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Cognition is defined as the mechanisms that allow animals process, store and act on information. These mechanisms mediate behaviour and how animals interact with their environment. Yet not all individuals behave the same. While much of this variation may be attributed to differences in cognitive abilities among individuals, our understanding of why individuals vary in cognitive performance is limited. Examining the factors that drive individual variation in cognition is fundamental for understanding its adaptive significance, particularly when factors that determine how well an individual performs on a task may or may not be heritable. The aim of my thesis was to investigate how a range of distinct and understudied proximate factors shape individual variation in cognitive performance in great tits (Parus major) across different problem-solving and cognitive tasks. Using a multi-access problem-solving device to test sequential innovative problem-solving performance, I discovered that food-related motivation drives innovativeness and likelihood of solving, while previous experience drives accuracy and that individuals show repeatable differences in their accuracy and ability to solve. Between individual differences in problem solving performance were explained entirely by accuracy, motivation, and positive feedback loop caused by previous experience. Food is fundamental for survival and reproduction and food quality impacts cognition and behaviour. In my third chapter I found that diet correlated with problem-solving success, while personality correlated with the proportion of arachidonic acid, an ω-6 polyunsaturated fatty acid that is crucial for normal development and functioning of the brain. Great tits experience varying levels of predation risk as they forage in complex and fluctuating environments, but little is known about the effect of predation risk on learning and cognition in the context of foraging. In Chapter 4 I show that under high predation, birds demonstrated greater behavioural flexibility compared to those under low predation risk and displayed worse spatial memory for their reward location than those under medium or low predation risk. In Chapter 5 I take the spatio-temporal learning paradigm into the wild, and explore the effects of species, age and distance between feeders on discrimination and temporal learning. I show for the first time in the wild that both great tits and blue tits are capable of temporal and reversal temporal learning, but performance in any of these metrics were not correlated among individuals. Shorter distances between feeders resulted in faster discrimination learning performance, but had no effect on temporal learning. My thesis demonstrates how a variety of underexplored proximate factors explain individual variation in cognitive performance, emphasising the challenges faced when measuring cognition generally but especially in the wild.

The microbial community in the gut is influenced by environmental factors, especially diet, which can moderate host behaviour through the microbiome-gut-brain axis. However, the ecological relevance of microbiome-mediated behavioural plasticity in wild animals is largely unexplored. We presented wild-caught great tits ( Parus major ) with a problem-solving task and showed that performance was weakly associated with natural variation in the gut microbiome. We then manipulated the gut microbiome by feeding birds one of two diets that differed in their relative levels of fat, protein and fibre content: an insect only diet (low content), or a seed, nut and beef suet diet (high content). We presented these same individuals with the same problem solving task after the dietary manipulation to test whether any observed dietary-induced gut microbiome alterations predicted their subsequent problem solving performance. Microbial communities changed substantially and were less diverse among individuals given the insect but not the seed diet. Individuals were less likely to problem-solve after being given the insect diet, and problem-solving performance was positively associated with microbiome diversity. The same microbiota metrics that were altered as a consequence of diet were also those that correlated with variation in problem solving performance. Although the effect on behaviour may not be solely or directly a consequence of the gut microbiota manipulation, this nevertheless represents the first evidence for an association between behaviour, diet and the gut microbiome in a wild animal system, and points to an overlooked but potentially crucial mechanism underlying individual behavioural plasticity in evolutionary ecology.

Research into proximate and ultimate mechanisms of individual cognitive variation in animal populations is a rapidly growing field that incorporates physiological, behavioural and evolutionary investigations. Recent studies in humans and lab animals have shown that the enteric microbial community plays a central role in brain development and functioning. The ‘gut-brain axis’ represents a multi-directional signalling system that encompasses neurological, immunological and hormonal pathways. In particular it is tightly linked with the hypothalamic-pituitary-adrenal axis (HPA), a system that regulates stress hormone release, and influences brain development and function. Experimental examination of the microbiome through manipulation of diet, infection, stress and exercise, suggests direct effects on cognition, including learning and memory. However, our understanding of these processes in natural populations is extremely limited. Here we outline how recent advances in predominantly laboratory-based microbiome research can be applied to understanding individual differences in cognition. Experimental manipulation of the microbiome across natal and adult environments will help to unravel the interplay between cognitive variation and the gut microbial community. Focus on individual variation in the gut microbiome and cognition in natural populations will reveal new insight into the environmental and evolutionary constraints that drive individual cognitive variation.

East African savannas are persistent socio-ecological systems undergoing unprecedented change. This dissertation focuses on the emerging agro-pastoral system of Maasai herders in the savanna lands adjacent to Tanzania’s Tarangire National Park. As pastoralists adopt cultivation, the relationship between humans and the land is changed. The new dynamics threaten the resilience of savanna systems. I examine three aspects of the human ecology of Maasai subsistence: changes in territory and political ecology, changes to the local common property system resulting from territorial compression, and how Maasai are responding to the production constraints of cultivation. I employed ethnography, social surveys, soil surveys and livestock demography to take a political ecology approach to investigating human-environment relations. Maasai territory is being fragmented by forces from within and without Maasai society. Poverty is increasing, due to market integration, high cattle mortality and population growth. Despite this, the adoption of cultivation cannot be explained by poverty alone. Poverty interacts with land tenure insecurity and with environmental stochasticity to create conditions conducive to the adoption of cultivation. Subdivision fragments the pastures which support pastoralism, reducing mobility and flexibility critical to dryland ecosystems. A village zoning plan has led to the emergence of a new common property regime that appears sufficient for current grazing and cultivation needs yet the historical pattern of land allocation means some villagers have greater access to protected pastures and water than others. Rich soils from abandoned kraals are also unequally distributed across the landscape. Pastoralists must negotiate limited cultivation experience, wildlife raids and labor shortages to integrate pastoral and agricultural production. Several trends suggest negative repercussions for future resilience of the socioecological system. Unequal resource distribution among land allocations, the history of interactions between stakeholder groups, and land use patterns that inadvertently concentrate resources among a few households are decreasing the flexibility demanded by semi-arid systems. To reduce the negative effects of cultivation, efforts should focus on improving yields on small plots, supporting livestock husbandry and integrating local residents and wildlife interests to build a resilient future.

The microbial community in the gut is influenced by environmental factors, especially diet, which can moderate host behaviour through the microbiome-gut-brain axis. However, the ecological relevance of microbiome-mediated behavioural plasticity in wild animals is unknown. We presented wild-caught great tits (Parus major) with a problem-solving task and showed that performance was weakly associated with variation in the gut microbiome. We then manipulated the gut microbiome by feeding birds one of two diets that differed in their relative levels of fat, protein and fibre content: an insect diet (low content), or a seed diet (high content). Microbial communities were less diverse among individuals given the insect compared to those on the seed diet. Individuals were less likely to problem-solve after being given the insect diet, and the same microbiota metrics that were altered as a consequence of diet were also those that correlated with variation in problem solving performance. Although the effect on problem-solving behaviour could have been caused by motivational or nutritional differences between our treatments, our results nevertheless raise the possibility that dietary induced changes in the gut microbiota could be an important mechanism underlying individual behavioural plasticity in wild populations.

The microbial community in the gut is influenced by environmental factors, especially diet, which can moderate host behaviour through the microbiome-gut-brain axis. However, the ecological relevance of microbiome-mediated behavioural plasticity in wild animals is unknown. We presented wild-caught great tits (Parus major) with a problem-solving task and showed that performance was weakly associated with variation in the gut microbiome. We then manipulated the gut microbiome by feeding birds one of two diets that differed in their relative levels of fat, protein and fibre content: an insect diet (low content), or a seed diet (high content). Microbial communities were less diverse among individuals given the insect compared to those on the seed diet. Individuals were less likely to problem-solve after being given the insect diet, and the same microbiota metrics that were altered as a consequence of diet were also those that correlated with variation in problem solving performance. Although the effect on problem-solving behaviour could have been caused by motivational or nutritional differences between our treatments, our results nevertheless raise the possibility that dietary induced changes in the gut microbiota could be an important mechanism underlying individual behavioural plasticity in wild populations.