Long-term monitoring for conservation typically requires unbiased estimates or indices of abundance, thereby allowing inference of population trends. Biased estimates can arise when individuals vary in capture probability, especially when overall capture probability is low. We used 3 methods to compare estimates and indexes of the abundance and sex ratio of spotted salamanders (Ambystoma maculatum) breeding in a 4-ha lake over 14 years to counts from a drift fence around the perimeter of the lake. The 3 sampling methods were 1) deployment of aquatic funnel traps around the lake and marking all individuals captured; 2) counting egg masses on the lake; and 3) surveying a coverboard array around the perimeter. To estimate male and female abundance and survival from the aquatic trapping data, we fitted a state-space formulation of the Jolly-Seber model with data augmentation to the encounter histories. We compared model formulations with and without individual heterogeneity in capture probability. Annual breeding turnout at the drift fence varied from 4,476 to 5,282 individuals for the 3 years surveyed. Abundance estimates from aquatic trapping data were substantially underestimated (lower by 67-75%) relative to drift fence counts when individual heterogeneity in capture probability was not addressed, whereas including individual heterogeneity resulted in sex-specific abundance estimates that were consistent with drift fence surveys. Raw sex ratios from aquatic trapping were male-biased (ranging from 0.67 to 0.81 proportion male, or 2.0:1 to 4.2:1 as a male:female ratio), whereas counts from the drift fence survey and estimates from the Jolly-Seber model with individual heterogeneity indicated female-biased sex ratios (ranging from 0.35 to 0.49 proportion male, or a ratio of 0.54:1 to 0.95:1). Egg mass counts were weakly correlated with abundance estimates, and cover board surveys detected less than 1% of the population. Our study underscores the utility of drift fence surveys as a reference for estimating the abundance of breeding individuals and the importance of considering individual heterogeneity in capture probability when estimating abundance of pond-breeding amphibians from capture data with imperfect detection. Our study also cautions that potential indices of abundance, such as egg-mass counts and coverboard counts, should be validated against reliable abundance estimates.

Many populations show pronounced individual heterogeneity in traits such as somatic growth rates, but the relevance of this heterogeneity to population dynamics remains unclear. Individual heterogeneity may be particularly relevant to long-lived organisms for which vital rates (survival and reproduction) increase with adult growth, as subtle differences in growth rates can have major fitness consequences. Previous analysis of data for snapping turtles (Chelydra serpentina) in Algonquin Park, Canada, from 1972 to 2012 showed that individual heterogeneity in growth rates and size-specific reproductive rates of adult females led to eightfold variation in lifetime reproductive output. Here, we test whether this individual heterogeneity affects population dynamics by comparing projections from alternative integrated population models (IPMs) where: (1) vital rates of adult females increase with size and there is individual heterogeneity in their adult growth and reproduction parameters as well as their ages at maturity; (2) vital rates increase with size but there is no individual heterogeneity; or (3) vital rates are assumed equal among adult females. The three IPMs all integrated component models for growth, reproduction, and survival, incorporated random annual variation in rates, and used data augmentation to model unobserved individuals including future recruits. The data augmentation approach allowed the individual heterogeneity in parameters to be extrapolated from observed to unobserved individuals under Model 1. Models 1 and 2 produced similar annual estimates of recruitment, mortality, and abundance from 1972 to 2012 and similar projections for the next 10 years. Those projections had wide prediction intervals (5% increase to 73% decline) due to annual variation in rates but were consistent with the 59% decline estimated based on new data collected from 2012 to 2022. The projected decline reflected predicted decreases in survival and recruitment due to a decrease in the average body size of adult females. Consequently, Model 3 gave more optimistic projections that were inconsistent with the observed decline. The results therefore showed that the size composition of adult females, and therefore their overall somatic growth rate, was important to the dynamics of the population. However, the results also indicated that the pronounced individual heterogeneity in growth rates observed was irrelevant to population dynamics.

- The Northern Map Turtle (Graptemys geographica LeSueur 1817) occupies large lakes and river systems in southern Ontario and southern Quebec, Canada, and the northeastern United States. The species is highly aquatic and basks conspicuously, which allows for reliable sighting and mapping of the species' distribution. We document a long-distance movement approximating 60 km by watercourse of an adult female Northern Map Turtle and extralimital observation at the species' northern climatic range limit and provide growth data from captures over a decade apart. These opportunistic resightings suggest that Northern Map Turtles are more mobile than generally recognized and highlights the importance of habitat connectivity to facilitate long-distance movements.

Amphibians that reproduce in early spring at northern latitudes may encounter environmental ice while migrating to their breeding sites. Due to the nucleation properties of ice, contact with environmental ice may induce rapid freezing of body tissues, which can cause irreversible damage to cells and lead to death. Although some species of salamanders are known to move over ice during early spring migration, freeze-intolerant species are expected to avoid physical contact with ice crystals to minimise the risk of freezing. Here, we documented the thermal biology of the freeze-intolerant blue-spotted salamander (Ambystoma laterale Hallowell, 1856) migrating at sub-zero temperatures in Algonquin Provincial Park, Ontario, Canada. During our surveys, we found sheltered, inactive, and migrating individuals; some in direct contact with ice. Our field measurements of skin temperature using high-resolution thermal imaging suggest that A. laterale can sustain activity in sub-zero temperatures, possibly in a supercooled state (i.e., chilled below the freezing point of body fluids but not frozen). By migrating in such conditions, these salamanders may overcome the risk of freezing while simultaneously prolonging their breeding season and potentially avoiding predators.

Morphological abnormalities in amphibians are commonly associated with anthropogenic activity, although little baseline information on the prevalence of abnormalities in uncontaminated environments exist. Here, we leverage a 12-year study of spotted salamanders ( Ambystoma maculatum (Shaw, 1802)) in an uncontaminated ecosystem in Algonquin Provincial Park, Canada, to estimate abnormality rates and explore how abnormalities affect fitness-related traits. Annual abnormality rates estimated from drift fence data ranged from 4.3% to 5.8% of individuals sampled. Abnormality rates from aquatic trapping between 2008 and 2019 varied from 1.2% to 16.7%, where temporal increases in abnormality rates were observed. We also performed a targeted, systematic literature survey and found that Caudata exhibited a slightly higher abnormality prevalence than Anura, and that the baseline frequency of abnormalities described at our drift fence site is slightly lower than rates reported in the literature (8.1%, 95% CI, 4.76%–13.3%). Salamanders with abnormalities exhibited a slightly, but not significantly, higher body condition and a significantly earlier arrival date at the breeding site, both of which are traits typically associated with high-fitness individuals. Our study suggests that abnormalities have detectable phenotypic consequences, and underlines the need for temporal sampling efforts to provide ranges of baseline abnormality rates, rather than a point estimate.

To decide whether to remain underground or to emerge from overwintering, fossorial ectotherms simultaneously process environmental, gravitational and circannual migratory cues. Here, we provide an experimental framework to study the behaviour of fossorial ectotherms during soil temperature inversion - a phenomenon that marks the transition between winter and spring - based on three non-mutually exclusive hypotheses (thermoregulation, negative geotaxis and migration restlessness). Using a vertical thermal gradient, we evaluated how temperature selection (Tsel), activity and vertical position selection differed under simulated soil temperature inversion (contrasting the active versus overwintering thermal gradients) in the spotted salamander (Ambystoma maculatum). Salamanders had different Tsel and activity levels between gradients, but selected similar heights regardless of thermal gradient orientation. Negative geotaxis may explain responses to changes in vertical thermal gradient orientation, with migratory restlessness contributing to differences in activity levels. Ultimately, our work should benefit those who aim to better understand the biology of fossorial ectotherms.

Subsidized predators are animals whose populations proliferate through association with humans. As subsidized predators, birds in the family Corvidae (Corvus spp., crows and ravens) pose an additive mortality threat to turtle eggs, juveniles, and, in some cases, adults. In this synthesis, I (1) review published and unpublished case studies of corvids as predators of chelonians, (2) examine regional population trends of corvids relative to the status of co-occurring chelonian species, and (3) evaluate our current understanding of subsidized corvids as threats to chelonians. Hyperpredation of chelonians by corvids is geographically widespread, locally severe where and when predation occurs, facilitated by anthropogenic subsidies (e.g., food, water, and perching, nesting, and roosting sites) and linear corridors (e.g., roads, electrical infrastructure), commonly associated with nesting corvids as predators, and co-occurring with corvid population increases. Hyperpredation by corvids appears to affect demographically sensitive stages of chelonian populations (juveniles and reproductive females) and very likely has long-term detrimental consequences given the slow life history of chelonians. The threat posed to chelonian populations by subsidized corvids is more widespread than currently recognized on the basis of substantial regional increases in corvid populations, the underreporting of predation observations, and the broad geographic areas over which hyperpredation of chelonians is occurring.

Temperate ectotherms have responded to recent environmental change, likely due to the direct and indirect effects of temperature on key life cycle events. Yet, a substantial number of ectotherms are fossorial, spending the vast majority of their lives in subterranean microhabitats that are assumed to be buffered against environmental change. Here, we examine whether seasonal climatic conditions influence body condition (a measure of general health and vigor), reproductive output, and breeding phenology in a northern population of fossorial salamander (Spotted Salamander, Ambystoma maculatum). We found that breeding body condition declined over a 12-year monitoring period (2008-2019) with warmer summer and autumn temperatures at least partly responsible for the observed decline in body condition. Our findings are consistent with the hypothesis that elevated metabolism drives the negative association between temperature and condition. Population-level reproduction, assessed via egg mass counts, showed high interannual variation and was weakly influenced by autumn temperatures. Salamander breeding phenology was strongly correlated with lake ice melt but showed no long-term temporal trend (1986-2019). Climatic warming in the region, which has been and is forecasted to be strongest in the summer and autumn, is predicted to lead to a 5%-27% decline in salamander body condition under realistic near-future climate scenarios. Although the subterranean environment offers a thermal buffer, the observed decline in condition and relatively strong effect of summer temperature on body condition suggest that fossorial salamanders are sensitive to the effects of a warming climate. Given the diversity of fossorial taxa, heightened attention to the vulnerability of subterranean microhabitat refugia and their inhabitants is warranted amid global climatic change.

Geophagy is the consumption of hard objects with no caloric value (e.g. soil, sand, sediment) called gastroliths. This behaviour is widespread in animals, and among reptiles, geophagy has been reported in crocodilians and lizards and occasionally in chelonians. In this study, we calculated geophagy rates in snapping turtle (Chelydra serpentina) and painted turtle (Chrysemys picta) hatchlings under various incubation protocols, ranging from highly artificial to semi-natural conditions. Among multiple experiments where eggs were incubated atop the nesting substrate, 66% of painted turtle and 58–93% of snapping turtle hatchlings exhibited geophagy within 24 h of hatching. Snapping turtle hatchlings that experienced a simulated natural nest emergence had an 85–100% rate of gastrolith consumption. Hatchling snapping turtles from shallow simulated nests emerged earlier and had higher rates of geophagy compared with those from deeper nests. Given the high frequency, short time period (24~72 h) and variety of incubation protocols under which geophagy occurred, we suggest that this behaviour is intentional. We discuss multiple hypothesis for the adaptive and functional significance of geophagic behaviour with respect to chelonians, synthesize existing literature on chelonian geophagy and highlight the possible implications of hatchling turtle geophagy for ex situ captive breeding and head-starting programs. Given that hatchlings readily consume their incubation medium, caretakers should carefully consider the substrate their animals are exposed to. Future research should address how widespread geophagy is among hatchling turtles and the possible role of this behaviour for hatchling ecology and health, including effects on the gut microbiome. Animals regularly consume non-caloric foods, such as rocks and soils. This behaviour is exhibited by hatchling turtles, but why? Our literature review suggests that the ingestion of non-caloric foods by turtles is important for nutrition and, in particular, this behaviour may help establish gut health in hatchlings. Observational and experimental study demonstrated that nest characteristics in-part account for why hatchling ‘turtles eat dirt’. This has applications for hatchling ecology as well as captive rearing conservation programs, an increasingly common strategy for the conservation of these globally imperilled animals. This work complements several recent studies and review articles about geophagy in other major vertebrate groups (birds, mammals) and provides a comprehensive summary on the current state of knowledge of this behaviour for turtles.

Sexually coercive reproductive tactics are widespread among animals. Males may employ specialized structures to harass, intimidate, or physically harm females to force copulation, and injuries to the head and neck are reported in taxa with sexually coercive mating systems. The mating tactics of Painted Turtles (Chrysemys picta (Schneider, 1783)) are typically described as involving male courtship and female choice. In contrast, female Painted Turtles in our study population display injuries on the head and neck indicative of bite wounds inflicted by sexually dimorphic tomiodonts and weaponized shell morphology of males during reproductive interactions. Using a 24-year data set, we demonstrate population-level trends in soft tissue wounds inflicted by conspecifics. Adult females experienced more wounding than adult males or juveniles, and larger females had a greater probability of wounding than smaller females. Wounding was concentrated on the dorsal head and neck of females, consistent with expectation of sexual coercion. Furthermore, elevated rates of fresh wounding occurred during late summer, concurrent with the breeding period. By assessing wound demographics, we provide indirect evidence that the tomiodonts and shell of male Painted Turtles inflict injury and function as sexual weapons. These findings shed new light on our understanding of mating system complexity in an often-overlooked and difficult-to-observe taxonomic group.

Oviposition site choice affects a host of offspring phenotypes and directly impacts maternal fitness. Recent evidence suggests that oviparous reptiles often select nest sites where the landscape has been altered by anthropogenic activity, whereas natural nest sites are less often used. We leverage a long-term study of snapping turtle (Chelydra serpentina) to identify natural nest sites and anthropogenic nest sites and to compare habitat variables among nest site types. Natural and anthropogenic nest sites did not differ in average canopy closure, distance to nearest water, substrate composition, or aspect. However, anthropogenic nest sites had less ground-level vegetation and greater soil brightness, and were 3.3 °C warmer than natural nests during incubation. We used the Schoolfield model of poikilotherm development to assess differences in development rate between natural and anthropogenic nests. Because of the difference in temperature, embryos in anthropogenic nests were predicted to have undergone nearly twice as much development as embryos in natural nests during incubation. We outline why the evolution of fast embryonic development rate cannot compensate indefinitely for the low temperature incubation regimes that become increasingly prevalent at northern range margins, thereby underlining why maternal nest site choice of relatively warm anthropogenic sites may help oviparous reptiles persist in thermally constrained environments. Future research should aim to quantify both the thermal benefits of anthropogenic nest sites, as well as associated fitness costs (e.g., increased adult mortality) to elucidate whether anthropogenic disturbance of the landscape can be an ecological trap or serve a net benefit to some reptiles in northern environments.

Sexually coercive reproductive tactics are widespread among animals, where one sex employs specialized structures, called sexual weapons, to harass, intimidate, and/or physically force the other sex to mate. Painted turtles (Chrysemys picta) have been extremely well-studied over the last two centuries, and their mating system has been described as female choice based on male courtship display. The present study arises from observation that males seemingly have more protracted and serrated anterior marginal scutes than females. We hypothesized that the anterior carapace is sexually dimorphic, and that this morphology is a weapon used by males in coercive mating. We quantified anterior carapacial morphology using geometric morphometric analysis of digital photographs, drawing on samples of painted turtles from North American museum collections and our field site in Algonquin Provincial Park. We found that the anterior carapace of males had a significantly more serrated and projected shape compared to females, consistent with the sexual weapon hypothesis. Additionally, anterior carapacial shape was more strongly related to body size in males. Behavioural field observations strongly suggest that males use this morphology as a weapon to harm females during reproduction. The present study complements and strengthens the recent hypothesis that male painted turtles engage in coercion as an alternative reproductive tactic, questioning the long-understood paradigm of exclusive female choice in this well-studied species. Our study invites new avenues of research on the evolution of female harm in a system with extreme selection on female longevity and for which operational sex ratios vary among populations. Further, our work underlines how basic natural history observations can transform our understanding of well-studied systems.

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We examined captures of Painted Turtle (Chrysemys picta) in Algonquin Provincial Park, Ontario, Canada, during the understudied summer–autumn transition period (August–September). The proportion of captured male turtles increased relative to the proportion of females during the late summer and early autumn sampling period, leading to male-biased capture rates in a population with a strongly female-biased sex ratio. We consider explanations for the capture bias in relation to sex-specific activity patterns and briefly discuss the implications of sampling period on the outcome of population structure studies.

We examined captures of Painted Turtle ( Chrysemys picta ) in Algonquin Provincial Park, Ontario, Canada, during the understudied summer–autumn transition period (August–September). The proportion of captured male turtles increased relative to the proportion of females during the late summer and early autumn sampling period, leading to male-biased capture rates in a population with a strongly female-biased sex ratio. We consider explanations for the capture bias in relation to sex-specific activity patterns and briefly discuss the implications of sampling period on the outcome of population structure studies.

We report summer caching of a partial carcass of a White-tailed Deer (Odocoileus virginianus) fawn by an Eastern Wolf (Canis sp. cf. lycaon) in a Sphagnum bog in Algonquin Provincial Park, Ontario, Canada. The microhabitat conditions in bogs (i.e., low temperature, acidity, and organochemical compounds) likely inhibit food spoilage, making bogs potentially important sites for food caching. Wolves in Algonquin Park experience low summer food availability and high pup mortality from starvation. Caches likely serve as necessary reserve food stores for adults and pups. Recent research has shown that wetland habitats are important den and rendezvous sites for Algonquin Eastern Wolves based on prey availability and, we suggest, perhaps for food storage and accessibility. This caching behaviour was recorded on video. We recommend that future research investigate Eastern Wolf selection of food-caching sites, as a complement to other spatial ecology studies.

The ability to identify the sex of animals accurately is important in population studies. Emydid turtles (Testudines: Emydidae) demonstrate a number of sexually dimorphic characters, including head (cranial) size and structure. Field observations from a long-term study of midland painted turtles (Chrysemys picta marginata) in Algonquin Provincial Park, Ontario, Canada, suggested distinct differences in external head morphology between the sexes. We evaluated these putative sexual differences in C. picta head morphology by conducting a visual questionnaire involving human observers of varying levels of experience (novice, beginner, intermediate, and advanced). Observers were capable of distinguishing the sexes based solely on head morphology with a high degree of accuracy (between 79% and 86% success) across experience levels. Observers identified head shape as a defining character distinguishing the sexes. We suggest that visual questionnaires are a quantifiable method of assessing dimorphic characters that can be used in addition to traditional morphometrics or geometric morphometrics to demonstrate a visual, rather than simply statistical, difference among characters and sexes. Despite the breadth of research conducted on C. picta, our study is among the first to describe, assess, and discuss the functional significance of head dimorphism in this model species.

We compare diet and feeding behaviour of Snapping Turtles (Chelydra serpentina) and Midland Painted Turtles (Chrysemys picta marginata) in Algonquin Provincial Park, Ontario, Canada. We observed young Chelydra and Chrysemys turtles feeding on insect and amphibian larvae in ephemeral ponds, adult Chrysemys terrestrially foraging on odonate larvae, and adult Chelydra consuming aquatic vegetation and seeds. These and other observations highlight the importance of seasonally available habitat and food for juvenile turtles. We also discuss the evidence for, and importance of, turtles as seed-dispersal agents for aquatic vegetation. Illustrative video recordings accompany our dietary observations.