Oxygen consumption of captive grey seals was measured over a period of 2.5 years at the captive facility of the Sea Mammal Research Unit at the University of St Andrews. The conditions under which in-water resting metabolic rate (RMR) was measured had a significant effect on the resulting estimates. RMR was highest when seals were at the surface breathing periodically. Surface apnoea and periodic submergence reduced RMR estimates by 25 and 35% respectively. There was significant seasonal variation in RMR's of adult females, with rates being highest in the spring and declining throughout the summer months. This variation was unrelated to changes in water temperature. Changes in mass explained some of this variation but this seasonality was still evident when rates were expressed mass-specifically. RMR of juvenile grey seals increased with age, as did lean body mass, although there was no relationship between age and total body mass. Diving metabolic rate (DMR) was measured while seals were voluntarily diving in a quasi- natural setting. Overall DMR was lower than RMR measured in the same animals. Mean DMR was 1.6 times predicted BMR. Average DMR decreased with dive duration and increased swimming activity during dives increased DMR. A model was developed that predicts DMR given information on the behaviour during the dive. This model was used to predict the at-sea metabolic rate of 5 wild grey seals from telemetry data. Overall, predicted at-sea metabolic rates were similar to DMR of the captive seals. Travelling dives had a higher energetic cost than foraging dives. Feeding during diving caused DMR to be increased 1.4-1.6 times pre-feeding levels. Metabolic rate data was incorporated into a population energy flux model. Energy requirements of different components of the population were estimated on a quarterly basis and all these were summed to produce an estimate of population annual energy requirements. Error in input parameters were used to calculate confidence limits in these estimates.

Firstly this study builds on the investigation initiated by Hall and Frame (2010), which found that Scottish harbour seals were exposed to domoic acid (DA), a potent natural neurotoxin produced by phytoplankton. Using the same sample collection technique to gather urine and faecal material from various populations around Scotland with differing population trajectories (Lonergan et al., 2007), the objective was to investigate not only exposure to DA, but also other groups of toxins such as paralytic shellfish poisoning (PSP) toxins and the lipophilic toxins okadaic acid (OA) and dinophysis toxins (DTXs). Toxins from harmful algae are thought to be potential causative factors in the on- going harbour seal decline in some regions of Scotland (Hall and Frame, 2010). This investigation was initiated because Pseudo-nitzschia (which produces DA) in particular was found to be highly prevalent in the phytoplankton communities in Scotland (Fehling et al., 2004; Stobo et al., 2008) and indeed was first observed at increased concentrations at around the time the harbour seal populations were observed as declining (Lonergan et al., 2007; Stobo et al., 2008). Prior to 2000 harbour seal populations in Scotland were largely stable or increasing. In addition DA exposure has had a devastating effect on the California sea lions (CSL) from the US west coast, where morbidity and mass mortality has occurred as a result of exposure (Goldstein et al., 2008; Gulland et al., 2002; Lefebvre et al., 1999; Scholin et al., 2000). In addition to the toxin analysis in urine and faecal samples, blood samples were collected and health parameters such as white blood cell and differential cell counts were investigated. Plasma cortisol concentrations and parasite faecal egg counts were additionally investigated as parameters indicative of adrenal function and parasite burden. CSL exposed to DA have significantly lower blood cortisol levels and higher eosinophil counts (Gulland et al., 2012) so it was possible that these indicators of effects might also be seen in the harbour seals. High parasite loads are often associated with high eosinophil levels (Klion and Nutman, 2004) so these data were needed to ensure any positive relationships found were linked to DA and were not a consequence of parasite burdens. The work presented in this thesis highlights the effect of exposure to the neurotoxin DA and documents that Scottish harbour seals are exposed to multiple toxins such as PSP toxins, OA and DTX-2 (Chapter 2, Chapter 4). Immunomodulatory effects of DA exposure such as lymphocytopenia and monocytosis are also reported. In general, harbour seals from the east coast and Northern Isles, where the decline in abundance has been greatest, had higher levels of DA in their excreta than animals from the west coast. The concentrations in the faeces and urine samples were generally low but time since exposure was unknown. Uptake of DA, PSP toxins, OA and DTXs in randomly selected fish from the east coast of Scotland in the Firth of Forth was investigated (Chapter 3), where benthic, flat and pelagic fish are shown to be vectors of toxin transfer and emphasis is drawn to flatfish as they seem to accumulate higher levels of toxins than the other species analysed. This indicates that harbour seals foraging off the east coast are likely to regularly encounter toxic prey that could impair their health. In addition to live captured harbour seals, samples from dead stranded marine mammals (including cetaceans and in particular harbour porpoise) found a range of species in Scottish waters were exposed to both DA and PSP toxins (Chapter 4). A monitoring tool to rapidly determine chronic DA exposure in blood samples was published recently for DA exposed CSLs and in Chapter 5 this monitoring technique was attempted in phocid seals, and where it failed to be replicated or validated which questions its function as a DA monitoring tool. Questions regarding how quickly a marine mammal excretes DA from the body have been discussed in the literature and in Chapter 6 an experiment was set up to measure the clearance of DA by using a biomarker (Iohexol). Iohexol was successfully measured in plasma samples from captive harbour seals following oral intake, where concentration and time of the iohexol peak was identified together with the calculation of its half-life. These results indicate the approximate elimination rate of DA (and potentially other hydrophilic toxins) and can be used to better interpret urine levels of DA measured in wild caught harbour seals. Collectively the results of this research will enable the risk posed by the ingestion of various toxins present in the Scottish marine food chain to marine mammals (particularly harbour seals but also harbour porpoise and grey seals) to be assessed.

The Caspian seal (Pusa caspica), which is endemic to the Caspian Sea, is listed as 'endangered' by IUCN due to a severe population decline and a number of unresolved threats. The results of aerial surveys of the Caspian seal population on their breeding ice habitat 2005-2012 are outlined in the Chapter 2. They demonstrated extreme fluctuations in pup production estimates between consecutive years which might be result of sampling error or underlying biological drivers influencing the fecundity of the population. The results of satellite tracking of Caspian seals in 2008-2012 are presented in the Chapters 3 and 4 including analysis of movements and habitat use respectively. In Chapter 3 the true path of seals was predicted by state-space modelling (SSM) and two behavioural states were distinguished from the locations: 'travelling' and 'foraging'. Chapter 4 used SSM results to identify important foraging areas and seasonal patterns of habitat usage. The results revealed high individual variation in habitat use which suggested individual foraging specialization in Caspian seal. The North Caspian is suggested to be a highly important habitat area for the Caspian seals throughout the year, where seals breed, moult, forage during their migrations and large proportion of seals (40% in our sample) stay for the whole all ice-free period. Chapter 5 presented first quantitative assessment of fisheries by-catch mortality of Caspian seals by interviews in fishing communities along the coasts of Russia (Kalmykia, Dagestan), Kazakhstan and Turkmenistan and revealed high by-catch rates related with sturgeon poaching. High by-catch mortality rates and overlap between critical habitat areas used by seals and human activities revealed by the study should cause concern for stakeholders. These results of the thesis can be used for developing and implementing effective conservation strategies for Caspian seals.

No description available.

No description available.

Worldwide harbour seal populations are showing differing and fluctuating trends in abundance, but the drivers of change remain uncertain. Within the Moray Firth, NE Scotland, count surveys carried out over the last 20 years highlighted the development of a new breeding site, providing a unique opportunity to carry out an individual-based study of harbour seal demography and pupping phenology using photo-identification techniques within a mark-recapture framework. Sightings of individual seals suggested that a large proportion of harbour seals are year-round residents at haul-out sites. Both sexes displayed high levels of between-year breeding site fidelity as well as seasonal variation in their haul-out behaviour. Apparent sex-specific survival rates (0.89♂, 0.97♀) and birth rates (0.88) were high. There was a strong correlation between lactation durations and the timing of pupping, suggesting that shifts in pupping phenology are a result of energetic constraints. This highlights the potential for using the timing of pupping as an indicator of ecosystem conditions. This study provided the first concurrent real-time estimates of survival and fecundity in a naturally regulated population of harbour seals. Demographic parameters and physiological responses indicate that prevailing conditions within the Moray Firth are favourable, and that this population should be recovering. However, observed patterns may also be an artefact of the long-term decline having caused an increase in per capita food availability through the reduction in intra-specific competition. This study highlights the current and long-term importance of individual-based data in understanding population dynamics. Through the identification of sentinel sites around the world, harbour seals could provide a single-species indicator of coastal ecosystem conditions in the Northern Hemisphere.

Animal communication systems are complex, but in many species relatively little is known about how they develop. Insight into the development of adult repertoires, considering how factors such as genetics, environment and learning contribute to signal changes, provides a more comprehensive understanding of communication. This thesis documented vocal learning and development in the grey seal. In chapter 3, vocal repertoires of grey seal pups were recorded from birth through their first year, and were compared to calls of other seals across life stages, from pups to adults. By examining call parameters that were similar in animals of the same age, size, and sex, changes that may be attributed to physical development and morphology were identified. Past studies have indicated that seals may also have advanced vocal learning abilities, however the extent of these capabilities was unknown. In this thesis, vocal learning in juvenile grey seals was tested considering both how the seals learn to produce calls as well as gain information from perceived sounds. In chapter 4, grey seals were shown to be capable of vocal usage learning by producing specific calls in specific contexts. In chapter 5, grey seals displayed control over the structure of their calls as they could imitate novel sound models, demonstrating vocal production learning. Lastly, in chapter 6 grey seals gained information from perceived sound signals and used them to their benefit to locate food, demonstrating acoustic comprehension learning. Adult grey seals have complex call repertoires, and in this thesis I have shown how their calls develop with physiological growth and experience, as well as how they can gain information from perceived sound signals.