Developing health and welfare assessment tools for harbour (Phoca vitulina) and grey seals (Halichoerus grypus) in rehabilitation centres

Harbour (Phoca vitulina) and grey (Halichoerus grypus) seals face numerous anthropogenic and environmental threats around the UK and Ireland. These commonly lead to seal pups becoming stranded and in need of rescue and rehabilitation. Although rehabilitation supports the recovery and welfare of stranded seals, our understanding of their species-specific responses to the rehabilitation process, and effective methods for assessing their health and welfare remain limited. This thesis will develop health and welfare assessment tools for harbour and grey seals in rehabilitation centres. It will identify admission reasons and physiological and behavioural indicators of stress, as well as developing parasite detection methods, in order to identify vulnerable individuals, monitor and reduce their allostatic load, and optimise their welfare throughout the rehabilitation process. In particular, this thesis will: i) determine the causes of seal admittance to rehabilitation centres, ii) investigate the predictors of survival, iii) develop an enzyme-linked immunosorbent assay for faecal cortisol metabolites (FCMs), iv) identify factors associated with changes in FCM levels and behaviour, and v) develop a lab-on-a-chip device for parasite detection. Chapter 2 explores factors affecting seal survival and stranding trends using rehabilitation records from centres across the UK and Ireland. The findings provide valuable insights into the most common pup stranding conditions and demonstrate that the survival likelihood is significantly influenced by species and individual weight at admission. Chapter 3 then focuses on the development of an enzyme-linked immunosorbent assay (ELISA) for measuring FCMs as a potential non-invasive biomarker of stress. In Chapter 4, this ELISA is used to monitor FCM levels throughout rehabilitation, alongside behavioural time budgets. While results show that FCM levels were not associated with factors such as sex, time in care, feeding method, time of day, water access, or age-weight residuals, their behavioural time budgets were significantly affected by feeding method, water access, age-weight residuals, and time of day, highlighting the importance of behavioural monitoring in welfare assessments. Finally, Chapter 5 presents the development of a lab-on-a-chip device for the rapid detection of lungworm DNA in seals and demonstrates that it can facilitate accurate diagnosis of parasitic infections in non-laboratory settings. Based on findings from these experimental chapters, specific recommendations are made to enhance rehabilitation protocols, including: i) the use of weight monitoring for survival likelihood estimation; ii) prioritising behavioural monitoring for welfare assessments, given the limited utility of FCM analysis in reflecting individual stress; iii) incorporation of enrichment to optimise welfare; and iv) the use of on-site molecular diagnostic tools for parasite detection and identification. Overall, the implementation of these recommendations is intended to maximise the effectiveness of rehabilitation and improve the welfare and survival of stranded harbour and grey seal pups.