Cultural Perspectives
By Tim Hazell, June 30, 2006 

La Vida Nocturna
The night lays lilies upon my 
burning roses
And cool cloths upon my feverish 
brow ...
How good the evening will be! It 
will have, for me, 
The luminous soul, the profound 
body, of a magnificent lover ...
—Delmira Augustini 

Time-keeping components in humans regulate how we respond to environments that consist of darkness and light, heat, cold and various phenomena. Impulses to seek shelter, nourishment, sleep and labor are triggered by innate mechanisms that may be located within the nucleus of the hypothalamus center of the brain.

Humans are diurnal, or daytime, organisms. We exhibit dominant phases of psychological and physiological activity during the hours of early morning to sunset, although individual preferences differ. Within the generalities of diurnal classification, many anomalies have led to distinctions such as “he or she is a morning or evening type.” People whose modalities suggest combinations of nocturnal and diurnal rhythms are intermediate, or crepuscular. Internal clocks regulating our autonomic and voluntary responses are referred to as circadian time-keeping systems. Creative, emotive springs are wound and released by impulses that may signal the onset of violent, antisocial behavior. When these motivations are positive, the same inner flows provide us with unparalleled flights of artistic temperament and achievement. Environmental and behavioral factors can alter the states of our seemingly innate entrainment dramatically.

One of the most unusual examples of extreme adaption to a nocturnal existence has been achieved by the owl monkey, or Aotus, a primate of neotropic regions such as the Amazon Basin. This ecological anomaly, with its beautiful markings and enormous liquid eyes, shares a similar social hierarchy with other diurnal primates, such as the macaque, spider and howler monkeys, but it has evolved remarkably individual lifestyle modalities. Preferences for locomotor activity, morphological development and habitat distribution are intrinsic with the owl monkey’s evolution of nocturnality. Its predilection for survival as a distinct genus within New World monkeys and its clan size and dietary choices stem from adaptive responses to predation pressures that differ between night and day. 

The Aotus dates back approximately 12 million years. This very rare and engaging jungle inhabitant may have shared a common diurnal ancestor with other species of primata. This was likely to have been a much smaller animal related to today’s tree shrews found at the base of protosimian and primate development. The versatile owl monkey has adjusted to lowland forest areas and high-altitude cloud ecosystems at 9,000 feet. Its range extends from Panama to northern Argentina and descends from the Andean wooded habitats of the montaña as it slopes towards the selva, or Amazon Basin, on its way to the Atlantic Ocean. Owl monkeys seek moderate tree cover at heights of 25 to 100 feet above the forest floor. Sleeping sites in hollow trees and intertwined creepers are jealously guarded and subject to competition from interspecific groups. 

The owl monkey is hardy, able to endure the extremes of cold and heat common to South America’s Andean environments and southern latitudes, where temperatures can vary from 40 degrees Celsius in the daytime to the freezing point after dusk. The genus is omnivorous, varying its diet of fruit and leaves with insect protein. The animal spends much of its nocturnal routine foraging vegetation and hunting for grubs. Aotus is monogamous, loyal to one mate, traveling through the green canopy in groups consisting of males, females and juveniles. Owl monkeys are highly intelligent and inventive, a common trait among primates of both Old and New World taxonomies. Offspring exhibit characteristics of affection, playfulness and attachment toward their parents. Their social system is well developed, and adult males carry out tasks of instructing younger members of the clan and defending the group from attack. 

Births occur once during the dry season, with another period following at the time of the monsoon. Immature owl monkeys remain under parental care, often carried by the males, until they achieve adult status two to three years later. They pursue a solitary bachelor existence, wandering until a suitable mate is found and the pair settles down to raise a family. Encounters with rivals are met with primate displays of bravado, clicking and grunting calls, back arching and mimetic gestures. Like many of its jungle cousins, the owl monkey is noisy, punctuating its hunting-gathering patterns with abrasive and strident vocalizations. Aotus marks its territory with an oily secretion found at the base of its tail. Scent and sound are important forms of primate intercommunication. 

Why do animals choose a nocturnal or night-oriented lifestyle? Advantages of concealment, absence of interspecific predation and foraging competition, better fields for uninterrupted night vision and movement are determining factors that may provide clues. The mysterious habits of bats and prosimians such as lemurs, raccoons and other creatures that emerge at dusk coincide with peculiar characteristics of light changes, as do the adaptive mechanisms of plants. Organisms possess capabilities for promoting or discouraging energy transfer. Plants change levels of morphological pigments and chloroplasts based on available radiant and visible luminescence, calibrating their movements according to positions of the sun and moon. For animals, interruptions in reproductive cycles are not linked directly to alterations in light patterns. However, as in humans, natural fluctuations of spectrum wavelengths, angles of incidence and seasons profoundly influence normal feeding patterns and matrixes of personality. 

Tim Hazell is a multidisciplinary artist in the areas of painting, music, theater, education, writing and research, specializing in Latin America. He may be contacted at hazel@unisono.net.mx or at his website, www.timhazell.com.