Assertion: caribou's coat | /r/HasAspect | two layers of fur
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Source sentences:
text: The coat has two layers of fur: a dense woolly undercoat and longer-haired overcoat consisting of hollow, air-filled hairs.[Notes 4] Fur is the primary insulation factor that allows reindeer to regulate their core body temperature in relation to their environment, the thermogradient, even if the temperature rises to 100 °F (38 °C).