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Author: Leslie Tsen (B.S.) Ecology, Evolution & Natural Resources. Wildlife Conservation
In chronobiology, scientists, researchers and investigators alike study the cyclic events in living organisms by examining how they physiologically, biologically, and behaviorally respond to the day-and-night cycle. Since the term “living organisms” encompasses an astronomical number of living species which also happens to include single cell amoeba, plants, and even mushrooms, we will be narrowing down our scope of discussion to the activity cycle of just mammals.
The understanding of these activity cycles as well as species natural history saves researchers a lot of time by improving their likelihood to encounter their studied subjects in the wild. It also guides conservationists, zoological park exhibitionists as well as animal caretakers (which also include pet owner) to better design a living habitat that best fits with the species’ natural behavior. For example, one would want to avoid housing a shy, nocturnal species in a relatively open enclosure with bright light beaming down all the time. If a particular species is known to feed exclusively during the day when its food items are the most visible, then it will be highly inefficient to carry out feeding under poor lighting condition.
The activity cycles of small mammals are typically divided into three categories - diurnality, nocturnality, and crepuscularity, whereas large mammals tend to exhibit a fourth activity cycle type known as cathemerality. In this article, we will briefly introduce the basic concepts of each activity cycle, discuss their respective pros and cons, and then relate them back to how you as a pet owner can utilize these valuable information to improve the well-being of your animals.
Diurnality refers to the habit of being active during the day. Species that exhibit this behavioral pattern carry out most of their activities such as foraging, marking and protecting territory, hunting as well as seeking out for mate throughout the day while spending their night sleeping or resting. One of the key benefits of being a diurnal species is that one gets to have a clearer and better view of its surrounding. This allows oneself to better identify food items when foraging, detect threats from predators and the environment, as well as to recognize potential mate of the same species from afar.
Living a diurnal life can sometimes be a double-edge sword. In the wild, many small mammals especially rodents are found at the bottom of the food chain serving as preys. Diurnal predators such as raptors (ex: eagle, hawk, falcon) and several species of mustelids (ex: weasel, ferret) have thus developed incredible eyesight that is capable of tracking down the subtlest movement made by their rodent preys even from several kilometers away.
As a general guideline, diurnal small mammals tend to dislike wandering off in exposed, open areas which greatly increases the risk of them being spotted by a predator. To better improve the mental health of your pet, shelters and substrates for hiding are highly recommended. We would also like to urge fellow pet keepers to not stand tall around small mammals before picking them up, as the overcasting shadow will likely terrorize your pets into thinking that they are about to get pounced by a predator. Instead, kneel down and calm your pet with a gentle voice before scooping them up at ground level.
Nocturnality refers to the habit of being active at night. Nocturnal mammals tend to have large eyes (to house larger-than-usual pupils) to compensate for the low light condition at night. In many nocturnal species, a unique, mirror-like structure called tapetum lucidum can be found in these large eyes to help reflect light enter through the retina. This reflection amplifies the amount of light entering the photoreceptors, thus allowing nocturnal animals to see clearly even under very dim light. If you beam a light towards the eyes of nocturnal mammals such as sugar glider and cat, you will notice a cool glowing effect coming out from the tapetum’s reflection.
Nocturnality does come with several benefits. By being active only after the sun is down, the risk of overheating will be greatly reduced. For instance, kangaroo rats (a less common pet) living in the harsh deserts of North America are able to conserve more water and avoid heat stress by hiding away in their relatively cool underground burrows throughout the day. Only exiting their burrows to forage for seeds at night, they are also able to dodge predators that rely heavily on their day vision to hunt.
Furthermore, insectivorous small mammals will likely benefit from the swarming behavior of insects species that are only active at night. A few examples of small mammal that have benefited tremendously by adapting nocturnality will be the vast species of insectivorous microbats, in which a single individual is capable of consuming up to 3000 mosquitoes in a single, mosquito-swarming night. If food sources are scarce at a particular time period yet abundant in another’s, it will be ideal to adjust your feeding session to the time when you are most likely to get fed.
Although being a night active species does grant nocturnal preys protections from diurnal predators under the cover of darkness, hunters such as owls, ocelots, and servals have adapted and coevolved with their natural preys to be able to hunt under low light condition. It is difficult to conclude whether nocturnal predators or preys utilize darkness better, as different species of preys and predators have evolved different strategies to counter-adapt against one another. For instance, a recent study has shown that nocturnal species that rely on vision as their primary sensory system (such as primates, carnivorous & herbivorous marsupials) are more active on moon-lit nights while those (rodents, rabbits, bats, badger & lion) that rely more on other sensory systems are less active.
To better observe the common behavior of your nocturnal pets as well as to interact with them during day time, you can reverse the lighting condition in your animal’s enclosure as seen in the nocturnal house of many zoos. Light is usually lit at night to stimulate day time while it is switched off in the morning to stimulate night time thus encouraging activity. A dim, artificial light stimulating moonlight can also be provided for nocturnal marsupials such as sugar glider to further increase their activity level.
Crepuscularity refers to the habit of being active during the dawn and the dusk. Species that have adapted to a crepuscular lifestyle tend to carry out most of their activities (foraging, feeding, hoarding) within the several short hour periods in a day when the sun is about to rise or set. There are some clear disadvantages of being a strict crepuscular species. For example, strictly crepuscular animals will only get very limited daily time period to carry out their activities. This translates to having less time to forage for foods and being less likely to encounter a potential mate. Therefore, many small mammals such as rodents and lagomorphs (rabbits, hares, pikas) exhibit a mixture of diurnal-crepuscular or nocturnal-crepuscular behavior depending on the season, temperature, weather, predatory factor, and food availability.
Crepuscular species will likely have an edge over predators that are most efficient at hunting during the day or the night when the light intensity is at its maximum or minimum. The transition phases (dawn and dusk) provide a few hours of precious twilight for crepuscular mammals to carry out their activities - just bright enough to identify foods, yet dark enough to mask them under the shadow. Crepuscularity may also help small mammals to combat both hyperthermia (too hot) and hypothermia (too cold) in harsh environment such as deserts where day and night temperature fluctuate greatly. In places where competitions for resources are fierce among strictly diurnal or nocturnal species, adopting a semi-crepuscular living habit might actually improves the winning chances of those who adapted.
Once domesticated, animals that were once crepuscular in the wild can often adapt to their owners’ schedule. However, we wanted to urge fellow pet keepers to take the adaptation process slowly and gradually as individuals are different. Never force your pets to adapt via starvation or physical abuse (this includes poking your rabbits when they are trying to rest) as these are not only cruel but could be potentially traumatizing for their physical and mental health. Instead, use positive encouragements such as offering them treats and caress them via massages when they stay up at your desired time period. You should also always be ready to accept the fact that some pets are just never meant to fit into your time schedule.
Cathemerality refers to the type of activity habit that is sporadically spread in a 24-hours period with no distinguishable peak activity level at any specific time period. It can also refer to the habit type of being active at both day and night. One of the major advantages of being cathemeral is that individuals are able to exploit resources at any given time.
Cathemerality is usually more common in larger mammals or in species that lack or have fewer natural predators. If an organism is lacking any natural predators (such as the adults of elephant, hippopotamus, and rhinoceros), then predatory stress will no longer be a limiting factor constraining individual’s activity patterns. Other factors such as temperature, humidity, intrinsic physiology, conspecific interaction, and resources availability will then play a larger role at governing the activity habit of such individual. Such is also the case for several lemur species that are living on the island of Madagascar. With only one rare predator (fossa) that is strong enough to bring them down, the common brown lemurs (Eulemur fulvus fulvus), the mongoose lemurs (Eulemur mongoz), and several others are known to be active throughout the day and night.
Domesticated pets such as dogs and cats are often time cathemeral due to the adaptation to their owners’ schedule. They can be active throughout the day and the night as long as they are properly fed and nourished. Hamsters, rabbits, guinea pigs, and mice will ocassionally stay up for a late night or early morning snack but are in general less cathemeral. Once again, we wanted to urge fellow pet owners to respect their pet's needs by accepting the fact that no two individuals are alike and that all animals should have their well-being lookafter in an individual-by-individual basis, irregardless of how seemingly "insignificant" these needs are to our human eyes.
Disclaimer: This article contains materials referred from published scientific journals and is strictly meant for educational purposes only. It must NOT be substituted for any forms of medical care, treatment, and consultation from veterinarians, aquatic experts or other licensed professionals. NO compensation shall be reimbursed by Harvest Fish & Pet for the direct or indirect loss, damage, injury, or death of both living (user included) and non-living beings caused by the application of information from this article either in full or in part.