Poaching. As long as the tiger is always around a poaching problem, because since ancient times, the idea that the tiger is a treasure has been deeply rooted

In the wild, wolves are pack animals, and by living in packs they stand at the top of the food chain, but despite this, they face daily threats

The existence of reproductive isolation, so that these situations can not occur, even if there are some individuals of different species sometimes complete the mating, but they generally can not produce offspring, or produce offspring can not continue to reproduce