Jarman–Bell principle
[6] Their small gut limits the amount of space for food, so they eat low quantities of high quality diet.
[3][11] Furthermore, the Jarman–Bell principle is also important by providing evidence for the ecological framework of "resource partitioning, competition, habitat use and species packing in environments"[3] and has been applied in several studies.
[14][15] When food is passed through the digestive system (including multiple stomach chambers), it breaks down further through symbiotic microbes[14][16] at fermentation site(s).
[8] The development of the rumen not only allows a site for fermentation but also decrease the food digestion (increase retention time).
The metabolic rate per unit of body mass of large animals is slow enough to subside on a consistent flow of low-quality food.
[6] Larger sized animals have a larger/longer digestive tract, allowing for more quantities of low quality food to be processed (retention time).
[8] However, there are also reports of larger animals, including primates and horses (under dietary restrictions), practicing coprophagy.
Through the extra flexibility of subsisting on low-quality food, the Jarman–Bell Principle suggests an evolutionary advantage of larger animals and hence provides evidence for Cope's rule.
[9] This discrepancy could be due to ecological factors which apply pressure and encourage an adaptive approach to the given environment, rather than taking on an optimal form of digestive physiology.
Clauss et al.[10] suggests that this is due to the diverse adaptations that support the rumen such that the digestive efficiency of ruminants remain consistent and independent of body size and food intake.
[10] In addition to providing evidence for ecological frameworks such as "resource partitioning, competition, habitat use and species packing in environment" and Cope's rule,[3][11] the Jarman–Bell Principle has been applied to model primate behaviours and explain sexual segregation in ungulates.
[7] This extra time influences behaviour and, over a group of ungulates, lead to segregation via food quality.
[7] Since males are larger and can handle low quality food, their feeding and ruminating activity will differ from females.
[7] Pérez-Barbería F. J., et al. (2008) tested the proposed hypothesis by feeding Soay sheep grass hay and observing the digestive efficiency between both sexes via their faecal output.
[7] Although this result is consistent with the Jarman–Bell principle in that it observes the relationship between size and food quality, it does not adequately explain the proposed hypotheses.
[7] For hypothesis (2), there are many external factors which may influence behavioural changes in males, enough to induce sexual segregation, that are not explored in Pérez-Barbería F. J, et al.
[7] By observing effective food digestibility in Soay sheep, the Jarman–Bell principle seems to apply at an intraspecific level.
[1] It can also be used to hypothesis the general diet of newly discovered/mysterious primates that have not been researched by taking into account the animal's body size.
[1] Steven J. C. Gaulin examined 102 primate species (from various scientific literature) for links between size and diet, and hence the Jarman–Bell principle.
Steven J. C. Gaulin notes that, when the principle is applied to offer any type of explanation, it is subjected to numerous other phenomena that occur at the same time.
[1] For example, the habitat range constrains the size of an organism; large primates are too heavy to live on tree tops.
Method two involves drawing ideas from extant animals and how their body mass is linked with their diet.
[9] However, the lack of particle reduction mechanisms (e.g. gastric mills, chewing teeth) challenges this expectation.
[9] Therefore, an enlarged gut cavity allows increased intake, and thus shorter retention time similar to other herbivorous reptiles.
[23] During this time period, herbivorous plant matter such as conifers, ginkgos, cycads, ferns and horsetails may have been the dietary choice of sauropods.
[24] Clauss Hummel et al. (2005), cited in D. M. Wilkinson and G. D. Ruxton's paper,[24] argues that larger sizes does not necessarily improve digestive efficiency.
Since gut volume scales linearly with body mass, larger animals have more capacity to digests food.
