Determining the physiological effects of stressors on organisms is essential to understand how human activities may impact environmental health. American alligators (Alligator mississippiensis, Daudin, 1802) are long-lived, top trophic carnivores inhabiting aquatic environments in the southeastern USA. Because of this, they may serve as important indicators of environmental health. Capture or trapping of crocodilians, including alligators, may be a dangerous and arduous task both for those capturing the crocodilian and the crocodilian itself, possibly affecting the parameters used to evaluate stress/health in an individual. To better characterize how capture and trapping of crocodilians affect physiological parameters, we investigated the effect of capture on white blood cell counts at four distinct time points. The majority of WBC counts, except for basophils, were unaffected (p > 0.05) by capture stress for up to 2 hours following initial capture. These results provide further support that crocodilian WBCs are temporally stable parameters that are useful for investigating exposure to long-term stressors.

I employ the comparative method to improve understanding of the metabolic rates expressed by mammalian hibernators when hibernating at body temperatures ≤ 10°C (deep hypothermia). The weight of evidence is that the mass-specific metabolic rate of adult hibernators in hibernation (HibMR) is constant or nearly constant regardless of body size. I compare to HibMR the metabolic rates of neonatal mice of two species when the neonates are in deep hypothermia. The neonates have mass-specific metabolic rates statistically identical to the HibMR of adult hibernators, suggesting that mammals may express a relatively fixed minimum mass-specific metabolic rate during deep hypothermia, regardless of the cause of hypothermia (hibernation or neonatal cooling). I also compare the relationship between metabolic rate and body size in polar species of teleost fish with the metabolism-size relationship in hibernating mammals. The mass-specific metabolic rates of resting polar fish at polar temperatures – although similar in order of magnitude to mass-specific HibMR in hibernating mammals – exhibit unambiguous allometry in relation to body size, in contrast to the lack or near-lack of allometry in the mammals, suggesting that comparative studies of the two groups might help reveal the mechanisms underlying a switch between allometry and lack of allometry.

Stream temperature is a key driver of physiological function in ectothermic fish, shaping the limits of thermal habitat. Temperature increases from climate change and habitat degradation are a major threat to federally Endangered Athabasca Rainbow Trout (Oncorhynchus mykiss Walbaum, 1792; ARBT) in Canada. This study investigated thermal preferences of ARBT across three streams spanning a natural temperature gradient (7.1–15.0°C mean July temperature) in the McLeod watershed, Alberta, Canada, at the northern limit of Rainbow Trout. Shuttle box experiments were used to assess preferred (Tpref) and avoidance (Tavoid) temperatures using a portable streamside laboratory, where Tpref is thought to represent the optimal temperature zone for metabolism and growth. The mean Tpref was 18.0 °C, higher than expected for a northern Rainbow Trout ecotype adapted to colder headwater streams. Significant variation in Tpref and lower Tavoid values across streams suggests a degree of thermal plasticity in response to different stream acclimation temperatures. These unexpected findings suggest that northern populations may not necessarily be differentially cold-adapted. However, compounding threats and the cumulative impacts of stream warming still pose significant risks to this endangered ecotype. Understanding ARBT’s thermal behavior is crucial for developing habitat protection and conservation policies as climate change intensifies.

Many wild species are declining due to human driven environmental changes, including landscape transformation due to agricultural intensification. This is especially true for insects and their avian predators worldwide. To understand how populations respond to human-induced environmental changes, detailed data on survival, reproduction and dispersal are essential especially in declining populations where immigration can buffer local declines. We used multi-state Capture-Mark-Recapture (CMR) models and 14 years of data (2006-2019) on individually marked Tree Swallows (Tachycineta bicolor (Vieillot, 1808)) breeding on farmlands in southern Québec, Canada, to quantify the effects of agricultural intensity, local weather, and interspecific competition on vital rates and population growth. Annual population growth rates were strongly influenced by immigration and adult return rates. Nest site competition from House Sparrows (Passer domesticus (Linnaeus, 1758)), primarily present in intensively cultivated landscapes, was the main factor driving the observed decline in productivity and adult return rates. Our results suggest that intensively cultivated farmlands act as population sinks, making them unsustainable for Tree Swallows without immigration. Our findings highlight the importance of considering both landscape context and population connectivity when assessing demographic processes. They also underscore the need to study multiple populations over large geographic regions to identify drivers of large-scale declines.

The holotype specimen of Tamiobatis vetustus Eastman, 1897 (NMNH 1717) was the first essentially complete, three-dimensional Paleozoic chondrichthyan braincase known to science. Here, it has been investigated using computerized tomography (CT), revealing its internal morphology for the first time, including the intracranial and labyrinth cavities, internal courses of nerves and blood vessels, plus several remarkable new features which are described here. Some supposedly morphological features of the neurocranium are reinterpreted as bilaterally symmetrical taphonomic artifacts.

Species distribution patterns at range edges can reveal effects of landscape and climate changes which can drive population expansions or contractions. Southern flying squirrel (Glaucomys volans Linnaeus, 1758) populations are common in eastern United States and southeastern Canada, and extend westwardly into the Great Plains. Space-use patterns within their range interior are well documented, though it is unclear if patterns are similar along western range edges. We tracked 10 southern flying squirrels in southeastern Kansas, USA to estimate home-range sizes and patterns in nest-site and tree selection. Forest structure and composition at western range edges differ compared to forest habitat at range interiors, and we predicted differences in home-range sizes and nest-site and tree selection patterns in Kansas compared to previous research. Mean home-range size was 1.55 ha (95% minimum convex polygon) and 5.44 ha (95% kernel density), similar to some populations in the interior of their range. Greater tree genera richness and average tree diameter (DBH) increased probability of nest-site use. Non-hard mast species and greater tree DBH increased nest-tree selection probabilities. Maintaining forest diversity while allowing all tree species to reach maturity could increase available nesting habitat for southern flying squirrels on their western range periphery.

Mammalian coat colour is adaptive, conferring benefits that enhance fitness. While most species have converged to an optimal coat colour, it remains variable in others. Gloger’s rule predicts darker coats in humid than in arid areas; yet this rule requires further testing. Using coat colour data from 2,279 black bears (Ursus americanus Pallas, 1780) from the Yukon, I examined the spatial prevalence of black and non-black colourmorphs. An information-theoretic approach was used to rank candidate models including age, sex, and ecoregion, as predictors of colourmorph prevalence. Ecoregions differed with respect to humidity, habitat openness, and grizzly bear (Ursus arctos Linnaeus 1758) densities, and were used as proxies to test ecogeographical hypotheses. Most black bears were black (64%). Sex and ecoregion were the highest ranked predictors of colourmorph prevalence. Colourmorphs of male black bears—but not females—differed significantly by ecoregion. Males were more apt to be black in humid ecoregions. These results provide partial support for Gloger’s rule operating at ecoregional scales depending on sex. From an evolutionary ecology perspective, the sex-biased conformity to Gloger’s rule is novel and suggests that selection for coat colour may operate differently on males and females, providing an intriguing avenue for further research with polychromatic mammals.

The Elm Point Formation is a Middle Devonian (Eifelian) unit deposited in the Elk Point Basin in North America. Specimens recovered from three localities in the interlake region of Manitoba, Canada, comprise skull and thoracic material of fossil early vertebrates, particularly dental elements. They include the arthrodiran placoderms Elmosteus lundarensis (Jobbins, Moysiuk, Durkin & Brink, 2025), Homosteus manitobensis Okulitch, 1944, and Squamatognathus steeprockensis Hanke, Stewart & Lammers, 1996a, ptyctodonts Ptyctodus cf. calceolus Newberry & Worthen, 1866, and Rhynchodus Newberry, 1873, and sarcopterygians including onychodontids and dipnoans. One sarcopterygian specimen exhibiting cosmine has been cautiously identified as the postparietal shield of an ‘osteolepiform’, likely representing the oldest tetrapodomorph from Canada. The overall faunal diversity of the Elm Point Formation is similar to other North American faunas from the Eifelian. Comparisons between North American Middle Devonian stratigraphic units show a slow change in faunal diversity, with the Eifelian rich in ptyctodont diversity and the Givetian exhibiting a diversification of arthrodires.

Small mammals are fundamental drivers of ecosystem processes, and they act as bioindicators of ecological integrity. Although their monitoring is crucial from a conservation perspective, conventional surveying devices such as pitfall traps are invasive and raise ethical concerns. A potential non-invasive alternative is the analysis of environmental DNA (eDNA) shed by small mammals in the environment. The first step in the adoption of eDNA-based monitoring is the design of species-specific, sensitive and efficient quantitative PCR (qPCR) assays. Here, we developped and validated targeted qPCR assays for three Canadian small mammals: the smoky shrew (Sorex fumeus Miller, 1895), the masked shrew (Sorex cinereus Kerr, 1792), and the southern bog lemming (Synaptomys cooperi Baird, 1858). We also conducted a pilot field study to compare small mammal detection rates from pitfall trap capture and eDNA analysis of soil samples. For the smoky shrew and the masked shrew, detection rates were low for both pitfall traps (6 and 16 %, respectively) and eDNA (6 and 3 %, respectively), while no capture or eDNA detection was made for the southern bog lemming, indicating that a greater sampling effort would be required to better compare the two methods. Additional studies are thus needed before eDNA can be adopted as a reliable method for monitoring small mammals.

The relationship between snow depth and browse availability in Canada’s boreal forest is difficult to quantify because while snow buries lower branches of shrubs, making their twigs unavailable to browsers, snow can simultaneously push the twigs taller branches lower, into browser reach. Here, we use trail cameras to estimate the quantity (g/m2) and quality (solubility, %) of willow (Salix spp. [L.]) twigs available to snowshoe hares (Lepus americanus [Erxleben, 1777]) in response to snow depth (cm) in Kluane, Yukon. First, we estimated the standing biomass and average solubility of willow twigs within three height classes across our study area. Next, over two winters, we took daily images of willow shrubs alongside snow stakes to measure daily snow depth and twig availability by height class (13,015 camera-days). Using general additive models (GAMs), we estimated that total biomass availability increased by 44.5% during the first 10 cm of snow accumulation, peaking at 7.7 g/m2 when snow depth was 27 cm, after which it declined steadily. Collectively, as snow depth increased to 83 cm, total biomass decreased by 68% and available twig solubility increased 44.5%. This novel method highlights the non-linear relationship between twig availability and snow depth that is caused by snow load on shrubs.