António Mira

How long do the dead survive on the road? Carcass persistence probability and implications for road-kill monitoring surveys

Background Road mortality is probably the best-known and visible impact of roads upon wildlife. Although several factors influence road-kill counts, carcass persistence time is considered the most important determinant underlying underestimates of road mortality. The present study aims to describe and model carcass persistence variability on the road for different taxonomic groups under different environmental conditions throughout the year; and also to assess the effect of sampling frequency on the relative variation in road-kill estimates registered within a survey. Methodology/Principal Findings Daily surveys of road-killed vertebrates were conducted over one year along four road sections with different traffic volumes. Survival analysis was then used to i) describe carcass persistence timings for overall and for specific animal groups; ii) assess optimal sampling designs according to research objectives; and iii) model the influence of road, animal and weather factors on carcass persistence probabilities. Most animal carcasses persisted on the road for the first day only, with some groups disappearing at very high rates. The advisable periodicity of road monitoring that minimizes bias in road mortality estimates is daily monitoring for bats (in the morning) and lizards (in the afternoon), daily monitoring for toads, small birds, small mammals, snakes, salamanders, and lagomorphs; 1 day-interval (alternate days) for large birds, birds of prey, hedgehogs, and freshwater turtles; and 2 day-interval for carnivores. Multiple factors influenced the persistence probabilities of vertebrate carcasses on the road. Overall, the persistence was much lower for small animals, on roads with lower traffic volumes, for carcasses located on road lanes, and during humid conditions and high temperatures during the wet season and dry seasons, respectively. Conclusion/Significance The guidance given here on monitoring frequencies is particularly relevant to provide conservation and transportation agencies with accurate numbers of road-kills, realistic mitigation measures, and detailed designs for road monitoring programs.

Factors affecting culvert use by vertebrates along two stretches of road in southern Portugal

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.

Comparing annual vertebrate road kills over two time periods, 9 years apart: a case study in Mediterranean farmland

We surveyed road kills occurring along a 26-km stretch of a major national road (Portugal) in two different years: 1996 and 2005. For analysis purposes, we divided the data into seven vertebrate groups: amphibians, reptiles, carnivores, prey mammals (shrews, moles, rodents, rabbits and hares), hedgehogs, owls and passerines. Main factors influencing vertebrate road casualties were evaluated using redundancy analysis and variance partitioning techniques, focusing on three sets of variables: land cover, landscape metrics and spatial location. We also took into account meteorological conditions and changes in traffic intensity specific to each of the surveyed years. The percentage of variance explained by the explanatory variables was greater in 1996 (67.5%) than in 2005 (48.1%). Many variables influencing road kill incidence were common to both years. The most significantly associated factor was the distance to the Natural Park of Serra de São Mamede (NPSSM): road kills decreased steadily as our survey moved south, away from the NPSSM border. Moreover, an increased incidence of road losses occurred in forested areas, such as montado and traditional olive groves. As 2005 was a climatically drier year, additional variance factors became prominent, including the distance to water reservoirs, suggesting a greater influence of water availability. Traffic flow increased by almost 150% from 1996 to 2005, which may explain the overall increase in road kills, with the notable exception of the amphibian group, whose road fatalities incidences decreased approximately sixfold. We expect that our survey will provide a comprehensive understanding of the most critical factors currently influencing vertebrate road fatalities and aid in improving the effectiveness of mitigation measures to reduce them.

Fine-scale population genetic structure and short-range sex-biased dispersal in a solitary carnivore, Lutra lutra

Abstract The genetic structure of animal populations is influenced by, among other factors, dispersal and relatedness. Limited dispersal may cause local spatial restrictions in gene flow, which can have important management and conservation implications. We used radiotracking and genetic data to verify the existence of a spatial structure in relatedness within a resident native Eurasian otter (Lutra lutra) population at a fine spatio-temporal scale, and to better understand dispersal in this species. We obtained 51 individual genotypes from 65 biological samples collected from 2007 to 2010 in an area of southern Portugal of 1,125 km2. In addition, we radiotracked 7 (2 female, 5 male) young otters. Relatedness estimates and geographic distances were inversely related in females, whereas the relationship was not significant in males. Among the tracked subadult animals, only males dispersed, covering on average a distance of 21 km (SD = 6 km; range: 11–25 km). Both genetic and field data therefore revealed male-biased dispersal and suggested female philopatry. The observed overall pattern of genetic structuring was up to a scale of 21 km, although no putative landscape barriers were present. These findings concur with the few others previously available, indicating how restricted contemporary gene flow may occur at fine spatiotemporal scales within continuous carnivore populations, and can therefore constitute a cryptic cause of risk (being driven by mechanisms not necessarily related to the movement capabilities of the species), adding complexity to the conservation and management of these animals.

Vegetation analysis in colonies of an endangered rodent, the Cabrera vole (Microtus cabrerae), in southern Portugal

The Cabrera vole (Microtus cabrerae) is a threatened rodent endemic in the Iberian Peninsula with a patchy distribution and specific microhabitat requirements. This aim of this study was to document the composition of plant communities in habitats of Cabrera vole colonies in southern Portugal. Differences observed in plant species composition were also compared with vegetation structure, taxonomic and life form groups, species and group diversity, disturbance, topography and soil properties. Vegetation was sampled between March and July 2004, in 26 colonies occurring in five geographical areas. Grasses were the most abundant, common and diverse family in the colonies, and the perennial grass Agrostis castellana was present in 92% of colonies, with a mean cover of 16% of the site. Other frequently occurring species were Briza maxima (85%), Vulpia myuros (85%), Gaudinia fragilis (81%), Leontodon spp. (81%), Avena barbata (77%), Bromus hordeaceus (77%) and Tolpis barbata (77%). Colonies were classified in eight vegetation groups that included meadows, tall perennial grasslands, manured meadows with tall sedges, annual grasslands and ruderal and nitrophilous grasslands. Main gradients associated with composition differences were grass richness, annual and perennial grass cover, vegetation structure (herbaceous vegetation height), soil properties (texture and moisture), disturbance (ruderal species) and colony dimensions (area). Results suggest that the Cabrera vole is able to exploit a wide variety of grasslands, with a varying degree of ecological disturbance. Meadows and perennial grassland communities seem to be higher-quality microhabitats for voles.

Major roads have a negative impact on the Tawny Owl Strix aluco and the Little Owl Athene noctua populations

Abstract. The increasing road networks threaten ecosystems by direct effects such as increased mortality due to collision with vehicles and by various indirect effects leading to road avoidance. We censused Tawny Owls Strix aluco and Little Owls Athene noctua in 2005, 2007 and 2009 in a rural landscape in Southern Portugal in order to study the effects of roads and habitat characteristics on Tawny Owl density and Little Owl presence. The presence of both owl species in the 70 census locations was coherent among years. Our results showed that Tawny Owl density near major roads was lower, with the negative effects extending possibly up to 2 km. The probability of Little Owl presence was also negatively affected by the proximity to major roads. The negative effects of roads were significant even considering habitat preferences and spatial autocorrelation, which had the most marked effect on the density or presence of both owls. The reduced occupancy by Tawny Owls and Little Owls of habitats near major roads may be caused by several factors, including increased mortality, disturbance caused by high traffic density, and increased fragmentation. Traffic noise in particular may affect intra-specific communication and hunting efficiency. Consequently, habitat near roads may represent lower-quality territories for owls.

The influence of human, livestock, and ecological features on the occurrence of genet (Genetta genetta): a case study on Mediterranean farmland

We have studied the relationship between occurrence patterns of the genet (Genetta genetta) and ecological, human, and livestock descriptors at the Monfurado Natura 2000 Site in southern Portugal. An information–theoretical model comparison (ITMC) was used to select the best models to explain the presence of the species, using data from 36 habitat patches. Variables that were included in the best models then were used in a variation partitioning procedure to determine the relative influence of each variable set on the presence of the genet. When considered together, all the variables captured 56.5% of the variance in genet occurrence within the study area. The set of ecological variables accounted for most of the explained variance (pure effect: 30.3%). In the best ecological model, the occurrence of the genet was positively related to the density of trees and shrubs in the dominant agro–silvo–pastoral system (montado), to soil organic matter, and to Shannon’s index of vertical vegetation diversity. Human influence factors (pure effect: 4.8%) highlighted the negative relationship between the presence of the genet and the proportion of game-estate areas. The group of livestock variables (pure effect: 8.5%) revealed that intermediate levels of grazing may promote the occurrence of the genet. Our results highlight the importance of variables directly related to agricultural management, and are meaningful because they allow for the prioritization of management decisions. In particular, the results draw attention to soil organic matter and grazing by sheep, which are important factors in soil conservation practices.

Relative Effects of Road Risk, Habitat Suitability, and Connectivity on Wildlife Roadkills: The Case of Tawny Owls (Strix aluco)

Background Despite its importance for reducing wildlife-vehicle collisions, there is still incomplete understanding of factors responsible for high road mortality. In particular, few empirical studies examined the idea that spatial variation in roadkills is influenced by a complex interplay between road-related factors, and species-specific habitat quality and landscape connectivity. Methodology/Principal Findings In this study we addressed this issue, using a 7-year dataset of tawny owl (Strix aluco) roadkills recorded along 37 km of road in southern Portugal. We used a multi-species roadkill index as a surrogate of intrinsic road risk, and we used a Maxent distribution model to estimate habitat suitability. Landscape connectivity was estimated from least-cost paths between tawny owl territories, using habitat suitability as a resistance surface. We defined 10 alternative scenarios to compute connectivity, based on variation in potential movement patterns according to territory quality and dispersal distance thresholds. Hierarchical partitioning of a regression model indicated that independent variation in tawny owl roadkills was explained primarily by the roadkill index (70.5%) and, to a much lesser extent, by landscape connectivity (26.2%), while habitat suitability had minor effects (3.3%). Analysis of connectivity scenarios suggested that owl roadkills were primarily related to short range movements (<5 km) between high quality territories. Tawny owl roadkills were spatially autocorrelated, but the introduction of spatial filters in the regression model did not change the type and relative contribution of environmental variables. Conclusions Overall, results suggest that road-related factors may have a dominant influence on roadkill patterns, particularly in areas like ours where habitat quality and landscape connectivity are globally high for the study species. Nevertheless, the study supported the view that functional connectivity should be incorporated whenever possible in roadkill models, as it may greatly increase their power to predict the location of roadkill hotspots.

A low-cost GPS GSM/GPRS telemetry system: performance in stationary field tests and preliminary data on wild otters (Lutra lutra).

Background Despite the increasing worldwide use of global positioning system (GPS) telemetry in wildlife research, it has never been tested on any freshwater diving animal or in the peculiar conditions of the riparian habitat, despite this latter being one of the most important habitat types for many animal taxa. Moreover, in most cases, the GPS devices used have been commercial and expensive, limiting their use in low-budget projects. Methodology/Principal Findings We have developed a low-cost, easily constructed GPS GSM/GPRS (Global System for Mobile Communications/General Packet Radio Service) and examined its performance in stationary tests, by assessing the influence of different habitat types, including the riparian, as well as water submersion and certain climatic and environmental variables on GPS fix-success rate and accuracy. We then tested the GPS on wild diving animals, applying it, for the first time, to an otter species (Lutra lutra). The rate of locations acquired during the stationary tests reached 63.2%, with an average location error of 8.94 m (SD = 8.55). GPS performance in riparian habitats was principally affected by water submersion and secondarily by GPS inclination and position within the riverbed. Temporal and spatial correlations of location estimates accounted for some variation in the data sets. GPS-tagged otters also provided accurate locations and an even higher GPS fix-success rate (68.2%). Conclusions/Significance Our results suggest that GPS telemetry is reliably applicable to riparian and even diving freshwater animals. They also highlight the need, in GPS wildlife studies, for performing site-specific pilot studies on GPS functioning as well as for taking into account eventual spatial and temporal correlation of location estimates. The limited price, small dimensions, and high performance of the device presented here make it a useful and cost-effective tool for studies on otters and other aquatic or terrestrial medium-to-large-sized animals.

Microtus cabrerae (Rodentia: Cricetidae)

Abstract:  Microtus cabrerae Thomas, 1906, or Cabreras vole, is a medium-sized arvicoline, and one of the largest Microtus species. M. cabrerae is an Iberoccitane endemic, which is currently restricted to the Iberian Peninsula, where it presents a highly fragmented distribution. The species is the sole extant representative of the anagenetic Iberomys lineage with origin in the early Pleistocene. M. cabrerae is primarily restricted to wet habitats dominated by tall grasses, sedges, and rushes. The species has experienced strong population declines mainly during the past 10 years, particularly due to agricultural intensification. M. cabrerae is currently classified by the International Union for Conservation of Nature and Natural Resources as “Near Threatened,” and is listed in the Habitats Directive and Bern Convention, thus requiring appropriate conservation measures.