An Examination of Limiting Factors of Chrysemys picta bellii (Western painted turtles) in the Lower Willamette River Basin, Oregon

Oregon’s two native freshwater turtle species, Chrysemys picta bellii (Western painted turtle) and Actinemys marmorata (Northwestern pond turtle), have seen significantly reduced population sizes since the founding of Portland in 1845, with estimates of up to 90% for A. marmorata. This project examined turtle nesting activity at 25 sites across a range of turtle populations and habitats around the Lower Willamette River Basin. All discovered turtle nesting activity was found in areas of high solar exposure. We found 93% of over 400 nest attempts to have been depredated across the 25 sites, well above most other reported rates. At several sites, many aborted nest attempts were found atop gravel roadbeds, indicating that lack of appropriate substrate is potentially limiting nesting success. The presence of greater than five pedestrians per hour at turtle nesting areas was correlated with a substantial decrease in nesting attempts suggesting that management of recreational activities may play a role in the amount of nesting activity occurring. Hence, site-specific solutions, such as importing substrate, alteration of path locations or seasonal trail closures to lessen human foot traffic disturbance of turtle nesting attempts, are likely to improve recruitment rates of native turtles in the Lower Willamette Basin. Further studies that improve knowledge of population demographics, the impact of human activities on turtles, and habitat needs of juvenile turtles are needed to support long-term self-sustaining turtle populations.

Cold-acclimation induces life stage-specific responses in the cardiac proteome of Western painted turtles (Chrysemys picta bellii): implications for anoxia tolerance

Western painted turtles (Chrysemys picta bellii) are the most anoxia-tolerant tetrapod. Survival time improves at low temperature and during ontogeny, such that adults acclimated to 3oC survive far longer without oxygen than either warm-acclimated adults or cold-acclimated hatchlings. Since protein synthesis is rapidly suppressed to save energy at the onset of anoxia exposure, this study tested the hypothesis that cold-acclimation would evoke preparatory changes in protein expression to support enhanced anoxia survival in adult but not hatchling turtles. To test this, adult and hatchling turtles were acclimated to either 20oC (warm) or 3oC (cold) for 5 weeks, and then the heart ventricles were collected for quantitative proteomic analysis. The relative abundances of 1316 identified proteins were compared between temperatures and developmental stages. The effect of cold-acclimation on the cardiac proteome was only evident in the context of an interaction with life stage, suggesting that ontogenic differences in anoxia tolerance may be predicated on successful maturation of the heart. The main differences between the hatchling and adult cardiac proteomes reflect an increase in metabolic scope with age that included more myoglobin and increased investment in both aerobic and anaerobic energy pathways. Mitochondrial structure and function were key targets of the life stage- and temperature-induced changes to the cardiac proteome, including reduced complex II proteins in cold-acclimated adults that may help down-regulate the electron transport system and avoid succinate accumulation during anoxia. Therefore, targeted cold-induced changes to the cardiac proteome may be a contributing mechanism for stage-specific anoxia tolerance in turtles.

Skeletal Muscle Histidine Containing Dipeptide Contents are Increased in Freshwater Turtles (Chrysemys picta bellii) with Cold-Acclimation

Freshwater turtles found in higher latitudes can experience extreme challenges to acid-base homeostasis while overwintering, due to a combination of cold temperatures along with the potential for environmental hypoxia. Histidine containing dipeptides (HCDs; carnosine, anserine and balenine) may facilitate pH regulation in response to these challenges, through their role as pH buffers. We measured the HCDs content of three tissues (liver, cardiac muscle and skeletal muscle) from the anoxia-tolerant painted turtle (Chrysemys picta bellii) acclimated to either 3 or 20 C. HCDs were detected in all tissues, with the highest content shown in the skeletal muscle. Turtles acclimated to 3 C had more HCD in their skeletal muscle than those acclimated to 20 C (carnosine = 20.8 +/- 4.5 vs 12.5 +/- 5.9 mmol/kg DM; ES = 1.59 (95%CI: 0.16 - 3.00), P = 0.013). The higher HCD content observed in the skeletal muscle of the cold-acclimated turtles suggests a role in acid-base regulation in response to physiological challenges associated with living in the cold, with the increase possibly related to the temperature sensitivity of carnosine's dissociation constant and buffering power of the skeletal muscle during anoxic submergence.

Cold-acclimation induces life stage-specific responses in the cardiac proteome of Western painted turtles (Chrysemys picta bellii): implications for anoxia tolerance

Western painted turtles (Chrysemys picta bellii) are the most anoxia-tolerant tetrapod. Survival time improves at low temperature and during ontogeny, such that adults acclimated to 3°C survive far longer without oxygen than either warm-acclimated adults or cold-acclimated hatchlings. Since protein synthesis is rapidly suppressed to save energy at the onset of anoxia exposure, this study tested the hypothesis that cold-acclimation would evoke preparatory changes in protein expression that would support enhanced anoxia survival in adult but not hatchling turtles. To test this, adult and hatchling turtles were acclimated to either 20°C (warm) or 3°C (cold) for 5 weeks, and then the heart ventricles were collected for quantitative proteomic analysis using labeled isobaric tags and mass spectrometry. The relative abundances of 1316 identified proteins were compared between temperatures and developmental stages. The effect of cold-acclimation on the cardiac proteome was most evident when life stage was included as a covariable, suggesting that ontogenic differences in anoxia tolerance may be predicated on successful maturation of the heart from its hatchling to adult form and, only after this maturation occurs, will cold-acclimation induce protein expression changes appropriate for supporting heart function during prolonged anoxia. The main differences between the hatchling and adult cardiac proteomes reflect an increase in metabolic scope that included more myoglobin and increased investment in both aerobic and anaerobic energy pathways. Mitochondrial structure and function were key targets of life stage- and temperature-induced changes to the cardiac proteome, including reduced complex II proteins in cold-acclimated adults that may help down-regulate the electron transport system and avoid succinate accumulation during anoxia. Therefore, targeted cold-induced changes to the cardiac proteome may be a contributing mechanism for stagespecific anoxia tolerance in turtles.

Spatial ecology and multi-scale habitat selection by Western Painted Turtles (Chrysemys picta bellii) in an urban area

As urban centres expand, knowledge on the habitat and space use of native wildlife, particularly long-lived species, is required for proper management. Our objective was to understand space requirements and key habitat features necessary for long-term persistence of Western Painted Turtles (Chrysemys picta bellii) living in a Canadian urban park. Using radio telemetry, we examined seasonal habitat selection and space use over two years, 2015–2016 (n = 23), and 2016–2017 (n = 29) in Regina, Saskatchewan. Daily movements and home ranges of males and females were smaller during emergence than during nesting or post-nesting phases of the active season. Turtles inhabiting marsh sites had 2- and 4-times larger daily movements and home ranges compared to turtles inhabiting the creek. Turtles selected the shoreline habitat over urban/parkland and open water. Turtles used marsh-shoreline habitats non-randomly, selecting accessible shoreline with large trees in the active season. In contrast, turtles used creek-shoreline habitat according to availability. Overwintering sites selected by turtles were warmer and deeper than random available sites, with no difference in dissolved oxygen level. However, water was hypoxic for most overwintering sites. Our results show that turtles range widely, requiring 20–60 ha throughout the year. Urban park areas should be managed to provide accessible shorelines with a combination of cover and open basking areas. Critically, careful attention needs to be paid to managing water depth so that over-wintering sites remain viable.

Comparison of Two Escapement Designs for Western Painted Turtles Captured in Modified Fyke Nets

Altering sampling methods to reduce bycatch during fish population sampling can introduce biases that affect the capture of target species. Therefore, understanding bycatch reduction devices and how they affect fish sampling is important. Our goal was to test two potential escapement designs intended to reduce bycatch of western painted turtles Chrysemys picta bellii during freshwater-fish population assessments with modified fyke nets. Design A tested an escapement flap on the interior of the modified fyke net and design B tested an escapement throat on the exterior of the modified fyke net. We completed 4-h and 24-h trials for turtle escapement to determine the effectiveness of each design for reducing turtle bycatch. We also simulated fish population assessments to determine the escapement of fish and turtles from each design. Turtles escaped from each design with mean escapement rates during the 4-h and 24-h trials of 71.1% and 63.8% from design A and 55.6% and 50.0% from design B, respectively. In the fish population assessment simulation we observed a mean escapement rate of 49% for turtles from design A, but a mean escapement rate of only 11% from design B. Species-specific escapement rates were observed for fish in both designs. Significant differences in the size structure of some species were observed. Escapement rates from design A were likely underestimated for most species captured due to movement of fish and turtles from the holding pen back into the fyke net. Based on our results, we do not recommend either design to reduce bycatch of turtles during fish community sampling without substantial refinement of the designs. Further research is needed to identify alternative methods for reducing turtle bycatch mortality.