At the start of torpor, the fat-tailed dwarf lemur’s tail can account for up to 40% of its body weight.
The figure reflects the animal’s seasonal preparation for hibernation. During Madagascar’s wet season, the lemur feeds heavily while fruits, flowers and other foods are available. It stores much of the resulting energy as fat in its tail, creating a compact reserve for the coming dry season.
By the beginning of torpor, the tail may represent as much as two-fifths of the animal’s total mass. The lemur then draws on that reserve while metabolism is greatly reduced. This is why the tail becomes conspicuously enlarged and why the species is called “fat-tailed.”
The 40% figure concerns the tail’s share of total body weight, not the percentage of the tail that is fat and not a permanent proportion throughout the year. The tail becomes smaller as reserves are used. The animal’s unusual physiology has made it a major subject in research on mammalian hibernation and energy conservation.