Our study yielded new insights into the influence of various ecological and anthropogenic variables on a community of felid predators and their prey in the Amazon rainforest. Responses to human impacts were strongest for the most highly persecuted mammals – both predators and game species – but were also very species-specific within the predator and prey guilds. In addition, mammals with less hunting pressure did not spatially avoid the more disturbed sites within our study area.
We did not observe any anthropogenic effects on one of the most persecuted species, white-lipped peccary (hereafter “white-lips”), because we did not capture them for seven years consecutively. Their absence is concerning given their ecological role, vulnerable status according to the IUCN, and near-threatened designation in Peru by SERFOR (IUCN, 2022; SERFOR, 2018). In contrast to the usual abundance of white-lips compared to collared peccary in Amazonian ecosystems, our study observed an abundance of collared peccary and no white-lips until 2022. White-lips typically dominate over collared peccaries, leading to lower occupancy probability for the latter at sites occupied by white-lips (Ferreguetti et al., 2017). They serve as ecosystem engineers, seed predators/ dispersers, and important prey for top predators like puma and jaguar (Ferreguetti et al., 2017; Kiltie & Terborgh, 1983). The disappearance of white-lips from large regions like MDD for over ten years initially led to the hypothesis of migration; however, a 15-year study in northern Brazil debunked this, showing that population declines were caused by disease outbreaks rather than migration (Fragoso, 2004). Disease outbreaks resulted in high mortality, with hunting further reducing the remaining individuals, while areas without hunting allowed for repopulation (Fragoso, 2004). Recolonization of herds from distant locations explains the 10–15-year process observed across the Amazon rainforest. The development of remote areas in the Las Piedras region, including road construction, settlement formation, and agriculture, has led to increased habitat fragmentation, hunting, and disease, likely contributing to the disappearance of white-lips. Our camera traps did not capture white-lips from 2014 to 2021, suggesting an epidemic after urbanization and the introduction of agriculture/livestock in the early 2000s. However, small groups were observed in person between 2017 and 2020 (D. J. Singer, personal communication, May 20, 2023), indicating that a few groups remained to repopulate the area; we then obtained our 35 records of white-lips on camera within the confines of the protected corridor in 2022. Encouragingly, in May 2023, our team witnessed a group of over 100 individuals, indicating population stabilization within the conservation corridor but unknown status outside of this privately protected area.
After white-lips, the most sought after bushmeat species include agouti, collared peccary, brocket deer, and lowland tapir, which all had significant responses to our anthropogenic covariates: distance from the closest settlement, proximity to agriculture, and land use type. Although agoutis are thought to be more adaptable to human-modified areas (Naughton-Treves et al., 2003), their negative relationship with settlements indicates a direct response to human presence and likely hunting pressure. Brocket deer and collared peccary both decreased in occupancy probability in mixed-use areas, which aligns with results from previous studies, confirming their heightened sensitivity to human disturbance (Nagy-Reis et al., 2017). Tapirs likely responded to agriculture in particular for several reasons: the presence of hunting, a decrease in food availability, and reduced access to water. Given that permanent households are prominent among the cacao and papaya farms and these households are isolated from both the closest settlement and the city, families rely upon the combination of their local crops and bushmeat to subsist. Tapirs are hunted with relative ease due to their heaviness and a method called “spotlighting” where their large eyeshine is spotted using flashlights at night. Additionally, clearcutting for agriculture has drastic, immediate effects on the floristic composition and vegetation structure at the forest edge and well into the remaining forest interior (Williams-Linera, 1990), decreasing interior species of the herbaceous layer that are vital to the tapir’s diet. Tapirs are semiaquatic and need consistent access to water bodies for various reasons including thermoregulation, to facilitate movement, and to escape predators (Burs et al., 2023). Drier and hotter forest edges cause increased forest desiccation and the disappearance of water bodies; canopy water loss has been known to extend over one kilometer into the forest in a landscape that has only been moderately fragmented (Briant et al., 2010). Matrix habitat or mixed-land use areas likely did not affect tapir occupancy because food and water availability remain high in these areas compared to landscapes of agriculture and forest fragments.
Due to their large home ranges and requirement for substantial contiguous areas to survive, jaguars are especially vulnerable to fragmentation and human development (Michalski & Peres, 2005; Zeilhofer et al., 2014). Our research shows that jaguars in the Las Piedras are using areas of mixed land-use outside of protected areas, but specifically avoiding cacao farms within the agricultural association that borders the LPCC. The agricultural association is predominantly made up of 5–20-hectare areas clearcut for cacao production, but oftentimes there are permanent households where domestic animals such as dogs, pigs, and chickens reside without fencing. One of several reasons that jaguar site use decreases in proximity to agriculture could be the higher likelihood of retaliation for livestock kills in these areas (Amador et al., 2013). Additionally, cacao farms likely do not provide sufficient vegetation cover and have lower occupancy of the jaguar’s main prey species, the lowland tapir. Mixed-use areas, which we defined as matrix habitat outside the protected LPCC, increased the site use probability of jaguars in our study area. Vehicles, hunting, and timber extraction were recorded at these sites, which were in closer proximity to human settlements, logging camps, and Brazil nut concessions. An increase in jaguar site use probability in these areas could be due to several factors: the extensive daily distance traveled by jaguars (McBride & Thompson, 2018), the use of habitual travel routes and paths of least resistance (Karanth & Nichols, 1998), their documented tolerance of human disturbance (e.g. ability to become more nocturnal in human-occupied areas) (Foster et al., 2010; Monette et al., 2020), and the relatively low level of human impact in these areas comparatively. Although these sites were outside of the protected corridor, the forest is generally intact and connected, and human activity is limited; therefore, jaguars still use these areas for navigation, at least to get from one zone of their range to another.
While most of our persecuted predator and game species showed a significant response to human impacts, the ocelot and the paca did not. Due to the extent to which ocelots are hunted (Valsecchi et al., 2023), usually in retaliation for livestock killings (Mena et al., 2021), we expected similar results to the jaguar with either distance from settlements or agriculture proving significant in affecting ocelot occupancy. Our results could indicate that ocelots are more capable of adapting to human disturbance; however, it could also be due to a lack of data from agricultural areas, as sites within 500 m of cacao or papaya agriculture only represented 12% of our total sites (in part due to camera theft near agricultural locations). This reduced sample size is likely causing us to miss patterns in species occupancy in relation to proximity to agriculture for not just ocelots but all of the species. Although the paca did not have a negative response to any human impact covariates, their significantly lower detection probability on human trails could represent an avoidance of humans at finer scales in response to hunting or could indicate they prefer smaller mammal trails. Additionally, paca are known to be a riverine species, and past studies have deployed camera traps within 100 m of a water source to effectively study their ecology (Figueroa-de-León et al., 2017). Therefore, the design of our study may be impeding our ability to detect patterns in the occupancy of paca given their habitat requirements and space use.
The Las Piedras River was a significant predictor of mammal occupancy across our study area. Distance from the closest river and vicinity to fresh water have been recorded to increase species occupancy in similar systems, within both the predator and prey guilds (Boron et al., 2019; Dias et al., 2019; Rich et al., 2017). The river and floodplain forest are crucial as mammal habitat; however, riverine habitat is also used by humans for the establishment of settlements and agriculture. The combination of abundant natural resources, transportation opportunities, and fertile soils make riverine habitats a primary choice for colonization in the Amazon rainforest (Lentz, 2000; Moran, 2007). Consequently, subsistence hunting is concentrated around farms and settlements and near the margins of rivers; distance from rivers has been used as a covariate to predict hunting intensity given it is a common access point for hunters (Espinosa et al., 2018; Whitworth et al., 2019). Riverine concessions in MDD should therefore receive prioritized protection in the face of further colonization due to the importance of rivers for mammal habitat.
Only two of the nine relatively non-persecuted mammals spatially avoided disturbed sites including the common opossum and green acouchi; in addition, the common opossum and Brazilian rabbit benefited from matrix habitat in our study area. The common opossum, although not persecuted for its meat, parts, or as a pet, has been known to be frequently killed by humans and dogs across its geographic range, which could explain its avoidance of areas with high land use (Vaughan & Hawkins, 1999). Common opossums also had a positive relationship with agricultural sites, likely due to the abundance of food (fruit, vegetables, and small domestic animals/ eggs), so their response to human disturbance varied. The green acouchi also avoided areas of high land use, which could be in response to human pressures like hunting; however, it could also be attributable to changes in community structure and interspecific competition. Populations of generalist rodents likely surged in matrix habitat (Suzán et al., 2008), increasing competition for food resources in human-modified areas, and pushing out the acouchi. The Brazilian rabbit increased in occupancy in areas of high land use and avoided intact forest within the private protected area; although there is little research on this particular species, rabbits in general are known to better cope with human disturbance and benefit from human infrastructure and resources (Bock et al., 2009).
By employing occupancy models and analyzing various ecological and anthropogenic covariates, our research sheds light on the impacts of human activities and their consequences for wildlife populations. Additionally, the methods developed in our study provide a means to detect the often subtle and overlooked process of defaunation, even in rapidly changing ecosystems like those in South America, by incorporating potential hunting access points (proximity to agriculture and settlements) into occupancy models. Our findings highlight the urgency of addressing deforestation and defaunation to prevent further ecosystem degradation. In some cases, like white-lipped peccary, we had no detections in areas with moderate levels human impact, indicating that even some amount of habitat destruction and hunting are fostering defaunation and the loss of ecological processes within the Las Piedras region. However, it is important to note that there are still opportunities for action and conservation interventions to mitigate defaunation in many areas as found that protected areas had higher occupancy probabilities for a number of prey species in our study. Protected areas, especially those bordering or utilized by human communities, can act important refugia for wildlife species from habitat loss and hunting (Boron et al., 2022; Lyra-Jorge et al., 2008). By identifying key indicator species and understanding their responses to human pressures, targeted conservation efforts can be implemented to ensure the long-term stability and functionality of these vital rainforest ecosystems across the globe.