Month: May 2025

Under the Arctic Sun: Seabirds in the Heat of Climate Change

/ gtattersall

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

Hydro Hackers: How Salamanders Outsmart “the Drying”

/ gtattersall

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.

For more information, please access the study here: https://doi.org/10.1242/jeb.250297 and the Inside JEB write-up here: https://doi.org/10.1242/jeb.250813

Citation

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

Blog Author: Danilo Giacometti

Canadian Society of Zoologists Conference

/ gtattersall

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!

/ gtattersall

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!