2. Some snails, such as desert snails, estivate while others hibernate.
We are all pretty familiar with hibernation when some animals conserve their energy by lowering their metabolism and ‘sleeping’ through the cold months. Some small species hibernate, but they also estivate. That is essentially the summer version of hibernation, in which animals enter a prolonged dormant state. Animals do this to protect themselves from the dryness and dangerously high temperatures. Snails can estivate for years. One instance of this was when a British museum worker found an Egyptian snail’s shell and assumed it was empty.
She went on to attach the shell to an identification card. Four years later, someone noticed there were traces of slime on the card. They put the shell into the water, and when the body came off the card, the workers were left stunned. As the cover came off, an alive, awake snail crawled out. The snail was estivating the entire time. Snails in colder climates can hibernate, while snails in hotter climates estivate during the summer months. Snails can decide to go into a deep sleep to avoid adverse weather conditions and periods when food is scarce. When snails go into either hibernation or estivation, they seal themselves safely inside their shells with a mucus layer that forms a hard cover over the opening.
With averaging just two hours of sleep a night, wild elephants are the lightest-known sleepers of any mammal. They might have little competition for this title in the giraffe. Wild elephants have more dangers and pressure to find food; wild animals tend to sleep less. The majority of the time, elephants will sleep standing up. Occasionally they would lie down when they require rapid eye movement (REM) sleep. During REM, the muscles usually relax, making it impossible to remain standing. However, this amount is so small that it doesn’t happen often.
Wild elephants are not too picky about where they sleep, but they are also on high alert when a predator presents itself. Surprisingly, their physical activity level during the day doesn’t directly impact how long they doze off. Bigger animals generally tend to sleep less, likely because they have to spend much time eating. Captive elephants tend to sleep a little longer, averaging three to seven hours a day. However, they do not have to worry about the threat of predators or where their next meal will come from. Researchers have uncovered that while elephants slept for an average of two hours a day, it was not consecutively. Instead, it was in four to five short bursts and occurred primarily between the nighttime hours. Each time the elephants slept in different places each night.
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