A Matter of Time

Philosopher's view of time - Creatures of the Night

“I often think that the night is more alive and more richly colored than the day.” Vincent Van Gogh

Not everything that roams the earth shares man's preference for daylight and daylight activities.  Our eyesight has adapted itself to light-saturated environments, making it natural and practical for humans to be active primarily during the day. Many people struggle with fears of the dark – perhaps due to the difficulties we have seeing well in it. Such fears can usually be traced back to a fear of the unknown, or, sometimes, a fear of the creatures that dwell in it. To us, “creatures of the night” often seem foreign and we develop inaccurate, derogatory stereotypes often due to the fact that we don’t spend enough time trying to truly understand them.

Advancements in technology have played the biggest role in allaying some of these fears by allowing us to probe deeper into the darkness than ever before. Even something as simple as sound recording equipment has made the discovery of ultrasonic communication primarily among small mammals possible.  It has also made echolocation, also called bio-sonar, possible in animals such as dolphins and bats. Echolocation is the equivalent of listening for echoes from sound waves the animal emits and then analyzing them. Ultrasonic, on the other hand, refers to anything outside of the range of audible sound.  Animals that utilize it can hear very high frequencies and use it for various things such as calling their mates or locating prey.

Humans are diurnal. That means that by nature, we are active during the day and sleep at night. Animals that do the opposite by adapting to the dark are nocturnal. These animals generally have superior sensory abilities, and can hear and see much better than humans can. Most rodents, fish, some types of birds, and deer, are neither diurnal nor nocturnal, but rather do the majority of their hunting or feeding at the twilight hours. Animals with behaviors like this are known as crepuscular and are most active at dawn and dusk.

Nocturnal tendencies are not restricted to a given set of environments either. Everything from European tawny owls to fungus that can grow up to 8 cm (3 in) in half an hour as darkness approaches can be found in the same peaceful woodland. Various kinds of insects, Roe deer, Nightingales, fox, long-eared bats, European badgers, raccoons, and weasels inhabit deciduous forests, all the while wolverines, European polecats, wolves, and snowshoe hares take over coniferous forests at night. In open land areas, Red Deer, European harvest mice, European brown hares, common shrews, moles, the common toad and various kinds of spiders thrive in the darkness.  Cats control bird populations in cities, herons stalk goldfish in garden ponds, and rats scurry through garbage, all under the protective shield of night. Swans, crayfish and eels make fresh water areas bustle after the sun goes down, and grey seals, most crustaceans, violet jellyfish, and some dolphins make the depths of the sea active when we are in our world of sleep.

These unique species of animals don’t chose to be active at night, but rather their internal clocks have allowed them to evolve in this way. These clocks can be better described as circadian rhythms, stemming from the Latin “circa diem,” or, “about a day.”

Some studies have shown that when mice are kept in a laboratory where the temperature is kept constant and the light is controlled, the mice's internal temperature, metabolic rate, and hormone levels increase when it is darker, while they remain at rest throughout the artificial “day” that the technician's create for them. Amazingly enough however, is that even if a dim light is kept on continuously, or the mouse is kept in total darkness at all times, this pattern of activity and rest persists. Not only that, but it persists in roughly a twenty-four hour cycle, sometimes rising to 22 hours or dipping to 25 hours, depending on the animal. The two most important factors affecting all of this is time and the animal's circadian rhythm.

The cycle seen here in the case of the mouse applies to all animals, including humans, and is in fact the reason we experience jet lag. The mouse could adjust to a new schedule if the twelve-hour light and dark periods were slowly modified over a period of weeks. With jet lag, however, people are expected to make this adjustment instantly as they cross over time zones, often resulting in negative side effects. Plants too experience this cycle: some look old and wilted after nightfall, while others seem to suddenly appear full-grown. Any change in day length may also alter the frequency at which plants flower, or alter other of their photoperiodic responses.

Aside from circadian rhythms, there are other life patterns that also effect plants and animals, including annual rhythms, continuously consulted clocks, and internal timers. Yearly clocks persist no matter what other conditions may arise, allowing some forms of water fowl to molt at ten month intervals, signaling many kinds of marine animals to breed at the same time each year, and indicating the appropriate time for migratory birds to take flight. Due to another kind of clock known as the “continuously consulted clock,” animals such as honeybees know when flowers are open and ready for them, and only visit them at certain times throughout the day. Yet another type of internal clock controls hibernation. The starting and end points of such dormancy are known ahead of time by a sort of mechanism working within the animal. More so than with humans, perhaps, the natural cycles of time influence nearly all aspects of the lifestyles of wild life.

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