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Herbivore, Omnivore, Insectivore
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 components. For this reason, folivorous animals tend to have long digestive tracts and slow metabolisms.
Many folivores 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 for 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.
The Evolution of Herbivory
Herbivory has evolved several times among different groups of animals. The first vertebrates were small fish that consumed protists and invertebrates. After these fish, the next group of vertebrates to evolve were piscivores, then insectivores, carnivores and finally herbivores. Since a complex set of adaptations was necessary for feeding on highly fibrous plant materials (structural modifications to the teeth, jaws, and digestive tract) and only a small proportion of extant tetrapods are obligate herbivores, it could be that early tetrapods made the transition to fully fledged herbivory by way of omnivory.
Folivorous Primates
Standard ecological theory predicts relatively large group sizes for folivorous primates, as large groups offer better collective defence against predators and they face little competition for food among each other. It has been observed that these animals nevertheless frequently live in small groups. Explanations offered for this apparent paradox include social factors such as increased incidence of infanticide in large groups.
Folivorous primates are relatively rare in the New World, the primary exception being howler monkeys. One explanation that has been offered is that fruiting and leafing occur simultaneously among New World plants. However a 2001 study found no evidence for simultaneous fruiting and leafing at most sites, apparently disproving this hypothesis.
Impressive Climbers
Arboreal mammalian folivores, such as sloths, koalas, and some species of monkeys and lemurs, tend to be large and climb cautiously. Similarities in body shape and head- and tooth-structure between early hominoids and various families of arboreal folivores have been advanced as evidence that early hominoids were also folivorous.
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An insectivore is a carnivorous plant or animal that eats insects. The first vertebrate insectivores were amphibians. When they evolved 400 million years ago, the first amphibians were piscivores, with numerous sharp conical teeth, much like a modern crocodile.
Although individually small, insects exist in enormous numbers. Insects make up a very large part of the animal biomass in almost all non-marine, non-polar environments. It has been estimated that the global insect biomass is in the region of 1,000,000,000,000 (1 trillion) kg with an estimated population of 1,000,000,000,000,000,000 (1 quintillion) organisms. Many creatures depend on insects as their primary diet, and many that do not (and are thus not technically insectivores) nevertheless use insects as a protein supplement, particularly when they are breeding.
Definition and Related Terms
Insectivores are predators that catch and eat insects. These predators may also eat other small invertebrates, such as spiders, millipedes, centipedes, and earthworms, as well.
Some insectivores specialize in catching and feeding upon flying insects, sometimes called aeroplankton. Examples of this type include dragonflies, smaller species of bats, flycatchers, swallows, and swifts. Insectivores that feed on flying insects must be quick and manoeuvrable fliers, and must have acute means of detecting their prey. Most species are visual predators, meaning they detect flying insects by sight. Bats, however, feed in darkness at night or dusk, and they locate their prey using echolocation, a type of biological sonar.
Insectivorous Plants
Although they are not necessarily part of the animal kingdom, insectivorous plants play an important role in maintaining the population of insects. These plants are highly adapted to their reliance on animals as a food source by the use of a variety of mechanisms to secure their prey, such as pitfalls, sticky surfaces, hair-trigger snaps, bladder-snaps, entangling furriness, and lobster-pot traps. Also known as carnivorous plants, they appear adapted to grow in places where the soil is thin or poor in nutrients.
However, animals are not these plants main source of energy, no matter how critical of a source of important minerals. Insectivorous plants, like many other plants, generally gain their source of energy from photosynthesis.
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Scavengers are animals that consume dead organisms that have died from causes other than predation. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding behaviour. Scavengers play an important role in the ecosystem by consuming dead animals and plants.
Scavengers aid in overcoming fluctuations of food resources in the environment. The process and rate of scavenging is affected by both biotic and biotic factors, such as carcass size, habitat, temperature, and seasons.
Types of Scavengers
Obligate scavenging is rare among vertebrates, due to the difficulty of finding enough carrion without expending too much energy.
Well-known invertebrate scavengers of animal material include burying beetles and blowflies, which are obligate scavengers, and yellowjackets. Fly larvae are also common scavengers for organic materials at the bottom of freshwater bodies. For example, Tokunagayusurika akamusi is a species of midge fly whose larvae live as obligate scavengers at the bottom of lakes and whose adults almost never feed and only live up to a few weeks.
Most scavenging animals are facultative scavengers that gain most of their food through other methods, especially predation. Many large carnivores that hunt regularly, such as hyenas and jackals, but also animals rarely thought of as scavengers, such as African lions, leopards, and wolves will scavenge if given the chance. They may also use their size and ferocity to intimidate the original hunters (the cheetah is a notable victim, rather than a perpetrator). Almost all scavengers above insect size are predators and will hunt if not enough carrion is available, as few ecosystems provide enough dead animals year-round to keep its scavengers fed on that alone. Scavenging wild dogs and crows frequently exploit roadkill.
Scavengers of dead plant material include termites that build nests in grasslands and then collect dead plant material for consumption within the nest. The interaction between scavenging animals and humans is seen today most commonly in suburban settings with animals such as opossums, polecats and raccoons. In some African towns and villages, scavenging from hyenas is also common.
Impact on the Environment
Scavengers play a fundamental role in the environment through the removal of decaying organisms, serving as a natural sanitation service. While microscopic and invertebrate decomposers break down dead organisms into simple organic matter which are used by nearby autotrophs, scavengers help conserve energy and nutrients obtained from carrion within the upper trophic levels, and are able to disperse the energy and nutrients farther away from the site of the carrion than decomposers.
Scavenging unites animals which normally would not come into contact, and results in the formation of highly structured and complex communities which engage in non-random interactions. Scavenging communities function in the redistribution of energy obtained from carcasses and reducing diseases associated with decomposition. Oftentimes, scavenger communities differ in consistency due to carcass size and carcass types, as well as by seasonal effects as consequence of differing invertebrate and microbial activity.
Competition for carrion results in the inclusion or exclusion of certain scavengers from access to carrion, shaping the scavenger community. When carrion decomposes at a slower rate during cooler seasons, competitions between scavengers decrease, while the number of scavenger species present increases.
Transmission of Disease
Scavenging may provide a direct and indirect method for transmitting disease between animals. Scavengers of infected carcasses may become hosts for certain pathogens and consequently vectors of disease themselves. An example of this phenomenon is the increased transmission of tuberculosis observed when scavengers engage in eating infected carcasses. Likewise, the ingestion of bat carcasses infected with rabies by striped skunks resulted in increased infection of these organisms with the virus.
A major vector of transmission of diseases are various bird species, with outbreak being influenced by such carrier birds and their environment. An avian cholera outbreak from 2006 to 2007 off the coast Newfoundland, Canada resulted in the mortality of many marine bird species. The transmission, perpetuation and spread of the outbreak was mainly restricted to gull species who scavenge for food in the area. Similarly, an increase of transmission of avian influenza virus to chickens by domestic ducks from Indonesian farms permitted to scavenge surrounding areas was observed in 2007. The scavenging of ducks in rice paddy fields in particular resulted in increased contact with other bird species feeding on leftover rice, which may have contributed to increased infection and transmission of the avian influenza virus. The domestic ducks may not have demonstrated symptoms of infection themselves, though were observed to excrete high concentrations of the avian influenza virus.
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Herbivore, Carnivore, Scavenger, Insectivore
An Omnivore is an organism that regularly consumes a variety of material, including plants, animals, algae, and fungi. They range in size from tiny insects like ants to large creatures-like people.
Because they have an easier time finding food, omnivores are sometimes better at adapting to new environments than creatures with more specific feeding habits. Omnivores can better adapt to development than herbivores or carnivores.
Animals that hunt other animals are known as predators, while those that are hunted are known as prey. Since omnivores hunt and are hunted, they can be considered both predators and prey. They can also be scavengers, animals that feed on the remains of dead animals.
Definition and Related Terms
An omnivore is an organism that can feed on both plant and animal sources. Carnivores are animals that feed only on other animals. Herbivores feed exclusively on plant material. An omnivore can feed on both sources.
Although a species as a whole may be omnivores, not all members of the species must be omnivores. Across the human species, while many are omnivorous just as many are vegan and partake in no animal products. In this case, humans are physiologically omnivorous, in that it is possible for them to obtain nutrients from both sources. However, many people are behaviourally herbivorous, and choose not to eat animal products because they can derive all the nutrients they need without animal products. One theory of human evolution suggests that our ancestors were mainly herbivorous, switching to become omnivores when tools and fire aided in the capture and edibility of animals.
Diverse Diet
Omnivores have evolved various traits to help them eat both plants and animals. Many omnivores have a mixture of sharp teeth (for ripping through muscle tissue) and flat molars (for grinding plant matter). However, some omnivores like Chickens, have no teeth and swallow their food whole.
An omnivore has the liberty of getting their meal from a large variety of food sources, such as from plants, and meat. They have the ability to incorporate food sources such as algae, fungi, and bacteria into their diet.
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Herbivore, Omnivore, Scavenger
A carnivore is an animal that eats primarily meat, or animal tissue, through hunting or scavenging. Typically, a carnivore is considered to be at the top of the food chain, not preyed upon by other animals, and is termed an apex predator.
Carnivores are sometimes characterized by their type of prey. For example, animals that eat mainly insects and similar invertebrates are called insectivores, while those that eat mainly fish are called piscivores. The first tetrapods, or land-dwelling vertebrates, were piscivorous amphibians known as labyrinthodonts. They gave rise to insectivorous vertebrates and, later, to predators of other tetrapods.
Carnivores may alternatively be classified according to the percentage of meat in their diet. The diet of a hypercarnivore consists of more than 70% meat, that of a mesocarnivore 30–70%, and that of a hypocarnivore less than 30%, with the balance consisting of non-animal foods such as fruits, other plant material, or fungi.
Carnivores in the Food Chain
For a healthy ecosystem it is important that the population of autotrophs, herbivores, and carnivores remain in balance. Carnivores depend on herbivores and other animals to survive. Zebras and Gazelles once travelled in great herds over the plains of Africa. But these herds have shrunk and are now mostly confined to parks and wildlife reserves. As the number of these herbivores decline, carnivores such as African Wild Dogs, which prey on them, also decline. Scientists estimate that only 3,00 to 5,500 African Wild Dogs remain in the wild.
In some places the disappearance of large carnivores has led to an overpopulation of herbivores, disrupting the ecosystem. Wolves and Cougars are traditional predators of White-Tailed Deer, for instance. But the hunting and development have eliminated these predators from the north-eastern United States. Without natural predators, the population of White-Tailed Deer has skyrocketed. In some cases, there are so many deer that they cannot find enough food. They frequently stray into towns and suburbs in search of food.
The Carnivorous Diet
Certain types of carnivores have specific diets. Some, such as Sea Lions, eat mainly fish. They are called piscivores.
Others, such as lizards, eat mainly insects. They are called insectivores. Many bats are also insectivores. One little brown bat can eat a thousand mosquitoes in an hour. Some insects are themselves insectivores. These include ladybugs, dragonflies, and praying mantises.
Carnivores that have been known to attack and eat human beings are known as man-eaters. Some species of sharks, alligators, and bears are called man-eaters. However, no carnivore specifically hunts human beings or relies on them as a regular food source.
Cannibals are carnivores that eat the meat of members of their own species. Many carnivores practice cannibalism. For some species, cannibalism is a way of eliminating competitors for food, mates, or other resources. Chimpanzees or Bears, for example, will hunt and consume the young of family members, sometimes their own offspring. Praying mantis females will kill and eat the bodies of their mates.
Many carnivores are scavengers, creatures that eat the meat of dead animals, or carrion. Unlike other types of carnivores, scavengers usually do not hunt the animals they eat. Some, such as vultures, consume animals that have died from natural causes. Others, such as hyenas, will snatch meat hunted by other carnivores. Many insects, such as flies and beetles, are scavengers.
Some carnivores, including sea lions, feed often. Others, such as king cobras, can go months between meals.
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A herbivore is an organism that feeds mostly on plants. Herbivores range in size from tiny insects such as aphids to large, lumbering elephants. Many herbivores spend a large part of their life eating. For example Elephants need to eat about 130kg (300lbs) of food a day. It takes a long time to eat that much leaves and grass, so elephants sometimes eat for 18 hours a day.
As a result of their plant diet, herbivorous animals typically have mouthparts adapted to rasping or grinding. Horses and other herbivores have wide flat teeth that are adapted to grinding grass, tree bark, and other tough plant material.
A large percentage of herbivores have mutualistic gut flora that help them digest plant matter, which is more difficult to digest than animal prey. This flora is made up of cellulose-digesting protozoans or bacteria.
Definition and Related Terms
Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in general are known as primary consumers. Herbivory is usually limited to animals that eat plants. Fungi, bacteria, and protists that feed on living plants are usually termed plant pathogens (plant diseases), while fungi and microbes that feed on dead plants are described as saprotrophs. Flowering plants that obtain nutrition from other living plants are usually termed parasitic plants.
Picky Eaters
Some herbivores eat any plant matter they can find. Elephants, for example, eat bark, leaves, small branches, roots, grasses, and fruit. Black Rhinoceroses also eat a variety of fruits, branches, and leaves.
Other herbivores eat only one part of a plant. An animal that specializes in eating fruit is called a frugivore. Oilbirds, which live in northern South America, are frugivores. They eat nothing but the fruit of palms and laurels. The Koala, which is native to Australia, eats little besides the leaves of eucalyptus trees. An animal that eats the leaves and shoots of trees is called a folivore. Pandas, which feed almost exclusively on bamboo, are folivores. Termites are insects that feed mostly on wood. Wood-eaters are called xylophages.
Many insects are herbivores. Some, such as Grasshoppers, will eat every part of a plant. Others specialize in certain parts of the plant. Caterpillars eat leaves. The larvae, or young wormlike forms, of root weevils feed on roots. Asian long-horned beetles tunnel deep into the heart of a tree and eat the wood there. Honeybees feed on nectar and pollen from flowers.
Some herbivores consume only dead plant material. These organisms are called detritivores. Detritivores also consume other dead organic material, such as decaying animals, fungi, and algae. Detritivores such as earthworms, bacteria, and fungi are an important part of the food chain. They break down the dead organic material and recycle nutrients back into the ecosystem. Detritivores can survive in many places. Earthworms and mushrooms live in the soil. There are also detritivore bacteria at the bottom of the ocean.
Plants that are parasites can still be considered herbivores. A parasite is an organism that lives on or in another organism and gets its nutrients from it. Parasitic plants get their nutrients from other plants, called host plants. Dodder, native to tropical and temperate climates around the world, is a parasitic vine that wraps around a host plant. Dodder has rootlike parts called haustoria that attach to the host plant, so it can feed on its nutrients. Eventually, the parasitic dodder feeds on all the nutrients of the host plant, and the host plant dies. The dodder vines then move on to another plant.
Herbivores in the Food Chain
Many herbivores spend a large part of their life eating. Elephants need to eat about 130 kilograms (300 pounds) of food a day. It takes a long time to eat that much leaves and grass, so elephants sometimes eat for 18 hours a day.
Herbivores depend on plants for their survival. If the plant population declines, herbivores cannot get enough food. Beavers, for example, feed on trees and plants that live near water. If the trees are removed to build houses and roads, the beaver population cannot survive.
Similarly, many carnivores need herbivores to survive. Herbivorous zebras and gazelles once travelled in great herds across the savannas of Africa. But these herds have shrunk and are now mostly confined to parks and wildlife reserves. As the number of these herbivores declines, carnivores such as African wild dogs, which prey on them, also decline. Scientists estimate that only 3,000 to 5,500 African wild dogs remain in the wild.
In some places, the disappearance of large carnivores has led to an overpopulation of herbivores. Wolves and cougars are traditional predators, or hunters, of white-tailed deer, which are herbivores. Hunting and expanding human settlements have practically eliminated these predators from the north-eastern United States. Without its natural predators, the population of white-tailed deer has skyrocketed. In some areas, there are so many deer that they cannot find enough food. They now frequently stray into towns and suburbs in search of food.
These Teeth are made for Chomping
Many herbivores have large, dull, flat teeth. These teeth are excellent for chewing and breaking down tough plant material. Carnivores have sharp, narrow teeth that are better for biting and tearing flesh.
However, some herbivores also have strong, sharp teeth. These teeth, such as those on Hippopotamuses and Gorillas, are not adapted for eating. They are developed for confrontations with other animals fighting, not feeding.
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