Spatial impacts and the characterisation of resource use in a heterogeneous landscape.

Highly spatially variable environments pose animals with diet selection decisions that need to account for the patchy nature of their resource. Improved rangeland management would result from being able to predict patterns of animal utilisation of such vegetation. Whilst progress is being made in the comprehension of large scale influences (e.g., location of drinking water, landscape topography), little is known about how these integrate with smaller scales. It is likely that animals view landscapes in differing ways, depending on the scale that processes operate. Identification of the appropriate scale at which a species is affected by the spatial heterogeneity of a resource requires characterisation of the resource spatial structure, independent of our own biases. We tend to view landscapes in terms of vegetation communities, whilst the appropriate unit for animal perception remains unclear. This poster describes a study of foraging behaviour carried out as a method by which to associate animal activity with space use as an independent estimate of spatial heterogeneity

Snout Shape in Extant Ruminants

Copyright: © 2014 Tennant, MacLeod. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. [4.0 license]. The attached file is the published version of the article

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

The allometric relationships for the fermentation rate of dry matter, the total energy concentration of volatile fatty acids (VFAs), the energy supplied from VFA production and the mass of the digesta contents within the rumen or caecum and proximal colon (hindgut) were used to test whether the digestive strategies of grazing and browsing African ruminants differ. The wet and dry mass of the contents of the rumen and hindgut were allometrically related to body mass (BM). These relationships did not differ between browsing and grazing ruminants. The fermentation rates in the rumen were strongly allometric and the intercepts of the relationships did not differ between browsers and grazers. The fermentation rates in the hindgut were not allometrically related to BM and did not differ between ruminants with different feeding habits. Likewise, the total energy concentration of the VFAs in the rumen and hindgut showed no allometric scaling and did not differ between browsing and grazing ruminants. The energy supplied by VFA production in both the rumen and hindgut of African ruminants scaled at around 0.8 with BM. Only in the case of the energy supplied by VFAs in the rumen were there significantly different intercepts for browsing and grazing ruminants. The energy supplied by VFA production in the rumen was inadequate to meet the energy requirements for maintenance of browsers and small grazers. The retention time of digesta in the alimentary tract was positively related to BM although there was no difference in the allometric relationships for grazers and browsers. The results of these analyses suggest that, after controlling for the effects of body mass, there is little difference in digestive strategy between African ruminants with different morphological adaptations of the gut

The nutritional ecology of African ruminants: A reinterpretation

1. Two contrasting explanations of niche separation in ruminants emphasize the importance of body mass-related trends in energy requirements and food-processing ability (the diet-quality assumption) and of physiological adaptations to diet type (grass or browse; the diet-type assumption).\ud \ud 2. The quality of the diet consumed in the dry season by 21 species of African ruminants was estimated from observed fermentation rates in the rumens of culled animals using a simulation model of digesta kinetics. The model predicts the effect of food composition (including tannins) on a number of variables on which previous arguments about physiological adaptations have been based: cellulolytic activity, digestion kinetics and volatile fatty acid proportions.\ud \ud 3. The predicted diet quality (potential digestibility) varied from 0.90 in small animals to 0.75 in large ones, and was negatively related to body mass with a shallow allometric exponent(- 0.035 +/- 0.0109).\ud \ud 4. The allometric exponent scaling body mass to predicted energy assimilation rate was 0.852+/-0.0474. The abundance and quality of food available were apparently adequate to allow greater net energy intake, relative to requirements, by large animals than small ones.\ud \ud 5. No difference existed in the predicted potential digestibility or net energy yield from the diet of browsing and grazing species after controlling for body mass. Therefore, although the diets differed in their botanical and chemical composition, the end result had little effect on the nutritional ecology of the animals with different diet types.\ud \ud 6. The model predicted that the level of cellulolytic activity of microbes in the rumen can affect the energy obtained from the diet. Microbial adaptation would cause browsers to suffer a penalty on switching from browse to grass, thereby reinforcing diet choice.\ud \ud 7. The presence of tannins in the diets of browsers was predicted to decrease rumen fermentation rate and increase the digestibility of the diet required to match observed fermentation rates

Interatheriidae (Typotheria; Notoungulata), body size and paleoecology characterization

Size has a major influence on animal’s adaptation to its environment and is central to paleobiological characterization of fossil mammals. We present new models of body mass estimation for the Interatheriidae (Notoungulata, Typotheria). This small herbivorous mammals extends from the late Paleocene to the late Miocene and they are very well represented in the paleontological record of southern South America during a geological time lapse that witnessed extremely important events, at both climatic and biotic levels. The importance of the group as paleoecological indicators for a great part of the Cenozoic is emphasized by their long biochron and abundance in the fossil record. In this context, estimation of the body mass becomes crucial to reconstruct and infer ecologicalenvironmental structure for a given time period. The results of the calculation of body masses from these new equations shows overall narrower range, smaller deviations, lower de-transformation correction and lower prediction error than previous equations used for body mass estimation in herbivores ungulates, establishing the maximum body mass for the Interatheriidae in 8.3 kg. These new body masses were utilized for characterization of the nutritional ecology of Protypotherium australe (early Miocene), suggesting browser habits but it does not exclude grass from been part of the diet.Fil: Scarano, Alejo Carlos. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Carlini, Alfredo Armando. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universitat Zurich; SuizaFil: Illius, Andrew W.. University of Edinburgh; Reino Unid

Phylogenetic analysis of stomach adaptation in digestive strategies in African ruminants

The stomach morphology of 28 species of artiodactyls that differ in feeding style (browser, mixed feeder, grazer) was analysed using a multivariate approach and phylogenetic correction in order to test whether stomach morphology was correlated with feeding style when body mass was controlled for. A total of 25 morphological traits of the stomach were used in the analysis. After the effects of body mass and phylogeny on stomach morphology were taken into account, there was no significant grouping of species according to feeding style. When information about the feeding style of each species was included in the analysis, the set of morphological traits separated the mixed feeders from the other two feeding styles, but grazers and browsers had similar morphological features. Most of the variance in stomach morphology was explained by body mass and a lesser proportion by phylogeny. The main morphological features that have previously been proposed as being adaptations in grazing species, namely, lengthening of the retention time of ingesta to achieve an increase in their fibre digestion capability by means of a larger relative stomach capacity, a greater subdivision of chambers and smaller openings, are not supported by the findings of this study. Thus, there is no consistent evidence to support a significant adaptive effect of stomach morphology to different diets in the Artiodactyla