A Closer Look At Some Of The Animals Adapted To Daytime Living
The term diurnal is used to describe animals that are mostly active during the day. As you can imagine, there are lots of diurnal animals, including us humans. But there are many that choose to be more active at other times of day too.
So why do some animals follow a diurnal lifestyle, and other choose to be nocturnal? What are the advantages and are there any notable differences between species that choose one over the other?
Here are some examples of diurnal animals, as well as an overview of the differences between diurnal and nocturnal with relation to the circadian rhythm.
Diurnal Vs Nocturnal And The Circadian Rhythm
The terms diurnal and nocturnal both have their origins in Latin. Diurnal comes from ‘diurnus’ which means day, while nocturnal comes from ‘nocturnus’ which is Latin for ‘belonging to the night’. From there, the words are simply translated into modern English.
In each case, animals follow a different circadian rhythm, depending on their preference for daylight or darkness. But what is the circadian rhythm?
Well, circadian rhythms are basically the daily (24hr) cycles that determine the lifestyle patterns of an animal. Including patterns of sleep, wakefulness, feeding and biological cycles. For instance, the circadian rhythm can determine when the body will start to produce more melatonin before sleep. Or when the ‘triple heater’ will kick in, or the time of day when you are most alert or your metabolic rate at a specific time. They tell the body the preferred time to carry out necessary functions like cell repair too.
These rhythms run in the background and are mainly affected by light and darkness, and the most commonly observed circadian rhythm is the sleep-wake cycle. It is this cycle where diurnal and nocturnal animals are very different.
It is believed that at one point, that most if not all animals were diurnal, whereas the trait today, is mostly reserved for birds, mammals, insects and lizards. Some animals have evolved to take advantage of the conditions that night time provides, when it is cooler, more humid and with less active predators.
Diurnal animals on the other hand prefer the lighter, warmer conditions of the day, thriving on sunlight, and less active with a period of sleep during the night.
Nocturnal animals have a better sense of hearing, smell, and eyesight and a higher body temperature for roaming in the cooler dark hours. Diurnal species have lower body temp and smaller, more dynamic eyes for dealing with different levels of light.
What Are Crepuscular Animals?
Crepuscular animals, are those that are mainly active during the twilight periods of dusk and just before dawn. They can be active partially during the day or the night, but are most active during these hours. Most animals that have adapted this kind of schedule have done so as a means to avoid predators. Though some also do so as a means to catch their prey too.
Some species that live a crepuscular life include:
- Some Badgers
- Some Birds
- Some Fish – Particularly those near coral reefs or fly feeders.
- Most Deer
12 Diurnal Animals You Can See During The Day
Squirrels are rodents of the family Sciuridae, found commonly across Europe, Africa and the Americas. Some live on the ground, others in the trees and some known as flying squirrels are even built for gliding through the canopies. One feature that most ground and tree species share, is that they are diurnal by nature. There are a few species that are crepuscular, particularly as a measure or predator avoidance.
Flying squirrels differ from tree and ground squirrels in that they are typically nocturnal, which suits them in their humid, rain forest environments.
Domestic Cows or Cattle (Bos taurus) are a common livestock species, with populations on every continent except Antarctica. All cattle display typical diurnal behaviour, with grazing mainly taking place through daylight hours and most of their sleep occurring at night.
Cows sleep for about 4 hours per day, of which around a quarter is REM sleep laying down. Most sleep will be laying down at night, but they do take small dozes or slow-wave sleep standing up, several times in a day.
They are known to spend up to 8 hours a day chewing their cud which is regurgitated, partially digested food. They also drink the equivalent of a bath tub full of water a day!
There is an estimated 1.3 billion head of cattle and 920 breeds of cow in the world today. Cows are referred to as the ‘fosters mothers to the human race’ because they produce most of the milk that people drink.
Domestic Sheep (Ovis aries) are another common livestock species, with a population estimated to be close to one billion around the globe. They are a typical flock animal and live in a diurnal cycle. Physically they are better designed for living an active life through the day, while resting at night. Their vision is not well equipped to deal with darkness.
As a result, baby sheep may cry at night if they are scared or unsure where their mother is. A mother may also cry or ‘baaah’ loudly so that they and their offspring can keep track of where each other are. They don’t need to do this so much through the day, by at night when vision is reduced, they can need this reassurance. Particularly while lambs are young.
They may cry loudly if they feel or sense the presence of something unfamiliar, like a predator, to make sure that they are all close by and safe, while also alerting the flock.
The domestic dog (Canis familiaris) can take on many different guises across the many different dog breeds, but they are all of the same species of canid, and descended from wolves. They are the only member of the canidae family that live a diurnal life. Typically, canids are nocturnal, with wolves, foxes and coyotes all showing a usual preference or nocturnal and occasional crepuscular habits.
It is debated as to whether dogs are naturally diurnal, or if they life this lifestyle to fit around the activity and eating habits of humans. They do like their daytime naps after all!
The Great Apes
All of the members of the Hominidae family, known as the great apes or hominids (including us humans), are diurnal by nature. Most, such as the orangutan, gorilla and chimpanzee, sleep in a troop of up to several dozen members, either on land or in the trees, depending on the species.
They sleep at night, from dusk till dawn and often create a new bed every night if they are naturally nomadic. They will gather food, travel and rear their young through their more active daylight hours.
It’s not just the great apes, but actually most of their primate cousins that are diurnal in nature. The exception to this are most lemurs and lorises, and a few haplorhines, specifically tarsiers and owl monkeys which are mostly nocturnal.
Ducks, are of the family Anatidae, and while all ducks are in this family, not all Anatidae are ducks. There are many different species, but the family also include swans and geese, which collectively with ducks, come to over 170 different species. Together these animals are known as waterfowl.
Ducks, geese and swans all share many characteristics, but there are several clear physical differences too. Typically, ducks are diurnal, mostly sleeping at night and active through the day. They do tend to feed more often toward the start and end of the day, but are not crepuscular as they are still active through the day.
In urban and suburban habitats, like lidos, ponds and lakes, where humans visit often, ducks are very active during the day, often approaching visiting humans for a feed.
In some areas where the climate is extreme, there are some populations that have started to evolve into a more nocturnal lifestyle.
There are many birds that are crepuscular, and there are many that are diurnal. Eagles (birds of the family Accipitridae) are usually the latter. There are 68 species of Eagle, across several genera, and all except 14 of these species are found exclusively in Europe.
These large birds of prey are exceptional hunters with incredible sight, but this vision is suiting to hunting in daylight. They require good light to allow for their exceptional depth of field and long distance sight that they need to spot their prey from afar.
One particular species, the Golden Eagle (Aquila chrysaetos) has even been described in a Cornell University publication as “the pre-eminent diurnal predator of medium-sized birds and mammals in open country throughout the Northern Hemisphere.”
There are lots of breeds of chicken, both natural and hybrid around the world. They all however, come from the same species (Gallus gallus domesticus), which is a domesticated species of wildfowl. They are a common livestock species, kept for meat, eggs and as show birds. A common trait across the breeds, is that they live a diurnal lifestyle, and boy do some of them – particularly roosters – like to let you know this when they wake at the crack of dawn!
There are more chickens across the world than any other bird, due to their popularity as a livestock species. They may unsettle at night, and more around if disturbed by a potential threat or predator, but otherwise they tend to live a typical diurnal life.
Horses (Equus ferus caballus) are typically diurnal or crepuscular, though some believe that they don’t fit any of these cycles, including nocturnal. This is because horses only sleep very little over a 24 hour period, and are therefore active for some of the night as well as the day. They also take several naps during the day, standing up.
Horses sleep for around 3 hours per day, mostly in short standing naps. However, longer REM sleeps require laying down, and they do this at night. While they are not fully asleep during their day naps, and can easily be alerted to a threat, in REM sleep they need to lay down because your brain cant have that level of alertness in REM sleep. As night time is the only time where they are in this vulnerable state, and they are mostly active around human lifestyle in the day, they are typically diurnal.
Wild and feral horses also tend to be diurnal in nature.
The Meerkat (suricate Suricata suricatta) is also called a ‘Suricate’. It is a small member of the mongoose family whose range extends from South West Angola to South Africa.
Meerkats inhabit dry open areas, scrublands and savannas. They range across all parts of the Kalahari Desert in Botswana and South Africa. Usually living in places where there is plenty of sandy soil where they can dig elaborate underground burrows with many tunnels leading to numerous sleeping chambers.
Meerkats are diurnal animals and only forage during the day. The desert can be very cold at night, but these little animals are huddled in their burrow, warm and comfortable during the night time hours. Like all mongoose, they are agile little hunters. Their main omnivorous diet consists of insects and particularly beetles, spiders and millipedes. They sometimes feed up on small vertebrates, eggs and roots.
There are over 20,000 species of bees in the world in nine recognised families. There are still many unclassified species therefore the total population could be even higher. However these little pollinators are in danger, with numbers in great decline with pesticides and agricultural products, as well as the decline in ‘wild’ areas they need for food being major threats.
Though most bees are solitary and parasitic, there are around 400 species of Social Bees and these are grouped as the Bumble bees and Honey bees. They are adapted for feeding on nectar and pollen, nectar is used as an energy source and pollen used primarily for protein and other nutrients. Most pollen is used as food for larvae.
This pollen and nectar is collected during the sunny daylight hours, as most bees use the sun to navigate. They can see toward the ultraviolet end of the light spectrum and need the light from the sun to be able to do this. So they are active through the day and sleep at night. Honey bees for example, are known to sleep between 5 to 8 hours per day.
An elephant spends up to 16 hours a day eating, drinking, bathing, dusting, wallowing and playing. They spend on average, 3 – 5 hours resting, and the majority of sleep is obtained at night. In most populations, they are most active in the morning and evening than in the middle of the hot day, but they are not classically crepuscular as this activity is not before dawn or at dusk.
Most populations of elephant, both African elephants and Asian elephants, are diurnal, but some populations that live near human settlement have been observed taking on a more nocturnal lifestyle to avoid contact with people. In captivity, Elephants sleep longer than they do in the wild, and most of this is again through the night.