from the book, "Petrified Lightning"
The elephant seal, a ponderous mountain of flesh weighing up to 8,000 pounds, is a marine counterpart of the elephant. Its name refers not only to size but also to the enormous nose of the male seal, which hangs over its mouth and becomes swollen and enlarged during breeding season. In the spring, mature bulls come ashore and take up territories on breeding beaches. The largest bulls, usually 12 or more years old, are the "beachmasters," and each wins control of a prime section of the beach.
There is much rivalry among elephant seals for the best location for breeding. The huge males constantly challenge each other with loud roars that can be heard for several miles. As a bull snorts, its oversize nose directs the sound waves into its mouth, which acts as a resonance chamber (the proverbial bullhorn?). Many vicious but rarely fatal fights break out. Rarely does an elephant seal not bear the scars of previous encounters.
When the females finally arrive on the beach, they all tend to ignore the males. They are preoccupied with giving birth to pups, after a gestation period of 350 days. A newborn seal can weigh 100 pounds, and its rate of growth is remarkable but understandable. Feeding from its mother's milk, which is 5.5 percent fat, it grows an average of 10 pounds a day. The pups are cared for until they have quadrupled their weight—a mere four weeks. They will then be weaned from mother and join other weaned young seals in groups called weaner pods. The nursing mother never leaves to feed, and her fast can cost her as much as 500 pounds in body weight, trimming her quite a bit from her original 1,600 pounds. When the pups are on their own and seaworthy, the female is ready to breed again.
Because no male seal will leave his breeding place, he cannot feed during the three—month mating period. Meals of his favorite fish and squid, found at a depth of 300 feet, are not available to a seal protecting his section of beach and a harem. He spends his hours and energy running off rival males and impregnating dozens to hundreds of females he has rounded up for just that purpose.
Scientists were curious about just how much energy the male seal invests in this three—month period of fasting while engaged in very energy—consuming activities. One biologist felt that calculating weight loss during the breeding season would be a good index of the reproductive investment the male seal puts into this exhausting activity. The problem was to find a way to get a hefty male elephant seal onto a scale during his busily obsessed season. The answer became clear: take advantage of his well—known libido. Drugging the male during a time of such high—energy preoccupation could kill him, so the scientist planned to lure the love—intoxicated bull with a female facsimile. She was a model of a seal mounted on a surf—board base and affectionately named Raisin.
The imitation seal was extremely well constructed, with appropriate appearance, sounds, smells, and movements. Raisin's tail was automated, and her wagging was synchronized with recorded sounds of an actual female being mounted by a male. Raisin was placed just beyond a sand—covered sensitive scale.
A young male named Cod 4 was the first to fall for the ruse, and he eagerly rushed onto the scale to get to Raisin. A scientist concealed in shrubbery read off "1,919 pounds." By the end of the breeding season Cod 4 had lost more than one—third of his body weight, and, counterproductively, had been unable to copulate with any of the 350 females in his harem. His weight was lost by the combination of fasting and chasing amorous males away from his breeding area as they attempted to steal some of his females. The harem—nappers were often successful because while Cod 4 was busily chasing one male another would rush in and drive off one or more females. So preoccupied was Cod 4 with guarding his wives that he could find no opportunity to relax and propagate his race.
Not all the males on the beach fell into so unrewarding a situation. The most dominant male on the beach, a monstrous seal named Outer by the scientists, managed to inseminate 87 females during the mating season. He too paid a heavy price. Early in the season Outer had also fallen for the charms of Raisin, so the scientists had an opportunity to record his original weight: he tipped the scale at over 5,000 pounds. By the end of the season Outer had lost nearly half of his original weight by fasting and protecting his harem from over 50 marauding bulls.
Many of the males looked with favor upon Raisin, and quite a few tried to mount her. All experienced extreme frustration, and none made any further effort to add her to their harem. Although they may not have noticed, Raisin didn't seem to care.
When the mating season is over both male and female seals will return to the sea to feed. During this period each new embryonic seal carried by its mother is in an arrested state of development. Actually it's nothing more than a hollow ball of cells floating free in the womb. In a process called delayed implantation, the embryo's development is stopped for several months while the mother regains the weight she lost. Once the female recovers, the ball of cells implants and growth continues.
About 11 months after pregnancy began, the mother seal will return to the beach where she mated almost a year ago and give birth to the new offspring. She will then mate again, perhaps this time without competition from Raisin.