Intraguild predation
Encyclopedia
Intraguild predation, or IGP, is the killing and eating of potential competitors. This interaction represents a combination of predation
and competition
, because both species utilize the same prey resources and also benefit from preying upon one another. Intraguild predation is common in nature and can be asymmetrical, in which one species feeds upon the other, or symmetrical, in which both species prey upon each other. Because the dominant intraguild predator gains the dual benefits of feeding and eliminating a potential competitor, IGP interactions can have considerable effects on the structure of ecological communities.
attached to their prey to direct predation between two apex predator
s.
, and the degree of IGP depends on factors such as the size, growth, and population density of the predators, as well as the population density and behavior of their shared prey. When creating theoretical models for intraguild predation, the competing species are classified as the "top predator" or the "intermediate predator," (the species more likely to be preyed upon). In theory, intraguild predation is most stable if the top predator benefits strongly from feeding on the intermediate predator, and if the intermediate predator is a better competitor for the shared prey resource.
The ecological effects of intraguild predation include direct effects on the survival and distribution of the competing predators, as well as indirect effects on the abundance and distribution of prey species and other species within the community. Because they are so common, IGP interactions are important in structuring communities. Intraguild predation may actually benefit the shared prey species by lowering overall predation pressure, particularly if the intermediate predator consumes more of the shared prey. Intraguild predation can also dampen the effects of trophic cascade
s by providing redundancy in predation: if one predator is removed from the ecosystem, the other is still consuming the same prey species. Asymmetrical IGP can be a particularly strong influence on habitat selection. Often, intermediate predators will avoid otherwise optimal habitat because of the presence of the top predator. Behavioral changes in intermediate predator distribution due to increased risk of predation can influence community structure more than direct mortality caused by the top predators.
s such as insect
s and arachnid
s. Hemiptera
n insects and larval lacewings
both prey upon aphid
s, but the competing predators can cause high enough mortality among the lacewings to effectively relieve predation upon the aphids. Several species of centipede
are considered to be intraguild predators.
Among the most dramatic examples of intraguild predation are those between large mammalian carnivores
. Large canines
and felines
are the mammal groups most often involved in IGP, with larger species such as lion
s and gray wolves
preying upon smaller species such as fox
es and lynx
. In North America, coyote
s function as intraguild predators of gray fox
es and bobcat
s, and may exert a strong influence over the population and distribution of gray foxes. However, in areas where wolves have been reintroduced, coyotes become an intermediate predator and experience increased mortality and a more restricted range.
s show strong IGP interactions, both between species of sharks and with other top predators like toothed whales. In tropical areas where multiple species of sharks may have significantly overlapping diets, the risk of injury or predation can determine the local range and available prey resources for different species. Large pelagic species such as blue
and mako
sharks are rarely observed feeding in the same areas as great white shark
s, and the presence of white sharks will prevent other species from scavenging on whale carcasses. Intraguild predation between sharks and toothed whales usually involves large sharks preying upon dolphin
s and porpoise
s while also competing with them for fish prey, but orca
s reverse this trend by preying upon large sharks while competing for large fish and seal
prey.
Fisheries managers
have only recently begun to understand the importance of intraguild predation on the availability of fish stocks as they attempt to move towards ecosystem-based management
. IGP interactions between sharks and seals may prevent seals from feeding in areas where commercially important fish species are abundant, which may indirectly make more of these fish available to fishermen. However, IGP may also negatively influence fisheries. Intraguild predation by spiny dogfish
and various skate
species on economically important fishes like cod
and haddock
have been cited as a possible reason for the slow recovery of the groundfish
fishery
in the western North Atlantic.
Intraguild predation is also an important consideration for restoring ecosystems. Because the presence of top predators can so strongly affect the distribution and abundance of both intermediate predator and prey species, efforts to either restore or control predator populations can have significant and often unintended ecological consequences. In Yellowstone National Park
, the reintroduction of wolves caused them to become intraguild predators of coyotes, which had far-reaching effects on both the animal and plant communities in the park. Intraguild predation is an important ecological interaction, and conservation and management measures will need to take it into consideration.
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
and competition
Competition (biology)
Competition is an interaction between organisms or species, in which the fitness of one is lowered by the presence of another. Limited supply of at least one resource used by both is required. Competition both within and between species is an important topic in ecology, especially community ecology...
, because both species utilize the same prey resources and also benefit from preying upon one another. Intraguild predation is common in nature and can be asymmetrical, in which one species feeds upon the other, or symmetrical, in which both species prey upon each other. Because the dominant intraguild predator gains the dual benefits of feeding and eliminating a potential competitor, IGP interactions can have considerable effects on the structure of ecological communities.
Types
Intraguild predation can be classified as asymmetrical or symmetrical. In asymmetrical interactions one species consistently preys upon the other, while in symmetrical interactions both species prey equally upon each other. Intraguild predation can also be age structured, in which case the vulnerability of a species to predation is dependent on age and size, so only juveniles or smaller individuals of one of the predators are fed upon by the other. A wide variety of predatory relationships are possible depending on the symmetry of the interaction and the importance of age structure. IGP interactions can range from predators incidentally eating parasitesParasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
attached to their prey to direct predation between two apex predator
Apex predator
Apex predators are predators that have no predators of their own, residing at the top of their food chain. Zoologists define predation as the killing and consumption of another organism...
s.
Ecology of intraguild predation
Intraguild predation is common in nature and widespread across communities and ecosystems. Intraguild predators must share at least one prey species and usually occupy the same trophic guildGuild (ecology)
A guild is any group of species that exploit the same resources, often in related ways. As can be seen from the list of examples below, it does not follow that the species within a guild occupy the same, or even similar, ecological niches...
, and the degree of IGP depends on factors such as the size, growth, and population density of the predators, as well as the population density and behavior of their shared prey. When creating theoretical models for intraguild predation, the competing species are classified as the "top predator" or the "intermediate predator," (the species more likely to be preyed upon). In theory, intraguild predation is most stable if the top predator benefits strongly from feeding on the intermediate predator, and if the intermediate predator is a better competitor for the shared prey resource.
The ecological effects of intraguild predation include direct effects on the survival and distribution of the competing predators, as well as indirect effects on the abundance and distribution of prey species and other species within the community. Because they are so common, IGP interactions are important in structuring communities. Intraguild predation may actually benefit the shared prey species by lowering overall predation pressure, particularly if the intermediate predator consumes more of the shared prey. Intraguild predation can also dampen the effects of trophic cascade
Trophic cascade
Trophic cascades occur when predators in a food web suppress the abundance of their prey, thereby releasing the next lower trophic level from predation...
s by providing redundancy in predation: if one predator is removed from the ecosystem, the other is still consuming the same prey species. Asymmetrical IGP can be a particularly strong influence on habitat selection. Often, intermediate predators will avoid otherwise optimal habitat because of the presence of the top predator. Behavioral changes in intermediate predator distribution due to increased risk of predation can influence community structure more than direct mortality caused by the top predators.
Terrestrial
Intraguild predation is well documented in terrestrial arthropodArthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s such as insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s and arachnid
Arachnid
Arachnids are a class of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although in some species the front pair may convert to a sensory function. The term is derived from the Greek words , meaning "spider".Almost all extant arachnids are terrestrial...
s. Hemiptera
Hemiptera
Hemiptera is an order of insects most often known as the true bugs , comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others...
n insects and larval lacewings
Neuroptera
The insect order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order contains some 6,010 species...
both prey upon aphid
Aphid
Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s, but the competing predators can cause high enough mortality among the lacewings to effectively relieve predation upon the aphids. Several species of centipede
Centipede
Centipedes are arthropods belonging to the class Chilopoda of the subphylum Myriapoda. They are elongated metameric animals with one pair of legs per body segment. Despite the name, centipedes can have a varying number of legs from under 20 to over 300. Centipedes have an odd number of pairs of...
are considered to be intraguild predators.
Among the most dramatic examples of intraguild predation are those between large mammalian carnivores
Carnivora
The diverse order Carnivora |Latin]] carō "flesh", + vorāre "to devour") includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal...
. Large canines
Canidae
Canidae is the biological family of carnivorous and omnivorous mammals that includes wolves, foxes, jackals, coyotes, and domestic dogs. A member of this family is called a canid . The Canidae family is divided into two tribes: Canini and Vulpini...
and felines
Felidae
Felidae is the biological family of the cats; a member of this family is called a felid. Felids are the strictest carnivores of the thirteen terrestrial families in the order Carnivora, although the three families of marine mammals comprising the superfamily pinnipedia are as carnivorous as the...
are the mammal groups most often involved in IGP, with larger species such as lion
Lion
The lion is one of the four big cats in the genus Panthera, and a member of the family Felidae. With some males exceeding 250 kg in weight, it is the second-largest living cat after the tiger...
s and gray wolves
Gray Wolf
The gray wolf , also known as the wolf, is the largest extant wild member of the Canidae family...
preying upon smaller species such as fox
Fox
Fox is a common name for many species of omnivorous mammals belonging to the Canidae family. Foxes are small to medium-sized canids , characterized by possessing a long narrow snout, and a bushy tail .Members of about 37 species are referred to as foxes, of which only 12 species actually belong to...
es and lynx
Lynx
A lynx is any of the four Lynx genus species of medium-sized wildcats. The name "lynx" originated in Middle English via Latin from Greek word "λύγξ", derived from the Indo-European root "*leuk-", meaning "light, brightness", in reference to the luminescence of its reflective eyes...
. In North America, coyote
Coyote
The coyote , also known as the American jackal or the prairie wolf, is a species of canine found throughout North and Central America, ranging from Panama in the south, north through Mexico, the United States and Canada...
s function as intraguild predators of gray fox
Gray Fox
The gray fox is a mammal of the order Carnivora ranging throughout most of the southern half of North America from southern Canada to the northern part of South America...
es and bobcat
Bobcat
The bobcat is a North American mammal of the cat family Felidae, appearing during the Irvingtonian stage of around 1.8 million years ago . With twelve recognized subspecies, it ranges from southern Canada to northern Mexico, including most of the continental United States...
s, and may exert a strong influence over the population and distribution of gray foxes. However, in areas where wolves have been reintroduced, coyotes become an intermediate predator and experience increased mortality and a more restricted range.
Aquatic/marine
Intraguild predation is also important in aquaitic and marine ecosystems. As top predators in most marine environments, sharkShark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
s show strong IGP interactions, both between species of sharks and with other top predators like toothed whales. In tropical areas where multiple species of sharks may have significantly overlapping diets, the risk of injury or predation can determine the local range and available prey resources for different species. Large pelagic species such as blue
Blue shark
The blue shark is a species of requiem shark, family Carcharhinidae, that inhabits deep waters in the world's temperate and tropical oceans. Preferring cooler waters, blue sharks migrate long distances, for example from New England to South America. Although generally lethargic, they can move very...
and mako
Shortfin mako shark
The shortfin mako shark, Isurus oxyrinchus , is a large mackerel shark. Along with the closely related longfin mako it is commonly referred to as a "mako shark".-Etymology:...
sharks are rarely observed feeding in the same areas as great white shark
Great white shark
The great white shark, scientific name Carcharodon carcharias, also known as the great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. It is known for its size, with the largest individuals known to have approached...
s, and the presence of white sharks will prevent other species from scavenging on whale carcasses. Intraguild predation between sharks and toothed whales usually involves large sharks preying upon dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s and porpoise
Porpoise
Porpoises are small cetaceans of the family Phocoenidae; they are related to whales and dolphins. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors and fishermen...
s while also competing with them for fish prey, but orca
Orca
The killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...
s reverse this trend by preying upon large sharks while competing for large fish and seal
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
prey.
Importance to management and conservation
The presence and intensity of intraguild predation is important to both management and conservation of species. Human influence on communities and ecosystems can affect the balance of these interactions, and the direct and indirect effects of IGP may have economic consequences.Fisheries managers
Fisheries management
Fisheries management draws on fisheries science in order to find ways to protect fishery resources so sustainable exploitation is possible. Modern fisheries management is often referred to as a governmental system of appropriate management rules based on defined objectives and a mix of management...
have only recently begun to understand the importance of intraguild predation on the availability of fish stocks as they attempt to move towards ecosystem-based management
Ecosystem-based management
Ecosystem-based management is an environmental management approach that recognizes the full array of interactions within an ecosystem, including humans, rather than considering single issues, species, or ecosystem services in isolation Ecosystem-based management is an environmental management...
. IGP interactions between sharks and seals may prevent seals from feeding in areas where commercially important fish species are abundant, which may indirectly make more of these fish available to fishermen. However, IGP may also negatively influence fisheries. Intraguild predation by spiny dogfish
Spiny dogfish
The spiny dogfish, spurdog, mud shark, or piked dogfish, Squalus acanthias, is one of the best known of the dogfish which are members of the family Squalidae in the order Squaliformes. While these common names may apply to several species, Squalus acanthias is distinguished by having two spines ...
and various skate
Skate
Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. There are more than 200 described species in 27 genera. There are two subfamilies, Rajinae and Arhynchobatinae ....
species on economically important fishes like cod
Atlantic cod
The Atlantic cod, Gadus morhua, is a well-known demersal food fish belonging to the family Gadidae. It is also commercially known as cod, codling or haberdine....
and haddock
Haddock
The haddock , also known as the offshore hake, is a marine fish distributed on both sides of the North Atlantic. Haddock is a popular food fish and is widely fished commercially....
have been cited as a possible reason for the slow recovery of the groundfish
Groundfish
Groundfish are fish that live on, in, or near the bottom of the body of water they inhabit. Some typical saltwater groundfish species are sole, flounder, and halibut....
fishery
Georges Bank
Georges Bank is a large elevated area of the sea floor which separates the Gulf of Maine from the Atlantic Ocean and is situated between Cape Cod, Massachusetts and Cape Sable Island, Nova Scotia ....
in the western North Atlantic.
Intraguild predation is also an important consideration for restoring ecosystems. Because the presence of top predators can so strongly affect the distribution and abundance of both intermediate predator and prey species, efforts to either restore or control predator populations can have significant and often unintended ecological consequences. In Yellowstone National Park
Yellowstone National Park
Yellowstone National Park, established by the U.S. Congress and signed into law by President Ulysses S. Grant on March 1, 1872, is a national park located primarily in the U.S. state of Wyoming, although it also extends into Montana and Idaho...
, the reintroduction of wolves caused them to become intraguild predators of coyotes, which had far-reaching effects on both the animal and plant communities in the park. Intraguild predation is an important ecological interaction, and conservation and management measures will need to take it into consideration.