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Jaguar population increases after wildfire and drought, indicating area's role as climate refuge

Following a large-scale wildfire, more jaguars migrated to a study site in the Brazilian wetlands that already had the largest population density of jaguars in the world, a new study found.

"Finding even more jaguars and other mammals in the study area following the 2020 wildfire and extreme drought suggests that it may serve as a climate refuge, buffering the effects of extreme climate events," said Charlotte Eriksson, a post-doctoral scholar at Oregon State University.

The 36,700-acre site is a seasonally flooded protected area in the northern portion of the Brazilian Pantanal, the largest freshwater wetland in the world.

Past research by Eriksson and others at Oregon State and in Brazil found the site is home to a population of jaguars that are unique because their diet primarily consists of aquatic organisms, instead of land-based animals, and because they are more socially tolerant and willing to share space with other jaguars.

For the new study, in Global Change Biology, the researchers, who have studied the jaguars since 2014, used video of jaguars and other mammals they captured from field cameras they deployed before, during and after the wildfire. They also collected nearly 175 jaguar scats to analyze the jaguars' diet.

The study site, much of which is federally protected, is five hours from the nearest town and can only be accessed by humans via boat. There are no roads, trails or settlements nearby. Researchers cover themselves from head to toe because of the abundance of biting insects.

Eriksson has been working on the project since 2017, first as a doctoral student in Oregon State Professor Taal Levi's lab and now as a post-doctoral scholar. She visited the study site in 2018 and 2021.

Jaguars are the most frequently detected mammals detected by the cameras, which is highly unusual for a large, solitary carnivore, Eriksson said. She said that would be similar to most frequently seeing a cougar or mountain lion on cameras in North America, instead of for example, deer.

She said that whenever she got off the boat, she would see jaguar tracks. In fact, one of her cameras recorded a jaguar just seven minutes after she set it up.

"I have never been to a place where the presence of a large carnivore is so obvious," she said.

The 2020 wildfires, driven by extreme drought, extreme temperatures and human activities, burned more than 11 million acres, including half the study site, and caused an estimated loss of 17 million vertebrates.

In the just-published paper, the researchers set out to understand the short-term impacts of the fire and long-term effects of drought on the population of jaguars and other mammals and whether the changes were driven by fire, drought or both. Findings included:

• Jaguar activity initially declined post-fire, indicating a short-term impact, but rebounded over time, with a significant increase in abundance and birth of cubs one year after the fire.
• Jaguars living in the area before the fire were sighted at similar rates before and after the fire, indicating that resident jaguars survived the fires and maintained their home ranges, while a large number of immigrant jaguars arrived from other areas, indicating the area served as a climate refuge.
• Richness and abundance of other mammal species increased across the study period, but was more strongly correlated with drought-induced changes than with fire-related impacts because the increase in species richness began in 2018 – before the fire. Researchers also didn't find a significant difference in species richness between camera sites burned during the fire or not burned.
• Jaguars maintained their specialization on aquatic prey, particularly fish and caiman alligators, despite the increase in mammals, supporting the hypothesis that consumption of aquatic prey reduces predation pressure on land-based mammals.

The researchers caution against generalizing their findings to other areas because of the unique nature of this part of the Pantanal, including the fact that parts of it are protected, but they emphasize the importance of maintaining such refugia and implementing proactive fire management.