- Inside a tree hollow, a bundle of fur lies unmoving. Despite appearances it is not dead, but deep in hibernation. But this tree isn't laden with snow, the winds aren't howling, and the temperature isn't way below zero. The tree is in the tropics, and the animal is a primate – a fat-tailed dwarf lemur.
- What makes dwarf lemurs unique is that they are the only primates, and the only tropical mammal, known to hibernate.
- When animals hibernate, it is usually because they need to reduce their energy expenditure over the cold winter months when food and water are scarce. So what good is hibernation in the tropics?
- Although dwarf lemurs don't have to deal with the mercury plummeting, they do have to cope with food and water resources nosediving during the dry season on Madagascar.
- Before the food disappears, they gorge themselves on sugary fruits, storing large quantities of fat in their tails and increasing their body weight by up to 40 per cent. They then climb into tree holes for six months or more of serious downtime, getting all of the energy and water they need from their tails. Their body weight may have halved by the time they emerge.
- So far, so typical. But what is unusual about these lemurs is that they don't drastically reduce their body temperature during their slumber as other hibernators do. Instead, their body temperature can fluctuate by as much as 20 °C because they match it to the temperature of their nest.
- This was so surprising when it was discovered in 2004 that some scientists called for hibernation to be redefined.
- Two other lemurs have now been observed hibernating - the little-known Crossley's and Sibree's dwarf lemurs found in eastern Madagascar, but this has shed little light on their fat-tailed cousin's weird behaviour. Unlike it, these lemurs do maintain a constant body temperature.
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