21 October, 2003
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I woke this morning to the call of a seal reverberating eerily up through the floor of our hut from somewhere below the ice. Is this my new Erebus Bay alarm clock? It's certainly better than any other wake-up call I've ever had.
It was warm and clear today. The high temperature was -9C, and the winds were almost nonexistent. Seals were lounging in the sun along the ice cracks by Big Razorback Island. You might wonder how they can lounge about so nonchalantly on a surface whose temperature is 0C. The key is blubber-almost 12.5cm (5") of it. While people living in cold climates often joke about putting on a layer of fat for the winter, these animals have some serious blubber. Not only does it insulate them from the cold and wind, it provides a layer of protection from cuts and bruises as well as acting as an excellent energy store for protracted periods on shore. According to one study, a resting adult Weddell Seal needs to eat at least 15,600kcal each day. How much food is that? Well, in our camp, we use the Oreo cookie as our calorie standard; a serving of Oreos (3 cookies) provides 160 calories. A seal would need to eat 97.5 Oreo servings, or 292 Oreos to get enough calories. Of course, that might not be as nutritionally balanced as their normal diet of Antarctic Herring (Pleuragramma antarcticum), or Antarctic Cod (Dissostichus mawsoni). There are approximately 150kcal in 100gm of Antarctic Herring-a seal would need to eat 10-15 kg of fish each day (not nearly as much fun as eating 292 Oreos!).
It's astounding to see the newborn pups nestled up next to their enormous mothers and realize that, by the time they are weaned in 6 weeks they will have increased their weight from 30 kg to well over 100 kg. Now, they certainly don't gain this much weight from eating Oreo cookies (though I have no doubt that you could, if you ate enough). They are gaining this at the expense of their mothers, whose milk starts with a 30% fat content that increases to 60% fat over the weeks that they are nursing. Luckily, the moms start with a healthy fat reserve, because the pups' weight gain is their weight loss. After weaning their pups, the mothers return to the water to feed and regain their lost body weight.
Darren, Brent, and I drove into McMurdo this afternoon in the Pisten Bully to pick up a piece of equipment that was slated to arrive as cargo on one of today's flights. Darren has been anxiously awaiting the arrival of his weighing sled so that he can begin his study of the mass dynamics of the seal population. Unfortunately, the flights were cancelled because today's initial weather forecast predicted some nasty weather. There are now 5 flights scheduled for tomorrow, one with the promised cargo on board. We will spend the night at McMurdo, taking full advantage of the hot water that flows from overhead (showers) and into washing machines.
Seal call alarm clock
Reverberates through the ice
Calling us to work
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