When humans and animals mate it's called Bestiality.
Bestiality refers to cross-species sexual activity between humans and non-human animals.
Because of the lack of research on the subject, it is difficult to conclude how prevalent bestiality is
Zoophilia is a paraphilia in which a person experiences a sexual fixation on non-human animals.
Ethical considerations preclude definitive research on the subject, but it's safe to say that human DNA has become so different from that of other animals that interbreeding would likely be impossible.
Laws regarding bestiality vary by jurisdiction, but many countries and regions have enacted laws that criminalize such behavior.
There are several reasons why bestiality is considered illegal in many places.
Animal Welfare: Engaging in sexual activities with animals is generally regarded as a form of animal abuse.
Even though it might be a bit embarrassing if you are caught watching animals have sex, it is not illegal.