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Effectiveness of crossings as wildlife passages for mammals in the Yungas of Argentina
Abstract
Irrigation canals are an important cause of wild mammal mortality in the Piedmont forest of the Argentine Yungas. To improve the permeability of this infrastructure, specific wildlife crossings were added to the existing non-wildlife crossings built for other purposes. However, the effectiveness of these wildlife-specific crossings has still not been evaluated. Here, we identified the mammalian species that use the crossings, determined the global frequency of use of each crossing through a use index, and evaluated the possible predilection of a species for a particular crossing type using species-specific models. We found that 50% of species in the study area used the crossings. The highest percentages of use corresponded to tapeti (Sylvilagus brasiliensis, 25.4%), lowland tapir (Tapirus terrestris, 21.5%), agouti (Dasyprocta punctata, 20.7%), crab-eating fox (Cerdocyon thous, 9.1%) and tayra (Eira barbara, 6.3%).The global model shows that crossing type, openness and vegetation vertical structure were the best predictors of crossing use. Species-specific models show in general that variables related to the structure of the crossings were better able to explain animal movement. The dry season increased the use of the crossings. We concluded that the presence of both wildlife-specific and non-wildlife-specific crossings would contribute to reducing the barrier effect and, therefore, to mammal conservation. In this connection we recommend that simple, low-cost wildlife-specific crossings be taken into account.
... Canals are common, extensive, and often overlooked landscape features globally and in the United States specifically, and deliver important water resources across thousands of kilometers, especially in arid environments where water is a limiting factor to human occupation and agriculture. Although much research has focused on the use of overpass and underpass crossing structures along major roads (Clevenger and Waltho, 2003;Ree et al., 2007;Mata et al., 2008;Corlatti et al., 2009;Sawaya et al., 2014;McGregor et al., 2015;Ford and Clevenger, 2019;Bhardwaj et al., 2020), little research has evaluated wildlife use of overpass crossing structures along other types of linear infrastructures, including major canals (although, see Popowski and Krausman, 2002, Peris and Morales, 2004, Baechli et al., 2021, Azedo et al., 2022. Canals exhibit similarities and differences when compared to road systems. ...
... ural characteristics (Clevenger and Waltho, 2003;Bond and Jones, 2008;Mysłajek et al., 2020). First, wildlife may be more likely to use crossing structures during particular seasons due to fluctuations in temperature, precipitation, and forage availability (Clevenger and Waltho, 2003, Mata et al., 2009, Sparks and Gates, 2012, Mysłajek et al., 2020. Baechli et al., 2021. Second, wildlife use of crossing structures may vary across times to day, which can also change seasonally (Kronfeld-Schor et al., 2013;Barrueto et al., 2014). In addition, wildlife may alter daily activity patterns in response to human structures and development (Tigas et al., 2002;Barrueto et al., 2014;Lewis et al., 2011;Lendrum et a ...
... In this study, a suite of small-to large-sized mammals used overpasses and siphons to cross a major canal. These results are consistent with other studies reporting that crossings can promote wildlife movement across canals (Popowski and Krausman, 2002;Peris and Morales, 2004;Baechli et al., 2021;Azedo et al., 2022) and other types of anthropogenic linear infrastructures, such as roads (Clevenger and Waltho, 2005;Olsson et al., 2008;Sawaya et al., 2013;McGregor et al., 2015;Simpson et al., 2016). However, it is important to understand how each species responds to canal crossings and the environmental variables that promote their use of these structures, especially when considering habitat associations and wildlife behavior unique to individual species (Lima and Dill, 1990;Denneboom et al., 2021). ...
Anthropogenic linear infrastructures can reduce landscape connectivity for wildlife, and crossing structures are a mitigation strategy to facilitate animal movement across potential barriers. However, the spatial and temporal factors promoting crossing structure use by the wildlife community across scales are not fully understood, especially for major water canals. We tested multiple hypotheses and predictions to evaluate how wildlife use of crossing structures was influenced by (1) landscape features (i.e., fine landscape-scale vegetation cover and broad landscape-scale plant productivity, topography, and human development), (2) season, and (3) time of day. We used remote cameras to monitor 43 overpasses and 13 siphons (i.e., natural crossing areas where the canal traveled underground) along the Central Arizona Project canal across three seasons (i.e., hot-dry, hot-wet, cool-wet) during one year. We detected 17 small- to large-sized herbivore and carnivore species using overpasses and siphons. When using crossing structures, each wildlife species exhibited unique habitat relationships in relation to vegetation cover, plant productivity, and topography. Several species decreased use of overpasses as the amount of human development increased. Crossing frequency increased in the hot-dry and cool-wet seasons for many species at overpasses (11 species) and siphons (9 species). Daily activity patterns of individual species were similar across seasons, and between overpasses and siphons. Ultimately, this study suggests that to promote movement across canals for the wildlife community, it is important to provide a variety of crossing types that occur away from human development and across a range of vegetation and topographic characteristics.
... Although only 20% of cultivated areas are irrigated, this is where 40% of the world's food is produced (Rossi 2019). However, irrigation canals have negative impacts on terrestrial mammals such as carnivores, including barrier and trapping (drowning) effects, disruption of seasonal movements, habitat fragmentation, and hindering the gene flow (Krausman & Bucci 2010;Baechli et al. 2021). Documenting the mechanisms to mitigate the impacts of irrigation canals is therefore becoming an urgent task. ...
... Most mitigation strategies are derived from road ecology, yet the effectiveness of crossing structures to reduce canal impacts has not been validated. To date, only two studies address the use of crossing structures by animals across canals, in Spain (Peris & Morales 2004) and Argentina (Baechli et al. 2021). ...
... Culverts are primarily engineered to allow rainwater runoff and stream flow under the canal and prevent flooding (Baechli et al. 2021). Notwithstanding, culverts are also widely used by animals and contribute substantially to canal crossings (Godinho & Onofre 2013). ...
As rainfall becomes scarcer or more erratic, we rely more on irrigation systems for agricultural and human water provision. Impacts of irrigation canals such as the barrier effect on wildlife movements are poorly documented. Although canal culverts and overpasses can be used by wildlife, little is known about their crossing behavior to guide barrier effect mitigation efforts. Over seven years, we recorded medium-sized carnivore crossings by video-surveillance through 30 culverts and 28 overpasses in a large irrigation project in south-central Portugal. We examined the influence of the structures’ features and landscape context on the likelihood of canal crossing. Culvert crossings were positively influenced by the proportion of nearby montado, a high nature value farming system. Overpass crossings were more likely in areas away from paved roads and with more nearby wetlands. Overpasses increased the crossing rates by about 11% relative to culverts and both were crossed more often in landscapes with evenly distributed land uses. In the project area, 20% of the montado has recently transitioned to irrigated agriculture, and wetlands have increased by 43%. It is therefore plausible that the increase in the crossing rate of overpasses relative to culverts will be accentuated. Our study produced the first evidence of a contrast in crossing rates among irrigation canal crossing structures. We have shown that the landscape can be a driver of animal crossings but irrigation projects can in turn be transformative of the landscape. Broadly, the fact that the deployment of irrigation canals may favor some land uses over others creates a conundrum that needs careful consideration when planning barrier effect mitigation interventions.
... . Overpass crossing structures on canals are used by a variety of species, particularly medium-and large-sized mammals (Popowski and Krausman 2002, Peris and Morales 2004, Baechli et al. 2021, Azedo et al. 2022. However, to what degree many smaller wildlife species use crossing structures associated with canals is unknown. ...
Landscape connectivity is critical to the long‐term conservation of wildlife populations. Although anthropogenic linear infrastructures (ALI), including roads and canals, provide important resources to humans, they can affect wildlife through habitat fragmentation and reduced movement through landscapes. To increase landscape connectivity, crossing structures, including underpasses, can facilitate wildlife movement across landscapes experiencing ALI. However, little is known about how a suite of small‐ to medium‐sized species use underpasses across seasonal and daily time periods, especially for some ALI such as major canals. We used specialized camera technology (i.e., the Hobbs Active Light Trigger [HALT] camera) to evaluate use of culvert underpass crossing structures (hereafter culverts) along the Central Arizona Project canal, Arizona, by a suite of mammals, reptiles, amphibians, and invertebrates. Specifically, we evaluated (1) which wildlife species used culverts, (2) how the frequency of use varied across seasons (i.e., hot‐dry, hot‐wet, cool‐wet) and (3) daily activity patterns of wildlife using culverts. We detected 31 species of wildlife using culverts, which included small‐ to medium‐sized mammals (56.4% of crossings), reptiles (21.0% of crossings), amphibians (19.0% of crossings), and invertebrates (3.6% of crossings), including some species of conservation concern, such as the Sonoran Desert tortoise (Gopherus morafkai) and Gila monster (Heloderma suspectum). However, crossings by larger mammal species were less effectively detected with the HALT cameras. Reptile crossing frequency was similar between the 2 seasons that they were active during the hot‐dry (May–June) and hot‐wet (July–October) seasons and crossing frequency by some species of amphibians and invertebrates was higher in the hot‐wet season. Throughout the entire year, small mammals used culverts more frequently in hot seasons (i.e., hot‐wet and hot‐dry) compared to the cool‐wet (November‐March) season. In addition, daily activity patterns varied by species, where species crossed culverts during diurnal (e.g., desert spiny lizards, Sceloporus magister and coachwhip snakes, Masticophis flagellum), crepuscular (e.g., cottontail rabbits, Sylvilagus audubonii and western diamondback rattlesnakes, Crotalus atrox), and nocturnal (e.g., deer mouse species, heteromyid species, woodrat species, desert stink beetle species) time periods. Our information can be used to manage wildlife crossing areas and increase landscape connectivity in relation to ALI.
... The implementation of fencing along highways and the use of underpasses (e.g., drainage culverts and cattle boxes) have been proposed as strategies to reduce roadkill and maintain population connectivity (Abra et al., 2020;Ascensao et al., 2021). Populations fragmented by irrigation canals can also be reconnected through the implementation of wildlifespecific crossings (Baechli et al., 2021). ...
This comprehensive chapter covers various aspects of the biology and natural history of the lowland tapir (Tapirus terrestris), including names, taxonomy, subspecies and distribution, descriptive notes, habitat, movement ecology and population density, activity patterns, feeding ecology, reproduction and growth, behavior, and status in the wild and in captivity. The chapter includes a distribution map, several photos of the species, and a list of key literature.
... Irrigation structures, such as irrigation canals, have been reported as the cause of death of 134 vertebrate species, 20.9% of them mammals, in West central Spain during a study period of 13 months(García, 2009). In carnivores, such structures may not only be deadly but also may fragment habitats, disrupt seasonal movements, and hinder gene flow(Baechli et al., 2021;Krausman & Bucci, 2010).The female Iberian lynx showed signs of adaptation to her injury as observed from body condition scores during the 20-day time lapse recorded by camera traps. Home-range estimates from this female are larger than those previously described for the species and sex(Rueda et al., 2021), probably because she was still in a dispersal phase during the first months after release. ...
Severe musculoskeletal diseases, such as those associated with congenital or traumatic events, that result in missing limbs may compromise the fitness and survival of free-living felids. Here we report the space use of four amputee individuals from three felid species captured from 2017 to 2022 in Missouri (USA), Toledo and Badajoz (Spain), and Suitai Khairkhan Mountain (Mongolia). We describe home ranges and daily travel distances post-release of free-living felids that had either suffered a traumatic amputation or following a surgical amputation. We compared these data with those reported in the literature for felids without amputations. Forelimb or hindlimb amputation did not affect the hunting, mating, or territory patrolling behavior of any of the individuals. However, we recorded significant differences in the daily movement before and after the traumatic event of the Iberian lynx forelimb amputee. We attribute this difference to the physical impairment, although we consider other variables that may have played a role. Nevertheless, all animals appeared to cope well with their limb loss, showing home ranges and daily
... Irrigation structures, such as irrigation canals, have been reported as the cause of death of 134 vertebrate species, 20.9% of them mammals, in West central Spain during a study period of 13 months(García, 2009). In carnivores, such structures may not only be deadly but also may fragment habitats, disrupt seasonal movements, and hinder gene flow(Baechli et al., 2021;Krausman & Bucci, 2010).The female Iberian lynx showed signs of adaptation to her injury as observed from body condition scores during the 20-day time lapse recorded by camera traps. Home-range estimates from this female are larger than those previously described for the species and sex(Rueda et al., 2021), probably because she was still in a dispersal phase during the first months after release. ...
Severe musculoskeletal diseases, such as those associated with congenital or traumatic events, that result in missing limbs may compromise the fitness and survival of free‐living felids. Here we report the space use of four amputee individuals from three felid species captured from 2017 to 2022 in Missouri (USA), Toledo and Badajoz (Spain), and Suitai Khairkhan Mountain (Mongolia). We describe home ranges and daily travel distances post‐release of free‐living felids that had either suffered a traumatic amputation or following a surgical amputation. We compared these data with those reported in the literature for felids without amputations. Forelimb or hindlimb amputation did not affect the hunting, mating, or territory patrolling behavior of any of the individuals. However, we recorded significant differences in the daily movement before and after the traumatic event of the Iberian lynx forelimb amputee. We attribute this difference to the physical impairment, although we consider other variables that may have played a role. Nevertheless, all animals appeared to cope well with their limb loss, showing home ranges and daily distances within those recorded for their sex and species. Unless amputee felids represent a threat to domestic livestock or humans, our data suggest these individuals may remain free‐living as they contribute to local population persistence and appear to maintain good general health and welfare.
Linear infrastructures such as agricultural irrigation channels produce physical changes and negative impacts to habitats, wildlife populations, communities, and ecosystems. Open irrigation channels act as a pitfall for wildlife and can affect vertebrates of all sizes. Nonetheless, small channels have received relatively little attention by conservation biologists. The objective of this study was to analyze vertebrate species richness and mortality in relation to different sections of an irrigation channel system and the surrounding landscape characteristics. For two years, we conducted monthly surveys along an open-channel irrigation system to estimate its effect on vertebrates through records of dead and alive individuals. We examined the spatial relation of species richness and mortality with transects using a canonical correspondence analysis and chi-squared tests to determine possible variations in the different structures of the channel and seasonality. Further, a landscape diversity index was used to analyze the importance of surrounding habitat structure and composition on these parameters. Most vertebrates (61%) were found dead, small mammals and reptiles were the most affected. Our results indicate that mortality of small vertebrates varies depending on species, structures of the open-channel agricultural irrigation system (i.e., concrete channel and floodgates), seasonality (i.e., wet, and dry), and landscape heterogeneity (i.e., high, medium, and low landscape diversity). The open-channel irrigation system is a threat to populations of small vertebrates in anthropized landscapes, conservation efforts should be directed at protecting water bodies and restructuring the open-channel agricultural irrigation system to avoid mortality of species such as small rodents (M. mexicanus) and reptiles (C. triseriatus, B. imbricata, and Thamnophis spp.).
In the Gran Chaco, one of the most biodiverse, yet imperiled, arid biomes in the world, open-to-air concrete water canals may threaten wildlife via drowning and habitat fragmentation, although these effects are usually overlooked. We performed field surveys and local people interviews along 250 km of canals in the Gran Chaco ecoregion of Argentina during austral spring and summer (six months). We documented 207 drowned individuals of 35 wildlife species, but more realistic estimations could increase this number to the thousands. Six species of conservation concern drowned in the canal, and eight of the drowned species have decreasing population trends. Drownings in some mammal species decreased with time without any mitigation measures implemented at the canal yet, suggesting an ongoing, large-scale population reduction due to this high mortality rate. Since mitigation measures applied in other regions were not effective to stop drowning and population isolation, these infrastructures should be avoided in arid environments worldwide.
An essential part of environmental impact assessment (EIA) is the proposal of mitigation measures, whose effectiveness has a decisive influence on the magnitude of the residual impacts of the proposals. However, the effectiveness of mitigation is not always well known, and sometimes it is even used in a manipulative way. This paper presents a sample of effectiveness values for some mitigation measures commonly proposed in EIA reports, based on information from the academic and grey literature. The aim is to show that the effectiveness of miti-gation measures can be highly variable, and may even lead to undesirable effects, and to highlight how this can influence the assessment of residual impacts. As examples, climate change mitigation may have undesired effects; revegetation effectiveness is overrated at least in some regions; wildlife protection measures may be over-optimistic; and sometimes there are complaints after the implementation of mitigation measures for odour, noise or vibration because beneficiaries expected greater effectiveness. Overestimating mitigation effectiveness leads to ignoring the mitigation hierarchy and underestimating residual impacts, which may distort decision-making. The effectiveness of mitigation is often site-dependent and species-dependent, so a lot of information is needed. Feedback from environmental follow-up is necessary, and EIA authorities should make an effort to collect and disseminate this information. Academics, practitioners and environmental authorities need to work hand in hand in this regard.
El pecarí de collar está ampliamente distribuido en el centro y norte de Argentina. Se encuentra en las ecorregiones de Yungas, Chaco Seco, Chaco Húmedo, Selva Paranaense, y está siendo reintroducido en los Esteros del Iberá. Esta especie, respecto de las otras dos de pecaríes, es la menos susceptible a la degradación del bosque, la fragmentación y a la caza (Altrichter & Boaglio, 2004); también presenta una dieta generalista y su productividad es más alta (Altrichter 2006). Sin embargo, el pecarí de collar necesita de bosques nativos para persistir (Altrichter & Boaglio 2004; Periago et al. 2017). Grandes superficies de bosques nativos están siendo reemplazadas por otros tipos de cobertura con fines productivos (Hansen et al. 2013); por lo que la pérdida de bosques amenaza la conservación de este pecarí. Además, la especie se encuentra bajo altísima presión de cacería en todo su rango de distribución y está llevando a la extinción local de la especie en algunas localidades.
Se sospecha e infiere una reducción en el tamaño poblacional superior al 30% producto de la disminución del área de ocupación (AOO), extensión de presencia (EOO) y calidad del hábitat, pasada (15 años) y proyectada (10 años) hacia el futuro. Las causas de la reducción del AOO son: (1) la transformación completa del hábitat de la especie -principalmente en Selva Pedemontana de Yungas y en el Chaco Seco y Húmedo-, debido al avance de la producción intensiva agrícola y ganadera; (2) la persistencia o aumento de los niveles actuales de cacería y (3) otras amenazas en los fragmentos de hábitat remanentes.
Protected areas are cornerstones of conservation efforts worldwide. However, protected areas do not act in isolation because they are connected with surrounding, unprotected lands. Few studies have evaluated the effects of protected areas on wildlife populations inhabiting private lands in the surrounding landscapes. The lowland tapir Tapirus terrestris is the largest terrestrial mammal of the Neotropics and is categorized as Vulnerable on the IUCN Red List. It is necessary to understand the influence of landscape characteristics on the tapir's habitat use to enable effective conservation management for this species. Our objectives were to (1) determine the potential distribution of the lowland tapir's habitat in the Southern Yungas of Argentina, and (2) evaluate the role of protected areas and other covariates on tapir habitat use in adjacent private lands. We used records of lowland tapirs to model the species' potential distribution and determined habitat use with occupancy modeling. Based on the covariates found to be significant in our models, we constructed predictive maps of probability of habitat use and assessed the area of potential habitat remaining for the species. Probability of habitat use was higher in the vicinity of two national parks and small households than further away from them. We found that in 85 % of the lowland tapir's potential distribution the probability of habitat use is high (> 0.5). These areas are near the three national parks in the study area. The probability of detecting lowland tapirs increased with distance to roads. We conclude that national parks play a key role in the persistence of lowland tapir populations on adjacent private lands.
La transformación del ambiente natural constituye la principal amenaza para la conservación de muchas de las especies de mamíferos. La agricultura ha reducido la conectividad del pedemonte de Yungas con el Chaco, limitándola a corredores de hábitats naturales modificados que atraviesan una matriz de zonas transformadas. Mediante relevamientos con cámaras trampa, identificamos las especies medianas y grandes de mamíferos que utilizan corredores boscosos en dos sectores latitudinales del pedemonte de Yungas de Argentina. Estudiamos la diversidad de especies, la influencia de la distancia a través del corredor hasta el bosque continuo sobre la riqueza, cuantificamos similitudes en la composición y estructura de las comunidades entre ambas situaciones ambientales y evaluamos si los corredores constituyen zonas de paso o si los mamíferos establecen sus áreas de acción en los mismos. Registramos 22 especies en los corredores. Sólo seis taxones registrados en bosque continuo no fueron documentados en los corredores, y tres fueron fotografiados sólo en corredores. Para ambos sectores latitudinales, la equitatividad fue levemente mayor en corredores (aunque las diferencias fueron significativas solo en el sector norte), mientras que la riqueza de especies mostró tendencias opuestas entre sectores latitudinales, siendo mayor en el bosque del sector norte pero menor en el bosque del sector sur (aunque las diferencias no fueron significativas en ningún caso). No encontramos una influencia de la distancia al bosque continuo sobre la riqueza de mamíferos, ni diferencias importantes en la composición y estructura de las comunidades de ambas situaciones ambientales. En el norte, Dasyprocta punctata fue más frecuente en bosques continuos, mientras que Mazama gouazoubira y Leopardus pardalis prefirieron los corredores. En el sur, Leopardus pardalis y Pecari tajacu fueron más frecuentes en bosque continuo, mientras que Didelphis albiventris y las especies omnívoras utilizaron más los corredores. No encontramos diferencias significativas entre especies generalistas y especialistas en el uso de estos hábitats. Nuestro trabajo constituye la primera aproximación a esta temática en la región de las Yungas, aportando información relevante para el establecimiento de políticas de conservación.
One of the major challenges in studies of activity and movement ecology is discovering how and why animals behave differently in certain environments. The gray brocket deer (Mazama gouazoubira) is widely distributed in the Neotropic region. In the Brazilian Pantanal wetland, gray brocket deer inhabit a unique landscape with varying ecotypes arranged in a mosaic, where seasonal flooding alters resource availability for the deer.
Documenting animal activity and movement can be the key to understanding how a species interacts with its dynamic environment. We used data from accelerometers and characteristics of movement on six GPS-monitored gray brocket deer in the Pantanal wetland to investigate how habitat type, periods of the day, and cycles of flooding and drought affect activity, movement behavior, and displacement. Deer exhibited the lowest activity and encamped movement in closed habitat during diurnal and nocturnal periods, suggesting resting and foraging behaviors. The highest activity and exploratory movement occurred in open habitats, and potentially was related to deer searching for locations with greater resource availability. Individuals were displaced the most during
floods, which was a response to access feeding sites that were free of water. Our results not only represent an unprecedented and refined view of the activity and movement behavior of brocket deer, but they also stress the importance of preserving multiple habitat types for species that express variable foraging strategies in heterogeneous landscapes.
RESUMEN. En Argentina, el pecarí labiado (Tayassu pecari) está categorizado como En Peligro, ya que su dis-tribución se redujo un 63% y sus poblaciones están fragmentadas. Nuestro objetivo fue determinar el tamaño de los grupos y comparar la tasa de captura de pecarí labiado en cámaras trampa entre dos sectores donde se distribuye la especie en las Yungas Australes de Argentina. En este estudio registramos el menor tamaño de grupo (10 ± 8 pecaríes labiados/grupo) comparado con otros estudios en el Neotrópico. La tasa de captura fue significativamente mayor en el sector sureste que en el sector norte (214.68 ± 927.39 vs. 0.13 ± 1.69; W = 5501, p < 0.0001). La baja tasa de captura en el sector norte es sorprendente dado que esta especie era frecuente de registrar hasta hace unos años en este sector. La información obtenida en este trabajo permite tener una esti-mación actual del estado de conservación del pecarí labiado en dos sectores de las Yungas Australes.
ABSTRACT. Decline of white-lipped peccary (Tayassu pecari) in a high conservation value area in Southern Yungas of Argentina. In Argentina, white-lipped peccary (Tayassu pecari) is categorized as Endangered since its distribution was reduced by 63% and its populations are fragmented. Our objectives were to determine group size and to compare camera trapping rate of white-lipped peccary between two areas in the Southern Yungas of Argentina where the species is distributed. In this study, we recorded the smallest group size (10 ± 8 white-lipped peccary/group) compared to other sites in the Neotropics. Camera trapping rate was significantly higher in the southeastern area than in the northern area. The low camera trapping rate of white-lipped peccary in the northern area (214.68 ± 927.39 vs. 0.13 ± 1.69, W = 5501, p < 0.0001) is striking given that the species was frequent to record in this area a few years ago. The information obtained in this work allows to have a current estimate of the conservation status of white-lipped peccary in the two areas of Southern Yungas of Argentina.
Palabras claves: cámara trampa, Neotrópico, tasa de captura, unidad de conservación.
Los tapires son considerados especies clave porque desempeñan un papel
importante en la dispersión de semillas y porque modelan la estructura y
composición del hábitat. Por lo tanto, son esenciales para la conservación de
ecosistemas enteros. También los denominamos especies paisaje, pues utilizan
áreas extensas y heterogéneas y tienen impacto significativo en la estructura y
función de los ambientes. Por ello, la extinción local o la disminución de sus
poblaciones pueden ocasionar la disrupción de algunos procesos ecológicos,
comprometiendo la integridad a largo plazo y la biodiversidad de los
ecosistemas.
En Argentina, límite austral de la distribución de Tapirus terrestris, la especie se
ha adaptado a condiciones relativamente más estresantes que las existentes
en otras áreas. Los tapires de esta región son importantes precisamente por
estas adaptaciones extremas, también porque su hábitat está siendo destruido
aceleradamente y porque aún sabemos poco sobre ellos. Urge entonces
promover su investigación e implementar acciones de conservación que
aseguren la supervivencia de la especie a largo plazo en nuestro país.
Desde 2004, el Grupo de Especialistas de Tapires (TSG) de la UICN promueve la
ejecución de Planes de Acción en todos los países de su distribución, proceso
que se inicia en Argentina al año siguiente.
El presente documento permitió realizar una revisión de la distribución del tapir
en nuestro país, considerar las actividades relacionadas a la especie que se
desarrollan hasta el momento, identificar las amenazas a las que se enfrenta,
priorizar áreas para la conservación y finalmente, definir las estrategias
principales para su preservación a largo plazo.
Deseamos que los lineamientos definidos en este Plan de Acción sean
aplicados en las políticas que hacen al manejo y conservación de la especie,
para lograr no sólo su supervivencia in situ a largo plazo, sino también la de
muchas otras especies de los ecosistemas donde habita el tapir.
Mortality of mammals and mitigation actions in irrigation canals of the Yungas piedmont of the High Bermejo River Basin, Argentina. We compiled information on mortality in medium and large mammals in irrigation canals in the Yungas of Argentina and we evaluated the role of escape ladders in mitigating this mortality. We systematically recorded falls and deaths in the canals, and used camera traps to monitor the use of escape ladders. We documented falls of 19 specimens of five species, and the deaths of eight individuals between 2013 and 2015. Most falls and deaths corresponded to Mazama gouazoubira. Cameras recorded 16 species on the escape ladders (34% of the records corresponding to Tapirus terrestris), which seem to have a positive effect, decreasing the mortality of individuals.
Roads have important effects on wildlife, such as natural habitat fragmentation and degradation and direct killing of fauna, which leads to reductions in wildlife population size. We focused on a principal road in Northwest Argentina to test for the effect of seasonality and landscape features on the composition of road-killed wildlife. We conducted regularly scheduled road trips during the dry and wet seasons. We recorded the presence or absence of a vegetation curtain or hedge along the road. We measured land use by remote sensing in a 500 m buffer along the road. We compared the abundance of animals killed between seasons (dry and wet) for different taxonomic groups (mammals, birds and reptiles) and for different origins (domestic and native). We built linear mixed models to test the effect of landscape features on the abundance of killed animals. Two hundred and ninety-three individuals were killed, belonging to 35 species; 75.8 % were native and 24.2 % domestic species. The majority of animals killed were mid-sized mammals. More animals were killed during the dry season. The most important factors to explain the wildlife road-killing were the season and the proportion of agricultural landscape. The composition of the killed animals changed with the season. The proportion of agricultural landscape incremented the number of killed birds and mammals during both seasons, without affecting reptiles. The ratio of wild to domestic animals killed was dependent on the season. This study sets a precedent as the first in road ecology in Northwest Argentina and should be taken into account for road planning and regulation.
Las Yungas subtropicales se extienden por el noroeste de Argentina y sur de Bolivia, ocupando aproximadamente 56 000 km2. Se caracterizan por su amplia distribución altitudinal (400-2300 msnm), donde el recambio de especies de árboles determina la ocurrencia de tres pisos altitudinales (selva pedemontana, selva montana y bosque montano) con cambios consistentes en la fenología foliar y los síndromes de dispersión de las especies arbóreas. Dominan las especies caducifolias en los extremos del gradiente, y las especies semicaducifolias y siempreverdes en las elevaciones intermedias. Por su parte, las especies dispersadas por el viento o la gravedad caracterizan la parte baja del gradiente, mientras que las dispersadas por animales caracterizan los pisos superiores de vegetación. Los cambios físicos y biológicos en el gradiente altitudinal condicionan los usos y las estrategias de conservación de las Yungas subtropicales. La desforestación alcanzaba 18% de la superficie original de este ambiente en Argentina en la década de los 70 y 31% en el año 2010, principalmente (>90%) en las zonas bajas y planas. Las Yungas de Argentina presentan protección formal estatal (nacional, provincial y municipal) en 22% de su extensión actual, sin considerar las categorías internacionales, que pueden ser instrumentos valiosos, si se logra una implementación efectiva de los criterios de uso sustentable de los recursos naturales. Adicionalmente, los planes de ordenamiento territorial en marcha vinculados a compensaciones económicas podrían jugar un papel importante en el marco de estrategias regionales de uso y conservación.
While many studies have looked at how large mammals respond to road mitigation measures, few have examined the effects on smaller mammals.
We investigated the effectiveness of three different types of wildlife passages along Highway 175 in Quebec, Canada, for small‐ and medium‐sized mammals (<30 kg) using infrared cameras. Wildlife passages ( n = 17) were monitored 24 h a day 7 days a week from 2012 to 2015. Two research questions were addressed: (i) What influences passage discovery and use? and (ii) does it differ between species? Global and species‐specific models were produced for both discovery and use. A linear mixed‐effects model was used for the discovery data (log‐transformed counts), and a generalized linear mixed model was used for the crossing data (binary response).
Species' responded to the passages differently, with discoveries increasing overall and in particular for marmots Marmota monax as latitude increased. Pipe culverts were significantly more likely to be discovered by micromammals and wooden ledge culverts by red squirrels Tamiasciurus hudsonicus . Older passages were discovered less in general, with the exception of marmots. Marmots were also the only species to show a difference in crossings by passage type, favouring pipe culverts. Passage use was less likely with a median present for all models, except squirrels. More open passages had higher use overall and particularly for marmots and weasels Mustela spp.
Synthesis and applications . By separating animal responses to wildlife passages into two types (discovery and use), we have shown it is possible to incorporate multiple dimensions into post‐mitigation evaluation. This study highlights how transportation agencies can engineer more effective wildlife passages by minimizing the barrier effect of the structures themselves and constructing more passages better suited to the needs of the species they are targeting. To benefit the most species, it is recommended that future projects contain a diversity of open, single segment passages requiring long‐term monitoring.
The diversity of Brazilian mammals is among the highest of the world. However this exceptional diversity is still widely unknown and great part of it is seriously threatened by human activities. In the present study we estimated species richness and relative abundance of medium and large size mammals for the region of Brasilândia de Minas, a city situated in a fragmented and poorly studied cerrado area of Minas Gerais state, Brazil. We obtained 63 records of 24 species, including eight species threatened with extinction. Our results support the hypothesis that many of the cerrado mammal species may be able to persist in fragmented agricultural landscapes. This paper shows that despite the anthropogenic disturbances detected, the studied area plays an important role in the conservation of medium and large size mammals in the cerrado biome.
La elaboración de una “Lista formal de Especies” ha sido un anhelo de la SAREM, casi contemporáneo a su nacimiento en 1983. Esta Sociedad ha realizado múltiples reuniones científicas en las que se han expuesto los resultados de diversas líneas de investigación nacional, y siempre ha estado en el “aire” la intención de hacer realidad una publicación “global” impulsada por ella misma. Con el transcurrir del tiempo, la intensa vida académica de sus miembros, los resultados de sus proyectos, la descripción de nuevas especies, nuevos registros de distribución, mayores datos sobre historia natural y otros estudios, han generado una voluminosa información, que estimábamos importante volcar en una obra de la naturaleza de este libro, con la valiosa cooperación de los especialistas de los distintos taxa.
Los mamíferos de Argentina: sistemática y distribución tomó su impulso definitivo gracias a conversaciones mantenidas entre los editores quienes, en noviembre de 2002, durante las Jornadas Argentinas de Mastozoología en Mar del Plata, concretaron el acuerdo de convocar a diversos autores para dar inicio al proyecto. Esto se hizo efectivo en abril de 2003, cuando la comisión directiva de SAREM estaba a cargo de Noemí Gardenal y de Carlos Borghi. Desde entonces se desarrolló el proceso de discusiones e intercambios de ideas para concretar la lista de mamíferos de la Argentina que se ofrece en este trabajo.
El objetivo original de la obra fue poner a disposición de la comunidad científica, el estado actual del conocimiento de los mamíferos de Argentina, desde la óptica y conocimiento de los especialistas nacionales, quienes debían resumir la información de las especies reconocidas hasta el momento, la taxonomía que debe utilizarse y las distribuciones de cada una. Este trabajo fue pensado para servir de base conceptual actualizada para futuras investigaciones y para proyectos de investigadores y jóvenes que deseen desarrollar sus estudios de tesis o becas.
Understanding the response of biodiversity to land-use changes is an important challenge for ecologists. We assessed the effects of five landscape metrics (forest cover, number of patches, edge density, mean inter-patch isolation distance and matrix quality) and three patch metrics (patch size, shape and isolation) on the number of species and patch occupancy of medium- and large-sized terrestrial mammals in the fragmented Lacandona rain forest, Mexico. We sampled mammal assemblages in 24 forest patches and four control areas within a continuous forest. The landscape metrics were measured within a 100-ha buffer, and within a 500-ha buffer from the centre of each sampling site. A total of 21 species from 13 families was recorded. The number of species increased with shape complexity and patch size at the patch scale, and with matrix quality within 100-ha landscapes. When considering 500-ha landscapes, only the number of patches (i.e. forest fragmentation level) tended to have a negative influence at the community level. Different landscape and patch metrics predicted the occurrence of each species within the sites. Our results indicate that there is a gradient of tolerance to forest cover change, from highly sensitive species to those tolerant of, or even benefited by, forest-cover change.
The last 20 years have seen a dramatic increase in efforts to mitigate the negative effects of roads and traffic on wildlife, including fencing to prevent wildlife-vehicle collisions and wildlife crossing structures to facilitate landscape connectivity. While not necessarily explicitly articulated, the fundamental drivers behind road mitigation are human safety, animal welfare, and/or wildlife conservation. Concomitant with the increased effort to mitigate has been a focus on evaluating road mitigation. So far, research has mainly focussed on assessing the use of wildlife crossing structures, demonstrating that a broad range of species use them. However, this research has done little to address the question of the effectiveness of crossing structures, because use of a wildlife crossing structure does not necessarily equate to its effectiveness. The paucity of studies directly examining the effectiveness of crossing structures is exacerbated by the fact that such studies are often poorly designed, which limits the level of inference that can be made. Without well performed evaluations of the effectiveness of road mitigation measures, we may endanger the viability of wildlife populations and inefficiently use financial resources by installing structures that are not as effective as we think they are. In this paper we outline the essential elements of a good experimental design for such assessments and prioritize the parameters to be measured. The framework we propose will facilitate collaboration between road agencies and scientists to undertake research programs that fully evaluate effectiveness of road mitigation measures. We discuss the added value of road mitigation evaluations for policy makers and transportation agencies and provide recommendations on how to incorporate such evaluations in road planning practices.
In central Argentina, Serrano forest has a long history of fire disturbance; however, the impact of fire on avifauna remains unknown. We compared the avian–habitat relationships in forest patches with low, moderate, and high fire regimes using a community-level (species richness, abundance, ordination and guilds) and species-level (indicator species analysis) approach. In patches under each fire condition, we recorded bird community composition, richness and abundance, and different vegetation structure variables. The site under high-severity fire regime was structurally poor and had been converted from original forest to dense grassland. There, diversity of bird community was low, retaining approximately 30 % of the species present in the least impacted site. Avian assemblage was dominated by generalist and open area birds. Guilds were underrepresented, showing an important reduction of foliage granivorous, nectarivorous, omnivores, and foliage and bark insectivorous, and absence of fly-catchers. Moreover, low abundance of forest understory, midstory, and canopy species and of birds belonging to open and closed nesting guilds was detected. By contrast, under low and moderate-severity fire regimes highest bird diversity as well as highest representativeness of most guilds was observed. Forest bird species were strongly associated with low fire disturbance, whereas moderate fire disturbance was characterized by the presence of forest and generalist species. Given the critical conservation status of Serrano forest in Córdoba, Argentina, habitat restoration and protection of forest relicts could be suitable measures to promote avifauna preservation.
Median barriers separate lanes of traffic moving in opposite directions on multilane highways. Such traffic safety devices can reduce head-on collisions but also have the potential to reduce landscape permeability by impeding wildlife movements across highways. Median barriers may also increase the risk of wildlife-vehicle collisions if an animal becomes trapped or confused amid barriers searching for a place to cross. A 2002 Transportation Research Board report highlighted the need to better understand the potential impacts of highway median barriers on wildlife. This lack of information can cause significant project delays and increase transportation project costs. This study represents the first attempt in North America to bring together information about highway median and roadside barriers and wildlife and provide preliminary guidelines to balance the needs of motorist safety and wildlife movements.
Use of specific overpasses by the fauna and related mortality in a water canal on the moorlands of Guardo (Palencia province, North of Spain) A water canal of 24 km lenght lay on the moorlands of Guardo (Palencia) in northern Spain. The canal serves as a barrier to some mammal movement and an annual average of 44 to 80 animals are dead by drowning; mostly Roe deer (C. capreolus). In order to mitigate casualties, several overpasses and tunnels have been built. Narrow overpasses (2, 2,5 and 3,6 m) are used by weasels (Mustelidae), foxes and dogs but, their effectiveness is poor by wild ungulates. Wide overpasses (7,5 m) are used by sheep- herds, humans and vehicles. The frequent use of both type of overpasses by wild carnivorous as well as for sheep, could made these unsuitable by wild ungulates. Although probably wider overpasses combined with vegetation will enhance animal crossing.
Wildlife crossing structures are intended to increase permeability and habitat connectivity across roads. Few studies, however, have assessed the effectiveness of these mitigation measures in a multispecies or community level context. We used a null model to test whether wildlife crossing structures serve large mam-mal species equally or whether such structures limit habitat connectivity across roads in species-specific ways. We also modeled species responses to 14 variables related to underpass structure, landscape features, and hu-man activity. Species performance ratios (observed crossing frequency to expected crossing frequency) were evaluated for four large carnivore and three ungulate species in 11 underpass structures in Banff National Park, Alberta, Canada. Observed crossing frequencies were collected in 35 months of underpass monitoring. Expected frequencies were developed from three independent models: radio telemetry, pellet counts, and hab-itat-suitability indices. The null model showed that species responded to underpasses differently. In the pres-ence of human activity carnivores were less likely to use underpasses than were ungulates. Apart from hu-man activity, carnivore performance ratios were better correlated to landscape variables, and ungulate performance ratios were better correlated to structural variables. We suggest that future underpasses de-signed around topography, habitat quality, and location will be minimally successful if human activity is not managed.
INTRODUCCIÓN El jabalí (Sus scrofa L.) -del árabe jabal-í, literalmente "de monte" en castellano (Cortés 1996)-representa el origen genético de los actuales cerdos domésticos y es una de las especies de mamíferos más ligadas al hombre desde tiempos prehistóri-cos. Hoy en día el jabalí constituye un importante recurso económico y cinegético así como una pieza clave en los numerosos ecosistemas que ocupa. Esta importancia no se ha traducido en un profundo conocimiento de su bio-logía y ecología y solamente en las últimas dos décadas del siglo pasado su estudio ha comenzado a aportar información verdaderamente relevante sobre distintos aspectos de su historia natural y su aplicación a la gestión (Mauget et al. 1984, Gerard et al. 1991). La aplicación de nuevas técnicas de estudio junto al creciente interés que despierta la especie ha ayudado a este desarrollo.
From 1993–1998, we monitored a 24.1-km long concrete water canal in northern Spain for drowned mammals. Along the canal, 14 concrete bridges and 9 small bridges permitted crossing by humans and livestock. Our objective was to test whether those bridges could be used as passages for wild animals to prevent drowning. We used tracks recorded in sand on bridges to identify species passing. Of the bridges, 65% were used by wild mammals; the 9 small bridges accounted for 57% of crossings by wild animals. Wild and domestic canids (Canis lupus, C.l. domesticus, Vulpes vulpes) were the main users (85%), followed by wild ungulates (mainly wild boar, Sus scrofa) at 71% of the crossings. Proximity to a mountain slope did not increase crossing in deer species, but did not hinder wild boars, foxes and wolves from doing so. Up to 88.1% of the wild mammalian species selected passages that were close to scrubland or forest. Of the drowned animals observed, 70% were dogs and livestock. More roe deer (Capreolus capreolus) drowned than other species, and 73% drowned between April and October. Throughout the year, 6.5% of wild boars fell into the canal . Foxes were the main species crossing the canal, but accounted for only 2.1% of drowned species. We recommend that the following action should be taken to reduce drowning: (1) bridges that are simpler and rustic in design should be constructed and (2) water catchments should be dug into the forest to provide water, so that animals do not need to use the canal as a water source or need to cross it to reach the river.
Roads, especially large highways, can have significant impacts on wildlife movement and survival. This is especially true for wide-ranging species, such as mammalian carnivores. Some of these impacts may be mitigated if wildlife can find and utilize passageways under highways. To determine if underpasses and drainage culverts beneath highways are used by wildlife as movement corridors, we monitored 15 such passages near Los Angeles, California using remotely triggered cameras and gypsum track stations. We found that passages were used by a variety of species, including carnivores, mule deer, small mammals, and reptiles. Many types of undercrossings were utilized, indicating that passages beneath highways, even when not originally designed for wildlife, can provide important safe avenues for animals to cross roads. For mammals of conservation concern, including native carnivores and deer, passage dimensions, surrounding habitat, and the extent of human activity were assessed to determine if these factors influenced passage use by these species. Our results show that while many native mammals used passages beneath highways, the presence of suitable habitat on either side of the passage was a particularly important factor predicting use. For deer and coyotes, passage dimensions were also important and should be considered with the presence of suitable habitat when wildlife passages are planned or evaluated. To increase the likelihood of utilization and to help prevent animals from crossing road surfaces, we suggest that simple improvements such as habitat restoration near crossing points and animal-proof fencing that serves to funnel wildlife to passages, can facilitate animal movement between fragmented habitats that are bisected by roads.
Abstract A huge road network with vehicles ramifies across the land, representing a surprising frontier of ecology. Species-rich roadsides are conduits for few species. Roadkills are a premier mortality source, yet except for local spots, rates rarely limit population size. Road avoidance, especially due to traffic noise, has a greater ecological impact. The still-more-important barrier effect subdivides populations, with demographic and probably genetic consequences. Road networks crossing landscapes cause local hydrologic and erosion effects, whereas stream networks and distant valleys receive major peak-flow and sediment impacts. Chemical effects mainly occur near roads. Road networks interrupt horizontal ecological flows, alter landscape spatial pattern, and therefore inhibit important interior species. Thus, road density and network structure are informative landscape ecology assays. Australia has huge road-reserve networks of native vegetation, whereas the Dutch have tunnels and overpasses perforating road barriers to enhance ecological flows. Based on road-effect zones, an estimated 15–20% of the United States is ecologically impacted by roads.
We measured the impact of prescribed summer and winter burns on vegetation characteristics and spring abundance of birds in a Spartina/Paspalum grassland at Matagorda Island National Wildlife Refuge and State Natural Area, Texas, 1993-94. We burned 8 (4 summer burn, 4 winter burn), 122-ha plots. We estimated bird abundance by surveying once a week from March through May at 12-16 fixed-radius point count stations in each plot. We measure forb and grass foliar cover, Utter depth, visual obstruction, and woody and residual stem density at each point count station 6-10 months after burning and 18-22 months after burning and found few differences in vegetation between summer and winter burns. Litter depth, visual obstruction, and woody stem density values were greater on control plots 6 to 10 months post-burn. By 18 to 22 months post-burn, only litter depth and visual obstruction remained higher on control plots than on either burn treatment. At 6 to 10 months after burnings, wrens were more abundant on control plots and sparrows were more abundant on the burned plots. By 18 to 22 months post-burn, wren abundance had increased on the burned plots, but was stiff highest on control plots. Sparrow abundance remained high on burned plots 18-22 month after burning. Precipitation was higher in 1993 than 1994; we believe blackbirds responded more to annual precipitation differences than to burning treatment. In this coastal island grassland, wren abundance was highest on unburned plots and sparrow abundance was highest on burned plots. We suggest that land managers could burn at > 2 year intervals in this grassland without negatively impacting most resident bird species.
Wildlife crossing structures are one solution to mitigating the fragmentation of wildlife populations caused by roads, but their effectiveness in providing connectivity has only been superficially evaluated. Hundreds of grizzly (Ursus arctos) and black bear (Ursus americanus) passages through under and overpasses have been recorded in Banff National Park, Alberta, Canada. However, the ability of crossing structures to allow individual and population-level movements across road networks remains unknown. In April 2006, we initiated a 3-year investigation into whether crossing structures provide demographic connectivity for grizzly and black bears in Banff National Park. We collected hair with multiple noninvasive methods to obtain genetic samples from grizzly and black bears around the Bow Valley. Our objectives were to determine the number of male and female grizzly and black bears that use crossing structures; examine spatial and temporal patterns of crossings; and estimate the proportions of grizzly and black bear populations in the Bow Valley that use crossing structures. Fifteen grizzly (7 female, 8 male) and 17 black bears (8 female, 9 male) used wildlife crossing structures. The number of individuals detected at wildlife crossing structures was highly correlated with the number of passages in space and time. Grizzly bears used open crossing structures (e.g., overpasses) more often than constricted crossings (e.g., culverts). Peak use of crossing structures for both bear species occurred in July, when high rates of foraging activity coincide with mating season. We compared the number of bears that used crossings with estimates of population abundance from a related study and determined that substantial percentages of grizzly (15.0% in 2006, 19.8% in 2008) and black bear (17.6% in 2006, 11.0% in 2008) populations used crossing structures. On the basis of our results, we concluded wildlife crossing structures provide demographic connectivity for bear populations in Banff National Park.
Conectividad Demográfica para Poblaciones de Úrsidos en Estructuras para Cruce de Vida Silvestre en el Parque Nacional Banff
Las estructuras para el cruce de vida silvestre son una solución para mitigar la fragmentación de poblaciones de vida silvestre provocada por los caminos, pero su efectividad para proporcionar conectividad ha sido evaluada solo superficialmente. Se han registrado cientos de pasadas de osos grizzli (Ursus arctos) y osos negros (U. americanus) en los cruces del Parque Nacional Banff, Alberta, Canadá. Sin embargo, se desconoce la capacidad de las estructuras de cruce para permitir movimientos individuales y a nivel población. En abril 2006, iniciamos una investigación de 3 años para conocer si las estructuras de cruce proporcionan conectividad demográfica para osos grizzli y negros en el Parque Nacional Banff. Recolectamos pelo mediante múltiples métodos no invasivos para obtener muestras genéticas de osos grizzli y negros alrededor del Valle Bow. Nuestros objetivos fueron determinar los patrones espaciales y temporales de los cruces; y estimar las proporciones de las poblaciones de osos grizzli y negros que utilizan estructuras de cruce. Quince osos grizzli (7 hembras, 8 machos) y 17 osos negros (8 hembras, 9 machos) utilizaron estructuras de cruce. El número de individuos detectados en las estructuras de cruce se correlacionó estrechamente con el número de pasadas en espacio y tiempo. Los osos grizzli utilizaron estructuras de cruce abiertas (e.g., puentes) más frecuentemente que los cruces compactos (e.g., alcantarillas). El pico del uso de estructuras de cruce para ambas especies de osos ocurrió en julio, cuando las altas tasas de actividad forrajera coinciden con la temporada de apareamiento. Comparamos el número de osos que utilizaron cruces con estimaciones de la abundancia poblacional de un estudio relacionado y determinamos que porcentajes sustanciales de las poblaciones de osos grizzli (15.0% en 2006, 19.8% en 2008) y de osos negros (17.6% en 2006, 11.0% en 2008) utilizaron las estructuras de cruce. Con base en nuestros resultados, concluimos que las estructuras de cruce proporcionan conectividad demográfica a poblaciones de osos en el Parque Nacional Banff.
The southernmost extension of tropical Andean–Amazonian forests protrudes into the arid to semiarid habitats in northwestern Argentina. We analyzed the decline of species richness of forest mammals along these Yungas forests. In particular, we tested whether species decline is due to a general latitudinal effect and whether the drop of species from the assemblages was independent from species' traits and environmental variables. For these tests, we estimated the geographic range edges of 39 species of forest mammal and estimated the species richness with bands of 30′. First, we compared the slope of the decline of species richness from north to south (5.8 species/degree) with the decline expected from the latitudinal species gradient (1–3 species/degree). The decline in species richness of forest mammals along the Yungas was significantly steeper than expected. Second, with a null model assuming a random drop of mammal species we derived confidence limits for the expected species richness and number of range edges within the bands. None of the forest mammals reached the tip of the forest, in marked contrast to nonforest mammals. More range edges than expected from the null model fell within the bands 23°30′–24°00′ S and a band near the tip of the Yungas indicating a nonrandom drop of species. The correlation between vulnerability traits and range edges suggests that processes associated with the availability of resources influence the drop of species. We propose that a suite of macroecological attributes interacting with a decrease in habitat quality determines the pattern of species richness in the Yungas forest.
The movement of vertebrates through 17 culverts under roads and railways in Central Spain was analysed over the course of an annual cycle. Passage was detected for amphibians, lizards, snakes, small mammals, rats, hedgehogs, rabbits and several species of carnivorous mammals, including Felis sylvestris and Genetta genetta. The intensity of animal movement, which varied considerably among the groups, was influenced by various factors such as the culvert dimensions, road width, height of boundary fence, the complexity of the vegetation along the route, and the presence of detritus pits at the entrance of culverts. It is concluded that adequately designed culverts can aid the conservation of vertebrate populations.
Numerous road and railway construction projects include costly mitigation measures to offset the barrier effect produced on local fauna, despite the scarcity of data on the effectiveness of such mitigation measures. In this study, we evaluate the utility of different types of crossing structures. Vertebrate use of 43 transverse crossing structures along the A-52 motorway (north-western Spain) was studied during spring 2001. Research centered on wildlife passages (9), wildlife-adapted box culverts (7), functional passages (6 overpasses, 7 underpasses) and culverts (14), with marble dust being used to record animal tracks. A total of 424 track-days were recorded, with most of the larger vertebrate groups present in the area being detected. All crossing structure types were used by animals, although the intensity of use varied significantly among them (Kruskal-Wallis test, p<0.05); culverts were used less frequently than other structures. Crossing structure type and width were identified as the most important factors in their selection for use. Wildlife passages and adapted culverts allowed crossing by certain species (wild boar, roe deer, Eurasian badger), which do not tend to cross elsewhere. These results highlight the importance of using both mixed-type structures and wildlife passages in reducing the barrier effect of roads.
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