Geometry of nutrition in field studies: an illustration using wild primates

Abstract

Nutritional geometry has shown the benefits of viewing nutrition in a multidimensional context, in which foraging is viewed as a process of balancing the intake and use of multiple nutrients. New insights into nutrient regulation have been generated in studies performed in a laboratory context, where accurate measures of amounts (e.g. eaten, converted to body mass, excreted) can be made and analysed using amounts-based nutritional geometry. In most field situations, however, proportional compositions (e.g. of foods, diets, faeces) are the only measures readily available, and in some cases are more relevant to the problem at hand. For this reason, a complementary geometric method was recently introduced for analysing multi-dimensional data on proportional compositions in nutritional studies, called the right-angled mixture triangle (RMT). We use literature data from field studies of primates to demonstrate how the RMT can provide insight into a variety of important concepts in nutritional ecology. We first compare the compositions of foods, using as an example primate milks collected in both the wild and the laboratory. We next compare the diets of different species of primates from the same habitat and of the same species (mountain gorillas) from two distinct forests. Subsequently, we model the relationships between the composition of gorilla diets in these two habitats and the foods that comprise these diets, showing how such analyses can provide evidence for active nutrient-specific regulation in a field context. We provide a framework to relate concepts developed in laboratory studies with field-based studies of nutrition.

The effects of plant nutritional chemistry on food selection of Mexican black howler monkeys (Alouatta pigra): The role of lipids

“…However, it has been recognized for some time [Hladik, 1977b;Garber et al, 2015;Gaulin & Gaulin, 1982] that dietary profiles obtained using traditional methods of feeding time and assumptions concerning the nutritional content of fruits, leaves, and flowers, offer a less precise understanding of primate feeding ecology compared to new analytical frameworks that focus on feeding rates, an estimation of daily amounts of each food type ingested, the calculation of daily nutrient and energy intake, and questions of nutrient prioritization and nutrient balancing [Felton et al, 2009;Simpson & Raubenheimer, 2012;Raubenheimer et al, 2015]. In addition, re-examining and rethinking primate feeding ecology requires that we assess available protein rather than crude protein in the plant parts consumed, calculate food selectivity indices based on measures of food availability rather than on plant species abundance, and identify nutrient prioritization patterns.…”

Nutritional Ecology and Human Health

“…It is not our intention to expound in detail upon those studies here (for a recent review, see 86) except to say that they illustrate how, by placing appetite at the center of nutritional models, nutritional geometry can go a long way toward identifying the combinations of factors that animals integrate to optimize the process of foraging. In particular, the questions of how appetites for different nutrients interact and how these interactions engage with the food environment to generate different patterns of nutrient intake have emerged as especially powerful guides for understanding animal nutrition, both in the laboratory and the wild (67,86).…”

The Multidimensional Stoichiometric Niche

“…Importantly, these nutritional and metabolic requirements can often be expressed in only a few well-established dimensions, potentially resolving some of the ambiguity in selecting traits. In particular, isotopic ecology (Layman et al, 2007;Newsome et al, 2007;Jackson et al, 2011;Cucherousset and Villéger, 2015;Swanson et al, 2015), the geometric framework of nutrition (Simpson and Raubenheimer, 1993;Raubenheimer and Simpson, 2004;Raubenheimer et al, 2009Raubenheimer et al, , 2015Kearney et al, 2010;Raubenheimer, 2011), and ecological stoichiometry (Elser et al, 2000;Peñuelas et al, 2008Peñuelas et al, , 2010 have all represented the ecological niche using the chemistry of living organisms.…”

“…Like traditional traits, isotopic traits can be fit with a convex hull, the size of which has been extensively used as a proxy of the size of the trophic niche occupied by a group of individuals (Layman et al, 2007(Layman et al, , 2012Cucherousset and Villéger, 2015). Similarly, the geometric framework of nutrition (NGF) has been used to build multidimensional models of animal macronutrient budgets (i.e., multidimensional nutritional niche) in which information on food macronutrient contents (i.e., proteins, carbohydrates, lipids), animal macronutrient requirements, and animal nutritional processes such as macronutrient intake, growth and macronutrient use, are integrated, modeled and visualized as three macronutrient axes (Raubenheimer et al, 2015;Machovsky-Capuska et al, 2016. Although this approach has been extremely useful to improve our understanding of the foraging behavior, post-ingestion allocation of macronutrients, and the dietary niche breath of a large diversity of animals, it is a data hungry approach and some of the required nutritional descriptors are restricted to specific taxonomic groups-such as animals but not plants.…”