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This thesis investigated whether a food-storing mammal, the eastern grey squirrel (Sciurus carolinensis), uses social cognitive skills in relation to its caching behaviour and explored whether social cognition really is a specialized adaptation that differs from other cognition by examining how social and non-social learning differ. The influence of social factors on the natural caching behaviour of wild squirrels was studied in the field and the effects of conspecific presence on specific aspects of caching behaviour (learning, memory and recovery) were investigated by testing captive squirrels in the laboratory on social learning and one-trial learning tasks. The squirrels were found to be able to learn by observing a conspecific and learned to make a logical choice more readily than an illogical one. They showed no such bias in a comparable non-social task. They responded flexibly to the presence of conspecifics both in the wild and in the laboratory but the results can be interpreted in terms of responses to observable cues rather than as evidence of higher cognitive skills. In total, this thesis suggests that squirrels use unsophisticated social cognitive strategies in relation to their caching but, the difference found in learning under social and non-social conditions suggests that, although not a highly social species, grey squirrels are particularly prepared to form certain associations with social cues. This offers some support to the theory that factors other than social complexity may lead to the development of the ability to process social information highly effectively.

This thesis examines how Eastern grey squirrels, Sciurus carolinensis, modify their foraging and hoarding behaviour in relation to different risks, particularly those which involve a trade-off between securing food resources and avoiding a negative outcome with a competitor. While foraging for food to eat and hoard, squirrels must compete with conspecifics and heterospecifics for access to resources, and they must ensure the safety of their food hoards from onlookers or opportunistic pilferers. While engaging in these behaviours in the most efficient way, they must also avoid being predated upon. Five studies were conducted to further understanding of grey squirrel foraging, hoarding and pilferage behaviours, and how they are affected by different risk factors. The data in this thesis provide experimental evidence that grey squirrels respond directly to conspecific presence as a cue of pilferage risk and adjust their behaviour in ways that may help to reduce cache theft. The data also support the view that conspecific and heterospecific competitors pose risks to foraging and caching, with squirrels modifying their behaviour in ways that serve to avoid negative competitive interactions. Predation risk was found to be particularly disruptive to foraging behaviour, and it also had a seasonal effect upon pilferage rates of experimenter-made caches. A variety of strategies that squirrels might use to pilfer caches were investigated, however, the data did not provide a clear indication of pilferage strategy used by squirrels; they did not seem to use observational spatial memory, and they did not simply pilfer in profitable foraging locations. This thesis raises questions about the mechanisms grey squirrels use to assess pilferage risk and how they engage in pilferage in comparison to other caching species; the studies conducted illustrate different methods that future research could use to investigate food hoarding and pilfering behaviour in wild and captive squirrels.

Successful management of an invasive species requires in depth knowledge of the invader, the invaded ecosystem, and their interactions. The complexity of the species-system interactions can be reduced and represented in ecological models for better comprehension. In this study, a spatially explicit population model was created using the RAMAS software package to simulate the past and future invasion dynamics of the eastern grey squirrel (Sciurus carolinensis) in the fragmented habitat in case study areas in Ireland. This invasive squirrel species causes economic damage by bark stripping forest crops and is associated with the decline of its native congener (S. vulgaris). Three combinations of demographic and dispersal parameters, which best matched the distribution of the species shortly after introduction, were used to simulate invasion dynamics. Future population expansion was modeled under scenarios of no control and two different management strategies: fatal culls and immunocontraceptive vaccination programmes. In the absence of control, the grey squirrel range is predicted to expand to the south and southwest of Ireland endangering internationally important habitats, vulnerable forest crops, and the native red squirrel. The model revealed that region-wide intensive and coordinated culls would have the greatest impact on grey squirrel populations. Control strategies consisting solely of immunocontraceptive vaccines, often preferred by public interest groups, are predicted to be less effective. Complete eradication of the grey squirrel from Ireland is not economically feasible and strategic evidence-based management is required to limit further range expansion. Ecological models can be used to choose between informed management strategies based on predicted outcomes.

The red squirrel (Sciurus vulgaris) is native to Eurasia, but in the UK its survival is being threatened by the non-native grey squirrel (Sciurus carolinensis). Since its introduction to the UK from the USA the grey squirrel has increased its range at the expense of the red squirrel. Although competition for resources clearly plays a role in this replacement, an infectious viral disease, caused by squirrelpox virus (SQPV) and hosted apparently asymptomatically by the grey squirrels, has now been recognised as a major contributing factor. Little is known about the pathogenesis of infection in grey squirrels in comparison to red squirrels, but understanding this is essential to determining how the virus spreads within and between the red and grey squirrels. The aims of this thesis were to investigate the course of SQPV infection in red and grey squirrels and possible routes of virus transmission. Specifically, for the first time, a novel Real Time PCR (qPCR) assay and immunohistochemistry were used to investigate the presence of SQPV in various tissues from naturally infected red squirrels and experimentally infected grey squirrels. In diseased red squirrels SQPV DNA was found in several tissues with the highest amounts being found in skin samples. This reflects the multiple lesions that were easily visible on the red squirrel carcasses. There was no indication of systemic disease although the viral DNA was detected, at lower levels, in other internal organs. Grey squirrels were experimentally infected with SQPV isolated from naturally-infected red squirrels with fatal clinical disease. In contrast to SQPV-infected red squirrels no clinical lesions, other than mild scab formation at the site of inoculation, were found in the grey squirrels post-infection. No gross pathological changes indicative of systemic infection were observed and these findings were reflected in the qPCR and histopathology results. Viral DNA was only detected by qPCR in samples from the site of inoculation (scarified skin) and at lower concentrations in other skin tissues such as digital and eyelid skin. In addition, histopathology and immunohistochemistry examination revealed evidence of infection characterized by ballooning degeneration of keratinocytes, and acanthosis and spongiosis of the epidermis. These skin lesions were self limiting and minor compared to the infected red squirrel skin samples. The molecular variation in the virus isolated over time from different parts of the UK was also investigated. Seven SQPV isolates (4 from Scotland and 3 from England) were tested and results indicated that there are no significant changes in the amino acid sequence of any of the three genes examined apart from one amino acid change (one base change) in one gene. All Scottish isolates examined showed this change in comparison to English isolates. The results in this thesis show that there is a mild pathology associated with SQPV infection in grey squirrels. Scabs form at the site of infection but are less proliferative than in infected red squirrels, though they may still serve to contaminate the environment with virus leading to further outbreaks of disease. In contrast it seems likely that the proliferative lesions suffered by red squirrels and the greater amounts of virus that this leads to are likely to be more significant to the epidemiology of disease in localised outbreaks.

The grey squirrel (Sciurus carolinensis) has wildtype and melanic (dark) colour morphs. Melanism is associated with variations in the melanocortin-1 receptor (MC1R) gene in a number of species. The MC1R protein is a G-protein coupled receptor, predominantly expressed in melanocytes, where it is a key regulator of pigment production. To investigate the genetic and molecular basis of melanism, the MC1R genes of the wildtype and melanic grey squirrel were sequenced. The wildtype (MC1R-wt) and melanic (MC1RΔ24) variants of the MC1R were then functionally characterised in a cell-based assay. The MC1R gene of the grey squirrel was found to have a 24 base pair (bp) deletion associated with melanism. The MC1R is typically activated by its agonist, the alpha-melanocyte stimulating hormone (α-MSH), which stimulates dark pigment production by raising intracellular cAMP levels. Conversely, the MC1R is inactivated by its inverse agonist, the agouti signalling protein (ASIP), which stops dark pigment production by lowering intracellular cAMP levels. To investigate the effects that the 24 bp deletion have on receptor function, MC1R-wt and MC1RΔ24 genes were transfected into HEK293 cells. Cells expressing either MC1R-wt or MC1RΔ24 were stimulated with α-MSH or ASIP and intracellular cAMP levels were measured. Unstimulated MC1RΔ24 cells showed higher basal activity than the MC1R-wt cells. Both MC1R-wt and MC1RΔ24 cells responded to α-MSH with a concentration-dependent increase in intracellular cAMP. However, while the MC1Rwt cells responded to ASIP with a concentration-dependent decrease in intracellular cAMP, MC1RΔ24 cells responded with an increase in cAMP. Melanism in the grey squirrel is associated with a 24 bp deletion in the MC1R. Cells expressing MC1RΔ24 have higher basal levels of cAMP than MC1R-wt cells. ASIP acts as an inverse agonist to the MC1R-wt but as an agonist to the MC1RΔ24. As MC1RΔ24 cells have higher levels of cAMP, and higher levels of cAMP lead to dark pigment production, the 24 bp deletion is the likely molecular cause of melanism in the grey squirrel.

The surveillance and control of introduced species has become an increasingly important, yet often controversial, form of environmental management. I investigate why and how introduced species management is initiated; whether, why and how it is contested; and what relations and outcomes emerge ‘in practice’. I examine how introduced species management is being done in the United Kingdom through detailed social scientific analyses of the processes, practices, and disputes involved in a series of management case studies. First, I demonstrate how some established approaches to the design and delivery of management initiatives can render them conflict-prone, ineffective and potentially unjust. Then, examining a disputesurrounding a state-initiated eradication of monk parakeets (Myiopsitta monachus), I show why and how ‘parakeet protectors’ opposed the initiative. I identify the significance of divergent evaluations of the risks posed by introduced wildlife; personal and community attachments between people and parakeets; and campaigners’ dissatisfaction with central government’s approach to the issue. By following the story of an unauthorised (re)introduction of Eurasian beavers (Castor fiber) to England, I show how adiverse collective has, at least temporarily, been united and empowered by a shared understanding of beavers as ‘belonging’ in the UK. I consider how nonhuman citizenship is socio-politically negotiated, and how the beavers have become enrolled in a ‘wild experiment’. Finally, through a multi- sited study of grey squirrel (Sciuruscarolinensis) control initiatives, I find important variations in management practitioners’ approaches to killing squirrels, and identify several ‘modes of killing’ that comprise different primary motivations, moral principles, ultimate aims, and practical methods. I identify multiple ways in which people respond and relate to introduced wildlife, and demonstrate how this multiplicity produces both socio-political tensions and accords. Furthermore, throughout this thesis I make a series of propositions for re-configuring the management of introduced species in ways that explicitly incorporate inclusive, constructive, and context-appropriate socio-political deliberations into its design and implementation.