Caleb Loughran, WNMU assistant professor of biology, has studied rattlesnakes and lizards and how they respond to heat as the climate continues to warm up. He spoke with KRWG's Susan Morée about his research and what he's hoping to investigate in the future to learn about how reptiles can handle climate change.
Susan Morée:
So Caleb, you have been doing research on snakes and you learned, I understand, about dramatic temperature swings for snakes. Is that correct?
Caleb Loughran:
Yes, more specifically, I was interested in how snakes select their body temperature because, as reptiles, they are regulated by selecting different environments so their body temperature can match the environmental temperature. So, I was curious how they were selecting their body temperatures used in different environments, and I was especially interested in how this varied among individuals within a group of snakes. So, I did a research project that involved comparing the temperature preferences of small snakes like babies and juveniles versus large adult snakes that get over three to four feet long.
Susan Morée:
And how does that research in the Pacific Northwest, does it translate to rattlesnakes and other types of snakes in the Southwest?
Caleb Loughran:
I certainly believe that it does. The specific project I did has never been done on any of the rattlesnakes in the Southwest. The same idea certainly applies. So the idea of the project that I did was to, like I said, was to... compare like the thermal preferences of the small snakes versus these large snakes and the main idea driving that was that small snakes are going to heat up and cool down at a much more rapid rate than large snakes will. Whereas large snakes will spend more time basking and absorbing heat and then they will retain heat for a longer period of time. So, consequently that will influence how much time they spend in hot areas versus cold areas and what shorter body temperature that they might seek So this idea was tested on northern Pacific rattlesnakes, but based off of the results that I found and the sort of environments that those snakes occupy, I imagine that we would probably see similar patterns in rattlesnakes in the southwest.
Susan Morée:
And what about climate change? Do you think that is affecting rattlesnakes and/or other snakes in the Gila?
Caleb Loughran:
That's a big unknown. So climate change certainly has been a main concern for a lot of many organisms, including reptiles. And there's been a lot of research that has gone into either measuring or trying to predict what the effects of climate change are. So it's hard to, it's really hard to predict what is and what specifically will happen with snakes because not a lot of primary research has been done on the effects of climate change on snakes. But the main idea of how climate change will affect a lot, many different reptile species is that as temperatures increase for longer periods and stay, get hotter and stay hotter, for longer periods throughout a given day, it truncates the ability for snakes, or really reptiles more broadly, it truncates their time available to be active and to forage and to search for mates, search for suitable habitat, and then be active in that suitable habitat. So this idea has been explored extensively with lizards, and there's been a lot of a lot of research that has looked at the finer nuances that might be constraining or opening up opportunities for different lizard species. This hasn't been tested as much with snakes, certainly not rattlesnakes, and so that's a major unknown, and that's an area of research I'd like to explore. And as far as this research paper that I recently published went, I did a speculative model that estimates activity time in different conditions for snakes and how long they can be out in the open before they have to retreat. And back to this question of body size and how body size might affect how they are using their environment and how they are thermo regulating. What the model predicted is that small bodied snakes are going to have a much more extreme truncation in their activity periods. So that might suggest that they're going to heat up potentially quicker and there's going to be a longer period of potentially lethal temperatures on the landscape. They may have a more difficult time in being active and essentially being able to grow, being able to forage and eventually reach adulthood. So I want to emphasize that this was just a model, and that simply was a heuristic exercise, but that's what, based off of the data I collected, that's what the model might suggest. So this has downstream effects for their ecology and their physiology and how they use the lens. So some of the questions that I'm really interested in exploring is to focus on some of these snake species in the Gila.
Susan Morée:
People don't always like rattlesnakes, right? And a lot of people are just simply afraid of snakes. Can you talk about why their presence is important in the environment?
Caleb Loughran:
Snakes are just a really important part of any ecosystem. They're an important predator. They're also an important prey species for many different things, many different other things. So they are a critical part of the food web, in terms of being both predator and prey. Although rattlesnakes can be dangerous, I always like to tell people that many animals can be dangerous. But the reality is that rattlesnakes in particular are typically very shy and like to be left alone. Everything about their affect is to stay hidden or to warn you to stay away when they are. So, they don't want to attack you. In fact, they really want to be left alone. And so, they're not as...So any rattlesnake encounters that someone might happen are almost always going to be avoidable. So I always encourage people, if they do encounter a rattlesnake and they're not so sure about it, just to give it its space and to leave it alone and to not approach it, because the snake is also wanting to be left alone and it doesn't want to bite anybody. It wants to save its venom for prey items.
Susan Morée:
I imagine snakes help, or especially rattlesnakes, help to keep the rodent population down in the wild. Is that true?
Caleb Loughran:
That's certainly true. So yeah, there's many snakes that are predators of rodents, and not the least of which are rattlesnakes. And rattlesnakes can sometimes occur in fairly high densities. And even though an individual snake might only eat one rodent every one to two weeks, if there's a high enough population of rattlesnakes, that can actually have, that can potentially have even more of a top-down predation effect on many rodent species than just maybe a single, like a single predator like a bob cat or coyote might have. So rattlesnakes are certainly not the only predators of rodents, but they are an important predator of rodents.
Susan Morée:
And you've also done some research on lizards, correct?
Caleb Loughran:
That is correct. That was what I did for my PhD at the University of New Mexico.
Susan Morée:
And what did you find out about lizards?
Caleb Loughran:
And so when going on this theme of climate change and how it's going to affect different reptile communities, what I was interested in this project on lizards is how can lizards tolerate prolonged, extreme, intense heat? Because snakes will typically go and hide under bushes and in holes when things get hot, and are only active when conditions are more optimal, whereas lizards will come out and be in the open heat for longer periods of time, but like I said earlier, they also are constrained by conditions being too hot for too long that they might have to retreat, and so my question was, can lizards potentially tolerate prolonged, extreme, intense heat by panting? So, like a dog might pant, but lizards are known to open their mouths to use evaporative cooling to evaporate water to try to cool down like we humans sweat. It's a thermo regulation mechanism. What was unknown is if this was how many different lizard species actually used this as a thermo regulation mechanism, if it was a feasible thermo regulation mechanism, and how costly it was to their energy and their water balance. So the work that I did on that was to measure the response of a number of different lizard species native to Arizona and New Mexico and measure metabolic rate and evaporative water loss rates before the onset of panting and then after they started panting, how much did their body temperature decrease below air temperature, and as their body temperature decreased below air temperature, how much did that cost them in their overall water budget? So that was the main project, or that was the main idea of the project that I did for that. And that was, like I said, at the University of New Mexico, on a lot of different native species here. And what I found in there is that many lizards actually do, will initiate panting as temperatures increase. But many lizards are very ineffective at panting and are likely to just end up retreating to cooler refuges, if possible, in their habitat. There were a few species that actually could sit very effectively and pant and evaporate water and lower their body temperature quite substantially, but this was very costly to their overall water budget. So the kind of unknown is right now is what are these lizards going to actually do in nature. We can predict that species that are not effective at panting are likely going to be very constrained by the increase in temperature, especially during heat waves, when we have two or three-week long heat waves, those lizards are likely going to have to retreat into thermal refuges to stay hidden and avoid the heat. There may be some lizard species that can try to be active for longer periods of time, but again, that's a very costly prospect to them, and it's only a worthwhile endeavor if they can replenish that water that they lost. So, the idea is that they might be able to come out and intermittently pat at a low intensity if conditions are such that they can spend an extra, 10 minutes, 20 minutes or more, just out getting a few extra food items, a few extra bugs, or defending their territory for just a little while longer. That might not seem like much, but it might be the sort of thing that gives them just a competitive edge. And so species that are able to do this might not be able to tolerate the very intense heat during heat waves for longer periods of time, like say in lowland deserts. But those species might be able to do all right and use panting as a mechanism. In areas where maybe it's slightly, slightly cooler, slightly higher elevation, so what happens in nature is really unknown and is an important gap in our knowledge. But the data I collected was the basic physiology of quantifying what lizards are capable of and what it costs them.
