Photo of the Week: January 25, 2010

Hi Gang!

It’s wintertime in the northern hemisphere, and in southern California that means its time for northern elephant seals, along with a several other species of pinnipeds, to gather together to bear pups and mate. Second only to the southern elephant seal in terms of size in the world of seals, adult male northern elephant seals routinely reach proportions 13 feet and 5,000 pounds. Females are smaller attaining a maximum size of approximately 10 feet (3m) and 1,500 pounds. The 4-foot long pups weigh in the neighborhood of 75 pounds.

Northern elephant seals are probably best known by members of the general public for the shape of the nose of adult males. The nose bears some resemblance to the trunks of elephants, and just a quick look makes it easy to understand how the northern elephant seal got its common name. Males begin to develop their enlarged proboscis at the onset of sexual maturity, somewhere between the ages of three to five years old, and their nose is fully grown by the time they are seven to nine years old.

While conditions often make it difficult to dive with elephant seals, there are a number of rookery areas on the California mainland where the animals can be observed while they are onshore. I captured this week’s POTW at Ano Nuevo State Park, a well-known rookery area south of San Francisco where thousands of northern elephant seals gather every winter. The photograph captures a female that appears to be objecting to the advances of a male

Breeding northern elephant seal bulls fight for dominance, not territory. A dominant bull will mate with many of the mature females in a breeding area, while most subordinate bulls will be lucky to mate at all. A dominant bull does not eat or drink during the breeding season as he is completely occupied with mating, maintaining dominance, and preventing his subordinates from mating.

The range of the northern elephant seals extends from Baja, Mexico northward to the Gulf of Alaska. Northern elephant seals migrate twice a year between their rookery areas in Mexico and California. During their winter breeding season, northern elephant seal come ashore. During the remainder of the year, except during periods of molting, elephant seals tend to live offshore where they demonstrate their skill as champion divers. Over the course of a year bulls spend roughly 250 days at sea covering an as-the-crow-flies distance of at least 13,000 miles. Females spend approximately 300 days at sea covering slightly more than 11,000 miles. No other mammal migrates over such long distances twice every year.

When in pursuit of prey, these pinnipeds have been documented to dive to dive as deep as 5,000 feet and can remain submerged for at least one hour while rarely spending more than four minutes between dives. The preferred prey consists of a variety of deepwater fishes and squids.

Northern elephant seals were hunted to the brink of extinction for the oil in their blubber during the 19^th century reducing their population to something south of 1,000 animals. Ultimately they were protected by laws in Mexico and the United States, and they have made a remarkable recovery with the current population likely being larger than it was in prehistoric times because northern elephant seals probably bred only on islands (not the coastal mainland) due to the presence of predators such as grizzly bears.

Approaching northern elephant seals, especially bulls during their mating season, can be tricky business. They are highly protective of their turf and can be quick to turn against any intruder. The terrain is often difficult to traverse for two-legged creatures- humans- but the bulls can cover ground at surprising speeds. Considering their size and yours, any physical confrontation would be a gross mismatch in which you would be a serious underdog!

I hope you enjoy this week’s POTW!

See you next week,

Marty