Predation is increasingly pointed out as one of the factors contributing to population declines of ground-nesting farmland birds, though it remains poorly understood how ongoing transformations of ...agricultural landscapes affect predator assemblages. This study addressed this issue, estimating the contribution of landscape composition and configuration to spatial variation in species richness and abundances of mammalian carnivores across a gradient of agricultural intensification in southern Portugal. The carnivore assemblage was diverse (10 species), but it was largely dominated by just three widespread and abundant species of generalist predators: domestic dog (Canis familiaris), red fox (Vulpes vulpes) and Egyptian mongoose (Herpestes ichneumon). The number of domestic carnivore species and the abundance of cats (Felis catus) increased along with farmland occupation by human dwellings, whereas dogs were not responsive to landscape variables. The species richness of wild carnivores was highest in landscapes with a patchwork of arable fields and semi-natural habitats such as forests and shrubland, though it was also high in irrigated landscapes with dense networks of irrigation channels and tree lines bordering agricultural fields. Irrigation was also positively associated with the abundance of otters (Lutra lutra) and mongooses. Cats, foxes, badgers (Meles meles), and total and wild carnivore abundances, were positively affected by increasing cover by eucalyptus and pine forest plantations. In general, results suggest that the highest diversity and abundance of carnivores in Mediterranean farmland may occur in mosaic landscapes with small agricultural fields, high cover by woody vegetation patches and corridors, and many human dwellings. Preventing scrub encroachment and afforestation may thus be necessary to maintain a low predation risk in open farmland habitats, which are often inhabited by ground-nesting birds of high conservation concern. Conversely, keeping shrubland and forest patches within farmed landscapes may be essential where carnivore persistence is a relevant conservation goal.
Robust and selective quantification methods are required to better analyze feed supplementation effectiveness with specific amino acids. In this work, a reversed-phase high-performance liquid ...chromatography method with fluorescence detection is proposed and validated for lysine quantification, one of the most limiting amino acids in ruminant nutrition and essential towards milk production. To assess and widen method applicability, different matrices were considered: namely Li2CO3 buffer (the chosen standard reaction buffer), phosphate buffer solution (to mimic media in cellular studies), and rumen inoculum. The method was validated for all three matrices and found to be selective, accurate (92% ± 2%), and precise at both the inter- and intra-day levels in concentrations up to 225 µM, with detection and quantification limits lower than 1.24 and 4.14 µM, respectively. Sample stability was evaluated when stored at room temperature, 4 °C, and −20 °C, showing consistency for up to 48 h regardless of the matrix. Finally, the developed method was applied in the quantification of lysine on real samples. The results presented indicate that the proposed method can be applied towards free lysine quantification in ruminant feeding studies and potentially be of great benefit to dairy cow nutrition supplementation and optimization.
Zinc is an essential trace element, required for enzymatic, structural, and regulatory functions. As body reserves are scarce, an adequate zinc status relies on proper dietary supply and efficient ...homeostasis. Several biomarkers have been proposed that enable the detection of poor zinc status, but more sensitive and specific ones are needed to detect marginal deficiencies. The zinc content of commercial dry dog foods has great variability, with a more frequent non-compliance with the maximum authorized limit than with the nutritional requirement. The bioavailability of dietary zinc also plays a crucial role in ensuring an adequate zinc status. Despite controversial results, organic zinc sources have been considered more bioavailable than inorganic sources, albeit the zinc source effect is more evident after a restriction period of dietary zinc. Many disorders have been associated with inadequate zinc status, not being clear whether the occurrence of the disease is the consequence or the cause. This review presents data on zinc requirements and biomarkers for zinc status, that can be applied for the development of supplementation strategies of zinc in complete pet foods. Moreover, it provides an understanding of the role zinc plays in the health of dogs, and how altered zinc status affects diseases in dogs.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Finding achievable ways to reduce roads’ impacts on wildlife is a conservation priority. Road verges may be important refuges for small fauna, making them good hunting sites for predators. These make ...both prey and predators vulnerable to vehicle collisions. Thus, actions aiming to dissuade these animals from approaching roads are needed. Here we tested the effectiveness of ultrasonic devices to keep rodents away from the road verges. We hypothesised that exposing rodents to ultrasounds will cause them to stay away from the device and, consequently, from the road. We sampled rodents before and after the devices were switched on. Our results showed a reduction in animal activity after 10 days with the devices on. The next step is to analyse if this behaviour translates in a reduction of wildlife-vehicle collisions of rodents and their predators.
The amino acid requirements of high-production dairy cows represent a challenge to ensuring that their diet is supplied with available dietary resources, and thus supplementation with protected amino ...acids is necessary to increase their post-ruminal supply. Lysine is often the most limiting amino acid in corn-based diets. The present study proposes the use of lipid nanoparticles as novel rumen-bypass systems and assesses their capability to carry lysine. Solid lipid nanoparticles, nanostructured lipid carriers and multiple lipid nanoparticles were considered and their resistance in a rumen inoculum collected from fistulated cows was assessed. All nanoparticles presented diameters between 200-500 nm and surface charges lower than -30 mV. Lysine encapsulation was achieved in all nanoparticles, and its efficiency ranged from 40 to 90%. Solid lipid nanoparticles composed of arachidic or stearic acids and Tween 60 resisted ruminal digestion for up to 24 h. The nanoparticles were also proven to protect their lysine content from the ruminal microbiota. Based on our findings, the proposed nanoparticles represent promising candidates for rumen-bypass approaches and should be studied further to help improve the current technologies and overcome their limitations.
Road mortality is probably the best-known and visible impact of roads upon wildlife. Although several factors influence road-kill counts, carcass persistence time is considered the most important ...determinant underlying underestimates of road mortality. The present study aims to describe and model carcass persistence variability on the road for different taxonomic groups under different environmental conditions throughout the year; and also to assess the effect of sampling frequency on the relative variation in road-kill estimates registered within a survey.
Daily surveys of road-killed vertebrates were conducted over one year along four road sections with different traffic volumes. Survival analysis was then used to i) describe carcass persistence timings for overall and for specific animal groups; ii) assess optimal sampling designs according to research objectives; and iii) model the influence of road, animal and weather factors on carcass persistence probabilities. Most animal carcasses persisted on the road for the first day only, with some groups disappearing at very high rates. The advisable periodicity of road monitoring that minimizes bias in road mortality estimates is daily monitoring for bats (in the morning) and lizards (in the afternoon), daily monitoring for toads, small birds, small mammals, snakes, salamanders, and lagomorphs; 1 day-interval (alternate days) for large birds, birds of prey, hedgehogs, and freshwater turtles; and 2 day-interval for carnivores. Multiple factors influenced the persistence probabilities of vertebrate carcasses on the road. Overall, the persistence was much lower for small animals, on roads with lower traffic volumes, for carcasses located on road lanes, and during humid conditions and high temperatures during the wet season and dry seasons, respectively.
The guidance given here on monitoring frequencies is particularly relevant to provide conservation and transportation agencies with accurate numbers of road-kills, realistic mitigation measures, and detailed designs for road monitoring programs.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Roads represent one of the main sources of wildlife mortality, population decline, and isolation, especially for low-vagility animal groups. It is still not clearly understood how wildlife ...populations respond to these negative effects over space and time. Most studies on wildlife road mortality do not consider the spatial and temporal components simultaneously, or the imperfect roadkill detection, both of which could lead to inaccurate assumptions and unreliable mitigation actions. In this study, we applied a multi-season occupancy model to a 14-year amphibian mortality dataset collected along 120 km of roads, combined with freely available landscape and remote sensing metrics, to identify the spatiotemporal patterns of amphibian roadkill in a Mediterranean landscape in Southern Portugal. Our models showed an explicit general decrease in amphibian roadkill. The Iberian painted frog (Discoglossus galganoi) experienced roadkill declines over time of ∼70 %, while the spiny common toad (Bufo spinosus) and the fire salamander (Salamandra salamandra) had a loss of nearly 50 %, and the Southern marbled newt (Triturus pygmaeus) had 40 %. Despite the decreasing trend in roadkill, spatial patterns seem to be rather stable from year to year.
Multi-season occupancy models, when combined with relevant landscape and remote sensing predictors, as well as long-term monitoring data, can describe dynamic changes in roadkill over space and time. These patterns are valuable tools for understanding roadkill patterns and drivers in Mediterranean landscapes, enabling the differentiation of road sections with varying roadkill over time. Ultimately, this information may contribute to the development of effective conservation measures.
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•Amphibians are currently the most road-killed vertebrate group.•We studied spatiotemporal patterns of roadkill in a Mediterranean landscape.•We applied multi-season occupancy models to 14-year mortality data.•Roadkill trends decreased in the study area in all analysed species.•Assessment of amphibian populations living near roads is urgently required.
Context
Understanding connectivity patterns in relation to habitat fragmentation is essential to landscape management. However, connectivity is often judged from expert opinion or species occurrence ...patterns, with very few studies considering the actual movements of individuals. Path selection functions provide a promising tool to infer functional connectivity from animal movement data, but its practical application remains scanty.
Objectives
We aimed to describe functional connectivity patterns in a forest carnivore using path-level analysis, and to explore how connectivity is affected by land cover patterns and road networks.
Methods
We radiotracked 22 common genets in a mixed forest-agricultural landscape of southern Portugal. We developed path selection functions discriminating between observed and random paths in relation to landscape variables. These functions were used together with land cover information to map conductance surfaces.
Results
Genets moved preferentially within forest patches and close to riparian habitats. Functional connectivity declined with increasing road density, but increased with the proximity of culverts, viaducts and bridges. Functional connectivity was favoured by large forest patches, and by the presence of riparian areas providing corridors within open agricultural land. Roads reduced connectivity by dissecting forest patches, but had less effect on riparian corridors due to the presence of crossing structures.
Conclusions
Genet movements were jointly affected by the spatial distribution of suitable habitats, and the presence of a road network dissecting such habitats and creating obstacles in areas otherwise permeable to animal movement. Overall, the study showed the value of path-level analysis to assess functional connectivity patterns in human-modified landscapes.
Despite its importance for reducing wildlife-vehicle collisions, there is still incomplete understanding of factors responsible for high road mortality. In particular, few empirical studies examined ...the idea that spatial variation in roadkills is influenced by a complex interplay between road-related factors, and species-specific habitat quality and landscape connectivity.
In this study we addressed this issue, using a 7-year dataset of tawny owl (Strix aluco) roadkills recorded along 37 km of road in southern Portugal. We used a multi-species roadkill index as a surrogate of intrinsic road risk, and we used a Maxent distribution model to estimate habitat suitability. Landscape connectivity was estimated from least-cost paths between tawny owl territories, using habitat suitability as a resistance surface. We defined 10 alternative scenarios to compute connectivity, based on variation in potential movement patterns according to territory quality and dispersal distance thresholds. Hierarchical partitioning of a regression model indicated that independent variation in tawny owl roadkills was explained primarily by the roadkill index (70.5%) and, to a much lesser extent, by landscape connectivity (26.2%), while habitat suitability had minor effects (3.3%). Analysis of connectivity scenarios suggested that owl roadkills were primarily related to short range movements (<5 km) between high quality territories. Tawny owl roadkills were spatially autocorrelated, but the introduction of spatial filters in the regression model did not change the type and relative contribution of environmental variables.
Overall, results suggest that road-related factors may have a dominant influence on roadkill patterns, particularly in areas like ours where habitat quality and landscape connectivity are globally high for the study species. Nevertheless, the study supported the view that functional connectivity should be incorporated whenever possible in roadkill models, as it may greatly increase their power to predict the location of roadkill hotspots.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Roads can negatively impact ecosystems by fragmenting habitats and affecting animal movements and behaviour. One of the major noticeable effects of roads is animal mortality by vehicle collisions, a ...paramount threat to wildlife, especially for amphibians. In the context of reduced water availability, particularly in the Mediterranean region, amphibians are projected to be one of the most negatively affected animal groups. In this study, we used 14-year road mortality data collected along 120 km of roads, combined with landscape and remote sensing variables, to identify the drivers of amphibian mortality spatial patterns in a Mediterranean landscape, in Southern Portugal. We recorded 5116 carcasses belonging to five amphibian species. Generalised linear models showed that for most of the species, roadkill numbers increased with the decrease in water availability in water bodies. Also, the distance of water bodies to the roads was important in understanding amphibian roadkill patterns, with a general increase in mortality at reduced distances. Land use variables were also significant drivers for amphibian road mortality, with species-specific responses. Roadkill numbers decreased for the Iberian ribbed newt and the fire salamander in agricultural dominated areas. Our results also show an increase in roadkill numbers for the natterjack toad in areas with higher percentage of olive groves, and an opposite response for the fire salamander. We recognize the importance of long-term studies in assessing roadkill patterns, and their value for amphibian monitoring and conservation.
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