Juvenile elephant seals prepare for migration

Plenty of juvenile seals are still on the beach, resting during their fall haul-out. They gradually depart, one by one. Look for a few adult bulls to show up toward the end of the month, preparing for the breeding season.

The young males, most less than 6 years old, return to the ocean after six weeks without food during their time on the beach. Their bodies are adapting to long fasts. Working out muscles and letting their bones support their weight on land strengthens them, an important part of their physical development.

The size of the nose (technically, proboscis) is a rough indicator of seal age for males. The females never grow that distinctive, eponymous appendage. It starts growing when the young males are about 5 years old, bending down. It grows into a noticeable trunk in the following year. It continues growing throughout the seal’s life, so senior seals have very impressive ones, indeed.

Most of the young seals on the beach are males. Although equal numbers of males and females are born, by age 2 more males than females are on the beach in the fall. At age 2, females are already mature and getting pregnant. Those that go through puberty at age 2 and get pregnant give birth around the time they turn 3. More than half have a pup at age 4. Nearly all have had a pup by the time they are 6.

Pregnant females are at sea in November, feeding and growing the pup inside them. They’ll be back on the beach in January to give birth.

Males are thought to be physically mature for breeding as young as 5 years old. Only the most dominant males get to breed, so younger bulls are not likely to get far enough up the dominance hierarchy to claim females. Less dominant males do some breeding, as females leave the beach, and perhaps in the water. But breeding honors go mainly to the dominant beachmaster.

Age and size go into the dominance mix. Watch young males work on their sparring skills. They tussle with each other on the beach and in the water. The bump chests, and nip at each other with their developing canine teeth. They go through the motions of fighting like adult bulls, but youngsters rarely draw blood. Their fights are not as serious as the fights between adults.

The chest shield is another indicator of maturity. It’s thick, calloused skin, often pink in mature bulls. The chests of these young bulls are starting to show the chest shield developing.

If juvenile elephant seals had locker rooms, I imagine these youngsters furtively comparing their noses and chest shields: Wow, Bumpy’s nose is already hanging down. His chest shield has more crinkles than mine — and hear how deep his voice is!

November is the calm before the storm of the birthing and breeding season. The first pup of the season is usually born in late December, but in 2016, one was born in late November.

This story was originally published November 21, 2017 at 8:08 AM with the headline "Juvenile elephant seals prepare for migration."