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In a context where human-wildlife conflicts are expected to be more frequent due to the expansion and intensification of human activities (e.g. tourism, agriculture, urbanisation, outdoor sports), instituting wildlife management policies promoting sustainable coexistence is more needed than ever. Investigating what are the main drivers of ungulates population dynamics and their responses to global changes (i.e. climate change and landscape anthropization), is then crucial if we aim to infer efficient management practices. Consequently, and as population dynamics and distribution are often the results of fine-scaled behaviours made by individual, we proposed through this thesis work, to more particularly explore the link between spatial behaviours, internal factors and environmental constraints. Based on the data from the monitoring of three wild ungulates species, i.e. roe deer Capreolus capreolus, mediterannean mouflon Ovis gmelini musimon x Ovis sp., and chamois Rupicapra rupicapra, we first showed that age was a major determinant of animals' spatial behaviours. During the rutting period, older roe deer males travelled greater daily distances than younger males due to patrolling behaviours for territory defence, whereas older mouflon males travelled less than younger males, which often adopted coursing tactics to mate with females. During the birth period, reproductive females had smaller home ranges than non-reproductive females in roe deer, whereas no marked differences were observed in mouflon females. The most marked age-related variation in space use of mouflon occurred outside the reproductive periods; specifically, the oldest individuals travelled less far and had a smaller home range (females only) than younger individuals. Similarly, in another study, we also showed that older chamois females visited locations with higher forage quantity than younger females, possibly because of their higher experience or locomotor senescence. We then demonstrated that external factors such as temperature and local landscape constraints, may also shape animals' behavioural responses. Individuals which had access to more thermal refuges such as forests and northern slopes, tended to increase their use of these habitats during days of high temperatures. This however was associated with opportunity costs, as thermal refuges typically offered decreased forage conditions, forcing in return these same individuals to increase their time spent foraging and relocating in order to gather sufficient resources. Overall, our results demonstrated that individual variability in age and in local landscape constraints induces among-individual heterogeneity in behavioural tactics, which are likely to result into individual differences in energy budgets that remains now to be explored in further studies.

With the increasing threats of climate change, there is an ever-pressing need to reduce fossil fuel emissions. Thus, recent years have seen a dramatic increase in the development of marine renewable energy (MRE) devices - in particular tidal stream turbines (TSTs) - to exploit tidal stream environments (TSEs) for green electricity generation. However, TSTs may pose threats to marine megafauna and relatively little is known about how animals operate in the environments targeted by these devices, and how they may be affected by them. This information is crucial for informing appropriate management strategies to mitigate the risk of conflict between animals and TST developments. Here, using grey seals (Halichoerus grypus) and harbour seals (Phoca vitulina) as my study species, with data collected from around the UK and neighbouring waters, including the Celtic and the North Sea, I aim to understand and quantify how seals move in TSEs and the implications of this for the TST industry. To achieve this, I quantify the broad-scale movement patterns of seals in coastal waters and their overlap with TSTs, examine the fine-scale movement and behaviour of seals in response to tidal conditions, derive recommendations on sample size and recording duration for animal tracking studies, and design new tags to track seals in TSEs at very fine-scales whilst minimising tag impact. My results suggest that the movements and behaviour of seals are driven by a combination of measurable (and in some cases predictable) demographic and environmental factors, and that the conservation strategies developed to manage the interaction between individuals and populations with TST devices must consider site-specific differences and account for individual variation, with consequences regarding data requirements. Further investigation is required to fully elucidate the extent of variability of seal movements in TSEs and the threats of TST developments, however the research presented herein provides new tools and ecological insights to support this need for both researchers and practitioners.

How animals behave is fundamental to enhancing their lifetime fitness, so defining how animals move in space and time relates to many ecological questions, including resource selection, activity budgets and animal movement networks. Historically, animal behaviour and movement has been defined by direct observation, however recent advancements in biotelemetry have revolutionised how we now assess behaviour, particularly allowing animals to be monitored when they cannot be seen. Studies now pair 'convectional' radio telemetries with motion sensors to facilitate more detailed investigations of animal space-use. Motion sensitive tags (containing e.g., accelerometers and magnetometers) provide precise data on body movements which characterise behaviour, and this has been exemplified in extensive studies using accelerometery data, which has been linked to space-use defined by GPS. Conversely, consideration of body rotation (particularly change in yaw) is virtually absent within the biologging literature, even though various scales of yaw rotation can reveal important patterns in behaviour and movement, with animal heading being a fundamental component characterising space-use. This thesis explores animal body angles, particularly about the yaw axis, for elucidating animal movement ecology. I used five model species (a reptile, a mammal and three birds) to demonstrate the value of assessing body rotation for investigating fine-scale movement-specific behaviours. As part of this, I advanced the 'dead-reckoning' method, where fine-scale animal movement between temporally poorly resolved GPS fixes can be deduced using heading vectors and speed. I addressed many issues with this protocol, highlighting errors and potential solutions but was able to show how this approach leads to insights into many difficult-to-study animal behaviours. These ranged from elucidating how and where lions cross supposedly impermeable man-made barriers to examining how penguins react to tidal currents and then navigate their way to their nests far from the sea in colonies enclosed within thick vegetation.

Seagrasses structure some of the world's key coastal ecosystems presently in decline due to human activities and global change. Population genetic analysis is an important tool for understanding genetic resources and adaptation, with great potential to inform marine spatial planning and other management decisions. This thesis addresses questions regarding the genetic diversity of extant populations, and how this information can aid current conservation and restoration efforts. In chapter 2, I aimed to assess the use of an existing panel of 15 microsatellites as a tool for understanding population genetic structure in widely distributed seagrass species, Zostera marina, from five meadows around the UK. These results from the pilot study showed that the proposed panel of microsatellites can provide high quality data from seagrass samples. Importantly, all microsatellite loci were polymorphic at this scale. In chapter 3, I estimated allelic diversity in eelgrass, Z. marina, at five sites around the Isles of Scilly Special Area of Conservation, UK, in 2010 and compared this to 23 years of annual ecological monitoring data (1996-2018). I found low genetic diversity and long-term declines in abundance amongst five sites around the Isles of Scilly, which is an isolated location approximately 25 miles off the southwest tip of the UK. In chapter 4, I further developed Z. marina around the Isles of Scilly as a natural model system to compare measures of resilience derived from demographic and morphological trait variability, long-term population dynamics and population genetics, which, is rarely done in a single study. I found allele richness, spatial variability in shoot morphology, resilience in local shoot dynamics were correlated and separately that resistance at a broader vegetation spatial scale are correlated. In chapter 5, I aimed to quantify genetic variation in eelgrass, Z. marina, and identify patterns associated with local environment from 18 meadows across the southwest of England and West of Wales, clustered into six sites: Gelliswick (1 seagrass meadow), Looe (1 seagrass meadow), Plymouth (6 seagrass meadows), Salcombe (1 seagrass meadow), Torbay (6 seagrass meadows), Weymouth (3 seagrass meadows). Across the southwest of England and West of Wales, eelgrass was not in Hardy-Weinberg equilibrium, indicating some local restriction of gene flow within sites. I also explored spatial structure through quantifying isolation by distance and inferred that connectivity between local sites on the coast potentially mitigates against population genetic restriction at the broader spatial scale, I estimated genetic variation in eelgrass between meadows and compared this to six environmental variables - depth, photosynthetically available light at the seabed (PAR), the coefficient of light attenuation (KDPAR), kinetic energy due to waves (KeW) and kinetic energy due to currents (KeC). I found that intermediate depths were associated with the highest allele richness and clonal richness, with intermediate available light associated with minimum clonal richness. Overall, my study highlights the need to understand the link between population genetics and environmental variables to improve responses to threats against this internationally important ecosystem.