DIURNAL ANIMALS: CHARACTERISTICS AND EXAMPLES - BIOLOGY - 2025

The diurnal animals are those that are active during the day and at night have a period of inactivity, sleep or rest. Some mammals, insects, reptiles and birds belong to this group.

In a 24-hour cycle, an animal's diurnal activity phase will depend on various factors; luminosity, temperature, the ability to obtain food using vision, among others. The time of year and the risk of being threatened by predators also influence.

Monarch butterfly. Source: Juan Emilio from Las Palmas de Gran Canaria, Spain, via Wikimedia Commons

The pattern of daytime activity is generally controlled by a circadian timing system. In mammals, the central nervous system is the master "clock" that controls daily physiological and behavioral rhythms, such as eating, sleeping, and waking.

Light acts on the central nervous system, causing changes in the organic response to external light and dark cycles. In addition, there are also "clocks" in peripheral organs, such as the pancreas and liver, which react to systemic signals.

Both systems, the central and the peripheral, are essential for the body to perform an adequate metabolic function.

characteristics

Visual acuity

Diurnal animals have excellent visual acuity. In addition, they can distinguish colors, because there are specialized cells called cones in their eyes. These structures are not very sensitive to light, but they are sensitive to colors.

In the vast majority of the species that make up this group there are two types of cones, spectrally different from each other. One of these is very sensitive to short wavelengths, while the other is very sensitive to long wavelengths.

However, some diurnal primates and humans have a third type of cone, known as the trichromatic retina.

Many diurnal animals, such as some birds and butterflies, require this clear view of the environment around them to locate food and recognize predators. The eagle can distinguish the slightest movement of its prey, even if it is very far away.

Environmental factors

There are elements in the environment that influence daytime activity patterns. Considering the hypothesis of circadian thermoenergetics (CTE), those animals that consume more energy than ingested, through sleep and food, would be more active during the day.

Some species vary their cycles depending on the seasons. An example of this is the blind mole rat (Spalax ehrenbergi). Its diurnal locomotor pattern has peaks of activity in summer between 8 in the morning and 1 in the afternoon.

In winter the behavior is different; it is active between 11 in the morning and 7 at night, turning into a nocturnal mammal.

Examples

Elephant

Elephant. Source: pixabay.com

During the day, these animals graze, drink water, plunge into rivers, roll in mud, and walk. The vast majority of elephants get little rest during the day, usually only for a few minutes.

The hours of these activities may vary according to the seasons of the year, even from one year to another.

Social activities and walks have high performance points during the dry and cold season, when adult males actively seek out females in heat. During hot and humid seasons, these behaviors decrease.

Diurnal behaviors possibly vary between elephants living in the same habitat. While some of these could spend an approximate 17% of the day on their feet, others in the same group could be more than 40%.

The same could happen with food; Some spend more than 23% of the hours of the day eating, and the rest of the herd would spend about 37% of their time feeding.

Chipmunk

Kaibaba squirrel, example of allopatric speciation

Squirrels are diurnal animals, because gathering their food and foraging depends on the ambient temperature. In the morning, the behavior exhibits two peaks, one in the early hours and the other in the afternoon.

During the day they rest, move and mate, presenting some seasonal variations in terms of time. In winter, the morning peak is wider than in the rest of the seasons.

During summer and winter, the busiest time in the morning is earlier than usual, and in the winter and fall it is later. In spring and summer there is a marked increase in the activity of this animal towards the hottest hours.

Butterfly

In Lepidoptera, being diurnal animals is possibly an ancestral condition. Previously it was thought that the ancestor of this genus was nocturnal, however new research presupposes that it flew during the day.

Almost all butterflies fly during the day, although some species are nocturnal, such as those belonging to the Hedylidae family. During the day, butterflies carry out most of their activities, including obtaining nectar. Mating in this species generally occurs in the afternoon.

Bee

The diurnal patterns of bees vary according to the seasons. In the summer, foraging is mainly enhanced in the mornings, while in the dry winter season it occurs after sunrise and before sunset.

The explanation of the search for food at night could be due to the greater availability of nectar at that time.

The flight, during the winter season, has a high incidence throughout the day, presenting a progressive decrease towards nightfall. In the summer the bees fly mostly in two stages; before sunrise and before sunset.

These animals have a daytime defensive behavior in their non-productive period. During the honey flow period, this behavior appears twice; very early in the morning and in the afternoon.

Primates

The vast majority of primates are diurnal, however some may be nocturnal or active at both times, with periods of rest interspersed.

There are also cases such as Aotus azarai, considered a strictly nocturnal species. However, research has described daytime behaviors in a group of these animals that live in Peru.

Diurnal primates, such as the Japanese macaque (Macaca fuscata), use this time to rest, feed, move from one place to another, groom themselves, socialize and mate.

These behaviors have variations in all seasons, except for inactivity during the reproductive period. At this time of year, the days are shorter, food is scarce and there is sexual competition between males.

The squirrel monkey (Saimiri sciureus), like the other members of the Cebidae family, is also an example of the primates that are mostly active during the hours of greatest sunlight. The only exception to that group is the Aotus.

In this way, this animal can have a better vision for communication and foraging. However, as they are diurnal animals they could face some problems, such as greater predation, stress due to high ambient temperatures, and greater competition in obtaining food.

Hawk

Peregrine falcon

This bird has great visual acuity that allows it to detect any movement of its prey, even if it is located at a great distance.

The hawk's eye has four types of color receptors that give it the ability to perceive not only the visible range of objects, but also the ultraviolet area of ​​the spectrum.

They also have other adaptations that allow it to detect polarized light or magnetic fields. This is due to the enormous number of photoreceptors that are located in the retina, almost 1,000,000 per square millimeter.

In addition to this, the hawk has a high number of nerves that connect the visual receptors with the brain and a fovea that magnifies the visual field.

Visual field

There are differences between the species of birds of prey, in terms of visual fields and the degree of eye movement in diurnal species. This suggests some sensory-type specializations that assist them in gathering visual information.

One of those that has the highest visual acuity is the red-tailed hawk, because they have the largest eye compared to other species.

The binocular field of Cooper's hawk is very wide, which favors its development in the habitat where it is located. This is closed and complex, and may require a greater binocular overlap in order to improve the detection of prey through vegetation.

Duck

Most ducks feed early and in the afternoon. The rest of the activities are carried out during the day, such as flying, bathing, resting, grooming and reproducing. There is an important difference between the hours in which these activities are carried out and the seasons of the year.

In the white-faced whistling duck, in the wet season, the month of greatest activity is April. During the dry season, the peak is in December.

Oxyura leucocephala uses most of its time resting. The remaining time is distributed between travel, feeding, flight and courtship, among others. Depending on the seasons and the reproductive season, these activities have a redistribution in the schedule.

Locomotion and rest occupy almost 89% of all activities in the winter. During mating time, the behaviors that dominated were locomotion, rest, and feeding.

Giraffe

The daytime activity of the giraffe varies almost daily, in addition to having specific aspects of each species. It is influenced by various factors, such as reproductive status, predators, climate, and the social group it is a part of.

In general, rumination in this mammal takes place at different times of the day. This could be a characteristic of ruminants, as a result of their eating habits.

The female giraffe spends more time grazing than the male, which may be associated with a higher energy requirement associated with gestation and the lactation period.

Woodpecker

Woodpeckers are diurnal birds, resting at night inside holes or crevices. This animal enters its nest around 20 minutes before sunset. Both the female and the male use the same nest, although they are located separately.

Most of the day it is in the trees, being able to occasionally descend to the ground to feed. You can also move to nearby trees or other areas where there is a greater abundance of food.

Heron

In these wading birds, foraging occurs during different hours of the day, varying the level of frequency of activity in both the wet and dry seasons.

Within the group of herons that carry out the vast majority of their work during the day is the white heron (Ardea alba). This bird fishes for long hours in the day, returning to its nest at dusk, where it sleeps until dawn. However, if the moon illuminates the night, it is likely that some are active.

The black-headed heron (Ardea melanocephala), native to Africa, is a diurnal species, which is found almost all the time in the wetlands hunting for food. However, occasionally I might fish at night.

References

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