Councils enforce strict laws on registering and micro-chipping cats. Any cat found not on its owner's property is impounded, and must be collected in 30 days else...This brings cat laws into a similar realm with dogs (which makes sense, why do cats have right to roam but not dogs?). I think a large part of the Australian's success has been that they are conserving equally charismatic native small mammals.
In NZ, we have complicated laws with three tiers: domestic cats at one end, ferals at the other, but a very politcally correct 'stray cat' which to a conservationist might be a feral cat in the waiting, but to a cat-owner is just a lost confused domestic cat. Feral cats are controlled appropriately on conservation lands and eradicated from islands, with little worry in a land where invasive species control is widespread. However stray cats present an issue on the mainland around urban areas, where they can not legally be controlled without creating trouble with RSPCA, etc. Research is ongoing in NZ (see New Zealand Journal of Zoology 34) however, and largely demonstrates that around urban areas, cats are integrated in an ecosystem and probably provide some level of control on rats, which counter-intuitively protects birds (meso-predator release effect, etc). So although the cats themselves are not an issue, the attitude remains a problem (e.g. people being prosecuted for interfering with other people's cats). The ethics of invasive species control is contentious, and I fear we are going to see more instances of PETA, etc lobbying against invasive species control, thus pitting a welfare-based ethic against a conservation-based ethic. James
