Fall is the season when the juvenile northern elephant seals return to the beaches of Piedras Blancas for a month of rest, called the fall haul-out. Most of these seals will be under five years of age. Included among these juveniles will be last winter’s pups returning to the beach for the first time.
There is no obvious reason for the juvenile seals to return to the beaches at this time of the year; they are not returning to molt, give birth, or mate. We do know that prior to their return, these juvenile seals have spent months out at sea, traveling thousands of miles, in their search for food. A month of undisturbed rest on a beach after such long migrations is no doubt a welcome respite.
If we could ask the returning juvenile males why they have returned to our beaches, they might suggest that the fall haul-out is an opportunity to practice their sparring skills while providing entertainment for visitors to the rookery. What the young males learn from their sparring will be useful to them in future years when they will compete to become an alpha male during the breeding season. For both sparring and moving about on the beach, the seals must use muscles that receive little use when at sea. Coming ashore to use these muscles is beneficial to the seal’s body development for its time on land.
Being at sea constantly engaged in deep dives for eight to ten months of the year reduces the benefit that gravity has for building a strong bone structure. Research has shown that the seals gain bone mass during their stay on the beach. It has also been noted that this fall haul-out mimics the migrating and fasting pattern that will bring the seals back to the rookery for the birthing and mating seasons later in their lives. Even if we are not yet sure about all of the reasons that the juvenile seals are here for a fall haul-out, our beautiful fall weather will add to an entertaining and enjoyable time to visit the rookery.