Kirsten M. Silvius

Large-Scale Environmental Monitoring by Indigenous Peoples

Changes in vertebrate populations in tropical ecosystems are often understood to occur at large spatial and temporal scales. Understanding these dynamics and developing management responses when they are affected by hunting and land-use change require research and monitoring at large spatial scales. Data collection at such scales can be accomplished only through the participation of locally resident nonscientists. To assess the feasibility of rigorous, scientifically valid data collection under such conditions, we describe the design and management of a three-year study of the relationships among socioeconomic factors, hunting behavior, and wildlife population dynamics in a 48,000-square-kilometer, predominantly indigenous region of Amazonia. All of the data in the study were collected by locally recruited and trained indigenous technicians. We describe data collection and verification systems adapted to the culturally influenced data-collection practices of these technicians and propose protocols and improvements on our methodology to guide future large-scale research-and-monitoring projects.

Space, Place, and Hunting Patterns among Indigenous Peoples of the Guyanese Rupununi Region

Hunting remains an important subsistence activity for many indigenous peoples of the Neotropics. This paper describes indigenous hunting patterns using a mixed-methods approach in southern Guyana from a space and place perspective that takes into account both biophysical and cultural/spiritual factors. Findings confirm those of others, that distance from community, mediated by characteristics of the biophysical environment, impacts where hunters go. Mapping of the spiritual landscape, however, demonstrates that sense of place is also important. This paper argues that researchers and managers should be careful to incorporate both the local environmental and cultural/spiritual contexts in studies that inform biodiversity and sustainable resource-use management.

Agent-based modeling of hunting and subsistence agriculture on indigenous lands: Understanding interactions between social and ecological systems

Indigenous people of the Rupununi region of Amazonian Guyana interact with their natural environment through hunting and subsistence agriculture. To date the sustainability of indigenous livelihoods has been analyzed by modeling either hunting or forest clearing. Here we develop a holistic model framework with agent-based modeling to examine interactions between demographic growth, hunting, subsistence agriculture, land cover change, and animal population in the Rupununi. We use an extensive field dataset from social surveys, animal observation records and hunting kill locations along with satellite images. The model exhibits feedback loops between a growing human population and depletion of local natural resources. Our model can reproduce the population size of two different villages along with landscape patterns without further calibration. Our model can be used for understanding the conditions of sustainability for indigenous communities relying on subsistence agriculture and hunting, and for scenario analyses to examine the implications of external interventions.

Avian Consumers of Cardon Fruits (Stenocereus griseus: Cactaceae) on Margarita Island, Venezuela1

The fruiting phenology and avian consumer set of card6n cactus (Stenocereus griseus) fruits were observed on the semiarid Macanao Peninsula of Margarita Island, Venezuela. The card6n population had two peak fruiting seasons (late May-early June and late August-early September) which correspond to the local rainy seasons, but many plants also produce low numbers of fruits throughout the year. Fruits were fed on continuously by a variety of consumers for several days while still attached to the plant. The avian consumer set induded 14 species and was dominated by two species of parrots (Aratinga pertinfax and the endangered Amazona barbadensis). Most of the avian consumers are omnivores that indude variable amounts of fruit in their diet. Feeding observations in the wild, captive feeding trials, and seed germination trials indicated that six of the bird species are seed predators, six act as seed dispersers, and two are neutral with respect to seed survival. Bats fed on the fruits but were unable to open the husks, and thus must rely on naturally dehisced fruits or fruits opened by psittacines.

Line Transect Surveys Underdetect Terrestrial Mammals: Implications for the Sustainability of Subsistence Hunting

Conservation of Neotropical game species must take into account the livelihood and food security needs of local human populations. Hunting management decisions should therefore rely on abundance and distribution data that are as representative as possible of true population sizes and dynamics. We simultaneously applied a commonly used encounter-based method and an infrequently used sign-based method to estimate hunted vertebrate abundance in a 48,000-km2 indigenous landscape in southern Guyana. Diurnal direct encounter data collected during three years along 216, four-kilometer -long transects consistently under-detected many diurnal and nocturnal mammal species readily detected through sign. Of 32 species analyzed, 31 were detected by both methods; however, encounters did not detect one and under-detected another 12 of the most heavily hunted species relative to sign, while sign under-detected 12 never or rarely collected species relative to encounters. The six most important game animals in the region, all ungulates, were not encountered at 11–40% of village and control sites or on 29–72% of transects where they were detected by sign. Using the sign methodology, we find that tapirs, one of the terrestrial vertebrates considered most sensitive to overexploitation, are present at many sites where they were never visually detected during distance sampling. We find that this is true for many other species as well. These high rates of under-detection suggest that behavioral changes in hunted populations may affect apparent occurrence and abundance of these populations. Accumulation curves (detection of species on transects) were much steeper for sign for 12 of 16 hunted species than for encounters, but that pattern was reversed for 12 of 16 species unhunted in our area. We conclude that collection of sign data is an efficient and effective method of monitoring hunted vertebrate populations that complements encounter and camera-trapping methods in areas impacted by hunting. Sign surveys may be the most viable method for large-scale, management-oriented studies in remote areas, particularly those focused on community-based wildlife management.

Mammal diversity influences the carbon cycle through trophic interactions in the Amazon

Biodiversity affects many ecosystem functions and services, including carbon cycling and retention. While it is known that the efficiency of carbon capture and biomass production by ecological communities increases with species diversity, the role of vertebrate animals in the carbon cycle remains undocumented. Here, we use an extensive dataset collected in a high-diversity Amazonian system to parse out the relationship between animal and plant species richness, feeding interactions, tree biomass and carbon concentrations in soil. Mammal and tree species richness is positively related to tree biomass and carbon concentration in soil—and the relationship is mediated by organic remains produced by vertebrate feeding events. Our research advances knowledge of the links between biodiversity and carbon cycling and storage, supporting the view that whole community complexity—including vertebrate richness and trophic interactions—drives ecosystem function in tropical systems. Securing animal and plant diversity while protecting landscape integrity will contribute to soil nutrient content and carbon retention in the biosphere.A high-diversity Amazonian system reveals the influence of mammalian diversity on the carbon cycle, mediated through vertebrate feeding events.

Author Correction: Mammal diversity influences the carbon cycle through trophic interactions in the Amazon

In the version of this Article originally published, the surname of Ted K. Raab was misspelt. This error has now been corrected in all versions of the Article.