White adipose tissue composition in the free-ranging fat-tailed dwarf lemur (Cheirogaleus medius; Primates), a tropical hibernator

In temperate species, hibernation is enhanced by high levels of essential fatty acids in white adipose tissue. Essential fatty acids cannot be synthesized by mammals, thus nutritional ecology should play a key role in physiological adaptations to hibernation. Tropical hibernators are exposed to different physiological demands than hibernators in temperate regions and are expected to be subject to different constraints. The aims of this study were to assess whether or not the tropical hibernator Cheirogaleus medius shows biochemical changes in its white adipose tissue before and during hibernation. A capture-recapture study was combined with feeding observations in western Madagascar. Before and after hibernation, 77 samples of white adipose tissue from 57 individuals of C. medius, as well as dietary items eaten during pre-hibernation fattening, were sampled and analyzed for their fatty acid composition. In contrast to temperate hibernators, C. medius exhibits extremely low essential fatty acid concentrations in its white adipose tissue (2.5%) prior to hibernation. The fatty acid pattern of the white adipose tissue did not change during pre-hibernation fattening and did not reflect dietary fatty acid composition. During hibernation, fat stores showed only minor but significant compositional changes. Because of its prevalence, the main fuel during hibernation was the monounsaturated oleic acid, which seemed to be preferentially synthesized from dietary carbohydrates. Results suggest that essential fatty acids do not represent an ecological limitation for hibernation in the tropics, at least not in the fat-tailed dwarf lemur.