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Introduction
Definition of Predation
Predation can be generally defined as any interaction between two organisms that result in a flow of energy between them. The interaction can be positive or negative and includes both predator-prey, herbivore-plant, and parasite-host interactions. The process involved is, an organism have to spend some effort to locate a live prey, plant or a host and in addition spend another effort to mutilate or kill it and enhancing its survival. Many people tend to generalize predation to carnivorous only but predation is applicable to both animals and plants. It should be noted that the whole food chain is the cycle of predation that is from the source of life for all life which is the sun, Plants utilize the sun’s energy, animals eat plants and utilize the plants’ energy, and some animals eat other animals and utilize their energy.
Mathematical models and logic suggests that a coupled system of predator and prey should cycle that is predators increase when prey are abundant, prey are driven to low numbers by predation, the predators decline, and the prey recover, ad infinitum.
A sample of a common predator- Prey cycle
Source:http://en.wikibooks.org/wiki/Ecology/Predation_and_Herbivory#ref_sih198 5 (Cited on April 20, 2013)
This cycle forms a major driving force in evolution, as predator density increases, the number of prey consumed also increases. Thus preys adapt to avoid consumption by predators and live on and reproduce and they pass their survival skills to their young. The predator also adapt to become more efficient and the individual which cannot capture any prey die off and better adapted population lives on. This continues as an evolutionary predator-prey cycle.
Examples
Predators are animals like Lion, Cheetah, Hyena, Wild Dog, Tiger, Panther and others also can be plants like carnivorous plants such as Bladderwort, Sundew, Venus-fly trap and others. Preys can be animals such as Zebras, Wild beast, Antelope, Gazelle, Rabbit and others also.Preys can be plants such as Grasses, Plant leaves, Tree barks and others.
Forms or Types of Predation
There are four major forms of predation which are Carnivory, Herbivory, Parasitism and Mutualism. Each type of predation can be categorized based on whether or not it results in the death of the prey. Carnivory is lethal to the prey while herbivory and parasitism may or may not be lethal to the prey. Mutualism is not lethal to either predator or prey but, rather, benefits both organisms.
plants sometimes) and Hypercarnivores (are able to eat only meat duet to restricted digestive capabilities).
Carnivorous habits can also occur in plants and fungi that feed on insects or microscopic invertebrates. Such as Bladderwort and Sundew.
Herbivory is a type of predation in which animals/organisms consume autotrophs such as plants, algae, and photosynthesizing bacteria. Herbivory is a term commonly used to describe the consuming of plants by animals. Subcategories are Monophagous and Polyphagous. Monophagous eat one plant species and their survival depend on the survival of their promari source of food. Monophagous are also immune to plant’s defenses both mechanical and chemical. For example Monarch Butterfly that feeds on milkweed is immune to its toxic defenses.
Polyphagous feed on more than one type of plant species, most herbivores are in this kind
Sub groups in Polyphagous are Frugivors (eat primarily fruits), Folivors (eat leaves), Nectarivores (eat nectar) .The highest rate of herbivory occur in rainforests.
Parasitism occurs when one organism (a parasite) benefits at the expense of another (host). This type of interaction harms the host but it’s not like in carnivory, doesn’t always result in death of the host but the host can suffer infection sometimes. Normally the parasite is much smaller than the host and has a much faster reproductive rate. Example is the tapeworm in human digestive system.
Therefore the whole process of predations is a form of competition for survival. A predator tend to develop distinct adaptive feature which will help to capture a prey while preys too will develop distinct features for their own defense against predators as explain in the following title.
The distinctive features of predators
Predatory behaviour is that which results in in to the killing of another animals or prey for food. Some predators such as lions and tigers are large and ferocious, while others can be small in appearance such as lady bugs but however lady bugs can be seen ferocious to their prey which is tiny insect sometimes called aphids. There also some predators such as bears and crows eat a mixed of diet that includes a lot of plant materials as well as other animals. Other animals such as frog, lizards and most species of wild cats are more strictly carnivorous and their diet consists almost entirely of animals.
Predators usually possess senses to find their prey and special abilities to capture those prey, for example predatory birds they possess outstanding eye sight and often hearing as in the case of owls, for example the peregrine falcon is a magnificent bird hawk, it flies high up to the sky and in the air peregrine has exceedingly keen vision when a potential prey is sighted flying along below the peregrine closes its wings and dives or stoops to make its ambush most effective. And it is estimated that the peregrine falcon reaches a speed of 300km/hr almost 100m/sec. most preys are killed instantly by the sudden jolt of the peregrine falcon.
Other predators such as many species of mammals have very keen sense of smell which helps them locate preys, also many predators are fast and they use their speed so as to capture prey for example cheetahs predators of the African savannah are the world’s fastest runners also falcon, predators of other bird species are the world’s fastest fliers and barracudas are very fastest swimmers.
Predation can have direct effects on the population dynamics of both the predator and prey populations. For example, an increase in predator density increases the chances that a prey individual will be captured and thus, decreases the survival rate of the prey population. Lower prey survival leads to lower prey abundance and this can decrease the survival rate of the predator population. With few predators in the area, the prey population recovers and the process repeats itself. This is called a population cycle.
Predators may also have indirect effects on their prey. Prey species often change their behavior and adopt defensive tactics in the presence of a predator. For example, a prey individual may be less likely to risk feeding in areas that are not protected by cover even if those unprotected areas are rich in food. The predator is therefore having a negative effect on the prey without ever interacting with it. Other defensive tactics include the schooling or herding behavior of prey animals and the production of distasteful chemicals by plants to ward off herbivores. Both tactics have costs associated with them and thus, the predators are asserting indirect effects on their prey. These defensive tactics, in turn, can indirectly effect predators to evolve better capture techniques or resistance to plant chemicals.
Adaptation of prey and predators in the ecosystem
Adaptation is a body party, body covering, or behavior that enables an organism to survive in the environment. Adaptation can be in terms of behavioral or physical characteristics which fall into three main groups that is body parts, body covering and behaviors. Adaptation under the predator-prey relationship develop in which for the case of prey organisms aim at protecting themselves against predators while for predators aims at developing efficiency of obtaining their prey as a source of food for their survival.
selection that favors prey to adopt and avoid being found, caught and eaten while increases predator’s ability or efficiency of finding, capturing and eating its prey. Those two selective processes oppose each other because as the prey become more adopting at escaping from predators the predators in turn evolve efficient mechanism for capturing them.
Hence in the evolution of predator –prey relationship the predator evolves so as dissociate itself from the interaction while the predator continually maintains the relationship. Prey have equally developed escape mechanism such as posting of sentinels, predator alarm, background color matching and thorns which help prey organisms to escape before they come close with their predators, that is why most predators hunt by ambush.
Example in terms of body parts (physical adaptation) predators and prey organisms have evolved wings, sharp claws, sharp teeth and webbed feet in which for prey organism is for defense against predators while for predators is for obtaining their prey. Wings help the predators like black eagle or vampire bat to fly faster and catch their prey, while the same wings are used by smaller birds to run away from these predators.
Webbed feet help predators to swim faster and catch their prey organism while prey organism can use them to run from the predators, sharp claws help predators like lion to kill easily their prey as well as for tearing meat while prey use them to warn their predators to back off like what happens with bears that uses claws for defense, sharp teeth like for leopards help them to kill, chew and tear their prey while gorillas can use them to show power or fear to the leopard, that’s why predators should have more resources at their disposal and should normally be more fit than their prey and that is the reason why in many occasions predators choose the easiest prey available like young, sick, victims of accident, aging.
the environment and sometimes look like a tree bark or dead leaves, this can be evidenced for the case of chameleon for the purpose of defense, but the same can be used by predators so that they cannot be seen by their prey and catch them easily. Mimicry refers to the situation where by animal look similar to another animal that is dangerous to the predators in which the dangerous animal may have toxins making undesirable for the predators, animals that copy appearance are called mimics and those having toxins are called models.
Ecological role of predators
The health of natural systems relies on the presence of predators, where by the intact healthy ecosystem provides benefits or they are important to humans simply because they provide clean water, forest regeneration, seed dispersal as well as natural pest control, climate regulation, healthy native plant communities in uplands which in turn they contribute to soil fertility, stream bank stability, healthy fish and insect population.
When predators are removed from their food webs, the system becomes unbalanced and unhealthy, we simply cannot keep the current pace of species and habitat reduction or elimination if we want to maintain the ecological balance of nature. In fact the predators are the keystone meaning that their presence or absence has significant impact on the surrounding biological community.
Predator species greatly impact their environment simply because they survive by preying on other organisms whereby they send ripples throughout the food web, regulating the effects of other animals have on that ecosystem. This cause and effect process is called trophic cascade or the progression of direct {predation driven} and indirect {fear driven} effects that predators have across lower nutritional {trophic} levels in food chain.
cases, dominant predators even kill and eat their competitors (termedintraguild predation). These effects in turn impact the animals in the competitor’s food chain, which on the whole is an overlapping yet different set of animals than in the dominant predator’s food chain. One of the most frequently studied dynamics between predators involves wolves and coyotes. Wolves regulate the numbers, movement, and distribution of coyote populations because wolves are dominant. When coyote populations are held in check, animals lower down in the coyote’s food chain tend to have higher survival rates, as has been found with pronghorn and sage grouse. Thus, top predators support prey species at lower levels, again in turn triggering a whole host of other effects that contribute to the healthy functioning of a natural area.
In addition to regulating natural systems as described above, predators (especially large predators) serve as a measure of the health of communities around them. Top predators are associated with high biodiversity value because, they are sensitive to ecosystem dysfunctions, such as pollution, habitat fragmentation, and other human impacts that would affect many species. Also they select sites with productive habitat and vegetation complexity and lastly most have diets dominated by a few main prey species but a large number of secondary prey species. Communities with many prey species are richer and allow for prey-switching if necessary, which helps prey populations persist yet still allows for top-down regulation of the area by the predator.
Conclusively, Top predators typically need large areas for foraging and breeding and are thus considered umbrella species that is, if an area supports a large predator, it will encompass the requirements of less demanding species. Finally, because of their large area requirements, many predator species serve as a draw for tourists, encouraging the protection of wild spaces while generating income and employment.
Predators Management
Predators management refers to the process of balancing predation of organisms in the animal populations. The predation management is of significant importance if you take into account the threats of unbalanced relationship to the surrounding social communities near by the parks, game reserve or conservation area particularly farmers, livestock owners and other villagers.
Most of the government authorities tend to manage predators particularly large predators like lions, leopards, hyenas, cheetahs, crocodiles and etc., below their biological carrying capacity because it’s better for predators to be minimal than preys instead of predators to be maximum than preys. Potential threats to predators includes loss of habitat and land use change, retaliatory killing and unregulated tourism may pose important threat to predator conservation management.
Control alternatives for managing predation on wildlife
It’s important to develop a control strategy that will address the followings;
Species to be controlled
The scale of control
The season and length of control
Lethal and non-lethal methods to be used
The cost benefit ratio
There are two control alternatives for managing predation in wildlife;. Lethal methods
Under lethal methods includes; Foothold traps (wide range of applications), Neck snares (easily used but not selective), Calling/Shooting (highly selective but time consuming), Aerial gunning (highly effective for some species and situations but can be expensive).
Foothold traps; Is versatile and available in sizes and shapes appropriate for coyotes, lions, wild dogs, etc. The size or number of the traps should correspond with the size of the predator. Stakes or drags must be attached to the trap to anchor the trapped predator. When doing traps the trapper should wear the gloves when handling clean traps and when setting traps because many predators (especially canines) have a keen sense of smell and can detect human’s odors on buried traps. Pick trap sites wisely to avoid catching non target animals. Good places where predators travel regularly including roads and trail intersections, water holes, fence corners, ‘crawls’ under fences, pasture gates, stream crossing and fresh animal carcasses.
Snares; Are rather simple mechanical devices. They are economical, effective and do not require as much skills or training to use correctly. Any animal travelling through a snare is likely to be caught so they must be used with extreme care. When tripped the snare start to close around the head or body and the locking device keep the loop tight. Snares are used where there’s net wire fencing. They are setting under the fence or between wires where animals pass through.
calling in the area, improper calling, missed shots, or carelessness on the part of the caller or hunter.
Aerial gunning; Is the use of the aircraft (fixed wing or helicopters) to take target animals that are causing problems or to quickly reduce the number of predators. Aerial gunning is most effective in area with open, flat terrain and little brush. A fixed wing air craft is most often used over flat or gently rolling terrain with little brush cover, where as a helicopter can be used for all types of terrain and cover. A12 semiautomatic short gun is the weapon of choice for aerial hunting from either types of aircraft.
In non-lethal methods include; Habitat enhancement (usually first line of defense, examples are improving nest cover), Fencing (most effective for free ranging animals), Cage traps ‘live traps’ (effective for many species but not coyotes), Conditioned Taste Aversion, Immuno-contraception (experimental).
Habitat enhancement is the most natural way to minimize predation. This involves manipulating the habitat to favor prey species. Generally the more cover available to the prey species the letter its odds of survival. Habitat enhancement ranges from strategic brush removal to subtle changes in grazing.
Conditioned taste aversion; Is the process by which animals come to associate the taste of a food with an acute gastric illness that occurs soon after consumption. It is largely experimental and it’s not likely to become a tool for controlling predation on game animals, but it may someday useful in controlling nest predation, especially when predators are small and also when occupy small overlapping ranges.
References
1. L.J Milne, The Arena of Life, 1972
2. L. Martin and Diamond M., Ecology and Evolution of communities, 1975 The Belknap Press of Harvard university press.
3. http://en.wikibooks.org/wiki/Ecology/Predation_and_Herbivory#endnote_Preston2009 (cited on April 19, 2013)
4. Michael Grahm, Natural Ecology, 1973
5. Pianka R. Eric, Evolutionary Ecology 1978, Harper and Row publishers. 6. http://www.globalchange.umich.edu/globalchange1/current/lectures/predation/
predation.html ( April 20/2013)
7. Bolen, Eric G. and Robinson, William L. Wildlife ecology and management, 5th edition