Elsevier

Biological Conservation

Volume 208, April 2017, Pages 29-39
Biological Conservation

Citizen scientists help unravel the nature of cattle impacts on native mammals and birds visiting fruiting trees in Brazil's southern Pantanal

https://doi.org/10.1016/j.biocon.2016.09.010Get rights and content

Highlights

  • Studied cattle impact on native forest fauna visiting fruiting trees in Pantanal.

  • Diversity of fruiting trees and visiting fauna greater in low cattle-impact areas.

  • Five frugivores and 1 carnivore were indicators of low cattle-impact conditions.

  • Responses of T. pecari and C. fasciolata to cattle impact were fruit-dependent.

  • Novel cattle management needed to curb losses of Pantanal forest biodiversity.

Abstract

We used 2 years of camera-trap surveys conducted by citizen scientists to compare native mammal and bird visits to dominant fruiting-tree species in low and high cattle-impact areas of rarely-flooded “cordilheira” forests in the Brazilian Pantanal. Monthly fruit censuses showed greater diversity of fruiting-tree species in low cattle-impact areas. Citizen scientists documented 29 native mammal and bird species among 5639 photo records obtained at fruiting trees. Analyses of 3 sets of camera-trap samples comprising: (1) only Attalea phalerata palms, (2) all ten dominant fruiting-tree species, and (3) all except a species with a highly-valued fruit and an unusual distribution, showed that faunal composition in low cattle-impact areas was significantly different and more diverse compared to that in high cattle-impact areas. Long-term cattle-related alterations of forest vegetation and short-term fruit depletion and interference by cattle explained faunal differences. While 5 frugivores and 1 carnivore were consistent indicators of low cattle-impact conditions, the value of 2 other frugivores (Tayassu pecari and Crax fasciolata) as indicators of cattle impact varied depending on fruit-species nutritive value, timing, and distribution. Improved cattle management is needed to prevent additional loss of forest biodiversity.

Introduction

Cattle rearing operations affect native fauna and flora, species interactions, and ecological communities across a wide range of climates, geographic regions, and environments (Bock and Bock, 1999, Chaikina and Ruckstuhl, 2006, Elliott and Barrett, 1985, Moser and Witmer, 2000, Shepherd and Ditgen, 2005). Negative impacts on native fauna can result from habitat and vegetation alterations, diet overlap with cattle, and alterations in behavior or habitat use associated with avoidance of cattle (Chaikina and Ruckstuhl, 2006, Elliott and Barrett, 1985, Moser and Witmer, 2000, Shepherd and Ditgen, 2005).

In the Brazilian tropics, cattle grazed in naturally-open rangelands or in areas that were deforested and converted to planted exotic, i.e., non-native, grass pastures (hereafter called planted pastures) also forage and seek shelter in nearby forests. Therefore, in addition to impacts on native grazers and browsers characteristic of open habitats, they potentially affect forest species, like ground-dwelling frugivores, which are the focus of this study. Frugivorous animals comprise a large part of vertebrate community biomass in tropical regions and are important seed dispersal agents, contributing to the dynamics and structure of forests (Jordano, 2000, Silman et al., 2003, Terborgh, 1983, Terborgh, 1986). Similar to cattle impacts on grazers and browsers, short-term indirect and direct effects on native frugivorous animals potentially include overlap in use of fruit resources and/or alterations of behavior and habitat use, e.g., if native fauna avoid areas where cattle congregate, or shift their spatial or temporal feeding patterns in the presence of cattle. Long-term indirect impacts of cattle on frugivores potentially include vegetation and habitat alterations caused by foraging and trampling of forest understory and shifts in seed dispersal and predation (Johnson et al., 1997, Nunes et al., 2008, Santos, 2011, Shepherd and Ditgen, 2005, Tomas et al., 2009).

The Pantanal of Bolivia, Paraguay, and the Mato Grosso region of central-western Brazil is an England + Wales-sized alluvial plain (150,500 km2) that drains the upper Paraguay river basin and forms one of the largest seasonal tropical wetland systems in the world (Hamilton et al., 1996, Junk et al., 2006, Nunes da Cunha et al., 2014, Padovani, 2010). It supports a rich variety and abundance of wildlife, is recognized internationally as a region of conservation importance, and is an important production area that has supported extensive cattle ranching operations since the late 1800s (Junk et al., 2006, Mazza et al., 1994, Nunes da Cunha et al., 2014, Santos et al., 2002, Santos et al., 2008). The Pantanal is one of the few places in the American tropics where a wide variety of wildlife are easily observed. For this reason, ecotourism is popular in the Pantanal, and has been adopted by a number of property owners as an alternative economic activity to replace or supplement cattle ranching. North American and European tourists interested in citizen-scientist opportunities are drawn to the region, and as reported for other studies (e.g., McKinley et al., 2017-this issue) have been integral to the successful collection of field data described in this article.

Because > 95% of the Brazilian Pantanal consists of privately-owned ranches called “fazendas”, the region has been (and continues to be) vulnerable to development trends initiated in the 1960s that decrease the environmental sustainability of ranch properties. These trends have included the introduction of harmful ranching practices, most significantly deforestation, conversion of natural habitat to planted pasture, and subsequent intensification of cattle operations (Santos et al., 2008, Silva et al., 1999). So, in addition to impacts and probable species losses from deforestation and conversions, the remaining native fauna and flora have been exposed to increased levels of cattle activity associated with the expansion of planted pasture. By 2008 (the period of this study), approximately 13% of the natural vegetation cover had been altered in the Pantanal (15% by 2014; Instituto SOS Pantanal and WWF-Brasil, 2015). Forest formations called “cordilheiras”, which were the focus of this study, have unfortunately been disproportionately targeted for deforestation and conversions in the Pantanal, because they occupy areas above typical peak flood levels and as a result are preferred locations for establishing the less flood-resistant exotic-grass monocultures (Silva et al., 1999).

Recent studies in the southern Pantanal, have shown that cattle-related impacts associated with both traditional and intensive (i.e., requiring deforestation and conversion to planted pasture) ranching practices may have negative consequences for forest flora and fauna, e.g., loss and simplification of forest understory vegetation (Nunes et al., 2008, Santos, 2011), alteration of forest structure and succession (Santos, 2011, Tomas et al., 2009), loss of insectivorous birds associated with forest litter (Nunes, 2009), loss of nesting cavity trees, Sterculia apetala, for threatened hyacinth macaws, Anodorhynchus hyacinthinus (Guedes et al., 2006), and altered range area and use by a wide-ranging prevalent frugivore, the white-lipped peccary, Tayassu pecari (Keuroghlian et al., 2015).

Our main objective was to determine whether native ground-dwelling mammalian and avian species visiting freshly-fallen fruits at trees in Pantanal forests were affected by cattle-related, or cattle-operation related, impacts. To that end, we relied on citizen scientists to conduct camera-trap surveys of forest fauna visiting fruiting trees in areas exposed to different levels of cattle activity. Using the data compiled from photo records by citizen scientists, we performed a range of analyses to evaluate impacts on faunal assemblages. Fruiting trees were ideal locations for monitoring the interactions between cattle and a wide range of native fauna, because they, like watering holes on dry savannas, are natural aggregation sites for fauna (Wemmer et al., 1996). A secondary objective of the study was to investigate the potential wider application of the procedures developed for citizen scientists as tools for evaluating and monitoring other types of environmental impacts in regional forests.

Section snippets

Study area

We focused our investigation in the upper Rio Negro subregion of the southern Pantanal (Padovani, 2010), Município de Aquidauana, Mato Grosso do Sul, Brazil (Fig. 1). Native vegetation in the region, as is true for many parts of the Pantanal, is a complex mixture of aquatic, savanna, and forest formations that are strongly influenced by annual and multi-annual flood cycles, consequent moisture conditions, climatic and edaphic factors, and human alterations of the landscape (Nunes da Cunha et

Dominant fruiting-tree species surveyed

From January 2007 through December 2008, citizen scientists conducted 35 camera-trap surveys to monitor animal visits to dominant fruiting-tree species in “cordilheira” forests. Table 1 shows the ten species of dominant fruiting trees surveyed, months when fruit fall occurred and surveys were conducted, sample sizes of camera-trap surveys in low and high cattle-impact areas, mean Sørensen dissimilarity of recorded animal assemblages relative to assemblages recorded at other fruiting-tree

Cattle impacts on dominant fruiting-tree species of “cordilheira” forests

Our systematic searches of “cordilheira” forests with citizen scientists suggested that a majority of dominant fruiting-tree species had uneven distributions, and/or fruiting patterns, in relation to the degree of cattle-impact, and that overall fruiting-tree diversity was lower in areas of high cattle-impact. For example, we only found fruiting B. mattogrossensis trees in areas of high cattle-impact, and fruiting P. heptaphyllum trees in areas of low cattle-impact. These results were

Acknowledgements

This project was funded by Wildlife Conservation Society-Brazil, Blue Moon Fund, Wallace Global Fund, Fundação Manoel de Barros, and The Waterloo Foundation. We thank “Global Ecotours” teachers: J. Wilford, E. Kinzly, M. Simonds, and C. Caprio, and their students for their enthusiasm, support, and friendship. We are also grateful for the hard work of our Brazilian colleagues that helped gather and organize the data: Perola Lopes A. Sanabria, Celso Vicente da Silva, Divino Aparecido Elias, and

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