Pulling Their Weight

Photograph by Roman Willi

Costa Rica’s rainforests are typically painted in vibrant hues, with flamboyant flowers, jewel-toned birds, and neon tree frogs. Yet beneath this colorful palette is a carpet of decaying leaves, and beneath the dull leaf litter are innumerable creatures whose contribution to the visual feast above goes largely unappreciated: ants.

More than 900 species and subspecies of ants (family Formicidae) crawl, skitter, and climb through Costa Rican ecosystems, comprising up to 25 percent of the terrestrial biomass here and in other tropical forests. Though most individuals weigh less than a grain of rice, they together keep the rainforest running smoothly. Ants feed a variety of wildlife, churn up soil, change the soil’s chemistry, and clear dead plants, animals, and insects. Microbes and other invertebrates also help with decomposition, but one study suggests that ants remove more than half of all dead material that falls to rainforest floors. Other research shows that leafcutter ants mow down so much vegetation that they alter forests’ architecture, creating gaps in the canopy. Ants from a single nest can harvest up to two metric tons (2,200 pounds) of leaves annually.

Ants’ own bodies—particularly their ability to carry heavy loads—play a role in this aptitude for ecosystem engineering. Their “necks” and mandibles have a unique physiology, with one type of muscle fiber that allows for quick, spring-loaded snapping so explosive it can kill small prey instantly or propel an ant backward, away from danger. Another bestows ants with sustained force for carrying heavy loads. Combined with specialized biomechanics that researchers are still studying, this anatomy lets some ant species lift more than 5,000 times their body weight—equivalent to an adult human hoisting two Statues of Liberty with only their head and neck.

While most visitors to the rainforest are drawn to colorful landscapes and charismatic megafauna, photographer Roman Willi seeks creepy crawly denizens like ants. When he spotted these two near Monteverde, Costa Rica, carrying a dead weevil (family Curculionoidae), he paused to photograph the industrious duo before they disappeared once more into the leaf litter.

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