Table 1.
Habitat characteristics, sample size, average daily energy and protein intakes, and ratio of available protein to non-protein energy (fat, carbohydrate and NDF) for five sifaka groups at Tsinjoarivo, Madagascar.
Table 2.
Linear Mixed Model results for 10 daily intake variables for five sifaka groups at Tsinjoarivo, Madagascar; data are individual lemurs’ average scores within each of 12 data collection periods (n = 152).
Table 3.
Seasonal variation in the daily energy and nutrient intakes (mean±SD) of diademed sifakas at Tsinjoarivo, Madagascar, scaled to metabolic body mass and body mass, respectively.
Fig 1.
Foraging and intake variables for five sifaka groups across five seasons at Tsinjoarivo, Madagascar.
The lean season is indicated by grey shading, error bars represent standard error.
Table 4.
Relative contribution of macronutrients to daily dietary intakes for five sifaka groups at Tsinjoarivo, Madagascar.
Fig 2.
Macronutrient balancing in sifaka groups across seasons at Tsinjoarivo, Madagascar.
Right-angle mixture triangle (RMT) plots showing the proportional contribution of protein, fat and carbohydrates to macronutrient-derived energy intakes for five sifaka groups at Tsinjoarivo, Madagascar across five seasons (1, 4 and 5 represent the lean season). Fat and protein are represented on the y- and x-axes, respectively, and carbohydrate is represented by an implicit axis Z. For clarity, each plot has two “isolines” representing 60% and 80% carbohydrates, shown with dotted lines.
Fig 3.
Seasonality in the contribution of protein to the diet in sifaka groups at Tsinjoarivo, Madagascar.
Bivariate plots showing absolute seasonal averages (daily intakes ± SE) of protein (x-axis) and non-protein energy (fat + carbohydrate + NDF; y-axis), both expressed in kJ, for five sifaka groups at Tsinjoarivo, Madagascar. The fit line represents a linear regression forced through the origin as a visual approximation of each group’s nutritional rail (with grey dashed lines indicating rails for groups in the other panel). The shaded area represents nutritional space (i) left of a vertical line representing estimated minimum protein requirement of 2.8 g●BMkg-1●day-1, equivalent to 234 kJ for a 5-kg sifaka, and/or (ii) below an oblique line representing 500 kJ●BMkg-0.762●day-1, equivalent to 1703 kJ for a 5-kg sifaka (see discussion for details on requirements).
Table 5.
Macronutrient concentrations of 8 most important foods utilized in CONT and FRAG sites, including the proportion of available energy derived from protein; full nutritional profiles in Irwin et al. [20].
Fig 4.
Schematic depicting different lean season “rules of compromise” when nutritional target (bullseye) cannot be met.
The abundant season target is assumed to be a balanced target achieved using fruits (lower AP:NPE ratio, steeper nutritional rail) and non-fruit foods (higher AP:NPE ratio, shallower nutritional rail), and one of the major constraints of the lean season is modeled as reduced fruit availability (solid component of fruit nutritional rail). Lower fruit availability in the lean season contracts the available nutritional space from all grey areas to the darker grey area. Mountain gorillas (1) overeat protein-rich non-fruit foods to meet NPE target; spider monkeys (2) fall short on non-protein energy target but meet protein target. Sifakas might be constrained by both fruit availability and a need to preserve the abundant season’s AP:NPE ratio (3), or intakes might be further limited by plant secondary metabolites (PSMs), which limit non-fruit intakes and would explain low lean season mass intakes (4). Note that different species are likely to differ in their “starting points” (a common starting point is used for simplicity of representation); for example, mountain gorillas’ abundant season “targets” are relatively higher in protein than either spider monkeys or sifakas.