Frosty trees and shrubs, daylight savings time, long nights, early sunsets, cold, crisp air. ‘Tis winter we are headed for, the coldest season of the year. It can bring with it plummeting temperatures and subzero conditions. To avoid these harsh chilly environments, some animals migrate, whilst others stay and ‘rough’ it out. Those that do decide to stay must change some of their behaviors and habits to adapt to these environmental stressors.
Many animals enter a period of dormancy to safeguard against seasonal adversities. Dormancy happens before or when the adverse conditions have already begun. It is a temporary state of quiet inaction in which the animal can save its energy. Animals have cues for entering dormancy and different classes of animals favor different types of dormancy. Those in zoos live in more controlled environments and may or may not enter dormancy, however, they still have cues that make them behave a certain way during seasonal changes. The different types of dormancy include: hibernation, torpor, aestivation and brumation. All bears hibernate, right? Nope; a true hibernator is believed to weigh an average of 2.5 ounces.
Bears go into a deep sleep during the winter months called torpor. In torpor, the animal can wake up quickly and easily. Hibernation is when animals “sleep” through the winter. Whilst sleeping these animals will not wake up whether touched or moved even if there is a noisy racket going on. Hibernation is a prolonged period of torpor; body temperatures drop way below that of an animal in torpor, and with minimal energy expenditure.
The hedgehog is known to hibernate in cold or very hot temperatures. The summer version of hibernation is aestivation. The sweltering heat causes the hedgehog to go into hiding, using as little energy as possible. In aestivation the animals neither sleep very deeply nor remain dormant for very long. We have Fiona our African four-toed hedgehog, who remains active all year round as she lives in her habitat with comfortable temperatures of 75-85 degrees. At Lee Richardson Zoo we also have Namba, our resident sloth bear, who does not go into torpor since he comes from the warmer lowland forests of India.
Reptiles are ectothermic; they depend on an external source of heat. Fortunately, their internal cues, together with signs from their surrounding (such as drops in temperature, humidity and light), act as signals to go dormant. The ornate box turtle begins to fast and empty out his/her digestive system when they receive the signals that winter is coming. The goal is to expend the least energy in the cold icy temperatures when not consuming any food. They find a thermally appropriate hiding spot or hibernacula and reduce their metabolic rate significantly. This survival plan is called brumation. Smalls and Buck, the zoo’s two ornate box turtles who go on special educational trips, have areas to snuggle up and stay warm, together with their favorite dietary treats available all year round! For this reason, they don’t experience brumation.
Animals’ intensified food collections, building of fat stores, heavier coat growths, feather fluffing, change to white winter wear, dormancy, and other behaviors occur in response to seasonal changes. Winter can be bitterly cold, dreary, and intense for many wildlife. But through their biological makeup and cues from Mother Nature, the flora and fauna of the wild remains relentless, albeit in its sedentary mode, in surviving the wintry months.
Dera Naidoo is an educational aide at Lee Richardson Zoo.