bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimates of forest elephant abundance: projecting the relationship between precision and effort
Authors: Peter D. Walsh , White Lee J.T. , Mbina Christian , Idiata Daniel , Mihindou Yves , Maisels Fiona , Thibault Marc 
Published: March 2003

Summary A key element of African elephant conservation is monitoring how different forms of human activity influence elephant distribution and abundance. Information on human–elephant interaction is critical for guiding conservation action at all levels, from very local management interventions, through national protected area planning, to international policy initiatives such as the ban on ivory trade. However, methods for monitoring elephant numbers often produce rather poor estimate precision. Therefore, a major challenge for elephant monitoring programmes at all levels is to allocate survey effort efficiently: the greatest possible statistical power to detect the effects of particular forms of human activity must be obtained from limited survey effort.This study examined an approach to survey design based on the assumption that the precision of an abundance estimate is directly proportional to sampling effort. Field data from three sites in Central Africa were used to evaluate the potential of this approach for projecting how much effort will be necessary to survey and monitor forest elephants.Variance in elephant dung pile encounter rate was proportional to sampling effort, but variance was also influenced by mean encounter rate. The relationship between variance and mean encounter rate followed a power law more closely than the linear model suggested by many previous authors. The linear model tended to substantially underestimate the effort level required for areas with high encounter rates. A bootstrapping exercise suggested that modelling the precision–effort relationship across strata should produce more accurate projections than estimating a distinct precision–effort relationship for each stratum.Our results suggest that the survey design framework examined could substantially improve the statistical power of forest elephant monitoring programmes, although the use of a power law (rather than linear) model seems preferable. A similar approach should be appropriate for designing savanna elephant monitoring programmes and for addressing other issues, including rates of hunting and human elephant conflict. Furthermore, the parameter estimates reported in this study should be useful in designing elephant survey and monitoring programmes at other forested sites in Central Africa.
The effects of flooding lowland wet grassland on soil macroinvertebrate prey of breeding wading birds
Authors: Ausden Malcolm , Sutherland William J. , James Robert 
Published: March 2003

SummaryLowland wet grassland in western Europe is often managed for breeding wading birds, especially lapwingVanellus vanellus, redshankTringa totanus, snipeGallinago gallinagoand black‐tailed godwitLimosa limosa. Recommended conservation management often entails introducing winter flooding, and in Britain there is government funding to encourage this through the Environmentally Sensitive Area scheme.Soil macroinvertebrates are important prey for breeding wading birds on lowland wet grassland. This study quantified the response of soil macroinvertebrates to flooding, their ability to survive in flooded grassland, and changes in the abundance and physical availability of soil macroinvertebrates for feeding wading birds as flood water subsides.Unflooded grasslands contained high biomasses of soil macroinvertebrates, comprising mainly Tipulidae larvae and earthworm species that are widespread in pastures. Grasslands with a long history of winter flooding contained much lower biomasses of soil macroinvertebrates, comprising mainly a limited range of semi‐aquatic earthworm species.Introducing winter flooding to previously unflooded grassland greatly reduced soil macroinvertebrate biomass. This was mainly due to the majority of earthworms vacating the soil soon after the onset of flooding. However, when earthworms were artificially confined in flooded soils, most species were capable of surviving periods of at least 120 days continual submergence. Winter flooding also expelled large numbers of overwintering arthropods from the soil.Soil macroinvertebrates were slow to recolonize winter‐flooded grassland when it was re‐immersed in spring. Consequently, prey biomass for breeding wading birds remained low in areas that had been flooded during the preceding winter. However, winter flooding probably benefited breeding snipe by helping keep the soil soft enough for them to probe for prey. It also probably benefited breeding lapwings and redshank by helping keep the sward short and open enough for them to feed in during the latter part of their breeding season. Pools of winter flood water that remained in spring and early summer also provided a source of aquatic invertebrate prey for breeding wading birds.We suggest that the best feeding conditions for breeding snipe will be provided by keeping the upper soil soft enough for them to probe in but without reducing soil macroinvertebrate biomass by flooding it beforehand. Optimal conditions for breeding lapwings and redshank will probably be provided by creating a mosaic of unflooded grassland, winter‐flooded grassland and shallow pools.
Grassland invasions: effects of manipulations of climate and management
Authors: S.M. Buckland , K. Thompson , J.G. Hodgson , J.P. Grime 
Published: March 2003

Summary

Climate change, in combination with the impacts of land use, will give rise to new opportunities for grassland invasion. This paper reports on the repercussions of a field experiment.
Plant species, sown into experimental plots as part of a 6‐year study investigating factors limiting the success of seedling invasions, were resurveyed in 1999, 3 years after terminating experimental manipulations of climate, soil fertility and disturbance.
The most dramatic observation was the protracted expansion in populations of Brachypodium pinnatum, despite being at the northern limit of its distribution in Britain. In contrast, all other sown species, including those of both southern and widespread distribution in Britain, had become extinct, declined or remained unchanged in abundance.
Patterns of establishment were strongly deterministic. Populations of the southern grass, B. pinnatum, were highest in areas of the experimental plots unamended by fertilizer and physical disturbance, but expansion was apparently promoted by cessation of management. Among invaders of widespread distribution, two were dependent upon fertilizer addition (Arrhenatherum elatius and Dactylis glomerata), one significantly increased its cover with a combination of fertilizer and disturbance (Holcus lanatus), and one benefited from disturbance (Plantago lanceolata).
Two southern perennials, Origanum vulgare and Senecio erucifolius, both remained present in 1999 in plots that were formerly heated and subject to drought (1991–96), whereas they had become extinct in control plots.
Although the most successful invader was a rhizomatous perennial grass, an alternative strategy for survival and expansion was revealed after the severe drought in 1995: gap recolonization by annuals with a persistent seed bank.
Most notably, this study revealed the hidden potential of a native species to establish beyond its current range of distribution and, contrary to many recognized weeds, the capacity to achieve dominance in the absence of eutrophication or disturbance. This highlights the potent effects of climate change when plant traits effective for establishment coincide with the removal of current barriers to dispersal.
A model of bovine tuberculosis in the badger Melesmeles: an evaluation of control strategies
Authors: Smith G.C. , Cheeseman C.L. , Clifton‐Hadley R.S. , Wilkinson D. 
Published: March 2003

Summary

An individual‐based stochastic simulation model was used to investigate the control of bovine tuberculosis (TB) in the European badger Meles meles. Nearly all population and epidemiological parameters were derived from one study site, and the transmission of TB from badgers to cattle was included. The latter is an essential step if reactive badger control strategies are to be modelled.
The model appeared to underestimate slightly the rate of population recovery following widespread culling. This may have been due to simulating an isolated population with no immigration and no compensatory increase in fecundity. This should not affect the relative efficacy of each control strategy, but does require further investigation.
Of the historical methods of badger control, gassing and the ‘clean ring’ strategies were the most effective at reducing disease prevalence in the badger and cattle herd breakdown rates. These results agree with those of earlier models.
The proactive badger removal operation as part of the current field trial should cause a dramatic decrease in the number of cattle herd breakdowns, but also has the greatest effect on the badger population size.
The proactive use of a live test to detect TB, followed by vaccination, appears to reduce substantially cattle herd breakdowns and disease prevalence in the badger.
Three combined control strategies gave the best initial reduction in cattle herd breakdown rate and disease prevalence in the badger: (i) a proactive cull followed by reactive test and cull; (ii) a continued vaccination and proactive test and cull; and (iii) a continuous proactive test and cull.
The results of simulation models suggest that badger vaccination is a very good method of TB control. This is at odds with simple models and requires further investigation.
Dung beetles as indicators of change in the forests of northern Borneo
Authors: Davis Andrew J. , Holloway Jeremy D. , Huijbregts Hans , Krikken Jan , Kirk‐Spriggs Ashley H. , Sutton Stephen L. 
Published: March 2003

Summary We reviewed the use of dung beetles as indicators of environmental change, highlighting the influence of natural forest dynamics on species distributions in primary forest and suggesting new ways in which this can be used to understand and interpret the effects of disturbance such as logging. These ideas were applied to rainforest dung beetle communities in Sabah, Malaysia. Dung beetle samples, using baited pitfall and flight intercept traps, were examined from primary, logged and plantation forests. Cluster analysis on dung beetle assemblages from primary forest samples showed clear species associations that had a high degree of fidelity to a particular biotope or vegetation type. Beetles were grouped into riverine‐edge, riverine, interior‐primary and ‘even’ (equitable distribution between biotopes) associations. Although biotope‐specific associations were spatially separate in primary forest, these associations overlapped at forest margins (riverine forest) and in logged forest (to form ‘composite assemblages’). Species associations showed different responses to disturbance: the riverine association included many species that showed a positive response to at least some types of disturbance, whereas others were neutral or negative in response; the even association species were mostly neutral; the primary forest associations were almost entirely negative in response.The greatest faunal similarities were found between logged forest and riverine assemblages. Diversity was lower in logged compared with primary forest, and the lowest species richness and diversity were recorded in plantation forest. Small‐scale species richness in logged forest was generally higher than in individual transects from primary forest due to the presence of overlapping species ranges (composite assemblages) that were usually spatially separate in primary forest. Data suggested that increased species richness at a fine scale does not necessarily mean that species richness is greater at a larger scale, and that species mixing in derived ecosystems is dependent on the type of disturbance. Forest management should aim to minimize the mixing of the components of different biotopes, by implementing low impact (i.e. reduced‐impact logging) harvesting techniques.
The management of lowland neutral grasslands in Britain: effects of agricultural practices on birds and their food resources
Authors: Vickery J.A. , Tallowin J.R. , Feber R.E. , Asteraki E.J. , Atkinson P.W. , Fuller R.J. , Brown V.K. 
Published: March 2003

SummaryThe effects of agricultural intensification on biodiversity in arable systems of western Europe have received a great deal of attention. However, the recent transformation of grassland systems has been just as profound.In Britain, the management of grassland has changed substantially in the second half of the 20th century. A high proportion of lowland grassland is managed intensively. The major changes include a doubling in the use of inorganic nitrogen, a switch from hay to silage, and increased stocking densities, particularly of sheep. Structurally diverse and species‐rich swards have been largely replaced by relatively dense, fast‐growing and structurally uniform swards, dominated by competitive species.Most of these changes have reduced the suitability of grassland as feeding and breeding habitat for birds.The most important direct effects have been deterioration of the sward as nesting and wintering habitat, and loss of seed resources as food. Short uniform swards afford poor shelter and camouflage from predators, whereas increased mowing intensities and trampling by stock will destroy nests and young. Increased frequency of sward defoliation reduces flowering and seed set, and hence food availability for seed‐eating birds.The indirect effects of intensification of management on birds relate largely to changes in the abundance and availability of invertebrate prey. The effects of management vary with its type, timing and intensity, and with invertebrate ecology and phenology, but, in general, the abundance and diversity of invertebrates declines with reductions in sward diversity and structural complexity.Low input livestock systems are likely to be central to any future management strategies designed to maintain and restore the ecological diversity of semi‐natural lowland grasslands. Low additions of organic fertilizer benefit some invertebrate prey species, and moderate levels of grazing encourage sward heterogeneity.There is now a need to improve understanding of how grassland management affects bird population dynamics. Particularly important areas of research include: (i) the interaction between changes in food abundance, due to changes in fertilizer inputs, and food accessibility, due to changes in sward structure; (ii) the interaction between predation rates and management‐related changes in habitat; and (iii) the impact of alternative anti‐helminithic treatments for livestock on invertebrates and birds.
The use of nitrogen fertilizer on alternative grassland feeding refuges for pink‐footed geese in spring
Authors: Patterson I.J. , Fuchs R.M.E. 
Published: March 2003

Summary

Intensive agriculture often reduces biodiversity on farmed land, but the converse situation, of wildlife damaging agriculture, is also important. A striking example is agricultural damage by increasing populations of wild geese. Alternative feeding refuges, designed to reduce damage, will be most effective if the grass swards are made as attractive to geese as possible. This paper describes an explicitly experimental study in north‐east Scotland during 1990–93, which investigated the effectiveness of different rates of application of nitrogenous fertilizer on the amount of grazing by pink‐footed geese in spring, compared split‐application with single‐application of spring fertilizer, and evaluated the use of slow‐release fertilizer in winter.
The amount of goose grazing, measured from cumulative dropping density, increased with application rates of spring fertilizer, up to around 80 kg N ha−1, in parallel with a similar increase in grass production. Beyond this level there was little further increase, and cost‐effectiveness, measured as the percentage increase in dropping density per kg N ha−1 applied, was greatly reduced.
Dropping density and grass production did not differ significantly between split‐application and single‐application of spring fertilizer. Split‐application should reduce the risk of nitrogen leaching in cold wet seasons, but the cost of application would be double that of single‐application.
Overall, cumulative dropping density and grass production in late May were not significantly greater in plots treated over the winter with slow‐release fertilizer than in untreated plots. Dropping density was, however, higher in treated plots than in untreated ones during a short mild period in early spring. Slow‐release fertilizer may be of benefit in mild winters, but is more expensive than conventional nitrogenous fertilizer.
This study has shown that nitrogenous fertilizer can greatly increase goose grazing on sacrificial grassland refuges in spring and is a useful tool in reducing conflict between farmers and increasing goose populations.
Impact of climatic factors on the developmental stability of mountain birch growing in a contaminated area
Authors: Jari Valkama , Mikhail V. Kozlov 
Published: March 2003

SummaryWe examined developmental stability in mountain birchBetula pubescensssp.czerepanoviialong a strong pollution gradient in the Kola Peninsula, north‐western Russia, over a period of 8 years (1993–2000). In particular, we investigated whether climatic factors or aerial pollution could increase developmental instability, which was assessed through leaf fluctuating asymmetry (FA).Contrary to our expectations, leaf FA was not correlated with either distance from the pollution source, or with the levels of nickel and sulphur dioxide pollution in the study plots, or with shoot length or leaf size. There was, however, variation in FA between years: highest values of developmental instability were recorded during the coldest summers.There was also considerable among‐tree variation in FA within plots, suggesting that birch genets either responded differently to environmental stress or demonstrated a different degree of genetic stress. The significant interaction between study year and birch genet suggests that the detected variation was a consequence of different sensitivity of the trees to climatic fluctuations rather than of different sensitivity to pollution.Growth rate of birch correlated positively with developmental stability, i.e. faster leaf growth was associated with lower FA both at the scale of individual trees (presumably genetic differences) and at the scale of study years (environmental differences).The lack of detectable response to aerial pollution by mountain birch in this study may be an outcome of selection for pollution‐resistant genotypes, which may have occurred due to an exceptionally high emission pressure during the past decades. On the other hand, resistance to temperature variations may not have evolved because warm and cold periods appear to occur somewhat regularly in the Kola Peninsula, and therefore variation in temperature optima between genotypes is favoured by natural selection.Our results demonstrate that FA may serve as a useful measure of climatic stress in plants.
The occurrence of commensal rodents in dwellings as revealed by the 1996 English House Condition Survey
Authors: Langton S.D. , Cowan D.P. , Meyer A.N. 
Published: March 2003

Summary

The presence of commensal rodents was assessed in the 1996 English House Condition Survey (EHCS). Logistic regression techniques were used to identify the key factors that might determine the susceptibility of dwellings to infestation.
The overall percentages of dwellings that were infested, weighted to allow for the more intensive sampling used in certain categories of dwellings, were 1·83% for mice Mus domesticus, 0·23% for rats Rattus norvegicus living indoors and 1·60% for rats living outdoors. These figures excluded vacant properties, properties with some commercial use, and purpose‐built flats, as these groups showed different patterns of infestation and were therefore excluded from the logistic regressions.
The prevalence of both rats and mice was significantly greater for dwellings where pets or livestock were kept in the garden.
Dwellings classed as unfit for human habitation were more likely to be infested with mice.
Dwellings in areas of low‐density housing had a significantly higher prevalence of both rat and mouse infestation. This probably reflects the general suitability of the rural environment for commensal rodents.
Older properties had a relatively high prevalence of rats. This may be because their mature gardens provided suitable habitats for colonization. Once other confounding factors were taken into account, the age of the property did not influence the rate of infestation by mice.
Dwellings in areas with substantial problems, such as dereliction, litter, vacant properties and unkempt gardens, had a significantly higher prevalence of rats and mice.
This study reveals the value of applied ecological techniques, including logistic regression of presence–absence data, in understanding the distribution of commensal rodents in relation to dwellings, with the prospect of more effective management practices being developed as a consequence.
A new technique to measure spatial relationships within groups of free‐ranging coastal cetaceans
Authors: Denardo C. , Dougherty M. , Hastie G. , Leaper R. , Wilson B. , Thompson P.M. 
Published: March 2003

Summary

The development and calibration of a land‐based technique to measure inter‐animal spacing in free‐ranging coastal cetaceans is described here. The technique was developed to study the behaviour of killer whales Orcinus orca in Norway.
A theodolite was used to measure the surfacing location of one reference individual while simultaneous video recordings of the whole group were made. Digitized video frames were then used to estimate the locations of all individuals in the video frame relative to the reference animal.
The technique was calibrated using a line of towed buoys with known separations. Estimated inter‐buoy distances were compared with actual values to calculate errors. There was no observable bias in measurements, with a mean error of −0·014 m (n = 304, SD = 0·880). At ranges up to 2 km from the observation site, 95% of measurements were accurate to within 1·7 m.
The accuracy of the measurement system was characterized with a set of Monte Carlo simulations. Simulations were run at offshore ranges from 100 m to 2000 m, with random perturbations applied to all variables. Errors in inter‐animal distances for n = 16 whales were estimated using 10 000 simulation runs for every range value. The results from the simulations agreed with experimental findings. The results showed no bias in inter‐animal distance measurements, with an overall mean error of 0·0864 m.
The results indicate that this technique is suitable for studies on a variety of coastal cetacean populations. It provides a new tool for quantitative studies on spatial behaviour of cetaceans, and will help underpin management efforts to monitor effects of anthropogenic disturbance. With modification, the technique might also be applicable to other coastal vertebrates where inter‐organism distances are required.