Data from: Nutrient-specific compensation for seasonal cold stress in a free-ranging temperate colobine monkey

1. Homeostatic responses of animals to environmentally-induced changes in
nutrient requirements provide a powerful basis for predictive ecological
models, and yet such responses are virtually unstudied in the wild. 2. We
tested for macronutrient-specific compensatory feeding responses by
free-ranging golden snub-nosed monkeys (Rhinopithecus roxellana)
inhabiting high altitude temperate forests where they experience a
substantial difference in ambient temperature in cold winters vs. warmer
springs. The monkeys had free access to natural foods throughout the year,
and to ensure that any seasonal differences in nutrient intake were due to
homeostatic compensation and not constraints on food availability, we
studied the monkeys during periods in which they were provisioned with the
same amount of supplementary foods in winter and spring. 3.
Thermoregulatory energy costs in winter and spring were calculated using
partitional calorimetric estimations of convective and radiative heat loss
obtained from thermal imaging of free-ranging monkeys in situ. Daily
nutrient intakes were measured using continuous focal follows (average 6.9
h/day) of free-ranging individuals (27 in spring and 28 in winter). 4. We
used a nutritional geometry framework to integrate these data and test
three predictions: i. In order to remain thermoneutral (balance heat loss
with heat expenditure), golden snub-nosed monkeys decrease daily energy
consumption during the spring compared to winter, ii. Decreased energy
intake is accomplished specifically by reducing intake of the primary
energetic nutrients, carbohydrate and lipid, relative to protein, and iii.
The seasonal reduction in ingested fat and carbohydrate calories will
quantitatively match the reduction in thermoregulatory costs in spring
compared with winter. 5. Our results showed that energy intake in spring
was reduced to almost half (55%) of that in winter. As predicted, this was
achieved by specifically reducing fat and carbohydrate consumption with
protein intake unchanged, by a quantity (326 kJ/mbm) that almost exactly
matched the seasonal difference in the daily energetic costs of
thermoregulation (329 kJ/mbm). 6. This is the first study to test for a
match between nutrient-specific homeostatic compensation and
environmentally-induced perturbations in nutrient requirements in
free-ranging animals, and underpins the potential for the homeostasis
framework to provide predictive power to ecological models.