Conservation Physiology最新文献

In the field of conservation physiology, there is often a trade off between conducting research in controlled laboratory settings or in inherently variable field environments. However, this belief sets up a false dichotomy where laboratory experiments are perceived as providing precise, mechanistic understanding with low variability at the cost of environmental realism while field studies are ecologically relevant but criticized for generating inconsistent evidence that is difficult to interpret and replicate. Despite the perceived binary view, these approaches are not in opposition to one another, but rather form a continuum along increasing ecological complexity. Here, we argue that it is possible to mindfully and purposefully design studies and develop integrative collaborations in conservation physiology that span the lab-field continuum to address pressing environmentally-relevant questions that can be used to inform policy and practice. We first outline the advantages and disadvantages of different approaches to knowledge generation. We then highlight ways to bridge the lab-field divide though leveraging the advantages provided by different approaches to build a more comprehensive understanding of the natural world, including how recent technological advances can help connect lab- and field-based research. Next, we discuss the importance of partnership and collaboration across sectors for informing our understanding of ecological patterns and physiological processes. Finally, we reflect on how to best translate physiological research into action and the reciprocal role that environmental practitioners can have in driving research questions in conservation physiology.

Freshwater environments are experiencing rapid changes in seasonal temperature and water flows that could impact threatened aquatic species. Environmental stressors experienced by mothers can influence the size and quality of fish eggs creating downstream effects on larval fitness. Cool water fish species like Pacific salmon with extended periods of embryonic development may be especially vulnerable to changing environmental conditions. To gain insight into the factors influencing embryonic physiology in fish, the relationship between parental genetics, egg size and embryo metabolism was examined in developing Chinook salmon (Oncorhyncus tshawytcha) and pink salmon (Oncorhyncus gorbuscha) embryos, as these species exhibit distinct differences in egg size and life history strategies. Egg size was found to have a relatively limited effect on embryo metabolism with parental genetics having a larger effect on the embryos of these species. Maternal genetics influenced embryonic metabolic rate more in the early stages of development than at later stages of development. These findings suggest that parental genetics or epigenetics is a key factor determining the metabolic rates of salmon embryos and that genetics should be considered when seeking to understand how environmental change will impact threatened fish species, like Pacific salmon.

Sea turtle health assessments can be strengthened by developing conserved biomarkers that discriminate between healthy and diseased states. Serum amyloid A, myeloid-related protein 126 and cardiac troponin C (CTNC) were explored as potential biomarkers of sea turtle health. Plasma concentrations initially quantified using a targeted SPARCL™ assay significantly differed between moribund (n = 15) and recovered (n = 5) loggerhead turtles (Caretta caretta). There was a negative correlation between myeloid-related protein 126 and packed cell volume (r = -0.612, P = 0.005) and total solids (r = -0.497, P = 0.03) and between and Fulton's body condition index (r = -0.684, P = 0.001). Serum amyloid A showed a relatively high interquartile range (IQR) in moribund turtles and no significant correlations with clinical parameters. Myeloid-related protein 126 and cardiac troponin C were further evaluated by an enzyme-linked immunosorbent assay in a larger dataset of loggerhead, Kemp's ridley (Lepidochelys kempii) and green (Chelonia mydas) turtles. Plasma myeloid-related protein 126 was significantly lower in captive healthy (n = 7) and recovered (n = 23) turtles than in moribund (n = 25) and nesting green (n = 58) turtles. Green turtles with fibropapillomatosis (n = 10) were not significantly different from any group. Discriminating values between healthy/recovered and moribund turtles were 1.89 and 1.97 ng/ml by receiver operating characteristic and logistic regression analyses, respectively. Myeloid-related protein 126 decreased in successfully rehabilitated turtles (n = 18 turtles; n = 67 blood samples) and was negatively correlated with body condition score (r = -0.672, P < 0.001) and packed cell volume (r = -0.443, P = 0.009). Cardiac troponin C was significantly higher (P = 0.049) in moribund turtles (n = 16) compared to healthy/recovered turtles (n = 7) and in moribund samples (n = 11) compared to recovered samples (n = 11) in serially sampled turtles (P = 0.015), but was not predictive of health status. Myeloid-related protein 126 represents a strong biomarker candidate in sea turtles. Cardiac troponin C warrants further evaluation in a larger dataset and serum amyloid A requires examination of variables affecting pathophysiologic responses in sea turtles.

Invasive species can alter the ecology of protected areas, substantially lowering the habitat quality for vertebrate communities. The Lower Imenti Forest on Mt. Kenya's northeastern slope has experienced habitat disturbance, degrading the system and resulting in the establishment of invasive species, including lantana (Lantana camara), throughout the area. Following reports of high mortality and poor conditions among the African savanna elephants (Loxodonta africana) inhabiting the area, we assessed the status of two endocrine indicators of their physiological condition. Specifically, we assessed the physiological stress response by measuring faecal glucocorticoid metabolites (fGCM) and the nutritional stress response by measuring faecal thyroid (fT3) concentrations in elephant faecal samples collected in the forest. To better interpret the hormone levels, we compared the hormone concentrations in the Imenti faecal samples to concentrations from reference levels indicative of extreme nutritional stress (from faecal samples of elephants experiencing drought-induced mortality) and adrenal stress (from elephants experiencing high levels of human-elephant conflict). The concentrations of fT3, a biomarker of nutritional stress response, found in elephant faecal samples from the Lower Imenti Forest were lower than the drought-stressed reference levels, suggesting lower levels of energy intake and assimilation of forage resources in elephants from this area. The concentration of fGCM, a biomarker of physiological stress response, was higher than the human-elephant conflict reference levels, suggesting the elephants in Lower Imenti were experiencing a higher physiological stress response. We found no differences between fT3 and fGCM concentrations in samples assigned to different age classes (juvenile, subadults, adults), suggesting the physiological problems were not age specific. Findings from our physiological study suggest that restricted movement and reduced forage availability due to lantana infestation in the Lower Imenti Forest may be driving the elevated nutritional stress, potentially contributing to the concerning mortality observed in the area. We discuss the use of endocrine markers to ascertain wildlife responses to degraded habitats.

As wildlife increasingly has to face levels of environmental conditions that go far beyond normal ranges, understanding the ecological and evolutionary dynamics behind such extreme scenarios becomes essential for animal conservation. Here, we discuss the eco-physiological singularities of wildlife coping with extreme conditions. We first discuss the conditions under which scenarios can be considered 'extreme'. This includes distinguishing the nature of natural and anthropogenic disturbances, considering aspects such as their intensities, as well as the understanding of species biology and evolutionary history. To exemplify the diversity of wildlife responses to extreme conditions, we highlight five different representative study cases (two with natural causes, three of anthropogenic origin): birds at high altitude, fish in geothermal habitats, birds in pesticide-laden farmlands, invertebrates in urban ponds, and amphibians in radioactive zones. These examples illustrate the diverse physiological and ecological responses to extreme factors, emphasizing the complexity of wildlife adaptation under different scenarios. However, they also reveal significant knowledge gaps regarding long-term effects of responses to extreme environments, and the mechanistic basis behind these processes. Future research should ideally include long-term approaches making use of validated physiological markers of individual, population or species health or fitness. This information could be then incorporated into mechanistic models like Species Distribution Models (SDMs) to predict species geographic occurrence and the impact of future extreme scenarios. Such holistic and integrative physiological approaches will enhance our understanding of species and population resilience, and will facilitate the identification of vulnerable populations, ultimately improving management strategies. By prioritizing these research efforts, we will better anticipate the impacts of environmental changes on wildlife health, and thus improve biodiversity conservation strategies.

Rivers, lakes, and wetlands are facing threats that continue to grow in intensity and frequency from climate change, habitat fragmentation, invasive species, changes in food availability, natural disasters, various forms of pollution (e.g., trace metals, light, noise), and emerging infectious diseases. These disruptions to freshwater environments are driving population declines in freshwater fishes as well as threatening migratory species that need freshwater habitats to complete their life cycle. To improve freshwater fish conservation efforts, it is essential to understand the magnitude and nature of the threats fish are currently facing. Here, we present a series of case studies that illustrate the utility of employing physiological methods to assess both the threats facing freshwater fishes, and the conservation efforts being used to help preserve freshwater biodiversity. We present an array of physiological tools that can be used across multiple levels of biological organization, from molecular to population-level, to address a variety of questions. Finally, we share what we view to be pressing questions in freshwater fish conservation physiology and highlight strategies to help bridge gaps across different user groups.

The prevailing shark nursery paradigm suggests that high survival in these habitats is primarily driven by reduced predator encounters: so-called pre-encounter risk. In this study, we propose an alternative or complementary mechanism: that some nurseries may lower post-encounter risk by providing environmental conditions that maximize escape performance. To test this hypothesis, we examined how temperature, depth and habitat complexity influence the escape performance of newborn blacktip reef sharks (Carcharhinus melanopterus) in Mo'orea, French Polynesia. In a controlled setting, we exposed 48 newborn sharks to four temperature treatments (25, 27, 29 and 31°C) and measured fast-start acceleration, turning rate and latency to respond to a stimulus. We also calculated aerobic scope at 27, 29 and 31°C, as greater aerobic scope is associated with faster recovery from burst swimming. Our results show that warmer temperatures improve escape performance, with 29% higher acceleration, 9% faster turning rates and 48% shorter reaction times at elevated temperatures. Furthermore, aerobic scope remained ≥80% of its maximum capacity between 27.5 and 30.8°C, suggesting that newborn sharks can sustain high metabolic performance within this thermal window. Field measurements at nursery habitats revealed that daily thermal fluctuations generally remained within this optimal aerobic scope range, meaning that newborns can maintain high escape performance for most of the day. Additionally, high-resolution mapping confirmed that previously reported home ranges were associated with shallow (median depth = 0.74 m), structurally complex reef flats dominated by coral substrate. The combination of reduced hydrodynamic drag in shallow water and increased manoeuvrability in complex habitats likely enhances predator evasion. However, extreme warming events that exceed critical thermal limits may trigger behavioural trade-offs that compromise escape performance and elevate predation risk. Our findings suggest that these nurseries provide habitat-specific advantages for predator evasion, reinforcing their critical role in the survival of newborn sharks.

Reproduction is the most energetically costly undertaking for female mammals and for capital breeders. Understanding factors that influence individual body condition and reproductive success is essential to understanding population demography. We investigated long-term trends in pregnancy rates to assess the impacts of individual and environmental factors on polar bear reproduction. Pregnancy status was determined from serum progesterone levels in blood collected from free-ranging polar bears captured on shore in late summer to early autumn in western Hudson Bay, Canada. We analysed 541 blood samples for progesterone level from 441 individuals from 1991 to 2021 and compared to data from 1982 to 1990 (354 individuals from 476 occasions). We used a generalized linear model to investigate individual and environmental factors that could influence pregnancy rates. The percent of solitary females that were pregnant declined significantly over time and between time periods from 85% in 1982-90 to 73% in 1991-2021. Interannual variation in pregnancy was high, ranging from 46 to 100%. Pregnancy rates were influenced by mass and age, with higher pregnancy rates for heavier females and those >4 and <24 years old. The percentage of pregnant 4-year-old females declined from 82% in 1982-90 to 55% in 1991-2021. The mass of pregnant females declined over time and the lightest pregnant female known to have produced cubs weighed 196 kg in the autumn. We suggest further research is needed to understand mechanisms resulting in pregnancy rate variation, which may be related to previous reproductive status and recent litter loss.

Our planet is experiencing sudden and unpredictable changes that affect most land and marine environments. We investigated blood analytes relevant to nutritional biochemistry and isotopic signatures of adult female California sea lions (CSL) from the Gulf of California, an area that has suffered changes in sea surface temperature in the past decades. During the 2016 and 2020 breeding seasons we collected fur, plasma and serum samples from apparently healthy adult female CSL (2016, n = 43; 2020, n = 12). We determined packed cell volume (PCV) and quantified 11 blood analytes directly or indirectly related to nutrition (albumin, cholesterol, triglycerides, glucose, total protein, globulin, creatinine, ferritin, iron, zinc and bilirubin). We also determined carbon and nitrogen isotopic signatures in the fur. Most analytes from 2020 were within the ranges reported for free-ranging CSL, while various analytes from 2016 deviated from reported ranges. Cholesterol, albumin, A:G ratio and zinc were higher in 2020, and glucose and total bilirubin were higher in 2016. Cholesterol and glucose varied across ecological regions. Isotopic values varied between sampling years, while trophic level and δ¹⁵N varied across regions. The δ¹³C values were related to blood glucose, while trophic level was related to cholesterol. These results may reflect dietary changes, as supported by isotopic signals. The variations in some of the blood analytes suggest short-term stressors or slight differences in sampling season, while others may reflect metabolic compensation of foraging effort, malnutrition or subclinical shifts in health. We generated reference data of the blood analytes for wild adult female CSL. By integrating clinical and ecological indicators, our approach offers a tool for early detection of subclinical metabolic and dietary shifts relevant to health and population viability. This is valuable for the conservation and adaptive population management of marine predators in rapidly changing ecosystems such as the Gulf of California.