A mesopredator is a mid-ranking predator in the middle of a trophic level, which typically preys on smaller animals. Mesopredators often vary in ecosystems depending on the food web. It is also important to note that there is no specific size or weight restrictions to qualify as a mesopredator, as it depends on how large the apex predator is, and what the mesopredator's prey is. When new species are introduced into an ecosystem, the role of mesopredator often changes; the same happens if a species is removed.
When populations of apex predators decrease, populations of mesopredators often increase. This is the mesopredator release effect. "Mesopredator outbreaks often lead to declining prey populations, sometimes destabilizing communities and driving local extinctions". When apex predators are removed from the ecosystem, this gives the mesopredators less competition and conflict. They are able to catch more prey and have lower mortality rates. Often, mesopredators can take over the role of apex predators. This happens when new species are introduced into an ecosystem or when species leave or are killed off. When this happens, and the new apex predator or former mesopredator, becomes the new species on top of the food chain, it is important to remember that they are not ecologically identical to the former apex predator, and is likely a smaller species, which will have different effects on the structure and stability of the ecosystem. The mesopredators that become the new apex predators are the species that benefit from this mesopredator release. Apex predators reduce mesopredator populations, and change mesopredator behaviors and habitat choices, by preying on and intimidating mesopredators. This can occur in any ecosystem with any type of relationship between predator and prey. However, in the case of the relationship between apex predator and mesopredator, it could mean that the apex predator causes the mesopredator to leave the ecosystem, again, creating room for a new species to become mesopredator.
Mesopredator outbreaks are increasing in fragmented habitats. A main cause is the disappearance of apex species within the habitat. Apex species are usually larger animals who require a bigger area and will often leave if the habitat is lost. When the apex predator leaves the ecosystem, a former mesopredator will become the new apex predator. Likewise, the apex predators, being larger animals, will often have more encounters with humans, leaving them more susceptible to harmful conflicts. These harmful conflicts can either cause the apex predator to leave the ecosystem in fear of danger, or if the situation is extreme enough, the humans will have killed off the apex predator. Another reason why mesopredator outbreaks are becoming more popular is because of certain resources being added in fragmented areas. Resources such as pet food, trash, crop, and crop pests. These resources often appear when development is occurring on land near the ecosystem. This scenario is the most ideal for mesopredator outbreaks to occur.
An apex predator, also known as an alpha predator or top predator, is a predator at the top of a food chain, with no natural predators.Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the highest trophic levels. Food chains are often far shorter on land, usually limited to being secondary consumers – for example, wolves prey mostly upon large herbivores (primary consumers), which eat plants (primary producers). The apex predator concept is applied in wildlife management, conservation and ecotourism.
Apex predators have a long evolutionary history, dating at least to the Cambrian period when animals such as Anomalocaris dominated the seas.
Humans have for many centuries interacted with apex predators including the wolf, birds of prey and cormorants to hunt game animals, birds, and fish respectively. More recently, humans have started interacting with apex predators in new ways. These include interactions via ecotourism, such as with the tiger shark, and through rewilding efforts, such as the proposed reintroduction of the lynx.Cascade effect (ecology)
An ecological cascade effect is a series of secondary extinctions that is triggered by the primary extinction of a key species in an ecosystem. Secondary extinctions are likely to occur when the threatened species are: dependent on a few specific food sources, mutualistic (dependent on the key species in some way), or forced to coexist with an invasive species that is introduced to the ecosystem. Species introductions to a foreign ecosystem can often devastate entire communities, and even entire ecosystems. These exotic species monopolize the ecosystem's resources, and since they have no natural predators to decrease their growth, they are able to increase indefinitely. Olsen et al. showed that exotic species have caused lake and estuary ecosystems to go through cascade effects due to loss of algae, crayfish, mollusks, fish, amphibians, and birds. However, the principal cause of cascade effects is the loss of top predators as the key species. As a result of this loss, a dramatic increase (ecological release) of prey species occurs. The prey is then able to overexploit its own food resources, until the population numbers decrease in abundance, which can lead to extinction. When the prey's food resources disappear, they starve and may go extinct as well. If the prey species is herbivorous, then their initial release and exploitation of the plants may result in a loss of plant biodiversity in the area. If other organisms in the ecosystem also depend upon these plants as food resources, then these species may go extinct as well. An example of the cascade effect caused by the loss of a top predator is apparent in tropical forests. When hunters cause local extinctions of top predators, the predators' prey's population numbers increase, causing an overexploitation of a food resource and a cascade effect of species loss. Recent studies have been performed on approaches to mitigate extinction cascades in food-web networks.Cat
The cat (Felis catus) is a small carnivorous mammal. It is the only domesticated species in the family Felidae and often referred to as the domestic cat to distinguish it from wild members of the family. The cat is either a house cat or farm cat which are pets, or a feral cat, freely ranging and avoiding human contact.
A house cat is valued by humans for companionship and for its ability to hunt rodents. About 60 cat breeds are recognized by various cat registries.Cats are similar in anatomy to the other felid species, with a strong flexible body, quick reflexes, sharp teeth and retractable claws adapted to killing small prey. They are predators who are most active at dawn and dusk (crepuscular). Cats can hear sounds too faint or too high in frequency for human ears, such as those made by mice and other small animals. Compared to humans, they see better in the dark (they see in near total darkness) and have a better sense of smell, but poorer color vision. Cats, despite being solitary hunters, are a social species. Cat communication includes the use of vocalizations including mewing, purring, trilling, hissing, growling and grunting as well as cat-specific body language. Cats also communicate by secreting and perceiving pheromones.Female domestic cats can have kittens from spring to late autumn, with litter sizes ranging from two to five kittens.
Domestic cats can be bred and shown as registered pedigreed cats, a hobby known as cat fancy. Failure to control the breeding of pet cats by spaying and neutering, as well as abandonment of pets, has resulted in large numbers of feral cats worldwide, contributing to the extinction of entire bird species, and evoking population control.It was long thought that cat domestication was initiated in Egypt, because cats in ancient Egypt were venerated since around 3100 BC.
However, the earliest indication for the taming of an African wildcat (F. lybica) was found in Cyprus, where a cat skeleton was excavated close by a human Neolithic grave dating to around 7500 BC. African wildcats were probably first domesticated in the Near East. The leopard cat (Prionailurus bengalensis) was tamed independently in China around 5500 BC, though this line of partially domesticated cats leaves no trace in the domestic cat populations of today.As of 2017, the domestic cat was the second-most popular pet in the U.S. by number of pets owned, after freshwater fish, with 95 million cats owned. As of 2017, it was ranked the third-most popular pet in the UK, after fish and dogs, with around 8 million being owned. The number of cats in the United Kingdom has nearly doubled since 1965, when the cat population was 4.1 million.Dusky catshark
The dusky catshark (Bythaelurus canescens) is a catshark of the family Scyliorhinidae that is endemic to the southeast Pacific Ocean, off the coasts of Peru and Chile. It grows to a maximum length of 70 cm, and is oviparous like many other chondrichthyans in the Indo-Pacific.Energy flow (ecology)
In ecology, energy flow, also called the calorific flow, refers to the flow of energy through a food chain, and is the focus of study in ecological energetics. In an ecosystem, ecologists seek to quantify the relative importance of different component species and feeding relationships.
A general energy flow scenario follows:
Solar energy is fixed by the photoautotrophs, called primary producers, like green plants. Primary consumers absorb most of the stored energy in the plant through digestion, and transform it into the form of energy they need, such as adenosine triphosphate (ATP), through respiration. A part of the energy received by primary consumers, herbivores, is converted to body heat (an effect of respiration), which is radiated away and lost from the system. The loss of energy through body heat is far greater in warm-blooded animals, which must eat much more frequently than those that are cold-blooded. Energy loss also occurs in the expulsion of undigested food (egesta) by excretion or regurgitation.
Secondary consumers, carnivores, then consume the primary consumers, although omnivores also consume primary producers. Energy that had been used by the primary consumers for growth and storage is thus absorbed into the secondary consumers through the process of digestion. As with primary consumers, secondary consumers convert this energy into a more suitable form (ATP) during respiration. Again, some energy is lost from the system, since energy which the primary consumers had used for respiration and regulation of body temperature cannot be utilized by the secondary consumers.
Tertiary consumers, which may or may not be apex predators, then consume the secondary consumers, with some energy passed on and some lost, as with the lower levels of the food chain.
A final link in the food chain are decomposers which break down the organic matter of the tertiary consumers (or whichever consumer is at the top of the chain) and release nutrients into the soil. They also break down plants, herbivores and carnivores that were not eaten by organisms higher on the food chain, as well as the undigested food that is excreted by herbivores and carnivores. Saprotrophic bacteria and fungi are decomposers, and play a pivotal role in the nitrogen and carbon cycles.The energy is passed on from trophic level to trophic level and each time about 90% of the energy is lost, with some being lost as heat into the environment (an effect of respiration) and some being lost as incompletely digested food (egesta). Therefore, primary consumers get about 10% of the energy produced by autotrophs, while secondary consumers get 1% and tertiary consumers get 0.1%. This means the top consumer of a food chain receives the least energy, as a lot of the food chain's energy has been lost between trophic levels. This loss of energy at each level limits typical food chains to only four to six links.Feral cat
A feral cat is an un-owned domestic cat (Felis catus) that lives outdoors and avoids human contact: it does not allow itself to be handled or touched, and usually remains hidden from humans. Feral cats may breed over dozens of generations and become an aggressive apex predator in urban, savannah and bushland environments. Some feral cats may become more comfortable with people who regularly feed them, but even with long-term attempts at socialization they usually remain aloof and are most active after dusk.
Feral cats are devastating to wildlife, and conservation biologists consider them to be one of the worst invasive species on Earth. Attempts to control feral cat populations are widespread but generally of greatest impact within purpose-fenced reserves. In Australia each feral cat kills up to 1000 native animals a year, ranging from crickets to lizards and small mammals. Some feral "catastrophic" cats will develop a taste and skill for hunting larger prey: Indigenous rangers in the Anangu Pitjantjatjara Yangkuntjatjara lands caught a 6.8-kilogram cat with a 5 kilogram rock-wallaby (warru) in its gut.To help protect native animals, feral cats are trapped where possible but are often also shot. Some animal-rights groups advocate trap-neuter-return programs to prevent the cats from continuing to breed, as well as feeding the cats, socializing and adopting out young kittens, and providing healthcare. Others advocate euthanasia. Feral cats may live outdoors in colonies: these are regarded as managed colonies when they are provided with regular food and care by humans.Kairomone
A kairomone (a coinage using the Greek καιρός opportune moment, paralleling pheromone) is a semiochemical, emitted by an organism, which mediates interspecific interactions in a way that benefits an individual of another species which receives it, and harms the emitter. This "eavesdropping" is often disadvantageous to the producer (though other benefits of producing the substance may outweigh this cost, hence its persistence over evolutionary time). The kairomone improves the fitness of the recipient and in this respect differs from an allomone (which is the opposite: it benefits the producer and harms the receiver) and a synomone (which benefits both parties). The term is mostly used in the field of entomology (the study of insects). Two main ecological cues are provided by kairomones; they generally either indicate a food source for the receiver, or the presence of a predator, the latter of which is less common or at least less studied.Leopard seal
The leopard seal (Hydrurga leptonyx), also referred to as the sea leopard, is the second largest species of seal in the Antarctic (after the southern elephant seal). Its only natural predator is the killer whale. It feeds on a wide range of prey including cephalopods, other pinnipeds, krill, birds and fish. It is the only species in the genus Hydrurga. Its closest relatives are the Ross seal, the crabeater seal and the Weddell seal, which together are known as the tribe of Lobodontini seals. The name hydrurga means "water worker" and leptonyx is the Greek for "small clawed".Marsupial lion
The marsupial lion (Thylacoleo carnifex) is an extinct species of carnivorous marsupial mammal that lived in Australia from the early to the late Pleistocene (1,600,000–46,000 years ago). Despite its name, it is not closely related to the lion, but is a member of the order Diprotodontia, one of the taxonomic groups of Australian marsupials.Mesocarnivore
A mesocarnivore is an animal whose diet consists of 30–70% meat with the balance consisting of non-animal foods which may include fungi, fruits, and other plant material. Mesocarnivores are seen today among the Canidae (coyotes, foxes), Viverridae (civets), Mustelidae (martens, tayra), Procyonidae (ringtail, raccoon), Mephitidae (skunks), and Herpestidae (some mongooses).Mesopredator release hypothesis
The mesopredator release hypothesis is an ecological theory used to describe the interrelated population dynamics between apex predators and mesopredators within an ecosystem, such that a collapsing population of the former results in dramatically-increased populations of the latter. This hypothesis describes the phenomenon of trophic cascade in specific terrestrial communities.
A mesopredator is a medium-sized, middle trophic level predator, which both preys and is preyed upon. Examples are raccoons, skunks, snakes, cownose rays, and small sharks.Nile crocodile
The Nile crocodile (Crocodylus niloticus) is an African crocodile, the largest freshwater predator in Africa, and may be considered the second-largest extant reptile and crocodilian in the world, after the saltwater crocodile (Crocodylus porosus). The Nile crocodile is quite widespread throughout sub-Saharan Africa, occurring mostly in the central, eastern, and southern regions of the continent, and lives in different types of aquatic environments such as lakes, rivers, and marshlands. Although capable of living in saline environments, this species is rarely found in saltwater, but occasionally inhabits deltas and brackish lakes. The range of this species once stretched northward throughout the Nile, as far north as the Nile delta. On average, the adult male Nile crocodile is between 3.5 and 5 m (11.5 and 16.4 ft) in length and weighs 225 to 750 kg (500 to 1,650 lb). However, specimens exceeding 6.1 m (20 ft) in length and weighing up to 1,090 kg (2,400 lb) have been recorded. Sexual dimorphism is prevalent, and females are usually about 30% smaller than males. They have thick, scaly, heavily armored skin.
Nile crocodiles are opportunistic apex predators; a very aggressive species of crocodile, they are capable of taking almost any animal within their range. They are generalists, taking a variety of prey. Their diet consists mostly of different species of fish, reptiles, birds, and mammals. They are ambush predators that can wait for hours, days, and even weeks for the suitable moment to attack. They are agile predators and wait for the opportunity for a prey item to come well within attack range. Even swift prey are not immune to attack. Like other crocodiles, Nile crocodiles have an extremely powerful bite that is unique among all animals, and sharp, conical teeth that sink into flesh, allowing for a grip that is almost impossible to loosen. They can apply high levels of force for extended periods of time, a great advantage for holding down large prey underwater to drown.Nile crocodiles are relatively social crocodiles. They share basking spots and large food sources, such as schools of fish and big carcasses. Their strict hierarchy is determined by size. Large, old males are at the top of this hierarchy and have primary access to food and the best basking spots. Crocodiles tend to respect this order; when it is infringed, the results are often violent and sometimes fatal. Like most other reptiles, Nile crocodiles lay eggs; these are guarded by the females. The hatchlings are also protected for a period of time, but hunt by themselves and are not fed by the parents. The Nile crocodile is one of the most dangerous species of crocodile and is responsible for hundreds of human deaths every year. It is a rather common species of crocodile and is not endangered despite some regional declines or extinctions.Productivity (ecology)
In ecology, productivity refers to the rate of generation of biomass in an ecosystem. It is usually expressed in units of mass per unit surface (or volume) per unit time, for instance grams per square metre per day (g m−2 d−1). The mass unit may relate to dry matter or to the mass of carbon generated. Productivity of autotrophs such as plants is called primary productivity, while that of heterotrophs such as animals is called secondary productivity.Rainforest
Rainforests are forests characterized by high rainfall, with annual rainfall in the case of tropical rainforests between 250 and 450 centimetres (98 and 177 in), and definitions varying by region for temperate rainforests. The monsoon trough, alternatively known as the intertropical convergence zone, plays a significant role in creating the climatic conditions necessary for the Earth's tropical rainforests.
Around 40% to 75% of all biotic species are indigenous to the rainforests. There may be many millions of species of plants, insects and microorganisms still undiscovered in tropical rainforests. Tropical rainforests have been called the "jewels of the Earth" and the "world's largest pharmacy", because over one quarter of natural medicines have been discovered there. Rainforests are also responsible for 28% of the world's oxygen turnover, sometimes misnamed oxygen production, processing it through photosynthesis from carbon dioxide and consuming it through respiration.
The undergrowth in some areas of a rainforest can be restricted by poor penetration of sunlight to ground level. If the leaf canopy is destroyed or thinned, the ground beneath is soon colonized by a dense, tangled growth of vines, shrubs and small trees, called a jungle. The term jungle is also sometimes applied to tropical rainforests generally.
Rainforests as well as endemic rainforest species are rapidly disappearing due to deforestation, the resulting habitat loss and pollution of the atmosphere.Refuge (ecology)
A refuge is a concept in ecology, in which an organism obtains protection from predation by hiding in an area where it is inaccessible or cannot easily be found. Due to population dynamics, when refuges are available, populations of both predators and prey are significantly higher, and significantly more species can be supported in an area.Sustainable gardening
Sustainable gardening includes the more specific sustainable landscapes, sustainable landscape design, sustainable landscaping, sustainable landscape architecture, resulting in sustainable sites. It comprises a disparate group of horticultural interests that can share the aims and objectives associated with the international post-1980s sustainable development and sustainability programs developed to address the fact that humans are now using natural biophysical resources faster than they can be replenished by nature.Included within this compass are those home gardeners, and members of the landscape and nursery industries, and municipal authorities, that integrate environmental, social, and economic factors to create a more sustainable future.
Organic gardening and the use of native plants are integral to sustainable gardening.Thylacoleo
Thylacoleo ("pouch lion") is an extinct genus of carnivorous marsupials that lived in Australia from the late Pliocene to the late Pleistocene (2 million to 46 thousand years ago). Some of these "marsupial lions" were the largest mammalian predators in Australia of that time, with Thylacoleo carnifex approaching the weight of a small lion. The estimated average weight for the species ranges from 101 to 130 kg.Trophic cascade
Trophic cascades are powerful indirect interactions that can control entire ecosystems, occurring when a trophic level in a food web is suppressed. For example, a top-down cascade will occur if predators are effective enough in predation to reduce the abundance, or alter the behavior, of their prey, thereby releasing the next lower trophic level from predation (or herbivory if the intermediate trophic level is a herbivore).
The trophic cascade is an ecological concept which has stimulated new research in many areas of ecology. For example, it can be important for understanding the knock-on effects of removing top predators from food webs, as humans have done in many places through hunting and fishing.
A top-down cascade is a trophic cascade where the top consumer/predator controls the primary consumer population. In turn, the primary producer population thrives. The removal of the top predator can alter the food web dynamics. In this case, the primary consumers would overpopulate and exploit the primary producers. Eventually there would not be enough primary producers to sustain the consumer population. Top-down food web stability depends on competition and predation in the higher trophic levels. Invasive species can also alter this cascade by removing or becoming a top predator. This interaction may not always be negative. Studies have shown that certain invasive species have begun to shift cascades; and as a consequence, ecosystem degradation has been repaired.For example, if the abundance of large piscivorous fish is increased in a lake, the abundance of their prey, smaller fish that eat zooplankton, should decrease. The resulting increase in zooplankton should, in turn, cause the biomass of its prey, phytoplankton, to decrease.
In a bottom-up cascade, the population of primary producers will always control the increase/decrease of the energy in the higher trophic levels. Primary producers are plants, phytoplankton and zooplankton that require photosynthesis. Although light is important, primary producer populations are altered by the amount of nutrients in the system. This food web relies on the availability and limitation of resources. All populations will experience growth if there is initially a large amount of nutrients.In a subsidy cascade, species populations at one trophic level can be supplemented by external food. For example, native animals can forage on resources that don't originate in their same habitat, such a native predators eating livestock. This may increase their local abundances thereby affecting other species in the ecosystem and causing an ecological cascade. For example, Luskin et al (2017) found that native animals living in protected primary rainforest in Malaysia found food subsidies in neighboring oil palm plantations. This subsidy allowed native animal populations to increase, which then triggered powerful secondary ‘cascading’ effects on forest tree community. Specifically, crop-raiding wild boar (Sus scrofa) built thousands of nests from the forest understory vegetation and this caused a 62% decline in forest tree sapling density over a 24-year study period. Such cross-boundary subsidy cascades may be widespread in both terrestrial and marine ecosystems and present significant conservation challenges.
These trophic interactions shape patterns of biodiversity globally. Humans and climate change have affected these cascades drastically. One example can be seen with sea otters (Enhydra lutris) on the Pacific coast of the United States of America. Over time, human interactions caused a removal of sea otters. One of their main prey, the pacific purple sea urchin (Strongylocentrotus purpuratus) eventually began to overpopulate. The overpopulation caused increased predation of giant kelp (Macrocystis pyrifera). As a result, there was extreme deterioration of the kelp forests along the California coast. This is why it is important for countries to regulate marine and terrestrial ecosystems.Predator-induced interactions could heavily influence the flux of atmospheric carbon if managed on a global scale. For example, a study was conducted to determine the cost of potential stored carbon in living kelp biomass in Sea Otter enhanced ecosystems. The study valued the potential storage between $205 million and $408 million dollars (US) on the European Carbon Exchange (2012).Trophic level
The trophic level of an organism is the position it occupies in a food chain. A food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. The trophic level of an organism is the number of steps it is from the start of the chain. A food chain starts at trophic level 1 with primary producers such as plants, can move to herbivores at level 2, carnivores at level 3 or higher, and typically finish with apex predators at level 4 or 5. The path along the chain can form either a one-way flow or a food "web". Ecological communities with higher biodiversity form more complex trophic paths.
The word trophic derives from the Greek τροφή (trophē) referring to food or nourishment.