RSS 1.0Theses
This collection contains the Doctoral and Masters by Research theses produced within the department.
This collection is licenced under a Creative Commons licence. The collection may be reproduced for non-commercial use and without modification, providing that copyright is acknowledged.
Recent Submissions
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Population dynamics of the Rodrigues fruit bat (Pteropus rodricensis): An analysis of long-term island wide bat count dataThe Rodrigues fruit bat (Pteropus rodricensis) is an insular Old-World fruit bat endemic to the Island of Rodrigues. The Mauritian Wildlife Foundation implemented a population monitoring program in 1974 and an estimate of less than 80 individuals was recorded in 1979. Following conservation efforts of reforestation of native flora, the population has experienced a steady increase, subject to decreases in numbers after severe cyclones. A standardized methodology was applied in 2016 creating a dataset suitable for population modelling and statistical analysis. The most recent population census (2022) revealed that the population has remained stable at around 20,000 individuals for the last 5 years. This study uses Generalised Linear Mixed Models (GLMMs) to analyse 17 years of population monitoring data in order to identify the climatic factors potentially driving the population trend. We identified that the strongest factors driving changes in the population numbers were linked to resource availability. Most notable were annual precipitation levels, which had a positive relationship with population size (β=1.745, P<0.001), and cyclones, specifically relating to cyclonic strength, which was negatively related with the population size (β=-0.205, P<0.0001). This study also critically analyses the population count methodology and offers recommendations and suggestions for future research to be conducted on the species.
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Elasmobranchs and the Inshore Reefs of Southern MozambiqueThe coastal waters off southern Mozambique host a diverse community of elasmobranchs. The complexity of studying sharks and rays in remote locations means that limited research attention focusses on its marine environment. As the region is famed for its coastal reefs and the diversity of its elasmobranch species, a novel opportunity was presented to study elasmobranch species that have become rare in most other regions. This thesis aims to investigate the relationship between elasmobranch species and coastal reef habitat in southern Mozambique. This aim is addressed by investigating the frequency with which elasmobranch species visit reef systems and by comparing this with the environmental and biological conditions on the reefs. A reef camera trap was deployed 60 times on four reefs to record elasmobranch visits and to estimate the relative abundance of each reef’s fish and coral communities. SCUBA-based transects (n = 738) were conducted on 18 reefs in the same region to count elasmobranchs and measure environmental parameters that influence the presence of elasmobranchs on the reefs. Two large Carcharhinus sharks were observed in low numbers during video and SCUBA observations. To monitor their interactions with regional reefs, 18 acoustic tags were fitted to Carcharhinus limbatus and Carcharhinus leucas individuals. The sharks were tracked on 13 omnidirectional acoustic receivers positioned on reefs throughout the Inhambane province of southern Mozambique. The community composition of reef fishes appeared to influence the species of elasmobranch that frequented each survey area. Sharks visited reefs with the most abundant piscivorous fish life, which we determined to be linked to foraging opportunities. Small-bodied stingrays were only observed visiting shallow reefs near intertidal sand flats. Pelagic rays (e.g. Mobula spp.) were most often observed while cleaning on reefs that were proximate to their foraging grounds.Elasmobranch abundance on reefs was found to vary across several spatiotemporal and environmental parameters, resulting in patterns of reef use across various temporal scales. Most elasmobranch species became abundant on reefs during the summer, and tide, water temperature, and moon illumination were found to be strong predictors of their presence and abundance. Closely related species were similar in their responses to the measured environmental and spatiotemporal parameters and these species visited the same reefs with specific biological characteristics. Reducing pressures on the reefs that elasmobranch species rely on, and eliminating the extraction of elasmobranchs around these reefs, could benefit the populations of vulnerable elasmobranchs off the coast of southern Mozambique.
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An examination of interspecific competition using observations in behaviour and physiology: A case study of Guanaco (Lama guanicoe) and domestic sheep (Ovis aries) in Chilean PatagoniaThe introduction of a new species to ecosystems can result in competition between native species and the introduced, with adaptations that may allow coexistence, through resource facilitation or partitioning, unable to evolve, given the short co-evolutionary time period. Consequently, in cases where livestock species have been introduced to a new system, competitive interactions between native and domestic species have been directly instigated, with interspecific competition between sympatric, free living ungulates and domestic livestock becoming an increasing concern for conservationists. Understanding the specific ways and mechanisms in which this competition manifests is critical for informing conservation management, both of wild species, and domestic livestock. Throughout this thesis, I examine the case study of wild guanaco (Lama guanicoe) and domestic sheep (Ovis aries), in the Patagonian Steppe ecosystem of Southern Chile, a system in which competition has been demonstrated as highly probable. Two key elements in guanaco-sheep competition were investigated, to determine whether competitive effects manifest in (1) foraging behaviour, by examining the effects of sheep presence on the behavioural changes in guanaco, and (2) physiology, by examining the effects of sheep presence on guanaco separately for cortisol and testosterone. (1) Guanaco bite rates generally increased with vegetation biomass availability. However, when sheep were present in high densities, the pattern reversed, with guanaco bite rates decreasing with vegetation abundance. Additionally, the probability of guanaco feeding occurring at any one time was shown to be higher in areas shared with domestic sheep than in national parks, where sheep are absent. Both results suggest guanaco prioritise feeding behaviours at the expense of other behaviours, where sheep are present. (2) Sheep presence did not predict either the cortisol or testosterone profiles of guanaco. Instead, cortisol concentrations were influenced by the group number and composition (number of adults and juveniles). Conversely, testosterone content was influenced mainly by the specific Age-Sex Class (social group) of the individual.
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Spatio-Temporal Dynamics of Wolves in the Italian AlpsThe recolonization of wolves (Canis lupus) in Europe has become a notable ecological and conservation success in recent decades, though it presents various legislative and management challenges. These challenges are heightened by the wolves' wide-ranging distribution, which often crosses administrative boundaries. Effective management of wolves depends on robust data from well-designed monitoring programs, which are difficult to implement in fragmented regions. Italy has taken significant steps to address these issues, conducting the first national scale monitoring of wolf abundance and distribution in 2020-2021 using non-invasive genetic sampling (NGS) combined with Spatial Capture-Recapture (SCR) modelling. This thesis explores a variety of ways to implement and optimise the current monitoring strategies by focusing on the Italian Alpine region. This area, in particular, can rely on historical information on wolves since the first surveys in the 90’s and on a highly trained network of personnel dedicated to their monitoring that has been implemented over the years. The year of national monitoring has been a great success in coordination and results, but it opens the question of the feasibility of maintaining such high quality in the long term and with possible reductions in economic funds. In fact, with both European and national management of the species expected in the next future, constantly updated abundance estimates will be essential to ensure the conservation of the species. In this thesis I investigated how the combination of NGS and SCR to obtain population size estimates can be optimised by identifying reduction limits for the number of search transects and also for their repetitions within the sampling season. This will allow to reduce both effort and costs for the next years of population size monitoring while maintaining accuracy and precision. Additionally, I explored the feasibility of extending large-scale monitoring of wolf abundance in the Italian Alps using more cost-effective tools, such as camera traps. I demonstrated the unsuitability of a group of statistical models, Spatial Counts or unmarked SCR, which are often used when individuals in the population are not distinguishable from each other. After identifying the limitations of the current modelling framework, I proposed a solution to address some of these issues by incorporating the group-living nature of wolves into the existing model through an extension of the Spatial Counts approach. Finally, I tested whether the drivers of the latest phase of wolf expansion throughout the Italian Alpine region have changed over time. I used a Dynamic Occupancy model to analyse wolf presence-absence data from 2014 to 2021. This analysis revealed the increasing importance of prey richness in colonization and persistence dynamics together with the smoothed effect over time of human densities. Additionally, I identified key areas where new potential conflicts could arise in human-dominated landscapes. Addressing these challenges is crucial for the continued recovery and sustainable coexistence of wolves with human communities in Italy and all Europe. Finally, I discussed all the findings in light of future population management of wolves.
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Life history strategy of western gorillas (gorilla gorilla gorilla)Abstract available in hard copy
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In vitro production of osteoclastsAbstract available in hard copy
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Regulation of osteoclast activity: differential adhesion of osteoclasts to the bone surfaceAbstract available in hard copy
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Sex differences in the social relationships of wild spider monkeys (Ateles geoffroyi yucatanesis)Abstract available in hard copy
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The biological relevance of monomeric and dimeric osteoprotegerinAbstract available in hard copy
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The descriptive epidemiology of prostate cancer with consideration of prognostic markers in Merseyside and Cheshire 1974-1993Abstract available in hard copy
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Dynamics of lichen dominated biological crusts in El Cautivo Badlands, Southeast SpainAbstract available in hard copy
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The regulation of osteoprotegerin production by effectors of bone turnoverAbstract available in hard copy
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Characterisation of the rat phenylalanine hydroxylase gene promoterAbstract available in hard copy
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Traditions in Wild Spider Monkeys (Ateles geoffroyi)Abstract available in hard copy
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Molecular ecology of Long-finned pilot whales (Globicephala melas) in the eastern North AtlanticThe long-finned pilot whale (LFPW) (Globicephala melas) is a large matrilineal odontocete, has antitropical distribution, with a subspecies in each Hemisphere, G. melas melas in the North Atlantic, and G. melas edwardii throughout the Southern Hemisphere. It is the species most commonly encountered in mass stranding events (MSE) globally. The causes driving such events are often complex and multi-layered or even indeterminable. However, social cohesion or the disruption of the species’ renowned social bonds are thought to be a key factor, regardless of other external influences. This PhD thesis aimed to explore this by employing mtDNA and nuclear genetic markers to investigate kinship among samples collected from MSE and an “at-sea” pod group. Six MSE were analysed with a panel of microsatellite markers to determine the kinship dyads within each event. In all but one MSE calves were found with missing mothers, and in some events mother-offspring dyads were separated over different stranding phases, suggesting that disruption of these important relationships can cause/extend MSE. Additionally, samples from a grind (caught pod) were included in analysis to compare an “at-sea” pod assemblage to those involved in a MSE. Confirming that LFPW pods are composed of highly related small family groups, a pod unit, these pod units are found in association with other such units, a pod complex and this is conserved across both individuals “at-sea” and those within a MSE. This also indicates that MSE may not be driven by kin group disruption per se. Population structure across the eastern North Atlantic was also assessed using a combination of mtDNA, microsatellites, and RAD-Seq. Although, mtDNA reported significant differentiation between Scotland and Ireland, the nuclear data supported a lack of neutral and non-neutral genetic structure. This demonstrates the weakness of using only mtDNA to infer population structure within a species with matrilineal groups, while the high population connectivity is important in terms of spatial management strategies and supports the need for cross border collaboration. Finally, genome wide SNP analysis was used to compare the two subspecies, for the first time, revealing a high level of neutral divergence (FST = 0.215) and robust assignment to Hemisphere. Multiple marker-based neutrality tests also revealed a number of positive outliers between the Northern and Southern groups, compatible with adaptive divergence and/or genomic incompatibilities. The level of neutral and non-neutral divergence, alongside clear geographical separation, indicate that taxonomic reclassification may be required designating the separate Hemispheres as distinct species.
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The Social System, Behaviour and Communication of the Golden Monkey (Cercopithecus mitis kandti)Forest guenons live in polygynous groups where males disperse on reaching sexual maturity and females remain within their natal group for life. During the mating season, the resident male regularly faces reproductive competition from extra-group males leading to extreme male-male competition for access to females. The golden monkey (Cercopithecus mitis kandti) is a little-understood, endangered guenon endemic to the Virunga Massif and Gishwati-Mukura National Park (Rwanda), known to live in large groups. The aim of this study was to provide the first behavioural account of this species and to describe and quantify its social system and communication. Behavioural and spatial data were collected five days a week over 15 months, using focal, instantaneous point samples and ad libitum sampling, from the habituated Kabatwa group in the Volcanoes National Park. A total of 31 adult males were individually identified within the home-range, and categorised as resident (n=11), transient (n=4), influx (n=10) or non-resident (n=6). Elo-ratings showeda consistently stable, tolerant, egalitarian hierarchy in resident males, who displayed low levels of non-contact aggression with more severe agonism directed towards extra-group males. Social network analysis revealed closer spatial relationships between resident males during the non-mating season in the forest and consistent agonistic networks. The mating season, defined through behavioural observations and estimating conception based on birth dates, extended over 5 months and females were observed copulating outside their conception window. Males followed females and both sexes mated with several partners over the season; the use of gestural displays were common in this reproductive context, as well as in agonistic contexts. The highly seasonal births coincided with bamboo shooting season when the group spent the majority of time in closed bamboo, with increased ground feeding; ground-feeding was frequent in this population (28% overall), and also reflected foraging for potatoes in agricultural land adjacent to the forest. The group spent about 50% of their time feeding; bamboo plant parts constituted 65.3% of their foraging effort throughout the year rising to 81.4% on bamboo shoots alone when they were available. Males exhibited a wide variety of sex-specific calls in different contexts; with some related to dominance rank. Vocalisations were examined through GLMMs and these were often different in form or context compared with other guenons, notably the single and double boom, nasal scream and male grunt. In summary, golden monkeys observed in this study had a multi-male, multi-female social organisation; both sexes were promiscuous during the mating season, and births were highly seasonal. Resident males were tolerant of each other, exhibited a stable egalitarian hierarchy with a broad communication repertoire including sex specific calls and gestures. Discussion focuses on comparison with other guenons, the unusually large group size and the unique, all-year-round, multi-male society observed in this golden monkey group. Further research is warranted on other groups, to explore female social structure and relationships, behavioural development, and to establish an understanding of life history strategies.
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Application of genetic techniques to conservation of the Critically Endangered Grenada Dove Leptotila wellsiThe Grenada Dove Leptotila wellsi is a Critically Endangered species endemic to the island of Grenada. It exists in two geographically isolated populations across the island. As an endemic on a small island with a limited and decreasing population, this species is at risk from genetic deterioration. Particular risks include inbreeding depression and accelerated loss of genetic diversity resulting from ongoing habitat fragmentation and population isolation. The work reported in this thesis aimed to provide the first genetic data for the Grenada Dove, assess its genetic status and determine what conservation management recommendations can be made to help ensure its long-term survival. A systematic literature review revealed geographical bias in how genetic approaches have been applied to the conservation of island bird species, under-representation of threatened species and highlighted a gap between genetic research and active conservation management. A protocol for obtaining usable genetic material from moulted plumulaceous feather samples was developed and showed that samples collected non-invasively in the field, that were kept in non-optimal conditions for deoxyribonucleic acid (DNA) extraction, can be used effectively to sequence informative regions of mitochondrial DNA (mtDNA) for genetic analysis. The evolutionary and life history of the Grenada Dove were investigated by estimating its phylogenetic placement and using phylogenetic comparative methods for estimating unknown life history traits. The Grey-Chested Dove Leptotila cassinii was identified as the species with which the Grenada Dove shares the most recent common ancestor, with an estimated divergence of approximately 2.53 million years ago. Life history trait values were predicted for the Grenada Dove and suggest this species will be slow to recover after a major population decline. The mitochondrial genetic diversity of Grenada Dove populations was assessed for the two areas of occupancy. Two haplotypes were identified with one haplotype unique to the population in the West. Selective neutrality tests Fu’s Fs=0.78 and Tajima’s D=0.83 were positive and not significant, with an FST value = 0.71 suggesting a marked genetic divergence between the two populations. This study showed low mitochondrial genetic diversity, a non-expanding population and iii | iii clear evidence for genetically isolated populations. Population viability analysis (PVA) was used to evaluate extinction risk and the potential for conservation management for the two populations of the Grenada Dove. This PVA identified that loss of forest habitat to commercial development is likely to have the biggest impact on extant populations and that conservation management to increase productivity is likely be the most effective conservation strategy. This thesis contributes novel information regarding evolutionary history, life history, population genetics and future population trajectories to inform long-term conservation actions for the Critically Endangered Grenada Dove.
