The maximum attainable body size of herbivorous mammals: morphophysiological constraints on foregut, and adaptations of hindgut fermenters

  title={The maximum attainable body size of herbivorous mammals: morphophysiological constraints on foregut, and adaptations of hindgut fermenters},
  author={Marcus Clauss and R Frey and B Kiefer and Matthias Lechner-Doll and Werner C. Loehlein and C Polster and Gertrud E. R{\"o}ssner and Wolf Juergen Streich},
An oft-cited nutritional advantage of large body size is that larger animals have lower relative energy requirements and that, due to their increased gastrointestinal tract (GIT) capacity, they achieve longer ingesta passage rates, which allows them to use forage of lower quality. However, the fermentation of plant material cannot be optimized endlessly; there is a time when plant fibre is totally fermented, and another when energy losses due to methanogenic bacteria become punitive. Therefore… 

The digestive performance of mammalian herbivores: why big may not be that much better

Quantitative research on these mechanisms is warranted in order to evaluate whether an increase in body size represents a net increase of digestive efficiency or just a shift of digestive focus.

Evolutionary adaptations of ruminants and their potential relevance for modern production systems.

Comparative physiology applies methods established in domestic animal science to a wider variety of species. This can lead to improved insight into evolutionary adaptations of domestic animals, by

Ecology, Evolution and Behaviour of Wild Cattle: The digestive system of ruminants, and peculiarities of (wild) cattle

Functional ruminants – the phylogenetic ruminant as well as the camelids – combine simple foregut fermentation with peculiar sorting mechanisms that assure that larger digesta particles are regurgitated and re-masticated (ruminated).

Review: Comparative methane production in mammalian herbivores.

It is concluded that still unidentified host-specific factors other than digesta retention characteristics, or the presence of rumination or a foregut, influence CH4 production, possibly pointing towards variation in microbiota functionality.

The Morphophysiological Adaptations of Browsing and Grazing Mammals

This chapter first reviews the actual state of knowledge on those properties of browse and grass that appear relevant for the ingestive and digestive process, and then deduct hypotheses as to how one would assume that browsers and grazers differ due to these characteristics.

Dinosaur Energetics: Setting the Bounds on Feasible Physiologies and Ecologies

  • A. Clarke
  • Environmental Science, Biology
    The American Naturalist
  • 2013
Quantitative analysis of dinosaur energetics shows that many features of dinosaur lifestyle are compatible with a physiology similar to that of extant lizards, scaled up to dinosaur body masses and temperatures.

Testing predictions on body mass and gut contents: dissection of an African elephant Loxodonta africana Blumenbach 1797

Data on the individual gut segments of a captive African elephant that was euthanased because of a positive serological tuberculosis test, but that was clinically healthy, did not show a reduced appetite, and ingested food up to the time of euthanasia contradicts the notion that elephants have comparatively less capacious gastrointestinal tracts.

The potential interplay of posture, digestive anatomy, density of ingesta and gravity in mammalian herbivores: why sloths do not rest upside down

The sitting resting posture of sloths could be an adaptation to exploit the tendency of the forestomach conents to stratify in order to pass larger, more difficult-to-digest particles faster from the fermentation chamber.

No evidence for directional evolution of body mass in herbivorous theropod dinosaurs

This work reconstructs body mass in the three major subclades of non-avian theropod dinosaurs whose ecomorphology is correlated with extrinsic evidence of at least facultative herbivory in the fossil record, and suggests that the hypothesis can be extrapolated to herbivorous lineages across geological time scales.

Faecal particle size: digestive physiology meets herbivore diversity.

  • M. ClaussP. Steuer J. Hummel
  • Medicine, Biology
    Comparative biochemistry and physiology. Part A, Molecular & integrative physiology
  • 2015



Modelling the nutritional ecology of ungulate herbivores: evolution of body size and competitive interactions

It is suggested that the upper limit to ungulate body size is determined by the ability to extract nutrients from feeding niches during the nadir of the seasonal cycle of resource quality and abundance.

Scaling of digestive efficiency with body mass in Neotoma

It is clear from the analysis that body mass is of critical importance in influencing fibre fermentation, actual ecological or evolutionary implications are more difficult to assess.

Feeding ecology and the evolution of body size of baboons

It is argued that male size is constrained by competition with ruminant species who are more efficient at digesting the types of foods required of greater male size, and female size is viewed as reduced below that of the male to absorb the energetic costs of lactation.

Speculations about the diet and digestive physiology of herbivorous dinosaurs

  • J. Farlow
  • Environmental Science
  • 1987
Large herbivorous dinosaurs probably fed on plants whose allelochemical defenses were geared more toward reducing digestibility than attacking the herbivore's metabolism directly, obviating the need for a foregut fermentation chamber and permitting these large herbivores to take advantage of the energetic benefits of hindg gut fermentation for digestion of low-quality fodder.

A Nutritional Explanation for Body-Size Patterns of Ruminant and Nonruminant Herbivores

Calculations suggest that sufficient intake of a high-fiber diet cannot be maintained to provide the energy necessary to support larger body sizes, and changing body size is postulated as a mechanism for differentiating the feeding requirements of herbivores.

A Model of Dietary Fiber Utilization by Small Mammalian Herbivores, with Empirical Results for Neotoma

A model of plant fiber utilization tailored specifically for hindgut fermenters indicates that small mammals can obtain significant benefit from fiber fermentation, especially at moderate fiber levels, andisons with literature data are in general agreement.

Allometry and Ecology of Feeding Behavior and Digestive Capacity in Herbivores : A Review

  • J. Van
  • Environmental Science
  • 2005
The purpose of this review is to give some perspective of the factors that influence feeding behaviors and the ability of herbivores to adapt to diets. The most important of these are digestibility,


A synthesis of diet information for all 78 species of extant African Bovidae (excluding goats and sheep), based on an extensive survey of the literature, found some degree of correspondence between taxonomic groupings and dietary strategies.

Optimal body size and an animal's diet

  • T. Case
  • Environmental Science
    Acta biotheoretica
  • 1979
A simple optimization model is developed here which considers food search, capture, and eating rates and the metabolic cost of these activities for animals of different sizes and produces an optimum intermediate body size which increases with food quality and decreases with increases in consumer metabolic rate and “prey” speed.

The functional significance of the browser-grazer dichotomy in African ruminants

There is little difference in digestive strategy between African ruminants with different morphological adaptations of the gut, after controlling for the effects of body mass.