One of Madagascar’s mysterious animals, the water-young lemur, only warms up its particularly long fingers when searching for food.
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The cat-sized watermelon lemur or aje-aje (Daubentonia madagascariensis) is the largest nocturnal primate in the world. Its characteristic feature is a specially modified middle finger with which it searches for insect larvae on tree trunks.
Researchers at Dartmouth College in the U.S. studied the heat distribution of an animal’s body when they noticed that the lemur’s most important “tool,” the middle finger used to search for food, is much colder at rest than its other fingers.
However, when searching, the temperature of this featured finger can rise by as much as 6 degrees Celsius. Researchers believe the lemur is likely to “turn off” its finger when not in use.
The unusual middle finger of the watermelon lemur has previously been found to be extremely sensitive to vibrations. The researchers wanted to study the surface temperature of various sensitive animal organs, so they chose this animal for thermal photography. Their findings were reported in the International Journal of Primatology.
When not in use, the finger appeared black on thermal photographs, suggesting quite a low temperature. When searching for food, the image changed to orange, indicating a large change in temperature. Researcher Gillian Moritz said they hypothesized the low temperature of the finger when not in use could be related to its long, thin shape. Objects of this shape have a relatively large surface area relative to volume, which is detrimental to thermal management.
In order for the animal to feel the vibrations caused by insect larvae through the tree bark, the finger is filled with sensitive nerve endings. However, due to the special sensing receptors, the use of the finger is very energy intensive. Like a delicate tool, it’s probably better to turn it off when not in use. “ Moritz told BBC Nature.
The way to implement the shutdown is still a mystery. The blood vessels may constrict, but it is also conceivable that the animal uses some other special method of thermoregulation. To be sure, no other animal is known yet that could separately control the temperature of its fingers.
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