The tropical forest ecosystems around the Tambopata River are famous for the opportunities they offer travelers from all over the world to spot major fauna. During their Peru vacation, many travelers are rightly drawn to the biodiverse Tambopata National Reserve and our own Tambopata Private Conservation Area in search of dramatic moments in the presence of major Amazon fauna. But visitors who choose to select an ecotourism excursion as part of their South America vacation should remember that they are also the habitat of many thousands of truly fascinating insect species.
The most numerous species of insect in the Amazon, and one of the species most representative of the complexity of insect life in the rainforest, is the leaf cutter ant. In the forests of South America, Central America and Mexico, leaf cutters are divided into a total of 47 species.
Leaf cutter ants can be seen on trails in Tambopata National Reserve, busily marching in seemingly endless foraging lines, with each ant carrying a section of leaf much larger than its own body.
After humans, leaf cutters are said to form the largest and most complex societies on Earth. A single colony of leaf cutter ants can contain millions of members. Each colony is a super organism with a collective function: to gather leaves and carry them back to their underground nest. As they cut through a leaf with their specially adapted mandibles, the ants produce high frequency vibrations that stiffen the leaf and make it easier to cut.
Working together, they can strip a tree bare in 24 hours. They follow scent trails back to their nest, increasing efficiency by keeping their path clear of forest debris. A leaf cutter nest can be up to eight meters deep, and contain thousands of interconnected chambers.
The leaves these ants gather are not used for food. Leaf cutter ant societies are based upon what scientists call ant-fungus mutualism, through which vast colonies of leaf cutter ants use the leaves they collect to create fungus gardens. This fungus is used to feed the ant larvae. Neither the fungus nor the ant could survive without the benefit of this reciprocal arrangement.
Within this carefully calibrated society, different ants perform a range of duties, from the smallest minim ants that tend the fungus garden, to patrolling minors that act to defend forage lines, and the mediae, responsible for cutting leaves and carrying them back to the nest. Meanwhile, so-called majors, the largest of the worker ants, combine with military discipline to defend the colony against intruders.
In addition to feeding them with freshly harvested plant material, the ant colony also works to keep the fungus they cultivate in their garden free of pests and mold. These behavioral adaptations are supported by biological characteristics; the bacteria that grow on the bodies of leaf cutter ants enable them to secrete chemicals that maintain the health of their fungus garden.
Scientists have discovered that the symbiotic relationship between these ants and their crops is so finely tuned that the ants are able to detect fluctuations in the health of the fungus caused by reactions to different types of plant matter. Responding to these changes, leaf cutter ants will harvest alternative plant species in order to vary the feed they give their garden.
Colonies are founded by a single queen, which through multiple couplings collects hundreds of millions of sperm in order to establish her city state of up to eight million individuals. With their division of labor based upon a caste system, the employing of complex farming techniques, and the use of pest and waste management practices, leaf cutter ants form societies every bit as complex as those found among other “higher” life forms.