n most species, both sperm and egg have a short fertilizable lifespan, and once they are delivered into the female tract, the clock starts ticking. What this means, of course, if that mating or insemination must coincide closely with ovulation. If sperm are deposited many days before the egg reaches the oviduct, there is little chance that they will survive to fertilize. Conversely, if sperm reach the oviduct several days after ovulation, they will certainly find an egg that has long since degenerated.