title: When to initiate torpor use? Food availability times the transition to winter phenotype in a tropical heterotherm.
abstract: Timing of winter phenotype expression determines individual chances of survival until the next reproductive season. Environmental cues triggering this seasonal phenotypic transition have rarely been investigated, although they play a central role in the compensation of climatic fluctuations via plastic phenotypic adjustments. Initiation of winter daily torpor use-a widespread energy-saving phenotype-could be primarily timed according to anticipatory seasonal cues (anticipatory cues hypothesis), or flexibly fine-tuned according to actual energy availability (food shortage hypothesis). We conducted a food supplementation experiment on wild heterothermic primates (grey mouse lemurs, Microcebus murinus) at the transition to the food-limited dry season, i.e. the austral winter. As expected under the food shortage hypothesis, food-supplemented individuals postponed the seasonal transition to normal torpor use by 1-2 month(s), spent four times less torpid, and exhibited minimal skin temperature 6 °C higher than control animals. This study provides the first in situ experimental evidence that food availability, rather than abiotic cues, times the launching of torpor use. Fine-tuning of the timing of seasonal phenotypic transitions according to actual food shortage should provide heterotherms with a flexible adaptive mechanism to survive unexpected environmental fluctuations.
authors.affiliation: Mécanismes adaptatifs et Evolution (MECADEV UMR 7179), Sorbonne Universités, Muséum National d'Histoire Naturelle, Centre National de la Recherche Scientifique, 1 avenue du Petit Château, 91800, Brunoy, France, pauline.vuarin@gmail.com.
authors.forename: Pauline
authors.initials: P
authors.lastname: Vuarin
authors.forename: Melanie
authors.initials: M
authors.lastname: Dammhahn
authors.forename: Peter M
authors.initials: PM
authors.lastname: Kappeler
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Henry
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D016565:Cheirogaleidae / Q000254:growth & development / Q000502:physiology*; D005508:Food Deprivation / Q000502:physiology*; D010641:Phenotype; D012098:Reproduction; D012621:Seasons; D013997:Time Factors; D064348:Torpor / Q000502:physiology*