Regardless of their preferred mode, bats, elephants, frogs, honeybees, humans and more have something in common: They all sleep. In fact, scientists have yet to find a truly sleepless creature.
Animals that don't need sleep (bullfrogs and dolphins)
Upside-down jellyfish
Suppose the definition of sleep requires your brain to be in a state of inactivity. In that case, animals like the upside-down jellyfish that have no brains technically can't sleep.
YES, THEY DO - but not in the sense we understand sleep. Research conducted by James and Cottell into sleep patterns of insects (1983) showed that ants have a cyclical pattern of resting periods which each nest as a group observes, lasting around eight minutes in any 12-hour period.
While mammals and birds possess the prerequisite neural architecture for phenomenal consciousness, it is concluded that fish lack these essential characteristics and hence do not feel pain.
Snails need moisture to survive; so if the weather is not cooperating, they can actually sleep up to three years. It has been reported that depending on geography, snails can shift into hibernation (which occurs in the winter), or estivation (also known as 'summer sleep'), helping to escape warm climates.
Horses, zebras and elephants sleep standing up. Cows can too, but mostly choose to lie down. Some birds also sleep standing up. Flamingos live on caustic salt flats, where there's nowhere they can sit down.
Mother octopuses never meet their babies, as they stop eating and die of starvation before the young hatch.
However, if a kangaroo rat drinks water, the necessary bodily liquids and vitamins are flushed out, and it dies as a result of dehydration.
The swamp wallaby is the only mammal that is permanently pregnant throughout its life according to new research about the reproductive habits of marsupials. Unlike humans, kangaroos and wallabies have two uteri. The new embryo formed at the end of pregnancy develops in the second, 'unused' uterus.
Most animals that procreate through parthenogenesis are small invertebrates such as bees, wasps, ants, and aphids, which can alternate between sexual and asexual reproduction. Parthenogenesis has been observed in more than 80 vertebrate species, about half of which are fish or lizards.
Koalas. Hats off to the (somewhat disputed) king of sleep: the Koala bear. They've been reported to sleep up to 22 hours a day in captivity, over 90% of their lives.
Sharks can sleep, and often opt to keep their eyes open while they do, according to new research published in Biology Letters. Because some sharks must swim constantly to keep oxygen-rich water flowing over their gills, it has long been rumored that they don't snooze at all.
Snakes actually sleep with their eyes 'open', as they don't have eyelids to close their eyes. Instead, their eyes are covered with transparent scales which protect their eyes and stop them becoming dry – these are called 'spectacles'.
Spiders usually have eight eyes but few have good eyesight.
Some spiders have median eyes that can detect polarised light and they use this ability to navigate while hunting.
While it can vary quite a bit, most snakes tend to spend much of their time asleep. The most commonly cited figure is 16 hours a day, though some species have been known to spend up to 22 hours!
When they're not looking for food, mosquitoes perch for long periods of time to conserve energy. But researchers discovered a subtle telltale sign the mosquitoes were asleep. “When mosquitoes enter a sleep-like state, their hind legs droop and their body comes closer to the surface,” Ajayi said.
So, while most sharks will be 100% fine if they stop swimming, a few iconic species such as great white sharks, whale sharks, hammerheads and mako sharks would suffocate without forward motion or a strong current flowing towards their mouths.
In sharks, the tongue is a small, flattened structure that is attached to the floor of the mouth. It is made of cartilage, just like the rest of the shark's skeleton, and it is covered with tiny, tooth-like structures known as papillae. These papillae help the shark to grip and manipulate food in its mouth.
Myth #1: Sharks Must Swim Constantly, or They Die
This allows them to rest on the sea floor and still breathe. However, sharks do have to swim to avoid sinking to the bottom of the water column. The ability to move up and down freely in the water column is, in fact, one of the extraordinary adaptations of sharks.
Three-toed sloths are some of the slowest and seemingly laziest creatures in the world. Instead of evolving to eat more, they evolved to do less.
Sloths are known for being slow creatures, so it makes sense that they're not only slow but sleepy too. The brown-throated three-toed sloth (Bradypus variegatus) sleeps a lot! In fact, this sloth sleeps for about 14 to 16 a hours a day.
While research tells us that women need more sleep than men, it's also the case that women tend to sleep slightly longer than men — by just over 11 minutes. The bad news, however, is that women's sleep may be lower quality than men's, perhaps due to differences in how they spend their day.
For example, the great majority of tunicates, pulmonate molluscs, opisthobranch, earthworms, and slugs are hermaphrodites. Hermaphroditism is also found in some fish species and to a lesser degree in other vertebrates. Most plants are also hermaphrodites.
Many species of fish, like the kobudai, are known as “sequential hermaphrodites”: they can switch sex permanently at a specific point in their lives. The majority of “sequential hermaphrodites” are known as “protogynous” (Greek for “female first”): they switch from female to male.