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The world is facing an unprecedented loss of biodiversity caused by anthropogenic environmental change. Captive breeding and reintroduction can help mitigate the effects of biodiversity loss for some endangered species, but to accomplish this, captive populations need to be self-sustainable. Intensive population management aims to achieve sustainability by maximising the retention of genetic diversity, maintaining demographic stability, and reducing adaptation to captivity. Recent evaluations of captive populations have indicated that many are not meeting their genetic and demographic goals, and are not sustainable. Consequently, their contribution to biodiversity conservation is being undermined. This thesis aims to evaluate the sustainability of captive populations using the scimitarhorned oryx as a case study. The European scimitar-horned oryx population experiences many of the challenges encountered by other captive populations, specifically, poor data quality in the international studbook resulting in less effective population management; rapid loss of genetic variation; and economic fragmentation. This thesis presents a series of original studies that evaluate the sustainability of captive populations, examines the impact of poor quality data on population management, and tests the effects of population fragmentation. The results contribute knowledge to the management of small captive populations in general, and to the scimitar-horned oryx in particular. I propose solutions to some of the challenges faced by endangered species in captivity, and advocate a reorientation of the existing small population management paradigm. Finally, I challenge the international zoological community to fulfil its potential for biodiversity conservation, and sustainably manage the populations in its care.

Given the increasing rate of environmental change that free-living animals are exposed to, there is a growing need to understand the causes and consequences of environmentally-induced phenotypic change and to what extent this phenotypic plasticity is adaptive. As well as being of fundamental biological significance, this knowledge is necessary for the development of effective conservation policies. This thesis examines variation in behavioural, morphological and physiological responses to repeated exposure to environmental stressors. In particular, I focus on early-life effects and discuss the potential consequences of developmental plasticity for later-life performance. Although negative effects of human disturbance on wild animals have been widely reported, few studies have considered the potential for effects on animals occupying burrows or cavities. Procellariiform seabirds are among the most globally-threatened avian taxa and include many species that nest underground. Human disturbance is one of the main threats they face, yet breeding colonies attract increasing numbers of tourists. The European storm petrel Hydrobates pelagicus is a small seabird, belonging to the Procellariiformes, that nests in cavities and is strictly nocturnally active at the breeding colony. The UK’s largest storm petrel colony at Mousa, Shetland, offers a novel system for investigating the potential impacts of human recreational disturbance on a cavity-dwelling animal and the capacity for environmentally-induced developmental plasticity within the remarkably slow development strategy displayed by nestlings. I show that, despite remaining out of sight, human disturbance above ground can have profound effects on cavity-dwelling animals. Nestling survival was significantly lower in areas exposed to high levels of human recreational activity, compared with those reared in areas subject to very low levels of visitor activity (Chapter 1). Furthermore, disturbed nestlings that survived to fledging displayed depressed growth rates (Chapter 2). Plasticity in developmental pathways, however, enabled nestlings to mitigate for poor growth conditions by prioritising energy allocation to structural components and extending the growth period. While such growth plasticity can be adaptive and avoid short-term costs, there may also be long-term costs associated with this strategy. Repeated exposure to stressors can give rise to chronic stress and measures of baseline glucocorticoids are widely considered to be useful for detecting stress in natural populations. Nestlings displayed no evidence for chronic stress, as measured by baseline corticosterone (the main glucocorticoid in birds), in response to repeated exposure to human recreational disturbance (Chapter 2) or investigator handling (Chapter 3). Furthermore, baseline corticosterone did not reflect the differences observed in growth trajectories between the two disturbance categories. Although it is unknown whether the induced changes in growth trajectories of high-disturbance nestlings carry costs, the lack of any effects on corticosterone levels suggests that glucocorticoids are not always an informative measure of individual state. Additional behavioural and physiological data are required to develop an integrated understanding of phenotypic responses to environmental cues. Besides immediate effects on growth and survival, it is well known that conditions experienced during early life can have profound influences on later-life performance. Telomere dynamics potentially provide a mechanistic link between the early environment and fitness outcomes. I show that environmental conditions during growth strongly influence early-life telomere dynamics of entire cohorts, and early-life telomere length is a good predictor of imminent mortality (Chapter 4). Natural variation in the natal environment can lead to marked differences in life-history traits between cohorts and telomere dynamics may be one of the mechanisms underlying cohort effects observed in nature. Unfavourable natal conditions were also associated with the occurrence of hypothermic responses in nestlings (Chapter 5). Such thermoregulatory responses may be adaptive, by facilitating survival during periods of food shortage or cold, but nonetheless could carry costs for growth and long-term fitness. An enhanced knowledge of the causes and consequences of facultative hypothermic responses can advance our understanding of the effects of environmental change. Understanding and predicting how populations will respond to environmental change, however, requires accurate estimation of population size. The ecology of Procellariiformes presents a major challenge to achieving this. Using spatially-explicit capture-recapture data from three closely-related species of storm petrel, it was shown that capture probability varies across spatial and temporal scales (Chapter 6). This quantified variation was used to inform optimal sampling strategies. The results demonstrate that spatially-explicit capture-recapture models can be effectively used to monitor vulnerable burrowing seabird populations, but require a species-specific approach. This thesis addresses key questions concerning the capacity for adaptation and response to environmental stress exposure and the mechanisms underlying individual variation in responses. I demonstrate that multidisciplinary studies of behaviour, morphology and physiology are required to develop an integrated understanding of responses to environmental stressors.

Previous research has hinted at changes in the migratory patterns of seabirds nesting in Scotland, including a decreasing number of Northern Gannets Morus bassanus wintering in the North Sea, and an increase in numbers of Northern Gannets and Great Skuas Stercorarius skua spending the winter off north-western Africa (NWA). Both species show increasing numbers of colonies in northern areas, including Norway and Russia. These seabird species move through the North Sea during autumn migration, and from there search for favourable wintering grounds mainly around Iberia, including the Atlantic coast of Portugal, the Bay of Biscay and the Gulf of Cadiz. By means of historic ring recovery data, provided by the British Trust for Ornithology, it was possible to establish that the number of records of adults of both species are increasing in recent years from NWA coasts, despite having to attend their nests in the colonies and, as a result, having limited time to migrate south. Differences were observed in ring recovery locations between years and months. The number of ring recoveries by month coincides with records from observation points along the coast of Western Europe. However, ring recovery data are limited and potentially biased. Using data loggers, it was possible to establish that both species are diurnal in habits during the entire winter period, showing noticeable differences in the times spent flying during the migration months (September-October) and during the wintering and breeding months (January and March respectively), and to confirm the increasing tendency to winter off NWA in recent years. Analyses of fishing landings, discard rates, and sea surface temperature data, show that food available to Northern Gannets and Great Skuas is increasing in NWA coasts where oceanographic conditions are stable; in contrast in the North Sea fisheries are decreasing and the sea surface is warming. Both species are apparently changing their migratory behaviour in order to face the constant changes in the abundance of food. Given the long life-span of Northern Gannets and Great Skuas, genetic changes can be ruled out of an explanation for the changes in migration behaviour, and the fact that the changes in winter distribution appear to be occurring within one generation of the birds. The winter distribution of Northern Gannets and Great Skuas may be due to an ideal free distribution over a wide range, in response to changes in the distribution of fish and the availability of discards.

Nephrops norvegicus is a mid-sized benthic decapod lobster found at depths of between 30-300 metres along the eastern Atlantic coast from Norway to Morocco, and within the Mediterranean sea. They inhabit marine muddy sediments in which they excavate burrow systems and from which they make short excursions to feed by predation and scavenging. The females of this species are known to reside within their burrows over the winter period while brooding their eggs, although their feeding behaviour over this period has not been investigated. Two aspects of the nutrition of N. norvegicus, namely nutritional status (the condition of an animal, which is maintained through a balance between energy intake and energy expenditure) and trophic dynamics (the flow of energy from exogenous inputs throughout food webs in an ecosystem) have been studied, to answer questions relating to the influence of season, sex and site on nutrition in this species. Specific questions that have been addressed include: with regard to season, is there a reduction in the nutritional status of N. norvegicus over the winter due to a decrease in primary production? With regard to sex, do females have a reduced nutritional status to males when they emerge from their winter brooding period, indicating that females go through a period of fasting over the winter? Also do females employ a filter feeding strategy over the winter? With regard to site, do N. norvegicus at two different sites on the west coast of Scotland (i.e. the Clyde Sea Area [CSA] and the North Minch [NM]) occupy different trophic levels and have different fatty acid signatures, which would indicate that their diets are made up of different prey species? A range of biochemical markers was tested to describe how N. norvegicus reacts to a period of forced starvation, and thus to determine their nutritional status. There was clear metabolic depression, indicated by an increase in the copper concentration of the hepatopancreas in both males and females. In contrast to the findings of previous studies, lipids in the hepatopancreas did decrease with starvation, however was mitigated by the metabolic depression and only became significantly lower than fed individuals after 12 weeks in males and 20 weeks in females. Lipids and water combined made up 80% of the mass of the hepatopancreas, and when the lipids decreased the proportional mass was replaced by water. However, as indicated by the hepatosomatic index (HSI), the total mass of the hepatopancreas decreased over the period of starvation. A temperature effect was also seen which influenced the amount of reserves required by the animal under these conditions. Using the results from the starvation trials, a predictive tool was developed for determining the nutritional status in N. norvegicus from the wild, and for calculating threshold values which indicate whether animals were in a starved state. These measurements and threshold values were applied to field caught animals, assessing the factors of season, sex and site. The seasonal analysis showed that there was low nutritional status in N. norvegicus during the winter of 2008-2009, whereas the nutritional status of winter 2009-2010 was not as low. The site analysis showed that N. norvegicus in the CSA, where burrow density is 0.85 m-2, were found to have a lower nutritional status than N. norvegicus in the NM, where burrow density was only 0.55 m-2. These results are consistent with the notion that in high density areas N. norvegicus has a lower nutritional status than in low density areas. Females were found to have a larger lipid store within the hepatopancreas than males, presumably to sustain reproduction. Females were also found to be metabolically depressed over the winter and spring months of early 2009. However they were not in an advanced state of starvation over this period. It is therefore concluded that over the winter months females reduce feeding, perhaps in a response to reduced mobility brought about by the brooding stage of reproduction, but do not follow different feeding strategies to males over this time. The differences of trophic level between N. norvegicus in the CSA and the NM were assessed through the use of stable isotope analysis. It was found that although the animals in the CSA had higher 15N values than the animals in the NM, the animals in the NM were actually feeding at 0.6 trophic level units higher than those in the CSA. The high 15N values in the CSA were ascribed to organic enrichment of nitrates in that area. There was no significant difference between males and females at the end of the winter period, indicating that when females are brooding their eggs they do not use different feeding strategies (e.g. filter feeding) as an alternative means of nutrition. The differences between the Fatty Acid (FA) signatures of N. norvegicus in the CSA and the NM were determined by fatty acid analysis. A clear difference was demonstrated between sites, indicative of differences in the dietary composition of the two populations, and suggestive of a greater input from pelagic food sources (either zooplankton or fish) in the NM. However, no significant difference was found in FA signatures between male and female N. norvegicus at either site or at any time of the year. Thus, consistent with the conclusions from the other monitoring methods, the FA signatures indicate that females and males had similar feeding patterns at all times of year, with regard to the type of food consumed. As well as addressing issues directly concerned with the nutrition of N. norvegicus in relation to season, sex and site, the results of these studies have a number of wider applications, including the development of optimal feeding strategies for holding lobsters under impoundment conditions for long periods, and for identifying the procedures required to assess more directly the dietary composition of N. norvegicus populations, and especially the contribution of fish to their diet.

Mosquito-borne diseases cause substantial mortality and morbidity worldwide. These impacts are widely predicted to increase as temperatures warm, since mosquito biology and disease ecology are strongly linked to temperature. However, direct evidence linking environmental change to changes in mosquito-borne disease is rare, and the ecological mechanisms that may underpin such changes are poorly understood. Environmental drivers, can have non-linear, opposing impacts on the demographic rates of different mosquito life cycle stages and on disease transmission processes. As such, model frameworks that explicitly incorporate the effects of temperature are required to predict seasonal mosquito abundance and the intensity and persistence of disease transmission under environmental fluctuations. Chapter 2 develops a variable-delay delay differential equation (DDE) model to estimate seasonal abundance of each life stage of the West Nile virus (WNV) vector mosquito species, Cx. pipiens, given temperature and photoperiod conditions experienced. The model highlights that the timing and intensity of warm periods can be more influential in shaping abundance patterns than average temperatures. Chapter 3 presents an extensive body of fieldwork, which led to a high temporal resolution seasonal abundance dataset of each life stage of Cx. pipiens. Chapter 4 challenges assumptions of the DDE model from Chapter 2 in light of the seasonal abundance data collected in Chapter 3. The importance of using appropriate, high temporal resolution input temperature datasets is displayed. Chapter 5 extends the DDE model from Chapter 4 to explicitly model WNV transmission cycles between vectors and avian hosts. The disease model predicts that the current climate in the South of England is too cold to facilitate WNV outbreaks. However, given projected warming in the UK in coming decades it is predicted that WNV infection rates in mosquitoes will be consistent with the lower range of values observed during WNV outbreaks 2080 if virus introduction coincides with warm periods. The risk of these outbreaks is predicted to increase sharply with increases in human greenhouse gas emissions.

There are an overwhelming number of biodiversity indices and indicators available for ecologists and conservationists to use when seeking to understand how biodiversity responds to human disturbance. In choosing between measures there is often an underlying assumption that if a measure works well for one group it will be equally applicable to another. In this study, I use multiple taxa to explore the performance of a wide range of alpha and beta diversity measures for studying biodiversity responses to human disturbance in tropical forest. I sampled 18 sites along a gradient of human disturbance from primary tropical forest to banana monocultures in Peru. I chose three taxonomic groups and one audio approach, which have all been suggested to be useful indicators for studying biodiversity responses to disturbance: orchid bees (n = 1783), dung beetles (n = 3787), butterflies (n = 2506) and soundscape samples (n = 6600). This allowed me to identify how these groups responded to disturbance, which diversity measures were most sensitive for detecting those changes and whether the same measures were suitable for all groups. I used Hill numbers to measure alpha diversity and explored beta diversity by looking at changes in community composition and two new measures of beta diversity: redundancy and representativeness. To see how the diversity patterns changed when taxonomic similarity was considered, I used a recently developed family of similarity-sensitive diversity measures and compared the results of these against more traditional measures. I found that the diversity indices that were best for detecting disturbance patterns varied widely among taxonomic groups. For dung beetles, species richness and community composition were the most effective measures, whereas these performed poorly for orchid bees. Abundance and redundancy were more sensitive for detecting a response to disturbance in orchid bees. Using the butterfly dataset, I show that the inclusion of species similarity completely changed the diversity patterns found across the disturbance gradient. The similarity of species present in a community is likely to be important for the preservation of evolutionary adaptability and the provision of ecosystem functions and I therefore suggest that diversity measures based on similarity will be a useful additional tool for conservation and impact assessments. Acoustic diversity showed unintuitive responses to disturbance, with higher diversity detected in more disturbed forest, and more research is required to assess the performance of different acoustic indices in rainforest environments. Overall, my results demonstrate the importance of choosing diversity indices carefully to suit the taxa being studied to avoid missing important ecological responses, including a consideration of species similarity. I recommend that, where possible, multiple diversity indices and taxonomic groups should be used to reduce this risk and provide a comprehensive understanding of ecosystem patterns in response to environmental change.

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Tree frogs have evolved specialised toe pads which allow them to efficiently climb vertical surfaces. The toe pad stick by using ‘wet adhesion’ – a combination of forces produced by a thin layer of fluid between the pad and the surface which provide temporary adhesion to allow quick attachment and detachment for climbing. Most studies on tree frogs have been based on their adhesive capabilities on surfaces which are flat, clean and dry (usually glass). However, climbing tree frogs in the wild will come across a variety of surfaces which could affect their adhesive abilities. This PhD investigated whether tree frog adhesion is affected by various ‘challenging’ surfaces, which reflect conditions that tree frogs may encounter whilst climbing. These include rough surfaces, wet conditions, surfaces with loose particulate and hydrophobic surfaces. Experiments were predominantly conducted using a force transducer to measure adhesive and frictional forces of single toe pads, as well as whole animal attachment experiments involving a rotating tilting board. The toe pads of tree frogs were shown to possess a self-cleaning mechanism, whereby the pads will remove contaminants (and subsequently recover adhesive forces) through repeated use, thanks to shear movements of the pad and the presence of pad fluid which aids contaminant deposition. To investigate how torrent frogs (frogs which inhabit waterfalls) can adhere to rough and flooded surfaces, the performance of torrent frogs species Staurois guttatus was compared to a tree frog species (Rhacophorus pardalis). Torrent frogs could produce higher adhesive forces than tree frogs with their toe pads, and possess a specialised toe pad morphology (directional fluid channels on the pad periphery) which may contribute to better performance in flooded conditions. Torrent frogs utilise large areas of ventral skin to stay attached on overhanging surfaces, while tree frogs display a reduction in contact area resulting in a failure to stay attached. This combination of ability and behaviour will help torrent frogs to stay attached on the rough and flooded surfaces that make up their waterfall habitat. On rough surfaces, tree frogs showed improved (compared to smooth surface performance) performance on smaller scale roughness (asperity size <10 µm), and poorer performance on the larger scale roughnesses tested (30 – 425 µm). Interference reflection microscopy (IRM) revealed that larger asperities result in pad fluid being unable to fill the larger gaps of such surfaces, which was confirmed by adding water to rough surfaces to improve attachment performance. The soft pad does however aid in conforming to some rough surfaces, which could account for the better performance on the smaller scale roughness. Many plant surfaces exhibit hydrophobic properties, and so the adhesive performance of tree frogs on hydrophobic surfaces was compared to that on hydrophilic surfaces. It was found that the toe pads could produce similar adhesive and frictional forces on both surfaces. The pad fluids contact angles were then measured on hydrophobic surfaces using IRM, where droplets of pad fluid formed lower contact angles (and are therefore exhibiting higher wettability) than water. Though the exact composition of pad fluid is unknown, some form of surfactant must be present which aids wetting of surfaces (either a surface modification or detergent present in the fluid) to allow wet adhesion to occur - goniometer experiments of water on dried footprints on hydrophobic surfaces confirmed this. The ability to stick in a variety of conditions could provide inspiration for ‘smart’ adhesives, which mimic the adaptable adhesion of tree frog toe pads.

Microplastic pollution has been identified as an ever increasing proportion of marine litter. Despite an increase in microplastic awareness over the last decade, it represents an as yet unquantified threat to the marine environment. The relatively few studies that monitor its distribution and impact have illustrated a range of worrying effects on marine habitats and communities. The Clyde Sea Area (CSA) is subject to many sources of terrestrial and maritime plastic input. The use of plastics in recreational and commercial vessels throughout the CSA is believed to result in large levels of microplastic fibres, which have previously been seen to be ingested by a range of marine organisms. In a study of the breakdown of commonly used polymers in benthic environments, it was found that ropes of 10 mm diameter in sub-tidal conditions release between 0.086 and 0.422g of microfibers per meter per month in the early stages of degradation. This rate would be expected to increase over subsequent months, releasing substantial amounts of fibres into the CSA environment. In addition to the presence of numerous sources of microplastics, the CSA is relatively enclosed, and may accumulate high levels of debris as a result. Monthly sampling of the water and sediment in the CSA revealed contamination similar to that observed in other near-shore environments. Thus, it is expected that the potential threat to organisms in other areas will be similar to that observed in the CSA. One organism known to take up microplastics is the Norway lobster, Nephrops norvegicus, the target of the main fishery in the CSA. In this work we examined the levels of microplastic in the gut of N. norvegicus from the Scottish waters. Examination of individuals from the CSA revealed both a high occurrence and high accumulation of microplastic. This was found to be much greater than in N. norvegicus sampled from more remote Scottish waters. As a result, N. norvegicus from the CSA are most likely to suffer from the negative impacts associated with microplastic ingestion than those in offshore or in areas of low anthropogenic activity. In order to determine the potential impacts of microplastic ingestion on N. norvegicus, we first examined the mechanism by which N. norvegicus retain and egest microplastic. The position of microplastic aggregations in the foregut indicates that the gastric mill is the main obstacle to microplastic egestion. Inducing moult in microplastic-fed individuals demonstrated that expulsion of the gut lining during ecdysis enables N. norvegicus to reduce their plastic load, limiting plastic aggregation to the length of a single moult-cycle. In an 8 month controlled-feeding experiment retained plastic was seen to have a range of impacts on N. norvegicus. Feeding rate and body mass was seen to decrease in plastic loaded N. norvegicus, and a reduction was observed in a number of indicators of nutritional state. The results presented in this thesis have a number of implications to the CSA and wider marine environment. The similarity in the level of microplastic observed in the CSA to that of other studies of inshore waters indicates the potential for high microplastic uptake by crustaceans in those areas. The high variability in observed microplastic abundance suggests that small-scale monitoring is unsuitable for monitoring marine microplastic debris, and that use of an indicator species may provide a more reliable method of monitoring that is not subject to small-scale heterogeneity in distribution. The seasonal retention of microplastic by N. norvegicus indicates that crustaceans may provide a suitable indicator of local contamination. However, in the CSA, the high level of fibre aggregation and observed impacts of prolonged retention indicate that microplastic may be causing further pressure on an already exploited resource, reducing the stability of the valuable N. norvegicus population.