How do hybrid animals happen?

Hybrids happen when two different species mate and have babies. for example, a liger is a tiger and a lion that mate and have cubs. These creatures arn't mutants just different. There are many ways in which these animals could mate. One way is that they could meet in the wild and mate but it's lesslikely because they usually have different habitats and are in a pack with there same species or loners that usally mate with the animals of there same species in that area. Another way this can occur is when there forced to breed. Some people capture animals and make them breed with different animals for their own pleasure. The last way I can think of is that scientists can put some kind of gene in the mother's egg while pregnant making the solution a wierd type of animal.