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Apr 25 2025
2A groundbreaking study conducted by Brazilian researchers has provided the first-ever estimate of the population density of deer species within the Atlantic Rainforest, revealing the significant influence of human activity on the wildlife of this vital ecosystem. This research marks a major milestone in the conservation of the biome, with the findings underscoring the profound effects of anthropogenic pressures on local biodiversity.
For more than a decade, a team of researchers has worked tirelessly to estimate the population density of five deer species native to the Atlantic Rainforest. Their efforts were largely focused on understanding the primary factors that affect the number of deer in specific forest areas. These factors included both natural elements, like altitude and vegetation types, as well as the increasingly evident role of human impact. The study was carried out at 31 sites across 21 conservation units throughout the Atlantic Rainforest, spanning from the Northeast to the South of Brazil.
The method used in the research involved tracking deer feces at these sites, with specially trained dogs used to locate the droppings. Once collected, fecal DNA analysis was conducted to accurately identify the species of deer in the area. This innovative approach allowed for the estimation of population density in areas that are otherwise difficult to study due to the elusive nature of these animals. The findings revealed a strong correlation between the low density of deer and the extent of human disturbances such as hunting, predation by domestic dogs, diseases carried by livestock, and the competition with wild boars—an invasive species that shares resources with the deer.
Márcio Leite de Oliveira, a professor at the University of Araraquara (UNIARA) and the lead author of the study, explained that forest-dwelling deer are notoriously difficult to spot, making population density a crucial but challenging metric to obtain. He emphasized that the study’s results, which have been incorporated into Brazil's National Action Plan for the Conservation of Ungulates, will significantly aid in managing and protecting deer populations in the future.
The data gathered also provided insights into how environmental factors such as vegetation, slope, and altitude interact with human threats. Each surveyed site was evaluated for the presence of human-induced pressures, which were scored on a scale from 0 to 2—zero indicating no threat and two indicating a high prevalence of threats. This evaluation revealed that human activities had the most profound impact on deer density, surpassing the influence of natural environmental factors.
The results were striking: the lowest deer density recorded was just 0.14 individuals per square kilometer for roe deer in the Araucárias National Park in Santa Catarina, while the highest density was observed in the Sooretama Biological Reserve. The red deer, however, presented an anomaly, with densities ranging from 1.47 to 3.42 individuals per square kilometer in the sampled areas.
In addition to the detrimental impacts of human threats, the study also highlighted the positive influence of human presence in certain circumstances. Notably, the presence of park rangers was shown to have a positive effect on deer populations. Areas with more park rangers exhibited higher deer densities, as conservation efforts in these regions helped protect the animals from hunting and other threats.
Oliveira and his colleagues also referenced previous research that indicated even a small increase in protected areas—just 2% more of the Atlantic Rainforest—could greatly benefit at least three species of deer. This work further underscores the importance of maintaining and expanding conservation efforts in the region.
“The data provided by this study offers a clear snapshot of the current situation for cervids in the Atlantic Rainforest. By repeating these population density estimates every five or ten years, we can better understand how conservation strategies are influencing deer populations, identifying where improvements are needed and where efforts have succeeded,” concluded Oliveira.
The findings from this study serve as a call to action for the continued protection of the Atlantic Rainforest, where human activities continue to pose significant challenges to the survival of many species. The evidence gathered by this research provides a critical foundation for informed, data-driven conservation policies aimed at ensuring the long-term sustainability of this rich and diverse ecosystem.
Source:https://phys.org/news/2025-04-human-threats-outweigh-natural-factors.html
This is non-financial/medical advice and made using AI so could be wrong.
