Mud, Mud, Glorious Mud?

The bats regularly visit so-called salt licks in the rainforest. Salt licks are water bodies with salty water or areas with mineral-rich clay.

The researchers draw far-reaching conclusions: Populations of fruit-eating bats may be supported by the additional mineral intake at salt licks, and since fruit-eating bats are major seed dispersers in tropical rainforests, mineral licks may have a strong, though indirect impact on plant biodiversity in the tropics.

Christian Voigt and his colleagues captured bats at salt licks and randomly selected sites in the Yasuni National Park in the Ecuadorian Amazon rain forest. Bats captured at salt licks were almost exclusively pregnant or lactating females, whereas bats captured at randomly selected sites in the forest were equally likely males or females; and females at these sites were neither pregnant nor lactating. Most of the bats at salt licks were fruit-eating species.

Christian Voigt explains: “Bats that do not eat insects often lack minerals, since fruits are poor in minerals. These animals need additional nutrients to increase milk production and promote skeletal growth in their offspring, since their offspring cannot be weaned until they have reached almost adult size. A young bat needs a fully developed skeleton for getting airborne”.

Soils in rainforests are generally depleted in minerals. This affects humans as well. “In tropical South America and Africa, indigenous people also eat mineral-rich clay”, says Voigt. Such clay can be bought at local markets, too. Obviously, bats and humans have discovered a similar solution for the same problem.

Voigt and his colleagues published their study in the open-access online journal “Research Letters in Ecology”.