Creature Feature: Animals Also Dream

Sleep, the essential restorative, is imperfectly understood in human beings and even more mysterious in nonhuman animals. However, much of the little we know about our sleeping habits does seem to apply to those of our pets as well.

Studies have shown that the content of an animal's slumber consists of periods of slow-wave sleep interspersed by shorter rapid-eye-movement phases.

In humans, REM sleep is associated with dreaming. Since the brain activity of animals during REM sleep is similar to a human's, it is reasonable to conclude that they, too, dream.

Animals, Too, Need Dreams

Another indicator that animals do dream is that sleep deprivation not only causes them to become physically ill but also mentally unstable.

It seems likely that dreaming fulfills the same purpose for our pets as it does for us, giving the brain a chance to process memories of past experiences.

Vegetarians, take note: Creatures high on the food chain get more sleep. Predators such as dogs, cats, and humans who consume protein-rich meat can afford the luxury of sleep. Herbivore prey animals, like cattle, sheep, and horses, must eat almost ceaselessly to obtain the requisite nutrition.

And, of course, they must also stay alert and vigilant lest they become protein for the predators.

Cats, consummate hunters that they are, are champion snoozers. They sleep away 60 to 80 percent of their lives.

It has been estimated that a typical 9-year-old cat will have been awake for only a mere three years of its life.

Unlike humans, who sleep for large blocks of time, cats take, well, cat- naps. They intersperse their active day of hunting or, more likely, hanging around the can opener, with many naps of around a 40-minute duration.

Interestingly enough, though cats are widely reputed to be nocturnal hunters who are active at night, recent studies have shown that the bulk of catnaps, 75 percent, occur during nighttime.

Lost In A Dream

A napping cat first goes into slow-wave sleep, during which it is resting but still very quick to awaken should something interesting occur.

If the slow-wave phase is undisturbed, the cat will enter the REM state, and remain in it for about 10 minutes. During this sleep phase, the cat is quite oblivious to its surroundings.

Observant owners frequently note that the cat seems quite lost to its dreams, quivering its paws and whiskers and sometimes muttering softly.

Sleep Cycle Of Dogs

Dogs do not spend as much time sleeping as cats do, but they do have very similar sleep patterns.

Many dog owners assume that their dog sleeps through the night just as they do, but a study conducted at Cornell University revealed that canines only spend about 60 percent of nighttime hours asleep.

Research has disclosed that dogs have a typical sleep-wake cycle of 104 minutes, consisting of 56 minutes awake and 48 minutes asleep.

Given the dissimilar slumber habits of dogs and humans, it is a tribute to the obligingly patient nature of dogs that they let us sleep undisturbed through the night.

Lydia's Dream Life

Dogs give the appearance of having an active and exciting dream life. Their legs move as if they're running, their whiskers twitch, and they may give voice to yips or soft barks.

Obviously, thrilling events are taking place in the Land of Nod.

My dog, Lydia, seems to have a recurring dream of greeting near and dear friends. Her only obvious REM activity is a happy, sustained tail-wagging.

However, as endearing and intriguing as a dreaming dog might be, the old clich‚ about letting sleeping dogs lie contains a great deal of truth; a dog startled from REM sleep will often snap or snarl.

Horses Take Turns

Herbivores, because of their vulnerability to predation, have evolved to need less sleep. When in a group, these animals will often take turns napping, a survival tactic that insures that there is always at least one animal on watch to give warning to the sleepyheads.

Horses, lacking the horns and tusks of most other herbivores, have only their swiftness and agility as a defense. Despite their imposing appearance and considerable power, they fight only when cornered. Fleeing the scene is their preferred defense.

Since rising from a prone position takes at least two seconds, and two seconds are too many when the lion is on your tail, horses evolved with the ability to sleep standing up.

On The Side: Deep Sleep

Horses may sleep standing up, but they cannot dream while standing up. REM sleep can only occur when an animal (of any species) is prone on its side.

Horses need REM sleep as much as any animal, so they will stretch out for short 30-minute snoozes throughout a 24-hour period, usually spending a total of about two hours a day lying down.

Lying down is not as restful for them as for us, for not only does a prone position conflict with the horse's instinct to be highly mobile, but, due to the considerable weight of an adult horse, their respiratory and circulatory systems are negatively affected by the position.

Ironically, sleeping lying down demands more energy from the horse than sleeping standing up. Quite possibly this is further indication of the necessity of dreams.

When in REM sleep, horses give off the same physical indications as dogs and cats do that they are dreaming.

Some horses can be quite lively and noisy during REM sleep. While spending many nights in the barn during foaling season, I witnessed many different styles of REM sleep among horses.

One young mare in particular, Queenie, seemed to have especially exciting dreams.

During her waking hours, Queenie was a rather mellow and self-effacing creature, but in her dreams she seemed to become considerably more dramatic.

She'd whinny softly and repetitively, toss her head spiritedly, and move her legs in a prancing pattern.

No Nightmares

What I wouldn't give to know what was in that head at that moment!

It is unlikely that we will ever know for sure if our animals dream as we do.

Happily, though, researchers have never reported an incidence of nightmares among animals. No creature has ever been reported jolting awake in an inexplicably fearful state.

So, if animals do indeed dream, we can reasonably assume that all their dreams are sweet.