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    Behaviour and social organization of little brown bats during dawn swarming
    (University of Waterloo, 2026-04-17) Contursi, Michela
    Collective behaviour in animals, being the coordinated actions and movement of groups of individuals, has important implications for social structure and organization. Females of many temperate bat species roost together in maternity societies, exhibiting roost switching and fission-fusion dynamics throughout the summer season. In the pre-dawn hours, bats gather near roosts and participate in a variety of conspicuous behaviours as a collective, referred to as “dawn swarming”. Using thermal video recordings and roost co-occurrence data from a RFID-monitored maternity society of little brown bats (Myotis lucifugus), we quantitatively characterized behaviours of bats in the area around roosts sites during the dawn swarming period, and investigated the extent to which dawn swarming activity patterns reflects an underlying social structure in maternity societies. During dawn swarming, bats displayed several visual behaviours, including circling the roost and swooping up to its entrance, in dynamic patterns each morning. Dawn swarming activity peaked one hour before sunrise and occurred consistently throughout the maternity season. While some bat activity was observed in the area of unoccupied roosts, disproportionately more activity occurred around roosts that ended up occupied as day-roosts following sunrise. Although this species is known to form preferential roosting associations, the associations observed during dawn swarming were not consistent social subgroups and there was no compelling evidence that individuals preferentially associated with certain conspecifics during dawn swarming. Together, these results suggest that the dawn swarming period functions as a society-level collective behaviour used by bats daily before settling into a roost, facilitating the transition between active (night) and resting (day) states for these animals.
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    Development and integration of technology into the monitoring of bats
    (University of Waterloo, 2026-04-17) Lawson, Felix
    Interdisciplinary collaborations have facilitated many advancements in ecology. Using frameworks and tools from other disciplines, researchers have been able to generate ideas and explore questions that would be otherwise difficult to pursue. Animals that have cryptic lifestyles or live in environments difficult to observe, such as bats, can be explored in greater detail by implementing various technologies. While aspects of the life histories of bats have been well documented, information on some basic behaviour pertaining to distributions and foraging tendencies of some species remain unknown due the difficulty of monitoring sympatric nocturnal species at the landscape scale. We explored methods of tracking individual tropical bats using RFID technology to quantify their movement in a Neotropical landscape. We found that species differed in their detection rates and area overlap with conspecifics within a forest patch. We also found sex differences that may be a result of seasonal behaviour. Additionally, we used current applications of RFID technology at roosting locations to motivate the development of a method for estimating the mass of climbing Eptesicus fuscus. We explored the use of machine learning techniques as well as a linear model to estimate the mass of E. fuscus climbing vertically using collected data of their applied weight. Our results suggest that it is possible to discern differences in mass within the expected range of wild E. fuscus. These results add to our ability to understand and observe animal behaviour and highlight the importance of interdisciplinary collaborations in exploring new ways to collect observations about ecological processes.
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    Economic evaluations of hemophilia A interventions in Canada
    (University of Waterloo, 2026-04-17) Hirniak, Samantha
    BACKGROUND: Hemophilia A is an X-linked disorder defined by a lack of clotting factor VIII within the blood. The current standard of care for hemophilia A is prophylaxis through injection of clotting factors. There are many varieties of clotting factors currently available on the Canadian market including standard half-life, extended half-life, non-factor replacement proteins, and second-generation extended half-life options. No matter what option is chosen, the cost is extremely high, primarily due to the cost of clotting factors, which have been cited as representing over 92% of the cost of hemophilia A treatment. For decades, gene therapy has been in development for those with hemophilia A. So far, none have been approved for use in Canada. Gene therapy is expected to last for at least 5 years without requiring supplemental injections. Gene therapy has an incredibly high short-term cost. Health technology assessments can be used to evaluate the cost-effectiveness of a treatment. There is currently no hemophilia A gene therapy cost-effectiveness study in the Canadian context. OBJECTIVE: The objective of this thesis was to analyze the economic environment of hemophilia A interventions in Canada and to determine if gene therapy would be cost-effective. This thesis completed 1) a population-level retrospective study on health utilities, 2) an economic analysis of the existing prophylaxis options, 3) a healthcare system cost analysis, 4) a narrative review on the diagnosis and treatment pathway for women with hemophilia A, and 5) cost-effectiveness analysis for hemophilia A gene therapy for men in Canada including re-dosable gene therapy. METHODS: Health utilities were retrieved from the Canadian Bleeding Disorders Registry (CBDR) and were analyzed with a multivariable regression model. A microsimulation model was built to analyze the cost-effectiveness of the currently available options (SHL, EHL, non-factor protein, second generation EHL). Healthcare system resource use costs were determined through health administrative data analysis. The microsimulation model was expanded allowing for the inclusion of gene therapy and the dynamics were analyzed. An incremental cost-effectiveness ratio (ICER) value comparing gene therapy to multiple methods of prophylaxis was computed and the most cost-effective treatment was identified. RESULTS: The feasibility study demonstrated, in a perfect scenario, gene therapy could be cost-effective in Canada. The feasibility study also highlighted significant sensitivity to cost and utility data. The population-based, cross-sectional study of health utilities provided the average utility values (and standard deviations) for patients with hemophilia A in Canada 0.79 (0.17), 0.76 (0.20), and 0.77 (0.19) for patients with severe, moderate, and mild hemophilia. The study of health utilities also illustrated that chronic pain was a significant factor in lowered hemophilia A utility. The economic evaluation of modern prophylaxis interventions demonstrated that to be dominant in the Canadian market EA would require a 50% price reduction, even though it significantly improved long-term joint health outcomes. The population-level retrospective study of healthcare costs in Ontario demonstrated, even with hemophilia treatment, there remains an increased healthcare system cost for those living with hemophilia A, regardless of sex. The narrative review on the experiences of women and girls with hemophilia demonstrated that barriers to diagnosis and care remain, and further research is necessary to determine how best to address these barriers. The economic analysis of gene therapy identified very similar outcomes in terms of life-expectancy and utility values to emicizumab. At current list prices, gene therapy has similar quality-adjusted life years to emicizumab and costs ~350K CAD more over a lifelong time horizon. With a 7.5 % price reduction, gene therapy may become the dominant strategy. CONCLUSION/IMPLICATIONS: This provides more insight to decision-makers on whether gene therapy should be reimbursed for hemophilia A patients in Canada while providing a deeper understanding of the health burden of hemophilia A in Canada.
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    Laser Directed Energy Deposition Repair of Laser Powder Bed Fusion Maraging Steel Components
    (University of Waterloo, 2026-04-17) Orchard, Benjamin Ferid
    High-pressure die casting (HPDC) tooling inserts produced via laser powder bed fusion (LPBF) improve thermal balance and extend tool life, but severe thermomechanical cycling inevitably causes surface degradation. While conventional welding repairs introduce excessive heat, laser directed energy deposition (LDED) offers near-net-shape restoration with superior thermal control. However, the mechanical integrity of the LDED deposit-substrate interface remains a critical concern. This thesis investigates strategies to optimize metallurgical bonding at the repair interface of LPBF-produced HPDC inserts. Simulated repair coupons with varying sidewall inclination angles were evaluated using scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) to assess defect removal geometries and toolpath parameters. In addition, peak-aged LPBF substrates repaired via LDED were tested for tensile performance and microhardness response to post-repair heat treatment. Results demonstrate that groove sidewall inclination angles of 45–50° produce acceptable bonding under baseline parameters. Steeper angles require contour pass assistance, with power-based energy modification assessed to be effective in promoting sidewall fusion and suppressing geometric deformation. Tensile testing of as-repaired coupons showed intermediate performance (ultimate tensile strength (UTS) = 1482.5 MPa) with consistent interfacial failure. Post-repair peak aging caused interfacial degradation (UTS = 679.80 MPa), attributed to wire electrical discharge machining (EDM) recast layer contamination and Ti-Al oxide inclusions at the interface; heat treatment successfully restored deposit hardness to 53.8 HRC. Ultimately, this work demonstrates that optimizing groove geometry and contour pass energy is vital for LDED repair efficacy, and it highlights that rigorous substrate surface preparation is a prerequisite to achieving mechanically sound repairs in the peak-aged condition.
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    Advancing microbial risk management through strategic integration of risk assessment and water supply operations
    (University of Waterloo, 2026-04-17) de Brito Cruz, Dafne
    Controlling risks posed by microbial contaminants is a key focus for the provision of safe drinking water. Increasing threats to water supply systems—such as rapid water quality changes associated with climate-shocks (e.g., wildfires, heavy precipitation, etc) as well as infrastructure failures and treatment deficiencies—increasingly challenge microbial risk management and underscore the need for resilience in safe water supply. The goal of this research was to advance drinking water microbial risk management through integration of risk assessment approaches and real-world water supply treatment operations scenarios. Quantitative and qualitative risk-based frameworks were developed to address gaps in knowledge and practice related to monitoring, treatment decision-making, risk assessment and treatment operations. Routine pathogen monitoring programs and the use of monitoring data in risk assessment for treatment decision making were addressed using data from a full-scale water treatment plant. Practical guidance was provided about monitoring and associated risk-based treatment requirements including methods for choosing sampling locations and frequency. Policy contributions involved definition of treatment sufficiency compliance rules and evidence for inclusion of Giardia in protozoa monitoring programs. This work underscored that data collection should be tailored to best represent water entering treatment plants so their use in risk assessment can best inform treatment decisions and maximize return on investment. While this may seem obvious, how to best represent system-specific attributes in monitoring design and implementation is often far from obvious. To shift from routine operations to extreme events, a scenario-based quantitative microbial risk assessment (QMRA) framework was applied in a case study involving a wastewater spill upstream of a drinking water intake, in which urgent risk-informed treatment decisions were needed. Conducting comprehensive and mathematically complex QMRA is not practical when time-sensitive decisions are needed. Thus, the simplified framework developed here demonstrated how preliminary risk assessment can be conducted for short-term, rapid source water quality degradation events and used to inform operational decisions and improve drinking water system response to adverse events. Filtration plays a central role in microbial risk management during drinking water treatment. Although filtration plants include multiple filters, risk is typically evaluated based on individual filter performance. A model was developed to evaluate how dynamic, concurrent operation of multiple filters affects plant-scale filtration performance and thus microbial risk. It was demonstrated that operational response strategies should prioritize improving performance when it is “low” rather than maximizing performance when it is already “high” because microbial treatment performance is typically expressed on a logarithmic scale. Practical implications of several design or operational decisions for microbial risk management such as the number of filters in operation, backwash staggering schedules and filter-to-waste operation were presented. Plant-scale risk assessment is essential to microbial risk management because risk is driven by the collective and dynamic operation of multiple treatment units. Yet, current practice and regulatory guidance do not always acknowledge plant scale considerations. Linking several aspects of water supply integrally related to risk, the effect of dependence between model inputs in drinking water QMRA was then evaluated. Hypothetical scenarios and data from a full-scale water treatment plant were used to demonstrate that ignoring dependence can over- or underestimate risk, sometimes substantially (e.g., more than an order of magnitude), and mislead decision-making. A framework was developed for characterizing the potential for biased interpretation of risk when assumed independence that is typical in QMRA practice is not valid. Finally, the themes and insights described above were connected to more broadly highlight the inextricable linkage between microbial risk assessment and resilience in safe drinking water supply. The concept of operational resilience was defined as a water supply system’s capacity to limit the risk consequences of insufficient treatment performance when adverse events perturb it. Then, hypothetical case studies were used to demonstrate that resilience description must explicitly reflect risk to be an actionable tool. These foundations can be used to develop tools to operationalize resilience in the future. In addition to contributions to advancing risk and resilience sciences and drinking water policies, this research provides actionable knowledge to water utilities for improving decision-making during challenging conditions, assessing microbial risks more accurately and increasing the resilience of treatment operations.