Allyson Menzies: Exploring thermoregulatory strategies of sympatric species

Ally in the Yukon. Photo credit: Yasmine Majchrzak.
Ally in the Yukon. Photo credit: Yasmine Majchrzak.

Allyson Menzies, a Ph.D. candidate at McGill University, discusses her most recently accepted paper, “Body temperature, heart rate, and activity patterns of two boreal homeotherms in winter: homeostasis, allostasis, and ecological coexistence”, her interest in ecology, as well as the pros and cons of outdoor fieldwork.

About the paper

What’s your paper about?

In a sentence, it is about the extent to which sympatric species have similar or differentiated responses to shared environmental variation. We outfitted North American red squirrels and snowshoe hares, two herbivores that coexist and are active throughout the winter in the boreal forest, with animal-borne dataloggers to record activity, heart rate, and body temperature data in the field. We looked at activity, heart rate, and body temperature responses of both species, simultaneously, to variation in air temperature, photoperiod, and experimentally-manipulated resources.

What is the background behind your paper?

Organisms are often characterized and differentiated via broad and generalized categorizations (e.g., carnivore vs. herbivore, endotherm vs. ectotherm, predator vs. prey), and these can be somewhat oversimplified or restrictive. An example of this is the dichotomous categorization of endotherms (i.e., mammals and birds) as either heterothermic (i.e., labile and variable body temperature) or homeothermic (i.e., relatively stable body temperature). As more species are studied, in the field, in response to more forms of environmental and behavioural variation, it is becoming more apparent that even the species classically defined as homeotherms (stable, constant) exhibit variation in the level and precision of body temperature, and the traits that vary in order to regulate it. And, that this variation is environmentally responsive and likely adaptive. So, we selected two species that are functionally similar in many ways (i.e., intermediate-sized, winter-active, homeothermic, herbivores), but also different in more subtle ways (i.e., access to thermal refugia, resource availability in winter, predation pressure) to explore the ways in which behaviour, temporal niche partitioning, and a species’ natural history can influence, or be influenced by, the need to maintain warm and stable body temperature. The opportunity to quantify the functional trait responses expressed by coexisting species, experiencing same time, same place environmental variation, focuses the comparison on actual species differences, and provides insight into the more subtle forms of differentiation that shape the competitive interactions and coexistence of more similar species.

What are the key messages of your article?

A key message of the paper is that even species that are considered quite similar can differ in the ways they respond to and cope with environmental variation, and these more subtle forms of differentiation may be critical and underappreciated dynamics that shape competitive interactions and coexistence of coexisting species.

How is your paper new or different from other work in this area?

Two major advances of this stem from 1) the two species comparison, and 2) the continuous, fine-scale behavioural and physiological data that were collected in the field.

First, two-species comparisons have been criticized in the past but, the opportunity to quantify the functional trait responses expressed by coexisting species, experiencing same time, same place environmental variation, focuses any comparisons on actual species differences. And, here, we capture exactly that – simple and straightforward differences in the physiology and behaviour of co-existing species that allow them to maintain homeostasis amidst the cold, dark, resource-limited conditions of the boreal forest in winter.

Second, studies of metabolic variation and body temperature regulation have, traditionally, employed highly standardized, lab-based measures on animals confined to small chambers, or highly-controlled laboratory settings. While controlled environment studies on captive animals are foundational to the study of animal physiology and reveal cause-effect relationships between particular forms of environmental variation (e.g., temperature, humidity) and certain organismal traits, they inevitably incorporate only a subset of the many environmental stressors and organismal responses at play in fully free-ranging circumstances. For example, in most controlled environment studies, food is ad libitum, predators are absent, access to microenvironment variation or thermal refugia is limited, and opportunities to express behavioural flexibility are constrained. Relative to captive conditions, free-ranging animals are, in some ways, more constrained, including more food limited and predator exposed, but in other ways more flexible, including greater opportunity for behavioural variation. In this paper, using animal-borne dataloggers, including accelerometers and implantable dataloggers, we were able to collect continuous, fine-scale behavioural and physiological data from completely free-ranging animals as they experienced variation in daylight, predation pressure, temperature, snow conditions, interactions with other animals, and both natural and experimentally-manipulated resource levels.

Ally releasing a snowshoe hare. Photo credit: Ally's iPhone.
Ally releasing a snowshoe hare. Photo credit: Ally’s iPhone.

Does this article raise any new research questions?

One question that still lingers is ‘why’? What is the adaptive significance and/or potential performance consequences of variation in body temperature for homeotherms? In comparison to many other species, they do not show a great deal of body temperature variation, but squirrels were still different from hares and, presumably, for a reason. Why do hares defend such a high and invariable body temperature while squirrels do not? We can speculate and generate hypotheses based on comparative data and our understanding of the natural history and ecology of these species, but there isn’t much empirical or experimental data out there to confirm or refute these ideas. E.g., Would predator detection and digestion efficiency be negatively affected if hare body temperature was 1 or 2 degrees lower?

About the research

What is the broader impact of your paper?

Two things that working on this paper made me think about were: 1) the ways in which we categorize and differentiate species; we tend towards a simplified and, perhaps, reductionist categorization system but organisms are evidently much more complex than that, and 2) that organismal responses to environmental variation often involve a suite of morphological, behavioural, and physiological traits; so, truly understanding how organisms cope with environmental variation requires an understanding of these multi-trait responses (including physiology, which is often overlooked in ecological research), which are difficult to capture. 

Did you have any problems setting up the experiment or gathering your data?

Snowshoe hare being released from a trap. Photo credit: Symon Ptashnik
Snowshoe hare being released from a trap. Photo credit: Symon Ptashnik

Yes. We had two species outfitted with multiple dataloggers, one of which needed to be surgically implanted, and then we needed to recapture and retrieve these individuals in order to get the data. We also had to set up a food-supplementation experiment on a subset of the individuals and ensure that they were, in fact, consuming the food. At the same time, there were plenty of mammalian and avian predators around that regularly consume our study species. So, it was a bit stressful and, honestly, lucky that we were able to retrieve the number of dataloggers that we did, on both species, at the same time as our food-supplementation experiment was in effect.

Where you surprised by anything when working on it?

I am still surprised and impressed at the level and constancy of snowshoe hare body temperature. This species faces so many environmental stressors (i.e., predators, low quality food in winter, no refugia from the cold or predators) and, yet, they maintain such high body temperatures despite the energetic cost (they generally lose mass over the winter). They just have a tough life, with no breaks it seems.

What is the next step in this field going to be?

Something that would be really interesting to investigate into the future is the seasonality and cyclicity (particularly for snowshoe hares, in response to their population cycles) of their behaviour, physiology, and energy expenditure. How do each of these traits, the relationship among them, and the energetic consequences change depending on the season or the year. With biologgers, we now have the capacity to collect fine-scale behavioural and physiological data on species of all sizes, across time windows that would allow us to answer these types of questions and, in the long run, link organismal responses to short- and long-term environmental variation to ecological processes, like species co-existence.

About The Author

How did you get involved in ecology?

Winter scene in Kluane, Yukon. Photo credit: Allyson Menzies.
Winter scene in Kluane, Yukon. Photo credit: Allyson Menzies.

I always enjoyed being outdoors and loved animals as a kid, but it wasn’t until I was in undergrad that I discovered I could combine the two and make it a career. I approached a professor in my third year of my undergrad and asked if they needed help with summer field work, which was slightly out of character for me, as a shy and anxious human. But, they happened to be new and in the process of establishing a research program (… and maybe desperate), so they said yes. That summer, I got to catch bats, survey caves and mines, and spend the summer with interesting, smart, outdoorsy people. I could not believe I was being paid (an important detail – pay your technicians!!) to be outside and observe some of the most fascinating creatures in the wild. My mind was blown, and I was hooked. The rest is history.  

What are you currently working on?

I am currently wrapping up my PhD thesis – it is due in 1 week (HOORAAAAY!). Then, I will be applying for post doc funding and probably look into some non-academic positions to keep my options open and, hopefully, find the right career path for me.

What’s your current position?

I am currently a PhD candidate at McGill University.

What project/article are you most proud of?

At this point, I am just extremely proud of what I have accomplished throughout my entire academic career. Even the stuff that has never seen the light of day. So much work goes into every field season, lab experiment, draft of a paper, presentation, and meeting. Its hard to grasp when you’re in the thick of it, but being so close to the end of my journey as a student, I can look back and appreciate it more.

If I had to choose a specific project, it would have to do with my extra curriculars or volunteer hours. I love public outreach and attempting to make science more accessible to the general public, especially kids. One of the peak moments of my PhD was being featured, as a cartoon, in a children’s magazine (Les Explorateurs) alongside one of my colleagues.

What is the best thing about being an ecologist?

Being outside. All of the beautiful forests, mountains, lakes, and wildlife I have encountered along the way have provided me so much stress-relief, comfort, and space for self-reflection and self-realization. I have learned about, experienced, and observed the natural world in ways most people never get to and have gained an appreciation for how complex and astonishing it really is.

What is the worst thing about being an ecologist?

There are many job-like qualities to being an ecologist that are terrible (e.g., sitting at a desk for long hours, staring at a computer screen, demands of publishing, etc). But, I think a unique one to the job, aside from dealing with the elements (cold, wet, buggy, snowy, conditions) or the physical and mental exhaustion of field work, is the sacrifice that it takes. It can require you to be away from everyone and everything you care about for long periods of time, and there is often no way around it. Grad school, post-docs, field work can all be disruptive to your life and require you to be extremely mobile and flexible, which isn’t possible for a lot of people. I was fortunate enough to have an amazing support system both on campus and in the field, and the capacity to leave my city life for 6 to 8 months per year, but this is not always the case.

What do you do in your spare time?

I am really close with my family, so most of my holidays are spent travelling to see them. I also attempt to play the ukulele, sing, read books, and watch mind-melting TV and movies (I am taking recommendations for post-thesis life!).

One piece of advice for someone in your field…

I have two pieces of advice.

There is no such thing as not being smart enough to do this. Being smart enough, good enough, hard working enough is all relative and socially construed. Find what you are passionate about, what motivates you, and think about the impact you want to have on science/society. That’s what will make the hard days more manageable. I tell myself this at least once a day.

There are so many intelligent people out there doing cool research, find the ones that are also kind, compassionate, and share your priorities. And work with them. It’ll make your journey more fun.

Read Body temperature, heart rate, and activity patterns of two boreal homeotherms in winter: homeostasis, allostasis, and ecological coexistence in full her.

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