Biology subjects

Barbraud, C.

Publications and source records attributed to Barbraud, C..

14 recordsLinked to original sources

bioRxiv2026

Large-scale exposure of southern seabirds to avian cholera Pasteurella multocida: scavengers as sentinels at different spatial scales

Seabird communities represent spatially structured social networks within which potential sentinels could inform us where multi-host pathogens could be present. Pasteurella multocida, the agent of avian cholera, is responsible for recurrent massive seabird mortality events on remote Amsterdam Island, Southern Indian Ocean, but little is known about its broad spatial occurrence. To explore its distribution and whether avian scavengers and predators could be used as sentinels, we screened 18 southern seabird species from 11 islands for antibodies against P. multocida (2634 plasma samples). We detected widespread but heterogeneous exposure among host populations. High seroprevalences were found in widely roaming predators and scavengers (giant petrels (Macronectes spp), and brown skua (Stercorarius antarcticus)), which could represent efficient sentinels at broad scales. Antibodies were also detected over a series of years in a non-migratory scavenger, the lesser sheathbill (Chionis minor) and an abundant penguin species, the king penguin (Aptenodytes patagonicus), suggesting that the bacterium was circulating locally at some sites. This broad scale serological screening of whole seabird host communities provides critical information to assess disease emergence risks in the context of global change.

ecology↗

bioRxiv2026

From vehicles to wildlife: transferable deep learning for trajectory generation

Realistic simulation of animal movement is fundamental to conservation, habitat modeling, and ecological scenario evaluation. Traditional approaches struggle to capture multi-scale trajectory dynamics, while generative deep learning for complete trajectory simulation remains largely unexplored in ecology due to data scarcity. We show that a diffusion model pre-trained on millions of vehicle GPS trajectories can be fine-tuned on hundreds of seabird central-place foraging trips to simultaneously generate ecologically realistic trajectories for five species and six breeding colonies. The fine-tuned model consistently outperforms four state-of-the-art baselines (GAN, VAE, HMM, iSSF) across movement metrics spanning step dynamics, spatial distribution, and behavioral temporality, with comparable or shorter computation times. Domain transfer reaches full performance in 35 minutes versus 7 hours from scratch, and conditioning on species and colony enables generalization to unseen combinations from as few as 10 trajectories. These results establish cross-domain transfer learning as a new paradigm for data-efficient generative animal movement modeling.

bioinformatics↗

bioRxiv2026

Dispersal, adaptation and persistence of H5N1 in the sub-Antarctic and Antarctica

High pathogenicity avian influenza virus (HPAIV) H5N1 reached the sub-Antarctic and Antarctica in 2023, subsequently spreading to remote locations within this region where it had devastating impacts on seal, penguin and albatross populations. The threat to marine wildlife over this broad area exemplifies the need to understand H5N1 long-distance dispersal and evolution. We obtained 104 novel viral genomic sequences from samples that we collected at South Georgia, Kerguelen, Crozet, Prince Edward, Falklands/Malvinas Islands and the Antarctic Peninsula in a region spanning 8,000 kilometers. Using recent phylogeographic modeling advances we show that H5N1 spread encompassed numerous transmission events between distant locations, accumulating mammalian-adaptive mutations in the process. Seals are the most affected species, but we reveal that the long-distance eastward virus dispersal better aligns with the long-distance movements of large petrels and albatrosses. The risk of H5N1 endemisation, dispersal to other locations and ongoing evolution are highly concerning.

microbiology↗

bioRxiv2025

Subtropical anticyclone impacts life-history traits of a marine top predator

Subtropical anticyclones are semi-permanent atmospheric high-pressure systems located in all major ocean basins and are associated with large-scale wind and weather patterns. They shape the physical environments of many species, yet their demographic impacts on wild populations remain largely unexplored. We combined population and climate analyses to investigate the demographic effects of subtropical anticyclones. Using 39 years of monitoring data on wandering albatrosses (Diomedea exulans), the "wind rider", breeding in the southern Indian Ocean, we explored the mechanisms linking subtropical anticyclone with demographic rates. We found that an intensified and poleward-shifted Indian Ocean subtropical anticyclone enhances westerly winds, improving survival and reproduction across all life stages in wandering albatrosses. These findings uncover a direct link between subtropical anticyclones and population dynamics, highlighting subtropical anticyclones as potential drivers of wind-reliant taxa responses to climate variability and change.

ecology↗

bioRxiv2025

Linking differences in personality to demography in the wandering albatross

Population dynamics are shaped by individual differences. With a good understanding of the relationships between individual differences and vital rates, population models can be improved to yield more realistic and detailed demographic projections. Personality, i.e., consistent individual differences in behaviour, is expected to shape individual differences in performance. Yet, an empirical quantification of its impact on population dynamics is currently lacking. Here, we developed and analysed a three-dimensional hyperstate population model that accounts for three sources of individual differences simultaneously in its structure: age, breeding state and boldness as a measure of personality. We parameterized our model using empirical demographic and boldness data on the wandering albatross (Diomedea exulans) population from the Crozet archipelago. We conducted sensitivity analyses to quantify the relative importance of boldness. We then simulated scenarios of increased strength of relationship between boldness and three vital rates (survival, breeding probability and breeding success) to explore conditions under which shifts in boldness distribution could be observed in the future. We showed that the sensitivity of population growth rate to changes in vital rates followed the normal distribution of boldness within the population. Indeed, population growth rate was much less sensitive to changes in the vital rates of extreme shy or bold individuals, compared to that of individuals of intermediate boldness. Overall, sensitivity of population growth rate was greater for survival than reproductive rates across all three dimensions. Our simulations showed that increasing the strength of the relationship between boldness and survival would yield the greatest shift in boldness distribution over time compared to breeding probability and breeding success. However, shifts in boldness distribution appeared constrained by the low heritability (< 0.2) value and the large variance in boldness in this population. Our study provides an important contribution to our understanding of the role of personality in shaping the population dynamics of wild species. In the face of global change, our approach offers a promising avenue to predict the potential for behavioral adaptation. More generally, our approach may help to unravel the complex interplay between individual variations in any (or many) traits and population dynamics.

ecology↗

bioRxiv2024

Fine-scale behaviour and population estimates suggest low exposure but do not exclude high sensitivity to bycatch for Endangered sooty albatrosses

Recent developments in assessing species-specific seabird bycatch risks demonstrated that fine-scale approaches are essential tools to quantify interactions with fishing vessels and understand attraction and attendance behaviours. Matching boats movements with birds tracking data specifically allows to investigate seabird-fishery interaction for cryptic species for which on-board information is critically lacking. The sooty albatross (Phoebetria fusca) overlaps with fisheries throughout its range and is known to be vulnerable to incidental bycatch. Combining GPS and behaviour data from individuals from Crozet Islands and boat locations during the incubation period, we investigated interactions of sooty albatrosses with fisheries in the southern Indian Ocean. Individuals foraged mostly in sub-tropical international waters, where they only encountered a small number of boats. The low interaction rate during this period may suggests that sooty albatrosses are not strongly attracted towards fishing vessels. However, this result should be interpreted with caution due to the low sample size and fishing effort during the study period, as these observations may conceal a higher bycatch risk during intense fishing effort and/or energetically demanding periods. The species conservation status requires further data to be collected throughout the annual cycle to provide an accurate assessment of the threat.

ecology↗

bioRxiv2023

BOTTOM-UP EFFECTS AND DENSITY DEPENDENCE DRIVE THE DYNAMIC OF AN ANTARCTIC SEABIRD PREDATOR-PREY SYSTEM

Understanding how populations respond to variability in environmental conditions and interspecific interactions is one of the biggest challenges of population ecology, particularly in the context of global change. Although several studies have investigated population responses to climate change, very few have explicitly integrated interspecific relationships when studying these responses. Here, we aim to understand the combined effects of inter- and intraspecific interactions and environmental conditions on the demographic parameters of a prey-predator system of three sympatric seabird populations breeding in Antarctica: the south polar skua (Catharacta maccormicki), and its two main preys during the breeding season, the Adelie penguin (Pygoscelis adeliae) and the emperor penguin (Aptenodytes forsteri). We built a two-species integrated population model (IPM) with 31 years of capture-recapture and count data, and provided a framework that allows estimating demographic parameters and abundance of a predator-prey system in a context where capture-recapture data are not available for one species. Our results showed that predator-prey interactions and local environmental conditions affect differently south polar skuas depending on their breeding state of the previous year. Concerning prey-predator relationships, the number of Adelie penguin breeding pairs showed a positive effect on south polar skua survival and breeding probability, and the number of emperor penguin dead chicks showed a positive effect on the breeding success of south polar skuas. In contrast, there was no evidence for an effect of the number of south polar skuas on the demography of Adelie penguins. We also found an important impact of sea ice conditions on both the dynamics of south polar skuas and Adelie penguins. Our results suggest that this prey-predator system is mostly driven by bottom-up processes and local environmental conditions.

ecology↗

bioRxiv2021

The challenges of independence: ontogeny of at-sea behaviour in a long-lived seabird

The transition to independent foraging represents an important developmental stage in the life cycle of most vertebrate animals. Juveniles differ from adults in various life history traits and tend to survive less well than adults in most long-lived animals. Several hypotheses have been proposed to explain higher mortality including that of inadequate/inferior foraging skills compared to adults, young naive individuals combining lack of experience and physical immaturity. Thus a change in behaviour, resulting in an improvement of skills acquired from growing experience, is expected to occur during a period of learning through the immaturity phase. Very few studies have investigated the ontogeny of foraging behaviour over long periods of time, particularly in long-lived pelagic seabirds, due to the difficulty of obtaining individual tracking data over several years. We investigated the foraging behaviour, through activity patterns, during the three life stages of the endangered Amsterdam albatross by using miniaturized activity loggers on naive juveniles, immatures and adults. Naive juveniles during their first month at sea after leaving their colony exhibited lower foraging effort (greater proportion of time spent sitting on water, longer and more numerous bouts on water, shorter and fewer flying bouts). Patterns of activity parameters in juveniles after independence suggested a progressive change of foraging performances during the first two months after fledging. We found sex differences in activity parameters according to time since departure from the colony and month of the year, consistent with the important sexual dimorphism in the Amsterdam albatross. Regardless of life stage considered, activity parameters exhibited temporal variability reflecting the modulation of foraging behaviour. This variability is discussed in light of both extrinsic (i.e. environmental conditions such as variability in food resources or in wind) and intrinsic (i.e. energetic demands linked to plumage renew during moult) factors.

ecology↗

bioRxiv2020

Multispecies integrated population model reveals bottom-up dynamics in a seabird predator-prey system

Assessing the effects of climate and interspecific relationships on communities is challenging because of the complex interplay between species population dynamics, their interactions, and the need to integrate information across several biological levels (individuals - populations - communities). Usually used to quantify species interactions, integrated population models (IPMs) have recently been extended to communities. These models allow fitting multispecies matrix models to data from multiple sources while simultaneously accounting for various sources of uncertainty in each data source. We used multispecies IPMs accommodating climate conditions to quantify the relative contribution of climate vs. interspecific interactions on demographic parameters, such as survival and breeding success, in the dynamics of a predator-prey system. We considered a stage-structured predator-prey system combining 22 years of capture-recapture data and population counts of two seabirds, the Brown Skua (Catharacta lonnbergi) and its main prey the Blue Petrel (Halobaena caerulea) both breeding on the Kerguelen Islands in the Southern Ocean. Our results showed that climate and predator-prey interactions drive the demography of skuas and petrels in different ways. The breeding success of skuas appeared to be largely driven by the number of petrels and to a lesser extent by intraspecific density-dependence. In contrast, there was no evidence of predation effects on the demographic parameters of petrels, which were affected by oceanographic factors (chlorophyll a and sea surface temperature anomalies). We conclude that bottom-up mechanisms are the main drivers of this skua-petrel system. We discuss the mechanisms by which climate variability and predator-prey relationships may affect the demographic parameters of these seabirds. Taking into account both species interactions and environmental covariates in the same analysis improved our understanding of species dynamics.

ecology↗

bioRxiv2019

When the going gets tough, the tough get going: effect of extreme climate on an Antarctic seabird’s life history

1Individuals differ in many ways. Most produce few offspring; a handful produce many. Some die early; others live to old age. It is tempting to attribute these differences in out-comes to differences in individual traits, and thus in the demographic rates experienced. However, there is more to individual variation than meets the eye of the biologist. Even among individuals sharing identical traits, life history outcomes will vary due to individual stochasticity, i.e., to chance. Quantifying the contributions of heterogeneity and chance is essential to understanding natural variability. Inter-individual differences vary across environmental conditions. Heterogeneity and stochasticity depend on environmental conditions. We show that favorable conditions increase the contributions of individual stochasticity, and reduce the contributions of heterogeneity, to variance in demographic outcomes in a seabird population. The opposite is true under poor conditions. This result has important consequence for understanding the ecology and evolution of life history strategies.

ecology↗

bioRxiv2019

Exploring the infection dynamics of a bacterial pathogen on a remote oceanic island reveals annual epizootics impacting an albatross population

Oceanic islands with reduced species richness provide an opportunity to investigate the emergence, maintenance and transmission of infectious diseases threatening wildlife. On Amsterdam Island, in the southern Indian Ocean, massive and recurrent mortality of the nestlings of Indian yellow-nosed albatross (Thalassarche carteri) has been attributed to avian cholera caused by Pasteurella multocida, a bacterial pathogen of likely human introduction. To understand the annual dynamics of pathogen prevalence, we measured the shedding of bacterial DNA by the albatrosses during four successive breeding seasons. The screening of 583 bird swabs by Real-Time PCR revealed an intense circulation of P. multocida during each study year, with a steady increase of infection prevalence across the breeding season. In the three years of highest pathogen prevalence, the epizootics were associated with massive die-offs of nestlings, inducing low annual fledging success (< 20%). These findings and developed PCR protocol have crucial applications for refining wildlife conservation plans aiming at controlling this disease.

ecology↗

bioRxiv2018

Sexual segregation in a highly pagophilic and sexually dimorphic marine predator

AO_SCPLOWBSTRACTC_SCPLOWSexual segregation is common in many species and has been attributed to intra-specific competition, sex-specific differences in foraging efficiency or in activity budgets and habitat choice. However, very few studies have simultaneously quantified sex-specific foraging strategies, at sea distribution, habitat use, and trophic ecology. Moreover, these studies come from low latitude areas reflecting a lack of evidence for polar species. We investigated sexual segregation in snow petrels Pagodroma nivea and combined movement, foraging trip efficiency, stable isotope and oceanographic data to test whether sexual segregation results from sex-specific habitat use. Breeding birds foraging in the Dumont dUrville sea, Antarctica, were tracked during incubation. Some similarities between males and females foraging characteristics did not support the sexual segregation hypothesis. Indeed, space-use sharing and utilization distribution, {delta}13C values and foraging trip performances (trip duration, length, speed and directions, mass gain, proportion mass gain) were similar between males and females.. However, there was support for sexual segregation in foraging characteristics linked to foraging habitats. Females foraged less than males in areas with higher sea ice concentration (SIC >70%) and had lower {delta}15N values in plasma, blood cells and feathers. Foraging efficiency (proportionate daily mass gain while foraging), was greater for females than for males, and was greater for larger females with deeper bills. Females were more efficient than males during short (<2 days) foraging trips, and for females, but not for males, mass gain, proportion mass gain and body condition at return from a foraging trip were positively correlated to SIC of the foraging areas. Together, these results suggest an absence of sexual segregation at large spatial scales in snow petrels during incubation, but strongly support habitat segregation between high (>70%) more profitable SIC (males) and low SIC areas (females), probably driven by intraspecific competition. Therefore, male and female snow petrels segregate at small spatial scales mainly determined by habitat (SIC) characteristics.

ecology↗

bioRxiv2018

Dispersal-dependent juvenile survival in a sexually dimorphic long-lived bird, the Greater Flamingo Phoenicopterus roseus

The viability and dynamics of spatially structured populations depend critically upon dispersal behaviour. Yet, in long lived species with delayed maturity, the fitness consequences of post-fledging dispersal, dispersal from the birthplace after independence and before first breeding attempt, are poorly understood although it is a critical determinant of natal dispersal.\n\nWe aimed at estimating sex-specific variations of juvenile survival in a long-lived bird species with sexual size dimorphism, the greater flamingo, as a function of post fledging dispersal destination. Using capture-recapture models, we estimated the survivorship of flamingos ringed in the Camargue (south of France) and wintering in the Mediterranean.\n\nDispersal probability from France was > 0.66 with important annual variations in preferred dispersal destinations. First-year survival increased along the winter temperature gradient with estimates below 0.50 {+/-} 0.07 in France and above 0.60 {+/-} 0.07 in African wetlands. The survival of flamingos wintering in France dropped by 30-50 % depending on sex between fall and spring of their first year.\n\nIn African sites and in Italy, there was no detectable difference of survival between sexes suggesting favorable wintering conditions. Body condition at fledging did not explain variations in first-fall survival within genders. Males wintering in France had a better survival than females.\n\nThese results show that sex and post-fledging dispersal destination affect juvenile survival, support the energetic hypothesis predicting an advantage of large body size to cope with cold temperatures and the competition hypothesis, and suggest the existence of sex-specific post fledging dispersal tactics.

ecology↗

bioRxiv2016

Dealing with many correlated covariates in capture-recapture models

Capture-recapture models for estimating demographic parameters allow covariates to be incorporated to better understand population dynamics. However, high-dimensionality and multicollinearity can hamper estimation and inference. Principal component analysis is incorporated within capture-recapture models and used to reduce the number of predictors into uncorrelated synthetic new variables. Principal components are selected by sequentially assessing their statistical significance. We provide an example on seabird survival to illustrate our approach. Our method requires standard statistical tools, which permits an efficient and easy implementation using standard software.

ecology↗