Sleep in mammals Sleep in non-human animals

1 sleep in mammals

1.1 sleep duration
1.2 sleep in rodents
1.3 sleep in monotremes
1.4 sleep in aquatic mammals

sleep in mammals

sleeping japanese macaques.

mammals have wide diversity in sleep phenomena. generally, go through periods of alternating non-rem , rem sleep, these manifest differently. horses , other herbivorous ungulates can sleep while standing, must lie down rem sleep (which causes muscular atony) short periods. giraffes, example, need lie down rem sleep few minutes @ time. bats sleep while hanging upside down. inversely humans , rats, male armadillos erections during non-rem sleep. mammals engaged in polyphasic sleep, dividing sleep multiple bouts per day. higher daily sleep quotas , shorter sleep cycles in polyphasic species compared monophasic species, suggest polyphasic sleep may less efficient means of attaining sleep’s benefits. small species higher bmr may therefore have less efficient sleep patterns. follows evolution of monophasic sleep may hitherto unknown advantage of evolving larger mammalian body sizes , therefore lower bmr.

sleep thought conserve energy, though theory not adequate decreases metabolism 5–10%. additionally observed mammals require sleep during hypometabolic state of hibernation, in circumstance net loss of energy animal returns hypothermia euthermia in order sleep.

nocturnal animals have higher body temperatures, greater activity, rising serotonin, , diminishing cortisol during night—the inverse of diurnal animals. nocturnal , diurnal animals both have increased electrical activity in suprachiasmatic nucleus, , corresponding secretion of melatonin pineal gland, @ night. nocturnal mammals, tend stay awake @ night, have higher melatonin @ night diurnal mammals do. and, although removing pineal gland in many animals abolishes melatonin rhythms, not stop circadian rhythms altogether—though may alter them , weaken responsiveness light cues. cortisol levels in diurnal animals typically rise throughout night, peak in awakening hours, , diminish during day. in diurnal animals, sleepiness increases during night.

sleep duration

flying foxes, asleep

different mammals sleep different amounts. some, such bats, sleep 18–20 hours per day, while others, including giraffes, sleep 3–4 hours per day. there can big differences between closely related species. there can differences between laboratory , field studies: example, researchers in 1983 reported captive sloths slept 16 hours day, in 2008, when miniature neurophysiological recorders developed affixed wild animals, sloths in nature found sleep 9.6 hours day.

sleeping polar bears

as birds, main rule mammals (with exceptions, see below) have 2 different stages of sleep: rem , nrem sleep (see above). mammals feeding habits associated sleep length. daily need sleep highest in carnivores, lower in omnivores , lowest in herbivores. humans sleep less many other omnivores otherwise not unusually or unusually little in comparison other mammals. many herbivores, ruminantia (such cattle), spend of wake time in state of drowsiness, perhaps partly explain relatively low need sleep. in herbivores, inverse correlation apparent between body mass , sleep length; big mammals sleep less smaller ones. correlation thought explain 25% of difference in sleep amount between different mammals. also, length of particular sleep cycle associated size of animal; on average, bigger animals have sleep cycles of longer durations smaller animals. sleep amount coupled factors basal metabolism, brain mass, , relative brain mass. duration of sleep among species directly related basal metabolic rate (bmr). rats, have high bmr, sleep 14 hours day, whereas elephants , giraffes, have lower bmrs, sleep 3–4 hours per day.

it has been suggested mammalian species invest in longer sleep times investing in immune system, species longer sleep times have higher white blood cell counts. mammals born well-developed regulatory systems, such horse , giraffe, tend have less rem sleep species less developed @ birth, such cats , rats. appears echo greater need rem sleep among newborns among adults in mammal species. many mammals sleep large proportion of each 24-hour period when young. giraffe sleeps 2 hours day in 5–15 minute sessions. koalas longest sleeping-mammals, 20–22 hours day. however, killer whales , other dolphins not sleep during first month of life. instead, young dolphins , whales take rests pressing body next mother’s while swims. mother swims keeping offspring afloat prevent them drowning. allows young dolphins , whales rest, keep immune system healthy; in turn, protecting them illnesses. during period, mothers sacrifice sleep protection of young predators. however, unlike other mammals, adult dolphins , whales able go without sleep month.

comparative average sleep periods various mammals (in captivity) on 24 hours


a sleeping dog



horses – 2 hours
elephants – 3+ hours
cows – 4.0 hours
giraffes – 4.5 hours
humans – 8.0 hours
rabbits – 8.4 hours
chimpanzees – 9.7 hours
red foxes – 9.8 hours
dogs – 10.1 hours
house mice – 12.5 hours
cats – 12.5 hours
lions – 13.5 hours
platypuses – 14 hours
chipmunks – 15 hours
giant armadillos – 18.1 hours
little brown bats – 19.9 hours

reasons given wide variations include fact mammals nap in hiding, bats or rodents tend have longer, deeper snoozes on constant alert. lions, have little fear of predators have relatively long sleep periods, while elephants have eat of time support huge bodies. little brown bats conserve energy except few hours each night when insect prey available, , platypuses eat high energy crustacean diet and, therefore, not need spend time awake many other mammals.

sleep in rodents

a sleeping rat

a study conducted datta indirectly supports idea memory benefits sleep. box constructed wherein single rat move freely 1 end other. bottom of box made of steel grate. light shine in box accompanied sound. after five-second delay, electrical shock applied. once shock commenced, rat move other end of box, ending shock immediately. rat use five-second delay move other end of box , avoid shock entirely. length of shock never exceeded 5 seconds. repeated 30 times half rats. other half, control group, placed in same trial, rats shocked regardless of reaction. after each of training sessions, rat placed in recording cage 6 hours of polygraphic recordings. process repeated 3 consecutive days. during posttrial sleep recording session, rats spent 25.47% more time in rem sleep after learning trials after control trials.

an observation of datta study learning group spent 180% more time in sws did control group during post-trial sleep-recording session. study shows after spatial exploration activity, patterns of hippocampal place cells reactivated during sws following experiment. rats run through linear track using rewards on either end. rats placed in track 30 minutes allow them adjust (pre), ran track reward-based training 30 minutes (run), , allowed rest 30 minutes.

during each of these 3 periods, eeg data collected information on rats sleep stages. mean firing rates of hippocampal place cells during prebehavior sws (pre) , 3 ten-minute intervals in postbehavior sws (post) calculated averaging across 22 track-running sessions 7 rats. results showed ten minutes after trial run session, there 12% increase in mean firing rate of hippocampal place cells pre level. after 20 minutes, mean firing rate returned rapidly toward pre level. elevated firing of hippocampal place cells during sws after spatial exploration explain why there elevated levels of slow-wave sleep in datta s study, dealt form of spatial exploration.

in rats, sleep deprivation causes weight loss , reduced body temperature. rats kept awake indefinitely develop skin lesions, hyperphagia, loss of body mass, hypothermia, and, eventually, fatal sepsis. sleep deprivation hinders healing of burns on rats. when compared control group, sleep-deprived rats blood tests indicated 20% decrease in white blood cell count, significant change in immune system.

a 2014 study found depriving mice of sleep increased cancer growth , dampened immune system s ability control cancers. researchers found higher levels of m2 tumor-associated macrophages , tlr4 molecules in sleep deprived mice , proposed mechanism increased susceptibility of mice cancer growth. m2 cells suppress immune system , encourage tumour growth. trl4 molecules signalling molecules in activation of immune system.

sleep in monotremes

since monotremes (egg-laying mammals) considered represent 1 of evolutionarily oldest groups of mammals, have been subject special interest in study of mammalian sleep. studies of these animals not find clear evidence rem sleep, assumed such sleep did not exist in monotremes, developed after monotremes branched off rest of mammalian evolutionary line, , became separate, distinct group. however, eeg recordings of brain stem in monotremes show firing pattern quite similar patterns seen in rem sleep in higher mammals. in fact, largest amount of rem sleep known in animal found in platypus. rem electrical activation not extend @ forebrain in platypods, suggesting not dream. average sleep time of platypus in 24-hour period said long 14 hours, though may because of high-calorie crustacean diet.

sleep in aquatic mammals

northern sea lion pup adult female , male, largest of eared seals. habitat: northern pacific.

the consequences of falling deep sleep marine mammalian species can suffocation , drowning, or becoming easy prey predators. thus, dolphins, whales, , pinnipeds (seals) engage in unihemispheric sleep while swimming, allows 1 brain hemisphere remain functional, while other goes sleep. hemisphere asleep alternates, both hemispheres can rested. terrestrial mammals, pinnipeds sleep on land fall deep sleep , both hemispheres of brain shut down , in full sleep mode. aquatic mammal infants not have rem sleep in infancy; rem sleep increases age.

among others, seals , whales belong aquatic mammals. earless seals , eared seals have solved problem of sleeping in water via 2 different methods. eared seals, whales, show unihemispheric sleep. sleeping half of brain not awaken when surface breathe. when 1 half of seal s brain shows slow-wave sleep, flippers , whiskers on opposite side immobile. while in water, these seals have no rem sleep , may go week or 2 without it. move onto land switch bilateral rem sleep , nrem sleep comparable land mammals, surprising researchers lack of recovery sleep after missing rem.

cape fur seal, asleep in zoo

earless seals sleep bihemispherically mammals, under water, hanging @ water surface or on land. hold breath while sleeping under water, , wake regularly surface , breathe. can hang nostrils above water , in position have rem sleep, not have rem sleep underwater.

rem sleep has been observed in pilot whale, species of dolphin. whales not seem have rem sleep, nor seem have problems because of this. 1 reason rem sleep might difficult in marine settings fact rem sleep causes muscular atony; say, functional paralysis of skeletal muscles can difficult combine need breathe regularly.