Raül Ramos

Trace me if you can: the use of intrinsic biogeochemical markers in marine top predators

Human activities have serious impacts on marine apex predators. Inadequate knowledge of the spatial and trophic ecology of these marine animals ultimately compromises the viability of their populations and impedes our ability to use them as environmental biomonitors. Intrinsic biogeochemical markers, such as stable isotopes, fatty acids, trace elements, and chemical pollutants, are increasingly being used to trace the spatial and trophic ecology of marine top predators. Notable advances include the emergence of the first oceanographic “isoscapes” (isotopic geographic gradients), the advent of compound-specific isotopic analyses, improvements in diet reconstruction through Bayesian statistics, and tissue analysis of tracked animals to ground-truth biogeochemical profiles. However, most researchers still focus on only a few tracers. Moreover, insufficient knowledge of the biogeochemical integration in tissues, fractionation and routing processes, and geographic and temporal variability in baseline levels co...

Diet of Yellow-legged Gull (Larus michahellis) chicks along the Spanish Western Mediterranean coast: the relevance of refuse dumps

In recent decades, the Yellow-legged Gull (Larus michahellis) has become a problematic species in many Mediterranean countries, mainly because it interferes with human interests. However, this gull also has a negative impact on several other bird species, many of which are classified as endangered. Two different European Union Action Plans are currently under development with the aim of decreasing the availability of food derived from human activities, such as garbage and fishery discards, which are considered to be the main causes of the superpopulations of this gull. Here, we describe the diet of Yellow-legged Gull chicks, with particular emphasis on establishing the dependence of each population on refuse dumps, in order to forecast changes in gull population dynamics in response to the management decisions being implemented. We sampled four colonies along the Western Mediterranean in Spain: the Medes Islands, the Ebro Delta, the Columbretes Islands, and Mazarrón Island. To elucidate their feeding ecology and to avoid obtaining a discrete estimation from a single sampling, we collected regurgitates from each colony three times throughout the chick-rearing period. Slightly differential feeding habits were observed between chick age classes. Younger chicks in all four colonies tended to be consistently provisioned with smaller prey such as invertebrates. Distinct uses of several foraging habitats among localities were observed. In particular, the use of refuse dumps was common and abundant in two of the colonies: the Medes and Mazarrón Islands. As a consequence of current management strategies, generalized reductions in Yellow-legged Gull populations and increases in the consumption of alternative food resources to those of fishery discards and refuse scraps are expected. Finally, we predict that decreased food availability will force some gulleries to increase predation on endangered species, thereby raising a conservation concern.

Maternal antibody persistence: a neglected life-history trait with implications from albatross conservation to comparative immunology

The evolution of different life-history strategies has been suggested as a major force constraining physiological mechanisms such as immunity. In some long-lived oviparous species, a prolonged persistence of maternal antibodies in offspring could thus be expected in order to protect them over their long growth period. Here, using an intergenerational vaccination design, we show that specific maternal antibodies can display an estimated half-life of 25 days post-hatching in the nestlings of a long-lived bird. This temporal persistence is much longer than previously known for birds and it suggests specific properties in the regulation of IgY immunoglobulin catabolism in such a species. We also show that maternal antibodies in the considered procellariiform species are functional as late as 20 days of age. Using a modelling approach, we highlight that the potential impact of such effects on population viability could be important, notably when using vaccination for conservation. These results have broad implications, from comparative immunology to evolutionary eco-epidemiology and conservation biology.

Linking isotopic and migratory patterns in a pelagic seabird

The value of stable isotope analysis in tracking animal migrations in marine environments is poorly understood, mainly due to insufficient knowledge of isotopic integration into animal tissues within distinct water masses. We investigated isotopic and moult patterns in Cory’s shearwaters to assess the integration of different stable isotopes into feathers in relation to the birds’ transoceanic movements. Specimens of Mediterranean Cory’s shearwater Calonectris diomedea diomedea caught accidentally by Catalan longliners were collected and the signatures of stable isotopes of C (δ13C), N (δ15N) and S (δ34S) were analysed in 11 wing and two tail feathers from 20 birds, and in some breast feathers. Based on isotopic signatures and moult patterns, the feathers segregated into two groups (breeding and wintering), corresponding to those grown in the Mediterranean or Atlantic regions, respectively. In addition, feathers grown during winter, i.e. moulted in Atlantic waters, were grouped into two isotopically distinct profiles, presumably corresponding to the two main wintering areas previously identified for Mediterranean Cory’s shearwater in tracking studies. N signatures mainly indicated the Mediterranean-to-Atlantic migration, whereas C and S signatures differed according to the Atlantic wintering area. Our results indicate that isotopic signatures from distant oceanic regions can integrate the feathers of a given bird and can indicate the region in which each feather was grown. This study thus underscores how stable isotope analysis can link marine animals to specific breeding and wintering areas, and thereby shed new light on studies involving assignment, migratory connectivity and carry-over effects in the marine environment.

Influence of Refuse Sites on the Prevalence of Campylobacter spp. and Salmonella Serovars in Seagulls

ABSTRACT Wild animals are well-known reservoirs of Campylobacter and Salmonella. We investigated the influence of insalubrious diets on the prevalence of both enterobacteria in seagulls. Campylobacter occurrence in gull chicks sampled along the northeastern Iberian coast was directly related to the degree of refuse consumption. High Salmonella values from the sampling sites did not reflect any dietary relationship.

Understanding Oceanic Migrations with Intrinsic Biogeochemical Markers

Migratory marine vertebrates move annually across remote oceanic water masses crossing international borders. Many anthropogenic threats such as overfishing, bycatch, pollution or global warming put millions of marine migrants at risk especially during their long-distance movements. Therefore, precise knowledge about these migratory movements to understand where and when these animals are more exposed to human impacts is vital for addressing marine conservation issues. Because electronic tracking devices suffer from several constraints, mainly logistical and financial, there is emerging interest in finding appropriate intrinsic markers, such as the chemical composition of inert tissues, to study long-distance migrations and identify wintering sites. Here, using tracked pelagic seabirds and some of their own feathers which were known to be grown at different places and times within the annual cycle, we proved the value of biogeochemical analyses of inert tissue as tracers of marine movements and habitat use. Analyses of feathers grown in summer showed that both stable isotope signatures and element concentrations can signal the origin of breeding birds feeding in distinct water masses. However, only stable isotopes signalled water masses used during winter because elements mainly accumulated during the long breeding period are incorporated into feathers grown in both summer and winter. Our findings shed new light on the simple and effective assignment of marine organisms to distinct oceanic areas, providing new opportunities to study unknown migration patterns of secretive species, including in relation to human-induced mortality on specific populations in the marine environment.

The influence of breeding colony and sex on mercury, selenium and lead levels and carbon and nitrogen stable isotope signatures in summer and winter feathers of Calonectris shearwaters

Contamination in marine foodwebs is nowadays of great environmental concern owing to the increasing levels of pollution in marine ecosystems from different anthropogenic sources. Seabirds can be used as indicators of regional contaminant patterns across large temporal and spatial scales. We analysed Hg, Se and Pb levels as well as stable isotope ratios of C (13C/12C, δ13C) and N (15N/14N, δ15N) in breeding- and winter-season feathers on males and females of two related shearwater species, providing information on spatiotemporal patterns of contaminants as well as the influence of the trophic ecology of these seabirds on contaminant levels. During the breeding season, Se and Pb concentrations were highest at the Cape Verde archipelago, showing no differences among the other colonies or between the sexes. However, Hg levels varied among colonies, being highest in the Mediterranean, probably resulting from the larger emissions and fallout of this pollutant in Europe. Feathers grown during breeding also showed sexual differences in Hg concentrations and δ13C. Differences in Hg concentration between sexes are mainly due to egg-laying decontamination in females. In contrast, differences in Hg among colonies are probably related to differences in trophic ecology, as indicated by δ13C and δ15N measurements. Contaminant concentrations in winter-grown feathers did not show any relationship with stable isotope values but were affected by contaminant loads associated with the breeding season. These findings suggest that the interpretation of contaminant levels of migratory species from feathers moulted out of the breeding season should be made with caution because those values could reflect exposures to contaminants acquired during the breeding season. We conclude that factors other than feeding ecology may play an important role in the interpretation of contaminant levels and their annual dynamics at several spatial scales. Consideration of the relevant temporal context provided by isotopic signatures and contaminant concentrations is important in deciphering contaminant information based on various tissues.

Combined Spatio-Temporal Impacts of Climate and Longline Fisheries on the Survival of a Trans-Equatorial Marine Migrant

Predicting the impact of human activities and their derivable consequences, such as global warming or direct wildlife mortality, is increasingly relevant in our changing world. Due to their particular life history traits, long-lived migrants are amongst the most endangered and sensitive group of animals to these harming effects. Our ability to identify and quantify such anthropogenic threats in both breeding and wintering grounds is, therefore, of key importance in the field of conservation biology. Using long-term capture-recapture data (34 years, 4557 individuals) and year-round tracking data (4 years, 100 individuals) of a trans-equatorial migrant, the Cory’s shearwater (Calonectris diomedea), we investigated the impact of longline fisheries and climatic variables in both breeding and wintering areas on the most important demographic trait of this seabird, i.e. adult survival. Annual adult survival probability was estimated at 0.914±0.022 on average, declining throughout 1978–1999 but recovering during the last decade (2005–2011). Our results suggest that both the incidental bycatch associated with longline fisheries and high sea surface temperatures (indirectly linked to food availability; SST) increased mortality rates during the long breeding season (March-October). Shearwater survival was also negatively affected during the short non-breeding season (December-February) by positive episodes of the Southern Oscillation Index (SOI). Indirect negative effects of climate at both breeding (SST) and wintering grounds (SOI) had a greater impact on survival than longliner activity, and indeed these climatic factors are those which are expected to present more unfavourable trends in the future. Our work underlines the importance of considering both breeding and wintering habitats as well as precise schedules/phenology when assessing the global role of the local impacts on the dynamics of migratory species.

Comparative phylogeography of two widespread magpies: Importance of habitat preference and breeding behavior on genetic structure in China

Historical geological events and climatic changes are believed to have played important roles in shaping the current distribution of species. However, sympatric species may have responded in different ways to such climatic fluctuations. Here we compared genetic structures of two corvid species, the Azure-winged Magpie Cyanopica cyanus and the Eurasian Magpie Pica pica, both widespread but with different habitat dependence and some aspects of breeding behavior. Three mitochondrial genes and two nuclear introns were used to examine their co-distributed populations in East China and the Iberian Peninsula. Both species showed deep divergences between these two regions that were dated to the late Pliocene/early Pleistocene. In the East Chinese clade of C. cyanus, populations were subdivided between Northeast China and Central China, probably since the early to mid-Pleistocene, and the Central subclade showed a significant pattern of isolation by distance. In contrast, no genetic structure was found in the East China populations of P. pica. We suggest that the different patterns in the two species are at least partly explained by ecological differences between them, especially in habitat preference and perhaps also breeding behavior. These dissimilarities in life history traits might have affected the dispersal and survival abilities of these two species differently during environmental fluctuations.

Global spatial ecology of three closely-related gadfly petrels

The conservation status and taxonomy of the three gadfly petrels that breed in Macaronesia is still discussed partly due to the scarce information on their spatial ecology. Using geolocator and capture-mark-recapture data, we examined phenology, natal philopatry and breeding-site fidelity, year-round distribution, habitat usage and at-sea activity of the three closely-related gadfly petrels that breed in Macaronesia: Zino’s petrel Pterodroma madeira, Desertas petrel P. deserta and Cape Verde petrel P. feae. All P. feae remained around the breeding area during their non-breeding season, whereas P. madeira and P. deserta dispersed far from their colony, migrating either to the Cape Verde region, further south to equatorial waters in the central Atlantic, or to the Brazil Current. The three taxa displayed a clear allochrony in timing of breeding. Habitat modelling and at-sea activity patterns highlighted similar environmental preferences and foraging behaviours of the three taxa. Finally, no chick or adult was recaptured away from its natal site and survival estimates were relatively high at all study sites, indicating strong philopatry and breeding-site fidelity for the three taxa. The combination of high philopatry, marked breeding asynchrony and substantial spatio-temporal segregation of their year-round distribution suggest very limited gene flow among the three taxa.