News and Events Relevant to the Lab
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.
Congratulations to Harry Kumbhani for being awarded an Ontario Graduate Scholarship for his MSc research in my lab. With coursework out of the way, conferences and summer field work beckon, so the timing could not be better!
Ectotherms from highly seasonal habitats often exhibit remarkable physiological plasticity, which allows them to balanceand adjust energy and water budgets in the face of fluctuating climatic conditions. Yet, fossorial (i.e., underground-dwelling) ectotherms are thought to experience attenuated climatic variability underground, raising the question: do fossorial ectotherms also display seasonal adjustments in key physiological functions?
In our recent publication, we investigated how seasonal acclimation (spring vs. autumn) affected energy expenditure and water loss in the spotted salamander. By measuring standard metabolic rates (SMR) and rates of evaporative water loss (EWL), we aimed to disentangle acute (i.e., exposure to test temperatures) from prolonged (i.e., seasonal acclimation) effects.
We found that increases in temperature led to increases in both SMR and EWL, demonstrating that fossorial salamanders also experience acute physiological costs when warmed. Salamanders had lower SMR in the spring, which may be beneficial in the context of overwintering emergence and breeding. In contrast, sustaining higher SMR in the autumn may allow salamanders to forage aboveground to replenish energy stores in preparation for the winter. EWL was stable between seasons, suggesting that salamanders may be more reliant on behavioural instead of physiological adjustments to manage water loss throughout the year. Together, our findings challenge the assumption that fossorial ectotherms are largely insulated from environmental fluctuations by virtue of living underground.
For more detailed information, you can access the full study here: https://doi.org/10.1007/s00442-025-05711-6
Citation
Giacometti, D, and Tattersall, GJ. 2025. Seasonal plasticity in the thermal sensitivity of metabolism but not water loss in a fossorial ectotherm. Oecologia. 207: 67. https://doi.org/10.1007/s00442-025-05711-6
A busy week with Honours student defences from the lab (and throughout the Department of Biological Sciences).
From our lab:
Margaret Kitney defended a brilliant thesis project on how and whether sex differences alters thermoregulatory behaviours in guppies (The effect of sex on the thermoregulatory behaviour of the Trinidadian guppy (Poecilia reticulata), having spent months watching fish swimming in shuttle boxes and months pouring over tracking algorithm detection processes. Truly a great amount of work and thought went into the thesis writing and explanations.
Natalie Bakker defended an awesome thesis project on bearded dragon cognition (Quantity Discrimination and Detour Task Performance of Bearded Dragons (Pogona vitticeps)), expanding our knowledge of how reptiles think and assess food resources. Months of challenges associated with our “lazy lizards”, but the project came together brilliantly in the end.
Congratulations to both!
For decades, the concept of a thermoregulatory “set-point” has been a cornerstone of physiological research, yet its definition and application remain surprisingly inconsistent across disciplines. Our recent study, spear-headed by the inimitable Dr. Duncan Mitchell, soon to be published in Biological Reviews, revisits and clarifies this fundamental concept by bridging perspectives from control theory and thermal biology. We explore how the set-point framework has been misinterpreted, and we argue for a more precise definition rooted in negative feedback principles. By revisiting foundational work and integrating recent empirical data, we demonstrate that set-points should not be conflated with operating body temperatures. Instead, they represent the thresholds at which thermo-effectors—such as sweating, shivering, or behavioural thermoregulation—are activated.
By incorporating an historical perspective, and combining control theory research with research into behavioural thermoregulation in lizards, our work highlights that, while lizards select body temperatures within a narrow range under stable conditions, their ability to do so is governed by multiple overlapping control mechanisms rather than a singular, static reference point.
This nuanced understanding has broad implications for comparative physiology and ecological research, especially in the face of climate change. The mischaracterization of set-points has led to confusion in both homeothermic and ectothermic species, potentially skewing interpretations of thermal adaptation and stress responses. By refining the definition of set-points within a rigorous control-theory framework, our study provides a clearer foundation for future research on thermal biology. We emphasize the importance of distinguishing between physiological thresholds and behavioral outcomes, urging researchers to adopt a systems-based approach to thermoregulation. Ultimately, our work seeks to reframe the discussion, ensuring that the next generation of studies can build on a more precise and unified conceptual framework.
This review is part of a series of “Misconceptions in thermal biology” papers, mainly from the Brain Function Research Group in South Africa, but the list of co-authors includes experts in thermal physiology and ecophysiology. Stay tuned for more papers in the future, and I encourage anyone new to thermoregulation and thermal biology research to read some of these.
Citation
Mitchell, D, Fuller, A, Snelling, EP, Tattersall, GJ, Hetem, RS, and Maloney, SK. 2025. Revisiting concepts of thermal physiology: understanding negative feedback and set-point in mammals, birds, and lizards. Biological Reviews. https://doi.org/10.1111/brv.70002
For other misconceptions in thermoregulation papers see:
Nest site selection is a critical decision for many animals, but for small carpenter bees (Ceratina calcarata), it’s a gamble with possibly far-reaching consequences. In our recent study, deHaan et al. explored the delicate balance between benefits and risks when mother bees choose to nest in sunny or shaded environments. The research uncovers an intriguing trade-off: while sunny nests boost maternal fitness by reducing the chances of complete brood failure, they come at the cost of smaller, thermally- stressed offspring. Thanks Mum!
Sunny nests, which are warmer, offer distinct advantages to mother bees. These nests enable earlier foraging activity and faster brood development, reducing the window of vulnerability to predators and parasites. To test this in an field experiment, however, we (i.e., Jessie deHaan) had to find nests early in the spring and relocate some nests to the shade and some to the sun to allow for these effects to be tested across the summer. Sunny nests reached maximum temperatures that were up to 3.8 °C higher than the maximum temperatures reached in the shade; further, the sunny nests would have been warmer for ~14-15 hours per day during the study period. In short, sunny nests are obviously warmer than shady nests, but also undergo wider diurnal changes in temperature.
In our experiment, we found that 59% of sunny nests successfully produced offspring, compared to only 32% of shaded nests. However, these sunnier sites posed challenges for developing juveniles, who faced higher temperatures that necessitated energy-intensive thermoprotective measures. Juveniles from sunny nests were smaller and had elevated heat tolerance thresholds (CTmax), suggesting they diverted resources from growth to survival. Since mothers provision each brood cell with a fixed amount of pollen after laying their egg, the size the young bees reach must reflect the trade-off between temperature-dependent energy expenditure and development. This trade-off also highlights how maternal decisions prioritize their own fitness, sometimes at the expense of their offspring’s long-term prospects.
This research sheds light on the intricate dynamics of environmental stress, maternal investment, and juvenile development in ectotherms like bees. With climate change amplifying temperature extremes, understanding these relationships could be crucial for predicting the future of pollinator populations.
This paper was the result of Jessie deHaan’s MSc research in Dr. Miriam Richards lab (co-supervised in part in my lab), but conducted during the lockdown period during the COVID-19 travel and research restrictions. At the time, faculty and student researchers were not permitted to come to campus, or initiate new research projects in the field (even though government scientists were allowed to carry on their research). For an MSc student in the middle of their research project, 2020 presented challenges to which Jessie rapidly adapted by running their experiments in their own backyard and in the basement of their house, using a modified PCR machine as the bee incubator! Hats off to ingenuity in the face of adversity.
Citation
deHaan, JL, Maretski, J, Skandalis, A, Tattersall, GJ, and Richards, MH. 2025. Costs and benefits of maternal nest choice: trade-offs between brood survival and thermal stress. Ecology. https://doi.org/10.1002/ecy.4525
See Dr. Miriam Richards lab page for more details about bees and her bee research!
Our latest study (https://doi.org/10.1016/j.applanim.2024.106484) sheds light on a perplexing behaviour seen in captive reptiles, namely their interactions with barriers (IWB), a form of repetitive behaviour akin to pacing in mammals. As part of her PhD research, Melanie Denommé investigated the motivations behind IWB in bearded dragons (Pogona vitticeps; Figure 1) over a three year period, and formally tested whether it stems from a “desire” to escape their enclosures.
Our findings revealed a strong preference for performing IWB near the front barrier of their environment (Figure 2), the only known escape route; even when half of it was obscured; they also direct more of their behaviour toward the transparent part of the front barrier. Interestingly, IWB was 15 times more likely to occur around the time when lizards defecated, supporting an argument that these behaviours may be driven by escape-related motivations, at least with respect the need to find suitable defecation areas. However, no clear link was found between IWB and anticipation of feeding, suggesting species-specific differences in how repetitive behaviours are triggered. Despite these results, lizards would still exhibit IWB with non-transparent barriers (Figure 2), suggesting that escape is not the exclusive explanation for these repetitive behaviours.
Seasonal and sex-related patterns offered further nuance. Contrary to expectations, female lizards performed IWB more during spring, while males showed consistent levels year-round. This might reflect frustrated breeding-season motivations, as females in the wild often roam widely in search of mates, a behaviour restricted in captivity. These findings emphasize the complex interplay between natural instincts and captive conditions, highlighting the importance of tailoring environments to better meet the needs of individual animals. By understanding these behaviours and using an evidence-based approach, we can deepen insights into the diverse causes of repetitive behaviours across species and thereby improve captive reptile welfare.
Note that the actual levels of IWB seen were low throughout the study, with numerous animals never performing the behaviour. There appear to be individual differences in the expression of IWB.
Citation
Denommé, M and Tattersall, GJ. 2025. Investigating the motivations of repetitive barrier interactions in Pogona vitticeps. Applied Animal Behaviour Science, 283: 106484. https://doi.org/10.1016/j.applanim.2024.106484
Shorebirds across Australia are experiencing notable changes in size and shape, offering a vivid example of climate change’s impact on wildlife. In a recent publication in Ecology Letters (McQueen et al), using comprehensive 46-year study involving over 200,000 observations across 25 species we show widespread declines in body size (“shrinking”) and concurrent increases in bill length (“shape-shifting”). These shifts appear to align with thermal adaptation, where smaller bodies and elongated bills would help dissipate heat more effectively in warmer environments. However, we also found that smaller species exhibited the most pronounced changes, while long-distance migratory species showed weaker trends, possibly due to physical constraints needed for efficient flight over vast distances.
Interestingly, while bill lengths have generally increased over time, they shortened following exposure to recent hot summers, hinting at complex evolutionary trade-offs between short-term vs. long-term climatic fluctuations. We suggest these changes may reflect not only adaptations for thermoregulation but also responses to nutritional stress or other environmental pressures. These findings emphasize the dual role of climate change as both a selective force and a stressor. As global temperatures continue to rise, understanding these morphological changes is crucial for predicting their effects on species survival and the ecosystems they inhabit.
To read more about the study, it in open access below.
Citation
A. McQueen, M. Klaassen, G. J. Tattersall, S. Ryding, Victorian Wader Study Group, Australasian Wader Studies Group, R. Atkinson, R. Jessop, C. J. Hassell, M. Christie, A. Fröhlich, M. R. E. Symonds. 2024. Shorebirds are shrinking and shape-shifting: declining dody size and lengthening bills in the past half-century. Ecology Letters. 27:e14513. https://doi.org/10.1111/ele.14513
Amphibians have long fascinated researchers due to their unique life cycles and environmental sensitivities, but many aspects about the biology of fossorial (i.e., burrowing) species remain shrouded in mystery. Fossorial amphibians like the Spotted Salamander (Ambystoma maculatum) spend most of their lives underground, emerging to the surface only briefly to breed or forage. In our latest paper, we address some of the intrinsic and extrinsic factors that may trigger emergence from overwintering by evaluating the interplay between temperature, gravity, and innate migratory cues over salamander behaviour.
Our study focussed on the role of soil temperature inversion—a seasonal shift where surface soils warm faster than deeper layers—in signalling salamanders to leave their winter refuges and begin their overland journey to breeding ponds. Using a vertical thermal gradient in the lab, we examined how salamanders responded to temperature cues at different depths and whether their activity levels changed with temperature shifts that mimicked soil temperature inversion. Our findings suggested that salamanders are not only tolerant of a wide thermal range but are also displaying a circannual phenomenon known as “migration restlessness”. Migration restlessness is characterised by a surge in movement often seen in animals preparing to migrate. Coupled with negative geotaxis, a tendency to move upward against gravity, this restless behaviour may explain why salamanders begin their spring migration at just the right moment, maximising their chances of reproductive success while avoiding the dangers of emerging too early and potentially freezing.
For a link to an interview with the first author ECR, Danilo Giacometti, please see the following link.
For a link to the paper, please see the citation below.
Citation
Giacometti D., Moldowan P. D., Tattersall G. J.; Ups and downs of fossorial life: migration restlessness and geotaxis may explain overwintering emergence in the Spotted Salamander. J Exp Biol 2024; jeb.249319. doi: https://doi.org/10.1242/jeb.249319
Blog Author: Danilo Giacometti
As global temperatures rise, animals are facing mounting pressure to adapt, and Australian birds are no exception. Our recent research (from Sara Ryding’s PhD research) has examined over 5,000 museum specimens, representing 78 bird species across Australia, revealing clear changes in their body and appendage sizes. These changes are aligned with two well-known ecological principles: Bergmann’s rule, which predicts smaller body sizes in warmer climates in endotherms, and Allen’s rule, which argues that animals (namely endotherms) will develop larger appendages to regulate body heat. Consistent with these theories, our study found that birds are experiencing a long-term decrease in body size, particularly in absolute wing length, while their appendages, such as bills and tarsi (leg bones), are getting larger relative to their bodies. This phenomenon, often referred to as “shape-shifting,” is a widespread response to the increasing temperatures driven by climate change.
Interestingly, our research also highlights a more complex picture when it comes to short-term responses. While long-term trends show a clear increase in appendage size to aid thermoregulation, birds displayed smaller appendages in the years following hotter temperatures. This suggests that while birds are gradually adapting to rising temperatures over time, short-term weather events may create different selection pressures that affect growth and development. Factors like food availability and reproductive challenges could contribute to these opposing trends. This study underscores the intricate balance between long-term evolutionary changes and the immediate pressures exerted by fluctuating environmental conditions, offering critical insights into how birds—and potentially other animals—might continue to respond to our rapidly changing world.
For a link to the study, please see the citation below.
Citation
Ryding, McQueen, A, Klaassen, M, Tattersall, GJ, and Symonds, MRE. 2024. Long- and short-term responses to climate change in body and appendage size of diverse Australian birds. Global Change Biology, 30:e17517. https://doi.org/10.1111/gcb.17517
Tattersall Lab (TEMP) 