NATURALLY SPEAKING: Northern Elephant Seals: Bulls, Dominance & Harems

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February 23, 2006

Northern Elephant Seals: Bulls, Dominance & Harems

Northern Elephant Seal Bull: Vocalization
AÃ±o Nuevo State Reserve

You'll often hear them long before you see them. The largest seal in the world, the elephant seal, hauls out along the California coastline in December in order to establish harems, or breeding groups.

Northern Elephant Seal Bull: Nose Vocalization
AÃ±o Nuevo State Reserve

One of the first steps in the establishment of a harem is to become a dominant or alpha male. In order to do this, you need to defend your turf against all comers - making it a safe, hospitable place that a female elephant seal, or cow, would want to birth and nurse her pup. The mature male, called a bull, will curl his long nose towards his throat and make a call, or vocalization, that states to the other males: "Come and get me!" This call can be heard for miles.

Northern Elephant Seal Bull: The Warning Gape
AÃ±o Nuevo State Reserve

When a bull meets another male, they will size each other up. They take in their relative sizes: how long their noses are, and how big their teeth are. I call this yawning at each other a warning gape: the better to bite you with. If one male doesn't turn around and leave, then the dominance display moves to the next level and the males rear up and come together for a physical encounter, chest to chest.

Northern Elephant Seal Bull: Chest Shield
AÃ±o Nuevo State Reserve

The battle-worn males have a calloused chest, this chest shield develops as the bull grows, and helps protect them from injury when they fight with other males. Bulls often try to bite each other in the neck.

These physical encounters take a lot of energy on land, and rarely last more than about 10 seconds. However, some battles seem to go on and on. All male elephant seals are very conscious as to where they fall in the dominance hierarchy. And as the alpha male fasts for the months in which he reigns over his breeding harem, he loses weight, often as much as 25 pounds a day. This makes it more and more difficult for him to keep his position as the season progresses. By the end of the season, it turns into a relative free for all, where the less dominant males, who have been chilling on the loser beaches, have some chance of mating with the late-pupping cows.

Northern Elephant Seal Bull: Battered Noses
AÃ±o Nuevo State Reserve

Only mature males have the long elephant-like nose. Their nose is quite delicate and is considered a secondary sexual characteristic - the bigger the nose, the more mature and strong the male. That said, a bull's nose can be hurt in battle, but that doesn't stop the bull from becoming an alpha male with his own harem.

Northern Elephant Seal Bull: Dominance Displays
AÃ±o Nuevo State Reserve

Northern Elephant Seal Bulls Lunge For The Throat
AÃ±o Nuevo State Reserve

Although the Northern Elephant Seal has no natural predators on land other than humans, the young pups often get caught in the middle of battles when an alpha male is protecting his harem from interlopers who hang around the boundaries of the harem, hoping for some action of their own. Every year, young pups are squashed by these big bulls.

Northern Elephant Seals: Pups Get Caught In The Middle
AÃ±o Nuevo State Reserve

Below, you can see a big alpha male in the foreground, with all his cows and pups around him. You'll note that there are no other large bulls in his territory. He protects it, with violence if necessary. However, since the alpha bull is usually the biggest, strongest bull around, he often does not have to make much of an effort to deter other bulls. He can just rear up, give a warning gape, or move towards the invading male, and that male will turn tail and flop away. Not every male elephant seal is destined to have his own harem - only 5% of all males ever father pups and have a harem, and very rarely does an alpha male reign for more than one season.