Seals evolved from land mammals, so their reproductive activities happen on land (or ice). There are several species of seal, but the general process is about the same. During the seal breeding season, mature males fight to claim territory on the breeding beaches. These fights are dangerous and take a lot of energy. The winning “beachmaster” has to protect the territory that he wins, so he doesn’t get to go fishing. He has to live off his fat. All of this tends to shorten his life. Male seals are much larger than females because small males don’t get much chance to pass on their DNA.

The females give birth on the beach and nurse their pups. After about 6 weeks, the females’ bodies are ready to become pregnant again. They will mate with whatever male has claimed the beach. This will give her pups “winning” genes. She might also mate with a male who is able to sneak onto the beach. That way, even if the beachmaster is not fertile, she can still get pregnant. (The seals don’t “know” any of this stuff, but that’s what happens).

Seals are mammals, so fertilization happens inside the female. Male seals keep their reproductive parts tucked away inside their bodies until they need them. This keeps their streamlined shape in the water. Once an egg is fertilized, it only divides a few times, then stops for months. This way, pups are born when there is plenty of food around when the mothers need to make milk, which takes a lot of energy and nutrients. The mothers may live off of fat or go hunting and leave the babies on shore.

Why do you think mother seals only have one pup per year?

If you are interested in questions like this, you may want to study mammalogy or marine biology.

Seals usually show up to beaches around winter time to reproduce. The males usually come first to claim their territories, and some even fight for their territories if space gets tight. In this time, the females arrive and the males commit to their territory to heighten their chances of mating; some seals may mate with multiple females.

Seals are mammals, so their reproduction process is like humans (sperm fertilizes an egg). The females have an egg inside their uteruses, which is protected by fluids. After it is fertilized it forms into a seal pup for about 9-11 months (depending on what seal species you are looking at). The pups are usually born right on the beach and drink the mother's milk. The mother is not ready to mate again until about 4 weeks when the pup has become more independent.