How do Marine Mammals Sleep?

Sleep is incredibly important to higher vertebrates such as reptiles, birds, and mammals. Continued disruption of sleep—as the parents of newborns and the CIA know well—is a torture technique. And while the function of sleep is not totally understood, we do know that it’s absolutely vital to the health of animals.

During a whale-watching trip years ago out of Half Moon Bay, at around 3:30 in the afternoon—just about the time I like to take a nap—I saw a very light blow, or exhalation, from a whale. As we approached, we saw that the whale wasn’t swimming. We turned off our engine and drifted near the stationary whale for over an hour. We watched silently as the animal slowly sank beneath the surface, disappearing for 90 seconds, resurfaced in exactly the same location, took a very light breath, and then sank back down—over and over. My conclusion was that the animal was asleep. But breathing is not an involuntary autonomic response in whales as it is in terrestrial animals. How can you sleep if you’re a voluntary breather like this whale?

Studies of both captive and wild cetaceans have revealed a most fascinating adaptation: Half the brain appears to stay awake while the other hemisphere drops into what we call slow-wave sleep, or deep sleep. There are basically two different kinds of sleep as measured by electrical activity in the brain—REM (rapid eye movement) sleep and non-REM sleep. In non-REM sleep there are three stages, each characterized by decreasing frequency of electrical impulses. During stage III (slow-wave sleep), memories are consolidated into the neural network, and essential repair to bodily systems takes place.

Studies on captive bottlenose dolphins show that each side of the brain gets a total of about four hours of “sleep” in short stints as the opportunity arises over 24 hours. Half of the brain nods off and the opposite eye closes while the other wakes up and helps the animal survive. This is called unihemispheric slow-wave sleep or USWS. Survive how? This evolutionary transformation allows the animal to safely breathe, consolidate memories, do essential bodily repair, interact with other members of its social group and stay cognizant of potential dangers like predators or large vessels approaching.

But what about pinnipeds—true seals (such as harbor seals) and eared seals (such as California sea lions) that can be found sleeping on land but spend many months at a time in the open ocean? Even though DNA analysis indicates that these two mammalian lineages share a common ancestor, only the eared seals exhibit USWS. But for some reason that remains unclear, true seals do not undergo USWS but are nonetheless very successful at getting the necessary “sleep” in their watery world through bilateral slow-wave sleep and holding their breath. An elephant seal, for example, can hold its breath for more than an hour. Other aquatic mammals, such as the Amazonian manatee, also have been shown to have USWS.

REM sleep occurs simultaneously in both hemispheres and is the final stage during the sleep cycle characterized by dream activity, increased breathing and respiratory rate. The electrical activity of the animal’s brain during REM is quite similar to that when it is awake. While pinnipeds experience something like REM while on land, it turns out cetaceans do not go through REM sleep, so I reckon they don’t dream.

It’s 3:30 pm—time for that nap essential to my health. At least that’s my story and I’m sticking to it.

The Great American Exchange

For millions of years, North and South America existed in geographic isolation — there was no Central America. North America began as part of the supercontinent Laurasia — that is basically all the land in the northern hemisphere. And South America began as part of another huge continent, which included Australia and Antarctica. In these separate regions plants and animals evolved in “splendid isolation” as Alfred Wallace first described it in the 1800s.

But beginning around three million years ago, volcanic activity created the Isthmus of Panama. The land that arose “suddenly” connected these two huge landmasses and caused one of the most remarkable events in the history of our planet. Abruptly there was a gigantic swap of fauna from one region to another, today known by biologists as the Great American Exchange. Camels, native to North America, headed south and evolved into llamas and vicunas. Deer, tapirs, cougars, skunks and foxes also went south into new territory and radiated out into a large number of species. Overall the exchange between north and south was quite uneven. The North American species basically out-competed, dominated and caused the extinction of many of South America’s animals.

On the contrary, only a few species from South America succeeded in conquering the Northern Hemisphere. The modern descendants of these southern mammals are armadillos, porcupines and opossums. There are no armadillos here but porcupines are a native California critter. The opossums we see in the Bay Area were allegedly introduced into San Jose in 1910. Goodness knows why — perhaps Granny was missing some of that possum stew she fondly remembered from back home in ‘Kentuckee’. At any rate these marsupial mammals have landed fully in California and thriving in our suburbs.

So last week when I passed several flattened on the road, I was reminded of those Grateful Dead lyrics — “what a long, strange trip it’s been” at least for those possums.


“What’s the largest underground-dwelling invertebrate in the Bay Area? How does it live?” Paul, Berkeley


Well Paul that has to be the tarantula. There are 15 or so species of “tarantulas” in California are in the genus Aphonopelma in a family called the Mygalomorphs. But our spiders are not true tarantulas. The original Lycosa tarantula is found only in Europe and is a member of the wolf spider group.

Every fall the male tarantulas leave the protection of their burrows and search for females. Males are easily identified by the presence of giant pedipalps – large leg-like appendages near the mouth. The male constructs a sperm web where he deposits some seminal fluid. He then takes up a little of that sperm into special reservoirs on the tips of his pedipalps. Now he is ready to roll. Normally these spiders are nocturnal but during the breeding season the males are out night and day cruising for females.

When he finds a female burrow he taps the entrance with his legs and entices her to emerge. This is a dangerous operation. Tarantulas have been known to kill and eat animals much larger than themselves including small rodents, lizards, and even other tarantulas. The female may charge him with her fangs exposed. He grabs her fangs with special spurs on the inside of his front legs. He then flips her on her back and rhythmically uses his pedipalps to brush past her sternum. (Are you beginning to breathe hard here?). He places his packet of sperm in her genital pore and makes a hasty retreat; he doesn’t want to get eaten. In humans mating occasionally follows dinner, in some spiders dinner occasionally follows mating.

The male tarantula will soon die; his job is done. Females on the other hand have been known to live over 20 years! Soon she will plug her burrow and spend the winter safe and secure far underground. Deep in her lair the following spring she will spin a thick egg sac and deposit 500 to 1000 eggs in it. The spiderlings hatch in about a month; the mother tears a small hole in the sac for her babies to emerge. They hang out with her for a while before leaving the burrow. And the cycle for another amazing animal begins anew.

Tarantulas take their name from the small Italian town of Taranto, where they were once numerous. Here tpeople believed that the bite of the tarantula was fatal. Just preceding death the victim entered a state of melancholy called tarantism. In order to survive death you had to listen to music during this tarantism. Not just any music, but the right music, which varied according to the particular whims of the victim.

The doctor would lead the patient into a room where an orchestra was assembled. The doctor would then take the musicians through a few numbers. The patient would be unmoved until the right tune was struck. With a wild look in the eye, he’d get up and begin an uncontrolled frenzy, leaping about, flailing his arms and shrieking (I used to see similar behavior at a Grateful Dead concert). Finally dripping with sweat he’d drop, totally exhausted, but completely cured. The patient would have recovered anyway. Tarantula bites are not fatal, in fact it’s pretty hard to get one to bite you. But it was probably a good opportunity to act out some fantasies.

The best location to view this autumn phenomenon is the inner coast range mountains like Diablo and Hamilton. There is even a tarantula festival in Henry Coe State Park Coe Park on October 6.
I am not sure which band is playing there however.

Wild Animal Behavior

Q – How have humans influenced wild animal behavior?

A – Most of the world’s 5,000 or so species of mammals are already nocturnal, so the effect of urbanization on their circadian activity is probably nil. Actually, even the nocturnal animals are mostly crepuscular in activity; that is, they have a burst of feeding, moving, and mating at the twilight times—dawn and dusk.

I have noticed in park settings that our local black-tailed deer are active in the early morning, take it easy at midday, and then begin feeding again in the afternoon. Of course, they are active at night as well. In “shruburbia,” where homeowners, children, and dogs are out and about during the day, the deer tend to visit only under cover of darkness to munch those well-watered and delicious roses. So they have altered their diurnal (daytime) activity slightly.

A more obvious change in behavior is with coyotes. These wonderfully adaptive wild canines have different social strategies depending upon the habitats in which they live. In wide-open undisturbed settings, they form monogamous pairs and maintain an active social life with related clans. The offspring often stay with their parents for one or two years and help feed their newborn brothers and sisters. A mated pair may be together for years. They frequently hunt in the day and vocalize both night and day. Early settlers in the West reported seeing very large coyote aggregations (75 or more) in areas of abundant game.

However, in urban zones, or in areas that they are just colonizing, coyotes adopt entirely different lifestyles. They do not interact much with each other, and they don’t form long-lasting monogamous pairs. Often the mother coyote is left to feed the young kits all by herself, while the male keeps more or less to himself. Male territories are larger than the females’, and males may move through several territories before mating. In such uncertain and novel settings, and where humans are present, coyotes vocalize very little, if at all, and don’t move around much in the daytime. In other words, they keep a very low profile. In fact, human residents can be blissfully unaware of the presence of coyotes in the neighborhood until their beloved pet cat is snatched right off the back porch.

Michael Ellis – Ask the Naturalist – Bay Nature Magazine


Q: How does photosynthesis occur in plants that are not obviously green, such as ornamental plum trees with deep purple-colored leaves?  What other chemicals are involved in photosynthesis besides chlorophyll? –Paul, Santa Cruz

A: Photosynthesis is that very elegant chemical process begun 4 billion years ago that jump started all life as we know it on our planet. The word literally means photo = light + synthesis = to put together. Basically six molecules of water plus six molecules of carbon dioxide in the presence of light energy produces one molecule of glucose sugar and emits six molecules of oxygen as a by-product. That sugar drives the living world. Animals eat plants, then breath in oxygen which is used to metabolize the sugar, releasing the solar energy stored in glucose and giving off carbon dioxide as a by product. That is it.

GREEN PLANTS DO THIS: 6 CO2(g) + 6 H2O(l) + light → C6H12O6(aq) + 6 O2(g)

ANIMALS DO THIS: C6H12O6 (aq) + 6O2 (g) → 6CO2 (g) + 6H2O (l) + energy

All photosynthesizing plants have a molecule called Chlorophyll a. This molecule absorbs most of the energy from the violet-blue and reddish-orange part of the spectrum. It does not absorb green; which is reflected back to our eyes. There are also accessory pigments which absorb energy that Chlorophyll a does not. These are chlorophyll b and carotenoids. There are at least 600 known carotenoids; they are split into two classes, xanthophylls and carotenes. They absorb blue light. Xanthophylls are yellow and carotenes are red and orange. Anthocyanin while not directly involved in photosynthesis is an importan pigment that gives stems, leaves, flowers or even fruits their red color.

Many ornamental plants are selected because of their red leaves – Japanese plums, Norway maples, purple smoke bush to name just a few. Obviously they manage to survive quite well without green leaves. At low light levels leaves with chlorophyll a and b are most efficent at photosynthesis. On a sunny day however there is essentially no difference between red and green leaves in trapping the suns energy. I have especially noticed the presence of red in brand new leaves and in many tropical plants. Anthocyanins apparently prevent damage to leaves from ultra intense light energy by absorbing UV light. There is also evidcence that unpalatable compounds are often produced along with Anthocyanins which may indicate to potential herbivores the presence of toxins.

There is still much research to be done in this arena and botanists have been wondering about red vs green leaves for the past 200 years! So you are in good company, Paul

Michael Ellis – Ask the Naturalist – Bay Nature Magazine

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