Factors affecting culvert use by vertebrates along two stretches of road in southern Portugal |
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Authors: | Fernando Ascensão António Mira |
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Institution: | 1.Unidade de Biologia da Conserva??o, Departamento de Biologia,Universidade de évora,évora,Portugal |
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Abstract: | A major target for environmental managers when trying to minimise the road-barrier effect on wildlife is to improve permeability
to animal movements. Previous studies have demonstrated that drainage culverts are used by vertebrates, although knowledge
of the main influencing factors remains limited. The use of 34 culverts from two roads in southern Portugal, differing in
traffic volume, vehicle speeds and configuration, was evaluated by the analysis of terrestrial vertebrate footprint data (408
passage-operative days). Culvert crossings were related to various explanatory variables by means of canonical ordination
techniques. We recorded 901 complete crossings, corresponding to an average of 2.2 crossings/culvert/operative day. Thirteen
taxa were detected, all in more than one passage. Animal species included reptiles, small mammals, lagomorphs, carnivores
and domestic dogs and cats. Our results suggest that fencing might have a funnelling effect, directing larger animals toward
culverts. Also, vegetation covering culvert entrances seems to have a positive effect, particularly on genets; longer passages
with entrances far from the pavement were, apparently, avoided by smaller animals; a lower number of crossings was detected
on passages with detritus pits; the closest passages to urban areas are more often used by domestic species; forest-living
species favour passages with low, open land cover nearby; and smaller species, like lagomorphs and small mammals, appear to
use more culverts near the pavement, which probably reflects the importance of road verges as refuges for these species. Although
not used by all species present in the study area, constructing numerous passages of different sizes without detritus pits
and which are distributed along roads might be an important step in mitigating road fragmentation effects on animal populations. |
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Keywords: | Road ecology Culvert use Conservation Canonical ordination Vertebrates |
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