- A recent study has confirmed that Amazon jaguars have developed a fascinating strategy to face seasonal river flooding: when the waters rise and flood the forests, these felines begin to live up in the trees.
- The finding, made in the Mamirauá Sustainable Development Reserve in Brazil’s western Amazon, surprised researchers who initially thought the animals would migrate to dry lands in search of prey.
- The research monitored 14 jaguars fitted with GPS collars between 2011 and 2020; the data showed the home range of these animals during floods remained virtually unchanged from during the dry season.
- While this adaptation is unique to Amazon jaguars, experts warn that variation in rain and flood cycles, aggravated by climate change, may pose yet another threat to this already near-threatened species.
“It’s amazing, it’s amazing! I have no other word to describe it.” That’s how biologist Marcos Roberto de Brito defines the thrill of seeing a jaguar up close for the first time. Brito is the lead author of a recently published study that discovered a unique trait in the jaguars of the Mamirauá Sustainable Development Reserve, in Brazil’s western Amazon: during floods, the big cats spend up to four months living up in the trees, where they hunt, mate and care for their young.
Between 2011 and 2020, researchers from the Mamirauá Institute, including Brito, used GPS collars to track 14 jaguars (Panthera onca) in the reserve. Located between the Solimões and Japurá rivers, before they join to form the Amazon, the reserve experiences annual floods that, depending on weather conditions, can raise the water level in the rivers by an average of 10 meters (33 feet). The water inundates the floodplain forests for approximately four months. But the local jaguars have found a surprising way to adapt, says study co-author Guilherme Alvarenga, a biologist at the Mamirauá Institute.
“When the river starts to flood, their prey, such as tapirs and wild pigs, simply leave the floodplain and go to dry land. One would assume that the jaguars would go after them, right?” he says. “But that’s not an option in the Mamirauá reserve, because the entire area is surrounded by two large rivers. The floodwaters are unbelievable. They reach 16 meters [52 ft] in some places.”
So the jaguars take to the trees. Living up in the trees demands considerable effort, since jumping between branches, climbing up and down trunks, and even swimming from tree to tree are all laborious and exhausting, especially when there’s less prey available. This led the researchers to hypothesize that the home range of individual jaguars, which are territorial animals, would decrease during the floods: by scaling back their displacements, they were expected to occupy a smaller territory. But the reality was the opposite.
“My impression is that creating and defending a home range is so difficult for a jaguar that it works hard to keep it, whether in dry or wet seasons,” Alvarenga says.
By monitoring the collared jaguars for up to 538 consecutive days, the researchers found their territories ranged from between 50 and 373.6 square kilometers (19.3 and 144.2 square miles). That didn’t vary much with seasonality; in fact, the home range of some of the jaguars monitored even expanded during the floods.
But if there’s no prey on the land during this period, the question remained: what do the jaguars eat? Brito said he was lucky enough to observe jaguars sleeping on trees during the day to save energy, and even saw one catching a howler monkey that was jumping between the branches.
“There are many monkeys and sloths in the reserve. Our hypothesis is that the jaguar starts lying in wait, waiting for prey to capture instead of actively hunting them, precisely as a way of saving energy.”
To catch a jaguar
A native of the Atlantic state of Rio Grande do Norte, Brito arrived in Mamirauá, at the other end of Brazil, in 2019, when the jaguar-tracking research was already underway. Until then, he’d never worked with big felines, having dedicated his master’s studies to something much smaller: butterflies.
His focus changed in 2017 when he moved to the Amazonian city of Manaus with a biologist friend. “The Amazon is a magnet,” he says. Passionate about the forest, he sought out any opportunity to work in the region, until he was able to study jaguars.
Initially, Brito was only responsible for processing and analyzing the data collected, under Alvarenga’s supervision. However, the need soon arose to also involve him in field expeditions to capture the biggest wildcats in the Americas and fit them with tracking collars.
“Everything in the Amazon is difficult, expensive, distant, and communication is poor. We go to fieldwork using a floating base, and we stay there for 30 days,” Brito says. “We spread traps throughout the forest, placing a radio transmitter in each one, but we have to check them constantly to prevent the animals from being trapped for too long.”
When a jaguar gets caught in a trap, the researchers proceed carefully, usually late at night, Brito says. They fire a tranquilizer dart from a distance. In his first such experience, Brito and two novice colleagues watched from afar while the more experienced Alvarenga and a veterinarian, Louise Maranhão, measured and weighed the unconscious jaguar. In the dark, all that could be heard was its grunting. The tension was palpable until the veterans returned and invited their newly hired colleagues to see the animal.
“There he was, my first jaguar, called Xangô,” Brito recalls. “He weighed about 60 kilos [132 pounds]. Jaguars in Mamirauá are smaller than in other regions, which makes it easier for them to climb trees. But they are still very muscular and strong animals. And there he was, sleeping. Awesome!”
Each campaign involves about five professionals, including researchers, a veterinarian and assistants. A cook is also hired and remains on the floating base. A GPS collar costs approximately $2,500, on top of the overall expedition cost of about $8,500, covering staff, provisions and supplies.
Hand in hand with traditional knowledge
Lázaro Pinto dos Santos and Railgler Gomes dos Santos were two of the field assistants who participated the most in the search for jaguars. As residents of the reserve, they were “phenomenal,” according to Brito. “After days of searching, Lazinho would tell me: ‘Marcão, let’s set the trap here,’ and he was right. He knew where the animal was and how it liked to move,” Brito says.
Both men have since passed away: Railgler drowned in 2020 and Lázaro died of heart problems in 2023. As a posthumous tribute, they’re credited as co-authors of the study that resulted from years of their dedication.
Created in 1990, the Mamirauá Sustainable Development Reserve, located in the heart of the Amazon, is home to 6,642 people: 1,811 inside the reserve itself, and 4,831 in its surroundings. They include farmers, riverside dwellers (or ribeirinhos), and extractivists, whose way of life centers on the sustainable extraction of forest resources.
Local community leader Paulo Cavalcante Martins worked directly on the jaguar project. He underscores the active participation of other community members in the capture and research activities. “Lázaro and Railgler were the ones who worked the hardest on this project. They spared no effort, day or night,” he says.
The jaguar research in Mamirauá began in the 2000s under Emiliano Ramalho, now the head of the feline research group at the Mamirauá Institute. In the early years, conversations with riverside residents were essential to understanding the behavior of jaguars during floods. It was the community members who first told the researchers that the felines took to the trees during floods.
To confirm what traditional knowledge already knew, it was necessary to install collars and use sophisticated monitoring modeling. The collars record the locations of the jaguars at scheduled intervals of one to six hours. In total, around 13,000 locations were collected.
Changes in the Amazon’s flood pulses
Jaguars are scattered across a range that goes from Mexico in the north to Argentina in the south, with impressive adaptations in each region. In the Pantanal wetlands, south of the Amazon, for example, they’re fishers. Studies underway suggest that Mamirauá is home to the second-largest jaguar population ever recorded in South America. And it’s only here where jaguars live in the trees, showing how biodiversity is shaped by the environment.
However, the Amazon’s drought-and-flood cycles are changing — a trend that’s been evident for more than a decade. Record droughts hit Mamirauá from 2023 to 2024, while the Rio Negro, which runs north of the reserve, saw its lowest level in 122 years, at just 12 m (39 ft). That came after a historic flood in 2021, when the river’s water level reached 30 m (nearly 100 ft). Hydrologist and Amazon expert Jhan-Carlo Espinoza says extreme droughts and floods in the area are influenced by El Niño and La Niña, which warm and cool Pacific Ocean waters, respectively. However, these climate events have become more frequent and overlapping, thus preventing the normalization of the rivers’ pulse.
“Global warming is probably intensifying these conditions,” Espinoza says. “The transition between La Niña and El Niño is part of natural climate variation, but it is accelerated by the increase in the planet’s average temperature and factors such as the warming of the Atlantic.”
Such drastic changes in the rise and fall of rivers impact all animals, including jaguars. “This alters the dynamics of the ecosystem,” Alvarenga says. “The Amazon Rainforest is sensitive to changes. Prolonged droughts reduce humidity and increase tree mortality, which unbalances everything else. Long floods expose animals such as jaguars to more severe periods of scarcity.”
Jaguars are the only big cats not currently in one of the IUCN Red List’s threatened categories (vulnerable, endangered, or critically endangered). But they’re listed as near-threatened. In Brazil, home to half of the world’s jaguars, the main threat is habitat loss caused by deforestation, aggravated by conflicts with ranchers. In an Amazon under transformation, climate change has emerged as another imminent risk.
Banner image of a jaguar in the Mamirauá reserve. Image courtesy of Emiliano Ramalho/Mamirauá Institute.
Meet the fishing jaguars that have made this patch of the Pantanal their own
Citation:
de Brito, M. R. M., Alvarenga, G. C., Oliveira-Santos, L. G. R., Maranhão, L., Pinto dos Santos, L., Gomes dos Santos, R., … Ramalho, E. E. (2025). Impact of seasonal flooding on Jaguar (Panthera onca) home range and movements. Journal of Mammalogy. doi:10.1093/jmammal/gyae145
This story was first published here in Portuguese on Feb. 24, 2025.
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