The titi monkey in fragmented landscapes 921
et al., 2017); (2) as our results show, there is a positive rela- tionship between the enhanced vegetation index and the model species occurrence; and (3) such indices can be ob- tained from freely available satellite images. Connectivity of arboreal mammal populations in frag-
mented landscapes may be maintained by dispersal events based on opportunities for visualization of surrounding habitat patches, as indicated by the positive effect of patch visibility on the occurrence of our model species and of C. personatus (see Silva et al., 2015). Patch visibility offers a new way to evaluate connectivity between populations of arbor- eal mammals in fragmented landscapes and its importance in explaining species occurrence should be further explored using other taxa and landscapes. The use of spatial memory can also play a role in dispersal events between forest frag- ments but, to our knowledge, this issue has not yet been investigated. Considering the positive effect of patch visibility, which
incorporates visibility modulated by landscape relief and linear distance, on the occurrence of our model species, it is likely that such arboreal mammals disperse across pas- tures between visible forest fragments that are close to each other (see also Moraes et al., 2018). Traveling over short distances between visible forest fragments, rather than dispersing over long distances may be a result of the high predation pressure arboreal mammals are exposed to during dispersal across open areas (Vuren & Armitage, 1994; Sakai & Noon, 1997). Callicebus melanochir may be persisting in the study area
as a result of metapopulation dynamics, with the large frag- ments being sources and the nearby smaller fragments that are visible being sinks. As arboreal mammals, we expect that isolated populations of C. melanochir have gone extinct in the study area as a result of the Allee effect (Stephens et al., 1999), genetic factors and stochastic events, consider- ing that three titi monkey generations (Veiga et al., 2011) have passed since the stabilization of forest conversion into pastures in this region in the 1990s (Coimbra-Filho & Câmara, 1996). Our study shows that forest area is the strongest predictor
of the occurrence of our model species, C. melanochir.We also found positive effects of forest quality, visibility and landscape connectivity on the species. We recommend that further research should consider the effect of forest quality on the occurrence of arboreal mammals in tropical forest hotspots and we encourage the use of remotely sensed vegetation indices as proxies of habitat quality. The adop- tion of the visibility metric may offer insights on the occur- rence of arboreal mammals and on the connectivity of pop- ulations. In addition to forest area, the use of forest quality and visibility, and landscape connectivity, can improve detection of arboreal mammal populations and also aid in the selection of fragments and the types of actions for spe- cies conservation at local and regional scales in fragmented
landscapes in tropical forest hotspots. Large remnants of tropical forest hotspots are scarce and therefore we require baseline data to support alternative conservation actions and management in small fragments.
Acknowledgements This study was financed in part by the Coordenação Nacional de Desenvolvimento Científico e Tecnológico (140039/2018-1; 153423/2016-1; 312045/2013-1; 312292/2016-3), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (001, 527091; 20131509; PROCAD 88881.068425/2014-0, PNPD 88882.306330/2018-01), Fundação de Amparo à Pesquisa do Estado do Amazonas, Fundação de Amparo à Ciência e Tecnologia de Pernambuco (BFP-0149-2.05/19) and Fundação de Amparo à Pesquisa do Estado de São Paulo (2013/50421-2). We thank R.C. Printes for providing the recording of a C. barbarabrownae long-call and for valuable comments on surveying titi monkey, M. Lapenta, Rubi and Juni for field assistance, the people who granted access to their lands, Martin Fisher for his critique, and two anonymous re- viewers for their valuable comments.
Author contributions Conception: RC-A, ALR, MCR; data collec- tion design, fieldwork: RC-A; mapping and quantification of landscape structure indices: ALR, FM; data analysis: ALR, MCR, FM; writing: RC-A, with input from ALR, JPS-A, TH, MCR.
Conflicts of interest None.
Ethical standards Fieldwork followed the code of best practice of the International Society of Primatologists, and otherwise abided by the Oryx guidelines on ethical standards.
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Oryx, 2021, 55(6), 916–923 © The Author(s), 2021. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605319001522
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