CELPIP Reading Part 3 Practice Test: The Lynx and the Snowshoe Hare

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Across Canada’s boreal forest, few relationships between predator and prey are as closely linked as the one between the Canada lynx and the snowshoe hare. Both animals are built for deep snow. The hare takes its name from its oversized hind feet, which spread its weight so that it can bound across soft drifts without sinking. Its coat also changes with the seasons, turning from brown in summer to white in winter, a shift triggered by the changing length of the day rather than by the arrival of snow. The lynx, a medium-sized wild cat with tufted ears and a short, black-tipped tail, has long legs and wide, heavily furred paws that work much like a pair of snowshoes. In winter especially, hares make up most of what a lynx eats.

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What makes the pair famous among scientists is a pattern that repeats itself roughly every ten years. Over several years, hare numbers climb until, in some places, the forest seems to be overrun with them. Then the population crashes, sometimes falling to a small fraction of its peak, before slowly beginning to rise again. Lynx numbers follow the same curve, usually a year or two behind. The pattern was first documented not by biologists but by fur traders. The Hudson’s Bay Company kept careful records of the lynx pelts it bought from trappers throughout the 1800s, and when scientists examined those ledgers in the twentieth century, the regular rise and fall of the lynx population stood out clearly. The figures still appear in ecology textbooks today.

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For decades, researchers debated what drives the cycle. The obvious explanation is that lynx simply eat too many hares, but the reality has proven more complicated. Long-term experiments in the Yukon, in which some areas were fenced to keep predators out and others were given extra food, suggested that several factors work together. As hare numbers peak, the twigs and shrubs they feed on in winter become scarce. At the same time, lynx, coyotes, owls and hawks all multiply. Constant danger also appears to stress the surviving hares so much that they produce fewer young, which helps explain why their numbers stay low for some time even after many of their predators have disappeared.

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For the lynx, a crash in the hare population means hard times. Adults lose condition, few females breed, and kittens born in such years rarely survive. Some lynx travel hundreds of kilometres in search of better hunting grounds, which occasionally brings them into areas where they are seldom seen. Researchers are now watching for a newer threat. As winters grow shorter in parts of the country, snow sometimes arrives later or melts earlier than it once did, leaving white hares standing out against a brown forest floor. Because the change in coat colour follows daylight, the hares cannot easily adjust, and scientists are studying whether this mismatch makes them easier for predators to find.