Baby Seal

After the female returns from her first feeding trip the most important thing for her is to find her own pup out of the mass of other pups that are not her own. Feeding a different mother's pup is a significant waste of energy, as milk production is a high parental cost. The seal overcomes this complication by voice recognition. The mother and pup must learn each other's voice in the first few days after the pup is born, before mom goes on her next hunt. On returning the mother seal calls out to her pup, causing the pup to call back. This enables the mother to be able to find her own pup and not waste any energy feeding and taking care of the wrong pup as this would only decrease her own fitness.
Diving
Pinnipeds can hold their breath for nearly two hours underwater by conserving oxygen. When the animal starts diving its heart rate slows to about one-tenth of its normal rate. The arteries squeeze shut and the sense organs and nervous system are the only organs that receive normal blood flow. Pinnipeds are able to resist more pain and fatigue caused by lactic acid accumulation than other mammals. However, once they return to the surface, they need time to recover and normalize their body chemistry.