Conservation Physiology最新文献

The southern Beaufort Sea polar bear sub-population (Ursus maritimus) has been adversely affected by climate change and loss of sea ice habitat. Even though the sub-population is likely decreasing, it remains difficult to link individual polar bear health and physiological change to sub-population effects. We developed an index of allostatic load, which represents potential physiological dysregulation. The allostatic load index included blood- and hair-based analytes measured in physically captured southern Beaufort bears in spring. We examined allostatic load in relation to bear body condition, age, terrestrial habitat use and, over time, for bear demographic groups. Overall, allostatic load had no relationship with body condition. However, allostatic load was higher in adult females without cubs that used terrestrial habitats the prior year, indicating potential physiological dysregulation with land use. Allostatic load declined with age in adult females without cubs. Sub-adult males demonstrated decreased allostatic load over time. Our study is one of the first attempts to develop a health scoring system for free-ranging polar bears, and our findings highlight the complexity of using allostatic load as an index of health in a wild species. Establishing links between individual bear health and population dynamics is important for advancing conservation efforts.

Non-native plant invasions and climate warming alter the microclimatic conditions that organisms experience in their habitats, with potential implications for the fitness of native faunal species, particularly ectotherms. Predictions for species conservation increasingly use microclimate data at fine spatial scales relevant to organisms, but they typically overlook the modulating effect that vegetation changes have on the microclimates available in the habitat. Here we quantify the microclimatic changes imposed by invasive trees and simultaneous warming on native habitats and assess the resulting thermal benefits and costs to a small tortoise species (Homopus areolatus) from an organismal perspective and throughout its life cycle. We logged operative temperature above- and belowground in the field, covering the diversity of microhabitats across the four seasons of the year, and assessed the species' optimal temperature in the laboratory. Moving beyond the common use of averages, we applied a range of metrics to quantify differences between invaded and native areas in spatio-temporal temperature distributions, combined effects with warming and thermal habitat suitability for the species. We found that invaded areas became cooler and less exposed to temperatures above the species' optimal in summer. This buffering effect is expected to become more pronounced with further climate warming, turning invaded areas into potential thermal refugia. However, reduced spatial thermal heterogeneity during warm periods, more prevalent sub-optimal low temperatures in winter and colder underground incubation conditions in invaded areas could be detrimental to the species' long-term performance. Our results reveal the mixed nature of thermal effects of invasive plants on ectotherms, underscoring the importance of applying a suite of metrics to assess microclimate distribution changes. The approach used here illustrates the value of integrating thermal physiological and microclimatic information for a more mechanistic understanding of conservation problems.

Natural light-dark cycles are responsible for synchronizing an animal's circadian clock with environmental conditions. Consequently, the endocrine system is vulnerable to changes in the external light environment, particularly short-wavelength blue light. Artificial light at night drastically changes the night-time environment by masking natural light cycles and disrupting well-established biological rhythms. The introduction of blue-rich lighting, such as white light-emitting diodes (LEDs), may increase the biological effects of light at night on wildlife. However, flexibility in the spectral composition of LED lighting presents options for wildlife-sensitive lighting, such as long-wavelength amber LEDs. Here we examine the effect of light spectra on circadian physiology in a nocturnal marsupial. Specifically, we investigate the effect of short-wavelength white (standard urban lighting) and long-wavelength amber LEDs (proposed wildlife-sensitive lighting) on circadian hormones and cell-mediated immunity in the Krefft's glider (Petaurus notatus). Melatonin and glucocorticoid secretion were disrupted following exposure to both short-wavelength white and long-wavelength amber LEDs. Both LEDs suppressed melatonin, whilst glucocorticoid secretion was suppressed under amber LEDs and increased under white LEDs. Despite this disturbance we did not detect any effect of light treatment on cell-mediated immune response. Our findings offer a novel contribution to understanding the physiological impacts of light at night on wildlife. We also provide evidence that long-wavelength amber LEDs can disrupt physiology and are not a wildlife-sensitive lighting option for all species.

Seabirds are frequently infected by avian influenza virus (AIV), which prior to 2021 primarily consisted of low-pathogenic AIV with limited reports of disease during infection. However, since highly pathogenic AIV (HPAIV) H5N1 clade 2.3.4.4b was introduced to North America in late 2021, HPAIV outbreaks in seabirds have occurred in multiple regions, with high levels of morbidity and mortality in many species. While monitoring active viral infections is critical for tracking disease burden, monitoring prior viral exposure via antibody detection in species that experienced large outbreaks is important for identifying individual- and population-level impacts of AIV on immunity and survival. We capitalized on ongoing egg collection programmes to assess the prevalence of antibodies against AIV nucleoprotein (NP) and hemagglutinin subtype 5 (H5) in 523 eggs collected in 2022 and 2023 from 11 seabird species that breed in the northwestern Atlantic, including primarily samples from eastern Canada and two from western Iceland. The prevalence of AIV antibodies in eggs varied across regions, species and years. American common eider (Somateria mollissima dresseri) eggs had the highest AIV antibody prevalence compared to sympatric species in 2023. Longitudinal samples were available for northern gannets (Morus bassanus) and American herring gulls (Larus argentatus smithsoniansus) at several sites, where the prevalence of anti-NP and anti-H5 antibodies increased from 2022 to 2023. Examining AIV antibody prevalence in seabird eggs can be a useful tool to investigate population-level AIV exposure, while we acknowledge our limited understanding of differential antibody waning rates and the relationship between titre and susceptibility.

Understanding the energetic demands of reproduction on female sea turtles is crucial for devising effective conservation strategies aimed at supporting the reproductive health and resilience of populations at nesting habitats. We studied the ovaries of 69 green turtles (Chelonia mydas) preyed upon by jaguars (Panthera onca) during three nesting seasons at Tortuguero, Costa Rica, the main green turtle Atlantic nesting beach. Our findings revealed a bimodal distribution of vitellogenic follicles, with 'dominant' follicles destined for ovulation and 'non-dominant' follicles to be resorbed. Female green turtles lay, on average, six clutches with ~110 eggs each per nesting season, and a size hierarchy was also found within dominant follicles. During the nesting season, the diameter of small dominant follicles increased by 66% prior to ovulation. Analysis of yolk composition showed that small dominant follicles had higher percent water content than large dominant follicles, which indicates dry matter deposition rather than hydration is responsible for the pre-ovulatory increase in diameter of green turtle dominant follicles during the nesting season. Furthermore, percentages of lipid, nitrogen (N) and phosphorus (P) in the yolk dry matter were constant across green turtle vitellogenic follicles, which underscores that the increase in follicle size results from provisioning with yolk containing similar proportions of these nutrients. Atretic follicles had higher water and lower P percentages than dominant follicles, indicating an accelerated resorption of phosphorus over lipids and N, which could be due to the importance of this nutrient for eggshell production. Finally, >49% of the energy required for egg production was still to be invested during the nesting season, and yolk from non-dominant follicles would not have provided sufficient energy for most females to complete yolk deposition. These insights into follicular dynamics and nutrient provisioning clarify the ongoing reproductive investments made by female green turtles at Tortuguero.

Seed (gene)banking is an effective way to conserve cultivated and wild plant diversity. However, long-term funding is not always consistently sufficient, and there is a need to both strengthen the effectiveness of genebank operations and maximize cost efficiency. One way to control the cost of maintaining a germplasm collection is to optimize the quantity of seeds per accession that is placed into storage, depending on the expected length of time a seed lot will remain above the viability threshold, expected rates of use for distribution and viability testing and on the requirement to ensure a reserve. Here, we express this as an equation, which can be applied to cultivated species and adjusted to different scenarios, but also to inform decisions about use of accessions of wild species where the number of seeds available is limited, a common scenario for wild-species conservation seed banks. For many crop genebanks, given the expected longevity of seeds, it would be worthwhile to increase the number of seeds produced and processed for storage. This would also help to diminish the risk of genetic drift due to frequent cycles of regeneration but would have implications in terms of how accessions are regenerated, in particular, how many plants are used for regeneration and the size of storage facilities. The equation we present can also be rearranged and used to plan how to allocate seeds for testing and use when the number of seeds available is limited. This may have particular relevance for species conservation seed banks.

The black-footed ferret (Mustela nigripes) is an endangered North American mustelid. This species is bred in managed care with the goal of reestablishing wild populations. However, individual ferrets in the conservation breeding programme have variable reproductive success. We monitored faecal steroid hormone metabolite profiles of 22 black-footed ferrets across two breeding seasons to examine whether endocrine factors were associated with successful reproduction. Among successfully whelping females, faecal progesterone metabolite concentrations were higher (P = 0.04) and faecal cortisol metabolite (FCM) concentrations were marginally higher (P = 0.07) in the late luteal phase compared to females who did not whelp (likely pseudopregnant). Effect sizes suggested that, in successfully whelping females, faecal oestradiol metabolite levels were higher in the follicular phase and FCM levels lower in the early luteal phase, but with high variation and lack of statistical significance. We speculate that this variation may be because male causes of reproductive failure account for some of these cases of pseudopregnancy. Among males, individuals that failed to successfully copulate had lower faecal testosterone metabolite concentrations than successful sires (P = 0.01). However, males who copulated but failed to sire a litter did not differ from successful sires in testosterone metabolite concentrations. Comparisons of sperm morphology between successful and unsuccessful sires were statistically underpowered, hence poor sperm quality could not be ruled out as a possible cause of these post-copulatory reproductive failures. Our data suggest that individuals who fail to reproduce in managed care are not experiencing chronic stress, based on FCM levels, although changes in females during the early luteal phase warrant further investigation. While male post-copulatory reproductive failure was not associated with deficiencies in sex hormone production, males that fail to copulate could potentially be targeted for testosterone supplementation.

Song competitions involving passerines, such as the Green-winged Saltator (Saltator similis), are legally permitted in Brazil and attract widespread participation. This study aimed to assess the adrenal response in male S. similis by comparing glucocorticoid metabolite (GCM) levels in uro-faecal extract samples collected during three competitions with those from a rest day (3 days before the competition, D-3), a day before the competition (D-1), the day of the competition (D0) and a day after the competition (D1). Simultaneously, we examined the potential variation in GCM levels among other males not engaged in song competitions but subjected to ex situ conditions much like those of participating males. GCM levels were measured using a direct enzyme immunoassay (EIA, CJM006), which was physiologically (ACTH challenge) and analytically validated (parallelism, accuracy and precision tests) for the species under study. The results indicated that the average GCM concentration was lower in the competition group (33.43 ± 22.09 ng/g) as compared to the control group (70.09 ± 29.45 ng/g; P = 0.01). However, concentrations spiked significantly on competition day (D0: 38.29 ± 26.12 ng/g) as compared to the rest day (D-3: 28.64 ± 17.86  ng/g; P = 0.02), suggesting acute stress response. Given the elevated GCM levels observed during competitions, further research is necessary to confirm the welfare of these birds under competition conditions and to explore the long-term effects of such stressors.

Increasing variable hydroperiods may leave ectotherms with complex life cycles more vulnerable to the impacts of environmental drying. While developmental plasticity may enable some species to escape drying ponds, this plasticity might result in trade-offs with performance and subsequent fitness in adults. Here, we used rice paddy frogs (Fejervarya limnocharis) to test how pond drying influences the developmental plasticity of tadpoles, and the resulting carryover effects on body size and jumping performance. We predicted that tadpoles under simulated drought conditions (2-0.25 cm depth) compared to low stable water level conditions (0.25 cm depth) would develop faster, and the resulting metamorphs would be smaller and exhibit lower jumping performance. We show that tadpoles in drying conditions had a faster developmental rate than tadpoles in stable low water level treatments. The size of metamorphs from the drying treatment was similar to the high-water treatments (2 cm depth), but maximum jumping distance of individuals from the drying condition was lower than that of the high-water treatment. These results indicate that drying conditions for F. limnocharis increase development rate without a reduction in size at metamorphosis, but with poorer mass-independent locomotor performance, which can potentially impact their survival.

Ongoing amphibian population declines are caused by factors such as climate change, habitat destruction, pollution and infectious diseases not limited to chytridiomycosis. Unfortunately, action is taken against these factors once population collapses are underway. To avoid these post hoc responses, wildlife endocrinology aims to analyse physiological mediators that predict future population declines to inform wildlife management. Mediators typically investigated are stress hormones known as glucocorticoids, which are produced by the Hypothalamus-Pituitary-Interrenal axis (HPI axis). The HPI axis is the part of the endocrine system that helps amphibians cope with stress. Chronic increases in glucocorticoids due to stress can lead to immune dysfunction, which makes amphibians more susceptible to infectious diseases. Despite this predictive potential of glucocorticoids, interpretation of glucocorticoid data is confounded by sampling design and type. Glucocorticoid monitoring classically involves blood sampling, which is not widely applicable in amphibians as some are too small or delicate to sample, and repeated samples are often valued. To address this, we tried to validate skin swabbing via corticosterone (CORT) and adrenocorticotropin hormone (ACTH) injections in adults of two amphibian species: Eastern red-spotted newts, Notophthalmus viridescens viridescens, with natural skin infections with Batrachochytrium dendrobatidis (Bd) upon collection in the field, and Northern leopard frogs, Rana (Lithobates) pipiens, raised in captivity and naïve to Bd exposure. Further, we determined the predictive potential of skin glucocorticoids on Bd load in the field via correlations in Eastern red-spotted newts. We found that hormones present in the skin are not related to the HPI axis and poorly predict infection load; however, skin hormone levels strongly predicted survival in captivity. Although skin swabbing is not a valid method to monitor HPI axis function in these species, the hormones present in the skin still play important roles in organismal physiology under stressful conditions relevant to wildlife managers.