Beneath the viridescent understory of the Brazilian Amazon, ecologist Lucas Paolucci has been honing his skills for hunting tapir dung. In this region’s degraded rain forests, he sees the piglike mammal’s enormous piles of poop as a treasure.
Chock full of seeds, the dung from trunk-nosed lowland tapirs (Tapirus terrestris) may be key in regenerating forests that have been hit by intensive logging and slash-and-burn agriculture, says Paolucci, of the Amazon Environmental Research Institute in Brazil.
“Tapirs in Brazil are known as the gardeners of the forests,” he says. Feasting on the fruit of more than 300 plant species, the animals travel through the forest underbrush with their bellies full of seeds. That includes seeds from large, carbon-storing trees like mess apple trees (Bellucia grossularioides) that can’t pass through smaller animals. So the lowland tapir, South America’s largest mammal, is one of the key agents dispersing seeds throughout the Amazon.
Rooting through poop piles in Mato Grosso, a state in west-central Brazil, wasn’t how Paolucci began his career; he studied ants in Brazil’s coastal Atlantic Forest. Later, he began to wonder how forest fires in the Amazon might affect the rain forest’s insect communities. And then, he became intrigued by the monstrous dung piles — each pile “bigger than my head,” he says.
In 2016, Paolucci joined other researchers studying the role of these magnanimous defecators in restoring disturbed forests. The team conducted an experiment in eastern Mato Grosso, where two forest plots had been control burned to varying degrees from 2004 to 2010. One plot was burned every year, and the other every three years. A third plot was left untouched as a control group.
Paolucci’s colleagues walked through the plots, recording the location of 163 dung piles and comparing them with camera-trap recordings of tapirs roaming through the area. Then the team sieved the fecal findings to separate out seeds, counting a total of 129,204 seeds from 24 plant species. The camera traps showed tapirs spending far more time in burned areas than in the pristine forest, perhaps enjoying the sunshine away from the forest canopy, Paolucci says. The animals also deposited more than three times as many seeds per hectare in burned areas as in the untouched forest.
Just months after the team published those findings in March of 2019 in Biotropica, the Amazon saw one of its most destructive fire seasons in years (SN: 8/23/19). That made Paolucci even more determined to understand tapirs’ role in forests’ recovery. But he knows the tapirs can’t be doing the job alone.
So Paolucci went back to the insects he began his career with, studying how they might be partners in planting new growth. Tapirs may be leaving fecal fortunes on the forest floor, but dung beetles are actually responsible for pushing the poop around. The insects will break off and bury small pieces of dung, including any seeds within, to snack on later. That helps seed germination get going.
In early 2019, Paolucci returned to the Amazon to collect 20 kilograms of tapir dung, which he broke apart and molded into 700-gram clumps. In each clump, he inserted plastic beads as dummy seeds and then returned the poop pellets to the field. After 24 hours, Paolucci collected the dung clumps again and counted how many beads remained. Those missing had presumably been rolled away by the beetles, and, by proxy, indicated how many seeds would potentially grow into plants one day. Paolucci hopes to publish these results in 2021.
Amazon ranchers are typically required by law to maintain 80 percent of native forest cover on their properties, but many trees have been illegally cleared and need to be replanted. Tapirs could provide cost-effective help with that effort, Paolucci speculates.
But the population of lowland tapirs, the only tapir species that is widespread throughout the Amazon, is decreasing and is now considered vulnerable, due to habitat loss and hunting for meat. Roughly 20 percent of the Amazon has been destroyed, with another 7 percent expected to be gone by 2030 if current deforestation rates continue. If tapirs fail to thrive, future “seed dispersal is expected to rely even more on organisms such as dung beetles,” Paolucci says.