1,632 research outputs found

    Mismatches between conservation science and practice

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    Re-introduction of the Mallorcan midwife toad, Mallorca, Spain

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    The Mallorcan midwife toad (Alytes muletensis, Sanchíz & Alcover, 1977) or ferreret was first described in the 1970s as Baleaphryne muletensis from upper Pleistocene fossils, and was considered extinct. The discovery of live tadpoles in 1980 led to further research which confirmed the species as extant and endemic to Mallorca (Mayol & Alcover, 1981). Subfossils suggest that the species was once widespread across the island, but today it is confined to a few gorges within the Serra de Tramuntana mountains in the north-west part of the island. There are currently about 34 populations within the mountains and adjacent areas (16 original wild populations plus 18 re-introductions). These are largely isolated from each other by physiographic barriers, but there is little evidence of any inbreeding depression. Re-introduction of captive bred toads started in 1989 and it is estimated that about 25% of the wild toads stem from captive bred stock. The successful re-introduction program contributed to the downgrading of the species from ‘Critically Endangered’ to ‘Vulnerable’ in the Global Amphibian Assessment of 2004. There is little evidence that wild populations are continuing to decline, but the recent discovery of chytridiomycosis in four populations gives cause for concern

    The Contribution of Late-type/Irregulars to the Faint Galaxy Counts from HST Medium Deep Survey Images

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    We present a complete morphologically classified sample of 144 faint field galaxies from the HST Medium Deep Survey with 20.0 < I <22.0 mag. We compare the global properties of the ellipticals, early and late-type spirals, and find a non-negligible fraction (13/144) of compact blue [(V-I) < 1.0 mag] systems with r1/4r^{1/4}-profiles. We give the differential galaxy number counts for ellipticals and early-type spirals independently, and find that the data are consistent with no-evolution predictions based on conventional flat Schechter luminosity functions (LF's) and a standard cosmology. Conversely, late-type/Irregulars show a steeply rising differential number count with slope (δlogNδm)=0.64±0.1(\frac{\delta log N}{\delta m}) = 0.64\pm 0.1. No-evolution models based on the Loveday et al. (1992) and Marzke et al. (1994b) {\it local} luminosity functions under-predict the late-type/Irregular counts by 1.0 and 0.5 dex, respectively, at I = 21.75 mag. Examination of the Irregulars alone shows that 50\sim 50% appear inert and the remainder have multiple cores. If the inert galaxies represent a non-evolving late-type population, then a Loveday-like LF (α1.0\alpha\simeq -1.0) is ruled out for these types, and a LF with a steep faint-end (α1.5\alpha\simeq -1.5) is suggested. If multiple core structure indicates recent star-formation, then the observed excess of faint blue field galaxies is likely due to {\it evolutionary} processes acting on a {\it steep} field LF for late-type/Irregulars. The evolutionary mechanism is unclear, but 60% of the multiple-core Irregulars show close companions. To reconcile a Marzke-like LF with the faint redshift surveys, this evolution must be preferentially occurring in the brightest late-type galaxies with z > 0.5 at I = 21.75 mag.Comment: 29 pages, 1 catalog and 10 figures. The figures and catalog can be found at http://www.phys.unsw.edu.au/~spd/bib.htm

    Effectiveness of translocation in mitigating reptile-development conflict in the UK

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    The translocation of reptiles from development sites is a frequent but controversial intervention to resolve reptile-development conflicts. A general lack of post-translocation monitoring means that the fate of translocated reptiles is largely unknown. Here we report on the outcome of six reptile translocations carried out to mitigate the impacts of development. Through detailed post-translocation monitoring, we sought to determine whether translocated reptiles established populations within the receptor sites. To determine the effect of translocation, we investigated six sites within the UK that had received populations of translocated slow-worm Anguis fragilis, viviparous lizard Zootoca vivipara, adder Vipera berus and / or grass snake Natrix helvetica. Identification photographs were taken of all reptiles during the translocation. Following release, between one and three years of post-translocation monitoring was undertaken; during the monitoring, identification photographs were again collected to establish whether captured individuals were part of the translocated populations. Very few translocated individuals were encountered during the post-translocation monitoring. The mean number of translocated reptiles was 98 (SE 19.61). Of these, an average of 1.5 (SE 0.72) individuals or 1.6% of the population were captured during the monitoring. No recaptures of translocated reptiles were made at three (50%) of the study sites. The low recapture rates of translocated reptiles could be due to mortality, imperfect detection (including inaccurate identification of individuals) or post-translocation dispersal. There is some limited evidence to support each of the possible options, but post-translocation dispersal is considered to be the most likely explanation. The study found no confirmatory evidence that mitigation-driven translocations are compensating for the losses of populations to development

    The Top Ten List of Gravitational Lens Candidates from the HST Medium Deep Survey

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    A total of 10 good candidates for gravitational lensing have been discovered in the WFPC2 images from the HST Medium Deep Survey (MDS) and archival primary observations. These candidate lenses are unique HST discoveries, i.e. they are faint systems with sub-arcsecond separations between the lensing objects and the lensed source images. Most of them are difficult objects for ground-based spectroscopic confirmation or for measurement of the lens and source redshifts. Seven are ``strong lens'' candidates which appear to have multiple images of the source. Three are cases where the single image of the source galaxy has been significantly distorted into an arc. The first two quadruply lensed candidates were reported in Ratnatunga et al 1995 (ApJL, 453, L5) We report on the subsequent eight candidates and describe them with simple models based on the assumption of singular isothermal potentials. Residuals from the simple models for some of the candidates indicate that a more complex model for the potential will probably be required to explain the full structural detail of the observations once they are confirmed to be lenses. We also discuss the effective survey area which was searched for these candidate lens objects.Comment: 26 pages including 12 figures and 10 tables. AJ Vol. 117, No.

    The predictive validity of the Living Goods selection tools for community health workers in Kenya : cohort study

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    Background Ensuring that selection processes for Community Health Workers (CHWs) are effective is important due to the scale and scope of modern CHW programmes. However they are relatively understudied. While community involvement in selection should never be eliminated entirely, there are other complementary methods that could be used to help identify those most likely to be high-performing CHWs. This study evaluated the predictive validity of three written tests and two individual sections of a one-to-one interview used for selection into CHW posts in eight areas of Kenya. Methods A cohort study of CHWs working for Living Goods in eight local areas of Kenya was undertaken. Data on the selection scores, post-training assessment scores and subsequent on-the-job performance (number of household and pregnancy registrations, number of child assessments, proportion of on-time follow-ups and value of goods sold) were obtained for 547 CHWs. Kendall’s tau-b correlations between each selection score and performance outcome were calculated. Results None of the correlations between selection scores and outcomes reached the 0.3 threshold of an “adequate” predictor of performance. Correlations were higher for the written components of the selection process compared to the interview components, with some small negative correlations found for the latter. Conclusions If the measures of performance included in this study are considered critical, then further work to develop the CHW selection tools is required. This could include modifying the content of both tools or increasing the length of the written tests to make them more reliable, for if a test is not reliable then it cannot be valid. Other important outcomes not included in this study are retention in post and quality of care. Other CHW programme providers should consider evaluating their own selection tools in partnership with research teams
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