The effect of roads on edge permeability and movement patterns for small mammals: a case study with Montane Akodont
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Increased edge density is among the main negative effects of habitat loss and fragmentation. Roads are linear infrastructures that may promote barrier effects due to disturbance and mortality effects. We hypothesized that edges of habitat patches bordered by roads are less permeable than roadless edges.
We tested whether edge permeability and avoidance are influenced by the presence of paved and dirt roads bordering habitat patches, relatively to roadless edges.
We translocated 55 montane akodonts (Akodon montensis) from the interior of vegetation remnants to their edges, and tracked fine-scale movements using spool-and-line devices. Edges were bordered by dirt roads (n = 12 mice), paved roads (n = 21) or were not bordered by roads (n = 22). We assessed edge permeability by comparing the number of tracks with crossings, and by comparing the empirical data to simulated correlated random walks. We also assessed edge avoidance by comparing the net direction travelled and net displacement from edge.
No edge crossings were recorded in roaded edges, whereas 36% of tracks in roadless edges crossed the edge at least once. Simulations indicated a significantly lower permeability of roaded edges, while the observed number of crossings in roadless edges was within the expected range. We found no evidence of higher avoidance of roaded edges, as both net direction travelled and displacement were similar across edge types.
Roads decreased edge permeability for the montane akodont. This is likely to increase population isolation among vegetation remnants by reducing the structural connectivity in the already fragmented landscape.
KeywordsBrazil Cerrado Landscape connectivity Road barrier effect Spool-and-line device
We are grateful for the financial support provided by FAPEMIG (Process CRA–PPM-00139-14/453 and CRA–APQ-03868-10), CNPq (Process 303509/2012-0), Fundação Grupo Boticário Process (0945-20122), and Tropical Forest Conservation Act – TFCA (through Fundo Brasileiro para Biodiversidade – FUNBIO). FA was partially funded by a postdoc grant from FAPEMIG/CAPES (CRA.BPD.00164/14) and a postdoc grant from Infraestruturas de Portugal Biodiversity Chair - CIBIO - Research Center in Biodiversity and Genetic Resources (BPD-REFER-NC). This study and its procedures were approved by the Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais - IBAMA/SISBIO (license No. 33840-1). We would like to thank Ricardo Pita, Sasha Vasconcelos and two anonymous reviewers for suggestions on early versions of this manuscript. We are also grateful to Ramon Gomes de Carvalho and Cristiane Moreira Mesquita for logistical support.
Compliance with ethical standards
Conflict of interest
The authors have no conflict of interest to declare.
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