a mating question... I hope you know...

Question
How does a crocodile know not mate with alligator?  Same thing with snakes even ... Like how would a rattle snake know not to mate with another snake of different species?

Answer
Most animals other than humans, the higher apes, and dolphins mate only at certain times.  The mating is triggered by clues from the female.  When females ovulate they go into "heat" cycles and this is what gets the males "excited" enough to interested in mating.  Many times the females will give off signals to let him know.  The signals can be physical or chemical (pheromones).  Alligators respond to alligator signals, crocs to crocs.  Snakes respond to pheromones from their own species only.  Actually you can trick snakes into mating with other species by using pheromones!  In captivity people have actually mated kingsnakes to rat snakes.