Environmental drivers of variability in population and individual foraging strategies

Efficient foraging can offer individuals a key opportunity to maximise fitness, with important consequences for population dynamics, species distributions, and ecosystem processes. The constant quest to minimise costs and maximise resource gains has given rise to a diverse range of movement behaviours among animals, the complexities of which we are continually uncovering as we accumulate more data, advance technology and develop methods. We know that animals typically forage on patchy resources that seldom stay constant in space or time. However, it remains unknown whether the degree of resource patchiness, or resource heterogeneity, can shape the costs and benefits of foraging, thus affecting foraging movements and population dynamics of animals. The overall aims of this study were therefore to use environmental, movement, and reproductive success data to understand how resource heterogeneity can drive individual and population foraging behaviour. We focus on the ecology of black-legged kittiwakes, Rissa tridactyla, which are a model species for such questions. As central place breeders that feed solely at the surface, kittiwakes are sensitive to changes in prey availability within the environment around their colony. Furthermore, kittiwakes have been widely studied as an ecosystem indicator species, and so we can build upon prior knowledge and benefit from a large body of existing data. To determine foraging behaviour I use GPS tracking data from 15 colonies around the UK and Ireland collected during the breeding seasons between 2010 and 2017; totalling 415 individuals and 1567 foraging trips. These tracking data were combined with environmental data to determine foraging habitat selection and variability over a predictable cycle, and to characterise environmental heterogeneity, as a proxy for resource heterogeneity, within the foraging range of kittiwakes at each colony. I compare environmental heterogeneity to foraging dynamics and reproductive success to understand the potential fitness costs and benefits of foraging in heterogeneous environments. Finally, I extend habitat selection functions to quantify individual specialisation in habitat selection between colonies, and to understand whether environmental heterogeneity could shape the diversity of movement behaviours. Studies revealed that habitat selection differed over the 12.4-h tidal cycle; and that environmental heterogeneity was associated with amplified changes in habitat selection, most likely because of greater spatial variability in temporal resource changes. In more heterogeneous environments, kittiwakes undertook longer foraging trips, overlapped more with other individuals, and had lower breeding success, which suggests that there is greater competition between individuals where resources are clustered into patches, at a cost to reproduction. Potentially as a mechanism to reduce competition, individual specialisations in habitat selection were more prevalent in heterogeneous environments. Together, results highlight the importance of local environmental processes in governing behavioural adaptations of predators. Chapters provide novel advances into the ecology of kittiwakes, but also into the drivers of optimal foraging trade-offs and the origins of individual differences in behaviour that are relevant well beyond this species. Overall, the work presented in this thesis demonstrates that environmental heterogeneity can play a key role in shaping foraging movements of individuals, population dynamics, and potentially the diversity of animal behaviour

Contaminants in northern fulmars (Fulmarus glacialis) exposed to plastic

Northern fulmars are seabirds which feed exclusively at sea, and as such, they are useful indicators of ocean health. Marine plastic pollution is an ever-increasing and global issue that affects the northern fulmar as they are frequently found to have ingested plastic. In this report we investigate whether the amount of ingested plastic affects the concentration of certain plastic-adsorbed toxicants in their tissues. Marine plastic pollution is a field of utmost importance. It is our hope that this continues to be an area which receives increased attention in order to elucidate the potential harmful effects plastics have on the northern fulmar and ocean health, in general

The Arctic Ocean as a dead end for floating plastics in the North Atlantic branch of the Thermohaline Circulation

The subtropical ocean gyres are recognized as greatmarine accummulation zones of floating plastic debris; however, the possibility of plastic accumulation at polar latitudes has been overlooked because of the lack of nearby pollution sources. In the present study, the Arctic Oceanwas extensively sampled for floating plastic debris fromthe TaraOceans circumpolar expedition. Although plastic debris was scarce or absent in most of the Arctic waters, it reached high concentrations (hundreds of thousands of pieces per square kilometer) in the northernmost and easternmost areas of the Greenland and Barents seas. The fragmentation and typology of the plastic suggested an abundant presence of aged debris that originated from distant sources. This hypothesis was corroborated by the relatively high ratios of marine surface plastic to local pollution sources. Surface circulation models and field data showed that the poleward branch of the Thermohaline Circulation transfers floating debris from the North Atlantic to the Greenland and Barents seas, which would be a dead end for this plastic conveyor belt. Given the limited surface transport of the plastic that accumulated here and the mechanisms acting for the downward transport, the seafloor beneath this Arctic sector is hypothesized as an important sink of plastic debris

Multi-colony tracking reveals segregation in foraging range, space use, and timing in a tropical seabird

Colonial animals experience density-dependent competition for food, which is posited to influence foraging range and lead to inter-colony segregation. However, such patterns are poorly studied in the tropics, where predictable day lengths, oligotrophic conditions, and facultative foraging may alter the relationships between foraging and intra-specific competition. Here, we GPS-tracked 207 breeding red-footed boobies Sula sula rubripes (RFB) from 4 neighbouring Chagos Archipelago colonies (~1100 to 9200 breeding pairs) in the central Indian Ocean, to determine how foraging strategies (i.e. effort, segregation, and timing) vary with colony, while accounting for sex, monsoon season, stage of reproduction, year, and individual. During incubation and chick-rearing, RFBs commute to pelagic foraging grounds (maximum distance mean ± SE: 112.9 ± 3.7 km; total distance: 298.4 ± 6.2 km) over 1 to 5 d (18.5 ± 1.6 h). Foraging effort was highest at the largest colony, and greater among females than males. Departure angles varied among colonies, leading to foraging areas that were largely spatially segregated. Timing of departures and arrivals were strongly constrained by daylight hours, although females and birds at the largest colony left earliest. Our study highlights the importance of inter-colony differences in tropical seabird foraging, which may relate to different levels of intra-specific competition. Moreover, links between foraging times and colony size suggest a previously undescribed outcome of density-dependent competition, highlighting the importance of understanding colonial living across multiple dimensions.</jats:p

Habitat selection and spatial behaviour of vulnerable juvenile lemon sharks: Implications for conservation

This is the final version. Available on open access from Elsevier via the DOI in this record.Data availability. Data will be made available on request.Nearshore environments represent important habitat for many marine vertebrates during their early-life stages. Globally, these coastal sites are impacted by human activities that have the potential to negatively impact biodiversity in ways we do not yet fully appreciate. To improve our understanding of the relevance of mangrove removal in tropical elasmobranch nursery grounds, we studied the globally Vulnerable lemon shark (Negaprion brevirostris) in a mangrove-fringed lagoon in Bimini, The Bahamas, following a decade of coastal development and habitat disruption. We used two years of acoustic telemetry detections and generalised linear mixed models (GLMMs) to evaluate the link between juvenile shark spatial behaviour and six features of their physical environment. AIC-adjusted model-averaged predictions of habitat selection demonstrated that distance from the central mangrove forest was the most important feature for sharks. After updating model averaging to account for overall preference for proximity to the central forest, we found that medium density seagrass was secondarily preferred over all other habitat types (bare sand, sargassum, urban and rocky outcrops, and deep water) within the core use area (probability of use ≥ 50 %). Locally, our results support including this core area in future marine protected area considerations. More broadly, in the face of rapid global population declines of many elasmobranchs and wide-spread habitat fragmentation in coastal marine nurseries, we identified widely applicable habitat features underpinning an area of high ecological significance for a threatened shark during a vulnerable life stage and outlined a habitat selection framework suitable for using marine vertebrate movement data as ecological indicators for future applied conservation.Prindiville familySave Our Seas Foundatio

Marine Important Bird and Biodiversity Areas in the Chagos Archipelago

This is the final version. Available on open access from Cambridge University Press via the DOI in this recordSeabirds are declining globally and are one of the most threatened groups of birds. To halt or reverse this decline they need protection both on land and at sea, requiring site-based conservation initiatives based on seabird abundance and diversity. The Important Bird and Biodiversity Area (IBA) programme is a method of identifying the most important places for birds based on globally agreed standardised criteria and thresholds. However, while great strides have been made identifying terrestrial sites, at-sea identification is lacking. The Chagos Archipelago, central Indian Ocean, supports four terrestrial IBAs (tIBAs) and two proposed marine IBAs (mIBAs). The mIBAs are seaward extensions to breeding colonies based on outdated information and, other types of mIBA have not been explored. Here, we review the proposed seaward extension mIBAs using up-to-date seabird status and distribution information and, use global positioning system (GPS) tracking from Red-footed Booby Sula sula – one of the most widely distributed breeding seabirds on the archipelago – to identify any pelagic mIBAs. We demonstrate that due to overlapping boundaries of seaward extension to breeding colony and pelagic areas of importance there is a single mIBA in the central Indian Ocean that lays entirely within the Chagos Archipelago Marine Protected Area (MPA). Covering 62,379 km2 it constitutes ~10% of the MPA and if designated, would become the 11th largest mIBA in the world and 4th largest in the Indian Ocean. Our research strengthens the evidence of the benefits of large-scale MPAs for the protection of marine predators and provides a scientific foundation stone for marine biodiversity hotspot research in the central Indian Ocean.Bertarelli Foundatio