Here's a nice reply from the SPCA to the letter from Tan Tuan Khoon.
Unfortunately he is at it again with this new letter. Again he refuses to acknowledge that these aren't pet cats but community cats. Also I love how the vacuum effect is dismissed as 'not practical in our highly urbanised theory' - and some people say the same about evolution. Just because it doesn't suit your point of view doesn't mean it's not true because the facts speak for themselves. As I've said time and again, there shouldn't be ANY cats left in his estate if the vacuum effect isn't true.