Karine Delord, Yves Cherel, Christophe Barbraud, Olivier Chastel, Henri Weimerskirch. (2017). High variability in migration and wintering strategies of brown skuas (Catharacta antarctica lonnbergi) in the Indian Ocean (Vol. 41).
Abstract: Movements of brown skuas (Catharacta antarctica lonnbergi) originating from two populations in the southern Indian Ocean were studied during the nonbreeding period using geolocation. A total of 33 individuals were equipped resulting in 34 annual tracks recovered from 50 deployments. Brown skuas varied extensively in their post-breeding movements, from true long range migrations to reach distant wintering zones, to short movements in the vicinity of breeding grounds. Overall, brown skuas migrated northward to overwinter in different areas in the southern hemisphere; individuals remained in the Indian Ocean, except two that overwintered in the Benguela Current (Atlantic Ocean). Wintering grounds were generally situated in productive dynamic upwelling waters or frontal systems. Brown skuas avoided the less productive area of the South Subtropical Gyre in the Central Indian Ocean. Individuals clearly differed in migratory strategies, targeting areas in a continuum from the sub-Antarctic to the tropics. Inter-individual differences were not sex-dependent. The migration dates varied between sexes with females leaving the breeding sites earlier and returning later compared to males. The duration of migration depended on wintering area and sex. Males had shorter migrations than females, regardless of the wintering area. Isotopic signatures clearly indicated that birds moulted in the wintering area and during migration. The low δ 15N values of feathers that grew in mixed subtropical-sub-Antarctic waters suggest that skuas fed on low trophic level prey in these areas. The origin and consequences of such strong inter-individual variation in migratory strategies requires further investigation.
Programme: 109
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Fay Rémi, Barbraud Christophe, Delord Karine, Weimerskirch Henri. (2017). From early life to senescence: individual heterogeneity in a long‐lived seabird (Vol. 88).
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Nathan Pacoureau, Matthieu Authier, Karine Delord, Christophe Guinet, Christophe Barbraud. (2017). Early-life density-dependence effects on growth and survival in subantarctic fur seals (Vol. 59).
Abstract: Understanding the regulation of natural populations has been a long-standing research program in ecology. Current knowledge on marine mammals and seabirds is biased toward the adult component of populations and lacking are studies investigating the juvenile component. Our goal was to estimate demographic parameters on the pre-weaning stage of a subantarctic fur seal (Arctocephalus tropicalis) population on Amsterdam Island, suspected to be regulated by density-dependence. The influence of abundance on growth parameters (length and weight) and survival was assessed over a study period spanning 16 years. We evidenced a negative trend in population growth rate when density increased. Density-dependence models were favored for pup body size and mass growth. Abundance had a clear influence on body length at high population-density, pups grew slower and were smaller at weaning than pups born in years with low population density. Abundance partly explained pup body mass variation and a weak effect was detected on pre-weaning survival. The causal mechanisms may be increased competition for food resources between breeding females, leading to a reduction of maternal input to their pups. Our results suggested that pup favored survival over growth and the development of their diving abilities in order to withstand the extreme fasting periods that are characteristic of this fur seal population. This analysis provides significant insight of density-dependent processes on early-life demographic parameters of a long lived and top-predator species, and more specifically on the pre-weaning stage with important consequences for our understanding of individual long-term fitness and population dynamics.
Programme: 109
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Patrick Samantha C., Pinaud David, Weimerskirch Henri, Morand‐Ferron Julie. (2017). Boldness predicts an individual's position along an exploration–exploitation foraging trade‐off (Vol. 86).
Abstract: Abstract Individuals do not have complete information about the environment and therefore they face a trade?off between gathering information (exploration) and gathering resources (exploitation). Studies have shown individual differences in components of this trade?off but how stable these strategies are in a population and the intrinsic drivers of these differences is not well understood. Top marine predators are expected to experience a particularly strong trade?off as many species have large foraging ranges and their prey often have a patchy distribution. This environment leads these species to exhibit pronounced exploration and exploitation phases but differences between individuals are poorly resolved. Personality differences are known to be important in foraging behaviour but also in the trade?off between exploration and exploitation. Here we test whether personality predicts an individual exploration?exploitation strategy using wide ranging wandering albatrosses (Diomedea exulans) as a model system. Using GPS tracking data from 276 wandering albatrosses, we extract foraging parameters indicative of exploration (searching) and exploitation (foraging) and show that foraging effort, time in patch and size of patch are strongly correlated, demonstrating these are indicative of an exploration?exploitation (EE) strategy. Furthermore, we show these are consistent within individuals and appear stable in the population, with no reproductive advantage. The searching and foraging behaviour of bolder birds placed them towards the exploration end of the trade?off, whereas shy birds showed greater exploitation. This result provides a mechanism through which individual foraging strategies may emerge. Age and sex affected components of the trade?off, but not the trade?off itself, suggesting these factors may drive behavioural compensation to maintain resource acquisition and this was supported by the evidence that there were no fitness consequence of any EE trait nor the trade?off itself. These results demonstrate a clear trade?off between information gathering and exploitation of prey patches, and reveals for the first time that boldness may drive these differences. This provides a mechanism through which widely reported links between personality and foraging may emerge.
Keywords: albatrosses area‐restricted search first passage time marginal value theorem personality seabirds
Programme: 109
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Jade Vacquié-Garcia, Jérôme Mallefet, Frédéric Bailleul, Baptiste Picard, Christophe Guinet. (2017). Marine Bioluminescence: Measurement by a Classical Light Sensor and Related Foraging Behaviour of a Deep Diving Predator.
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Jade Vacquié-Garcia, Christophe Guinet, Anne-Cécile Dragon, Morgane Viviant, Nory El Ksabi, Frédéric Bailleul. (2017). Predicting prey capture rates of southern elephant seals from track and dive parameters (Vol. 541).
Abstract: In the marine environment, track and dive parameter data (obtained using Argos or GPS tags and time–depth recorders) are commonly used to provide proxies for foraging behaviour of marine predators. However, their accuracy is rarely assessed. Recently, the addition of head-mounted accelerometers has allowed for detection of prey capture attempts (PCAs) at sea, allowing for more accurate estimations of foraging behaviour. Despite increased numbers of such devices being deployed, their use is still marginal compared with other tools which measure track and dive parameters. The objectives of our study were (1) to identify the most relevant combination of tracking and diving metrics in predicting the frequency of PCAs in female southern elephant seals Mirounga leonina from the Kerguelen Islands, and (2) to apply it to a broader range of individuals for which only tracking and diving data were available. The results of our models were consistent with the optimal foraging theory as well as the optimal diving theory. The model with the best predictive performance was the one that combined both tracking and diving information. However, most of the variability in the number of PCAs could be solely explained by changes in the diving behaviour of seals. Finally, we used the best predictive model on 20 individuals, which had not been fitted with accelerometers, to determine their main foraging zones. The behavioural indicators established in this study constitute a useful ecological tool for population monitoring and conservation purposes.
Keywords: Biologging Dive parameters Foraging Marine predator Prey capture events Southern elephant seals Track parameters
Programme: 109
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Weimerskirch H., Filippi D.P., Collet J., Waugh S.M., Patrick S.C. (2017). Use of radar detectors to track attendance of albatrosses at fishing vessels (Vol. 32).
Abstract: Abstract Despite international waters covering over 60% of the world's oceans, understanding of how fisheries in these regions shape ecosystem processes is surprisingly poor. Seabirds forage at fishing vessels, which has potentially deleterious effects for their population, but the extent of overlap and behavior in relation to ships is poorly known. Using novel biologging devices, which detect radar emissions and record the position of boats and seabirds, we measured the true extent of the overlap between seabirds and fishing vessels and generated estimates of the intensity of fishing and distribution of vessels in international waters. During breeding, wandering albatrosses (Diomedea exulans) from the Crozet Islands patrolled an area of over 10 million km2 at distances up to 2500 km from the colony. Up to 79.5% of loggers attached to birds detected vessels. The extent of overlap between albatrosses and fisheries has widespread implications for bycatch risk in seabirds and reveals the areas of intense fishing throughout the ocean. We suggest that seabirds equipped with radar detectors are excellent monitors of the presence of vessels in the Southern Ocean and offer a new way to monitor the presence of illegal fisheries and to better understand the impact of fisheries on seabirds.
Keywords: biologging bioregistro conservation method long‐line fisheries método de conservación pesca con sedal largo sistema de monitoreo de navíos vessel monitoring system
Programme: 109
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R. A. Phillips, R. Gales, G. B. Baker, M. C. Double, M. Favero, F. Quintana, M. L. Tasker, H. Weimerskirch, M. Uhart, A. Wolfaardt. (2016). The conservation status and priorities for albatrosses and large petrels (Vol. 201).
Abstract: Seabirds are amongst the most globally-threatened of all groups of birds, and conservation issues specific to albatrosses (Diomedeidae) and large petrels (Procellaria spp. and giant petrels Macronectes spp.) led to drafting of the multi-lateral Agreement on the Conservation of Albatrosses and Petrels (ACAP). Here we review the taxonomy, breeding and foraging distributions, population status and trends, threats and priorities for the 29 species covered by ACAP. Nineteen (66%) are listed as threatened by IUCN, and 11 (38%) are declining. Most have extensive at-sea distributions, and the greatest threat is incidental mortality (bycatch) in industrial pelagic or demersal longline, trawl or artisanal fisheries, often in both national and international waters. Mitigation measures are available that reduce bycatch in most types of fisheries, but some management bodies are yet to make these mandatory, levels of implementation and monitoring of compliance are often inadequate, and there are insufficient observer programmes collecting robust data on bycatch rates. Intentional take, pollution (including plastic ingestion), and threats at colonies affect fewer species than bycatch; however, the impacts of disease (mainly avian cholera) and of predation by introduced species, including feral cats (Felis catus), rats (Rattus spp.) and house mice (Mus musculus), are severe for some breeding populations. Although major progress has been made in recent years in reducing bycatch rates and in controlling or eradicating pests at breeding sites, unless conservation efforts are intensified, the future prospects of many species of albatrosses and large petrels will remain bleak.
Keywords: Anthropogenic impacts Conservation management Invasive species Non-target species Population trends Regional fisheries management organisations
Programme: 109
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Bernt-Erik Sæther, Vidar Grøtan, Steinar Engen, Tim Coulson, Peter R. Grant, Marcel E. Visser, Jon E. Brommer, B. Rosemary Grant, Lars Gustafsson, Ben J. Hatchwell, Kurt Jerstad, Patrik Karell, Hannu Pietiäinen, Alexandre Roulin, Ole W. Røstad, Henri Weimerskirch. (2016). Demographic routes to variability and regulation in bird populations (Vol. 7).
Abstract: There is large interspecific variation in the magnitude of population fluctuations, even among closely related species. The factors generating this variation are not well understood, primarily because of the challenges of separating the relative impact of variation in population size from fluctuations in the environment. Here, we show using demographic data from 13 bird populations that magnitudes of fluctuations in population size are mainly driven by stochastic fluctuations in the environment. Regulation towards an equilibrium population size occurs through density-dependent mortality. At small population sizes, population dynamics are primarily driven by environment-driven variation in recruitment, whereas close to the carrying capacity K, variation in population growth is more strongly influenced by density-dependent mortality of both juveniles and adults. Our results provide evidence for the hypothesis proposed by Lack that population fluctuations in birds arise from temporal variation in the difference between density-independent recruitment and density-dependent mortality during the non-breeding season.
Programme: 109
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S. Ishino, S. Hattori, J. Savarino, B. Jourdain, S. Preunkert, M. Legrand, N. Caillon, A. Barbero, K. Kuribayashi, N. Yoshida. (2017). Seasonal variations of triple oxygen isotopic compositions of atmospheric sulfate, nitrate, and ozone at Dumont d'Urville, coastal Antarctica (Vol. 17).
Abstract: Triple oxygen isotopic compositions (Δ17O = δ17O − 0.52 × δ18O) of atmospheric sulfate (SO42−) and nitrate (NO3−) in the atmosphere reflect the relative contribution of oxidation pathways involved in their formation processes, which potentially provides information to reveal missing reactions in atmospheric chemistry models. However, there remain many theoretical assumptions for the controlling factors of Δ17O(SO42−) and Δ17O(NO3−) values in those model estimations. To test one of those assumption that Δ17O values of ozone (O3) have a flat value and do not influence the seasonality of Δ17O(SO42−) and Δ17O(NO3−) values, we performed the first simultaneous measurement of Δ17O values of atmospheric sulfate, nitrate, and ozone collected at Dumont d'Urville (DDU) Station (66°40′ S, 140°01′ E) throughout 2011. Δ17O values of sulfate and nitrate exhibited seasonal variation characterized by minima in the austral summer and maxima in winter, within the ranges of 0.9–3.4 and 23.0–41.9 ‰, respectively. In contrast, Δ17O values of ozone showed no significant seasonal variation, with values of 26 ± 1 ‰ throughout the year. These contrasting seasonal trends suggest that seasonality in Δ17O(SO42−) and Δ17O(NO3−) values is not the result of changes in Δ17O(O3), but of the changes in oxidation chemistry. The trends with summer minima and winter maxima for Δ17O(SO42−) and Δ17O(NO3−) values are caused by sunlight-driven changes in the relative contribution of O3 oxidation to the oxidation by HOx, ROx, and H2O2. In addition to that general trend, by comparing Δ17O(SO42−) and Δ17O(NO3−) values to ozone mixing ratios, we found that Δ17O(SO42−) values observed in spring (September to November) were lower than in fall (March to May), while there was no significant spring and fall difference in Δ17O(NO3−) values. The relatively lower sensitivity of Δ17O(SO42−) values to the ozone mixing ratio in spring compared to fall is possibly explained by (i) the increased contribution of SO2 oxidations by OH and H2O2 caused by NOx emission from snowpack and/or (ii) SO2 oxidation by hypohalous acids (HOX = HOCl + HOBr) in the aqueous phase.
Programme: 414
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