Antarctica

Antarctica by Gabrielle Walker Read Free Book Online

Book: Antarctica by Gabrielle Walker Read Free Book Online
Authors: Gabrielle Walker
ran into in the Crary Lab on his way out to the field. Bob worked at several different Weddell seal colonies, but he said we’d find him today at Turk’s Head, the big blunt end of a rocky cape that juts out into the sea ice just beyond the Erebus Ice Tongue.
    He’d already told me that right now, in early November, was the perfect time to study Weddells, because this was more or less the only time any of them came up out of the sea. Even so, we were unlikely to see males since they would only usually be on the surface when they had just lost a serious fight for underwater territory. But the females had to emerge to give birth, and we were entering prime pupping season.
    Bob had also told me why he was so interested in Weddells. ‘When animals are on the edge, stressed out, they come up with the most interesting survival strategies. I’m intrigued by the places and times where they have to go to the greatest lengths.’
    Every so often, we saw a seal in the distance. They looked like slugs, fat and dark and lying utterly still. One advantage of the long American presence at McMurdo was that researchers had been studying and tagging the seals around here for nearly forty years. Any Weddell that you saw here was almost certain to bear a bright yellow or blue tag on its flipper. It could be jarring to see this overt sign of the presence of humans among animals that ought to be wild. But the tagging neither hurt the seals nor impeded them in their swimming, and it provided a spectacular database to trace how the most southerly mammal on Earth could make a living in a place that should surely be out of bounds to warm-blooded animals.
    We parked the Mattrack and Bob came over to greet us. He led us off towards the colony, probing every so often with an ice axe. ‘Whenever you’re working around seals there will be cracks,’ he said. ‘Be careful and step where I step.’
    As we walked, Bob explained that he was working now on population dynamics—how the seals lived and what sort of trade-offs they needed to make. All the other Antarctic seals live much farther north, in the pack ice, where stretches of open water form daily and air is easily had. Weddells are the only marine mammals to live in fast ice—where the sea covering is thick and there are very few breaks—and they have to go to considerable lengths to achieve this. It’s hard being an air-breathing mammal in a place where air is scarce. They have developed special hinges on their jaws so they can open their mouths extraordinarily wide; with their inclined upper incisors they gnaw at the ice to keep breathing holes open throughout the winter. And they can hold their breath for up to an hour and a half before they have to find a hole, trumpet a warning that anyone else using it should get out of the way, and then surge upwards for that first fresh gasp of air.
    Why should they go to so much trouble? Bob thinks it is so they can exploit scarce resources with much less competition. No other mammals are down here hunting the fish. And, perhaps more importantly, nobody else is on the hunt for seal pups. Up in the pack ice, killer whales and leopard seals prowl, but neither of these can live down here.
    By avoiding these predators, seal pups have an unusually high survival rate compared to other similar creatures. But even so, only one in five of them will make it. Bob is interested in the details of this stark number. Who has a better chance than whom? What does it take to get ahead of the pack in the survival stakes?
    Now we were walking among the colony proper, and Bob’s colleague Mark Johnston came over to say hello. He saw me staring at two dead pups. They were pathetic scraps, one with its face planted in the snow, the other, even thinner, bent at an awkward right angle. ‘That’s part of the eighty per cent mortality right there,’ he said. ‘That little skinny one starved to death. It took

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