Estimation of Dry-Matter Intake in Wild Herbivores

Storr, G. M.

doi:10.1038/197307b0

Cited by 31 publications

(5 citation statements)

References 2 publications

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“…Animals can be fed foods 'labelled' with an indigestible marker (radioactive isotopes, e,g., Mautz and Petrides 1971; cotton thread, e.g., Campling et al 1961) to measure rate of appearance of the marker in feces. Another method is to sacrifice a set of animals, who have had food provided ad libitum, and measure changes in digestive organ contents over a period of time (Storr 1963). Both techniques were used in my studies.…”

Section: Constraint Equation 1) Digestive Capacity Digestive Ca-mentioning

confidence: 99%

Optimal foraging and community structure: implications for a guild of generalist grassland herbivores

1986

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A particular linear programming model is constructed to predict the diets of each of 14 species of generalist herbivores at the National Bison Range, Montana. The herbivores have body masses ranging over seven orders of magnitude and belonging to two major taxa: insects and mammals. The linear programming model has three feeding constraints: digestive capacity, feeding time and energy requirements. A foraging strategy that maximizes daily energy intake agrees very well with the observed diets. Body size appears to be an underlying determinant of the foraging parameters leading to diet selection. Species that possess digestive capacity and feeding time constraints which approach each other in magnitude have the most generalized diets. The degree that the linear programming models change their diet predictions with a given percent change in parameter values (sensitivity) may reflect the observed ability of the species to vary their diets. In particular, the species which show the most diet variability are those whose diets tend to be balanced between monocots and dicots. The community-ecological parameters of herbivore body-size ranges and species number can possibly be related to foraging behavior.

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Section: Constraint Equation 1) Digestive Capacity Digestive Ca-mentioning

confidence: 99%

Optimal foraging and community structure: implications for a guild of generalist grassland herbivores

1986

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“…of feces (Croker 1959;Dusi 1949;Hegg 1961;Hercus 1960;Kiley 1966;Stewart 1967;Storr 1961Storr , 1963Storr , 1964Storr , 1968Ward 1969;Williams 1969).…”

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Estimating Dryweights of Foodplants in Feces of Herbivores

Free¹,

Hansen²,

Sims³

1970

Journal of Range Management

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The dry weight composition of foodplants was estimated by a microscope technique for esophageal samples from steers, fecal samples of steers and fecal samples from sheep fed on the esophageal samples. Perennial species of foodplants forming more than 5% of the diets could be identified and quantified by the analysis of 100 microscope fields at 125 power magnification. The diagnostic features of fragile forbs were not as prominent in feces as they are in non-digested plants. Knowing what foodplants an animal eats was once a worthwhile research objective but now it is essential to also study "when" and "how much"

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“…The observed proportion of monocot and dicot in the diet of each of the 109 individuals was determined from the mean of five fecal pellets collected from each individual at its last capture prior to foraging observations (Ritchie 1988). Diet proportions were measured using microhistological techniques (Storr 1963;Sparks and Malechek 1968). These proportions were weighted by the relative dry-matter digestibilities of the two food types to account for their differential appearance in feces (Smith and Shandruk 1979).…”

Section: Deviation From An Optimal Dietmentioning

confidence: 99%

Optimal foraging and fitness in Columbian ground squirrels

Ritchie

1990

Oecologia

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Optimal diets were determined for each of 109 individual Columbian ground squirrels (Spermophitus coiumbianus) at two sites in northwestern Montana. Body mass, daily activity time, and vegetation consumption rates for individuals were measured in the field, along with the average water content of vegetation at each ground squirrel colony. I also measured stomach and caecal capacity and turnover rate of plant food through the digestive tract for individuals in the laboratory to construct regressions of digestive capacity as a function of individual body mass. Finally, I obtained literature estimates of average daily energy requirements as a function of body mass and digestible energy content of vegetation. These data were used to construct a linear programming diet model for each individual. The model for each individual was used to predict the proportion of two food types (monocots and dicots) that maximized daily energy intake, given time and digestive constraints on foraging. Individuals were classified as "optimal" or "deviating", depending on whether their observed diet was significantly different from their predicted optimal diet. I determined the consequences of selecting an optimal diet for energy intake and fitness. As expected, daily energy intake calculated for deviators (based on their observed diet proportion) was less than that for optimal foragers. Deviating foragers do not appear to compensate for their lower calculated energy intake through other factors such as body size or physiological efficiency of processing food. Growth rate, yearly survivorship, and litter size increase with calculated energy intake, and optimal foragers have six times the reproductive success of deviators by age three. Optimal foraging behavior, therefore, appears to confer a considerable fitness advantage.

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Estimation of Dry-Matter Intake in Wild Herbivores

Cited by 31 publications

References 2 publications

Optimal foraging and community structure: implications for a guild of generalist grassland herbivores

Optimal foraging and community structure: implications for a guild of generalist grassland herbivores

Estimating Dryweights of Foodplants in Feces of Herbivores

Optimal foraging and fitness in Columbian ground squirrels

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