Predation
n., plural: predations
[prɪˈdeɪʃən]
Definition: The symbiotic relationship between a predator and its prey
Table of Contents
In ecology, predation is a mechanism of population control. Thus, when the number of predators is scarce the number of prey should rise. When this happens the predators would be able to reproduce more and possibly change their hunting habits. As the number of predators rises, the number of prey declines. This results in food scarcity for predators that can eventually lead to the death of many predators.
Predation Definition
What does predation mean? What is predation? We can define predation as the ecological process in which an animal (or an organism) kills and feeds on another animal (or an organism). The animal that kills another animal to feed on is called a “predator“. The one that is killed to be eaten is known as prey. The best example of predation is in carnivorous interaction. A carnivore is an animal that gets its energy only by eating meat or animal tissues. Thus, in carnivorous interaction, one animal feeds on another. Examples are wolves hunting a deer or a moose, an owl hunting the mice, and the lion hunting various animals.
A predation is a form of a symbiotic relationship between two organisms of unlike species in which one of them acts as a predator that captures and feeds on the other organism that serves as the prey.
Predation in Ecology
An ecological science definition of predation is that it is an ecological process where energy is transferred from one living being to another based on the nature and behavior of the predator.
How does predation work? In another context, predation means the reliance of one organism on another by consuming it as its food. Using predation, the organisms get the energy to increase their life and reproduce to sustain the existence of their species.
Animals that are an easy target include the young and the old. The young are without sufficient experience or knowledge yet are highly vulnerable to predator attacks. The old animals, in turn, are not as vigorous as they have been during their prime and so would not be able to defend themselves fully as they have been.
Often, the predator is larger than its prey. The larger animal consumes the smaller ones as their food as mostly seen in seas (where large fishes are preying on small fishes or insects). However, there are instances as well when small animals are preying on large ones and this is not an easy task. A group hunting technique referred to as group predation makes predation of larger animals possible. Examples of group predation are a group of lions, wolves, or hyenas that can kill much larger animals. Lions are seen to kill big buffalos that are sometimes five times the weight of individuals. Group predation is commonly seen in ants as well.
Predation is not only seen in animals but also in other living beings, such as carnivorous plants. Examples include pitcher plants and Venus flytrap that prey on insects and flies. As you will see, there are three stages of venus flytrap predation. Firstly, the trap (which is a pair of modified leaves) is open waiting for prey to enter. When a prey (e.g. fly) gets into the plant’s trap, it generates stimuli that signal the plant to close a bit. By the next stimulation, the plant totally shuts its trap sealing the prey inside. The trap then serves as a digestive organ, secreting enzymes that digest the prey.
Read: Understanding the Venus Flytrap.
As for the pitcher, there is a pool of water containing digestive enzymes that digest the insect into absorbable food. The digestive enzymes dissolve the insect and the plant gets the nutrients.
Predator Definition
What is a predator? We can define predators as the species that use other species as their food. There are animal predators such as cats, wolves, lions, etc., and plant predators such as pitcher-plant. Predator and prey have an ecological relationship that keeps the population of both in control. When a predatory animal starts consuming its prey, the population of prey will decrease while that of the predator will increase. After some time there will be less prey while more predators. The lesser food will result in a decrease in the population of predators and as result, the population of prey will start increasing. This predator-prey relationship is naturally present on earth for millions of years. Further details about this have been discussed in the Population dynamics of predator and prey.
There are several types of predators depending on their size, biology, and nature of predation. However, predators are largely considered carnivores or meat-eaters. Other references though include herbivores and parasites as predators based on the definition of predation that incorporates the ecological flow of energy between organisms. [Ref.: Sih, et al.] However, we will focus more on the carnivores as predators in the next sections.
Predators’ hunting techniques
Predators search, assess, pursue, and then kill the prey. These actions of a predator are known as the foraging cycle. The search involves finding the right kind of prey. For example, a wolf will not search for a very oversized animal such as buffalo, rather its preference will be a smaller animal such as moose. Similarly, an insect named “mantid” would prefer to catch small prey. This is because it uses its forelegs to capture and eat the prey and its forelegs are not very large or strong. Thus there is a positive correlation between the size of prey and types of predators. Once the prey is searched, the predator can assess either wait for it or pursue it. It also depends on the nature of the predator and the density of prey. Of course, a plant will not pursue a fly. However, some predators such as tigers and lions can first wait and then pursue their prey once it’s in their range.
Predators use different methods of hunting. One of the methods is to capture the prey. There are several capturing techniques that different predators use. The techniques can involve ambush (lions, panthers, and other carnivorous animals use this method), ballistic interception (such as a frog catches a fly passing nearby with a sudden jerk of its sticky tongue), and pursuit (chasing).
- In the ambush technique, the animal observes the environment and waits for prey silently in a more hidden area. The purpose of an ambush is to launch a surprise attack on the prey thus leaving limited chances of its survival. Ambush technique is used by both vertebrate predators (frogs, angel sharks, etc.) and non-vertebrate predators (mantis shrimps, trapdoor spiders, etc.)
- Ballistic interception is the technique in which the predator first observes the movement of its prey, predicts its motion, and then intercepts by attacking the animal with the predator’s natural tool. Examples of predators that use ballistic attacks are vertebrates such as chameleons and non-vertebrate such as dragonflies.
- Pursuit is another technique where the predators chase the fleeing prey. Chasing prey involves the agility and skill of the predator. If prey moves in a single direction, the capture depends upon the speed of the predator. The one with higher speed will win. But in most cases, the prey seldom moves in a straight line (for example chasing a deer). In such a situation the predator must react in a timely manner by calculating and following the intercept path.
A predator blindly following the haphazardly moving prey will lose it eventually. The best technique the predator uses is parallel navigation where every move of the prey brings it closer to the predator. Some predators camouflage before the actual pursuit. This helps them to be as close to the prey as possible. Thus minimum pursuit may be required. Contrary to high-speed pursuit done by lions, tigers, cats, etc., there is another kind of pursuit that requires extreme endurance and persistence. In such kinds of pursuits, the predator chases the prey for long distances at slow speed. The chase may linger for hours. The African dog is the best example of such a predator. It follows its prey for many miles at a relatively slow speed. Hunting in a group is known as group pursuit predators. Lions and wolves show such behavior. Such pursuit can help capture and handle a larger prey.
Predators’ prey handling
After capturing the prey, the predator has to handle its prey for eating. This is the fight of predator versus prey where the predator wants to eat while the prey wants to escape. The predators can kill the prey or sometimes eat alive. There are prey animals that are very dangerous to handle due to the presence of their innate defense mechanisms, such as sharp claws, teeth, poisonous spines, etc. For example, catfish can lock its spine in an erect position suddenly. If it is in the mouth of a predator, it can severely damage the predator’s mouth. The predators avoid this danger by tearing up the prey before eating.
Adaptations
The principle of evolution is based on the survival of the fittest. Predation has an impact on the fitness of both the prey and the predators. In order to survive and reproduce for the continuation of their species, both predators and prey need to acquire adaptations to enable them to eat, and at the same time, avoid being eaten. The survival mechanism is passed to offspring in genetically determined traits. Natural selection is the basis of the selection of improved predation for predators and avoiding predation by prey.
Predators adaptations
The adaptation in predators helps them capture their prey easily. Predators usually exhibit traits such as sharp claws, teeth, body structure, and venom that increase the ability to capture the prey. Apart from these traits, a predator also needs very sharp sensory organs to locate and observe the prey. The adaptation resulted in an acute sense of smell, hearing, and viewing. For example, the raptor (birds of prey) can spot their prey from a mile away. Similarly, the owl catches the mice by locating the sound. Pit viper snakes can sense heat from the prey which helps it chase. The bat and dolphins use sound waves to navigate and locate potential prey.
Prey adaptations
Prey adaptation in nature helps the prey to avoid detection or capture. Some species use color and camouflage methods to avoid detection. These include leaf insects, small lizards, moths, frogs, and other herbivorous animals. The prey freezes at its position once it detects the predator. The lack of movement makes it difficult for a predator to search visually. There are situations when predators come too close, in such conditions the prey will suddenly flee. The predator may start the chase. Prey will avoid capture by moving away from the predator or sitting on another area where it becomes invisible. However, such tactics don’t work every time. Some prey animals confuse or surprise the predators to get some extra time to flee. Lizards drop their tails to confuse the predator. Predator catches the tail while the lizard flees away. Similarly, moths can flash brightly colored hindwings in front of predators to confuse and threaten them. The brightly colored species are considered toxic among predators. Not all species exhibiting vivid colors are toxic but they mimic to avoid being eaten. Examples of such mimicry include the swallowtail butterfly which mimics the distasteful species of Amauris and Danaeus.
Chemical adaptations
Both predators and prey have shown chemical adaptation. The predators use chemicals to attack the prey while prey uses the chemicals to counter-attack or avoid being eaten. Prey uses venom, poisons, and toxins as their defense. The venomous snakes use their toxic venom to take down their prey. These snakes can kill a larger animal using their venom by injecting it into the bloodstream of its prey while biting. In a few moments, the animal will die. The snakes don’t chew, but swallow their prayers. The larger snakes have been seen to eat whole goats or dear.
Some prey have acquired mechanisms that make them less palatable to their predators. For example, caterpillars and monarch butterflies can eat milkweed, which is a poisonous plant for most omnivores and herbivores. By eating this plant, the butterflies also get the toxins. That makes them unappetizing to the predators.
Population Dynamics of Predators and Prey
There is a natural balance between the population of predators and the prey. If there are no predators, the population of the prey can increase exponentially. It can increase the carrying capacity of the environment. Predators help to control the prey population by consuming it as their food. When the population of prey increases, the number of predators also increases as there is more food available. But an increase in the predator population could lead to a decline in the prey population. This, in turn, has its effect on the predator population, which also decreases because of the scarcity of food. Thus there are cyclic fluctuations in the population of prey and predators.
The population dynamics of snowshoe hare and lynx were studied by the researchers. They found that over the period of time the hare population was fluctuating and with these fluctuations, the population of lynx was also changing in synchrony.
Apart from predator and prey, some other factors also play their role in population dynamics. These factors are environmental and human interference. If there are multiple predators for the same prey, the population of prey will abruptly fall while the predators either need to find a new place or new prey to feed themselves. Thus, the food web (food cycle) in such conditions becomes very complex to study.
Researchers have found that in northern temperate regions the food web is simple and a population cycle exists. Researchers have also made computer mathematical models to simulate the population dynamics of the species. This will help the scientists to study the population cycle and thus help avoid the extinction of species.
Energy Flow and Trophic Levels
The trophic level of an organism indicates the position it occupies in the food cycle. The food cycle or food web is the system comprising producers, consumers, and decomposers. Producers include the autotrophs and they produce their food from soil, water, air, and light. They do not eat other animals as prey. Consumers are also known as heterotrophs. They cannot produce their food and need to eat other organisms which can be animals, plants, insects, etc. Lastly, decomposers are the organisms that decompose food or animal waste. Bacteria are natural decomposers.
Based on these three identities, the trophic levels are defined as follows:
LEVEL-01: Producers (plants and algae make their own food)
LEVEL-02: Herbivores (The animals that eat the plant to live)
LEVEL-03: Carnivores (Eat herbivores)
LEVEL-04: Carnivores (Eat other carnivores- prey on predators)
Predation Examples
There are several examples of predation. Humans are one of the biggest examples of predation. Unlike plants, humans and other mammals cannot produce their own food. Therefore they need to eat other animals or plants to survive.
Carnivorous predation
Carnivorous predation is one of the most common kinds of predation. The best example of carnivorous predation is lion hunting zebras, rhinos, buffalo, and wolves. Wolves hunt large herbivores such as deer, sheep, and elk. Wolves have strong jaws, powerful bodies, and an acute sensory system that helps them find, capture, and kill their prey.
Owls seem like innocent birds, however, they are predators for mice. Owls also eat other things such as frogs, snakes, lizards, rabbits, and squirrels. An owl is also an example of carnivorous predation.
Apart from owls, many other birds are carnivorous predators, for example, eagles, hawks, falcons, vultures, etc. All of these birds eat other species such as mice, chickens, snakes, fishes, etc.
Some plants have also shown carnivorous behavior such as pitcher plant capturing and digesting the flies. Similarly, venus flytraps also work in the same manner. These plants are usually found in soils that are not very rich in nutrients.
Herbivorous predation
In herbivorous predation, the predator eats plants, grass, leaves, algae, etc. Herbivores are adapted to their mode of feeding for example rabbit is a herbivore and will eat certain types of grass and leaves. It is unable to eat strong stems and plants. Elephants are also herbivores and can eat tough plants and stems because of their flat teeth which grind easily. Examples of other herbivore predation are cow eating grass, goat and sheep eating plant leaves, monkeys eating fruits, gorillas eating soft stems and leaves of the plant. Apart from animals, some insects have also shown herbivorous predation behavior such as grasshoppers eating plant leaves, stems, and flowers.
Parasitic predation
An example of parasitic predation where parasites don’t kill the animal are mites, ticks, and lice. The host of the parasite is usually a human, animal, or plant. Parasitic fungi are also examples of parasitic predation because they rely on their host of food.
Try to answer the quiz below to check what you have learned so far about predation.
References
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- Sih, A., Crowley, P., McPeek, M., Petranka, J., and Strohmeier, K. 2019. Predation, Competition, and Prey Communities: A Review of Field Experiments. Annual Reviews. https://www.annualreviews.org/doi/abs/10.1146/annurev.es.16.110185.001413
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