Winter Hibernation in the Moscow Zoo
Animals start getting ready for winter hibernation in advance - their food preferences change and their metabolism undergoes some changes, too: animals have to store enough fat under their skin to survive through the whole winter. Besides, they have to get ready with the place for hibernation - to dig a deep hole, to make a nest or a den.
The zoo inhabitants get ready for winter hibernation, and you can see they look and behave differently. The raccoons have put on some weight and they can seldom be seen outside their houses; they are moving slower and spend most of the time eating. When the air temperature drops, the raccoons will all gather in the same small house (to get warmer) and fall asleep. During the thaw in winter the raccoons can wake up to eat. The raccoon dog has similar way of winter hibernation. Bobak marmots prepare a special hole where there is a separate sleeping room, with hay on the floor. They may come out during the last warm days, but soon they will go inside and fall sleep until the spring. Bobak marmots have a very deep sleep, their heart beats much slower and they hardly breathe, while the body temperature decreases to 8° C.
The bear will go to sleep in the artificial den later, when it gets colder at the end of November. The body temperature in bears does not decrease and they can wake up easily, so the keepers try to be as quiet as possible near the den. The bears breeding time is connected with the cold period of the year: the mother bear does not eat anything till spring, but feeds the baby bears and cares about them. In spring, when they grow up a little, they will come out of the den.
The jerboas in the zoo sleep in refrigerators. During hibernation their body temperature may decrease to 8° C, their breath and heartbeat become almost unnoticeable. At this time they twist their bodies to look like a ball and move to the place with the appropriate temperature without waking up. In our zoo, the keepers prepare these animals for hibernation by lowering the temperature in the enclosure, giving them less juicy food and more seeds rich in fat, and monitoring their weight increase closely. The jerboa`s weight keeps increasing when they prepare for winter hibernation, and at the moment it stops, it means that the animal is ready to sleep. Then the jerboa is placed in a small wooden box with some soft material inside (to reduce noise and vibration) and put in a fridge. Some of the species with a very good hearing can go to sleep only if the fridge works noiselessly. Then, during the winter, the animals are regularly checked and their weight is controlled. When the weight goes down to the summer numbers, the jerboas are awakened by putting them back to a warm enclosure.
The fat dormouse goes to sleep in the open enclosure. The warm sleeping houses are furnished with wool inside (for example, camel wool or wolves` fur) for building nests. The animals decide when to go to sleep and when to wake up themselves.
Small Madagascar hedgehog tenrecs have imperfect thermotaxis (as in reptiles, the temperature of their body depends greatly on the environment temperature). They feel well at a temperature of +25°С and higher. During their breeding season environment temperature should be about +28°C. But at a temperature of +20°С they can only sleep for 5 months without waking up. At the Moscow Zoo they are kept in a special room where the needed temperature is maintained. These little animals usually rake aside their bedding and lie sprawled on the bare floor. In Nocturnal House visitors can see hedgehogs hibernating in their enclosures at natural temperatures which are rather low in winter. Many of the reptiles and amphibians and some insects also hibernate in winter.
Hibernating hazel dormouse (photo by O. Ilchenko)