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, [1] [2] and significantly more species can be supported in an area. [3] [4]
Coral reefs provide the most dramatic demonstration of the ecological effects of refuges. [5] [6] Refuge-rich coral reefs contain a full 25% of ocean species, even though such reefs make up just 0.1% of the ocean's surface area. [7] [8] [9] [10] On the other hand, in the sunlight-illuminated open ocean just offshore, there are no places to hide from predation, and both diversity and quantities of organisms per unit area is much lower. [11] Additionally, coral reefs enhance non-local diversity by providing spawning grounds and a refuge habitat for juvenile fishes that will live in the open ocean as adults. [12]
Rainforest species diversity is also in large part the result of diverse and numerous physical refuges. [13]
Prey animals typically maintain larger populations when they have a place to physically hide from predation. For example, rats maintain a higher population density if the rats have refuges such as tall grass, allowing them to hide from predators such as owls and cats. [14] Sea birds often have nesting colonies on islands but not on nearby, apparently suitable, mainland sites. The islands lack the mammalian predators found on the mainland, such as cats, dogs, and rats, all of which typically decimate seabird colonies. [15] Semiaquatic animals, e.g. mouse-deer, may use bodies of water as refuges. [16]
Game reserves have been deliberately used to enhance the total population of large game, e.g. deer, for at least a century. [17] Limiting hunting by humans in a relatively small area allows the overall population to rebound. [18] The same principle applies to fisheries, which produce more fish when there is a nearby refuge from human predation in the form of a nature reserve, resulting in higher catches than if the whole area was open to fishing. [19] [20] [21] In human-managed systems like these, heavily hunted areas act as a sink in which animals die faster than they reproduce, but are replaced by animals migrating from the protected nature reserve area. [22]
Many prey animals systematically migrate between refuges and predator-rich feeding grounds, in patterns that minimize their chances of being caught by the predators. The largest such migration by biomass is the oceans' diel vertical migration, in which vast quantities of organisms hide in the lightless depths of the open ocean, arising after dark to consume phytoplankton. [23] This allows them to avoid the large predatory fish of the open ocean, as these predators are primarily visual hunters and need light to effectively catch prey. Similar types of migration also occur in fresh water. For example, small European perch exhibit a daily horizontal migration in some lakes in Finland. During the day they move away from the vegetated areas where the predation threat in the clear water is great, into more turbid open water areas, moving back at night because of the greater availability of zooplankton among the aquatic plants. [24]
Refuge use reduces the likelihood of species extinction. [6] There have been a number of mass extinction events. During some of these, denizens of the deep ocean have been relatively immune. The coelacanth for example, is a remnant species of a once common group of fishes, the Sarcopterygii, which disappeared from shallow seas at the time of the Cretaceous–Paleogene extinction event 66 million years ago, leaving only a couple of surviving species. [25] [26] Many coral taxa have used the deep ocean as a refuge, shifting from shallow to deep water and vice versa during their evolutionary history. [27] By developing wings and taking flight, insects exploited the air as a refuge, a place of safety from ground-based predators; this successful evolutionary strategy set the insects on the path to occupying the dominant position they hold today. [28]
Human societies show a similar effect, with remote mountainous regions such as Zomia or the Scottish Highlands serving as refugia, allowing their inhabitants to maintain cultural traditions and languages that were being pushed to extinction in more accessible locations. [29] [30]
Refuge from predators often depends on the size of the prey, meaning that individuals under or over a specific size cannot be consumed by the predator.
The small individuals are more likely to be able to tuck themselves away in some hole or cranny, or if, like barnacles, they are living on an exposed surface, are of negligible interest to predators like starfish because of their small size. Another example is the tidepool sculpin, which takes refuge in small rockpools when the tide is out, thus taking advantage of its small size and avoiding its larger fish predators. [31]
Large individuals may escape predators by being too large to be consumed, or their size allowing them to inhabit areas free of predators. Often larger individuals can still be consumed by predators, but the predator will prefer small prey as these require less work (handling) and the predator is less likely to get hurt by small individuals. Leading to a larger return on investment. An example is the rock lobster which can consume large individuals of the pink-lipped topshell, but will preferentially consume small individuals when given the choice. [32] Some barnacles escape predators by settling further up the shore, away from predators. There the starfish cannot reach them when the tide is out, nor can whelks drill through their shells because they remain submerged for insufficient time during each tidal cycle. [33] In this situation, size is a refuge in itself, in that it enables the barnacle to escape desiccation under circumstances that might be lethal to smaller individuals. [33]
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation and parasitoidism. It is distinct from scavenging on dead prey, though many predators also scavenge; it overlaps with herbivory, as seed predators and destructive frugivores are predators.
Moray eels, or Muraenidae, are a family of eels whose members are found worldwide. There are approximately 200 species in 15 genera which are almost exclusively marine, but several species are regularly seen in brackish water, and a few are found in fresh water.
The crown-of-thorns starfish, Acanthaster planci, is a large starfish that preys upon hard, or stony, coral polyps (Scleractinia). The crown-of-thorns starfish receives its name from venomous thorn-like spines that cover its upper surface, resembling the biblical crown of thorns. It is one of the largest starfish in the world.
An apex predator, also known as a top predator, is a predator at the top of a food chain, without natural predators of its own.
The red lionfish is a venomous coral reef fish in the family Scorpaenidae, order Scorpaeniformes. It is mainly native to the Indo-Pacific region, but has become an invasive species in the Caribbean Sea, as well as along the East Coast of the United States and East Mediterranean and also found in Brazil at Fernando de Noronha.
The California sheephead is a species of wrasse native to the eastern Pacific Ocean. Its range is from Monterey Bay, California, to the Gulf of California, Mexico. It can live for up to 20 years in favorable conditions and can reach a size of up to 91 cm (3 ft) and a weight of 16 kg (35 lb). It is carnivorous, living in rocky reef and kelp bed habitats, feeding primarily on sea urchins, molluscs, and crustaceans.
The orange-lined triggerfish is a demersal triggerfish. Although Balistapus is a monotypic genus, it is closely related to the genus Balistoides.
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.
Panulirus argus, the Caribbean spiny lobster, is a species of spiny lobster that lives on reefs and in mangrove swamps in the western Atlantic Ocean.
Marine larval ecology is the study of the factors influencing dispersing larvae, which many marine invertebrates and fishes have. Marine animals with a larva typically release many larvae into the water column, where the larvae develop before metamorphosing into adults.
A spongivore is an animal anatomically and physiologically adapted to eating animals of the phylum Porifera, commonly called sea sponges, for the main component of its diet. As a result of their diet, spongivore animals like the hawksbill turtle have developed sharp, narrow bird-like beak that allows them to reach within crevices on the reef to obtain sponges.
A wild fishery is a natural body of water with a sizeable free-ranging fish or other aquatic animal population that can be harvested for its commercial value. Wild fisheries can be marine (saltwater) or lacustrine/riverine (freshwater), and rely heavily on the carrying capacity of the local aquatic ecosystem.
Ostorhinchus cyanosoma, commonly known as the yellow-striped cardinalfish, goldenstriped cardinalfish, or the orange-lined cardinalfish, is a species of marine fish in the cardinalfish family of order Perciformes. It is native to the Indo-West Pacific.
Pseudochromis fuscus is a species of saltwater fish in the dottyback family. Dottybacks are generally very bright in color and relatively small, factors which have made them popular among aquarium enthusiasts. Besides their coloration and size, they are probably best known for their aggressive temperament. While many of the more common dottybacks are in the Pseudochromis genus, there are also species in other genera. Common names for this particular species include the brown dottyback, the golden dottyback, and the musky dottyback. The common name “Golden dottyback” is shared with another species of dottyback, the Pseudochromis pseudoplesiopinae. The species name, fuscus, means dark or dusky in Latin.
In biology, any group of fish that stay together for social reasons are shoaling, and if the group is swimming in the same direction in a coordinated manner, they are schooling. In common usage, the terms are sometimes used rather loosely. About one quarter of fish species shoal all their lives, and about one half shoal for part of their lives.
Coral reef fish are fish which live amongst or in close relation to coral reefs. Coral reefs form complex ecosystems with tremendous biodiversity. Among the myriad inhabitants, the fish stand out as colourful and interesting to watch. Hundreds of species can exist in a small area of a healthy reef, many of them hidden or well camouflaged. Reef fish have developed many ingenious specialisations adapted to survival on the reefs.
Intraguild predation, or IGP, is the killing and sometimes eating of a potential competitor of a different species. This interaction represents a combination of predation and competition, because both species rely on 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.
A planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton. Planktivorous organisms encompass a range of some of the planet's smallest to largest multicellular animals in both the present day and in the past billion years; basking sharks and copepods are just two examples of giant and microscopic organisms that feed upon plankton. Planktivory can be an important mechanism of top-down control that contributes to trophic cascades in aquatic and marine systems. There is a tremendous diversity of feeding strategies and behaviors that planktivores utilize to capture prey. Some planktivores utilize tides and currents to migrate between estuaries and coastal waters; other aquatic planktivores reside in lakes or reservoirs where diverse assemblages of plankton are present, or migrate vertically in the water column searching for prey. Planktivore populations can impact the abundance and community composition of planktonic species through their predation pressure, and planktivore migrations facilitate nutrient transport between benthic and pelagic habitats.
Pterois is a genus of venomous marine fish, commonly known as lionfish, native to the Indo-Pacific. It is characterized by conspicuous warning coloration with red or black bands, and ostentatious dorsal fins tipped with venomous spines. Pterois radiata, Pterois volitans, and Pterois miles are the most commonly studied species in the genus. Pterois species are popular aquarium fish. P. volitans and P. miles are recent and significant invasive species in the west Atlantic, Caribbean Sea and Mediterranean Sea.
Compared to terrestrial environments, marine environments have biomass pyramids which are inverted at the base. In particular, the biomass of consumers is larger than the biomass of primary producers. This happens because the ocean's primary producers are tiny phytoplankton which grow and reproduce rapidly, so a small mass can have a fast rate of primary production. In contrast, many significant terrestrial primary producers, such as mature forests, grow and reproduce slowly, so a much larger mass is needed to achieve the same rate of primary production.