983 resultados para habitat type


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Background: The European badger (Melesmeles) is involved in the maintenance of bovine tuberculosis infection and onward spread to cattle. However, little is known about how transmission occurs. One possible route could be through direct contact between infected badgers and cattle. It is also possible that indirect contact between cattle and infected badger excretory products such as faeces or urine may occur either on pasture or within and around farm buildings. A better understanding of behaviour patterns in wild badgers may help to develop biosecurity measures to minimise direct and indirect contact between badgers and cattle. However, monitoring the behaviour of free-ranging badgers can be logistically challenging and labour intensive due to their nocturnal and semi-fossorial nature.We trialled a GPS and tri-axial accelerometer-equipped collar on a free-ranging badger to assess its potential value to elucidate behaviour-time budgets and functional habitat use. Results: During the recording period between 16:00 and 08:00 on a single night, resting was the most commonly identified behaviour (67.4%) followed by walking (20.9%), snuffling (9.5%) and trotting (2.3%).When examining accelerometer data associated with each GPS fix and habitat type (occurring 2 min 30 s before and after), walking was themost common behaviour in woodland (40.3%) and arable habitats (53.8%), while snuffling was themost common behaviour in pasture (61.9%). Several nocturnal resting periods were also observed. The total distance travelled was 2.28 km. Conclusions: In the present report, we demonstrate proof of principle in the application of a combined GPS and accelerometer device to collect detailed quantitative data on wild badger behaviour. Behaviour-time budgets allow us to investigate how badgers allocate energy to different activities and how thismight change with disease status. Such information could be useful in the development of measures to reduce opportunities for onward transmission of bovine tuberculosis from badgers to cattle.

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How does fire affect the plant and animal community of the boreal forest? This study attempted to examine the changes in plant composition and productivity, and small mammal demography brought about by fire in the northern boreal environment at Chick Lake, N.W.T. (65053fN, 128°14,W). Two 5*6 ha plots measuring 375m x 150m were selected for study during the summers of 1973 and 197^. One had been unburned for 120 years, the other was part of a fire which burned in the spring of 1969. Grids of 15m x 15m were established in each plot and meter square quadrats taken at each of the 250 grid intersections in order to determine plant composition and density. Aerial primary production was assessed by clipping and drying 80 samples of terminal new production for each species under investigation. Small mammal populations were sampled by placing a Sherman live trap at each grid intersection for ten days in every month. The two plots were similar in plant species composition which suggested that most regrowth in the burned area was from rootstocks which survived the fire. The plant data were submitted to a cluster analysis that revealed nine separate species associations, six of which occured in the burned area and eight of which occured in the control. These were subsequently treated as habitats for purposes of comparison with small mammal distributions. The burned area showed a greater productivity in flowers and fruits although total productivity in the control area was higher due to a large contribution from the non-vascular component. Maximum aerial productivity as dry wieght was measured at 157.1 g/m and 207.8 g/m for the burn and control respectively. Microtus pennsylvanicus and Clethrionomys rutilus were the two most common small mammals encountered; Microtus xanthognathus, Synaptomys borealis, and Phenacomys intermedius also occured in the area. Populations of M. pennsylvanicus and C. rutilus were high during the summer of 1973; however, M. pennsylvanicus was rare on the control but abundant on the burn, while C. rutilus was rare on the burn but abundant in the control. During the summer of 197^ populations declined, with the result that few voles of any species were caught in the burn while equal numbers of the two species were caught in the control. During the summer of 1973 M. pennsylvanicus showed a positive association to the most productive habitat type in the burn which was avoided by C. rutilus. In the control £• rutilus showed a similar positive association to the most productive habitat type which was avoided by M. pennsylvanicus. In all cases for the high population year of 1973# the two species never overlapped in habitat preference. When populations declined in 197^f "both species showed a strong association for the most productive habitat in the control. This would suggest that during a high population year, an abundant species can exclude competitors from a chosen habitat, but that this dominance decreases as population levels decrease. It is possible that M. pennsylvanicus is a more efficient competitor in a recently burned environment, while C. rutilus assumes this role once non-vascular regrowth becomes extensive.

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Breeding seabirds are threatened by human activities that affect nesting and foraging habitat. In Canada, one of the seabirds most at risk of extirpation is the Roseate Tern, Sterna dougallii. Although critical nesting habitat has been identified for the Roseate Tern in Canada, its foraging locations and the diet of its chicks are unknown. Therefore, our goal was to determine the foraging locations and diet of chicks of Roseate Tern breeding on Country Island, Nova Scotia, which is one of Canada's two main breeding colonies. In 2003 and 2004, we radio-tracked the Roseate Tern by plane to locate foraging areas and conducted feeding watches to determine the diet of chicks. Roseate Tern foraged approximately 7 km from the breeding colony over shallow water < 5 m deep. In both years, sand lance, Ammodytes spp., was the most common prey item delivered to chicks, followed by hake, Urophycis spp. Our results are consistent with previous work at colonies in the northeastern United States, suggesting that throughout its range, this species may be restricted in both habitat use and prey selection. The reliance on a specific habitat type and narrow range of prey species makes the Roseate Tern generally susceptible to habitat perturbations and reductions in the availability of prey.

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The UK population of the Spotted Flycatcher Muscicapa striata has declined markedly in the last 30 years but there have been few recent studies of the species. This study examined the relationship between nest success and the predominant habitat type around Spotted Flycatcher nests in two contrasting areas of England. A breeding population in eastern England, a region where numbers of Spotted Flycatchers are known to have decreased dramatically in recent decades, was compared with another in southwest England, where numbers have remained stable or even increased. Whilst there was no difference in breeding success between the two study areas, there were significant differences between habitats, with garden nests more successful than those in farmland or woodland, at both egg and chick stages. Estimates of productivity per nesting attempt were also lower in farmland and woodland, with nests in gardens fledging twice as many chicks as those in either woodland or farmland. The proximate cause of lower success in farmland and woodland was higher nest predation rates during both egg and chick stages. In terms of nesting success, farmland and woodland appear to be similar in quality for this species, but both appear to be suboptimal habitats when compared with gardens, providing evidence of a problem on the breeding grounds for this species, in at least these two habitats.

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The UK population of the Spotted Flycatcher Muscicapa striata has declined markedly in the last 30 years but there have been few recent studies of the species. This study examined the relationship between nest success and the predominant habitat type around Spotted Flycatcher nests in two contrasting areas of England. A breeding population in eastern England, a region where numbers of Spotted Flycatchers are known to have decreased dramatically in recent decades, was compared with another in southwest England, where numbers have remained stable or even increased. Whilst there was no difference in breeding success between the two study areas, there were significant differences between habitats, with garden nests more successful than those in farmland or woodland, at both egg and chick stages. Estimates of productivity per nesting attempt were also lower in farmland and woodland, with nests in gardens fledging twice as many chicks as those in either woodland or farmland. The proximate cause of lower success in farmland and woodland was higher nest predation rates during both egg and chick stages. In terms of nesting success, farmland and woodland appear to be similar in quality for this species, but both appear to be suboptimal habitats when compared with gardens, providing evidence of a problem on the breeding grounds for this species, in at least these two habitats.

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Faunal atlases are landscape-level survey collections that can be used for describing spatial and temporal patterns of distribution and densities. They can also serve as a basis for quantitative analysis of factors that may influence the distributions of species. We used a subset of Birds Australia’s Atlas of Australian Birds data (January 1998 to December 2002) to examine the spatio-temporal distribution patterns of 280 selected species in eastern Australia (17–37°S and 136–152°E). Using geographical information systems, this dataset was converted into point coverage and overlaid with a vegetation polygon layer and a half-degree grid. The exploratory data analysis involved calculating species-specific reporting rates spatially, per grid and per vegetation unit, and also temporally, by month and year. We found high spatio-temporal variability in the sampling effort. Using generalised linear models on unaggregated point data, the influences of four factors – survey method and month, geographical location and habitat type – were analysed for each species. When counts of point data were attributed to grid-cells, the total number of species correlated with the total number of surveys, while the number of records per species was highly variable. Surveys had high interannual location fidelity. The predictive values of each of the four factors were species-dependent. Location and habitat were correlated and highly predictive for species with restricted distribution and strong habitat preference. Month was only of importance for migratory species. The proportion of incidental sightings was important for extremely common or extremely rare species. In conclusion, behaviour of species differed sufficiently to require building a customized model for each species to predict distribution. Simple models were effective for habitat specialists with restricted ranges, but for generalists with wide distributions even complex models gave poor predictions.

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1. The Grampians National Park in Victoria is a 'hot spot' for freshwater crayfish diversity, with seven species from six genera occurring in sympatry. Few studies have examined how multiple species of freshwater crayfish co-exist across landscapes consisting of a mosaic of perennial and seasonal habitats. Despite their endemicity and likely key role in freshwaters, the ecology and biology of these crayfish remains unknown.

2. This study determined the distribution and habitat use of five crayfish species (Euastacus bispinosus, Cherax destructor, Geocharax falcata, Gramastacus insolitus and Engaeus lyelli). Seasonal sampling surveys ascertained whether crayfish distribution was related to habitat type, environmental or physicochemical variables, catchment or season.

3. Distribution was directly related to habitat type and the environmental and physicochemical variables that characterised habitats. Engaeus lyelli, G. falcata and G. insolitus occurred predominantly in floodplain wetlands and flooded vegetation habitats, E. bispinosus occurred only in flowing soft-sediment channels and C. destructor was found in all catchments and habitat types studied. Gramastacus insolitus co-occurred with G. falcata at all sites except two, so no distinct habitat separations were apparent for these two species.

4. A high percentage cover of boulders was the best indicator of crayfish absence, and discriminated between habitat types and crayfish species: it was probably a surrogate for a larger range of environmental and physicochemical variables. Catchment and season did not affect crayfish distribution.

5. These crayfish species varied in their degree of habitat specialisation from strongly generalist (C. destructor) to occupying only a specific habitat type (E. bispinosus). Some species appeared specialised for seasonal wetlands (G. insolitus and G. falcata). Overlap in site occupancy also varied: G. insolitus and G. falcata distributions were strongly associated, whereas C. destructor appeared to occur opportunistically across habitats, both alone and co-occurring with all the other species.

6. Management strategies to conserve multiple species of crayfish co-existing within landscapes will need to incorporate a range of perennial and seasonal habitat types to ensure sufficient space is available for species to maintain different occupancy patterns. Given that water resources are under increasing pressure and are strongly regulated within the Grampians National Park, this may present a conservation challenge to water managers in this location.

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Studies of post-dispersal seed removal in the Neotropics have rarely examined the magnitude of seed removal by different types of granivores. The relative impact of invertebrates, small rodents, and birds on seed removal was investigated in a 2,178 ha Atlantic forest fragment in southeastern Brazil. We used popcorn kernels (Zea mays-Poaceae) to investigate seed removal in a series of selective exclosure treatments in a replicated, paired design experiment that included forest understory, gaps, and forest edge sites. We recorded the vegetation around the experimental seed stations in detail in order to evaluate the influence of microhabitat traits on seed removal. Vertebrate granivores (rodents and birds) were surveyed to determine whether granivore abundance was correlated with seed removal levels. Seed removal varied spatially and in unpredictable ways at the study site. Seed encounter and seed use varied with treatments, but not with habitat type. However, seed removal by invertebrates was negatively correlated with gap-related traits, which suggested an avoidance of large gaps by granivorous ants. The abundance of small mammals was remarkably low, but granivorous birds (tinamous and doves) were abundant at the study site. Birds were the main seed consumers in open treatments, but there was no correlation between local granivorous bird abundance and seed removal. These results emphasize the stochastic spatial pattern of seed removal, and, contrary to previous studies, highlight the importance of birds as seed predators in forest habitats. (c) 2007 Elsevier Masson SAS. All rights reserved.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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In most habitats, vegetation provides the main structure of the environment. This complexity can facilitate biodiversity and ecosystem services. Therefore, measures of vegetation structure can serve as indicators in ecosystem management. However, many structural measures are laborious and require expert knowledge. Here, we used consistent and convenient measures to assess vegetation structure over an exceptionally broad elevation gradient of 866–4550m above sea level at Mount Kilimanjaro, Tanzania. Additionally, we compared (human)-modified habitats, including maize fields, traditionally managed home gardens, grasslands, commercial coffee farms and logged and burned forests with natural habitats along this elevation gradient. We distinguished vertical and horizontal vegetation structure to account for habitat complexity and heterogeneity. Vertical vegetation structure (assessed as number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) displayed a unimodal elevation pattern, peaking at intermediate elevations in montane forests, whereas horizontal structure (assessed as coefficient of variation of number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) was lowest at intermediate altitudes. Overall, vertical structure was consistently lower in modified than in natural habitat types, whereas horizontal structure was inconsistently different in modified than in natural habitat types, depending on the specific structural measure and habitat type. Our study shows how vertical and horizontal vegetation structure can be assessed efficiently in various habitat types in tropical mountain regions, and we suggest to apply this as a tool for informing future biodiversity and ecosystem service studies.

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Utilisation by fish of different estuarine habitats is known to vary at many different temporal scales, however no study to date has examined how utilisation varies at all the relevant times scales simultaneously. Here, we compare the utilisation by fish of sandy, intertidal foreshore habitats in a subtropical estuary at four temporal scales: between major spawning periods (spring/ summer and winter), among months within spawning periods, between the full and new moon each month, and between night and day within those lunar phases. Comparisons of assemblage composition, abundance of individuals and of fish in seven different,ecological guilds' were used to identify the temporal scales at which fish varied their use of unvegetated sandy habitats in the lower Noosa Estuary, Queensland, Australia. Fish assemblages were sampled with a seine net at three different regions. The most numerically dominant species caught were southern herring (Herklotsichthys castelnaui: Clupeidae), sand whiting (Sillago ciliata: Sillaginidae), weeping toadfish (Torquigener pleurogramma: Tetraodomidae), and silver biddy (Gerres subfasciatus: Gerreidae). Considerable variation at a range of temporal scales from short term (day versus night) to longer term (spawning periods) was detected for all but one of the variables examined. The clearest patterns were observed for diurnal effects, where generally abundance was greater at night than during the day. There were also strong lunar effects, although there were no consistent patterns between full moon and new moon periods. Significant differences among months within spawning periods were more common than differences between the actual spawning periods. The results clearly indicate that utilisation of sandy, unvegetated estuarine habitats is very dynamic and highly variable in space and time. (c) 2006 Elsevier B.V. All rights reserved.

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Rodents are often involved at several stages of trophic dynamics. Consequently they often play crucial roles in the structure and function of many complex ecological systems. This study sought to address the lack of baseline data concerning rodents in tropical areas, and south Florida in particular. Live trapping took place in the four major habitat types of the Long Pine Key area of Everglades National Park over the course of one year. I compared population structures and abundance of murid rodents in the four habitat types, and tested multiple weather variables for their effectiveness as predictors of rodent abundance. I found the Long Pine Key area to be depauperate in terms of species diversity. Each of the four species of rodent encountered favored a particular habitat type. The density of the understory vegetation and the avoidance of avian predators in particular appear to be the most important factors in the distribution and abundance of rodents in the Long Pine Key area of Everglades National Park.

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There are several abiotic factors reported in the literature as regulators of the distribution of fish species in marine environments. Among them stand out structural complexity of habitat, benthic composition, depth and distance from the coast are usually reported as positive influencers in the diversity of difentes species, including reef fish. These are dominant elements in reef systems and considered high ecological and socioeconomic importance. Understanding how the above factors influence the distribution and habitat use of reef fish communities are important for their management and conservation. Thus, this study aims to evaluate the influence of these variables on the community of reef fishes along an environmental gradient of depth and distance from shore base in sandstone reefs in the coast of state of Rio Grande do Norte, Brazil. These variables are also used for creating a simple predictive model reef fish biomass for the environment studied. Data collection was performed through visual surveys in situ, and recorded environmental data (structural complexity of habitat, type of coverage of the substrate, benthic invertebrates) and ecological (wealth, abundance and reef fish size classes). As a complement, information on the diet were raised through literature and the biomass was estimated from the length-weight relationship of each species. Overall, the reefs showed a low coverage by corals and the Shallow reefs, Intermediate I and II dominated by algae and the Funds by algae and sponges. The complexity has increased along the gradient and positively influenced the species richness and abundance. Both attributes influenced in the structure of the reef fish community, increasing the richness, abundance and biomass of fish as well as differentiating the trophic structure of the community along the depth gradient and distance from the coast. Distribution and use of habitat by recifas fish was associated with food availability. The predictor model identified depth, roughness and coverage for foliose algae, calcareous algae and soft corals as the most significant variables influencing in the biomass of reef fish. In short, the description and understanding of these patterns are important steps to elucidate the ecological processes. In this sense, our approach provides a new understanding of the structure of the reef fish community of Rio Grande do Norte, allowing understand a part of a whole and assist future monitoring actions, evaluation, management and conservation of these and other reefs of Brazil.

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Dry river beds are common worldwide and are rapidly increasing in extent due to the effects of water management and prolonged drought periods due to climate change. While attention has been given to the responses of aquatic invertebrates to drying rivers, few studies exist on the terrestrial invertebrates colonizing dry river beds. Dry river beds are physically harsh and they often differ substantially in substrate, topography, microclimate and inundation frequency from adjacent riparian zones. Given these differences, we predicted that dry river beds provide a unique habitat for terrestrial invertebrates, and that their assemblage composition differs from that in adjacent riparian zones. Dry river beds and riparian zones in Australia and Italy were sampled for terrestrial invertebrates with pitfall traps. Sites differed in substrate type, climate and flow regime. Dry river beds contained diverse invertebrate assemblages and their composition was consistently different from adjacent riparian zones, irrespective of substrate, climate or hydrology. Although some taxa were shared between dry river beds and riparian zones, 66 of 320 taxa occurred only in dry river beds. Differences were due to species turnover, rather than shifts in abundance, indicating that dry river bed assemblages are not simply subsets of riparian assemblages. Some spatial patterns in invertebrate assemblages were associated with environmental variables (irrespective of habitat type), but these associations were statistically weak. We suggest that dry river beds are unique habitats in their own right. We discuss potential human stressors and management issues regarding dry river beds and provide recommendations for future research.

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Approximately 90% of the original woodlands of the Mount Lofty Ranges of South Australia has been cleared, modified or fragmented, most severely in the last 60 years, and affecting the avifauna dependent on native vegetation. This study identifies which woodland-dependent species are still declining in two different habitats, Pink GumBlue Gum woodland and Stringybark woodland. We analyse the Mount Lofty Ranges Woodland Bird Long-Term Monitoring Dataset for 1999-2007, to look for changes in abundance of 59 species. We use logistic regression of prevalence on lists in a Bayesian framework, and List Length Analysis to control for variation in detectability. Compared with Reporting Rate Analysis, a more traditional approach, List Length Analysis provides tighter confidence intervals by accounting for changing detectability. Several common species were declining significantly. Increasers were generally large-bodied generalists. Many birds have already disappeared from this modified and naturally isolated woodland island, and our results suggest that more specialist insectivores are likely to follow. The Mount Lofty Ranges can be regarded as a 'canary landscape' for temperate woodlands elsewhere in Australia without immediate action their bird communities are likely to follow the trajectory of the Mount Lofty Ranges avifauna. Alternatively, with extensive habitat restoration and management, we could avoid paying the extinction debt. © Royal Australasian Ornithologists Union 2011.