Digestive rate model

Last updated

The digestive rate model (DRM) [1] (of foraging) is related to optimal foraging theory in that the model describes the diet selection that animals should perform in order to maximize the energy (or nutrients) available to them. It differs from the main body of Optimal Foraging Theory in stating that animals can select food in order to make optimal use of their digestive tract (maximize digestion rate) rather than the maximization of the food ingestion rate, which is the base of Optimal foraging theory.

Foraging Searching for wild food resources

Foraging is searching for wild food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce. Foraging theory is a branch of behavioral ecology that studies the foraging behavior of animals in response to the environment where the animal lives.

Optimal foraging theory

Optimal foraging theory (OFT) is a behavioral ecology model that helps predict how an animal behaves when searching for food. Although obtaining food provides the animal with energy, searching for and capturing the food require both energy and time. To maximize fitness, an animal adopts a foraging strategy that provides the most benefit (energy) for the lowest cost, maximizing the net energy gained. OFT helps predict the best strategy that an animal can use to achieve this goal.

A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excreted by cells to create non-cellular structures, such as hair, scales, feathers, or exoskeletons. Some nutrients can be metabolically converted to smaller molecules in the process of releasing energy, such as for carbohydrates, lipids, proteins, and fermentation products, leading to end-products of water and carbon dioxide. All organisms require water. Essential nutrients for animals are the energy sources, some of the amino acids that are combined to create proteins, a subset of fatty acids, vitamins and certain minerals. Plants require more diverse minerals absorbed through roots, plus carbon dioxide and oxygen absorbed through leaves. Fungi live on dead or living organic matter and meet nutrient needs from their host.

The basic tenet of the DRM is that the intake of energy by an animal passes through two consecutive processes, food ingestion or foraging, and food digestion. Optimal foraging theory describes the diet selection if the food ingestion rate is the limiting factor. The DRM describes diet selection and foraging behavior if digestion is the rate limiting process. Food can consist of varying fractions of largely indigestible parts such as fibre in plant material, shells of molluscs or insect chitin, which can be thought of as 'rate limiting' for the digestion process or somewhat more intuitively as 'bulk' that takes up capacity that can be spent better for material with a higher digestibility.

Ingestion is the consumption of a substance by an organism. In animals, it normally accomplished by taking in the substance through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms, ingestion can take place through taking the substance through the cell membrane.

A limiting factor is a variable of a system that, if subject to a small change, causes a non-negligible change in an output or other measure of the system. A factor not limiting over a certain domain of starting conditions may yet be limiting over another domain of starting conditions, including that of the factor.

Chitin long-chain polymer of a N-acetylglucosamine

Chitin (C8H13O5N)n ( KY-tin), a long-chain polymer of N-acetylglucosamine, is a derivative of glucose. It is a primary component of cell walls in fungi, the exoskeletons of arthropods, such as crustaceans and insects, the radulae of molluscs, cephalopod beaks, and the scales of fish and lissamphibians. The structure of chitin is comparable to another polysaccharide—cellulose, forming crystalline nanofibrils or whiskers. In terms of function, it may be compared to the protein keratin. Chitin has proved useful for several medicinal, industrial and biotechnological purposes.

The original description of the model positioned the DRM as an alternative to the contingency model (CM) of optimal foraging and pointed out that some of the predictions of the DRM provide a better match than did the CM with observed diet choice and behavior of e.g. herbivores. The DRM went largely unnoticed, but a recent paper by Van Gils [2] describes how red knots Calidris canutus forage based on digestive bottlenecks and confirmed their foraging according to the DRM rather than the CM model of optimal foraging. The case is particularly interesting as a major difference in individual foraging behavior is related to a large intraspecific difference in the digestive tract of the knots.

See also

Behavioral ecology Study of the evolutionary basis for animal behavior due to ecological pressures

Behavioral ecology, also spelled behavioural ecology, is the study of the evolutionary basis for animal behavior due to ecological pressures. Behavioral ecology emerged from ethology after Niko Tinbergen outlined four questions to address when studying animal behaviors that are the proximate causes, ontogeny, survival value, and phylogeny of behavior.

Human behavioral ecology (HBE) or human evolutionary ecology applies the principles of evolutionary theory and optimization to the study of human behavioral and cultural diversity. HBE examines the adaptive design of traits, behaviors, and life histories of humans in an ecological context. One aim of modern human behavioral ecology is to determine how ecological and social factors influence and shape behavioral flexibility within and between human populations. Among other things, HBE attempts to explain variation in human behavior as adaptive solutions to the competing life-history demands of growth, development, reproduction, parental care, and mate acquisition.

Related Research Articles

Herbivore Animal adapted to eating plant material

A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. 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.

DRM may refer to:

Red knot species of bird

The red knot is a medium-sized shorebird which breeds in tundra and the Arctic Cordillera in the far north of Canada, Europe, and Russia. It is a large member of the Calidris sandpipers, second only to the great knot. Six subspecies are recognised.

Information foraging is a theory that applies the ideas from optimal foraging theory to understand how human users search for information. The theory is based on the assumption that, when searching for information, humans use "built-in" foraging mechanisms that evolved to help our animal ancestors find food. Importantly, better understanding of human search behaviour can improve the usability of websites or any other user interface.

Cud is a portion of food that returns from a ruminant's stomach to the mouth to be chewed for the second time. More accurately, it is a bolus of semi-degraded food regurgitated from the reticulorumen of a ruminant. Cud is produced during the physical digestive process of rumination. The idiomatic expression chewing one's cud means meditating or pondering; similar expressions such as "he chewed that over for a bit", or "chew on that!" likely have the same derivation.

The marginal value theorem (MVT) is an optimality model that usually describes the behavior of an optimally foraging individual in a system where resources are located in discrete patches separated by areas with no resources. Due to the resource-free space, animals must spend time traveling between patches. The MVT can also be applied to other situations in which organisms face diminishing returns.

Phenotypic plasticity the ability of an organism to change its phenotype in response to the environment

Phenotypic plasticity refers to some of the changes in an organism's behavior, morphology and physiology in response to a unique environment. Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompasses all types of environmentally induced changes that may or may not be permanent throughout an individual's lifespan. The term was originally used to describe developmental effects on morphological characters, but is now more broadly used to describe all phenotypic responses to environmental change, such as acclimation (acclimatization), as well as learning. The special case when differences in environment induce discrete phenotypes is termed polyphenism.

Life history theory is an analytical framework designed to study the diversity of life history strategies used by different organisms throughout the world, as well as the causes and results of the variation in their life cycles. It is a theory of biological evolution that seeks to explain aspects of organisms' anatomy and behavior by reference to the way that their life histories—including their reproductive development and behaviors, life span and post-reproductive behavior—have been shaped by natural selection. A life history strategy is the "age- and stage-specific patterns" and timing of events that make up an organism's life, such as birth, weaning, maturation, death, etc. These events, notably juvenile development, age of sexual maturity, first reproduction, number of offspring and level of parental investment, senescence and death, depend on the physical and ecological environment of the organism.

In ecology, an ideal free distribution is a way in which animals distribute themselves among several patches of resources. The theory states that the number of individual animals that will aggregate in various patches is proportional to the amount of resources available in each. For example, if patch A contains twice as many resources as patch B, there will be twice as many individuals foraging in patch A as in patch B. The ideal free distribution (IFD) theory predicts that the distribution of animals among patches will minimize resource competition and maximize fitness.

Prey switching is frequency-dependent predation, where the predator preferentially consumes the most common type of prey. The phenomenon has also been described as apostatic selection, however the two terms are generally used to describe different parts of the same phenomenon. Apostatic selection has been used by authors looking at the differences between different genetic morphs. In comparison, prey switching has been used when describing the choice between different species.

Collective animal behavior Coordinated behavior of large groups of similar animals

Collective animal behavior is a form of social behavior involving the coordinated behavior of large groups of similar animals as well as emergent properties of these groups. This can include the costs and benefits of group membership, the transfer of information across the group, the group decision-making process, and group locomotion and synchronization. Studying the principles of collective animal behavior has relevance to human engineering problems through the philosophy of biomimetics. For instance, determining the rules by which an individual animal navigates relative to its neighbors in a group can lead to advances in the deployment and control of groups of swimming or flying micro-robots such as UAVs.

Octopus aquaculture

The development of octopus aquaculture, the farming of octopus, is being driven by strong market demands in the Mediterranean and in South American and Asian countries. Octopus live short lives, growing rapidly and maturing early. They typically reach two or three kilograms. There is little overlap between successive generations.

Hindgut fermentation is a digestive process seen in monogastric herbivores, animals with a simple, single-chambered stomach. Cellulose is digested with the aid of symbiotic bacteria. The microbial fermentation occurs in the digestive organs that follow the small intestine: the large intestine and cecum. Examples of hindgut fermenters include proboscideans and large odd-toed ungulates such as horses and rhinos, as well as small animals such as rodents, rabbits and koalas. In contrast, foregut fermentation is the form of cellulose digestion seen in ruminants such as cattle which have a four-chambered stomach, as well as in sloths, macropodids, some monkeys, and one bird, the hoatzin.

In biology, optimality models are a tool used to evaluate the costs and benefits of different organismal features, traits, and characteristics, including behavior, in the natural world. This evaluation allows researchers to make predictions about an organisms's optimal behavior or other aspects of its phenotype. Optimality modeling is the modeling aspect of optimization theory. It allows for the calculation and visualization of the costs and benefits that influence the outcome of a decision, and contributes to an understanding of adaptations. The approach based on optimality models in biology is sometimes called optimality theory.

Dr John D. Goss-Custard is a British behavioural ecologist; he was one of the first scientists to carry out field work on foraging behaviour making use of optimising models, specifically the optimal diet model. After completing a BSc degree in Zoology at the University of Bristol, he moved to the University of Aberdeen to carry out research for a PhD degree, which he was awarded in 1966. The University of Aberdeen awarded him its DSc degree in 1987.

Evolutionary biologists have developed various theoretical models to explain the evolution of food-sharing behavior—"the unresisted transfer of food from one food-motivated individual to another"—among humans and other animals.

Jarman-Bell principle A concept in ecology

The Jarman-Bell principle, coined by P.J Jarman (1968.) and R.H.V Bell (1971), is a concept in ecology offering a link between a herbivore's diet and their overall size. It operates by observing the allometric properties of herbivores. According to the Jarman-Bell principle, the food quality of a herbivore's intake decreases as the size of the herbivore increases, but the amount of such food increases to counteract the low quality foods.

References

  1. ↑ Verlinden, C.; Wiley, R. H. (1989). "The constraints of digestive rate: An alternative model of diet selection". Evolutionary Ecology. 3 (3): 264. doi:10.1007/BF02270727.
  2. ↑ Van Gils, J. N. A.; Rooij, S. M. R. D.; Van Belle, J.; Van Der Meer, J.; Dekinga, A.; Piersma, T.; Drent, R. (2004). "Digestive bottleneck affects foraging decisions in red knots Calidris canutus. I. Prey choice" (PDF). Journal of Animal Ecology. 74: 105. doi:10.1111/j.1365-2656.2004.00903.x.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.