Project

Road Macroecology: analysis tools to assess impacts on biodiversity and landscape structure

Goal: This study was developed under the the scope of the Brazilian program "Atração de Jovens Talentos" of the National Science Institute (CNPq).

We intended to work on the two main negative effects of roads on wildlife: mortality due to vehicles collision and habitat fragmentation in Brazil.

The main objectives were:

- Make available a database of published and unpublished road-kills of terrestrial vertebrates in Brazil.

• Identify the biological and ecological mechanisms that make species particularly vulnerable to road mortality;

• Analyse the effect of road mortality on populations viability;

• Examine critical areas for birds and mammals population persistence due to roads;

This project includes the collaboration of international researchers to develop tools in order to identify the effects of roads towards Brazilian birds and mammals.

Date: 26 February 2015 - 26 November 2017

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Clara Grilo
added a research item
Aim The road network is increasing globally but the consequences of roadkill on the viability of wildlife populations are largely unknown. We provide a framework that allows us to estimate how risk of extinction of local populations increases due to roadkill and to generate a global assessment that identifies which mammalian species are most vulnerable to roadkill and the areas where they occur. Location Global. Time period 1995–2015. Major taxa studied Terrestrial mammals. Methods We introduce a framework to quantify the effect of roadkill on terrestrial mammals worldwide that includes three steps: (a) compilation of roadkill rates to estimate the fraction of a local population killed on the roads, (b) prediction of population risk of extinction based on observed roadkill rates (for a target group of species of conservation concern and non-threatened species with high roadkill rates), and (c) global assessment of vulnerability to roadkill for 4,677 terrestrial mammalian species estimated using phylogenetic regression models that link extinction risk to demographic parameters. Results We identified four populations among the 70 species in the target group that could become extinct in 50 years if observed roadkill levels persist in the study areas: maned wolf Chrysocyon brachyurus (Brazil), little spotted cat Leopardus tigrinus (Brazil), brown hyena Hyaena brunnea (Southern Africa) and leopard Panthera pardus (North India). The global assessment revealed roadkill as an added risk for 2.7% (n = 124) terrestrial mammals, including 83 species Threatened or Near Threatened. We identified regions of concern that have species vulnerable to roadkill with high road densities in areas of South Africa, central and Southeast Asia, and the Andes. Main conclusions Our framework revealed populations of threatened species that require special attention and can be incorporated into management and planning strategies informing road managers and conservation agencies.
Clara Grilo
added a research item
The negative effects of roads on wildlife populations are a growing concern. Movement corridors and road-kill data are typically used to prioritize road segments for mitigation measures. Some research suggests that locations where animals move across roads following corridors coincide with locations where they are often killed by vehicles. Other research indicates that corridors and road-kill rarely occur in the same locations. We compared movement corridor and road mortality models as means of prioritizing road segments for mitigation for five species of felids in Brazil: tiger cats (Leopardus tigrinus and Leopardus guttulus were analyzed together), ocelot (Leopardus pardalis), jaguarundi (Herpailurus yagouaroundi), and puma (Puma concolor). We used occurrence data for each species and applied circuit theory to identify potential movement corridors crossed by roads. We used road-kill records for each species and applied maximum entropy to determine where mortality was most likely to occur on roads. Our findings suggest that movement corridors and high road mortality are not spatially associated. We suggest that differences in the behavioral state of the individuals in the species occurrence and road-kill data may explain these results. We recommend that the road segments for which the results from the two methods agree (~5300 km for all studied species combined at 95th percentile) should be high-priority candidates for mitigation together with road segments identified by at least one method in areas where felids occur in low population densities or are threatened by isolation effects.
Clara Grilo
added 2 research items
Mortality from collision with vehicles is the most visible impact of road traffic on wildlife. Mortality due to roads (hereafter road-kill) can affect the dynamic of populations of many species and can, therefore, increase the risk of local decline or extinction. This is especially true in Brazil, where plans for road network upgrading and expansion overlaps biodiversity hotspot areas, which are of high importance for global conservation. Researchers, conservationists and road planners face the challenge to define a national strategy for road mitigation and wildlife conservation. The main goal of this dataset is a compilation of geo-referenced road-kill data from published and unpublished road surveys. This is the first Data Paper in the BRAZIL series (see ATLANTIC, NEOTROPICAL, and BRAZIL collections of Data Papers published in Ecology), which aims make public road-kill data for species in the Brazilian Regions. The dataset encompasses road-kill records from 45 personal communications and 26 studies published in peer-reviewed journals, theses and reports. The road-kill dataset comprises 21,512 records, 83% of which are identified to the species level (n = 450 species). The dataset includes records of 31 amphibian species, 90 reptile species, 229 bird species, and 99 mammal species. One species is classified as Endangered, eight as Vulnerable and twelve as Near Threatened. The species with the highest number of records are: Didelphis albiventris (n = 1,549), Volatinia jacarina (n = 1,238), Cerdocyon thous (n = 1,135), Helicops infrataeniatus (n = 802), and Rhinella icterica (n = 692). Most of the records came from southern Brazil. However, observations of the road-kill incidence for non-Least Concern species are more spread across the country. This dataset can be used to identify which taxa seems to be vulnerable to traffic, analyze temporal and spatial patterns of road-kill at local, regional and national scales and also used to understand the effects of road-kill on population persistence. It may also contribute to studies that aims to understand the influence of landscape and environmental influences on road-kills, improve our knowledge on road-related strategies on biodiversity conservation and be used as complementary information on large-scale and macroecological studies. No copyright or proprietary restrictions are associated with the use of this data set other than citation of this Data Paper.
Mortality from collision with vehicles is the most visible impact of road traffic on wildlife. Mortality due to roads (hereafter road-kill) can affect the dynamic of populations of many species and can, therefore, increase the risk of local decline or extinction. This is especially true in Brazil, where plans for road network upgrading and expansion overlaps biodiversity hotspot areas, which are of high importance for global conservation. Researchers, conservationists and road planners face the challenge to define a national strategy for road mitigation and wildlife conservation. The main goal of this dataset is a compilation of geo-referenced road-kill data from published and unpublished road surveys. This is the first Data Paper in the BRAZIL series (see ATLANTIC, NEOTROPICAL, and BRAZIL collections of Data Papers published in Ecology), which aims make public road-kill data for species in the Brazilian Regions. The dataset encompasses road-kill records from 45 personal communications and 26 studies published in peer-reviewed journals, theses and reports. The road-kill dataset comprises 21,512 records, 83% of which are identified to the species level (n = 450 species). The dataset includes records of 31 amphibian species, 90 reptile species, 229 bird species, and 99 mammal species. One species is classified as Endangered, eight as Vulnerable and twelve as Near Threatened. The species with the highest number of records are: Didelphis albiventris (n = 1,549), Volatinia jacarina (n = 1,238), Cerdocyon thous (n = 1,135), Helicops infrataeniatus (n = 802), and Rhinella icterica (n = 692). Most of the records came from southern Brazil. However, observations of the road-kill incidence for non-Least Concern species are more spread across the country. This dataset can be used to identify which taxa seems to be vulnerable to traffic, analyze temporal and spatial patterns of road-kill at local, regional and national scales and also used to understand the effects of road-kill on population persistence. It may also contribute to studies that aims to understand the influence of landscape and environmental influences on road-kills, improve our knowledge on road-related strategies on biodiversity conservation and be used as complementary information on large-scale and macroecological studies. No copyright or proprietary restrictions are associated with the use of this data set other than citation of this Data Paper.
Rafaela Cobucci Cerqueira
added 2 research items
Universidade Federal de Lavras, CP 3037, Lavras, MG, CEP 37200-000, Brasil. Potential movement corridors and road-kill likelihood models have been used as analytical tools to identify areas for placing road-effect mitigation measures. Our main goal was to identify road segments for placing mitigation measures for felids in Brazil using these two different methods to evaluate the spatial overlap between them. We modelled data for northern tiger cat L. tigrinus, southern tiger cat L. guttulus, jaguarundi Puma yagouaroundi and puma Puma concolor throughout each species' range within Brazil. Tiger cats were modelled together. We ran habitat suitability models using species locations as response variable and then used the inverse of habitat suitability to create resistance maps. We applied circuit theory to model potential movement
Mortality from collision with vehicles is the most visible impact of road traffic on wildlife. Mortality due to roads (hereafter road‐kill) can affect the dynamic of populations of many species and can, therefore, increase the risk of local decline or extinction. This is especially true in Brazil, where plans for road network upgrading and expansion overlaps biodiversity hotspot areas, which are of high importance for global conservation. Researchers, conservationists and road planners face the challenge to define a national strategy for road mitigation and wildlife conservation. The main goal of this dataset is a compilation of geo‐referenced road‐kill data from published and unpublished road surveys. This is the first Data Paper in the BRAZIL series (see ATLANTIC, NEOTROPICAL, and BRAZIL collections of Data Papers published in Ecology), which aims make public road‐kill data for species in the Brazilian Regions. The dataset encompasses road‐kill records from 45 personal communications and 26 studies published in peer‐reviewed journals, theses and reports. The road‐kill dataset comprises 21,512 records, 83% of which are identified to the species level (n = 450 species). The dataset includes records of 31 amphibian species, 90 reptile species, 229 bird species, and 99 mammal species. One species is classified as Endangered, eight as Vulnerable and twelve as Near Threatened. The species with the highest number of records are: Didelphis albiventris (n = 1,549), Volatinia jacarina (n = 1,238), Cerdocyon thous (n = 1,135), Helicops infrataeniatus (n = 802), and Rhinella icterica (n = 692). Most of the records came from southern Brazil. However, observations of the road‐kill incidence for non‐Least Concern species are more spread across the country. This dataset can be used to identify which taxa seems to be vulnerable to traffic, analyze temporal and spatial patterns of road‐kill at local, regional and national scales and also used to understand the effects of road‐kill on population persistence. It may also contribute to studies that aims to understand the influence of landscape and environmental influences on road‐kills, improve our knowledge on road‐related strategies on biodiversity conservation and be used as complementary information on large‐scale and macroecological studies.
Fernando Pinto
added a research item
Biodiversity in Latin America is at risk today due to habitat loss, land conversion to agriculture and urbanization. To grow their economies the developing countries of Latin America have begun to invest heavily in new road construction. An assessment of research on the impacts of roads on wildlife in Latin America will help define science-based conservation strategies aimed at mitigating road expansion. The aim of this review was to qualitatively and quantitatively assess scientific research papers addressing road impacts on vertebrate species in Latin America. We searched for scientific papers published as early as 1990 to 2017. We reviewed a total of 197 papers. Published research showed an increasing trend in the last decade with a strong geographic bias with a majority of papers from Brazil. Mammals were the most studied taxa followed by birds, reptiles and amphibians. The majority of studies focused on road mortality and at the individual species level. Studies documented an increase in deforestation rates, in land conversion to agriculture, illegal activities (hunting, logging) and the establishment of human settlements. The effects of roads on species richness and populations abundance varied among taxa with no apparent pattern within taxa. Forest-dependent species tended to avoid crossing roads. Amphibians had the highest median road-kill rate, followed by reptiles, mammals and birds. Our results suggest that there is an urgent need for more research, particularly in Central America and to employ predictive tools for difficult-to-sample or understudied species and critical conservation areas. We recommend a two-speed approach to guide future research: one focusing on quantifying individual species responses towards roads and their implications on population viability; a second consisting of regional or continental-scale analyses and modelling of road risks to species and populations to inform road planning immediately.
Clara Grilo
added a research item
Rapidly expanding road networks have been a key driver of the fragmentation and isolation of many wildlife species, and are a source of significant mortality due to collisions with vehicles. But not all animals are affected equally by transportation infrastructure, and in most cases little is known about the population-scale consequences of roads for wildlife. Even less information is available to characterize species' behavioral responses to roads. Although research shows that maned wolves (Chrysocyon brachyurus) in Brazil are experiencing considerable fragmentation and road mortality, the degree to which these disturbances are impacting the species' viability is unknown. The goal of this study was to analyze the potential effects of roads on maned wolf population size and structure. We used a simulation model to evaluate the population-scale consequences of individual maned wolf interactions with roads, which can result in road crossing, avoidance, or mortality due to a collision with a vehicle. We also forecasted where in Brazil these impacts might be most significant. Our model incorporated species demographic and movement parameters, plus habitat quality and a map of the road network. We found that even moderate rates of road mortality led to severe declines in population size, and that four specific locations accounted for a disproportionate fraction of roadkill events. Our approach will be generally useful for evaluating the relative importance of road effects on species conservation in many ecological systems, for prioritizing data collection efforts, and for informing conservation policies and mitigation strategies.
Clara Grilo
added 2 research items
Mortality from collision with vehicles is the most visible impact of road traffic on wildlife. Mortality due to roads (hereafter road-kill) can affect the dynamic of populations of many species and can, therefore, increase the risk of local decline or extinction. This is especially true in Brazil, where plans for road network upgrading and expansion overlaps biodiversity hotspot areas, which are of high importance for global conservation. Researchers, conservationists and road planners face the challenge to define a national strategy for road mitigation and wildlife conservation. The main goal of this dataset is a compilation of geo-referenced road-kill data from published and unpublished road surveys. This is the first Data Paper in the BRAZIL SERIES (see ATLANTIC, NEOTROPICAL, and BRAZIL collections of Data Papers published in Ecology), which aims make public road-kill data for species in the Brazilian Regions. The dataset encompasses road-kill records from 45 personal communications and 26 studies published in peer-reviewed journals, theses and reports. The road-kill dataset comprises 21,512 records, 83% of which are identified to the species level (n = 450 species). The dataset includes records of 31 amphibian species, 90 reptiles species, 229 birds species, and 99 mammals species. One species is classified as Endangered, eight as Vulnerable and twelve as Near Threatened. The species with the highest number of records are: Didelphis albiventris (n = 1,549), Volatinia jacarina (n = 1,238), Cerdocyon thous (n = 1,135), Helicops infrataeniatus (n = 802), and Rhinella icterica (n = 692). Most of the records came from southern Brazil. However, observations of the road-kill incidence for non-Least Concern species are more spread across the country. This dataset can be used to identify which taxa seems to be vulnerable to traffic, analyze temporal and spatial patterns of road-kill at local, regional and national scales and also used to understand the effects of road-kill on population persistence. It may also contribute to studies that aims to understand the influence of landscape and environmental influences on road-kills, improve our knowledge on road-related strategies on biodiversity conservation and be used as complementary information on large-scale and macroecological studies. No copyright or proprietary restrictions are associated with the use of this data set other than citation of this Data Paper.
Clara Grilo
added a research item
Road networks can have serious ecological consequences for many species, mainly through habitat fragmentation and mortality due to collisions with vehicles. One example of a species impacted by roads is the giant anteater (Myrmecophaga tridactyla), currently listed as Vulnerable by IUCN. Here we analysed the relative effect of fragmentation and mortality due to roads on giant anteater populations and show the critical areas for their persistence in Brazil. We estimated minimum patch size and maximum road density to evaluate the impact of the road network and observed road-kills on this species. We explored different scenarios by varying values of dispersal capacity to estimate the minimum patch size, and also of population densities to estimate maximum road density for giant anteater persistence. Our findings indicated that the minimum patch size can be from 498 to 247 km² and the maximum road density can vary between 0.21 and 0.55 km/km² in pessimist and optimistic scenarios, respectively. In Brazil, habitat fragmentation seemed to have a major impact over giant anteater populations. Habitat fragmentation due to roads seemed to have a more negative effect than mortality due to collisions with vehicles. Critical areas for the species persistence can represent 32% of its range in the optimistic scenario with 18% of suitable patches below the minimum size and 0.1% above the maximum road density. This study provides insights and implications for road networks on giant anteater populations in Brazil and guidance on road density and patch size thresholds for land managers and road agencies charged with planning ecologically sustainable roads in Brazil.
Clara Grilo
added a research item
Mortality from collision with vehicles is the most visible impact of road traffic on wildlife. Mortality due to roads (hereafter road-kill) can affect the dynamic of populations of many species and can, therefore, increase the risk of local decline or extinction. This is especially true in Brazil, where plans for road network upgrading and expansion overlaps biodiversity hotspot areas, which are of high importance for global conservation. Researchers, con-servationists and road planners face the challenge to define a national strategy for road mitigation and wildlife conservation. The main goal of this dataset is a compilation of geo-referenced road-kill data from published and unpublished road surveys. This is the first Data Paper in the BRAZIL series (see ATLANTIC, NEOTROPICAL, and BRAZIL collections of Data Papers published in Ecology), which aims make public road-kill data for species in the Brazilian Regions. The dataset encompasses road-kill records from 45 personal communications and 26 studies published in peer-reviewed journals, theses and reports. The road-kill dataset comprises 21,512 records, 83% of which are identified to the species level (n = 450 species). The dataset includes records of 31 amphibian species, 90 reptile species, 229 bird species, and 99 mammal species. One species is classified as Endangered, eight as Vulnerable and twelve as Near Threatened. The species with the highest number of records are: Didelphis albiventris (n = 1,549), Volatinia jacarina (n = 1,238), Cerdocyon thous (n = 1,135), Helicops infrataeniatus (n = 802), and Rhinella icterica (n = 692). Most of the records came from southern Brazil. However, observations of the road-kill incidence for non-Least Concern species are more spread across the country. This dataset can be used to identify which taxa seems to be vulnerable to traffic, analyze temporal and spatial patterns of road-kill at local, regional and national scales and also used to understand the effects of road-kill on population persistence. It may also contribute to studies that aims to understand the influence of landscape and environmental influences on road-kills, improve our knowledge on road-related strategies on biodiversity conservation and be used as complementary information on large-scale and macroecological studies. No copyright or proprietary restrictions are associated with the use of this data set other than citation of this Data Paper.
Clara Grilo
added a research item
Conservation at the cross-roads: how roads and other linear infrastructure influence conservation symposium at the International Congress of Conservation Biology and the European Congress of Conservation Biology 6th August 2015.
Clara Grilo
added 2 research items
1.Common worldwide and encroaching on even the most remote locations, roads negatively affects wildlife through habitat loss, fragmentation and direct mortality. Reducing these effects requires mitigation, including wildlife crossing structures and fencing. However, mitigation measures are expensive and vary in their success level, especially when constructed to meet the needs of several species. Moreover, mitigation planning rarely considers the needs of multiple species. As funds are limited, deciding where and how to act for the greatest return on investment is crucial. 2.Combining decision theory with a metapopulation model, we determined the most cost‐effective actions mitigating the effects of roads on multiple species. The model is illustrated with two sets of species with varying of life history traits, from a diversity of taxonomic groups. We tested the cost‐effectiveness of spatially explicit combinations of three management options for each road section: 1) no mitigation, 2) fences without wildlife crossings, and 3) fences combined with wildlife crossings. 3.We explored the trade‐offs between each population's probability of persistence and total mitigation cost, first on a per‐species basis and then considering all species. We then tested the cost‐effectiveness of different planning strategies: 1) single species, 2) two types of focal species based on different life history traits, and 3) comprehensive multispecies planning. 4.Planning for the needs of all species at the same time (multispecies strategy) maximizes the number of persisting species and provides the most robust and cost‐effective planning strategy, while single‐species strategies were found to be inefficient. However, basing decisions on the focal species with the largest home range can provide reasonably cost‐effective results, but should be considered only when there is not enough time or money to collect the necessary information to perform a multispecies analysis. 5.Synthesis and applications. Our model can be adapted to most road mitigation problems. It illustrates that the needs of multiple species should be considered to plan a cost‐effective road mitigation system. However, when resources are limited to plan for all species, those with larger home ranges should be used as reasonable proxies for other species. This article is protected by copyright. All rights reserved.
Aim Collisions between wildlife and vehicles are recognized as one of the major causes of mortality for many species. Empirical estimates of road mortality show that some species are more likely to be killed than others, but to what extent this variation can be explained and predicted using intrinsic species characteristics remains poorly understood. This study aims to identify general macroecological patterns associated with road mortality and generate spatial and species‐level predictions of risks. Location Brazil. Time period 2001–2014. Major taxa Birds and mammals. Methods We fitted trait‐based random forest regression models (controlling for survey characteristics) to explain 783 empirical road mortality rates from Brazil, representing 170 bird and 73 mammalian species. Fitted models were then used to make spatial and species‐level predictions of road mortality risk in Brazil, considering 1,775 birds and 623 mammals that occur within the continental boundaries of the country. Results Survey frequency and geographical location were key predictors of observed rates, but mortality was also explained by the body size, reproductive speed and ecological specialization of the species. Spatial predictions revealed a high potential standardized (per kilometre of road) mortality risk in Amazonia for birds and mammals and, additionally, a high risk in Southern Brazil for mammals. Given the existing road network, these predictions mean that >8 million birds and >2 million mammals could be killed per year on Brazilian roads. Furthermore, predicted rates for all Brazilian endotherms uncovered potential vulnerability to road mortality of several understudied species that are currently listed as threatened by the International Union for Conservation of Nature. Conclusion With a rapidly expanding global road network, there is an urgent need to develop improved approaches to assess and predict road‐related impacts. This study illustrates the potential of trait‐based models as assessment tools to gain a better understanding of the correlates of vulnerability to road mortality across species, and as predictive tools for difficult‐to‐sample or understudied species and areas.
Clara Grilo
added 2 research items
Land-use change is a major threat to biodiversity globally. Roads cause direct mortality and limitation of individual movements, which may isolate populations and affect their viability in the long term. Here we provide the first comprehensive global assessment of the exposure of terrestrial mammalian carnivores to roads using an integrated modelling framework. Global. We estimated critical road densities and critical patch sizes for each species based on a spatially explicit model and life-history traits. We calculated the distribution of landscape fragment sizes for each carnivore species by intersecting global road density with each species range. The proportion of a species’ geographical range with fragments below the critical patch size is used as an index of the vulnerability to roads. We found that the carnivores expected to be most exposed to roads belong to families Felidae, Ursidae, Mustelidae, Canidae and Procyonidae. Approximately one-third of the species most affected have not been identified by the IUCN as threatened by roads. Our model projects time to extinction that may be as low as one century for some species, such as the endangered Iberian lynx. Species are expected to be more exposed in areas with medium to high road density but, surprisingly, also in areas where road density is relatively low. Hotspots of the number of species locally endangered by roads occur in North America and Asia. Our results suggest the need to reassess the status and threats of those species that have not been previously recognized as strongly affected by roads. Our framework can be applied at different spatial scales, to assess the effects of the development of the road network and inform prioritization schemes for road building, and to identify areas for conservation, and species requiring particular mitigation and restoration measures.
Clara Grilo
added 2 research items
Forests can be divided into smaller fragments by road construction, which can affect the availability of refuge and food resources for many species and limit their daily and dispersal movements. Although there are several primate species with high risk of extinction in small forest fragments disturbed by anthropogenic activities, some species exhibit high ecological plasticity to persist in human-modified landscapes. The main goal of this study is to assess the relative role of roads on the spatial behaviour of black-tufted-ear marmosets within the forest fragments located in the southern region of Minas Gerais, Brazil. We examine the influence of the habitat quality (mean distance between trees and mean canopy cover), disturbance (distance to the road, distance to the edge and edge type), and spatial configuration variables (spatial autocorrelation index, position within the fragment and fragment type) on the occurrence of black-tufted-ear marmoset in fragments distributed along a transition biome area between Atlantic Forest and Cerrado. We monitored black-tufted-ear marmoset groups inhabiting forest fragments away from the roads (three control fragments) and fragments close to road segments (three impacted fragments). Impacted fragments were located in an urban area at least 1 km from each other, and with an average distance of 8 m from the nearest road. All control fragments were located in a rural area at least 4 km from each other, and with an average distance of 426 m from the nearest road. We defined 0.4-ha quadrats (64 m x 64 m) as survey units within the fragments, according to the minimum size of home-range area recorded for black-tufted-ear marmosets. Six surveys were conducted between
Clara Grilo
added a research item
There are several primate species with high risk of extinction in small forest fragments disturbed by human activities. However, some species exhibit high ecological plasticity, which allows them to persist in human-modified landscapes. The main goal of this study is to examine the relative roles of vegetation (mean distance among trees and mean canopy cover), human disturbance (distance to the road, distance to the fragment edge and edge type), and habitat spatial configuration (spatial autocorrelation index, category of quadrat – position within the fragment/fragment type) on the habitat selection of the black-tufted marmoset Callithrix penicillata in forest patches. We selected forest patches near and away from roads/urban areas, in southern Minas Gerais state, south-eastern Brazil. We used generalized linear mixed models to explain the presence of black-tufted marmoset in those patches. Our results show that black-tufted marmoset tend to occupy forest fragments closer to roads/urban areas, and consequently are under the influence of anthropic disturbance. In addition to the area delimited by these fragments, there is a preference for edge environments, where disturbances are exacerbated and the ecological conditions are suitable for exploitation by the black-tufted marmoset (supply of gum trees and reduced risk of competition). We suggest that a cross-habitat spillover by marmoset occur from forests to small habitat patches close to human-modified areas, such as those in proximity to roads and urban zones.
Clara Grilo
added 5 research items
Several studies document that species perceives or responds to its environment at different spatial scales. Knowledge on which spatial scale should be used to assess the importance of environmental variables to explain road mortality risk is still scarce. Roads cause a particular impact on large carnivores, since they usually have large home ranges and low reproduction rates. However, few studies explore the use of different spatial units on modeling and the influence of one scale may cause on the results. The maned wolf (Chrysocyon brachyurus) is a generalist carnivore, classified as Vulnerable by the ICMBio and as Near Threatened by the IUCN Red List. Collisions with vehicles are one of the main threats suffered by the species. The aim of this research is to evaluate role of environmental variables to explain maned wolf road-kill likelihood across multiple scales and therefore the implications on spatial patterns of road mortality risk. We used two spatial extents (species distribution and only the road network within the species distribution) and two spatial unit sizes (species home-range size (64km 2) and the standard size for road-kill modeling (1km length) – 1km 2) to model the maned wolf road-kill likelihood. More specifically, we performed three models: 1) species distribution area with the home range size as the spatial unit, 2) species distribution area with 1km 2 resolution, and 3) road network with 1km 2 resolution. For the data collection, road-kill georeferenced data were obtained from Urubu System database and from published papers. Variables used to predict species mortality risk included bioclimatic (maximum temperature of the warmest month), landscape (river density, area of mosaic croplands/open vegetation, forest, mosaic forest/open vegetation and open vegetation), landscape metrics (Simpson's index) and human pressure (human population density, Euclidean distance to protected areas and type of
Roads affect a wide range of species with direct mortality caused by collision with vehicles as the most conspicuous impact. However, species are not equally affected by road traffic and several studies have suggested that some species' traits (e.g. body mass, diet) are associated with increased vulnerability to roads. The main goal of this study is to explore if species' intrinsic traits explain road-kill rates of birds and mammals in Brazil. We tested three hypotheses that could explain the relationship between traits and road-kill rates (Figure 1): (1) the degree of perception of risk mainly determines vulnerability to traffic; (2) ecological specialization predicts vulnerability to traffic; and (3) both the degree of perception of risk and ecological specialization predict vulnerability. Estimates of road-kill rates for 175 bird and 75 mammal species were obtained from national/international peer-reviewed publications and grey literature considering only studies in which surveys were conducted at least once a week. We selected seven traits related to perception of risk: body mass, activity cycle (nocturnal or non-nocturnal), age at first birth (age females give birth to first litter), home range size, sociality (solitary or social), lifespan, and number of anthropogenic threaten factors (as more threatened species may be more aware of risk). We considered five traits associated to ecological specialization: diet breath (number of different diet items), trophic level (carnivore or non-carnivore), foraging substratum (volant or non-volant), land use breath (number of different land use classes) and predominant land use (preferred land use class).
Clara Grilo
added a project goal
This study was developed under the the scope of the Brazilian program "Atração de Jovens Talentos" of the National Science Institute (CNPq).
We intended to work on the two main negative effects of roads on wildlife: mortality due to vehicles collision and habitat fragmentation in Brazil.
The main objectives were:
- Make available a database of published and unpublished road-kills of terrestrial vertebrates in Brazil.
• Identify the biological and ecological mechanisms that make species particularly vulnerable to road mortality;
• Analyse the effect of road mortality on populations viability;
• Examine critical areas for birds and mammals population persistence due to roads;
This project includes the collaboration of international researchers to develop tools in order to identify the effects of roads towards Brazilian birds and mammals.