Biology: Look up "sexual reproduction." The historical record: Almost every time male and female are kept together by anyone, they breed and there are too many tigers, not too few. The issue they have is with too many cubs and too many survivors. They need homes, that's all. Genetic purity: Give it up.
So you want me to find articles for you that prove that sexual reproduction works and that tigers routinely have a lot of cubs when in captivity. It sounds like you don't know anything about the business that you disparage.
Yes, Tigers reproduce...they have sexual organs you know. And yes, they reproduce in captivity owned by NGO's also. So what's your idea and what difference does it make?
I don't know where this will end up, but "Save the Tigers Fund" and IFAW have earned the contempt of the Chinese government. The Chinese offered to meet them all the way, but their offer was spurned, as most would expect of animal rights zealots. The AR people have made the Chinese lose face. This is not good. Now the AR people have lost any chance that they might have had of influencing Chinese policy. That is just as well.
It may well be that the twilight of the tiger is its destiny. It will be but one of many large animals that have seen their ends in the last 15,000 years.
One thing happens every once in a while that makes me want to scream and rattle some cages. Some inexperienced person, maybe has never worked with a big cat in his life, buys a few and starts a "sanctuary." If he has some money and some manual skills, maybe he winds up with some really nice cats and really nice places for them to stay. This person gets his experience on the job and his information out of books and the Internet. So far I am cool with all this. I think that it's just as valid a way as any. What makes me really angry is when these self-educated experts get uppity. A few years of experience and they seem to forget their own beginnings. Over and over again the story is the same. Someone starts a sanctuary, gets a license, then they start bashing on people who do exactly the same thing they did, making all sorts of dire warnings, testifying in front of state legislatures that this is wrong, talking to county commissions to get them to deny permits or zoning variances. I hate the hypocrisy. Right now I'm reading about one of these places where the owner has expressed many times his desire that people don't do what he did. His cages are built in a way that a human can almost squeeze between the bars and the tigers can reach into other cages. Someone who works there got clobbered by a cat reaching through from another cage, but not hurt. There is no physical barrier to anyone just reaching in with their entire arm and a tiger can reach someone standing about three feet away. This is a place where the owner continually gets in the news bitching about someone else's unsafe conditions. I've read some statements of his that just made me mad. I think he helped drive someone I know out of the business, and that person uses cages that people can't reach into and get their arm pulled off. They also prevent tigers from reaching out and hurting people, but no, that's not good enough for his highness.
