--- title: How animals sleep: half-asleep dolphins, standing horses, short-sleeping giraffes and birds that nap in the air — a lesson of Mova's school · trees and pragmatics description: «How animals sleep: half-asleep dolphins, standing horses, short-sleeping giraffes and birds that nap in the air», a lesson of the biology course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: It is asleep, but only with half its brain: the other half --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/) [home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [school](https://md.mova.elamur.ai/free/en/corpora/school/) / [Biology](https://md.mova.elamur.ai/free/en/corpora/school/biology/) / How animals sleep: half-asleep dolphin… # How animals sleep: half-asleep dolphins, standing horses, short-sleeping giraffes and birds that nap in the air Lesson 390 of the biology course of Mova's primary school: 15 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: [the lesson at school](https://md.mova.elamur.ai/free/en/school-run/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/). - [1](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/1/) — It is asleep, but only with half its brain: the other half stays awake to steer, come up to breathe and watch for danger. - [3](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/3/) — Ducks at the ends of a row keep the outward eye open, frigatebirds nap for seconds while gliding over the ocean, and horses doze standing up so they can run if danger comes. - [4](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/4/) — Big plant-eaters like giraffes and elephants sleep only a short time, because they need many hours to eat and lying down can be dangerous with lions about. - [5](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/5/) — Animals that eat poor food, like koalas, or must wait for their food, like bats, sleep a lot to save energy. - [6](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/6/) — Some famous sleep facts are myths, because they came from animals in zoos, which have less to do and no danger. - [7](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/7/) — A dolphin can sleep with one half of its brain while the other half stays awake, and the halves take turns. - [8](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/8/) — Ducks at the edge of a sleeping row keep the outward eye open and that half of the brain awake, while ducks in the middle sleep more deeply. - [9](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/9/) — Frigatebirds can fly for weeks without landing; scientists found they slept less than an hour a day while flying, mostly in seconds-long naps, but about twelve hours a day on land. - [11](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/11/) — Wild giraffes sleep in short bits adding up to about half an hour to a few hours, often standing, because getting up takes them a long time. - [12](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/12/) — Scientists reported that wild sloths sleep about nine or ten hours a day, not twenty; the big number came from sloths in zoos. - [13](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/13/) — Wild elephants in Africa were reported to sleep only about two hours a night, mostly standing, and some nights not at all. - [14](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/14/) — Chinstrap penguins guarding nests were reported to take over ten thousand tiny naps a day, each a few seconds long, adding up to about eleven hours. - [15](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/15/) — Fish rest by slowing down and hovering still; they have no eyelids, so their eyes stay open, and some parrotfish sleep in a bubble of slime. - [16](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/16/) — Koalas sleep or rest about 18 to 22 hours a day, and some bats sleep about 20 hours. - [17](https://md.mova.elamur.ai/free/en/corpora/school/biology/390-how-animals-sleep-half-asleep-dolphins-standing-horses-short-sleeping-giraffes-and-birds-that-nap-in-the-air/17/) — Sleeping a lot saves energy when food is poor or comes only at certain times. - ← previous: [How scientists test animal minds: the mirror test, puzzle boxes and Clever Hans](https://md.mova.elamur.ai/free/en/corpora/school/biology/389-how-scientists-test-animal-minds-the-mirror-test-puzzle-boxes-and-clever-hans/) - next →: [Do animals dream? Twitching dogs, replaying rats and colour-changing octopuses](https://md.mova.elamur.ai/free/en/corpora/school/biology/391-do-animals-dream-twitching-dogs-replaying-rats-and-colour-changing-octopuses/) - ↑ back to [Biology](https://md.mova.elamur.ai/free/en/corpora/school/biology/)