Egg predation

Egg predation is a feeding strategy by animals (ovivores) including fish, birds, snakes and insects, in which they consume the eggs of other species. Since an egg represents a complete organism at one stage of its life cycle, eating an egg is a form of predation, the killing of another organism for food.

Egg predation is found widely across the animal kingdom, including in insects such as ladybirds, molluscs such as the leech Cystobranchus virginicus, fishes such as haddock, snakes such as colubrids, birds such as carrion crow and buzzard, and mammals such as red fox, badgers and pine martens. Some species are specialist egg predators, but many more are generalists which take eggs when the opportunity arises.

Snakes specialising in egg predation have greatly reduced venom, implying that the main function of venom is to subdue prey.

Pseudechis porphyriacus eating eggs
A red-bellied black snake Pseudechis porphyriacus eating eggs of the green tree snake Dendrelaphis punctulatus

Ecological relationship

Corvus ossifragus and egg
Generalist and omnivorous[1] predators like this fish crow, Corvus ossifragus, eat eggs among many other prey when they have the opportunity.

Egg predation is an ecological relationship in which an animal (a predator) hunts for and eats the eggs of another (prey) species. This reduces the evolutionary fitness of the parents whose eggs are preyed on. Among birds such as eider ducks in one study, half the individuals started a fresh clutch of eggs, always in a new nest, and they always avoided the area around the robbed nest.[2] Egg predation rates can be high for ground-nesting birds such as the European golden plover, Pluvialis apricaria: in Norway 78.2% of nests of this species were preyed on. Experimental removal of two nest and egg predators, red fox and carrion crow, in another study raised the percentage of pairs that fledged young from c. 18% to c. 75%. Population increases among many generalist predators such as buzzard, badger, carrion crow, pine marten, raven, and red fox in Scotland have contributed to the decline in several ground-nesting bird species by taking eggs, young, and sitting hen (female) birds.[3]

Among fish, egg predation by species such as haddock (Melanogrammus aeglefinus) can contribute to the decline in other fish populations such as of Atlantic herring (Clupea harengus). This effect can be important in attempts to restore fisheries damaged by overfishing.[4]

Invasive species such as the harlequin ladybird Harmonia axyridis frequently prey on eggs and young of native species, in its case including those of other ladybirds such as the two-spot ladybird Adalia bipunctata. Females of the prey species laid eggs with higher amounts of defensive alkaloids when egg predation was occurring.[5]

Some colubrid snakes such as the Formosa kukri snake Oligodon formosanus specialise in egg predation.[6] Egg predation by snakes is rarely opposed, but the Asian long-tailed skink Eutropis longicaudata aggressively protects its eggs from the Formosa kukri snake.[7][8]

Egg-eating snakes such as the marbled sea snake Aipysurus eydouxii have atrophied venom glands; this has been explained as an evolutionary consequence of their diet, since venom is not required to subdue their prey, unlike the case in their venomous and conventionally predatory ancestors.[9]

The aquatic piscicolid leech Cystobranchus virginicus is an egg predator; it may be an obligate egg-feeder as it has not been seen feeding on an adult but has been found in the nests of a variety of species of North American freshwater fish of the genera Campostoma and Moxostoma.[10]

See also

References

  1. ^ Goodwin, D. (1983). Crows of the World. Queensland University Press. p. 92. ISBN 0-7022-1015-3.
  2. ^ Hanssen, Sveinn Are; Erikstad, Kjell Einar (2012). "The long-term consequences of egg predation". Behavioral Ecology. 24 (2): 564–569. doi:10.1093/beheco/ars198.
  3. ^ Ainsworth, Gill; Calladine, John; Martay, Blaise; Park, Kirsty; Redpath, Steve; Wernham, Chris; Wilson, Mark; Young, Juliette (2017). Understanding Predation | A review bringing together natural science and local knowledge of recent wild bird population changes and their drivers in Scotland. Scotland's Moorland Forum. pp. 233–234.
  4. ^ Paul, Sarah C.; Stevens, Martin; Burton, Jake; Pell, Judith K.; Birkett, Michael A.; Blount, Jonathan D. (2018). "Invasive Egg Predators and Food Availability Interactively Affect Maternal Investment in Egg Chemical Defense". Frontiers in Ecology and Evolution. 6. doi:10.3389/fevo.2018.00004.
  5. ^ Pike, David A.; Clark, Rulon W.; Manica, Andrea; Tseng, Hui-Yun; Hsu, Jung-Ya; Huang, Wen-San (2016-02-26). "Surf and turf: predation by egg-eating snakes has led to the evolution of parental care in a terrestrial lizard". Scientific Reports. 6 (1). doi:10.1038/srep22207.
  6. ^ "Snakes meet their match in offspring-protecting lizards". Phys.org. 30 January 2013. Retrieved 11 September 2018.
  7. ^ Huang, Wen-San; Lin, Si-Min; Dubey, Sylvain; Pike, David A. (2012). Coulson, Tim (ed.). "Predation drives interpopulation differences in parental care expression". Journal of Animal Ecology. 82 (2): 429–437. doi:10.1111/1365-2656.12015.
  8. ^ Li, Min; Fry, B.G.; Kini, R. Manjunatha (2005). "Eggs-Only Diet: Its Implications for the Toxin Profile Changes and Ecology of the Marbled Sea Snake (Aipysurus eydouxii)". Journal of Molecular Evolution. 60 (1): 81–89. doi:10.1007/s00239-004-0138-0.
  9. ^ Light, Jessica E.; Fiumera, Anthony C.; Porter, Brady A. (2005). "Egg-feeding in the freshwater piscicolid leech Cystobranchus virginicus (Annelida, Hirudinea)". Invertebrate Biology. 124 (1): 50–56. doi:10.1111/j.1744-7410.2005.1241-06.x.
Avivore

An avivore is a specialized predator of birds, with birds making up a large proportion of its diet. Such bird-eating animals come from a range of groups.

Bacterivore

Bacterivores are free-living, generally heterotrophic organisms, exclusively microscopic, which obtain energy and nutrients primarily or entirely from the consumption of bacteria. Many species of amoeba are bacterivores, as well as other types of protozoans. Commonly, all species of bacteria will be prey, but spores of some species, such as Clostridium perfringens, will never be prey, because of their cellular attributes.

Bottom feeder

A bottom feeder is an aquatic animal that feeds on or near the bottom of a body of water. The body of water could be the ocean, a lake, a river, or an aquarium. Bottom feeder is a term used particularly with aquariums. Biologists often use the terms benthos — particularly for invertebrates such as shellfish, crabs, crayfish, sea anemones, starfish, snails, bristleworms and sea cucumbers — and benthivore or benthivorous, for fish and invertebrates that feed on material from the bottom. However the term benthos includes all aquatic life that lives on or near the bottom, which means it also includes non-animals, such as plants and algae.

Biologists also use specific terms that refer to bottom feeding fish, such as demersal fish, groundfish, benthic fish and benthopelagic fish. Examples of bottom feeding fish species groups are flatfish (halibut, flounder, plaice, sole), eels, cod, haddock, bass, grouper, carp, bream (snapper) and some species of catfish and shark.

Decomposer

Decomposers are organisms that break down dead or decaying organisms, and in doing so, they carry out the natural process of decomposition. Like herbivores and predators, decomposers are heterotrophic, meaning that they use organic substrates to get their energy, carbon and nutrients for growth and development. While the terms decomposer and detritivore are often interchangeably used, detritivores must ingest and digest dead matter via internal processes while decomposers can directly absorb nutrients through chemical and biological processes hence breaking down matter without ingesting it. Thus, invertebrates such as earthworms, woodlice, and sea cucumbers are technically detritivores, not decomposers, since they must ingest nutrients and are unable to absorb them externally.

Florivore

In zoology, a florivore (not to be confused with a folivore) is an animal which mainly eats products of flowers. Florivores are types of herbivores (often referred to as floral herbivores), yet within the feeding behaviour of florivory, there are a range of other more specific feeding behaviours, including, but not limited to:

Granivory: the consumption of grain and seeds

Nectarivory: the consumption of flower nectar

Palynivory: the consumption of flower pollen

Frugivory: the consumption of fruit

Folivore

In zoology, a folivore is a herbivore that specializes in eating leaves. Mature leaves contain a high proportion of hard-to-digest cellulose, less energy than other types of foods, and often toxic compounds. For this reason, folivorous animals tend to have long digestive tracts and slow metabolisms. Many enlist the help of symbiotic bacteria to release the nutrients in their diet. Additionally, as has been observed in folivorous primates, they exhibit a strong preference towards immature leaves, which tend to be easier to masticate, tend to be higher in energy and protein, and lower in fibre and poisons than more mature fibrous leaves.

Hypercarnivore

A hypercarnivore is an animal which has a diet that is more than 70% meat, with the balance consisting of non-animal foods such as fungi, fruits or other plant material. Some extant examples include crocodilians, owls, shrikes, eagles, vultures, felids, most wild canids, dolphins, orcas, snakes, spiders, scorpions, mantises, marlins, groupers, and most sharks. Every species in the Felidae family, including the domesticated cat, is a hypercarnivore in its natural state. Additionally, this term is also used in paleobiology to describe taxa of animals which have an increased slicing component of their dentition relative to the grinding component. Hypercarnivores per definition need not be apex predators. For example, salmon are exclusively carnivorous, yet they are prey at all stages of life for a variety of organisms.

Many prehistoric mammals of the clade Carnivoramorpha (Carnivora and Miacoidea without Creodonta), along with the early order Creodonta, and some mammals of the even earlier order Cimolesta, were hypercarnivores. The earliest carnivorous mammal is considered to be Cimolestes, which existed during the Late Cretaceous and early Paleogene periods in North America about 66 million years ago. Theropod dinosaurs such as Tyrannosaurus rex that existed during the late Cretaceous, although not mammals, were obligate carnivores.

Large hypercarnivores evolved frequently in the fossil record, often in response to an ecological opportunity afforded by the decline or extinction of previously dominant hypercarnivorous taxa. While the evolution of large size and carnivory may be favored at the individual level, it can lead to a macroevolutionary decline, wherein such extreme dietary specialization results in reduced population densities and a greater vulnerability for extinction. As a result of these opposing forces, the fossil record of carnivores is dominated by successive clades of hypercarnivores that diversify and decline, only to be replaced by new hypercarnivorous clades.

As an example of related species with differing diets, even though they diverged only 150,000 years ago, the polar bear is the most highly carnivorous bear (more than 90% of its diet is meat) while the grizzly bear is one of the least carnivorous in many locales, with less than 10% of its diet being meat.

List of feeding behaviours

Feeding is the process by which organisms, typically animals, obtain food. Terminology often uses either the suffixes -vore, -vory, -vorous from Latin vorare, meaning "to devour", or -phage, -phagy, -phagous from Greek φαγειν (phagein), meaning "to eat".

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).

Mucophagy

Mucophagy (literally "mucus feeding") is feeding on mucus of fishes or invertebrates. It may also refer to consumption of mucus or dried mucus in primates.

There are mucophagous parasites, such as some sea lice that attach themselves to gill segments of fish.Mucophages may serve as cleaners of other animals.

Another usage of this term is in reference to the feeding organ rich in mucous cells which pumps the water through, feeding particles get entrapped in mucus, and the latter proceeds into the esophagus.

Myzocytosis

Myzocytosis (from Greek: myzein, (μυζεῖν) meaning "to suck" and kytos (κύτος) meaning "container", hence referring to "cell") is a method of feeding found in some heterotrophic organisms. It is also called "cellular vampirism" as the predatory cell pierces the cell wall and/or cell membrane of the prey cell with a feeding tube, the conoid, sucks out the cellular content and digests it.

Myzocytosis is found in Myzozoa and also in some species of Ciliophora (both comprise the alveolates). A classic example of myzocytosis is the feeding method of the infamous predatory ciliate, Didinium, where it is often depicted devouring a hapless Paramecium. The suctorian ciliates were originally thought to have fed exclusively through myzocytosis, sucking out the cytoplasm of prey via superficially drinking straw-like pseudopodia. It is now understood that suctorians do not feed through myzocytosis, but actually, instead, manipulate and envenomate captured prey with their tentacle-like pseudopodia.

Oophagy

Oophagy ( oh-OFF-ə-jee) sometimes ovophagy, literally "egg eating", is the practice of

embryos feeding on eggs produced by the ovary while still inside the mother's uterus. The word oophagy is formed from the classical Greek ᾠόν (ōion, egg) and classical Greek φᾱγεῖν (phāgein, to eat). In contrast, adelphophagy is the cannibalism of a multi-celled embryo.

Oophagy is thought to occur in all sharks in the order Lamniformes and has been recorded in the bigeye thresher (Alopias superciliosus), the pelagic thresher (A. pelagicus), the shortfin mako (Isurus oxyrinchus) and the porbeagle (Lamna nasus) among others. It also occurs in the tawny nurse shark (Nebrius ferrugineus), and in the family Pseudotriakidae.

This practice may lead to larger embryos or prepare it for a predatory lifestyle.There are variations in the extent of oophagy among the different shark species. The grey nurse shark (Carcharias taurus) practices intrauterine cannibalism, the first developed embryo consuming both additional eggs and any other developing embryos. Slender smooth-hounds

(Gollum attenuatus), form egg capsules which contain 30-80 ova within which only one ovum develops while all other ova are ingested and packed to an external yolk sac. The embryo then develops normally without ingesting further eggs.Oophagy is also used as a synonym of egg predation practised by some snakes and other animals. Similarly, the term can be used to describe the destruction of non-queen eggs in nests of certain social wasps, bees, and ants. This is seen in the wasp species Polistes biglumis and Polistes humilis. Oophagy has been observed in Leptothorax acervorum and Parachartergus fraternus, where oophagy is practiced to increase energy circulation and consume more protein. Polistes fuscatus use oophagy as a method to establish a dominance hierarchy; dominant females will eat the eggs of subordinate females such that they no longer produce eggs, possibly due to the unnecessary expending of energy and resources. This behavior has also been observed in some bee species. Bee species include Xylocopa sulcatipes and Bombus ruderatus, where queen bees will eat the larva deposited by workers or ejected them from the nest in order to maintain dominance over the female workers.

Paedophagy

Paedophagy (literally meaning the "consumption of children") in its general form is the feeding behaviour of fish or other animals whose diet is partially, or primarily the eggs or larvae of other animals. However, P. H. Greenwood, who was the first to describe paedophagia, defines it to be a feeding behaviour evolved among cichlid fishes.

Planktivore

A planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton.

Polybia rejecta

Polybia rejecta is a species of social wasp found in the Neotropics region of the world. It was discovered by Fabricius in South America in the 1790s. The wasp is associated with many other organisms, particularly specific species of ants and birds such as the Azteca ants and the cacique birds. This association is most beneficial to the ants and birds because of the aggressive protective nature of the wasp. The wasps will protect their nest even if it means death against any predator that approaches it and therefore this means that the association also protects the ants and birds. Additionally, the wasp is known for eating the eggs of red eyed tree frogs as a main way of subsistence. It also, like many other wasp species, has a caste system of queens and workers that is evident by difference in body size among the wasps; the biggest female becomes the queen.

Predation

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 (which usually do not kill the host) and parasitoidism (which always does, eventually). It is distinct from scavenging on dead prey, though many predators also scavenge; it overlaps with herbivory, as a seed predator is both a predator and a herbivore.

Predators may actively search for prey or sit and wait for it. When prey is detected, the predator assesses whether to attack it. This may involve ambush or pursuit predation, sometimes after stalking the prey. If the attack is successful, the predator kills the prey, removes any inedible parts like the shell or spines, and eats it.

Predators are adapted and often highly specialized for hunting, with acute senses such as vision, hearing, or smell. Many predatory animals, both vertebrate and invertebrate, have sharp claws or jaws to grip, kill, and cut up their prey. Other adaptations include stealth and aggressive mimicry that improve hunting efficiency.

Predation has a powerful selective effect on prey, and the prey develop antipredator adaptations such as warning coloration, alarm calls and other signals, camouflage, mimicry of well-defended species, and defensive spines and chemicals. Sometimes predator and prey find themselves in an evolutionary arms race, a cycle of adaptations and counter-adaptations. Predation has been a major driver of evolution since at least the Cambrian period.

Saprophagy

Saprophages are organisms that obtain nutrients by consuming decomposing dead plant or animal biomass. They are distinguished from detritivores in that saprophages are sessile consumers while detritivore are mobile. Typical saprophagic animals include sedentary polychaetes such as amphitrites (Amphitritinae, worms of the family Terebellidae) and other terebellids.

The eating of wood, whether live or dead, is known as xylophagy. Τhe activity of animals feeding only on dead wood is called sapro-xylophagy and those animals, sapro-xylophagous.

Vermivore

Vermivore (from Latin vermi, meaning "worm" and vorare, "to devour") is a zoological term for animals that eat worms (including annelids, nematodes, and other worm-like animals). Animals with such a diet are known to be vermivorous. Some definitions are less exclusive with respect to the diet, but limit the definition to particular animals, e.g. "Feeding on worms or insect vermin. Used of a bird."An entire genus of New World warblers has been given the name Vermivora.

One vermivore that may feed exclusively on worms is Paucidentomys vermidax, a rodent species of a type commonly known as shrew rats which was discovered in 2011 in Indonesia. The name, which can be translated as "worm-eating, few-toothed mouse", refers to the fact that they have only four teeth and may live exclusively on a diet of earthworms. This reduced dentition in vermivorous mammals is said to be due to relaxed selectional pressure on dental occlusion.

Xylophagy

Xylophagy is a term used in ecology to describe the habits of an herbivorous animal whose diet consists primarily (often solely) of wood. The word derives from Greek ξυλοφάγος (xulophagos) "eating wood", from ξύλον (xulon) "wood" and φαγεῖν (phagein) "to eat", an ancient Greek name for a kind of a worm-eating bird. Animals feeding only on dead wood are called sapro-xylophagous or saproxylic.

Carnivores
Herbivores
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