Springtime is pup season. At this time of year, harbor seal pups are frequently found alone on area beaches. They are usually not stranded, but simply resting (as all baby mammals must do) and waiting for their mothers to come back ashore to nurse them. Adult female seals are shy and unlikely to rejoin a pup if there is activity nearby. They may only return to suckle their pup at night when people (and dogs) are not around. It is very important not to interfere with this process, and especially not to move a pup from where it is receiving care from its mother.
Within three or four weeks of birth, harbor seal pups are weaned from maternal care and are left to fend for themselves. While learning to find and catch its own food, a young seal may come ashore frequently to rest. This is often a very challenging stage of life, and not all pups survive. But while it may be tempting to "take them in," their best chance for survival is to be left alone on the beach.