Mammalian dietary ecology (technical session at 74th SVP meeeting) (original) (raw)
Dietary Characterization of Terrestrial Mammals
Understanding the feeding behaviour of the species that make up any ecosystem is essential for designing further research. Mammals have been studied intensively, but the criteria used for classifying their diets are far from being standardized. We built a database summarizing the dietary preferences of terrestrial mammals using published data regarding their stomach contents. We performed multivariate analyses in order to set up a standardized classification scheme. Ideally, food consumption percentages should be used instead of qualitative classifications. However, when highly detailed information is not available we propose classifying animals based on their main feeding resources. They should be classified as generalists when none of the feeding resources constitute over 50% of the diet. The term 'omnivore' should be avoided because it does not communicate all the complexity inherent to food choice. Moreover, the so-called omnivore diets actually involve several distinctive adaptations. Our dataset shows that terrestrial mammals are generally highly specialized and that some degree of food mixing may even be required for most species.
Estonian Journal of Ecology, 2009
Describing species' ecological strategies enables us to condense ecological information and to express it in evolutionary terms. However, the process of categorizing species is hampered by methodological difficulties and insufficient development of the typology and nomenclature of different strategies. In this article an approach for overcoming these difficulties is proposed. For a precise description of mammalian substrate utilization, it is better to combine two characteristics rather than use only one. The categorization should reflect: (1) the media or substrates primarily used for foraging; and (2) the media or substrates primarily used for sleeping. The numerous substrate utilization strategies of mammals fall into five broad groups: (1) aquatic and semiaquatic; (2) subterranean; (3) terrestrial and subterranean-terrestrial; (4) arboreal and semiarboreal; and (5) aerial and semiaerial. Three main mammalian feeding strategies are proposed: animalivorous, frugivorous, and herbivorous. An example of ecological classification of mammals in terms of substrate utilization and feeding strategy is provided.
Oikos, 2014
A central goal of nutritional ecology is to understand how variation in food quality limits the persistence of wild animal populations. Habitat suitability for browsing mammals is strongly aff ected by concentrations of nutrients and plant secondary metabolites (PSMs), but our understanding of this is based mostly on short-term experiments of diet selection involving captive animals. In the wild, browsers forage in biologically, chemically and spatially-complex environments, and foraging decisions in response to varying food quality will be correspondingly complicated. We have identifi ed four steps that must be achieved in order to translate our understanding from laboratory experiments to populations of mammalian browsers: 1) knowing what foods and how much of these wild browsers eat, as well as what they avoid eating; 2) knowing the relevant aspects of plant nutritional and defensive chemistry to measure in a given system and how to measure them; 3) understanding the spatial distribution of nutrients and PSMs in plant communities, the costs they impose on foraging and the eff ects on animals ' distributions; and 4) having appropriate statistical tools to analyse the data. We discuss prospects for each of these prerequisites for extending laboratory studies of nutritional quality, and review recent developments that may off er solutions for fi eld studies. We also provide a synthesis of how to use this nutritional knowledge to link food quality to population regulation in wild mammals and describe examples that have successfully achieved this aim.
PLOS ONE, 2020
The critically endangered Amargosa vole (Microtus californicus scirpensis) is found only in rare marsh habitat near Tecopa, California in a plant community dominated by three-square bulrush (Schoenoplectus americanus). Since the earliest research on the Amargosa vole, the existing paradigm has been that these voles are obligatorily dependent on bulrush as their only food source and for the three-dimensional canopy and litter structure it provides for predator avoidance. However, no prior research has confirmed the diet of the Amargosa vole. In this study we characterized the Amargosa vole' nutritional needs, analyzed the quality of bulrush by forage analysis, and performed microhistological and metabarcoding analyses of vole feces to determine what foods were consumed in the wild. All bulrush plant tissues analyzed were low in fat (from 0.9% of dry matter in roots to 3.6% in seeds), high in neutral detergent fiber (from 5.9% in rhizomes to 33.6% in seeds), and low in protein (7.3-8.4%). These findings support the conclusion that bulrush alone is unlikely to support vole survival and reproduction. Fecal microhistology and DNA metabarcoding revealed relatively diverse diets including plants in 14 families, with rushes (Juncaceae), bulrushes (Cyperaceae), and grasses (Poaceae) being the most common diet items. On microhistology, all analyzed samples contained bulrush, sedges (Carex sp.), rushes (Juncus sp.), and beaked spikerush (Eleocharis rostrellata) even from marshes where non-bulrush plants were uncommon. There was evidence of insects at <1% in two marshes but none in the remaining marshes. Metabarcoding detected ten genera of plants. When considering non-Schoenoplectus targets, for which metabarcoding had poor sensitivity, saltgrass (Distichlis spicata) was the most commonly detected species, with prominent contributions from seaside arrowgrass (Triglochin concinna) and yerba mansa (Anemopsis californica) as well. Diversity of vole diets generally increased with increasing site plant diversity, but differences were not statistically significant. Confirming details about dietary behaviors is critical for informing
Diet differentiation between European arvicoline and murine rodents
Acta Theriologica, 2011
Small European muroid rodents are generally divided into species which feed on seeds and/or invertebrates and species which feed on green plant material; however, there is considerable plasticity in feeding behavior among species. Here, we analyze diets of 14 low-latitude rodent species from Western Europe based on published studies. The 77 studies were submitted to principal component analysis in order to compare diet plasticity within and between the 14 species. We observed variations in food composition of arvicoline and murine rodents which are associated with differences in morphology and habitat use. Most arvicoline rodents eat mainly green matter of the herbaceous layers of open habitats whereas most murine species are able to use a greater diversity of high energetic plant tissues from denser habitats, where they can exploit the different vegetation layers. Despite its phylogenetic position among arvicoline rodents, the bank vole (Myodes glareolus) shows morpho-physiological and ecological traits which tend to be more similar to murine species. These intermediate evolutionary characters seem consistent with the fact that bank voles are able to exploit a wide spectrum of trophic resources from low energetic lignified tissues to high calorific invertebrate prey. This results in a very diverse diet, which is intermediate between true herbivorous arvicolines and typical seed-and invertebrate-eating murine species. More investigations on genetic affiliation and ecological driving forces will help understand this intermediate position of bank vole diet, and further investigations among other arvicoline species will help determine if bank voles and other Myodes species are unique.
1999
A quarter of a century ago, Freeland andJanzen (1"97a) attempted to put many years of observations of the toxicity of plant secondary metabolites (PSM) into an evolutionary framework to predict what impact these compounds would have on diet selection and nutritional ecology of mammals. Although many ecologists had discussed the evolutionary impact of PSM on insect herbivores (e.9., Fraenkel, 1959), there had been little consideration of the different effects of PSM on mammalian herbivores and no general predictions of how animals should forage when PSM occurred in potential diet items. There was, however, a rich collection of pharmacological and toxicological data, and observations of animal poisoning mediated by PSM. Accordingly, Freeland andJanzen's (J.974) paper was highly influential and their framework for understanding how PSM should affect mammalian foraging remains the dominant paradigm today.
A New Method of Determining Diets of Rodents
Journal of Mammalogy, 1998
Diets of rodents often have been studied by analysis of feces or stomach contents. Analysis of feces is highly inaccurate because of differential digestion, and the analysis of stomach contents requires the sacrifice of large numbers of individuals and cannot be used for some species because of conservation considerations. We developed a new method for detennining diets of rodents by stomach pumping that is as accurate as previously used analysis of stomach contents. Animals are not sacrificed, so it is possible to collect more than one sample from each individual and study a population of rodents for a long time without harming it. It also allows studies that would otherwise be legally or morally impossible.
Mammal Review, 2018
1. Diet is a key trait of an organism’s life history that influences a broad spectrum of ecological and evolutionary processes. Kissling et al. (2014; Ecology and Evolution 4: 2913–2930) compiled a species-specific data set of diet preferences of mammals for 38% of a total of 5364 terrestrial mammalian species assessed for the International Union for Conservation of Nature’s Red List, to facilitate future studies. The authors imputed dietary data for the remaining 62% by using extrapolation from phylogenetic relatives. 2. We collected dietary information for 1261 mammalian species for which data were extrapolated by Kissling et al. (2014), in order to evaluate the success with which such extrapolation can predict true diets. 3. The extrapolation method devised by Kissling et al. (2014) performed well for broad dietary categories (consumers of plants and animals). However, the method performed inconsistently, and sometimes poorly, for finer dietary categories, varying in accuracy in both dietary categories and mammalian orders. 4. The results of the extrapolation performance serve as a cautionary tale. Given the large variation in extrapolation performance, we recommend a more conservative approach for inferring mammalian diets, whereby dietary extrapolation is implemented only when there is a high degree of phylogenetic conservatism for dietary traits. Phylogenetic comparative methods can be used to detect and measure phylogenetic signal in diet. If data for species are needed, then only the broadest feeding categories should be used. This would ensure a greater level of accuracy and provide a more robust data set for further ecological and evolutionary analysis.
Comparative Animal Nutrition and Metabolism - Peter Robert Cheeke, Ellen S. Dierenfeld
The capybara, the world's largest rodent, is native to the floodplains of the northern parts of South America. It is a nonruminant herbivore with cecal fermentation. • proteins; • carbohydrates; • lipids; • minerals; • vitamins; and • water. Water is considered to be a nutrient, although for domestic animals it does not totally fit the definition of a nutrient because it is not generally required in the diet (food) but is usually consumed separately as drinking water. Some desert animals (e.g. pack rat) never drink, but survive on metabolic water (see Chapter 20). Marine mammals (e.g. seals, sea lions) never drink, but obtain their water from their diet (fish tissue), while fruit-eating animals (frugivores) obtain a major portion of their water from the diet (fruit). Thus water is truly a nutrient for these species. A brief description of each of these major nutrient categories will be given for introductory purposes; they will be discussed in detail in later chapters. Proteins Proteins are large molecules composed of amino acids joined together by peptide bonds (see Chapter 4). Plant and animal proteins are composed of about 20 amino acids, arranged in various sequences to form specific proteins. A few other amino acids (e.g. citrulline) do not occur in protein tissue but have other specific functions, and are known as non-protein amino acids. Over 300 individual amino acids are known; most of them are non-protein amino acids in plant tissue, with no role in animal nutrition (except a negative one if they are toxic). Some sources indicate even greater numbers of known amino acids in plants, as high as over 900 (Wink, 1997). The genetic control of protein synthesis involving DNA and RNA metabolism is one of the marvels of life. Each cell (except non-avian erythrocytes) contains a genetic code, programming the cell to synthesize particular proteins. Proteins are an integral part of animal structure and metabolism. They constitute a major part of the body structure, as components of muscle, connective tissue and cell membranes. All metabolic reactions are dependent on proteinaceous enzymes. A major concern of animal nutritionists is the provision of adequate dietary protein and amino acids. From a comparative standpoint, there are great differences in protein utilization, with ruminant animals largely insulated from specific dietary amino acid requirements because of the activities of rumen microbes, whereas carnivores have some distinct differences from omnivores in amino acid needs. All amino acids contain nitrogen; therefore, all proteins contain nitrogen. Protein utilization by animals is often studied by measuring nitrogen in nitrogen balance trials. Protein digestibility, for example, is determined by measuring the nitrogen content of feed and faeces to determine the amount of absorbed (hence digested) nitrogen, reflective of amino acid absorption. In general, proteins contain about 16% nitrogen. The protein content of feeds is usually measured by determining the nitrogen content and multiplying it by the factor of 6.25. Crude protein is defined as N × 6.25 (16 g of nitrogen (N) come from 100 g protein; therefore, 1 g of nitrogen is associated with 100/16 = 6.25 g of protein). Nitrogen is measured by the Kjeldahl procedure, which is named after the Danish chemist who developed it. The feed sample is boiled in concentrated sulfuric acid, resulting in the complete oxidation of all organic material. The proteins and amino acids are completely degraded; their nitrogen is released as ammonium ion (). The solution is then made alkaline, converting to ammonia (NH 3). Steam is passed through the solution (steam distillation), driving off the NH 3 , which is trapped in a boric acid solution. The concentration of NH 3 is measured by titration. It is important to recognize that the crude protein procedure measures nitrogen. Thus, it does not distinguish between high-quality and poorquality protein, or protein and non-protein nitrogen. 1 Carbohydrates Besides containing carbon, carbohydrates (CH 2 O) n contain hydrogen and oxygen in the proportions found in water; hence the name (hydrates of carbon). Carbohydrates are the basic energy source of almost all animal life. They are produced as the end products of photosynthesis by green plant tissue. Photosynthesis is a very complicated process, but in simple terms, consists of the reduction (gain of hydrogen) of carbon dioxide in plants to dietary supplements are unproven scientifically, and their use is promoted by anecdotal 'evidence'. Lack of scientific proof is a reflection of a lack of financial incentive for research support, because most herbal products are not patentable. The problem with 'anecdotal evidence' is that it is often due to the placebo effect (Kienzle et al., 2006). The only acceptable proof is a double-blind study (in which neither the investigator nor the subject knows the identity of which subjects are on which treatment). Subjective types of responses, particularly in equine studies, are also a problem. With dressage horses, for example, the responses are the evaluations of the rider, such as unresponsiveness or stiff back, horse 'too hot', and so on. The more subjective the criteria, the more likely that the rider's imagination comes into play (Kienzle et al., 2006). Animal Cellular Metabolism Enzymes and hormones Enzymes and hormones have important roles in regulation of metabolism. Some general comments of an introductory nature will be made here, and specific roles of various enzymes and hormones will be discussed later as appropriate. Enzymes are organic catalysts. Catalysts are substances that accelerate chemical reactions. They undergo chemical changes during the reaction, but revert to their original state when the reaction is completed, and can be reused. Virtually every chemical reaction that takes place in living tissues requires an enzyme catalyst. With some exceptions (e.g. drug metabolizing enzymes), enzymes are very substrate-specific, having an active site that is very specific in its binding capabilities. All enzymes are proteins. Enzymes can be extracted from tissues and purified, and utilized in research, medicine and for industrial purposes. Enzymes have traditionally been named for the substrate upon which they act, with the addition of the ending 'ase'. Some of the enzymes encountered in nutrition, such as trypsin, chymotrypsin, pepsin and rhodanese, were named before a unifying system of nomenclature was developed. The current system includes information on the type of chemical reaction catalysed and cofactors required. For example, oxidoreductases catalyse oxidationreduction reactions, transferases catalyse transfer of a group (e.g. glutathione-Stransferase), hydrolases act to hydrolyse ester bonds, isomerases catalyse interconversions of isomers (e.g. trans-vitamin A to cis-vitamin A), etc. Essential cofactors, such as nicotinamide adenine dinucleotide (NAD) and NAD phosphate (NADP), are included in the name. The result can be some real tongue-twisters, such as UDP-Nacetylglucosamine:dolicholphosphate N-acetylglucosamine phosphate transferase! This enzyme is essential for formation of glycoproteins, and is inhibited by the mycotoxins responsible for annual ryegrass toxicity of sheep. Cofactors associate reversibly with enzymes or substrates; they are often metal ions. Enzymes that require a metal ion cofactor are called metal-activated enzymes, in contrast to metalloenzymes that contain a metal ion as a prosthetic group. Copper, iron and zinc frequently function as cofactors. Organic cofactors are called coenzymes. Coenzymes act as reusable shuttles that can transport substrates from their point of generation to their point of utilization. Several B-vitamins function as constituents of coenzymes, including pantothenic acid (coenzyme A, CoA), niacin (NAD, NADP), riboflavin (flavin mononucleotide, FMN; flavin adenine dinucleotide, FAD), thiamin, folic acid and vitamin B 12. Many coenzymes are derivatives of adenosine monophosphate (e.g. CoA, NAD, NADP, FAD). The distribution of enzymes in living tissues is highly ordered, with enzymes located so that the product(s) of one enzymatic reaction are substrates for the next reaction. They are compartmentalized in subcellular fractions; the enzymes of glycolysis, for example, are in the cell cytosol while the citric acid cycle enzymes are in the mitochondria. Enzymes have an 'active site' or 'catalytic site' where the interactions between enzyme, substrate and coenzymes occur. Many enzymes are produced and secreted as proenzymes or zymogens, which must be activated to the active enzyme form. This process is physiologically necessary in many cases, such as when the enzyme is needed intermittently, but when it is needed, it is needed immediately. Prothrombin is a proenzyme in the blood; when blood clotting is required, prothrombin is activated to the enzyme thrombin. Pepsinogen is secreted from the gastric mucosa, and activated by hydrochloric acid (HCl) in the stomach to pepsin. Other proteolytic enzymes are secreted as zymogens (e.g. trypsinogen, chymotrypsinogen). It would be physiologically difficult for a cell to store an active proteolytic enzyme without digesting itself. Many enzymes require metal ions for their activity. Metalloenzymes contain a mineral as an integral part of their structure, while metal-activated enzymes require the presence of a less tightly bound mineral (cofactors). There are many zinc and copper metalloenzymes, such as thymidine kinase (Zn) and cytochrome oxidase (Cu). The activity of enzymes is regulated in various ways in order to direct metabolic activity to maintain homeostasis. Homeostasis refers to the constancy of the internal environment, whereby cellular metabolism is regulated to attempt to maintain a steady-state condition. An example is blood glucose. Homeostatic hormones such as insulin and glucagon function to maintain a fairly constant...
Revisiting the dietary niche: When is a mammalian herbivore a specialist?
Integrative and Comparative Biology, 2009
Synopsis Understanding dietary specialization in herbivores has theoretical and practical implications in ecology, yet defining niche breadth consistently has been problematic. To increase clarity and communication among ecologists and among disciplines (i.e., chemists, pharmacologists), we propose a specialization key for mammalian herbivores that assigns ''obligatory'' and ''facultative'' modifiers to the terms ''specialist'' and ''generalist''. These modifiers are assigned based on (1) relative breadth of the animal's realized niche and diet (what it eats), (2) relative breadth of the fundamental niche and available diet (what it could eat), (3) the extent of chemical or physical characteristics, termed ''difficulty'', that make food items either low in value or unpalatable to most herbivores, and (4) relevant temporal and spatial scales at which diets and niche breadth were measured. Obligatory specialists always have a narrow realized niche consisting of difficult food items, and morphological adaptations and/or the loss of redundant behavioral flexibility that effectively limit their fundamental niches, precluding them from expanding their diet under changed environmental conditions. Facultative specialists have a consistently narrow realized niche for difficult foods during at least one spatial or temporal scale, but have a broad enough fundamental niche to allow them to expand their diet to include less difficult foods when environmental conditions allow. Facultative generalists have the broadest fundamental niche, allowing them to consume a wide variety of foods. However, they may occasionally demonstrate a narrow realized niche, focused on less difficult plants than is the case with specialists. Finally, the obligatory generalists always have a wide realized niche because of a relatively narrow fundamental niche, precluding them from eating much of any difficult plant. We summarize hypothesized characteristics of mammalian herbivores in each of the four categories of specialization. We demonstrate the need for further work on defining the realized and fundamental niches, comparing among herbivores across categories conducted under similar conditions, and understanding the nature of trade-offs required for specialization and generalization for both community and phylogenetically based analyses.
Ecology of Vertebrate Nutrition
eLS, 2001
Vertebrate nutritional ecology is the study of the interrelationships between food resources in the environment and the consumptive use of these food resources by vertebrate animals. Consumptive use includes how vertebrate animals procure, digest, absorb and metabolise available foods in the environment to satisfy their requirements for health, growth and reproduction. The challenge for wild vertebrates is to satisfy their nutritional requirements in an environment that often varies in food availability and quality. Vertebrate animals have evolved a diverse and interesting suite of solutions to the problem(s) of acquiring necessary nutrients and energy in a world where food often does not want to be eaten.
Rapid Communications in Mass Spectrometry
RATIONALE Ecologists increasingly determine the δ 15 N values of amino acids (AA) in animal tissue; "source" AA typically exhibit minor variation between diet and consumer, while "trophic" AA have increased δ 15 N values in consumers. Thus, trophic-source δ 15 N offsets (i.e., Δ 15 NT-S) reflect trophic position in a food web. However, even minor variation in δ 15 Nsource AA values may influence the magnitude of offset that represents a trophic step, known as the trophic discrimination factor (i.e., TDFT-S). Diet digestibility and protein content can influence the δ 15 N values of bulk animal tissue, but the effects on AA Δ 15 NT-S and TDFT-S in mammals are unknown. METHODS We fed captive mice (Mus musculus) either (A) a low-fat, high-fiber diet with low, intermediate, or high protein; or (B) a high-fat, low-fiber diet with low or intermediate protein. Mouse muscle and dietary protein were analyzed for bulk tissue δ 15 N using elemental analyzer-isotope ratio mass spectrometry (EA-IRMS), and were also hydrolyzed into free AA that were analyzed for δ 15 N using EA-IRMS. RESULTS As dietary protein increased, Δ 15 NConsumer-Diet slightly declined for bulk muscle tissue in both experiments, increased for AA in the low-fat, high-fiber diet (A), and remained the same or decreased for AA in the high-fat, low-fiber diet (B). The effects of dietary protein on 15 NT-S and on TDFT-S varied by AA but were consistent between variables. CONCLUSIONS Diets were less digestible and included more protein in Experiment A than in Experiment B. As a result, the mice in Experiment A probably oxidized more AA, resulting in greater Δ 15 NConsumer-Diet values. However, the similar responses of 15 NT-S and of TDFT-S to diet variation suggest that if diet samples are available, 15 NT-S accurately tracks trophic position. If diet samples are not available, the patterns presented here provide a basis to interpret 15 NT-S values The trophic-source offset of Pro-Lys did not vary across diets, and therefore may be more reliable for omnivores than other offsets (e.g., Glu-Phe).
Diet breadth of mammalian herbivores: nutrient versus detoxification constraints
Oecologia, 2000
Two hypotheses, nutrient constraints and detoxification limitation, have been proposed to explain the lack of specialists among mammalian herbivores. The nutrient constraint hypothesis proposes that dietary specialization in mammalian herbivores is rare because no one plant can provide all requisite nutrients. The detoxification limitation hypothesis suggests that the mammalian detoxification system is incapable of detoxifying high doses of similar secondary compounds present in a diet of a single plant species. We experimentally tested these hypotheses by comparing the performance of specialist and generalist woodrats (Neotoma) on a variety of dietary challenges. Neotoma stephensi is a narrow dietary specialist with a single species, one-seeded juniper, Juniperus monosperma, comprising 85–95% of its diet. Compared with other plants available in the habitat, juniper is low in nitrogen and high in fiber, phenolics, and monoterpenes. The generalist woodrat, N. albigula, also consumes one-seeded juniper, but to a lesser degree. The nutrient constraint hypothesis was examined by feeding both species of woodrats a low-nitrogen, high-fiber diet similar to that found in juniper. We found no differences in body mass change, or apparent digestibility of dry matter or nitrogen between the two species of woodrats after 35 days on this diet. Moreover, both species were in positive nitrogen balance. We tested the detoxification limitation hypothesis by comparing the performance of the generalist and specialist on diets with and without juniper leaves, the preferred foliage of the specialist, as well as on diets with and without α-pinene, the predominant monoterpene in juniper. We found that on the juniper diet, compared with the specialist, the generalist consumed less juniper and lost more mass. Urine pH, a general indicator of overall detoxification processes, declined in both groups on the juniper diet. The generalist consumed half the toxin load of the specialist yet its urine pH was slightly lower. Moreover, the generalist consumed significantly less of the treatment with high concentrations of α-pinene compared to the control treatment, while the specialist consumed the same amount of food regardless of α-pinene concentration. For both groups, urine pH declined as levels of α-pinene in the diet increased. The generalist produced a significantly more acidic urine than the specialist on the treatment with the highest α-pinene concentration. Our results suggest that in this system, specialists detoxify plant secondary compounds differently than generalists and plant secondary compounds may be more important than low nutrient levels in maintaining dietary diversity in generalist herbivores.
A comparison and critique of different scat-analysis methods for determining carnivore diet
Mammal Review, 2011
1. For terrestrial carnivores, scat analysis is the technique most often used to determine diets. Various methods of interpreting scat-analysis data exist; however, little is known about how the choice of method affects the results. 2. We reviewed 50 scat-analysis papers to assess the range of methods currently used. Furthermore, we used a large data set from cape fox Vulpes chama and black-backed jackal Canis mesomelas scats to compare 11 scat-analysis methods. Techniques tested included five biomass calculation methods, four frequency of occurrence methods, one method that estimated volume in scats, and another that estimated mass of food items in scats. 3. Frequency of occurrence methods were used in 94% of reviewed papers, and in 50% of papers they were the sole methods used. However, we conclude that frequency of occurrence has the least ecological significance and results can be misleading. Although biomass calculations probably provide the best approximation to true diets, only 23% of reviewed papers used suitable biomass calculation methods when models were available for the study species. 4. Analysis of fox and jackal scats showed that there were significant differences among methods when calculating percent diet composition and niche breadth. Additionally, dietary overlap between species differed considerably among the methods (range of R0 = 0.29-0.79). We conclude that the choice of method can have a significant impact on the results of dietary analysis, and can lead to very different conclusions about a species' ecology. 5. The best approximation of the true diet can be obtained by using a biomass calculation model that was developed for the same species, or for a closely related species with a similar food spectrum. When no such model is available, either the volume or mass of diet components in the scats should be used. To document rare food items, frequency of occurrence data could also be given.
Average daily metabolic rate of rodents: habitat and dietary comparisons
Functional Ecology, 1998
Average daily metabolic rate (ADMR), the metabolizable energy intake required by a caged animal to maintain constant body energy content, includes the basal metabolic rate (BMR) and the heat increment of feeding for maintenance (HIF m ). Therefore, when an animal is in energy balance, ADMR can be expressed as:
Recent advances in primate nutritional ecology
Nutritional ecology seeks to explain, in an ecological and evolutionary context, how individuals choose, acquire, and process food to satisfy their nutritional requirements. Historically, studies of primate feeding ecology have focused on characterizing diets in terms of the botanical composition of the plants consumed. Further, dietary studies have demonstrated how patch and food choice in relation to time spent foraging and feeding are influenced by the spatial and temporal distribution of resources and by social factors such as feeding competition, dominance, or partner preferences. From a nutritional perspective, several theories including energy and protein-to-fiber maximization, nutrient mixing, and toxin avoidance, have been proposed to explain the food choices of non-human primates. However, more recently, analytical frameworks such as nutritional geometry have been incorporated into primatology to explore, using a multivariate approach, the synergistic effects of multiple nutrients, secondary metabolites, and energy requirements on primate food choice. Dietary strategies associated with nutrient balancing highlight the tradeoffs that primates face in bypassing or selecting particular feeding sites and food items. In this Special Issue, the authors bring together a set of studies focusing on the nutritional ecology of a diverse set of primate taxa characterized by marked differences in dietary emphasis. The authors present, compare, and discuss the diversity of strategies used by primates in diet selection, and how species differences in ecology, physiology, anatomy, and phylogeny can affect patterns of nutrient choice and nutrient balancing. The use of a nutritionally explicit analytical framework is fundamental to identify the nutritional requirements of different individuals of a given species, and through its application, direct conservation efforts can be applied to regenerate and protect specific foods and food patches that offer the opportunity of a nutritionally balanced diet.