418 E. Rios et al.
persist better in patches located (1) more distant from settlements, (2) in landscapes with few settlements, (3)in landscapes with high incidence of unpaved roads, (4)ina mosaic with high proportion of forest, cacao agroforests and farmland, and (5) more distant from other forest patches (Table 2). These outputs suggest that curassow persistence is more
affected by hunting pressure than habitat quality, because (1) the hunting pressure submodels presented higher ex- planatory power than habitat quality submodels, (2) the final models included four hunting pressure variables in contrast to only two habitat quality variables, and (3) hunt- ing pressure variables appeared in all models (e.g. distance from the focal forest patch to settlements) or in themajority of models (area occupied by settlements), whereas habitat quality variables appeared in only one final model.
Discussion
We used a variety of methods to gather information on fac- tors affecting the persistence of the red-billed curassow in 14 sites in southern Bahia, in the threatened Brazilian Atlantic forest. Although we are confident that this served our pur- pose of providing an insight into the relative roles of habi- tat change and hunting in influencing persistence of the species, additional, more consistent data would be helpful. This is a challenge for threatened species that occur at low densities (naturally or as a result of anthropogenic declines) in habitats where access can be difficult and detection rates are low. Nonetheless, a systematic approach to both gather- ing data and maximizing the value of data from planned and ongoing studies would yield significant benefits for in- forming management decisions in such situations (see also Grainger et al., 2017). Our findings suggest that the most important factor to
consider in conservation strategies for the red-billed curas- sow is hunting pressure. As predicted, red-billed curassows are more likely to persist in forest landscapes with low human density (i.e. forest patches further away from set- tlements). Several other cracids show similar patterns: the great curassow Crax rubra and crested guan Penelope pur- purascens were less likely to occupy densely settled areas in the Yucatán Peninsula, Mexico (Urquiza-Haas et al., 2009), the black curassow Crax alector exhibits high occu- pancy rates in forest patches unaffected by hunting pres- sure in central Amazonia (Benchimol & Peres, 2015), and the razor-billed curassow Mitu tuberosa, Spix’s guan Penelope jacquacu, blue-throated piping guan Pipile cumanensis and speckled chachalaca Ortalis guttata havemuch lower popula- tion densitieswithin 5kmof villages in the PeruvianAmazon (Begazo & Bodmer, 1998). We hypothesized that red-billed curassow persistence is
inversely related to the incidence of unpaved roads, be- cause roads facilitate access by hunters (Canale et al., 2012).
However, we found red-billed curassows are more likely to persist in landscapes with higher incidence of roads. One possible explanation is that curassows utilize roads to forage (Srbeck-Araujo et al., 2012), thereby increasing the chances of people recording them. We also found red-billed curas- sows more likely to persist in amosaic of forest, cacao agro- forest and farmland as long as the proportion of native forest cover is high. Cacao agroforests are known to support a high diversity of forest species when located near large forest remnants (Faria et al., 2007). Contrary to our expectations, we found that red-billed
curassows are more likely to persist in isolated forest patches (.1 km distant from others). However, these isolated forest patches are relatively large (. 3,700 ha) and located in land- scapes with a high proportion of forest cover (. 65%). Thus it is possible that curassows do not attempt to leave such patches. The few data available on dispersal of curassows suggest poor dispersal capability: no gap-crossing move- ments of bare-faced curassows Crax fasciolata were recorded in Amazonian forest patches (Lees & Peres, 2009) and none of 25 reintroduced red-billed curassows monitored over a 25-month period moved across .750 minopenareas (Bernardo, 2010). In our studied landscape, the minimum distance from the focal forest patch to another patch was 760 m, whichmay be toowide a gap to be crossed successfully (Table 2). If curassows attempt to cross such gaps, searching for areas with higher resource availability, they may be more vulnerable to natural predators, hunters and/or dogs. Because hunting pressure compromises curassow per-
sistence, future protected areas will serve the species better in regions with low human density. Reintroduction ini- tiatives for red-billed curassows (Bernardo & Locke, 2014) need to take this factor into account (Alves et al., 2017). Hunt- ing pressure (and the feasibility of reducing it) should be assessed at potential reintroduction sites before any such reintroductions proceed.
Acknowledgements We acknowledge Coordenação de Aperfeiçoa- mento de Pesquisa e Ensino Superior (CAPES) for a Master’s student- ship to ERS and post-doc studentship to CSSB, and Universidade Estadual do Sudoeste da Bahia- campus Jequié for logistical support.
Author contributions Study design: ER, CSSB; fieldwork: ER; data analysis: CSSB; writing: all authors.
Conflicts of interest None.
Ethical standards This research abided by the Oryx guidelines on ethical standards and was approved by the Ethics Committee of Uni- versidade Estadual do Sudoeste da Bahia—Brazil (CEUA n. 332013) and the Brazilian Environmental Agency (SISBIO-ICMBio n. 487391).
References
ALVAREZ, A.D. (2010) A Camera-Trapping Survey of the Endangered Red-Billed Curassow Crax blumenbachii in the Atlantic Rainforest,
Oryx, 2021, 55(3), 412–420 © The Author(s), 2020. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605319000711
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