bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intensity of parasitic nematodes increases with organochlorine levels in the glaucous gull
Authors: Sagerup Kjetil , Henriksen Espen O. , Skorping Arne , Skaare Janneche Utne , Gabrielsen Geir Wing 
Published: March 2003

Summary 1. Organochlorines probably suppress immune functions in birds and mammals, but few field assessments are available. If establishment and/or survival of parasites is limited by host immunity, we would expect increased parasite intensities in animals with high organochlorine burdens, such as the glaucous gull Larus hyperboreus. 2. We collected 40 adult glaucous gulls on Bear Island in the western Barents Sea. Concentrations of nine selected polychlorinated biphenyls (PCB; 28, 52, 99, 101, 118, 138, 153, 170 and 180) and five chlorinated pesticides (hexachlorobenzene, oxychlordane, DDE, DDT and Mirex) were measured in the liver. The abundance of 12 species of intestinal helminths, including one trematode, six cestodes, four nematodes and one acanthocephalan, was determined. 3. After controlling for nutritional condition, no single parasite species was significantly associated with concentrations of PCB or chlorinated pesticides. However, the intensity of all nematodes grouped together was positively correlated with 10 of the 14 organochlorine concentrations measured. The strongest correlations were with p,p′‐DDT, Mirex, Σ9PCB, and PCB congeners 28, 118, 153, 138, 170 and 180. 4. Although correlative and collected in the absence of immunological data, these data do not refute the hypothesis that organochlorines might affect avian immune function.
The adequacy of collecting techniques for estimating species richness of grassland invertebrates
Authors: Standen Valerie 
Published: March 2003

1. There is still considerable debate about the most effective methods of sampling invertebrates in monitoring and assessment programmes. 2. The above‐ground invertebrates of a limestone grassland in north‐east England were compared between samples from pitfall traps and from a D‐vac suction trap combined with a lightweight swish net (SW/DV). 3. Over 14 000 individuals were captured, with similar numbers in the pitfall and SW/DV samples. A total of 480 species of Hemiptera, Coleoptera, Diptera and Araneae was identified and placed into 14 taxa for further analysis. 4. The pitfall sample produced species/specimen curves from which it was possible to estimate species richness for all the Coleoptera and Araneae taxa and the calypterate Schizophora. The SW/DV sample was adequate to estimate the species richness of Hemiptera, most Diptera taxa, herbivorous Coleoptera and Linyphiidae. 5. The proportion of Coleoptera and Araneae taxa that were method‐unique was higher in the pitfall sample than the SW/DV sample and vice versa for the Hemiptera and Diptera taxa. Nevertheless, a relatively high proportion of method‐unique species of most taxa was found in both sample types, indicating that they can each contribute to assessing species assemblages in grasslands. 6. Both pitfall traps and SW/DV samples are needed to estimate species richness in grasslands for all taxa except Heteroptera, Homoptera and Lycosidae. Herbivorous Coleoptera and Linyphiidae were collected in numbers adequate for assessing richness in both sample types, but more specimens were required in one or other sample for the remaining taxa.
The impact of waterfowl foraging on the decomposition of rice straw: mutual benefits for rice growers and waterfowl
Authors: Bird J.A. , Pettygrove G.S. , Eadie J.M. 
Published: March 2003

1. Recent legislation in California, USA, has restricted traditional open‐field burning of rice straw residues, leading farmers to adopt alternative methods of straw disposal such as post‐harvest flooding of rice fields. These changes may benefit wildlife because winter‐flooded fallow rice fields provide foraging habitat to migratory waterfowl. In turn, the foraging activity of waterfowl may help to increase rice straw decomposition, providing a reciprocal benefit to farmers. We examined the effects of waterfowl foraging activity on straw decomposition and nitrogen mineralization following rice harvest in a fallow flooded soil. 2.  Experimental plots (25 m2) were established on a silty clay soil and were subjected to two post‐harvest treatments: wet‐rolled or untilled. Mallard ducks Anas platyrhynchos were placed in one‐half of the experimental plots, following a split‐plot design, for a 3‐week period, at a density equivalent to 33 birds ha−1 over a season of 180 days to approximate regional abundance data. 3.  Waterfowl foraging activity increased residual surface straw decomposition by 78% in untilled plots and 18% in wet‐rolled plots compared with the respective unforaged plots. Average straw diameter in foraged plots was reduced to one‐third that of unforaged plots. 4.  Waterfowl foraging and field tillage reduced nitrogen (N) concentrations in the surface straw residue remaining at the end of the winter fallow period. Below‐ground organic residue was not affected by waterfowl foraging, indicating that ducks did not incorporate the straw. There were no apparent additions of carbon (C) or N to the soil as a result of waterfowl activity. 5. We conclude that waterfowl foraging can substantially increase straw decomposition in flooded, fallow, rice fields. Accordingly, rice producers should consider agronomic practices that attract waterfowl, such as winter flooding, to maximize the decomposition of rice straw residue. At the upper end of regionally observed waterfowl densities (at or near 33 birds ha−1 season−1) waterfowl foraging activity may alleviate the need for autumn tillage. Shallow flooded rice fields will also provide important winter habitat to migratory waterfowl, aiding wetland management and conservation efforts in the Central Valley of California. 6. These results provide an example of how a mutually beneficial solution can be achieved that provides needed waterbird habitat while concomitantly alleviating an agricultural problem.
Modelling the spatial dynamics of parapoxvirus disease in red and grey squirrels: a possible cause of the decline in the red squirrel in the UK?
Authors: Rushton S.P. , Lurz P.W.W. , Gurnell J. , Fuller R. 
Published: March 2003

Summary 1.  A stochastic individual‐based model for simulating the dynamics of an infectious disease in sympatric red and grey squirrel populations is described. The model simulates the spread of parapoxvirus between squirrels in fragmented populations based on the dispersal of infected animals, the probability of encounters between individuals, exposure to the virus and subsequent mortality. 2.  The disease model was integrated with a spatially explicit population dynamics model that simulated red and grey squirrel populations in real landscapes, using habitat information held in a geographical information system. Latin hypercube sampling was used to create a range of realistic life‐history and infection scenarios and the model was used to investigate the dynamics of red and grey squirrels in Norfolk between 1966 and 1980. 3.  The model predicted that parapoxvirus, like interspecific competition, could have led to the extinction of the red squirrel in Norfolk. The results suggest that the red squirrel–grey squirrel–parapoxvirus interaction represents a system of apparent competition mediated by an infectious agent, as seen in other interactions between resident and exotic species. 4.  The need for further epidemiological research on the virus is emphasized. We believe that the combined effects on disease transmission of habitat, behaviour and grey squirrels acting as reservoir hosts will lead to a patchy prevalence and sporadic incidence of parapoxvirus disease in red squirrels and a more rapid local replacement by grey squirrels. 5.  These results have implications for conservation management of the red squirrel in the UK. Schemes in which animals are translocated or given supplementary feeding may enhance disease spread by bringing infected animals into contact with others.
The effects of fragmentation on fluctuating asymmetry in passerine birds of Brazilian tropical forests
Authors: Anciães M. , Marini M.Â. 
Published: March 2003

Summary 1.  Fluctuating asymmetry (FA) refers to the difference between the right and left sides in characters that should otherwise be bilaterally symmetrical, but whose expression is affected by epigenetic stress during development. Forest fragmentation may promote an increase in FA in isolated populations, by either genetic or environmental stress. FA may function as a biomonitor index in conservation biology if increased levels were observed in populations from fragmented habitats. 2.  We tested the hypothesis that FA is higher in birds from small tropical forest patches than in large forest tracts. We measured wing and tarsus FA on mist‐netted birds from seven fragments and seven continuous areas from south‐eastern Atlantic rain forest in Brazil. We performed FA comparisons between fragments and control groups for the whole community, for individual foraging guilds and for the six most abundant species. 3.  Wing and tarsus FA were significantly greater in fragments than continuous areas for the whole community and were both negatively correlated with forest fragment size. Differences in FA varied among foraging guilds, being more evident for insectivorous species, especially those feeding in or near the understorey. 4.  FA levels increased significantly in forest fragments in at least one trait for five of the six most abundant species. There was no correlation between tarsus and wing asymmetries for the individuals of any species nor any difference between the degree of asymmetries of these characters. 5.  We suggest that FA is a useful tool to assess the effects of fragmentation on forest birds, and may be applied in monitoring neotropical birds. FA indices might be profitably developed, particularly in species most threatened by fragmentation effects and when investigated in different morphological characters.
The effect of dingo control on sheep and beef cattle in Queensland
Authors: Allen L.R. , Sparkes E.C. 
Published: March 2003

Summary

Predation by dingoes Canis lupus dingo is regarded as a widespread problem by Australian livestock producers. This study examined five decades of historical data to evaluate the use and effect of dingo control on the distribution of sheep and beef cattle in Queensland.
In Queensland, dingo bounties were significantly more numerous in years with high sheep numbers but significantly less numerous in years with high beef cattle numbers. These relationships probably reflected the social and economic attitudes of the two producer groups to dingoes.
The relatively high impact that dingoes are perceived to have on sheep compared with beef cattle, the control techniques used by the two producer groups, and the intensity at which these techniques are applied, were the underlying causes.
Subsequent to the introduction of baiting using 1080 (sodium fluoracetate), there was an immediate decline in the use of strychnine, the number of dingo bounties presented for payment, and the number of dingo trappers employed by local governments in Queensland. However, these changes were confounded by a simultaneous decline in sheep numbers and dingo control effort.
Barrier fences and poisoned ‘buffers’ were compared for their ability to protect sheep from dingo predation. With few exceptions, sheep numbers declined or increased marginally within 50 km inside a dingo barrier fence or within a boundary between sheep and beef cattle production outside the dingo barrier fence. This contrasted to areas > 50 km from the dingo barrier fence or sheep/cattle boundary.
Both poisoned buffers and barrier fences could be equally effective at preventing sheep losses. However, buffers are best suited to open arid areas where large‐scale co‐ordinated baiting programmes are more feasible and where prey scarcity leads to increased bait consumption. We predict that sheep production outside the dingo barrier fence in Queensland will contract from the north and east. There is a case for re‐establishing a barrier fence in this area to prevent such contraction.
Co‐ordinated predator management, such as barrier fencing or aerial baiting, can protect sheep at a regional level. However, unless the financial burden of pest control is shared through a centralized scheme, sheep producers living along the boundary are likely to leave the industry or substitute cattle for sheep and the sheep‐production area will contract.
This paper cautions the use of bounties as a measure of relative abundance and illustrates how people’s perception of a pest and the type of livestock they produce can affect their level of control effort and the control methods they use.
Colonization of grassland by sown species: dispersal versus microsite limitation in responses to management
Authors: Coulson Sarah J. , Bullock James M. , Stevenson Mark J. , Pywell Richard F. 
Published: March 2003

Summary

Diversification of species‐poor grassland often requires the introduction of desirable species by sowing seed. Little is known about the factors controlling the spread of introduced species, or how these interact with management. We determined whether management affected spread rates of two grassland species by modifying seed dispersal or seedling establishment.
An experiment was set up in 1995 on a species‐poor grassland. It comprised five blocks, each with four treatments: (1) autumn grazed only; (2) cut July; (3) cut July and September; (4) cut July and aftermath grazed. Twenty‐two plant species were separately slot‐seeded into each treatment plot, providing discrete linear colonization foci.
The mechanisms controlling spread were studied in two species: Rhinanthus minor, an annual with large seeds adapted for wind dispersal; and Leucanthemum vulgare, a perennial with small seeds with no obvious dispersal adaptations.
Perpendicular spread of each species by 1998 was described well by a simple inverse power model. Rhinanthus had spread further in the hay‐cut treatments (2–4) than in the grazed treatment (1). Leucanthemum spread poorly in all plots, with no treatment effects.
Seed dispersal from source slots was also described well by the inverse power model. Dispersal curves for Rhinanthus were much longer in the hay‐cut treatment (3) than in the grazed treatment (1), because more seed dispersed during hay cutting than before, and cutting dispersed seed longer distances. There was no dispersal by grazing animals. Dispersal showed directional effects: seeds travelled further in the prevailing wind direction before the hay‐cut and in the grazed treatment; dispersal by hay cutting was further in the cut direction than in the opposite direction.
Leucanthemum showed poor dispersal, with no treatment effects, except that more seeds were dispersed in the grazed (1) than the hay‐cut (3) treatment.
The establishment and survival of sown seeds showed no treatment effects for either species.
Management effects on the spread of Rhinanthus reflected effects on dispersal, rather than establishment. Leucanthemum showed poor dispersal but good establishment in all treatments, suggesting its spread may also have been dispersal‐limited. Rhinanthus was positively affected by hay cutting because it set seed at the time of cutting, whereas Leucanthemum set seed later and cutting reduced its seed production.
The results indicate that management of grassland to enhance the colonization of sown species might be best targeted at enhancing seed‐dispersal distances. Hay cutting can do this, but must coincide with seed set.
A plant trait analysis of responses to grazing in a long‐term experiment
Authors: James M. Bullock , Joe Franklin , Mark J. Stevenson , Jonathan Silvertown , Sarah J. Coulson , Steve J. Gregory , Richard Tofts 
Published: March 2003

Summary

There are few long‐term experimental studies of plant community responses to changes in grazing intensity. Here we report species’ changes in a mesotrophic grassland after 12 years of a grazing experiment and relate these changes to species’ life‐history traits.
The experiment was set up in 1986 on an extensified species‐poor grassland in lowland UK. Treatments comprised sheep grazing vs. no grazing in winter, grazing vs. no grazing in spring, and two grazing intensities in summer, in a 2 × 2 × 2 factorial design with two replicate blocks.
Point quadrat surveys in 1998 showed responses to grazing treatments by 17 of the 22 most common species. Species showed different responses, many of which were specific to a grazing season. Community changes were similar under spring and winter grazing, but the heavier summer grazing had different consequences. Species richness was increased by spring grazing, decreased by heavier summer grazing and unaffected by winter grazing.
More species responded to treatments in the 1998 survey compared with a survey in 1990. Furthermore, the whole experimental grassland had changed between the surveys, probably as a result of falling soil fertility. The two dominant grasses had declined drastically and most other species had increased in abundance. Five new species were found in 1998.
Intensive surveys of dicotyledonous species in 1998 showed five of the 12 most common species had responded to grazing treatments. In most cases dicotyledonous species had increased in abundance under heavier grazing in one or more season, and species richness was increased by spring and winter grazing. Compared with a 1991 survey, the number of species responding to treatments had increased by 1998 and seven new species were found.
We tested whether species’ responses to grazing were linked to life‐history traits according to three hypotheses: that heavier grazing would disadvantage (i) species grazed preferentially, (ii) species less able to colonize gaps or (iii) more competitive species. Mechanisms differed among seasonal treatments. Responses to heavier summer grazing were linked strongly to gap colonization ability. Responses to spring and winter grazing were positively related to grazer selectivity, a surprising result that might be explained if selectivity was positively related to plant regrowth ability.
This study shows the need for long‐term experimental analyses of community responses to grazing as vegetation responses may develop over a long time. The traits analysis suggests it may be possible to predict changes in species composition under grazing through an understanding of the mechanisms of plant responses. Grassland managers require such information in order to manipulate grazing regimes to achieve, for example, diversification or weed control.
Quality of cavity microclimate as a factor influencing selection of maternity roosts by a tree‐dwelling bat,Chalinolobus tuberculatus, in New Zealand
Authors: Sedgeley Jane A. 
Published: March 2003

SummaryCavity quality is important for the productivity and survival of many species of tree‐dwelling wildlife. Intensive land management practices, such as logging and agriculture, frequently reduce cavity availability and potentially affect the long‐term viability of populations.The New Zealand long‐tailed batChalinolobus tuberculatusselects roosts in small knot‐hole cavities with specific structural properties relative to available cavities. They also change roosts daily among a large pool of different roosts. Such behaviour is likely to makeC. tuberculatusvulnerable to human‐induced deterioration in roosting habitat.This study represents a case study of the degree of sophistication sometimes required to assess availability and quality of roost sites, by testing whether roosts selected byC. tuberculatusalso have specific microclimates.Selection for microclimate was demonstrated by comparing temperature and humidity inside unoccupied maternity roosts with available, apparently unused, knot‐hole cavities, large trunk‐hollows and ambient conditions.Compared with ambient conditions, roost and available knot‐hole cavities had stable microclimates displaying only small ranges in temperature and humidity. Temperature inside cavities was lower than ambient temperature in the day and was warmer (and peaked) at night. Humidity in cavities was constantly high. Mean temperatures within trunk‐hollows (not known to be used byC. tuberculatus) were cooler than mean ambient and roost temperatures, and temperature ranges in hollows were large and fluctuated similarly to ambient temperatures.Compared with available cavities and hollows, roost cavities had higher minimum temperatures, and maximum temperatures occurred significantly later in the day and continued for significantly longer. Humidity ranges were less and high humidity was maintained for longer.The results suggest thatC. tuberculatusselects maternity roost sites with microclimatic conditions that are likely to accrue substantial energetic benefits. Predicted energy savings for adult bats using roost cavities compared with available knot‐holes were 1·1–3·3%, and compared with hollows 3·4–7·3%. Greater energy savings would occur at night and benefit non‐volant young.In order to evaluate adequately and mitigate the full impacts of land‐use practices, there is a need for wider tests to provide direct evidence of interactions between habitat management, cavity provision and survival of cavity‐dependent wildlife.
The accuracy of GPS for wildlife telemetry and habitat mapping
Authors: Hulbert Ian A.R. , French John 
Published: March 2003

Summary

Decision support tools used for vegetation management require accurate information on the spatial array of different plant communities and a herbivore’s grazing location. We tested the accuracy and precision of locations derived using the satellite navigation global positioning system (GPS).
Before May 2000, the accuracy and precision of GPS‐derived locations were degraded by a process known as selective availability (SA); after May 2000, SA was disabled. In this study we investigated how to handle and improve the quality of data generated both when SA was enabled and when SA was disabled using relative GPS (rGPS). rGPS entails the post‐processed correction of the roving GPS module with simultaneously acquired positional errors recorded at a known stationary reference location.
With SA enabled, GPS data were obtained at a fixed known location to obtain baseline information, and from a roving module that essentially mimicked surveying techniques or the movement of a free‐ranging animal. The mean accuracy of GPS with SA enabled was 21 m for the fixed module and 25 m for the roving module. Use of rGPS and further manipulation of the data improved the mean accuracy of the data to 7 m for the fixed module and 10 m for the roving module. With SA disabled, data were similarly recorded from the fixed known location and resulted in a mean location accuracy of 5 m. The use of rGPS resulted in a significant improvement of this value to 3·6 m and precision measured by the 95% quantile was < 10 m. For mapping and wildlife tracking, such quality in terms of location accuracy and precision is unprecedented and demonstrates that rGPS may still be useful in many applications.
GPS enables the world‐wide collection of accurate and precise location information at 1‐second intervals. Furthermore, by programming the GPS receiver to overdetermine location by using information from all visible satellites, many of the limitations that arise in habitats or environments with a limited view of the sky may be overcome.
With SA now disabled, the potential use of GPS will increase. With further miniaturization, surveying of remote featureless landscapes or the tracking of crepuscular or far‐ranging animals will become more accurate and more quantifiable than ever before.