Category Animal World

Birds such as swifts, songbirds, seabirds, and sandpipers also sleep unihemispherically, with half of their brain shut. This helps them during long flights.

Keeping one half of the brain at rest, called unihemispheric slow-wave sleep, is in direct contrast to the typical situation where sleep and wakefulness are mutually exclusive states of the whole brain, the scientists say. “We have found that birds can detect approaching predators during unihemispheric slow-wave sleep, and that they can increase the use of unihemispheric sleep as the risk of predation increases,” they report.

The scientists studied groups of mallard ducks while they rested side by side and found that those at the edge of the group were significantly more likely to keep one eye open, with the closed eye being on the side of its nearest neighbour.

“We have found that birds sleeping under risky situations spend more time with one eye open and half the brain awake, and choose to direct the open eye towards a perceived threat,” added Dr Rattenborg.

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The dolphin sleeps with half its brain and one of its eyes shut at a time to keep a watch on approaching predators and other dolphins. After two hours or so, they shut the other eye and the other half of the brain, so both eyes and brain hemispheres get their due rest.

Dolphins have binocular vision (with their eyes sitting on opposite sides of their head), so the researchers trained one of the dolphins to recognized two shapes, either three horizontal red bars or one vertical green bar. They trained Say with her right eye first.

The scientists thought that because half of the dolphin’s brain would be asleep during testing, Say would only recognize the shapes with the eye connected to the conscious half of her brain. But she gave them a surprise: She trained her left eye on the shapes, even though that eye had not seen the shapes before.

Ridgway said this must mean that information is transferred between the two hemispheres of the brain.

The dolphins proved just as sharp with their eyes as they were with their ears: After 120 hours, they still saw the shapes.

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Many creatures sleep in a group for protection from predators. Puppies, squirrels, bats and meerkats sleep huddled together for warmth and protection.

Puppies will often sleep on their stomach so that they can get up quickly and not miss any playtime. If a dog sleeps on its back, it is either very comfortable, as it’s organs are the most exposed, or it’s trying to cool off. If your dog cuddles with you, it’s showing you affection and trust.

Many dogs will circle before laying down, which is what their ancestors the wolves would do to trample grass down to make a comfortable bed. Digging is something their ancestors would do to keep them warm in the winter and cool in the summer.

If your dog sleeps during the day, it may be due to boredom. If there’s any kind of noise and their ears perk up, it means that they are just waiting for something exciting to happen and weren’t in deep sleep.

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The large hairy armadillo sleeps for 20 hours a day. It is followed by the brown bat (19 hours), the North American opossum (18 hours), the python (18 hours) and the owl monkey (17 hours).

Armadillos live in temperate and warm habitats, including rain forests, grasslands, and semi-deserts. Because of their low metabolic rate and lack of fat stores, cold is their enemy, and spates of intemperate weather can wipe out whole populations.

Most species dig burrows and sleep prolifically, up to 16 hours per day, foraging in the early morning and evening for beetles, ants, termites, and other insects. They have very poor eyesight, and utilize their keen sense of smell to hunt. Strong legs and huge front claws are used for digging, and long, sticky tongues for extracting ants and termites from their tunnels. In addition to bugs, armadillos eat small vertebrates, plants, and some fruit, as well as the occasional carrion meal.

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Prey animals such as deer and sheep sleep for 3 to 4 hours per night, and sheep typically sleep in a herd for added protection. The giraffe sleeps only about 30 to 90 minutes a day. Because getting up from the ground takes them a little time, laying down makes them more vulnerable to predators such as crocodiles and lions. For this reason, they will often sleep standing up and may rest their head on their rumps. Researchers until the 1950s believed that they didn’t sleep at all. Many prey animals sleep less than predatory animals. However, this rule does not apply to all species.

Since they are a prey species, they sleep extremely lightly and tend to nap during the day. They’ll sleep within the herd, and some sheep will stay awake whilst others to sleep to act as alarm bells in case of predators.

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Did you know some animals sleep through summer? This is called aestivation. The equivalent during the winter months is hibernation, which you may be aware of. But humans neither aestivate nor hibernate. Some molluscs (e.g. Spanish snail), fish species (e.g. African lungfish in picture), reptiles (e.g. North American desert tortoise) and amphibians (e.g. waterholding frog) spend hot or dry period in a prolonged state of torpor or dormancy. They do so to avoid damage from high temperatures. They have to conserve energy, retain water in the body and ration the use of stored energy during aestivation. Animals that aestivate go through almost the same physiological processes as those that hibernate.

For going into hibernation or aestivation, animals go through the pre-preparation stage, where the animals store enough of food and water which may last for the long duration, but generally, the food is stored in the form of fat, which provides energy to survive.

These sleep proceeds gradually, as the metabolic activity, hearts beat and breathing rates also slows down. The electrical activity in the brain though stops, but still, the animals respond to stimuli such as sound, light, and temperature.

Picture Credit : Google