Validating accelerometry-derived proxies of energy expenditure using the doubly-labelled water method in the smallest penguin species

Acknowledgements We are grateful to Dr Catherine Hambly and Peter Thompson for technical assistance with the isotope analysis for the doubly labelled water measurements. We thank Parks Victoria (in particular, the rangers at Gabo Island and Port Campbell Offices) and Kevin Lotte for logistical support. Funding This project was funded by the Holsworth Wildlife Research Endowment – Equity Trustees Charitable Foundation and the Ecological Society of Australia and Deakin University internal funds.Peer reviewedPublisher PD

Determining energy expenditure in a large seabird using accelerometry

Funding The research was financially supported by the Holsworth Wildlife Research Endowment. Open Access funding provided by La Trobe University. Deposited in PMC for immediate release. Acknowledgements We thank the Victorian Marine Science Consortium, Sea All Dolphin Swims, and Parks Victoria for logistical support. Catherine Hambly and Peter Thomson provided technical support for the DLW isotope analysis. Aspects of the results and discussion in this paper are reproduced from the PhD thesis of L.P.A. (Angel, 2015).Peer reviewedPublisher PD

Disentangling the cause of a catastrophic population decline in a large marine mammal

Considerable uncertainties often surround the causes of long-term changes in population abundance. One striking example is the precipitous decline of southern sea lions (SSL; Otaria flavescens) at the Falkland Islands, from 80 555 pups in the mid 1930s to just 5506 pups in 1965. Despite an increase in SSL abundance over the past two decades, the population has not recovered, with the number of pups born in 2014 (minimum 4443 pups) less than 6% of the 1930s estimate. The order-of-magnitude decline is primarily attributed to commercial sealing in Argentina. Here, we test this established paradigm and alternative hypotheses by assessing (1) commercial sealing at the Falkland Islands, (2) winter migration of SSL from the Falkland Islands to Argentina, (3) whether the number of SSL in Argentina could have sustained the reported level of exploitation, and (4) environmental change. The most parsimonious hypothesis explaining the SSL population decline was environmental change. Specifically, analysis of 160 years of winter sea surface temperatures revealed marked changes, including a period of warming between 1930 and 1950 that was consistent with the period of SSL decline. Sea surface temperature changes likely influenced the distribution or availability of SSL prey and impacted its population dynamics. We suggest that historical harvesting may not always be the “smoking gun” as is often purported. Rather, our conclusions support the growing evidence for bottom-up forcing on the abundance of species at lower trophic levels (e.g., plankton and fish) and resulting impacts on higher trophic levels across a broad range of ecosystems

Departure time influences foraging associations in little penguins

Recent studies have documented that little penguins (Eudyptula minor) associate at sea, displaying synchronised diving behaviour throughout a foraging trip. However, previous observations were limited to a single foraging trip where only a small number of individuals were simultaneously tracked. Consequently, it is not known whether coordinated behaviour is consistent over time, or what factors influence it. In the present study, breeding adults were concurrently instrumented with GPS and dive behaviour data loggers for at least 2 consecutive foraging trips during guard and post-guard stage at two breeding colonies (London Bridge and Gabo Island, south-eastern Australia) of contrasting population size (approximately 100 and 30,000-40,000, respectively). At both colonies, individuals were sampled in areas of comparable nesting density and spatial area. At London Bridge, where individuals use a short (23 m) common pathway from their nests to the shoreline, > 90% (n = 42) of birds displayed foraging associations and 53-60% (n = 20) maintained temporally consistent associations with the same conspecifics. Neither intrinsic (sex, size or body condition) nor extrinsic (nest proximity) factors were found to influence foraging associations. However, individuals that departed from the colony at a similar time were more likely to associate during a foraging trip. At Gabo Island, where individuals use a longer (116 m) pathway with numerous tributaries to reach the shoreline, few individuals (< 31%; n = 13) from neighbouring nests associated at sea and only 1% (n = 1) maintained associations over subsequent trips. However, data from animal-borne video cameras indicated individuals at this colony displayed foraging associations of similar group size to those at London Bridge. This study reveals that group foraging behaviour occurs at multiple colonies and the pathways these individuals traverse with conspecifics may facilitate opportunistic group formation and resulting in foraging associations irrespective of nesting proximity and other factors

Proton capture cross section of Sr isotopes and their importance for nucleosynthesis of proton-rich nuclides

The (p,$\gamma$) cross sections of three stable Sr isotopes have been measured in the astrophysically relevant energy range. These reactions are important for the $p$-process in stellar nucleosynthesis and, in addition, the reaction cross sections in the mass region up to 100 are also of importance concerning the $rp$-process associated with explosive hydrogen and helium burning. It is speculated that this $rp$-process could be responsible for a certain amount of $p$-nuclei in this mass region. The (p,$\gamma$) cross sections of $^{84,86,87}$Sr isotopes were determined using an activation technique. The measurements were carried out at the 5 MV Van de Graaff accelerator of the ATOMKI, Debrecen. The resulting cross sections are compared with the predictions of statistical model calculations. The predictions are in good agreement with the experimental results for $^{84}$Sr(p,$\gamma$)$^{85}$Y whereas the other two reactions exhibit differences that increase with mass number. The corresponding astrophysical reaction rates have also been computed.Comment: Phys. Rev. C in pres

Accuracy of ARGOS Locations of Pinnipeds at-Sea Estimated Using Fastloc GPS

Background: ARGOS satellite telemetry is one of the most widely used methods to track the movements of free-ranging marine and terrestrial animals and is fundamental to studies of foraging ecology, migratory behavior and habitat-use. ARGOS location estimates do not include complete error estimations, and for many marine organisms, the most commonly acquired locations (Location Class 0, A, B, or Z) are provided with no declared error estimate.Methodology/Principal Findings: We compared the accuracy of ARGOS locations to those obtained using Fastloc GPS from the same electronic tags on five species of pinnipeds: 9 California sea lions (Zalophus californianus), 4 Galapagos sea lions (Zalophus wollebaeki), 6 Cape fur seals (Arctocephalus pusillus pusillus), 3 Australian fur seals (A. p. doriferus) and 5 northern elephant seals (Mirounga angustirostris). These species encompass a range of marine habitats (highly pelagic vs coastal), diving behaviors (mean dive durations 2&ndash;21 min) and range of latitudes (equator to temperate). A total of 7,318 ARGOS positions and 27,046 GPS positions were collected. Of these, 1,105 ARGOS positions were obtained within five minutes of a GPS position and were used for comparison. The 68th percentile ARGOS location errors as measured in this study were LC-30.49 km, LC-2 1.01 km, LC-1 1.20 km, LC-0 4.18 km, LC-A 6.19 km, LC-B 10.28 km. Conclusions/Significance: The ARGOS errors measured here are greater than those provided by ARGOS, but within the range of other studies. The error was non-normally distributed with each LC highly right-skewed. Locations of species that make short duration dives and spend extended periods on the surface (sea lions and fur seals) had less error than species like elephant seals that spend more time underwater and have shorter surface intervals. Supplemental data (S1) are provided allowing the creation of density distributions that can be used in a variety of filtering algorithms to improve the quality of ARGOS tracking data.<br /

Mate similarity in foraging Kerguelen shags: a combined bio-logging and stable isotope investigation

Similarity or dissimilarity between 2 individuals that have formed a pair to breed can occur in morphology, behaviour and diet. Such patterns influence partners&rsquo; cooperation when rearing their offspring, consequently influencing reproductive success. They may confer different benefits, depending on species and contexts. However, the extent to which breeding partners are more similar in morphology, behaviour, and diet is poorly documented. Furthermore, the relationship between behavioural consistency and mate choice is particularly poorly understood. To investigate these issues, Kerguelen shags Phalacrocorax verrucosus, which are monogamous with high mate fidelity across years, were studied. Partners were equipped with GPS and diving behaviour loggers. Feather and blood samples were analysed for stable isotopes (&delta;13C, a proxy of foraging habitat, and &delta;15N, a proxy of diet/trophic position). Generalized linear mixed effects models and permutation tests were used to investigate pair similarity in morphology, foraging behaviour, behavioural consistency, overlap in foraging areas, and diets/foraging habitats. Mates were found not to exhibit size-assortative mating, but were more similar in foraging behaviour. They did not show assortative or disassortative mating based on foraging behavioural consistency. Furthermore, they followed more similar bearings and overlapped more in foraging areas. In accordance with this, partners were more similar in &delta;15N. Given the lack of assortative mating by morphology, the similarity in behaviour could be due to individuals selecting mates with similar foraging abilities, linked with individual quality, and/or subsequently using information gained from their partners&rsquo; foraging strategies (e.g. local enhancement). This could help breeding pairs increase their foraging efficiency and reproductive success.<br /

Regional variability in diving physiology and behavior in a widely distributed air-breathing marine predator, the South American sea lion (Otaria byronia)

Our understanding of how air-breathing marine predators cope with environmental variability is limited by our inadequate knowledge of their ecological and physiological parameters. Because of their wide distribution along both coasts of the sub-continent, South American sea lions (Otaria byronia) provide a valuable opportunity to study the behavioral and physiological plasticity of a marine predator in different environments.We measured the oxygen stores and diving behavior of South American sea lions throughout most of its range, allowing us to demonstrate that diving ability and behavior vary across its range.We found no significant differences in mass-specific blood volumes of sea lions among field sites and a negative relationship between massspecific oxygen storage and size, which suggests that exposure to different habitats and geographical locations better explains oxygen storage capacities and diving capability in South American sea lions than body size alone. The largest animals in our study (individuals from Uruguay) were the shallowest and shortest duration divers, and had the lowest mass-specific total body oxygen stores, while the deepest and longest duration divers (individuals from southern Chile) had significantly larger mass-specific oxygen stores, despite being much smaller animals. Our study suggests that the physiology of airbreathing diving predators is not fixed, but that it can be adjusted, to a certain extent, depending on the ecological setting and or habitat. These adjustments can be thought of as a 'training effect': as the animal continues to push its physiological capacity through greater hypoxic exposure, its breath-holding capacity increases

Long-term species, sexual and individual variations in foraging strategies of fur seals revealed by stable isotopes in whiskers

Background: Individual variations in the use of the species niche are an important component of diversity in trophic interactions. A challenge in testing consistency of individual foraging strategy is the repeated collection of information on the same individuals. Methodology/Principal Findings: The foraging strategies of sympatric fur seals (Arctocephalus gazella and A. tropicalis) were examined using the stable isotope signature of serially sampled whiskers. Most whiskers exhibited synchronous delta C-13 and delta N-15 oscillations that correspond to the seal annual movements over the long term (up to 8 years). delta C-13 and delta N-15 values were spread over large ranges, with differences between species, sexes and individuals. The main segregating mechanism operates at the spatial scale. Most seals favored foraging in subantarctic waters (where the Crozet Islands are located) where they fed on myctophids. However, A. gazella dispersed in the Antarctic Zone and A. tropicalis more in the subtropics. Gender differences in annual time budget shape the seal movements. Males that do not perform any parental care exhibited large isotopic oscillations reflecting broad annual migrations, while isotopic values of females confined to a limited foraging range during lactation exhibited smaller changes. Limited inter-individual isotopic variations occurred in female seals and in male A. tropicalis. In contrast, male A. gazella showed large inter-individual variations, with some males migrating repeatedly to high-Antarctic waters where they fed on krill, thus meaning that individual specialization occurred over years. Conclusions/Significance: Whisker isotopic signature yields unique long-term information on individual behaviour that integrates the spatial, trophic and temporal dimensions of the ecological niche. The method allows depicting the entire realized niche of the species, including some of its less well-known components such as age-, sex-, individual- and migration-related changes. It highlights intrapopulation heterogeneity in foraging strategies that could have important implications for likely demographic responses to environmental variability