Current Knowledge and Conservation of the Wild Mammals of the Gulf of Guinea Oceanic Islands

Oceanic islands are usually difficult for mammals to colonize; consequently, the native mammal fauna is typically species-poor, often consisting of just a few species of bats. The oceanic islands of the Gulf of Guinea are no exception to this pattern. Still, the known mammal richness is relatively high for the small size of the islands. Out of a total of 13 native species, including 11 bats and 2 shrews, at least 7 species and 3 subspecies are single-island endemics. In addition to native species, at least 6 other wild mammals have been introduced to the islands purposely or accidentally by humans. Some of these are among the world’s most notorious invasive species and cause damage to native species, ecosystems, and humans. Predation by exotic species can threaten native island mammals, which are especially sensitive due to their small populations and limited ranges. These impacts are likely worsened by other threats, such as forest degradation and climate change, and a general lack of knowledge about the natural history of most species also hampers the implementation of conservation measures. Therefore, fostering further research on the endemic-rich mammal fauna of these islands is vital to ensure their persistence.info:eu-repo/semantics/publishedVersio

Echolocation of Central Amazonian ‘whispering’ phyllostomid bats: call design and interspecific variation

Phyllostomids (New World leaf-nosed bats) are the ecologically most diverse bat family and have undergone the most extensive adaptive radiation of any mammalian family. However comprehensive, multi-species studies regarding phyllostomid echolocation are scarce in the literature despite abundant ecological research. In this study, we describe the call structure and interspecific variation in call design of 40 sympatric phyllostomid species from the Central Brazilian Amazon, focussing on general patterns within genera, subfamilies and between feeding guilds. All but one species utilized short, broadband FM calls consisting of multiple harmonics. As reported for other bat families, peak frequency was negatively correlated with body mass and forearm length. Twenty-five species alternated the harmonic of maximum energy, principally between the second and third harmonic. Based on PCA, we were unable to detect any significant differences in echolocation call parameters between genera, subfamilies or different feeding guilds, confirming that acoustic surveys cannot be used to reliably monitor these species. We present Ametrida centurio as an exception to this generalized phyllostomid structure, as it is unique in producing a mono-harmonic call. Finally, we discuss several hypotheses regarding the evolutionary pressures influencing phyllostomid call structure

Hidden-variable theorems for real experiments

It has recently been questioned whether the Kochen-Specker theorem is relevant to real experiments, which by necessity only have finite precision. We give an affirmative answer to this question by showing how to derive hidden-variable theorems that apply to real experiments, so that non-contextual hidden variables can indeed be experimentally disproved. The essential point is that for the derivation of hidden-variable theorems one does not have to know which observables are really measured by the apparatus. Predictions can be derived for observables that are defined in an entirely operational way.Comment: 4 page

Nature-based solutions to increase rice yield: An experimental assessment of the role of birds and bats as agricultural pest suppressors in West Africa

Rice is widely consumed as a staple food, being cultivated worldwide. However, in West Africa, production is not enough to satisfy demand. Rice often suffers intensive damage by herbivorous arthropods that affect quality and quantity of the grain. Birds and bats have been shown to suppress arthropod pests, potentially enhancing rice productivity and food security. However, the degree to which these taxa provide nature-based solutions for mitigating pest-induced rice losses is poorly known, especially in West Africa. Here, we used experimental exclosures to investigate whether birds and bats reduce plant damage and boost rice yield by suppressing arthropod abundance. In a rural area in northern Guinea-Bissau, we established 14 sets of paired control and experimental exclosures parcels, precluding access of birds and bats to rice plants. We then quantified how the absence of birds and bats influenced arthropod communities, plant damage, and rice yield over a full rice production cycle (six months). Arthropod numbers in exclosures (10.1 ± 9.1 ind./plot) were nearly double those in control plots (5.8 ± 3.0 ind./plot), a result mostly due to a lower spider abundance in the controls. The percentage of leaf and grain damage showed no difference between exclosure and control. Using Structural Equation Models, we uncovered that the exclusion of birds and bats boosted arthropod abundance but had only marginal effects on rice damage and no detectable effect on yield. The exclusion of flying vertebrates led to a marked increase in spider abundance, suggesting an effect of mesopredator release, which in turn likely helped maintaining pest abundance low and potentially contributing to the small overall effect on rice damage and yield. Enhancing the abundance of birds and bats is an interesting option to suppress agricultural pests, but our results highlight the need for a better understanding of ecological interactions in agricultural landscapes in West Africa. We stress the need for more research to inform evidence-based policies using nature-based solutions that foster the natural consumption of pests by vertebrates, as a means to improve food security

Secondary forest regeneration benefits old-growth specialist bats in a fragmented tropical landscape

Tropical forest loss and fragmentation are due to increase in coming decades. Understanding how matrix dynamics, especially secondary forest regrowth, can lessen fragmentation impacts is key to understanding species persistence in modified landscapes. Here, we use a whole-ecosystem fragmentation experiment to investigate how bat assemblages are influenced by the regeneration of the secondary forest matrix. We surveyed bats in continuous forest, forest fragments and secondary forest matrix habitats, similar to 15 and similar to 30 years after forest clearance, to investigate temporal changes in the occupancy and abundance of old-growth specialist and habitat generalist species. The regeneration of the second growth matrix had overall positive effects on the occupancy and abundance of specialists across all sampled habitats. Conversely, effects on generalist species were negligible for forest fragments and negative for secondary forest. Our results show that the conservation potential of secondary forests for reverting faunal declines in fragmented tropical landscapes increases with secondary forest age and that old-growth specialists, which are often of most conservation concern, are the greatest beneficiaries of secondary forest maturation. Our findings emphasize that the transposition of patterns of biodiversity persistence in island ecosystems to fragmented terrestrial settings can be hampered by the dynamic nature of human-dominated landscapes.Peer reviewe

Secondary forest buffers the effects of fragmentation on aerial insectivorous bat species following 30 years of passive forest restoration

Passive forest restoration can buffer the effects of habitat loss on biodiversity. We acoustically surveyed aerial insectivorous bats in a whole‐ecosystem fragmentation experiment in the Brazilian Amazon over a 2‐year period, across 33 sites, comprising continuous old‐growth forest, remnant fragments, and regenerating secondary forest matrix. We analyzed the activity of 10 species/sonotypes to investigate occupancy across habitat types and responses to fragment size and interior‐edge‐matrix (IEM) disturbance gradients. Employing a multiscale approach, we investigated guild (edge foragers, forest specialists, flexible forest foragers, and open space specialists) and species‐level responses to vegetation structure and forest cover, edge, and patch density across six spatial scales (0.5–3 km). We found species‐specific habitat occupancy patterns and nuanced responses to fragment size and the IEM disturbance gradient. For example, Furipterus horrens had lower activity in secondary forest sites and the interior and edge of the smallest fragments (1 and 10 ha) compared to continuous forest, and only two species (Pteronotus spp.) showed no habitat preference and no significant responses across the IEM and fragment size gradients. Only the Molossus sonotype responded negatively to vegetation structure. We uncovered no negative influence of forest cover or edge density at guild or species‐level. Our results indicate that reforestation can buffer the negative effects of fragmentation and although these effects can still be detected in some species, generally aerial insectivorous bats appear to be in recovery after 30 years of passive forest restoration. Our findings reinforce the need to protect regenerating forests while conserving vast expanses of old‐growth forest

Effect of the natural sweetener xylitol on gut hormone secretion and gastric emptying in humans:A pilot dose-ranging study

Sugar consumption is associated with a whole range of negative health effects and should be reduced and the natural sweetener xylitol might be helpful in achieving this goal. The present study was conducted as a randomized, placebo-controlled, double-blind, cross-over trial. Twelve healthy, lean volunteers received intragastric solutions with 7, 17 or 35 g xylitol or tap water on four separate days. We examined effects on: gut hormones, glucose, insulin, glucagon, uric acid, lipid profile, as well as gastric emptying rates, appetite-related sensations and gastrointestinal symptoms. We found: (i) a dose-dependent stimulation of cholecystokinin (CCK), active glucagon-like peptide-1 (aGLP-1), peptide tyrosine tyrosine (PYY)-release, and decelerated gastric emptying rates, (ii) a dose-dependent increase in blood glucose and insulin, (iii) no effect on motilin, glucagon, or glucose-dependent insulinotropic peptide (GIP)-release, (iv) no effect on blood lipids, but a rise in uric acid, and (v) increased bowel sounds as only side effects. In conclusion, low doses of xylitol stimulate the secretion of gut hormones and induce a deceleration in gastric emptying rates. There is no effect on blood lipids and only little effect on plasma glucose and insulin. This combination of properties (low-glycemic sweetener which stimulates satiation hormone release) makes xylitol an attractive candidate for sugar replacement

Multi-Jet Event Rates in Deep Inelastic Scattering and Determination of the Strong Coupling Constant

Jet event rates in deep inelastic ep scattering at HERA are investigated applying the modified JADE jet algorithm. The analysis uses data taken with the H1 detector in 1994 and 1995. The data are corrected for detector and hadronization effects and then compared with perturbative QCD predictions using next-to-leading order calculations. The strong coupling constant alpha_S(M_Z^2) is determined evaluating the jet event rates. Values of alpha_S(Q^2) are extracted in four different bins of the negative squared momentum transfer~\qq in the range from 40 GeV2 to 4000 GeV2. A combined fit of the renormalization group equation to these several alpha_S(Q^2) values results in alpha_S(M_Z^2) = 0.117+-0.003(stat)+0.009-0.013(syst)+0.006(jet algorithm).Comment: 17 pages, 4 figures, 3 tables, this version to appear in Eur. Phys. J.; it replaces first posted hep-ex/9807019 which had incorrect figure 4

Multiplicity Structure of the Hadronic Final State in Diffractive Deep-Inelastic Scattering at HERA

The multiplicity structure of the hadronic system X produced in deep-inelastic processes at HERA of the type ep -> eXY, where Y is a hadronic system with mass M_Y< 1.6 GeV and where the squared momentum transfer at the pY vertex, t, is limited to |t|<1 GeV^2, is studied as a function of the invariant mass M_X of the system X. Results are presented on multiplicity distributions and multiplicity moments, rapidity spectra and forward-backward correlations in the centre-of-mass system of X. The data are compared to results in e+e- annihilation, fixed-target lepton-nucleon collisions, hadro-produced diffractive final states and to non-diffractive hadron-hadron collisions. The comparison suggests a production mechanism of virtual photon dissociation which involves a mixture of partonic states and a significant gluon content. The data are well described by a model, based on a QCD-Regge analysis of the diffractive structure function, which assumes a large hard gluonic component of the colourless exchange at low Q^2. A model with soft colour interactions is also successful.Comment: 22 pages, 4 figures, submitted to Eur. Phys. J., error in first submission - omitted bibliograph

Measurements of Transverse Energy Flow in Deep-Inelastic Scattering at HERA

Measurements of transverse energy flow are presented for neutral current deep-inelastic scattering events produced in positron-proton collisions at HERA. The kinematic range covers squared momentum transfers Q^2 from 3.2 to 2,200 GeV^2, the Bjorken scaling variable x from 8.10^{-5} to 0.11 and the hadronic mass W from 66 to 233 GeV. The transverse energy flow is measured in the hadronic centre of mass frame and is studied as a function of Q^2, x, W and pseudorapidity. A comparison is made with QCD based models. The behaviour of the mean transverse energy in the central pseudorapidity region and an interval corresponding to the photon fragmentation region are analysed as a function of Q^2 and W.Comment: 26 pages, 8 figures, submitted to Eur. Phys.