Conservation Physiology最新文献

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.

In the Anthropocene, species are increasingly faced with multiple stressors that are more severe and less predictable than before. While multiple stressors often interact to affect organisms negatively, sometimes these interactions can be beneficial, enhancing resilience through cross-protection. Cross-protection interactions occur when exposure to one stressor, such as elevated temperature, enhances an organism's tolerance to a different stressor, like hypoxia, through shared protective mechanisms or signaling pathways. Understanding the potential for cross-protection to combat rapid and diverse environmental change is crucial for conservation, as it potentially alters the predicted consequences of such change. Here, we outline 10 key considerations for investigating cross-protection in a conservation context. These considerations include the importance of stressor intensity and timing, recognizing species-specific and sex-specific responses, and embracing temporal variability in environmental stressors. Additionally, predictions will depend upon uncovering the underlying mechanisms of cross-protection by integrating emerging approaches like omics and meta-analyses. By better understanding-and in some cases explicitly leveraging-cross-protective interactions, conservation practitioners may be able to develop more effective management plans to enhance species resilience, potentially mitigating the immediate effects of emerging stressors. These insights are vital for guiding future research directions and informing conservation policies and management practices to preserve biodiversity in the Anthropocene.

The presence of chemical contaminants in freshwater systems poses a threat to many aquatic organisms, and understanding the extent and nature of this threat can facilitate conservation management actions. Sturgeon are considered threatened worldwide and they differ in many important ways from other fishes. Two sturgeon species, green sturgeon (Acipenser medirostris) and white sturgeon (A. transmontanus), are found in California and utilize anthropogenically impacted freshwater habitats of the Central Valley. This study evaluated the behavioural effects in endogenously feeding larvae (3-7 days post hatch) of both sturgeon species following an acute exposure (96 hours) to the pyrethroid pesticide bifenthrin at aqueous concentrations ranging from 10 to 2000 ng/l, with selected levels based on previous environmental monitoring. Sturgeon had high survival at all concentrations tested (~95%), yet at higher concentrations (>1000 ng/l) they displayed altered behavioural patterns, including reduced activity, increased meander of the movement path and reduced thigmotaxis. While these higher concentrations of bifenthrin have been observed within water samples from the sturgeon habitats of California, they appear uncommon. The present study suggests that sturgeon larvae are not highly sensitive to acute aqueous exposure under environmentally relevant concentrations of bifenthrin (1-10 ng/l), yet these aqueous concentrations do have behavioural effects that may be of concern for the conservation of these declining species. Additionally, impacts to these species may also occur through exposure to sediment-bound bifenthrin or dietary bioaccumulation, and more work needs to be done to understand the implications of these exposure routes.

The northern bobwhite (Colinus virginianus) is an economically and ecologically vital gamebird in North America experiencing vast population declines. With the recent validation of an enzyme immunoassay to detect corticosterone metabolites in faeces, there are many opportunities for its scientific application. Corticosterone, a key avian stress-related hormone, has many beneficial functions that support a quail's immune response, primarily by suppressing inflammation, allowing cells to function more efficiently. However, chronic levels of elevated corticosterone in Aves have been shown to cause metabolic disruption and suppressed reproduction and growth. Determining root causes of chronically elevated corticosterone levels is vital for bobwhite conservation efforts. Proposed research investigating causes of bobwhite stress includes examining the effects of pesticides, climate, disease and management strategies. However, the various methodologies exploring these relationships may result in different ways the faeces are stored and processed, especially in studies on wild bobwhite. These differences may impact research outcomes leading to incorrect conclusions. This study was conducted to determine if enzyme immunoassay results from faecal samples frozen or left in the environment before extraction of faecal corticosterone metabolites differ from those where extraction is immediate. Faeces treatments affected the corticosterone metabolite measurements differently depending on whether the faeces were from males or females, so the effects of treatments were analysed within each sex. No significant difference was found in female faecal corticosterone metabolite concentrations between the frozen and environmentally exposed faeces (P = 0.853); however, concentrations in the immediately extracted faecal corticosterone metabolites were significantly lower (P < 0.001). Male bobwhite faecal samples that were immediately frozen had significantly lower faecal corticosterone metabolite concentrations compared to environmentally exposed male samples and frozen female samples (P = 0.039). These results indicate that faecal corticosterone metabolite concentrations are comparable between environmentally exposed samples from both sexes and frozen samples from females.

Wildlife health assessments including haematology and biochemistry parameters are essential to evaluating the well-being of free-living species. In Galapagos, the iconic giant tortoises still thrive in the archipelago despite anthropogenic pressures, with up to 13 extant species distributed across most islands and ecosystems. In previous work conducted by our research group, we described for the first-time reference intervals of haematology and plasma biochemistry in four Galapagos tortoise species. With the aim of continuing to provide cutting-edge health data for Galapagos tortoises, here we report haematology and plasma biochemistry descriptive statistics, reference intervals and cell morphology of tortoises from four different tortoise populations (i.e. Alcedo Volcano, Cerro Azul Volcano, Cinco Cerros and Sierra Negra Volcano). Additionally, we compared values between sexes and applied a principal component analysis to explore differences in haematology and biochemistry parameters between tortoise populations, including those previously published by our research group. Females presented higher calcium, phosphorus and albumin, consistent with vitellogenesis, whereas males had higher packed cell volume and sodium than females. Blood cell morphology was consistent across species. The two main principal components of the multivariate statistical model were unable to explain >44.9% of the variance across tortoise populations. We suggest additional research to explore the correlation between anthropogenic factors (i.e. climate change, pesticides, plastics) and blood values, for a deeper understanding of tortoise physiology and ultimately improved diagnostics and management actions. In the anthropogenic era, understanding the health status of bioindicator species like Galapagos tortoises is mandatory to inform current and future conservation priorities and actions.