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Browsing by Author "Silvius, Kirsten M."

Now showing 1 - 4 of 4
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    Fishes and cowboy boots: An optimistic view
    Lima Constantino, Pedro de Araujo; Silvius, Kirsten M.; Alvarenga, Fernanda; Buck Silva, Cristina Isis; Kurihara, Leonardo; Rossoni, Felipe; Torres, Ana Claudia; Dias da Costa, Antonio Adevaldo; Correa Mota, Sara Quizia; Nunes Rocha, Joao da Mata; Silva Santos, Bruna De Vita; Campos-Silva, Joao Vitor (2020-09)
    The community-based management of Arapaima gigas for sustainable commercial use allows that wild fish legally harvested in the Brazilian Amazon supply the demand for exotic leather in the US, supporting the conservation of the forest and providing income for fishers communities if based in fair-trade. We provide a more optimistic view than Heinrich et al. (2019) on the effects of international trade of arapaima leather in the conservation of the species in Brazil.
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    Line Transect Surveys Underdetect Terrestrial Mammals: Implications for the Sustainability of Subsistence Hunting
    Fragoso, Jose M. V.; Levi, Taal; Oliveira, Luiz F. B.; Luzar, Jeffrey B.; Overman, Han; Read, Jane M.; Silvius, Kirsten M. (PLOS, 2016-04-13)
    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.
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    Mammal and tree diversity accumulate different types of soil organic matter in the northern Amazon
    Losada, Maria; Martinez, Antonio M.; Silvius, Kirsten M.; Varela, Sara; Raab, Ted K.; Fragoso, Jose M. V.; Sobral, Mar (Cell Press, 2023-03)
    Diversity of plants and animals influence soil carbon through their contributions to soil organic matter (SOM). However, we do not know whether mammal and tree communities affect SOM composition in the same manner. This question is relevant because not all forms of carbon are equally resistant to mineralization by microbes and thus, relevant to carbon storage. We analyzed the elemental and molecular composition of 401 soil samples, with relation to the species richness of 83 mammal and tree communities at a landscape scale across 4.8 million hectares in the northern Amazon. We found opposite effects of mammal and tree richness over SOM composition. Mammal diversity is related to SOM rich in nitrogen, sulfur and iron whereas tree diversity is related to SOM rich in aliphatic and carbonyl compounds. These results help us to better understand the role of biodiversity in the carbon cycle and its implications for climate change mitigation.
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    Visual encounters on line transect surveys under-detect carnivore species: Implications for assessing distribution and conservation status
    Fragoso, Jose M. V.; Goncalves, Fernando; Oliveira, Luiz F. B.; Overman, Han; Levi, Taal; Silvius, Kirsten M. (2019-10-30)
    We compared the distribution and occurrence of 15 carnivore species with data collected monthly over three years by trained native trackers using both sign surveys and an encounter-based, visual-distance method in a well-preserved region of southern Guyana (Amazon / Guiana Shield). We found that a rigorously applied sign-based method was sufficient to describe the status of most carnivore species populations, including rare species such as jaguar and bush dog. We also found that even when accumulation curves for direct visual encounter data reached an asymptote, customarily an indication that sufficient sampling has occurred to describe populations, animal occurrence and distribution were grossly underestimated relative to the results of sign data. While other researchers have also found that sign are better than encounters or camera traps for large felids, our results are important in documenting the failure of even intensive levels of effort to raise encounter rates sufficiently to enable statistical analysis, and in describing the relationship between encounter and sign data for an entire community of carnivores including felids, canids, procyonids, and mustelids.