Common Musk Turtles (Sternotherus odoratus) select habitats of high thermal quality at the northern extreme of their range

Picard, Gabriel; Carrière, M; Blouin‐Demers, Gabriel

doi:10.1163/017353710x541913

Cited by 30 publications

(18 citation statements)

References 31 publications

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“…Thermal quality is often one of the most important factors for habitat selection in ectotherms (Hughes and Grand 2000, Blouin-Demers and Weatherhead 2001, Monasterio et al 2009, Lelièvre et al 2011, Picard et al 2011, Halliday and Blouin-Demers 2016. Thermal quality is important for habitat selection in ectotherms because physiological performance (Huey 1991) and fitness (Huey and Berrigan 2001) are related to body temperature and because ectotherms use habitat selection to thermoregulate.…”

Section: Introductionmentioning

confidence: 99%

Density‐dependent habitat selection predicts fitness and abundance in a small lizard

Paterson

Blouin‐Demers

2017

Oikos

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Density‐dependent habitat selection has been used to predict and explain patterns of abundance of species between habitats. Thermal quality, a density‐independent component of habitat suitability, is often the most important factor for habitat selection in ectotherms which comprise the vast majority of animal species. Ectotherms may reach high densities such that individual fitness is reduced in a habitat due to increased competition for finite resources. Therefore, density and thermal quality may present conflicting information about which habitat will provide the highest fitness reward and ectotherm habitat selection may be density‐independent. Using ornate tree lizards Urosaurus ornatus at 10 sites each straddling two adjacent habitats (wash and upland), we tested the hypothesis that habitat selection is density‐dependent even when thermal quality differs between habitats. We first tested that fitness proxies decline with density in each habitat, indicating density‐dependent effects on habitat suitability. We also confirmed that the two habitats vary in suitability (quantified by food abundance and thermal quality). Next, we tested the predictions that habitat selection depends on density with isodar analyses and that fitness proxies are equal in the two habitats within a site. We found that monthly survival rates decreased with density, and that the wash habitat had more prey and higher thermal quality than the upland habitat. Lizards preferred the habitat with more food and higher thermal quality, lizard densities in the two habitats were positively correlated, and fitness proxies of lizards did not differ between habitats. These patterns are consistent with density‐dependent habitat selection, despite differences in thermal quality between habitats. We expect that density‐dependent habitat selection is widespread in terrestrial ectotherms when densities are high and temperatures are close to their optimal performance range. In areas where thermal quality is low, however, we expect that depletable resources, such as food, become less limiting because assimilating resources is more difficult.

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Section: Introductionmentioning

confidence: 99%

Density‐dependent habitat selection predicts fitness and abundance in a small lizard

Paterson

Blouin‐Demers

2017

Oikos

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“…Furthermore, G. polyphemus is never exposed to freezing temperatures, given this species' southern distribution and pattern of winter subterranean refuge use (DeGregorio, Buhlmann, & Tuberville, ). Conversely, S. odoratus is an aquatic turtle distributed throughout northern climates where they are likely exposed to more variable temperatures (e.g., Picard, Blouin‐Demers, & Carriere, ) and thus may be exposed to freezing or near‐freezing body temperatures. Thus, the differences in the ability of these two species to thermally acclimate immune function is likely either a result of present selection resulting from different thermal ecologies, phylogenetic constraints, or a combination of these factors, as organisms from thermally variable climates are more likely to acclimate more rapidly than animals from thermally stable climates (Angilletta, ).…”

Section: Discussionmentioning

confidence: 99%

Rapid thermal immune acclimation in common musk turtles (Sternotherus odoratus)

2019

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As infectious diseases in ectothermic vertebrates increasingly threaten wild populations, understanding how host immune systems are affected by the environment is key to understanding the process of infection. In this study, we investigated how temperature change and simulated bacterial infection (via lipopolysaccharide [LPS] injection) interacted to regulate innate immunity, as measured by bactericidal ability (BA), phagocytosis rate, and heterophil:lymphocyte ratio (HLR) in common musk turtles (Sternotherus odoratus). We found that LPS stimulated an acute immune response, as measured by an increase in BA, phagocytosis rate, and HLR. When exposed to a 5 or 10°C temperature change for 48 hr, turtles rapidly acclimated to the new temperature by adjusting their immune output. This acclimation was compensatory as seen by elevated rates of immune output in colder animals and decreased rates of immune output in warmer animals. These results indicate that while temperature change may be a constraint on some animals, S. odoratus have the ability to rapidly adjust immunity to match environmental thermal demand. This rapid ability to adjust immunity may be related to the broad geographic distribution of musk turtles. Future research should focus on how immune acclimation in ectotherms varies both intraspecifically and interspecifically across regional scales and geographic distributions.

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“…Turtles often respond to thermally heterogeneous environments by behavioral thermoregulation, including habitat selection to maximize heat gain (Dubois et al, 2009; Picard et al, 2011), alterations to activity timing and use of refuges in times of temperature extremes (Nieuwolt, 1996; Lagarde et al, 2012), and seasonal migration between areas differing in temperature (Swingland and Lessells, 1979). Given the variation in thermal characteristics of habitats at the fire-maintained site, we expected to observe strong links between seasonal habitat use and thermoregulatory behavior in T. carolina .…”

Section: Discussionmentioning

confidence: 99%

Thermal biology of eastern box turtles in a longleaf pine system managed with prescribed fire

Roe

Wild

Hall

2017

Journal of Thermal Biology

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Fire can influence the microclimate of forest habitats by removing understory vegetation and surface debris. Temperature is often higher in recently burned forests owing to increased light penetration through the open understory. Because physiological processes are sensitive to temperature in ectotherms, we expected fire-maintained forests to improve the suitability of the thermal environment for turtles, and for turtles to seasonally associate with the most thermally-optimal habitats. Using a laboratory thermal gradient, we determined the thermal preference range (Tset) of eastern box turtles, Terrapene carolina, to be 27 – 31 °C. Physical models simulating the body temperatures experienced by turtles in the field revealed that surface environments in a fire-maintained longleaf pine forest were 3 °C warmer than adjacent unburned mixed hardwood/pine forests, but the fire-maintained forest was never of superior thermal quality owing to wider Te fluctuations above Tset and exposure to extreme and potentially lethal temperatures. Radiotracked turtles using fire-managed longleaf pine forests maintained shell temperatures (Ts) approximately 2 °C above those at a nearby unburned forest, but we observed only moderate seasonal changes in habitat use which were inconsistent with thermoregulatory behavior. We conclude that turtles were not responding strongly to the thermal heterogeneity generated by fire in our system, and that other aspects of the environment are likely more important in shaping habitat associations.

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Common Musk Turtles (Sternotherus odoratus) select habitats of high thermal quality at the northern extreme of their range

Cited by 30 publications

References 31 publications

Density‐dependent habitat selection predicts fitness and abundance in a small lizard

Density‐dependent habitat selection predicts fitness and abundance in a small lizard

Rapid thermal immune acclimation in common musk turtles (Sternotherus odoratus)

Thermal biology of eastern box turtles in a longleaf pine system managed with prescribed fire

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