Individual niche variation is increasingly being demonstrated in animal populations in a wide variety of species and taxa. Niche variation among individuals has important implications for the ecology, evolution and management of animal populations and is a subject of increasing interest. However, despite its widespread occurrence the causes and consequences of individual niche variation remain poorly understood. In this thesis I use the European badger (Meles meles), a well studied species of high ecological interest, as a model system to investigate individual niche variation. In order to achieve this I combine information on individual foraging niches derived via stable isotope analysis (SIA) of badger vibrissae with detailed life history and ecological data from a long-term study population to investigate the incidence, cause and consequence of individual niche variation within badger social groups. First I use the biomarker Rhodamine B to investigate vibrissae growth rates and patterns in badgers and demonstrate that the isotopic composition of a single vibrissa likely reflects diet over several months (Chapter 2). Next I explore the use of SIA as a tool to investigate badger diet, by comparing isotopic patterns to seasonal changes in diet measured using faecal analysis (Chapter 3). My results provide validation that SIA is powerful tool for investigating foraging variation in this species, and suggest that within badger populations substantial dietary variation may occur among individuals. Further investigation of isotopic variation Indicates that individuals within social groups differ markedly and consistently in their isotopic signature, independent of age and sex effects and that in some instances these differences are remarkably consistent across year (Chapter 4).This suggesting long term individual specialisation (Chapter 4). I find that the degree of this individual specialisation, and the relationship between specialisation and body condition is influenced by competition for resources (Chapter 5). Social groups with higher levels of competition exhibit greater specialisation and specialised individuals within these highly competitive environments are in better condition. Finally, I discuss the implications of these results for individual niche variation, for the application of SIA to study this behaviour and for badger ecology generally (Chapter 6). I also outline future directions for further research.

This study applies a life history approach to analyzing the identities of 52 Maya individuals who lived between 2000 BC and AD 900 in and around the city of Holmul, within the Petén region of Guatemala. Primary goals were to: (1) identify migrant and local individuals within the urban population; (2) determine 87Sr/86Sr isotope ratio signatures for the sites of Holmul, Cival, La Sufricaya, K’o, and Hamontun; (3) compile osteobiographies, personal life histories revealed through skeletal remains, of the individuals in the sample; and (4) evaluate evidence bearing on the identities of inhabitants of the Holmul region and how they were represented within economic, political, and cultural landscapes of the ancient Maya. This work demonstrates how bioarchaeologists can implement osteobiographical analyses to advance the understanding of multifaceted social identities and individual experiences of life and death. By integrating osteological study, stable isotope analysis, and consideration of mortuary context, material culture, inscriptions, and monumental architecture, the individual, rather than the population, becomes the focus. This aggregate approach allows for an in-depth consideration of human remains as former social beings with complex identities. The findings of this research suggest that most elite inhabitants in this ancient Maya city were local to the Holmul region, with the few outliers having originated from elsewhere in the Maya lowlands. This conclusion aligns with Maya elite ideologies of establishing lineages and reinforcing power through ancestor veneration. The local 87Sr/86Sr ratio signature of the Holmul region is comparable to other archaeological sites in the southern Maya lowlands. The osteobiographies reveal life histories, which personalize prior interpretations that considered the population only as an aggregate. This project also elucidates identities of sacrificed children, elite/royal women, and the local Holmul elite. Results of the study support the use of the isotopic analysis of human remains as an essential tool for approaching complex archaeological questions and evaluating hypotheses previously addressed primarily using architectural, iconographic, and artifactual evidence. Further, this study demonstrates the benefit of the isotopic analysis of dental enamel, especially in the Maya region and other environments characterized by difficult excavation conditions and the poor preservation of human remains.

Food webs in aquatic ecosystems can be dramatically altered by invasive species. Quagga mussels are prevalent invaders that compete with existing species and disrupt nutrient cycling. In 2012, the Quagga Mussel (Dreissena rostriformus bugensis) was introduced into Lake Powell and is expected to move throughout the reservoir in the near future. Stable isotope analysis is a powerful tool for characterizing food webs and trophic interactions. To predict the long-term effects of Quagga Mussels, we used stable isotope analysis of primary producers, primary consumers, prey fish species, and predator fish species in Lake Powell to determine food web structure. Quagga Mussel are positioned to disrupt the pelagic arm of the food web by interfering with the link between phytoplankton and herbivorous zooplankton. This will likely have negative impacts on pelagic fish such as striped bass (Morone saxatilis) and threadfin shad (Dorosoma petenense). Quagga Mussel may also boost benthic productivity in the littoral zone by diverting nutrients from the water column to the benthos. This may have positive impacts on littoral fishes such as largemouth bass (Micropterus salmoides), smallmouth bass (Micropterus dolomieu), bluegill (Lepomis macrochirus), and green sunfish (Lepomis cyanellus).

Bark beetle outbreaks are becoming more intense and severe when coupled with the effects of climate change. Engelmann spruce (Picea engelmannii) is one such species facing large-scale, epidemic spruce beetle outbreaks. Large-scale disturbances, such as beetle outbreaks, have major consequences for the future success of the ecosystem, thus highlighting the importance of understanding what promotes amplified outbreaks as well as their effects on future seedling establishment. Our research focused on two parts of a large-scale beetle outbreak: the mortality of spruce trees and the subsequent regeneration of seedlings. Our first study examined the timing of spruce mortality during an outbreak in order to identify the extent to which drought promotes host species mortality. Trees that are drought stressed have less resources to defend themselves against beetle attacks, however, the warmer temperatures associated with droughts also promote a more rapid population expansion of spruce beetles. We were specifically interested in determining the contribution that host drought stress plays during an epidemic outbreak. Our second study analyzed the patterns of regenerating seedlings with an aim to identify changes associated with the outbreak. Specifically, we were interested in how an epidemic outbreak changes the drivers of seedling establishment.

This study conducts a multi-isotopic bioarchaeological analysis of the Avondale Burial Place (McArthur Cemetery), a recently discovered Emancipation-era African American cemetery near Macon, GA. Stable isotopic analyses were performed on available dental remains in order to reconstruct the diet and demography of the individuals buried at McArthur Cemetery. Specifically, δ18O and δ13C were characterized in tooth enamel and examined in tandem with collaborative osteological and mortuary analyses to reconstruct early-life diet and residential origin. The results suggest that members of the Avondale community buried in McArthur did not experience significant mobility, but rather resided in the area for most of their lives. Overall, these results greatly contribute to the genealogical research of McArthur Cemetery’s descendants as well as the fragmented history of the South by exploring whether the individuals in this community took part in the Great Migration following the Civil War.

The green turtle, Chelonia mydas, is a circumglobal species that exhibits several important developmental or ontogenetic shifts throughout its life history. The first major shift occurs when juvenile turtles migrate from pelagic habitat, where they forage as omnivores, to coastal neritic habitat, where they become primarily herbivores, foraging on algae and seagrass. Anecdotal evidence and gut-content analyses suggest that juvenile green turtles in south Texas bays, such as the lower Laguna Madre and Aransas Bay, undergo an additional ontogenetic shift during this important life history stage. Evidence from stable isotope analysis (SIA) of scute tissues of green turtles from Texas' lower Laguna Madre and Aransas Bay supports an intermediate stage between this species' shift from pelagic waters to seagrass beds in neritic waters; this additional shift comprises an initial recruitment of post-pelagic juveniles to jetty habitat located on the channel passes Gulf-ward of adjacent bays before subsequently recruiting to seagrass beds in these bays. Examination of stable carbon ([delta]¹³C) and nitrogen ([delta]¹⁵N) isotopes in microlayers of scute tissue from several size classes of green turtles from the lower Laguna Madre and Aransas Bay was used to confirm the occurrence of two ontogenetic shifts. Smaller green turtles (< 35 cm SCL) exhibited more depleted [delta]¹³C signatures and more enriched [delta]¹⁵N signatures, consistent with jetty habitat, compared to those of larger counterparts (> 45 cm SCL) that displayed enriched [delta]¹³C signatures and depleted ¹⁵N signatures, consistent with seagrass habitat. Changes in the isotopic composition between these size classes indicate distinct shifts in diet. Post-pelagic juveniles first recruit to jetty habitat and forage primarily on algae, before subsequently shifting to seagrass beds and foraging primarily on seagrass. These findings indicate the use of a characteristic sequence of distinct habitats by multiple life history stages of green turtles in Texas bays, a conclusion with broad management implications for this endangered species.

During the Medieval period of Denmark, economic and trade relations grew inter-regionally, with culture, ideas, and products being transferred on a more regular basis through the 11th to 13th centuries. Beginning around 1050 AD and lasting until AD 1536, the country faced drastic climatic changes, shifting economic and agricultural practices, and disease outbreaks (most notably the bubonic plague). The current study seeks to investigate mobility during this period from two medieval cemeteries around Horsens, Denmark: the rural site of Sejet and the urban site of Ole Wormsgade, both used throughout the 12th to 16th centuries. A previous isotopic analysis using oxygen indicated that some movement was seen at these sites, with three individuals identified as potential migrants from other Scandinavian regions. This study compares the existing oxygen isotopic data with variations in 87Sr/86Sr ratios from these samples. Such ratios represent local bedrock baselines of strontium, which are slightly different between eastern and western Denmark. ICP-MS was used to measure 87Sr/86Sr ratios, and results are interpreted in the context of climatic changes and shifting socioeconomic practices. The results suggest that longer-distance movements into Denmark were seen during the Early Medieval Period. The potential migrant identified in this research points to movement towards the rural population at Sejet, and could possibly connect this migration with marriage rules influencing immigration at the time. This research demonstrates that movement during the medieval period of Denmark was a complex, dynamic, and multilinear process during a time of increasing urbanization. / October 2015

Understanding wolf (Canis lupus) food habits provides critical information for boreal woodland caribou (Rangifer tarandus caribou; forest-dwelling ecotype) recovery strategies. By incorporating the stable isotope ratios of different caribou ecotypes into a stable isotope mixing model, I determined the relative importance of boreal woodland caribou in the summer diet of wolves in northern Manitoba, Canada. Boreal woodland caribou were primary summer prey for wolves collected in winter in registered trapline (RTL) districts where these caribou are considered rare, suggesting migratory behaviour in some wolves. Moose were primary prey in other RTL districts, followed by boreal woodland caribou, with beaver providing important contributions. Recovery strategies for woodland caribou should investigate annual wolf, caribou, and moose movement in the region to complement these findings and gain a better insight into this complex ecosystem.

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Understanding wolf (Canis lupus) food habits provides critical information for boreal woodland caribou (Rangifer tarandus caribou; forest-dwelling ecotype) recovery strategies. By incorporating the stable isotope ratios of different caribou ecotypes into a stable isotope mixing model, I determined the relative importance of boreal woodland caribou in the summer diet of wolves in northern Manitoba, Canada. Boreal woodland caribou were primary summer prey for wolves collected in winter in registered trapline (RTL) districts where these caribou are considered rare, suggesting migratory behaviour in some wolves. Moose were primary prey in other RTL districts, followed by boreal woodland caribou, with beaver providing important contributions. Recovery strategies for woodland caribou should investigate annual wolf, caribou, and moose movement in the region to complement these findings and gain a better insight into this complex ecosystem.