After observing mountain gorillas in
Uganda for nearly a year, scientists
believe they have discovered why the
animals eat decayed wood and lick
tree stumps, behaviors that have puzzled
primate researchers for decades.
The gorillas will suck on wood chips for several minutes before
spitting them out. They have also been seen licking the bases of
tree stumps and the insides of decayed logs.
Researchers figured maybe the wood was providing some kind of
medicinal benefit, by reducing parasites and gastric upsets, but a
new study by Cornell University researchers may have solved the
mystery. They collected wood samples from stumps and logs
that the animals consumed as well as those they avoided. They
also collected samples of other things the gorillas ate.
They found that the decayed wood was the source of over 95
percent of the animal’s dietary sodium, even though it represented
only about 4 percent of their food intake.
The behavior has been observed in other primates, too, including
chimpanzees, lemurs and mountain monkeys. Elephants travel to
underground caves with salt deposits, and moose eat aquatic
plants with high sodium content.
Many animals have a specific appetite for sodium and will actively
seek it out. They don’t necessarily ‘know’ that wood is a
good source of sodium, but it does mean that they can detect it
when it is present.
Sodium is important for living organisms, and is involved in muscle
contractions, regulating blood pressure and maintaining water
and acid-base balance. Too much sodium is not good, but not
enough can be worse.