Ecology

Lake whitefish (Coregonus clupeaformis) are ecologically, economically, and culturally significant across their range, yet little is documented about the species' spawning behaviour. Recruitment of lake whitefish has dramatically declined over the past two decades across many regions of the Laurentian Great Lakes, most notably in lakes Huron and Michigan, prompting research efforts to fill critical knowledge gaps in the life history of this species. Understanding the reproductive ecology of lake whitefish, including documenting aspects of spawning behaviour, may reveal clues about factors contributing to the declines. This study used fine-scale acoustic telemetry to characterize sex-specific movement patterns and habitat associations of lake whitefish during the spawning season. A VEMCO Positioning System (VPS) was deployed at an active spawning shoal in Georgian Bay (Lake Huron), with guidance provided by Saugeen Ojibway Nation members with local ecological knowledge about the shoal and the lake whitefish population. In the fall of 2020, 50 lake whitefish were captured and tagged at the spawning shoal; 28 of those fish were observed the following spawning season in 2021. A clear increase and decrease was observed in the presence of individuals in the study area over the spawning period. Both sexes moved into shallower waters at night and deeper waters during the day at rates of 0.162 m/h and 0.08 m/h, respectively. Decreased rates of movement and horizontal distance travelled were detected during the day leading up to a peak activity phase where 22 fish were present. At night during this peak activity phase, males moved 30.0% faster on average than females (0.204 ± 0.13 and 0.143 ± 0.10 m/s, respectively). This study provided a unique opportunity to work with local First Nations to understand lake whitefish spawning behaviour, providing insights into the reproductive ecology of a population undergoing concerning declines in recruitment and abundance.

Author Keywords: Coregonine restoration, Coregonus clupeaformis, Fine-scale acoustic telemetry, GLATOS, Spawning habitat, Two-Eyed Seeing

The Great Lakes represent nearly a fifth of the global freshwater surface supply, and support culturally, economically, and ecologically important fish species such as Walleye (Sander vitreus). With water temperatures projected to rise by several degrees in the coming century, understanding the energetic impacts on fishes is crucial for effective habitat and fisheries management. I measured the swimming performance, accelerometer-based activity, and metabolism of walleye in relation to body size, sex, and water temperature to assess potential responses to climate variability. Both acceleration and swim speed predicted metabolic rate with reasonable accuracy. Temperature had a positive effect on oxygen consumption whereas body mass had a negative effect. Critical swimming speed increased with temperature, and tailbeat frequency had positive relationships with swim speed and acceleration. My laboratory-based calibrations should enable remote field monitoring of energy use of walleye (via accelerometers) and help conserve an important species through bioenergetic modelling.

Author Keywords: accelerometry, bioenergetics, climate change, metabolism, respirometry, walleye

Estimation of population abundance from samples has inherent practical challenges. Moreover, analytical methods to estimate abundance may vary in statistical assumptions and prediction uncertainties. I evaluated the performance of design-based and model-based methods to estimate Canada geese (Branta canadensis) abundance based on aerial fixed-width transect surveys in the Hudson Bay Lowlands, Canada. I evaluated Empirical Bayesian Kriging (EBK), areal interpolation and a ratio estimator on the basis of accuracy and precision using spatial point simulations. Untransformed EBK was the most accurate and precise, due in part, to its inherent handling of nonstationary distributions. The ratio estimator followed the same trends as EBK and, in some cases, had higher precision. Consideration of alternative analytical methods and their strengths and weaknesses is an important step in generating reliable information for population monitoring. Geostatistical approaches such as EBK have the benefit of providing spatially explicit mapping of abundance and reliable population estimates.

Author Keywords: Areal interpolation, Design-based inference, Empirical Bayesian Kriging, Geostatistics, Model-based inference, Ratio estimator

Acoustic communication is vital for mediating interactions between individuals and their environment. From echolocating bats to isolated rodent pups, ultrasonic vocalizations are a useful mechanism for producing localized and cryptic acoustic signals. Flying squirrels have been demonstrated to produce almost exclusively ultrasonic calls which is rare in both squirrels and mammals, though the significance of this acoustic range is unknown. To investigate the context of ultrasonic calls in these gliding mammals, I created phylogenetic comparative analyses to compare ecological and morphological traits against call frequencies. I found that nocturnality, a trait entangled with gliding in squirrels, was related to higher-frequency calls. Furthermore, by comparing all gliding mammals and their non-gliding counterparts, I found that gliding mammals produce significantly higher frequencies than these relatives. This form of cryptic communication is likely used to avoid predation, which was further supported by behavioural experiments wherein flying squirrels used significantly higher frequencies when predation risk increased. While high frequency communication was used by most gliders, I found that ultraviolet-induced photoluminescence, another potential form of crypsis, was strongly associated with nocturnality, with half of the tested gliding mammals showing evidence of this unique colouration. While ultrasonic vocalizations are widespread in echolocating bats and echonavigating mammals, I did not find evidence to support echonavigation in flying squirrels. Instead, I found that ultrasonic vocalizations are used in a variety of social contexts and during solitary foraging and exploration. These combined results demonstrate the unique ecological and evolutionary pressures acting on small-bodied, nocturnal gliding taxa and the resulting cryptic behaviours and communication.

Author Keywords: communication, flying squirrels, gliding mammals, Sciuridae, ultrasound, ultraviolet-induced photoluminescence

I tracked summer movements and activity of snowshoe hares (Lepus americanus) in southwestern Yukon, Canada, during their population cycle (2015–2022) to assess the primary drivers of movement. Hares exhibited variable movement and activity during the cycle, exhibiting increased home range size and higher daily displacement during low population densities. Males exhibited more dramatic increases in their home ranges (>3-fold), and had greater and more variable movement rates and time spent travelling than females. The ratio of predators to hares was highest at low hare densities when hares were moving most, and seasonal activity of hares seemed unrelated to that of predators. Differences between sexes imply that reproductive activities likely were the main driver of hare movement variation rather than food availability. These findings reinforce that, even in highly variable environments, potential rewards associated with successful mate search and reproduction may outweigh the risks associated with reproductive behaviour.

Author Keywords: behaviour, boreal forest, GPS telemetry, home range, movement ecology, predation risk

Muskrat populations are declining across North America. In recent decades, hybrid cattail Typha x glauca has been invading wetlands in North America. This invasion is degrading wetland habitat, leading to reduced interspersion of water and vegetation. Muskrats are wetland-obligates and their populations are positively linked to marsh interspersion. Therefore, muskrat populations may be declining due to the invasion of T. x glauca and subsequent reduction in interspersion. To test this hypothesis, I first sampled marshes across south-central Ontario, comparing muskrat densities with the relative frequency of T. x glauca and the degree of interspersion. Second, I measured intensity of use by muskrats in a large wetland along a gradient of interspersion. My findings suggest that reduced interspersion may be contributing to muskrat population declines, but it is unclear to what degree T. x glauca is responsible. Further research is needed to understand the effects of wetland invasions on muskrat populations.

Author Keywords: invasive species, Ondatra zibethicus, Southern Ontario, Typha x glauca, wetlands, wildlife conservation

Amphibian biodiversity is in global decline, driven primarily by habitat loss and fragmentation arising from landcover alteration. For pond-breeding amphibians, larval abundance should be governed by aquatic breeding site quality, surrounding terrestrial habitat characteristics, and proximity to neighbouring populations. If safeguarding salamander populations is a priority, conservation efforts will benefit from understanding the relative importance of each feature on salamander populations. I sought to identify the factors associated with relative abundance of Ambystoma salamander larvae across habitat patches on Pelee Island, Ontario, Canada. Larval density and a suite of environmental variables were measured at 34 breeding sites across the island. Using spatial analysis, I also determined landcover features surrounding the breeding site, including, terrestrial habitat type, terrestrial patch size, and indices of isolation (e.g., nearest neighbour distance, proximity index). The relative abundance of Ambystoma larvae was best predicted by additive effects of breeding site quality (e.g., canopy cover, submergent vegetation, and cooler water temperature) and size of surrounding terrestrial habitat patches. I did not detect any influence of agricultural land cover within 300 m of the breeding sites on larval count, implying that Ambystoma can persist within agriculture-dominated landscapes provided that high breeding habitat quality is maintained, and ponds are embedded within large forest patches. Further, I failed to detect any impact of breeding site isolation on larval numbers, indicating that local habitat quality and terrestrial patch size more strongly determine larval abundance than patch connectivity. My research highlights the critical importance of conserving high-quality aquatic breeding habitats and maintaining large contiguous patches of terrestrial habitat for amphibian

Author Keywords: Amphibian, Anthropogenic impacts, Biodiversity conservation, Habitat fragmentation, Habitat suitability, Salamanders

Understanding habitat needs of a species is critical, especially for species reintroduced to an area or expanding their range. I evaluated roost tree selection and survival probability of GPS-tagged eastern wild turkeys (Meleagris gallopavo silvestris) from 2017–2020 and 2022 in Peterborough County, Ontario, Canada. Fine-scale roost tree selection was associated with larger trees, with microclimate factors such as wind speed, temperature, and precipitation having little to no influence. Turkeys showed high annual survival probabilities relative to other northern regions of their range, but survival was not influenced by proximity of roost tree to a building. The behaviour of roosting in an elevated perch helps turkeys avoid ground-dwelling predators, but specific selection of one tree versus another has little additional benefit to survival. Turkeys appear to survive well in a landscape that is a mix of agricultural and urban, with forest patches intact for roosting habitat.

Author Keywords: Eastern wild turkey, habitat, Meleagris gallopavo silvestris, microclimate, roost sites, survival

Understanding threats to declining species at multiple stages of their annual cycle is important for determining the cause of their declines and conserving their populations. To assess potential responses to changing habitat and predators under climate change, I compared the nest site characteristics, responses to human intruders, and migratory patterns between Short-billed Dowitchers and Stilt Sandpipers breeding in Churchill, MB. I conducted behavioural observations and habitat surveys and deployed radio transmitters on birds during incubation. Short-billed Dowitcher nests had higher concealment and adults were more aggressive than Stilt Sandpipers. Short-billed Dowitchers took an eastern migratory route and stopped in the southeast US, whereas Stilt Sandpipers migrated west. Short-billed Dowitchers displayed relatively high connectivity during migration with nearly 1/3 of confirmed stopovers occurring at a single site in Georgia. These findings highlight the importance of considering varying antipredator defense and migration strategies in the face of climate change.

Author Keywords: Central Flyway, incubation, Midcontinent, migratory connectivity, Motus, nest concealment

Migration, space use, and phenology play key roles in shaping avian populations and are therefore critical for conservation. My thesis examines the migration strategies and non-breeding spatial requirements of Virginia's beach-nesting American Oystercatchers (Haematopus palliatus), as well as the nesting phenology of mid-Atlantic American Oystercatchers and Piping Plovers (Charadrius melodus). I assessed migratory decisions using field-readable bands and GPS transmitters, finding that ~90% of Virginia's beach-nesting American Oystercatchers migrate out-of-state during the non-breeding season, though tested hypotheses did not strongly predict migration patterns. I then estimated home range sizes of American Oystercatchers during the non-breeding season, revealing high individual variation (12.1-201.6 km²) and a potential trend toward larger home ranges in males. Finally, I analyzed clutch initiation timing of American Oystercatchers and Piping Plovers in response to climate change, finding that American Oystercatchers advanced timing of breeding by 10.7 days between 2005-2022, while Piping Plovers showed no significant shift.

Author Keywords: behavioural ecology, climate change, home-range, migration, movement ecology, phenology