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Behaviour identification and time–activity budget estimation of threatened little bustard using accelerometry
No full textInternational audienceUnderstanding animal ecology requires knowing what animals do. GPS devices provide detailed insights into space use, but they lack behavioural information until recent advancements in accelerometry have bridged this gap. In this study, machine learning methods were applied to accelerometry data to identify and classify behaviours in little bustard, Tetrax tetrax, a species whose population is declining because of habitat loss and degradation. Using recordings of four captive individuals, models were fitted to classify key behaviours, standing, lying, vigilance, locomotion, foraging and male courtship, with separate models for each sex because of behavioural differences. In addition, different sampling frequencies, balancing methods and data-splitting approaches were tested to examine interindividual variation and the effect of sample size. Results revealed that models built with data sampled at 10 Hz performed similarly to those sampled at 20 Hz. Male models slightly outperformed female models, achieving precision and sensitivity exceeding 0.87. Male-specific behaviours, such as courtship, attained F1-scores above 0.8. The application of the models to 10 free-ranging individuals showed marked seasonal and sexual differences in time-activity budgets. Males changed their behaviour seasonally, devoting more time to vigilance, locomotion and courtship during the breeding season and to foraging in winter. On the contrary, females showed a more consistent behaviour pattern year-round, predominantly resting, although lying increased during the breeding season, likely reflecting incubation. These findings indicate the potential application of machine learning and accelerometry to monitor behaviours in freeranging little bustards, offering a valuable tool to understand activity patterns and develop conservation strategies for this threatened species
Video evidence of pteropod predation highlights diet flexibility in Adélie penguins
No full textInternational audienceUnderstanding how climate-driven changes in the Southern Ocean may alter predator–prey interactions is essential, for evaluating ecosystem-level consequences, yet many trophic relationships remain poorly documented. Shelled pteropods (Thecosomata) are key components of Southern Ocean zooplankton but are highly vulnerable to ocean acidification, and their role as prey for higher predators has rarely been confirmed. Here, we present the first direct video evidence of pteropod predation by chick-rearing Adélie penguins (Pygoscelis adeliae) near Dumont d’Urville Station, East Antarctica. Seven of eight video-instrumented birds consumed pteropods (N = 1,449 captures), predominantly Clio pyramidata, with two individuals relying heavily on them (> 60% of prey). Other prey included krill, fish, and occasionally amphipods. Pteropods were encountered over a wide range of distances from the colony (0.8–47 km), whereas encounters with krill and fish occurred mainly far from the colony (24–50 km and 20–52 km, respectively). Pteropod encounters occurred over a broad depth range (1–82 m), with C. pyramidata most frequently captured at 35–45 m. Although average feeding rates in pteropod-dominated dives were lower than those in krill-dominated dives (6.4 ± 1.4 captures min⁻1 and 9.5 ± 8.3 captures min⁻1, respectively), the maximum number of pteropod captures in a dive was high (81 captures), indicating substantial number of prey captures when dense pteropod patches were encountered. Our findings reveal that pteropods can serve as an opportunistic yet substantial prey for Adélie penguins, highlighting an overlooked but potentially significant trophic pathway
Hysteresis phenomenon within unsaturated granular assemblies: Capillary forces and matric suction
No full textInternational audienceIn this paper, we present a numerical approach to simulate the condensation and evaporation processes of capillary bridges within granular materials. The formation and dynamics of capillary bridges are captured using the phase-field-based Lattice Boltzmann model (LBM) to solve Allen-Cahn and Navier-Stokes equations, while evaporation and condensation processes accounted by local changes in position of the capillary interfaces. Our model captures the emergence of hysteresis as a result of irreversible geometric transitions-such as bridge coalescence and snap-off-without prescribing any constitutive relation between suction and saturation degrees. This change in capillary regimes arises naturally from the interface dynamics and not solved by the LBM. In particular, we can capture and analyze the discontinuities in capillary forces, when capillary bridges merge or split within small elementary assemblies of three or four spherical particles. Having validated our numerical results for the above elementary assemblies, a poly-dispersed granular assembly composed of 1,000 spherical grains is next addressed. Our simulations capture well-known condensation and evaporation hysteresis phenomenon while offering the possibility to inspect the underlying topology of air/water cluster for the same water saturation along different hydraulic paths
Anomalous ion transport in saline solutions under electric fields: A molecular dynamic study
No full textInternational audienceIn this study, we employ molecular dynamics simulations to investigate the anomalous diffusion of N a + and Cl -ions in water at the microscopic scale. By carefully distinguishing the migration (drift) component from the diffusive motion, we analyze the influence of ion concentration and applied electric fields on ionic transport. Our results reveal clear deviations from classical Brownian dynamics under non-zero electric fields, highlighting the emergence of anomalous diffusion regimes. We further show that the degree of anomalous behavior strongly depends on the ionic chemical activity and the strength of Coulombic interactions between ions
Toxicity by contact of Bordeaux mixture but no behavioral responses of the egg parasitoid Trichogramma cordubensis
No full textInternational audienceThe increasing use of pesticides is recognized as a threat to pest natural enemies. We investigated the effects of Bordeaux mixture, a fungicide widely used in viticulture, on Trichogramma cordubensis, a biological control agent used against the major vineyard pest Lobesia botrana. The lethal and sublethal effects of 20 g.L -1 Bordeaux mixture on T. cordubensis were studied. To assess the potential persistence of Bordeaux mixture, each experiment was conducted at four different time scales after pesticide application. A first experiment aimed to assess the effects of surface contaminations to Bordeaux mixture on the longevity of T. cordubensis, which was reduced by 26 % when exposed to the fungicide. A second experiment aimed to assess the oviposition dynamics of T. cordubensis during the three first days after its emergence in contaminated or unexposed environments. No differences in oviposition were observed when T. cordubensis was exposed to Bordeaux mixture. A third experiment aimed to assess the oviposition choices of T. cordubensis between hosts on either contaminated or unexposed surfaces. No evidence of an oviposition deterrence was detected. Overall, surface contact with Bordeaux mixture was found harmless on T. cordubensis life parameters. Time after fungicide applications did not differently impact our results on longevity and behavior. However, time after both control and pesticide applications may have led to altered micro-environmental conditions affecting T. cordubensis' development. This study suggests that T. cordubensis inability to discriminate against a copper contaminated environment is a crucial factor in enhancing its effectiveness as a biological control agent
La gestión del agua y las técnicas constructivas en el territorio de Baelo Claudia durante la Antigüedad. Memoria final del Proyecto General de Investigación, Sevilla,
No full textDrought‐driven foraging adjustments in breeding white storks Ciconia ciconia : GPS tracking insights from two French marshes
No full textInternational audienceIn the context of climate change, the increasing frequency of severe meteorological events, such as floods or droughts, is expected to impact various life history traits in organisms, primarily by altering the availability and quality of their trophic resources. Our study aimed to quantify the effects of meteorological conditions on the fine‐scale space use of breeding white storks Ciconia ciconia . Birds were equipped with GPS/acceleration loggers in two breeding areas within the marshes of the French Atlantic coast and monitored over four years, including one year of drought. Specifically, we examined variations in home‐range size, daily foraging distances, the proportion of time spent foraging, and daily activity levels in relation to drought conditions and individual state (sex, brood age and brood size). Our findings reveal that under drier conditions, storks increased their daily foraging distances, home‐range size, and time spent foraging. Individuals with smaller broods travelled greater distances from the nest, and tended to exploit larger home‐ranges. Their activity levels and time spent foraging increased with brood age and brood size, and were higher in females than in males. Our findings reveal how climate change, particularly drought, affects the foraging behaviour of a wetland top predator, and highlight the conservation challenges faced by wetland ecosystems
法国早期汉学形成过程中传教士与法国学者的贡献
No full textInternational audienceDans l’Europe des XVIIe et XVIIIe siècles, le mythe biblique de la Tour de Babel était toujours très vivant. On s’interrogeait sur ce que pouvait être cette langue originelle de l’Humanité, perdue depuis des millénaires du fait du châtiment divin. Lorsque, dans les dernières années du XVIIe siècle, décidée par Louis XIV et Colbert, la mission des Jésuites, promus à cette occasion « Mathématiciens du Roi », permit à l’Europe, en particulier à la France, de découvrir la Chine et, bien sûr, sa langue plurimillénaire, reposant sur un système d’écriture ressemblant à des hiéroglyphes et donc rappelant l’Égypte ancienne, le débat entre savants, théologiens et philosophes, prit un nouvel essor
Genetic divergence between French Atlantic populations of the red alga Gelidium pulchellum: evidence of a cryptic species complex and an undescribed distinct species
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Uncovering genetic population structure in the Endangered northern rockhopper penguin (Eudyptes moseleyi) across islands in the Southern Atlantic and Indian oceans
No full textInternational audienceBackground: The northern rockhopper penguin (Eudyptes moseleyi) is a threatened species, listed as Endangered globally by the IUCN owing to rapid population decreases in the past, combined with a limited distributional range. Their breeding is confined to five islands in the central South Atlantic Ocean (Gough, Nightingale, Inaccessible, Alex (= Middle), and Tristan da Cunha) and two islands in the southern Indian Ocean (Amsterdam and Saint Paul). Nonbreeding birds forage widely in these oceans and vagrant individuals have been recorded in the Falkland Islands/ Malvinas, South Africa, Kerguelen Archipelago, Australia, and New Zealand. The origins of these vagrant birds are largely unknown, and it remains unclear to what extent northern rockhopper penguins move between islands and oceans. Understanding connectivity between populations is essential for developing appropriate conservation strategies, especially as some populations may be at greater extinction risk than others.Results: Northern rockhopper penguins from the two oceanic basins are genetically distinct, with minimal evidence of migration between ocean basins. No substructure was detected within ocean island groups and although low, the level of migration between islands was sufficient to prevent genetic differentiation. Differential signatures of genetic diversity and inbreeding may also suggest some island populations are at higher risk of inbreeding depression. Conclusions: This study provides the first comprehensive genetic population structure analysis of the entire breeding range of the Endangered northern rockhopper penguin. This gives an unparalleled understanding of the connectivity within and between populations breeding in the Atlantic and Indian oceans, and highlights areas for further investigation. Knowledge of genetic structure and population dynamics can inform effective conservation management by predicting a species’ ability to adapt and remain resilient to local or global threats, including the increasing impacts of climate-driven changes in marine environments. Our results suggest that northern rockhopper penguins should be managed as two conservation management units to maximise the conservation of genetic diversity within the species and allow strategies to be developed that consider the different pressures affecting the populations in each ocean basin