Northern Elephant Seal Superweaners

© Mike Spinak

Every now and then, I just discuss a photo, and the story behind it. Today is one of those times.

These Northern elephant seal pups are called superweaners. No, I’m not making that suggestive title up. That’s really the term that scientists call this type of elephant seal pups. The story behind that monicker is one worth sharing.

Northern elephant seals spend most of their lives at sea. Adults only come ashore during the breeding season. The females, called cows, stay on the beach for about 4-6 weeks, to give birth, nurse their young, molt, and mate. During their brief time on land, they don’t eat, nor drink, nor excrete. They nurse their pups enough for the pups to put on 200-300 pounds, entirely from their bodily reserves, losing a huge proportion of their own body mass, in the process.

At a certain point, the elephant seal mothers abruptly decide the nursing is over, and they head back out to sea. They leave their seal pups stranded on the shore. At this point, the seal pups are not nearly developmentally ready, yet, to head out to sea and begin their adult lives. They’re so bloated with blubber that they are too buoyant to swim properly. They’re stranded on the shore, while their bodies grow from being fat laden babies into being juveniles with more muscle and bone, and less fat. This is a dangerous time for the vulnerable pups; and, if a pup didn’t build up enough of its own reserves, before its mother left, it may starve and die, before it’s ready to head to sea.

When their mothers abandon them, their first impulse is to find another mother, nearby, to adopt them. This is a risky proposition, for all involved. While the mothers often have very strong mothering instincts, they only have the bodily reserves to raise a single pup. If they try to take on more, there won’t be enough milk; the mother will get too depleted generating milk, and her own pup will starve to death. Consequently, mothers will usually reject a weaned pup seeking to nurse – and the rejection is likely to come in the form of a violent bite, to drive the intruding pup away. (You can see some marks from rejection bites in the pups in this picture.)

Nonetheless, some pups do manage to get adopted, and continue weaning. Some mothers have such strong mothering instincts that they’ll take on a weaner who comes to nurse, even at the expense of their own. More commonly, mothers who lost their own children will adopt another.

Searching for another mother, for further nursing, is a delicate balance for a weaned pup. Numerous violent rejection bites can lead to dangerous amounts of cumulative injury. For this reason, most pups soon give up on finding another mother for further nursing. But for those pups who succeed in getting adopted and nursing more, the benefits can be huge. The pup can potentially put on another hundred pounds, or more, which will help it get a much stronger start in life.

Weaners who have been nursed a second time (and sometimes even a third!) by another mother are called “superweaners”. They can be quite large, fat, and swollen, with rippling waves of blubber.

In this picture, the darker superweaner is younger; the lighter superweaner has already gone through the first molt.

Northern Elephant Seal Pup Superweaners (Mirounga angustirostris), Piedras Blancas, San Simeon, California

All pictures and text are © Mike Spinak, unless otherwise noted. All pictures shown are available for purchase as fine art prints, and are available for licensed stock use. Telephone: (831) 325-6917.