10 Mystifying Rainforest Mysteries That Baffle Scientists

A rainforest is a wild place of wonder and mystique. Every year, new species of flora and fauna are recorded by intrepid biologists who trek into the bush. Anthropologists spend their lives learning more about the reclusive people in its deepest depths. As time goes on, scientists slowly map out the mysteries of the jungle.

It takes hard work, but researchers continue to develop better methods of observation. In turn, they solve muddled mysteries about the wet world under the canopy. But even with all we know today about rainforest ecosystems, there are still so many more unknowns.

In these ten instances, scientists have spent countless hours trying to answer some of the rainforest’s biggest and most confusing questions. In some cases, a breakthrough could be just around the corner. In others, we may never know the truth. But in all, we can be sure the mystery itself is both fascinating and maddening.

Related: Top 10 Strange Scientific Studies

10 The Life of the Piripkura People and Other Isolated Tribes

Deep in the Amazon rainforest, there are tribes that have little to no contact with the outside world. Most are aware of modern life to some degree. Unfortunately, many are negatively impacted by illegal logging and mining practices. But anthropologists still don’t know much about the way they live. Way out in the remote jungle, these tribes are extremely isolated.

One of the most far-removed groups is the Piripkura. Their community, set far in the western wilds of Brazil, numbered just about 20 members in the recent past. Even their neighbors don’t know much about them. The nearby Gavião tribe knows them as the “butterfly people” due to their nomadic lifestyle. It was only in 1998 that Brazilian officials first learned of their hardships. That year, two Piripkura men left the forest to be hospitalized for an illness. During the stay, they told doctors how a hostile band of invaders had massacred most of their comrades.

Alarmed by the group’s low numbers, a Brazilian judge finally took action in 2021. He ordered the country’s indigenous agency FUNAI to set aside 600,000 acres of land for the Piripkura. The hope is that the tribe will have enough space to thrive away from modern life. Concerns abound, though.

Illegal logging continues to push closer to the people. Deforestation has brought violence, sickness, and death to the tribe’s members. Every year, their way of life becomes more threatened. Their isolation is under threat from illegal industry encroachment. In turn, anthropologists are worried they may never understand how the Piripkura really live. Insight into one of the world’s most unique and reclusive cultures may soon be lost forever.^[1]

9 A Completely Untouched African Rainforest

It’s not every day that researchers find a new part of the Earth. In fact, that hardly ever happens. Google Earth has mapped out pretty much the entire globe. Its images are accessible to us all through a few clicks of a mouse. As far as unexplored territories, there just isn’t much left. The days of intrepid adventurers sailing around the unexplored world have been gone for centuries. So imagine the scientific community’s surprise in 2012 when a conservationist discovered a completely new rainforest in Mozambique!

Dr. Julian Bayliss is a butterfly expert who has spent years using Google Earth to examine rainforests in Africa. In 2012, he made out an image of a crater on top of a mountain in the African nation. Within that crater, there seemed to be a pristine rainforest high up in the sky. Scientists were shocked at the discovery but also somewhat skeptical.

Five years later, Bayliss took a team of 28 researchers to Mozambique to find out what was in that untouched forest. The journey wasn’t without challenges, though. Scaling the mountain, called Lico, proved almost impossible. The team used drones to look ahead of them and map out paths. But after making it to the top, Bayliss’s team found some surprising things. Among them were several completely new species, including a type of butterfly that Bayliss later named after the mountain.

Even more surprisingly, they found evidence of human settlement in the sky-high jungle. Old clay pots were discovered strewn about in the dense, remote forest. The team hypothesized they had been sent up as offerings by early humans who were thankful for the river flowing down from on high. Still, nobody knows anything about the people who lived there long ago. Their route up the mountain and time spent above remains a mystery.^[2]

8 The Ancient Animal Cave Paintings of the Amazon

South America was the last continent colonized by humans. Migration patterns suggest early man moved into the area at the very end of the last Ice Age, roughly 12,000 years ago. For decades, researchers have been trying to piece together knowledge about those early communities. The incredible biodiversity of the Amazon and its rain-drenched ecosystem has made the puzzle more difficult.

Today, scientists still don’t know much about what early civilization was like deep in the jungles. That began to change in 2017. That year, archaeologists excavated an 8-mile-long (12.9-kilometer) stretch of cave drawings deep in the Colombian jungle. The hand-scrawled images are thought to date back to the earliest known times of man in the rainforest. The drawings depict animals like mastodons and giant sloths. They also show images of how early man lived in the area.

Biologists are especially interested in the portrayal of now-extinct species. As they painstakingly analyze each cave painting, they hope to learn more about early biodiversity in the rainforest. “The paintings give a vivid and exciting glimpse into the lives of these communities,” archaeologist Mark Robinson told Live Science. “It is unbelievable to us today to think they lived among, and hunted, giant herbivores, some of which were the size of a small car.”^[3]

7 The Mystery of the Mapinguari

Some Amazon tribes swear about the existence of the mapinguari. While wildlife biologists are skeptical, this giant sloth supposedly lives deep in the jungle. For centuries, the mapinguari has been a key part of old stories passed down among tribes. Folklore in those communities claims the beast stands more than 7 feet (2.13 meters) tall with matted hair and an awful smell.

Over the years, people deep in the Amazon claim to have seen it in person. To some, the beast has one eye. Others assert it has a gaping, snarled mouth in the middle of its stomach. Local myths hold that the mapinguari is most aggressive toward people who mistreat the environment within the dense, lush jungles.

Unfortunately, scientists haven’t been able to find evidence that the giant sloth-like creature really exists. And it’s not for lack of trying. Biologists have spent considerable time searching for bones and droppings throughout remote areas of the rainforest. With no hard evidence on hand, they think something else may be going on. One ornithologist thinks the mythical mapinguari is the product of long-standing local legends. “It is quite clear to me that the legend of the mapinguari is based on human contact with the last of the ground sloths,” scientist David Oren told The New York Times in 2007. “We know that extinct species can survive as legends for hundreds of years.” Ancient evidence may back him up.

Archaeologists have found fossils of a giant sloth known as the Megatherium in the Amazon. That animal has been extinct since the end of the last Ice Age. But it’s possible stories of the beast’s existence have been handed down over thousands of years. Now, locals know the tales and believe the sloth is still out there. Scientists don’t know for sure, though. Some still think there could be an undiscovered giant sloth roaming in a remote rainforest.^[4]

6 The Dead Humpback Whale of the Amazon River

Humpback whales migrate thousands of miles during their lives. One of their biggest trips comes in the summer when they swim south to Antarctica’s oceans from the northern hemisphere. So scientists were shocked in February 2019 when a year-old humpback whale was found dead on the shores of an island in the Amazon River. Locals found the whale calf on the banks of Marajo Island. It was lying on the shore upstream from the river’s opening into the Atlantic Ocean.

The whale’s discovery was bizarre for several reasons. For one, the timing of its death was wrong. Humpback whales often enjoy the warm waters of the Amazon basin early in the winter. By February, they are long gone from the area. Plus, the whale being found further upstream in freshwater confused biologists. The animal had no visible wounds, either. So poaching and whaling were ruled out. The mystery persisted, though.

The timing of its death didn’t match with known migration patterns. Eventually, scientists came to believe the whale calf was lost in a sad mix-up. One theory holds that the mammal was separated from its mother during an earlier migration. Small, weak, and on its own, strong off-season currents pushed it into the estuary. Once there, biologists believe it became entangled in a mangrove swamp. It was too weak to free itself and eventually perished in the freshwater environment.

Scientists also wonder whether it could have ingested plastic waste near the shore, hastening its death. Whatever the case, it was unheard of for locals to see a whale so far up the river. And while scientists believe their theories may be a likely scenario, they still aren’t truly certain about what happened.^[5]

5 The Uncertain Discovery of the Fire-Tailed Titi Monkey

The two-year period from 2014 to 2015 was a major period of success for biologists. In those two years, they discovered nearly 400 new species in the Amazon rainforest. Jungles are lush and dense, of course. So it’s not surprising to hear of new discoveries taking place. But some of these findings were critical to understanding the threatened landscape and its inhabitants.

In fact, one, in particular, was especially fascinating. The fire-tailed titi monkey was first recorded in a remote section of the Amazon in southern Brazil in 2010. Biologists didn’t have enough information at the time to classify it, though. The animals’ bright red tails drew attention, but they were reclusive and few in number. They spend their entire lives high up in trees, too, making observation difficult. For years, researchers went back into the jungle, hoping for more information.

By 2015, they started to develop knowledge about the monkey’s characteristics and behavior. Eventually, they officially declared it to be Milton’s titi monkey. It is named in honor of Milton Thiago de Mello, a Brazilian primatologist. The monkeys’ high-altitude habitat has made more info hard to come by. Even among primates, they are noted for keeping their distance and living in seclusion. Thus, recording observations has been a slow process. Wildlife researchers are working hard to know more about them, but their remote habitats have proven tough. Today, biologists still don’t know very much about these tree-dwelling jungle creatures.^[6]

4 The “Silkhenges” of Peru

We all know that spiders spin silk to make webs. But in the rainforests of eastern Peru, certain spiders have been creating unique silk structures for completely unknown reasons. In fact, researchers aren’t even certain which type of spider is the one doing the spinning. And their discovery was only first made in 2013! But the incredibly intricate designs of these webs have fascinated entomologists ever since. Some have even taken to calling them “silkhenges” because of how they hold a central cone surrounded by pillars—almost like a silk version of England’s Stonehenge.

In 2019, tropical entomologist Phil Torres was finally able to capture amazing video evidence of the silk structures. Torres and others believe they are made by a spider trying to protect its egg sac. Arachnologists haven’t been able to see these silkhenges being made, though. Without evidence of their construction, experts know little else about the reason they exist. And yet their existence is widespread.

Some researchers have found these silk creations in other far-reaching parts of the Amazon basin. “One key thing that we learned this time that I could say for certain is that now we’re finding them in clusters,” Torres told Live Science in 2020. “If you find one, and you spend enough time looking around that immediate area, you’re going to find more. That tells us something about the behavior.” Beyond that, biologists remain baffled. Torres and his colleagues hope to learn more one day.^[7]

3 The Mysterious Smoked Mummies of Papua New Guinea

Mummification isn’t just practiced in Egypt. In fact, tribes in the tropical Highlands region of Papua New Guinea have their own take on it. While ancient Egyptians used salt and spices to desiccate water from dead bodies, Papuans had a different way of doing things. The Anga tribe used heat to burn out moisture from corpses. They would hang dead bodies over a fire until they were charred. Then, they would slice open the corpses at the knees, elbows, and feet. Hollow bamboo poles were inserted into the slits to help evacuate blood and fluids.

As the body drained, the fire helped dry out the corpse’s contents. Villagers would supposedly collect their dead loved ones’ fluids and cover themselves in them as a show of mourning. Meanwhile, the bodies were left standing out in the open to dry. Then, they were propped up on a cliff overlooking the village. Their position was meant to signify that the deceased was now looking over the tribe.

Today, the Anga’s reasons for practicing mummification aren’t well known. In fact, the practice is only known because of a British explorer from the early 20th century. Charles Higginson visited the Anga in 1907 and documented their mourning practices. He was disgusted by what they did. He claimed they were “bloodthirsty savages” and criticized their alleged practice of ingesting and spreading dead relatives’ bodily fluids. But today, historians think Higginson over-exaggerated his tales.

One modern-day anthropologist has wondered why these supposedly “bloodthirsty” natives didn’t make Higginson one of their victims. “If that was the case,” researcher Ian Lloyd Neubauer argued in 2015, “why didn’t the Anga make a meal of Higginson, a lone and defenseless foreigner living in their midst?”

It’s a valid question. And it’s one that has no answer. Mummification ended in 1949 when Christian missionaries began living with the Anga. Today, the tribe’s remaining mummies are decades old but still intact. Villagers take great care to look after the remains. But with mummification ending generations ago, locals can’t offer insight beyond Higginson’s shoddy reporting. Thus, the reasons for this unique mourning process will likely forever remain a mystery.^[8]

2 The Red-Hot River of Mayantuyacu

A remote town in central Peru called Pucallpa is near one of the most interesting and mysterious places in the Amazon. The tiny town sits by a red-hot river that is said to kill anything that enters it. The boiling river of Mayantuyacu runs extremely hot all year round. Scientists have measured its temperature anywhere from 120° to almost 200°F (38° to 93°C).

It’s not a long river, measuring just 4 miles (6.4 kilometers) in length. And it’s not incredibly powerful, either, with its deepest depths at 16 feet (4.9 meters). But the boiling water can be deadly. People who have fallen in have suffered third-degree burns within seconds. Visitors are advised to stay away to avoid severe injury or death. Through it all, the river is said to be sacred. A local shaman guards the river and claims its water is good for medicine.

Conservationists are fascinated by the river’s scalding temperatures. In 2011, Peruvian geoscientist Andrés Ruzo trekked to Pucallpa to study the Mayantuyacu. He noted its average temperature to be 187°F (86°C). While not completely boiling, he saw how the intensely hot waters were fatal to wildlife. But he was confused as to why the river was so warm in the first place. As he discovered, there is no nearby volcanic activity.

To this day, Ruzo doesn’t have a definitive answer for the boiling river. As best he can figure, the river may ride above a deep ground sink. As the water descends into the Earth, it heats up. Then, the heat presses the water up through faults and cracks. By the time it reaches the surface, he theorizes, the water remains remarkably hot. Today, Ruzo continues to study the river. He hopes to one day have a scientific explanation for the amazing phenomenon.^[9]

1 The Bizarre Lost Birds of Barro Colorado

Panama’s Barro Colorado Island once hosted more than 200 bird species. But in the last century, a quarter of them have disappeared. And scientists aren’t sure why. The trouble first began after 1914. That year, the Panama Canal was completed. In the ensuing months, the water level of nearby Gatun Lake rose sharply. It quickly filled in the valleys around Barro Colorado.

By the 1980s, ecologists thought the larger lake might have snuffed out predators in the area. In turn, populations of mid-sized mammals like monkeys and coatis blossomed. Those mammals often eat bird eggs. Thus, scientists assumed those primates had stifled the bird population. But the mystery was far from solved.

In 1994, ecologist Douglas Robinson began researching bird flight patterns on the island. He found that many local species were unlikely to ever fly off the island. In addition, it turned out monkeys and coatis were not responsible for eating bird eggs. Instead, video evidence proved the local snake population was culling the nests. Researchers had never considered that possibility.

Still, by 2000, more than 45 bird species had completely disappeared from the island. Snakes alone couldn’t account for such a significant and quick loss in biodiversity. Robinson has continued to research the situation with the hopes of one day solving the mystery of the missing birds of Barro Colorado. To date, there is no definitive answer for the extinctions.^[10]