Loading...
7 results
Search Results
Now showing 1 - 7 of 7
- Migrants and residents of a long‐lived seabird differ in their behavioural response to a stressorPublication . Gatt, Marie C.; Granadeiro, José Pedro; Catry, PauloInter-individual variation in behaviour has been recognised as a major driver of population ecology, but its relationship to migratory strategy has been ill-explored. Here, we investigated whether male migrant and resident Cory’s shearwaters Calonectris borealis, a long-lived partially migratory seabird, are distinguishable by their temperament at the colony. We tracked a large number of individuals over two winters using GLS devices and assessed whether exploratory behaviour and reaction to extraction from the nest corresponded to migratory strategy over this period. While exploratory behaviour was unrelated to migratory strategy, birds that were resident were more likely to be unreactive towards extraction from the nest. This difference in behavioural stress response, together with previous findings that migrants display higher physiological stress over winter, suggests that migrants and residents may be distinguishable by their stress threshold.
- Higher mercury contamination is associated with shorter telomeres in a long-lived seabird – A direct effect or a consequence of among-individual variation in phenotypic quality?Publication . Bauch, Christina; Gatt, Marie C.; Verhulst, Simon; Granadeiro, José P.; Catry, PauloMercury is a heavy metal, which is pervasive and persistent in the marine environment. It bioaccumulates within organisms and biomagnifies in the marine food chain. Due to its high toxicity, mercury contamination is a major concern for wildlife and human health. Telomere length is a biomarker of aging and health, because it predicts survival, making it a potential tool to investigate sublethal effects of mercury contamination. However, the relationship between telomeres and mercury contamination is unclear. We measured feather mercury concentration in Cory's Shearwaters Calonectris borealis, long-lived seabirds and top predators, between 9 and 35 years of age and related it to telomere length in erythrocytes. Cory's Shearwaters with higher mercury concentrations had shorter telomeres and the effect was sex-dependent, reaching significance in males only. This may be explained by the fact that males have longer telomeres and higher and more variable mercury concentrations than females in this population. The mercury effect on telomere length was stronger on longer telomeres in the genome within individuals. We discuss the hypotheses that the negative correlation could either be a direct effect of mercury on telomere shortening and/or a consequence of variation in phenotypic quality among individuals that results in a covariation between mercury contamination and telomere length.
- Generalist seabirds as biomonitors of ocean mercury: The importance of accurate trophic position assignmentPublication . Gatt, Marie Claire; Reis, Bianca; Granadeiro, José Pedro; Pereira, Eduarda; Catry, PauloMonitoring mercury concentration in the marine environment is pivotal due to the risks that mercury intake poses to the ecosystem and human health. It is therefore of interest to make reliable, comparative measurements over large geographic areas. Here, the utility of wide-ranging generalist seabirds as mercury biomonitors at an ocean basin scale was assessed, using the Cory's Shearwater as a model species. The mercury concentration in flight feathers moulted at distant non-breeding areas of geolocator-tracked birds was quantified, reflecting contamination in various geographic areas. Compound-specific isotope analysis of amino acids was used to obtain comparable trophic positionestimates controlled for baseline isoscape. Birds that remained resident in the Canary Current integrated less mercury into their feathers than those that migrated to either the Benguela or Agulhas currents. Residents also occupied a significantly lower trophic position during the non-breeding season than migrants, largely explaining the difference in mercury exposure. Both mercury concentration and trophic position were similar in individuals spending the non-breeding period in the Benguela and Agulhas currents. This paper highlights the importance of accurate trophic position calculation in order to understand mercury exposure in wide-ranging predators and for meaningful spatial comparisons.
- Untangling causes of variation in mercury concentration between flight feathersPublication . Gatt, Marie C.; Furtado, Ricardo Andrade; Granadeiro, José P.; Lopes, Daniel; Pereira, Eduarda; Catry, PauloBird feathers are one of the most widely used animal tissue in mercury biomonitoring, owing to the ease of collection and storage. They are also the principal excretory pathway of mercury in birds. However, limitations in our understanding of the physiology of mercury deposition in feathers has placed doubt on the interpretation of feather mercury concentratoins. Throughout the literature, moult sequence and the depletion of the body mercury pool have been taken to explain patterns such as the decrease in feather mercury from the innermost (P1) to the outermost primary feather (P10) of the wing. However, it has been suggested that this pattern is rather a measurement artefact as a result of the increased feather mass to length ratio along the primaries, resulting in a dilution effect in heavier feathers. Here, we attempt to untangle the causes of variation in feather mercury concentrations by quantifying the mercury concentration as μg of mercury (i) per gram of feather, (ii) per millimetre of feather, and (iii) per day of feather growth in the primary feathers of Bulwer's Petrel Bulweria bulwerii chicks, effectively controlling for some of the axes of variation that may be acting in adults, and monitoring the growth rate of primary feathers in chicks. The mercury concentration in Bulwer's Petrel chicks' primaries increased from the innermost to the outermost primary for all three concentration measures, following the order of feather emergence. These observations confirm that the pattern of mercury concentration across primary feathers is not an artefact of the measure of concentration, but is likely an effect of the order of feather growth, whereby the earlier grown feathers are exposed to higher blood mercury concentrations than are later moulted feathers as a result of blood mercury depletion.
- Monitoring of mercury in the mesopelagic domain of the Pacific and Atlantic oceans using body feathers of Bulwer's petrel as a bioindicatorPublication . Furtado, Ricardo; Granadeiro, José Pedro; Gatt, Marie C.; Rounds, Rachel; Horikoshi, Kazuo; Paiva, Vitor H.; Menezes, Dilia; Pereira, Eduarda; Catry, PauloGlobal mercury pollution has markedly and consistently grown over the past 70 years (although with regional variations in trends) and is a source of major concern. Mercury contamination is particularly prevalent in biota of the mesopelagic layers of the open ocean, but these realms are little studied, and we lack a large scale picture of contamination in living organisms of this region. The Bulwer's petrel Bulweria bulwerii, a species of migratory seabird, is a highly specialised predator of mesopelagic fish and squid, and therefore can be used as a bioindicator for the mesopelagic domain. Mercury accumulated by the birds through diet is excreted into feathers during the moulting process in adults and feather growth in chicks, reflecting contamination in the non-breeding and breeding periods, respectively, and hence the influence of different, largely non-overlapping breeding and non-breeding ranges. We studied mercury in feathers and the trophic position in two colonies from the Atlantic Ocean (Portugal and Cape Verde) and two colonies from the Pacific Ocean (Japan and Hawaii). We found significantly lower levels of mercury in adult and chick samples from the Pacific Ocean compared with samples from the Atlantic Ocean. However, we did not detect differences in trophic position of chicks among colonies and oceans, suggesting that differences in mercury measured in feathers reflect levels of environmental contamination, rather than differences in the structure of the trophic chain in different oceans. We conclude that despite a reduction in mercury levels in the Atlantic in recent decades, mesopelagic organisms in this ocean remain more heavily contaminated than in the Pacific at tropical and subtropical latitudes. We suggest that Bulwer's petrel is a highly suitable species to monitor the global contamination of mercury in the mesopelagic domain.
- Costs of reproduction and migration are paid in later return to the colony, not in physical condition, in a long-lived seabirdPublication . Gatt, Marie Claire; Versteegh, Maaike; Bauch, Christina; Tieleman, Irene; Granadeiro, José Pedro; Catry, PauloLife history theory suggests a trade-off between costly activities such as breeding and migration and somatic self-maintenance. However, how the short-term cost of parental effort is expressed in species with a slow pace-of-life is not well understood. Also, investigating carry-over effects of migration is most meaningful when comparing migratory strategies within the same population, but this has rarely been done. We explore this hypothesis in a long-lived, pelagic seabird, the Cory's Shearwater, Calonectris borealis, where males display partial migration. By manipulating reproductive effort and taking advantage of the natural variation in migratory strategy, we investigate whether early reproductive failure and migratory strategy had implications on the physical condition of males on return to the colony the following year. We experimentally induced breeding failure from mid-incubation, tracked the over-winter movements of these males and of males that invested in parental effort, and assessed innate immunity, stress, and residual body mass the following year. Early breeding failure resulted in earlier return to the colony among all males, associated with greater probability of reproductive success. Residents had a lower tail feather fault bar intensity, an indicator of stress during the non-breeding period, compared to migrants. Reproductive effort and migratory strategy had no impact on physiological condition otherwise. Our results provide evidence that in species with a slow-pace of life, such as the Cory's Shearwater, somatic maintenance is prioritised, with the costs of reproduction and migration paid in delayed arrival date.
- Sex‐specific telomere length and dynamics in relation to age and reproductive success in Cory's ShearwatersPublication . Bauch, Christina; Gatt, Marie Claire; Granadeiro, José Pedro; Verhulst, Simon; Catry, PauloIndividuals in free-living animal populations generally differ substantially in reproductive success, lifespan and other fitness-related traits and the molecular mechanisms underlying this variation are poorly understood. Telomere length and dynamics are candidate traits explaining this variation, as long telomeres predict a higher survival probability and telomere loss has been shown to reflect experienced "life stress". However, telomere dynamics among very long-lived species are unresolved. Additionally, it is generally not well understood how telomeres relate with reproductive success or sex. We measured telomere length and dynamics in erythrocytes to assess their relation to age, sex and reproduction in Cory's Shearwaters (Calonectris borealis), a long-lived seabird, in the context of a long-term study. Adult males had on average 231 bp longer telomeres than females independent of age. In females, telomere length changed relatively little with age, whereas male telomere length declined significantly. Telomere shortening within males from one year to the next was three times higher than the inter-annual shortening rate based on cross-sectional data of males. Past long-term reproductive success was sex-specifically reflected in age-corrected telomere length: males with on average high fledgling production were characterised by shorter telomeres, whereas successful females had longer telomeres and we discuss hypotheses that may explain this contrast. In conclusion, telomere length and dynamics in relation to age and reproduction are sex dependent in Cory's Shearwaters and these findings contribute to our understanding of what characterises individual variation in fitness.