Our new paper, led by MSc student Harry Kumbhani and building on fieldwork conducted by former MSc student Curtis Abney, explores how Eastern Garter Snakes (Figure 1) navigate the complex thermal landscapes of wetlands in southern Ontario. Using detailed operative temperature models, which were copper snake replicas equipped with temperature loggers, our team quantified how three adjacent habitat types (closed forest, mixed shrub, and open peat; Figure 2) differ in the thermal opportunities they provide. Although the open peat habitat consistently reached the warmest temperatures and offered the greatest access to the snakes’ preferred thermal range, it also exhibited extreme highs that frequently exceeded the species’ upper thermal tolerance. This created a paradox: the habitat with the highest apparent thermal quality was also the riskiest.
Figure 1. Eastern garter snake (Thamnophis sirtalis sirtalis).Figure 2. A snake’s eye view of the canopy cover within the three habitat types.
Despite expectations that snakes might favour the warmest habitat, we found that Eastern Garter Snakes were most abundant in the intermediate, mixed-shrub habitat, a pattern we describe as a “Goldilocks effect.” This middle habitat provided a balance of sun and shade, offering both basking opportunities and safe retreat sites, and avoided the thermal instability and overheating risk found in the open peat. The study suggests that thermal quality is more nuanced than simply being warm enough; stability, heterogeneity, and safety from extreme temperatures all shape how snakes use their environment. These findings highlight the importance of structurally diverse habitats for temperate reptiles and offer valuable insights into how changing landscapes may influence thermoregulation and habitat choice in the future.
Citation
Kumbhani, HAW, Abney, CR, Giacometti, D, and Tattersall, GJ. 2025. Operative temperatures of Eastern Garter Snakes (Thamnophis sirtalis sirtalis) reveal a Goldilocks effect for habitat use. Canadian Journal of Zoology, 103: 1-15. https://doi.org/10.1139/cjz-2025-0090
A new study led by Morgane Vandendoren, Nicole Bedford, and others from Adam Nelson’s lab at the University of Wyoming has uncovered a new role for oxytocin, the so-called “love hormone.” Published in eLife, the research shows that oxytocin neurons in the paraventricular hypothalamus act as a kind of biological switch, helping mammals transition from cooler, resting states to warmer, active ones. Using mice, the team combined calcium imaging, optogenetics, and behavioural observation to show that bursts of oxytocin neuron activity reliably occur just before an animal warms up and becomes active, even in the absence of social cues. These neurons appear to coordinate both thermogenic (heat-producing) and behavioral arousal, revealing a new layer of oxytocin’s influence that bridges physiology and behaviour.
This collaboration, with contributions from several Wyoming students and collaborators, demonstrates how oxytocin not only shapes social and maternal behaviours but also tunes the body’s thermal and arousal cycles. My lab’s involvement was a bit on the periphery, but focused on the thermal imaging and coding pipelines that helped visualize these rapid transitions in body temperature and activity. Together, the findings expand our understanding of oxytocin beyond its traditional social context, showing that it also plays a key role in the daily rhythm of energy balance and physiological readiness.
The University of Wyoming have a more detailed press release for the study here:
This paper was published in eLife, following an open peer review approach that I am still trying to wrap my head around. The citation is below, and so formally the study is published in preprint format, with us having still to upload a revised manuscript which will address some of the points raised by the reviewers.
Citation
Vandendoren, M, Rogers, JF, Landen, JG, Killmer, S, Alimiri, B, Pohlman, C, Tattersall, GJ, Bedford, NL, Nelson, AC. 2025. Oxytocin neurons signal state-dependent transitions to thermogenesis and behavioral arousal in social and non-social settings. eLife, 14: RP108212. https://doi.org/10.7554/eLife.108212.1
In the cold, temperate forests, long before spring fully arrives, blue-spotted salamanders (Ambystoma laterale) are already on the move. These small amphibians begin migrating to their breeding ponds while snow still blankets the ground and ice lingers on and in the soil. This is a risky strategy for a species that can’t survive freezing. Our recent Natural History note, spearheaded by Dr. Danilo Giacometti and published in the Canadian Journal of Zoology, documents this remarkable early migration and presents new thermal imaging evidence that blue-spotted salamanders achieve this while at sub-zero body temperatures.
For amphibians like blue-spotted salamanders, freezing is typically fatal. Ice crystals rupture cells, leading to irreversible damage. Unlike some frogs that survive being partially frozen thanks to natural antifreezes like glucose, blue-spotted salamanders are known to be freeze-intolerant.
But in spring 2022 in Algonquin Park, during a brief window of opportunity we observed salamanders actively migrating, even while walking across or sheltering beside ice. Using high-resolution thermal imaging, we measured their skin temperatures (a reliable proxy for body temperature in such small animals) and found several individuals with body temperatures as low as –3.6°C, which is well below their known freezing point. Our findings suggest that blue-spotted salamanders may rely on supercooling, where their body fluids remain liquid even below freezing. This strategy has been shown in lab studies to be possible down to about –1.5°C, but our field data suggest some individuals may supercool even further, albeit briefly.
One of the most surprising observations was that several salamanders were in direct contact with ice, a known trigger for freezing of fluids that are supercooled. Despite this, they were active and moving, raising fascinating questions about how they might avoid nucleation (the start of ice formation) in natural settings or if they can manage short-term freeze/thaw during their migration.
Thermal images of blue spotted salamanders migrating at sub-zero temperatures. Temperatures reflect variation in microhabitats encountered by animals during movement, and these observed skin temperatures fall below the known freezing points and minimum supercooling points for Ambystoma laterale.
Why would salamanders take such a risk by migrating so early? There may be several evolutionary advantages. By arriving at breeding ponds early before other species, they reduce competition and potentially avoid predators. Early breeding also gives their offspring more time to grow before winter returns.
Our study opens new questions about the limits of amphibian cold tolerance and the role of behavior and microhabitat selection. More research is needed to understand whether these salamanders truly remain supercooled for long periods or whether they occasionally freeze and recover, a possibility hinted at but not yet proven in this species.
For now, our thermal images offer a rare glimpse into the early spring lives of blue-spotted salamanders and reveal that there’s still much to learn about how animals survive the cold.
Giacometti, D, Moldowan, P, and Tattersall, GJ. 2025. Sub-zero body temperatures during early spring migration in blue-spotted salamanders (Ambystoma laterale). Canadian Journal of Zoology, https://doi.org/10.1139/cjz-2025-0045
Postscript: An Editor’s Lament
The journey that this very brief natural history note took to reach publication was unnecessarily arduous. We originally submitted this study to Canadian Field Naturalist in August 2022. In that initial submission, we heard back after 16 months from the editor that the manuscript had been peer reviewed (3 reviewers) and with straightforward revisions; we supplied revisions within 30 days in January 2024. Then all went quiet with the journal for months. We reached out on numerous occasions to the editors in 2024 about whether the manuscript was still being handled, whether we would hear a decision, and received responses that indicated that editing it was not a high priority.
So, after 2.5 years sitting with Canadian Field Naturalist, we withdrew the manuscript (Spring 2025) and submitted it to CJZ where I am pleased to note that the manuscript underwent a normal peer review process.
As an editor (the average turnaround time for 1st submit Major/Minor decision papers I handle is 51 days – this includes the time to find reviewers), I was saddened at how CFN handled the initial manuscript. There were extenuating circumstances in that the associate editor handling the initial submission passed away, but we were assured by the editorial team that the manuscript would not get ‘lost’ in the re-shuffle.
As a society journal, it deserves support, but 2.5 years to handle a short manuscript does not set a good example for early career researchers; this is almost a lifetime for a graduate student.
I understand that editors need to make difficult decisions and in the course of those duties often reject studies (for fit or for other reasons). But timely decision making is just as important or more so for early career researchers. All the academic editors I know are full-time employed with academic and research jobs, but I have never heard any of them indicate or hint to an author that their submission is not a priority. If the work is not appropriate for the journal, the most humane decision is to reject it in a timely manner.
Anyhow, I am pleased with the Canadian Journal of Zoology’s handling of the manuscript. It was professional and straightforward and now we can move on from this experience.
I do think that we need to support natural history style studies/observations, so I can only hope that by sharing this, those that read this may push for change at journals that could use the support.
We’re excited to share the publication of a new paper in Ecography, led by PhD candidate Sara Ryding (Deakin University, collaboration with Matt Symonds Lab), which explores how climate change may be reshaping the morphology of migratory shorebirds. Using an incredibly extensive dataset of nearly 19,000 juvenile birds across 11 species sampled over 43 years, Sara investigated whether warming temperatures are causing changes in relative wing length, a trait thought to play a role in thermoregulation. Interestingly, while juvenile shorebirds migrating to tropical northern Australia exhibited a consistent increase in relative wing length over time, no such trend was observed in their temperate southern counterparts.
Crucially, the study found no evidence that these morphological changes are driven by developmental temperatures at the breeding grounds, suggesting that these changes are unlikely to be short-term plastic responses. Instead, they may reflect long-term, potentially evolutionary responses to the environmental conditions experienced at non-breeding sites. This work highlights how subtle, climate-linked changes in body shape (e.g. “shape-shifting”) may be occurring unevenly across populations, depending on local climatic pressures.
Congratulations to Sara on this significant contribution to our understanding of how wildlife is adapting to our changing planet.
Citation
Ryding, S, McQueen, A, Symonds, MRE, Tattersall, GJ, Victorian Wader Study Group, Australasian Wader Studies Group, Rogers, DI, Atkinson, R, Jessop, R, Hassell, CJ, Christie, M, Ross, TA, and Klassen, M. 2025. Shape-shifting in relative wing length of juvenile shorebirds: no evidence of developmental temperatures driving morphological changes. Ecography, 2025: e07801. doi: 10.1002/ecog.07801
Congratulations Dr. Danilo Giacometti! The Faculty of Mathematics and Sciences at Brock has awarded you the FMS Best PhD Thesis Award. A supervisor could not be prouder!
Bearded dragons (Pogona vitticeps) have become one of the most popular pet reptiles and in many cases are contributing to research as well. But as their popularity has soared, so too has the need to better understand what these lizards actually need to live well in captivity. Our latest study, recently published in PLOS ONE, examines whether giving bearded dragons more “naturalistic” resources within their enclosures actually improves their well-being. These enclosures included features like climbing structures, loose substrate, and multiple hiding spots, compared to standard setups with only basic furnishings. We expected these more complex spaces to help the lizards behave more naturally and experience less stress. While the naturalistic enclosures did offer better thermal variety (important for ectothermic animals like reptiles), we were surprised to find that they did not have a clear effect on how active the lizards were, how they used their space, or how often they showed signs of stress or relaxation.
Interestingly, only female lizards housed long-term in naturalistic enclosures showed lower levels of physiological stress (measured through ratios of white blood cells), suggesting that any benefits might be subtle or sex-specific.
Overall, our findings show that simply adding complexity to an enclosure isn’t enough to guarantee better welfare. It may be that lizards don’t perceive naturalistic and standard enclosures as very different, or that enclosure size matters more than what’s in it. For reptile owners and researchers alike, the take-home message is this: meaningful welfare improvements require us to think beyond aesthetics or what human caretakers assume is “good” or “natural”—we need to constantly evaluate our efforts and ask the animals themselves what they think.
Denommé, M and Tattersall, GJ. 2025. Influence of enclosure design on the behaviour and welfare of Pogona vitticeps. PLoS One 20(6): e0322682 https://doi.org/10.1371/journal.pone.0322682
A bearded dragon on top of cork bark. Photo credit Dr. Danilo Giacometti.
I am really proud to congratulate Dr. Danilo Giacometti for his successful PhD Defence! The thesis entitled “Physiological and behavioural responses to temperature and humidity in fossorial amphibians” was defended today in front of his examining committee: Dr. Don Miles (External, Ohio University), Dr. Toby Mündel (External within Brock University), Dr. Diane Mack (Chair, Brock University), Dr. Miriam Richards, Dr. Kiyoko Gotanda, and myself. A very large audience was in attendance for the entire defence (!). I wanted to thank our Brasilian colleagues who were able to log in and attend as well!
As the Arctic warms at an alarming pace, we’re learning that even cold-adapted species like the thick-billed murre aren’t immune to rising temperatures. This latest study, led by Fred Tremblay from Dr. Kyle Elliot’s lab at McGill adds to the growing understanding that cliff-nesting seabirds are experiencing heat stress far despite ambient air temperatures rarely exceeding 25°C. Using custom 3D-printed murre models painted to mimic the birds’ plumage, we measured “operative temperatures” (the actual heat experienced by an animal) on Coats Island, Nunavut. These operative temperatures soared as high as 46.5°C due to solar radiation and other environmental factors. In fact, murres faced heat stress conditions on 61% of summer breeding days, which can lead to significant water loss and physiological strain.
This work highlights the impact of climate change on Arctic wildlife and illustrates the value of biophysical modelling and how important it is to consider more than air temperature measurements in macroecology/macrophysiology (see https://doi.org/10.1111/1365-2656.12818 and https://doi.org/10.1002/ece3.5721).
These models, in combination with infrared thermal imaging, offer a non-invasive and cost-effective way to measure real-world thermal conditions, paving the way for better predictions of species vulnerability. With males incubating eggs during the hottest parts of the day, this heat stress isn’t just theoretical. It could shift breeding success, survival rates, and long-term population dynamics. These type of studies demonstrate the importance of microclimates in assessing the threats facing Arctic fauna and animals around the world.
Example thermal image of biophysical models and live thick-billed murres in the breeding colony at Coats Island, Nunavut, Canada. For each model and murres where at least 1/3 of the back is visible, the back area is indicated by the white perimeter with associated mean back temperature to the right.Graphical abstract of the study
For access to the study please follow the link in the citation below.
Citation
Tremblay F, Choy ES, Fifield DA, Tattersall GJ, Vézina F, O’Connor R, Love OP, Gilchrist GH, Elliott KH. 2025. Dealing with the heat: Assessing heat stress in an Arctic seabird using 3D-printed thermal models. Comp Biochem Physiol A Mol Integr Physiol. 306: 111880. https://doi.org/10.1016/j.cbpa.2025.111880
For amphibians, water is everything. Their thin skin makes them especially vulnerable to drying out, so staying hydrated is not just about comfort—it is about survival. But how do amphibians manage their hydration state in the face of different temperatures and fluctuating humidity?
Our recent study on spotted salamanders (Ambystoma maculatum) provides some new insights into this question. We exposed salamanders to two temperatures—17°C and 22°C—within a humidity gradient (Fig 1) to understand how salamanders behaved when given the choice to move toward more or less humid conditions under contrasting thermal conditions.
Figure 1. Schematic of the humidity gradient, showing how salamanders can freely move throughout a circular environment to select from low to high humidity.
We found that salamanders consistently selected localities in the gradient that maintained a constant vapour pressure deficit (VPD), which is the key variable driving evaporative water loss (Figure 2). VPD reflects a more physiologically relevant metric for the “drying power” of air. Since they behaviourally regulate a constant VPD regardless of temperature, this provides support for a humidistat (i.e., that they regulate their water loss).
Figure 2. Summary of the selected VPD and selected RH for spotted salamanders tested at 17 and 22C.
Virtually, what this means is that salamanders prefer higher relative humidity (RH) at 22°C than at 17°C to offset the increased drying power of the air at warmer temperatures. This suggests that salamanders are not just responding to RH or temperature independently. Instead, they are tuning into the combined effects that actually influence water loss.
Additionally, salamanders that selected higher VPDs (i.e., dryer conditions) lost more water, and body size also mattered, as larger individuals lost more water than smaller ones even after accounting for temperature. This highlights a trade-off between body size, humidity preference, and the risk of dehydration.
Temperature also played an important role in rehydration. Salamanders rehydrated faster at 22°C than at 17°C, suggesting that warmer conditions may boost water uptake—perhaps because of increased skin permeability at warmer temperatures, or from active processes that promote water uptake.
One of the most intriguing findings was the idea that salamanders might be able to sense how much water they are losing. We propose that local evaporative cooling of the skin—especially on the parts exposed to air—could serve as a sensory cue. If the dorsal skin is cooler than the ventral skin (which stays in contact with the moist substrate), that temperature difference might help the salamanders detect and respond to evaporative demand.
Overall, our study shows that rather than being passive victims of their environment, salamanders actively choose conditions that help them stay hydrated. Their behaviour is not random—it is a targeted response to complex environmental pressures.
One take home from this is that we can’t only measure relative humidity as an environmental predictor for microhabitat selection in salamanders and other ectotherms, but we need to incorporate the biophysical aspects of water loss. Hopefully this isn’t too scary!
Here’s Spotty! – All drought and no rain make salamanders insane.
Giacometti, D and Tattersall, GJ. 2025. Behavioural evidence of a humidistat: a temperature-compensating mechanism of hydroregulation in spotted salamanders. Journal of Experimental Biology, 250297 https://doi.org/10.1242/jeb.250297
Harry Kumbhani was representing the lab at the Canadian Society of Zoologists conference last week in Waterloo with his stunning poster below. And he received a little message, possibly from a journal editor encouraging he submit the manuscript, perhaps?!
Well done Harry and thank you for all your hard work on that project. Hopefully there will be good news on this soon as we finalise the manuscript.
Tattersall Lab (TEMP) 