A novel technique to measure chronic levels of corticosterone in turtles living around a major roadway

Nailing it: Investigation of elephant toenails for retrospective analysis of adrenal and reproductive hormones

Hormone monitoring of at-risk species can be valuable for evaluation of individual physiological status. Traditional non-invasive endocrine monitoring from urine and faeces typically captures only a short window in time, poorly reflecting long-term hormone fluctuations. We examined toenail trimmings collected from African (Loxodonta africana) and Asian (Elephas maximus) elephants during routine foot care, to determine if long-term hormone patterns are preserved in these slow-growing keratinized tissues. We first measured the growth rate of elephant toenails biweekly for one year, to establish the temporal delay between deposition of hormones into nail tissue (at the proximal nail bed) and collection of toenail trimmings months later (at the distal tip of the nail). In African elephants, toenails grew ~0.18 ± 0.015 mm/day (mean ± SEM) and in Asian elephants, toenails grew ~0.24 ± 0.034 mm/day. This slow growth rate, combined with the large toenail size of elephants, may mean that toenails could contain a 'hormone timeline' of over a year between the nail bed and nail tip. Progesterone, testosterone and cortisol were readily detectable using commercial enzyme immunoassays, and all assays passed validations, indicating that these hormones can be accurately quantified in elephant toenail extract. In most cases, variations in hormone concentrations reflected expected physiological patterns for adult females and males (e.g. ovarian cycling and musth) and matched individual health records from participating zoos. Progesterone patterns aligned with our calculations of temporal delay, aligning with female ovarian cycling from over six months prior. Unexpectedly, male testosterone patterns aligned with current musth status at the time of sample collection (i.e. rather than prior musth status). Though this sample type will require further study, these results indicate that preserved hormone patterns in elephant toenails could give conservationists a new tool to aid management of elephant populations.

A validated LC-MS/MS method for simultaneous determination of key glucocorticoids in animal hair for applications in conservation biology

A new method for the determination of main glucocorticoids (cortisol, cortisone, and corticosterone) in hair by liquid chromatography-tandem mass spectrometry was developed. Glucocorticoids were extracted from hair shafts using methanol followed by solid-phase extraction. A validation test was performed using hair from three species of wild mammals with different body size (0.2-800 kg), lifestyle (terrestrial, burrowing and arboreal species), social organization (living in herds or solitary), and different predicted type of hair glucocorticoids: European bison (Bison bonasus), European hamster (Cricetus cricetus), and Eurasian red squirrel (Sciurus vulgaris). Regardless of the species evaluated, the method shows good linearity for all analytes accompanied by satisfactory accuracy (91-114%) and precision (RSD < 13%). Depending on the analyte and hair origin, the calculated limits of quantification were between 0.05 and 1.19 ng/mL, which corresponds to 1.28-31.51 pg/mg. Using cortisol and cortisone as examples, we have demonstrated that measuring multiple glucocorticoids simultaneously provides more comprehensive information than solely concentrating on one, thereby contributing to a more balanced and reliable interpretation of the acquired results. However, the utility of cortisol metabolites as markers of stress response in keratinized tissues should be substantiated by additional experimental studies on targeted animals. We posit that this paper could serve as a crucial catalyst to prompt such experiments.

Tracking reproductive events: Hoof growth and steroid hormone concentrations in hair and hoof tissues in moose (Alces alces)

Measurements of reproductive and stress-related hormones in keratinous tissues (e.g. hair, claws, hooves, baleen) can provide a record of stress and reproductive response in wildlife. We evaluated a method to collect keratin tissue from hooves of immobilized moose (Alces alces) and validated enzyme immunoassays for measuring cortisol and progesterone in hooves and hair. We also measured the annual growth and wear rates of moose hooves. Progesterone (range: 1.0-43.7 pg/mg) and cortisol (range: 0.05-2.9 pg/mg) were measurable and showed variation among hoof samples and moose. Pregnant females had twice as high progesterone concentrations (18.00 ± 3.73 pg/mg) from hoof sample locations post breeding compared to non-pregnant moose (9.40 ± 0.25 pg/mg). Annual hoof growth differed between the front (5.58 ± 0.12 cm) and rear (4.73 ± 0.13 cm) hooves and varied by season with higher growth rates during summer which decreased into autumn and winter. Adult female hooves represented between 1.6 and 2.1 years of growth and included up to two reproductive cycles. We established a method to estimate hoof growth rate and applied this to postmortem samples and were able to detect previous pregnancies. Shoulder guard hairs grew between August and March including during late gestation; however, hair progesterone concentrations (range: 2-107.1 pg/mg) were not related to reproductive state. Hair cortisol concentrations in our study (range: 0.2-15.9 pg/mg) were within the range of values previously reported for cervids. Our study supports the use of hooves for longitudinal sampling and measuring reproductive and stress-related hormones, providing a new tool for tracking reproductive events and understanding what variables may contribute to population level changes in reproduction.

Long term stability of corticosterone in feathers

Measuring corticosterone in feathers allows researchers to make long-term, retrospective assessments of physiology with non-invasive sampling. To date, there is little evidence that steroids degrade within the feather matrix, however this has yet to be determined from the same sample over many years. In 2009, we made a pool of European starling (Sturnus vulgaris) feathers that had been ground to a homogenous powder using a ball mill and stored on a laboratory bench. Over the past 14 years, a subset of this pooled sample has been assayed via radioimmunoassay (RIA) 19 times to quantify corticosterone. Despite high variability across time (though low variability within assays), there was no effect of time on measured feather corticosterone concentration. In contrast, two enzyme immunoassays (EIA) produced higher concentrations than the samples assayed with RIA, though this difference is likely due to different binding affinities of the antibodies used. The present study provides further support for researchers to use specimens stored long-term and from museums for feather corticosterone quantification, and likely applies to corticosteroid measurements in other keratinized tissues.

Evaluating Dermal Bone as a Novel Source of Endocrine Information in Ninespine and Threespine Stickleback Fish

Monitoring the physiology of small aquatic and marine teleost fish presents challenges. Blood samples, often the first choice for endocrinologists, can be difficult or even impossible to obtain and alternative matrices currently used for hormone analyses do not occur in fishes (e.g., hair, feathers etc.) or are not easily collected from small aquatic organisms (e.g., urine and feces). Some teleosts, however, have enlarged bony dermal elements that possibly accumulate and store steroid hormones in physiological relevant concentrations. Both threespine stickleback (Gasterosteus aculeatus) and ninespine stickleback (Pungitius pungitius) have a series of external, lateral bony plates, dorsal spines, and a pair of pelvic spines attached to the pelvic girdle. We investigated if cortisol, the primary circulating glucocorticoid in teleosts, could be extracted from stickleback dermal bone and quantified using a commercially available enzyme immunoassay (EIA). We successfully validated a cortisol EIA for dermal bone extracts, determined that cortisol was detectable in both species, and found that dermal bone cortisol levels significantly correlated with cortisol levels in whole body homogenate. Ninespine stickleback had significantly higher dermal bone cortisol concentrations than threespine stickleback and female threespine stickleback tended to have over twice the mean dermal bone cortisol concentration than males. Because both stickleback species are widely used for ecotoxicological studies, using dermal bone as a source of endocrine information, while leaving the body for contaminant, genomic, histological, and stable isotope analyses, could be a powerful and parsimonious tool. Further investigation and physiological validations are necessary to fully understand the utility of this new sample matrix.

Assessing chronic stress in wild mammals using claw-derived cortisol: a validation using European badgers (Meles meles)

Measuring stress experienced by wild mammals is increasingly important in the context of human-induced rapid environmental change and initiatives to mitigate human-wildlife conflicts. Glucocorticoids (GC), such as cortisol, mediate responses by promoting physiological adjustments during environmental perturbations. Measuring cortisol is a popular technique; however, this often reveals only recent short-term stress such as that incurred by restraining the animal to sample blood, corrupting the veracity of this approach. Here we present a protocol using claw cortisol, compared with hair cortisol, as a long-term stress bio-indicator, which circumvents this constraint, where claw tissue archives the individual's GC concentration over preceding weeks. We then correlate our findings against detailed knowledge of European badger life history stressors. Based on a solid-phase extraction method, we assessed how claw cortisol concentrations related to season and badger sex, age and body-condition using a combination of generalized linear mixed models (GLMM) (n = 668 samples from 273 unique individuals) followed by finer scale mixed models for repeated measures (MMRM) (n = 152 re-captured individuals). Claw and hair cortisol assays achieved high accuracy, precision and repeatability, with similar sensitivity. The top GLMM model for claw cortisol included age, sex, season and the sex*season interaction. Overall, claw cortisol levels were significantly higher among males than females, but strongly influenced by season, where females had higher levels than males in autumn. The top fine scale MMRM model included sex, age and body condition, with claw cortisol significantly higher in males, older and thinner individuals. Hair cortisol was more variable than claw; nevertheless, there was a positive correlation after removing 34 outliers. We discuss strong support for these stress-related claw cortisol patterns from previous studies of badger biology. Given the potential of this technique, we conclude that it has broad application in conservation biology.

Stress Concepts and Applications in Various Matrices with a Focus on Hair Cortisol and Analytical Methods

When studying stress in animals, it is important to understand the types of stress and their classification, and how to assess the stress levels in different animal species using different matrices accurately and precisely. The classification of stress types helps to distinguish between good stress (eustress) and bad stress (distress). Hence, first, it is crucial to assess the animal's level of stress in a non-intrusive manner and second to identify the type of stress that is best suited to its environment. Third, it is also important to analyze the obtained samples using a suitable method to increase the validity of stress hormone measurements. Therefore, in this review, we aim to: (1) explain the classification of stress, (2) discuss the wide range of body matrices (e.g., saliva, milk, hair, urine, feces, sweat, fins, etc.) that can be used as samples to evaluate stress levels, as well as their comparisons and limitations, and present the reliable matrices for measuring stress hormones with special emphasis on hair, (3) compare the analytical methods for measuring stress hormones after sample preparation. Despite some literature that does not include hair as a reliable matrix for evaluating stress levels, hair is one of the matrices for measuring long-term stress hormone accumulations. This review discusses some factors that influence the level of stress hormones in the hair. By understanding these issues, the scientific community will not only be able to improve the understanding of stress and biomarker evaluation but also suggest how to deal with the consequences of stress in future research.

Relationships between age, diet, and stress-related hormones and reproduction in American marten (Martes americana)

American marten (Martes americana) in Interior Alaska are at the northwestern limit of their North American range. To investigate factors that may be associated with reproduction we determined the cementum age and the presence or absence of blastocysts in 118 female martens for 3 years (2012, 2014, and 2016) in two regions. For each marten we collected fur samples and measured steroid hormone concentrations (cortisol, testosterone, and progesterone) and stable isotopes (δ15N and δ13C values, a proxy for diet). These parameters reflect the diet and endocrine activity between June and October when fur is grown. We also collected two claws from a subset of 39 female marten from one region in 2012 and 2014. Progesterone concentrations were measured in one whole claw and from a second claw divided into proximal (recent growth) and distal sections. Differences in the probability of blastocysts being present were associated with geographic region and sample year suggesting that reproduction in female marten varies on a fine scale. We found the that presence of blastocysts was positively associated with marten age and δ15N values in fur but negatively associated with fur cortisol concentrations. These findings suggest that the likelihood a female marten will reproduce in a given year is influenced, in part, by the proportion of protein in their diet and stressors encountered during late summer and fall, months before active gestation begins.

Personality matters: exploring the relationship between personality and stress physiology in captive African lions

Background

Considering animals as individuals and not as species is becoming increasingly essential to animal welfare management in captive settings. Recent studies on big cat personalities and coping strategies suggest personality can help big cats cope in their surroundings. Yet a large portion of the published literature focuses on understanding either the personality or stress physiology of big cats. Our research shows how integrating an improved understanding of the personality of big cats with stress physiology may enhance welfare, especially for endangered species like African lions. By using a wild cat personality checklist, this study compared the key personality dimensions of 22 African lions with its faecal glucocorticoids and assessed factors influencing their personality and stress physiology.

Results

We found two reliable personality dimensions for African lions (dominance and agreeableness) and identified key factors (sex, age and location) that may influence their personality. Further, on testing if these factors influenced the stress physiology through variations in glucocorticoid levels, there was no significant difference. However, there was a strong negative association between agreeableness and glucocorticoid levels. These results suggest that the behavioural traits loading positively and higher for agreeableness are associated with lower glucocorticoid stress levels, which may assist a lion to cope with stressors in its surroundings.

Conclusions

Our findings highlight this integrated approach of linking personality and stress physiology of big cats can be beneficial for caretakers. For example, during stressful veterinary procedures or in reintroduction programs, recognizing the personality of lions can help in designing or providing them with resources that will alleviate stress. Thus, there is a need for more interdisciplinary approaches that will contribute towards enhancing the individual and overall welfare of big cats.

Comparison of stress biomarkers in laying hens raised under a long-term multiple stress condition

The objective of the current experiment was to compare various stress biomarkers including the heterophil to lymphocyte ratio (H:L ratio) in blood and the corticosterone (CORT) concentrations in feathers, claws, and egg yolk and to find the potential stress biomarkers in laying hens exposed to a long-term multiple stress condition. A total of 24 Hy-Line Brown laying hens at 47 wk of age were allotted to 2 distinct conditions including normal condition (NC) and multiple stress condition (MC) with 8 replicated cages. In NC treatment, 8 hens were raised individually in the cage (0.16 m²/hen) under the temperature of 21 ± 0.6°C. In MC treatment, 16 hens were raised with 2 hens per cage to decrease space allowance (0.08 m²/hen) and the temperature was maintained at 31 ± 1.6°C. The experiment lasted for 8 wk. The common diets and water were fed on an ad libitum basis during the experiment. Results indicated no interactions between stress conditions and duration of stress exposure for all measurements. Hens in MC treatment had a greater (P < 0.01) blood H:L ratio than those in NC treatment. The greater (P < 0.05) H:L ratio for MC treatment was observed at all weeks. Hens in MC treatment had greater (P < 0.05) feather CORT concentrations than those in NC treatment. Feather CORT concentrations were increased (P < 0.05) with duration of the experiment. However, stress conditions did not influence claw CORT concentrations. A tendency (P = 0.081) was observed for greater yolk CORT concentrations in MC treatment than in NC treatment. In conclusion, the H:L ratio in blood and CORT concentrations in feathers and egg yolks are considered potential stress biomarkers in laying hens exposed to stress conditions, although each measurement has its respective limitations. However, CORT concentrations in the claw appear to be insensitive to a long-term stress exposure.

Fecal glucocorticoid metabolites and ectoparasites as biomarkers of heat stress close to roads in a Mediterranean lizard

Differences between air and ground temperatures are expected to narrow with the advance of the season in temperate regions (aka seasonal restriction in the availability of thermal microhabitats), which may activate behavioral and physiological responses of ectotherm species adapted to temperate climates. However, according to cost-benefit models of ectotherm thermoregulation, we hypothesize that these responses may also carry some costs. We quantified seasonal shifts in thermoregulatory precision, concentration of fecal glucocorticoid metabolites, and load of ectoparasites in a Mediterranean lizard, Psammodromus algirus. We also tested whether the proximity to a road, a putative source of chronic stress, can facilitate the glucocorticoid-mediated response of lizards to heat stress. As expected, differences between body and environmental temperatures narrowed during the reproductive season and lizards responded by increasing their thermoregulatory precision and the secretion of glucocorticoids, as indicated by metabolites in feces. Interestingly, lizards tended to have higher glucocorticoid concentration when captured far from the road. This might reflect either a putative impairment of the glucocorticoid-mediated response of the lizards to heat stress close to the road or the plastic capability of P. algirus to acclimate to sources of moderate chronic stress. In the latter direction, the increase of both glucocorticoid metabolites and thermoregulatory precision supported that this Mediterranean species responds to environmental thermal restrictions with adaptive behavioral and physiological mechanisms. However, this was also associated with an increase in its susceptibility to ectoparasites, which represents an added cost to the current cost-benefit models of ectotherm thermoregulation.

Effects of harmful algal blooms on stress levels and immune functioning in wetland-associated songbirds and reptiles

Harmful algal blooms (HABs), caused primarily by nutrient input from agricultural runoff, are a threat to freshwater systems worldwide, and are further predicted to increase in size, frequency, and intensity due to climate change. HABs occur annually in the Western Basin of Lake Erie (Ohio, USA), and these blooms become toxic when dominated by cyanobacteria that produce the liver toxin microcystin. Although we are making substantial inroads toward understanding how microcystin affects human health, less is known about effects of microcystin on wildlife exposed to HABs. Wetland-associated songbirds (barn swallows, Hirundo rustica, and red-winged blackbirds, Agelaius phoeniceus) and reptiles (Northern watersnakes, Nerodia sipedon, and painted turtles, Chrysemys picta) were sampled from wetlands exposed to chronically high microcystin levels due to a prolonged HAB event, and from unexposed, control wetlands. Physiological stress levels and several measures of immune functioning were compared between the HAB-exposed and control populations. Physiological stress levels, measured as heterophil:lymphocyte ratios, were higher in barn swallows, red-winged blackbirds, and Northern watersnakes exposed to a chronic HAB compared to unexposed, control individuals, but painted turtles did not differ in physiological stress levels between HAB-exposed and control individuals. Neither barn swallows nor red-winged blackbirds differed in immune functioning between populations, but HAB-exposed watersnakes had higher bactericidal capacity than control snakes, and HAB-exposed painted turtles had lower bactericidal capacity than control turtles. These results suggest that even when HABs do not cause direct mortality of exposed wildlife, they can potentially act as a physiological stressor across several taxa, and furthermore may compromise immune functioning in some species.

Chronic noise exposure has context-dependent effects on stress physiology in nestling Tree Swallows (Tachycineta bicolor)

Anthropogenic noise is increasing in intensity and scope, resulting in changes to acoustic landscapes and largely negative effects on a range of species. In birds, noise can mask acoustic signals used in a variety of communication systems, including parent-offspring communication. As a result, nestling birds raised in noise may have challenges soliciting food from parents and avoiding detection by predators. Given that passerine nestlings are confined to a nest and therefore cannot escape these challenges, noise may also act as a chronic stressor during their development. Here, we raised Tree Swallow (Tachycineta bicolor) nestlings with or without continuous, white noise to test whether noise exposure affected baseline and stress-induced plasma, integrated feather corticosterone levels, and immune function. Stress physiology and immune function may also vary with the competitive environment during development, so we also examined whether noise effects varied with brood size and nestling mass. We found that overall, exposure to noise did not alter nestling stress physiology or immune function. However, light nestlings raised in noise exhibited lower baseline plasma and integrated feather corticosterone than heavy nestlings, suggesting alternative physiological responses to anthropogenic stimuli. Furthermore, light nestlings in larger broods had reduced PHA-induced immune responses compared to heavy nestlings, and PHA-induced immune responses were associated with higher levels of baseline plasma and feather CORT. Overall, our findings suggest that noise can alter the stress physiology of developing birds; however, these effects may depend on developmental conditions and the presence of other environmental stressors, such as competition for resources. Our findings may help to explain why populations are not uniformly affected by noise.

Seasonal changes in steroid and thyroid hormone content in shed skins of the tegu lizard Salvator merianae

Sampling blood for endocrine analysis from some species may not be practical or ethical. Quantification of hormones extracted from nontypical sample types, such as keratinized tissues, offers a less invasive alternative to the traditional collection and analysis of blood. Here, we aimed to validate assays by using parallelism and accuracy tests for quantification of testosterone, corticosterone, progesterone, and triiodothyronine (T₃) in shed skins of tegu lizards. We assessed whether hormone content of sheds varied across one year similar to what was previously detected in plasma samples. In addition, we aimed to identify the phase relationship between hormone levels of shed skin and plasma levels obtained from the same animals. High frequency of shedding occurred during the active season for tegus (spring/summer), while shedding ceased during hibernation (winter). All hormones measured in shed skins exhibited seasonal changes in concentration. Levels of testosterone in shed skins of male tegus correlated positively with plasma testosterone levels, while corticosterone in both males and females exhibited an inverse relationship between sample types for the same month of collection. An inverse relationship was found when accounting for a lag time of 3 and 4 months between sheds and plasma testosterone. These results indicate that endocrine content of sheds may be confounded by factors (i.e., seasons, environmental temperature, thermoregulatory behavior, among others) that affect frequency of molting, skin blood perfusion, and therefore hormone transfer from the bloodstream and deposition in sheds of squamates.

Scales of our lives: Sex identification of Temminck's pangolin (Smutsia temminckii) using scales retrieved out of the illegal wildlife trade

Pangolins are the most trafficked wild mammals, with their scales in high demand. Scales are often the only part of the animal confiscated from the trade, but they represent accessible material for forensic investigations, including for sexing. This study aimed to develop a sexing tool for Temminck's pangolin, using scales for hormone quantification. Scales from males and females were liquidised using keratinase and the resulting suspension analysed for progestagen and androgen metabolite (scPM and scAM) concentrations. Scale PM and scAM concentrations were compared between sexes, while overall median values for scPM and scAM, as well as a ratio of scPM to scAM (P/A) were used as boundary values for sex identification. Neither scPM nor scAM concentrations were significantly different between the sexes and concentrations of a juvenile and sub-adult male overlapped with females, possibly indicating later sexual maturity in males. Boundary values for scAM concentrations and the P/A ratio predicted sex with 100% accuracy for females and 78% for males, while the accuracies for the scPM boundary value were lower. When only adult individuals are considered, scAM and P/A ratio boundaries are 100% accurate for both sexes. Therefore, scale hormone ratios show promise as a sex identification tool for Temminck's pangolin, particularly applicable in forensic investigations on the pangolin trade.

Fecal glucocorticoid metabolites reflect hypothalamic-pituitary-adrenal axis activity in muskoxen (Ovibos moschatus)

Muskoxen (Ovibos moschatus), a taxonomically unique Arctic species, are increasingly exposed to climate and other anthropogenic changes. It is critical to develop and validate reliable tools to monitor their physiological stress response in order to assess the impacts of these changes. Here, we measured fecal glucocorticoid metabolite (FGM) levels in response to the administration of adrenocorticotropic hormone (ACTH) in the winter (1 IU/kg) and summer (2 IU/kg) using two enzyme immunoassays, one targeting primarily cortisol and the other targeting primarily corticosterone. Fecal cortisol levels varied substantially within and among individuals, and none of the animals in either challenge showed an increase in fecal cortisol following the injection of ACTH. By contrast, two of six (winter) and two of five (summer) muskoxen showed a clear response in fecal corticosterone levels (i.e., maximal percentage increase as compared to time 0 levels > 100%). Increases in fecal corticosterone post-ACTH injection occurred earlier and were of shorter duration in the summer than in the winter and fecal corticosterone levels were, in general, lower during the summer. These seasonal differences in FGM responses may be related to the use of different individuals (i.e., influence of sex, age, social status, etc.) and to seasonal variations in the metabolism and excretion of glucocorticoids, intestinal transit time, voluntary food intake, and fecal output and moisture content. Results from this study support using FGMs as a biomarker of hypothalamic–pituitary–adrenal axis activity in muskoxen, advance our understanding of the physiological adaptations of mammals living in highly seasonal and extreme environments such as the Arctic, and emphasize the importance of considering seasonality in other species when interpreting FGM levels.

Common myths of glucocorticoid function in ecology and conservation

Glucocorticoids are popular hormones to measure in both biomedical and ecological studies of stress. Many assumptions used to interpret glucocorticoid results are derived from biomedical data on humans or laboratory rodents, but these assumptions often fail for wild animals under field conditions. We discuss five common assumptions often made about glucocorticoids in ecological and conservation research that are not generally supported by the literature. (1) High acute elevations of glucocorticoids indicate an animal in distress. In fact: because glucocorticoids are needed to survive stressors, elevated concentrations often reflect adequate coping. (2) Low glucocorticoid concentrations indicate a healthy animal. In fact: because glucocorticoids are important in responding to stressors, low glucocorticoid concentrations might indicate the lack of adequate coping. (3) Sustained elevated glucocorticoids indicate chronically stressed animals. In fact: glucocorticoid concentrations by themselves have no predictive value in diagnosing chronic stress. (4) Glucocorticoids mobilize energy to survive short-term stressors such as predator attacks. In fact: glucocorticoids' primary impact on energy regulation is to remove glucose transporters from cell surfaces. Not only is this process too slow to provide short-term energy, but glucocorticoid-induced increases in glucose reflect decreased, not increased, glucose utilization. (5) Glucocorticoid measurements in non-blood tissues (e.g., feces, hair, feathers, etc.) are equivalent to blood concentrations. In fact: these alternative tissues present imperfect reflections of blood concentrations, and it is blood concentrations that interact with receptors to evoke biological change. In summary, proper consideration of these common assumptions will greatly aid in interpreting glucocorticoid data from ecological and conservation studies.

Degradation of Temminck's pangolin (Smutsia temminckii) scales with a keratinase for extraction of reproductive steroid hormones

Hormone monitoring in keratinous tissues has become increasingly popular. The insoluble keratin materials are generally pulverised before hormone extraction; however, this is difficult for thicker keratin structures like baleen plates or hooves. A new method, involving the use of keratinase, allows enzymatic digestion of keratin and hormone analysis in the resulting suspension. Pangolins are unique mammals covered in keratinous scales, which are one of the reasons these animals are extensively trafficked. This study aimed to investigate the suitability of Temminck's pangolin scales as hormone matrix for quantifying reproductive steroids. A protocol was developed to digest scales with a keratinase before measuring hormone concentrations. This method can be used to investigate the reproductive endocrinology of Temminck's pangolins but may also be extended to the other extant pangolin species.•Keratinase digests Temminck's pangolin scales and reproductive steroid metabolite concentrations are measurable in the resulting suspension.•Isopropanol is an ideal washing solvent for scales to remove surface contaminants and scale sample mass should be standardised to allow comparisons.•Any section of a scale and scales from any pangolin body region can be used as samples for hormone quantification.

Corticosterone response by Peromyscus mice to parasites, reproductive season, and age

A common response to parasite infestations is increased production of glucocorticoid hormones that regulate immune function. We examined relationships between ectoparasite infestations and fecal corticosterone metabolites (FCM) in deer mice (Peromyscus maniculatus). Furthermore, we experimentally removed fleas to determine if reductions in ectoparasites affected FCM production. Individuals were assigned to control (no flea removal) or treatment (anti-flea application, physical combing) groups and individuals were recaptured to assess changes in FCM concentrations. There was a significant and negative effect of number of anti-flea treatment applications on FCM concentrations of deer mice. However, models including host biology traits and environmental predictors had a better model fit compared to models containing ectoparasite predictors. In particular, there was a significant relationship of deer mouse FCM with date and host age, where glucocorticoid production decreased towards the end of the breeding season and increased with age. Overall, adverse events associated with reproduction and age class, rather than ectoparasites, may be more important to variation in glucocorticoids of deer mice.

Ophidiomycosis in Red Cornsnakes (Pantherophis guttatus): Potential Roles of Brumation and Temperature on Pathogenesis and Transmission

Ophidiomycosis (snake fungal disease) is caused by the fungus Ophidiomyces ophiodiicola. As ophidiomycosis is difficult to study in free-ranging snakes, a reliable experimental model is needed to investigate transmission, pathogenesis, morbidity, and mortality, and the effects of brumation and temperature on disease development. Our objective was to develop such a model via subcutaneous injection of O. ophiodiicola conidia in red cornsnakes (Pantherophis guttatus). The model was used to evaluate transmission and the effects of brumation and temperature in co-housed inoculated and noninoculated snakes. All 23 inoculated snakes developed lesions consistent with ophidiomycosis, including heterophilic and granulomatous dermatitis, cellulitis, and myositis, and embolic fungal granulomas throughout the liver and the coelomic connective tissue in 21/23 (91%). In the inoculated snakes, 21% of skin swabs, 37% of exuvia, and all liver samples tested positive by qPCR (quantitative polymerase chain reaction) for O. ophiodiicola. A post brumation skin swab from 1/12 noninoculated snakes that brumated in contact with inoculated snakes tested positive by qPCR, suggesting possible contact transmission. That snake had microscopic skin lesions consistent with ophidiomycosis, but no visible fungal elements. Of the 23 inoculated snakes, 20 (87%) died over the 70-day experiment, with ophidiomycosis considered the primary cause of death; 12 (52%) of the inoculated snakes died during brumation. Overall, this experimental model of ophidiomycosis reproduced skin lesions analogous to those of many natural cases, and internal lesions similar to the most severe natural cases. The study provides tentative experimental evidence for horizontal transmission in brumation, and offers a tool for future studies of this widespread snake disease.

Beyond Glucocorticoids: Integrating Dehydroepiandrosterone (DHEA) into Animal Welfare Research

Animal welfare researchers are committed to identifying novel measures for enhancing the quality of life of individual animals. Recently, welfare scientists have emphasized the need for tracking multiple indicators of an animal's behavioral, emotional and mental health. Researchers are currently focused on integrating non-invasive physiological biomarkers to gain insight into an individual's welfare status. Most commonly, the animal welfare community has analyzed glucocorticoid hormones and their metabolites as a measure of stress. While glucocorticoids provide valuable information about hypothalamic-pituitary-adrenal (HPA) axis activity, there are limitations to utilizing these hormones as the sole measure of long-term stress and welfare. Other biomarkers, such as dehydroepiandrosterone and its sulfate ester-collectively referred to as DHEA(S)-help provide a more complete picture of HPA activity. DHEA(S) counteracts the effects glucocorticoids by having anti-aging, immune-enhancing and neuroprotective properties. Recent studies have examined the ratio of glucocorticoids to DHEA(S) as a way to better understand how the HPA axis is functioning. There is evidence that this ratio serves as an indicator of immune function, mental health, cognitive performance and overall welfare. We review studies that employed the glucocorticoid:DHEA(S) ratio, outline methodological considerations and discuss how researchers can integrate glucocorticoids, DHEA(S) and the glucocorticoid:DHEA(S) ratio into welfare assessments.

No island-effect on glucocorticoid levels for a rodent from a near-shore archipelago

Island rodents are often larger and live at higher population densities than their mainland counterparts, characteristics that have been referred to as "island syndrome". Island syndrome has been well studied, but few studies have tested for island-mainland differences in stress physiology. We evaluated island syndrome within the context of stress physiology of white-footed mice (Peromyscus leucopus) captured from 11 islands and five mainland sites in Thousand Islands National Park, Ontario, Canada. Stress physiology was evaluated by quantifying corticosterone (a stress biomarker), the primary glucocorticoid in mice, from hair and its related metabolites from fecal samples. White-footed mice captured in this near-shore archipelago did not display characteristics of island syndrome, nor differences in levels of hair corticosterone or fecal corticosterone metabolites compared with mainland mice. We suggest that island white-footed mice experience similar degrees of stress in the Thousand Islands compared with the mainland. Although we did not find evidence of island syndrome or differences in glucocorticoid levels, we identified relationships between internal (sex, body mass) and external (season) factors and our hormonal indices of stress in white-footed mice.

Baseline and stress-induced corticosterone levels across birds and reptiles do not reflect urbanization levels

Rates of human-induced environmental change continue increasing with human population size, potentially altering animal physiology and negatively affecting wildlife. Researchers often use glucocorticoid concentrations (hormones that can be associated with stressors) to gauge the impact of anthropogenic factors (e.g. urbanization, noise and light pollution). Yet, no general relationships between human-induced environmental change and glucocorticoids have emerged. Given the number of recent studies reporting baseline and stress-induced corticosterone (the primary glucocorticoid in birds and reptiles) concentrations worldwide, it is now possible to conduct large-scale comparative analyses to test for general associations between disturbance and baseline and stress-induced corticosterone across species. Additionally, we can control for factors that may influence context, such as life history stage, environmental conditions and urban adaptability of a species. Here, we take a phylogenetically informed approach and use data from HormoneBase to test if baseline and stress-induced corticosterone are valid indicators of exposure to human footprint index, human population density, anthropogenic noise and artificial light at night in birds and reptiles. Our results show a negative relationship between anthropogenic noise and baseline corticosterone for birds characterized as urban avoiders. While our results potentially indicate that urban avoiders are more sensitive to noise than other species, overall our study suggests that the relationship between human-induced environmental change and corticosterone varies across species and contexts; we found no general relationship between human impacts and baseline and stress-induced corticosterone in birds, nor baseline corticosterone in reptiles. Therefore, it should not be assumed that high or low levels of exposure to human-induced environmental change are associated with high or low corticosterone levels, respectively, or that closely related species, or even individuals, will respond similarly. Moving forward, measuring alternative physiological traits alongside reproductive success, health and survival may provide context to better understand the potential negative effects of human-induced environmental change.

Validation of a novel method to create temporal records of hormone concentrations from the claws of ringed and bearded seals

Ringed (Pusa hispida) and bearded seals (Erignathus barbatus) inhabit vast and often remote areas in the Arctic, making it difficult to obtain long-term physiological information concerning health and reproduction. These seals are experiencing climate-driven changes in their habitat that could result in physiological stress. Chronic physiological stress can lead to immunosuppression, decreased reproduction and decreased growth. Recently, keratin has become a popular matrix to measure steroid hormones, such as stress-related cortisol and reproduction-related progesterone. We developed and validated methods to extract cortisol and progesterone from the claws of adult female ringed (n = 20) and bearded (n = 3) seals using enzyme immunosorbent assays. As ringed and bearded seal claws grow, a pair of dark- and light-colored bands of keratin is deposited annually providing a guide for sampling. Two processing methods were evaluated, removal of claw material with a grinding bit or grinding followed by mechanical pulverization (102 paired samples from six claws, two each from three seals). Adding the mechanical pulverization step resulted in a 1.5-fold increase in hormone extraction. Progesterone from the proximal claw band was evaluated to biologically validate claw material as a measure of pregnancy in ringed seals (n = 14). Claws from pregnant seals had significantly higher claw progesterone concentrations than from non-pregnant seals. This suggests that the elevated progesterone associated with gestation was reflected in the claws, and that the most proximal claw band was indicative of pregnancy status at time of death. Thus, although the sample size was low and the collection dates unbalanced, this study demonstrates the potential to use claws to examine an extended time series (up to 12 yrs) of cortisol and progesterone concentrations in ringed and bearded seal claws.

Examining the Effects of Chronic Selenium Exposure on Traditionally Used Stress Parameters in Juvenile American Alligators (Alligator mississippiensis)

Environmental contaminants, such as the trace element selenium (Se), are a continuing concern to species worldwide due to their potential pathophysiological effects, including their influence on the stress response mediated through glucocorticoids (GCs; stress hormones). Environmental concentrations of Se are increasing due to anthropogenic activities, including the incomplete combustion of coal and subsequent disposal of coal combustion wastes. However, most studies examining how Se affects GCs have been focused on lower trophic organisms. The objectives of this study were to investigate the effects of long-term Se exposure on traditionally used stress parameters and to identify which of these parameters best indicate Se accumulation in liver and kidney of the American alligator (Alligator mississippiensis), a top trophic carnivore found in the southeastern United States and known to inhabit Se-containing areas. Alligators were divided into three dietary treatments and fed prey spiked with 1000 or 2000 ppm of selenomethionine (SeMet) or deionized water (control treatment) for 7 weeks. Following the 7-week treatment protocol, blood and tissue samples were obtained to measure plasma corticosterone (CORT; the main crocodilian GC), tail scute CORT, the ratio of peripheral blood heterophils (H) to lymphocytes (L) as H/L ratio, and body condition. To evaluate which parameter best indicated Se accumulation in the liver and kidney, principal component and discriminant analyses were performed. The only parameter significantly correlated with liver and kidney Se concentrations was scute CORT. Our results suggest that measurement of CORT in tail scutes compared with plasma CORT, H/L ratios, and body condition is the best indicator of Se-exposure and accumulation in crocodilians.

Town and Country Reptiles: A Review of Reptilian Responses to Urbanization

The majority of the world population is now inhabiting urban areas, and with staggering population growth, urbanization is also increasing. While the work studying the effects of changing landscapes and specific urban pressures on wildlife is beginning to amass, the majority of this work focuses on avian or mammalian species. However, the effects of urbanization likely vary substantially across taxonomic groups due to differences in habitat requirements and life history. The current article aims first to broaden the review of urban effects across reptilian species; second, to summarize the responses of reptilian fauna to specific urban features; and third, to assess the directionality of individual and population level responses to urbanization in reptile species. Based on our findings, urban research in reptilian taxa is lacking in the following areas: (1) investigating interactive or additive urban factors, (2) measuring multiple morphological, behavioral, and physiological endpoints within an animal, (3) linking individual to population-level responses, and (4) testing genetic/genomic differences across an urban environment as evidence for selective pressures.

Evidence of degradation of hair corticosterone in museum specimens

Researchers increasingly rely on non-invasive physiological indices, such as glucocorticoid (GC) levels, to interpret how vertebrates respond to changes in their environment. Recently, hair GCs have been of particular interest, because they are presumed stable over long periods of storage, which may facilitate the study of large-scale spatial and temporal patterns of stress in mammals. In the current study, we evaluated the stability of hair corticosterone levels in museum specimens, and the potential effects of different museum curation treatments. Using deer mouse (Peromyscus maniculatus) specimens collected from Vancouver Island (11 sites, 82 individuals) over 76 years, we found that specimens collected earlier in the 20th century had lower hair corticosterone than more recently collected specimens. These results suggest that hair hormone levels may not be stable over decades of storage time. We then subjected hair samples collected from white-footed mouse (Peromyscus leucopus, n = 36) to 3 different museum curation treatments, and found that borax lowered hair corticosterone levels relative to control samples, but air drying samples, or treating them with turpentine had no effect. Our results present a source of concern for the use of museum specimens for hair hormone analysis, and for studying long term trends in glucocorticoid levels.

Corticosterone in American alligator (Alligator mississippiensis) tail scutes: Evaluating the feasibility of using unconventional samples for investigating environmental stressors

Baseline plasma corticosterone (CORT) concentrations have been widely used to investigate the effects of stressors in wild and captive crocodilians. However, collecting baseline plasma CORT samples from wild crocodilians may be particularly difficult due to the capture and handling protocols used for large individuals. Thus, it may prove beneficial to use recently modified techniques for extracting CORT deposited in keratinized and non-keratinized tissues to better quantify the effects of long-term stress in crocodilians. In this study, we investigated the feasibility of using American alligator (Alligator mississippiensis) tail scute tissues to quantify CORT by collecting blood and tail scutes from 40 alligators before and after a short-term handling stressor. The objective of the current study was to better understand CORT deposition in crocodilian scutes and whether short-term increases in CORT could be detected. We found that CORT can be reliably extracted from alligator scute tissue and quantified using a commercially available enzyme immunoassay. However, there was a significant increase in scute CORT concentrations following an alligator being exposed to a short-term stressor (p = 0.017), although the magnitude of change was less than observed in plasma samples from the same individuals (p = 0.002). Furthermore, our results indicate that there was a significant effect of body condition on an alligator's post-stressor CORT concentration (p = 0.02). While our study is among the first to experimentally examine the usefulness of tissue CORT in crocodilians, a combination of field and laboratory experiments are needed to better understand deposition rates of CORT in scute tissues and to further validate the usefulness of tissue glucocorticoids for evaluating the effects of stress.

Turning the threat into a solution: using roadways to survey cryptic species and to identify locations for conservation

Freshwater turtles are one of the most imperilled groups of vertebrates globally, and roads have been associated with their decline. Although roads are typically viewed as an imminent threat to population persistence, because of direct mortality and increased landscape fragmentation, we argue that they are an important sampling tool for collecting a wide variety of data that can inform conservation efforts. Road surveys can yield important presence data when conducting species inventories, particularly for cryptic species, and can also indicate where to implement road mitigation measures. Our research examined three road survey methods from two previous studies (walking versus bicycling and walking versus driving) to test their relative effectiveness at locating turtles. We found that walking surveys yielded the highest number of turtles per kilometre; however, bicycling and driving surveys also presented advantages (specifically, the ability to survey longer lengths of road more quickly). We recommend using walking surveys in areas of specific interest (e.g. to investigate suitable habitat for imperilled species or to investigate the presence of cryptic species), and bicycling or driving surveys between sections of specific interest. Road survey methods could be used in addition to more traditional sampling approaches (e.g. trapping and visual surveys), and do not need to be restricted to areas where roadwork projects are in progress or being planned. Road surveys could also be used during general environmental assessments and ecological research, to effectively incorporate turtle presence data into conservation efforts.

Conservation implications of physiological carry-over effects in bats recovering from white-nose syndrome

Although it is well documented that infectious diseases can pose threats to biodiversity, the potential long-term consequences of pathogen exposure on individual fitness and its effects on population viability have rarely been studied. We tested the hypothesis that pathogen exposure causes physiological carry-over effects with a pathogen that is uniquely suited to this question because the infection period is specific and time limited. The fungus Pseudogymnoascus destructans causes white-nose syndrome (WNS) in hibernating bats, which either die due to the infection while hibernating or recover following emergence from hibernation. The fungus infects all exposed individuals in an overwintering site simultaneously, and bats that survive infection during hibernation clear the pathogen within a few weeks following emergence. We quantified chronic stress during the active season, when bats are not infected, by measuring cortisol in bat claws. Free-ranging Myotis lucifugus who survived previous exposure to P. destructans had significantly higher levels of claw cortisol than naïve individuals. Thus, cryptic physiological carry-over effects of pathogen exposure may persist in asymptomatic, recovered individuals. If these effects result in reduced survival or reproductive success, they could also affect population viability and even act as a third stream in the extinction vortex. For example, significant increases in chronic stress, such as those indicated here, are correlated with reduced reproductive success in a number of species. Future research should directly explore the link between pathogen exposure and the viability of apparently recovered populations to improve understanding of the true impacts of infectious diseases on threatened populations.

Stress response to handling is short lived but may reflect personalities in a wild, Critically Endangered tortoise species

We investigated the acute stress response associated with animal personalities by measuring plasma glucocorticoids throughout handling and collected ~2 years of movement and behavioural data in a wild, Critically Endangered animal, Astrochelys radiata (radiated tortoise). To determine whether our standard, brief conscientious handling procedures induce a stress response in our target species, we applied a stressor by way of initial animal processing and deployment of telemetry equipment. During surveys and processing, we sampled animals immediately upon detection, again after completing transmitter attachment and processing, and a final time the following day. We then used radiotelemetry to follow a subset of the animals for 22 months while collecting behavioural, climatic and location data. We found that brief and conscientious handling did not illicit consistent changes in plasma concentrations of the stress hormone corticosterone (CORT) but did reveal tremendous individual variation in response. The CORT concentration ranged more than 200-fold after imposing the stressor and returned to near-baseline values by the following day. When we accounted for the wide variation by calculating the degree of each individual's stress response relative to its baseline over its processing time, we discovered two non-overlapping physiological response types; those in which CORT concentrations increased dramatically in response to handling (219 ± 89.8 pg/ml/min) and those in which CORT varied only slightly (5.3 ± 8.9 pg/ml/min). The response types (strong vs. mild) also predicted body condition, home range size, activity, and behavioural tendencies. The degree of the individual's stress response in this species may be one component of correlated physiological and behavioural traits (animal personalities), which have previously been obscured in other chelonian studies by the use of mean values and should be considered in future conservation management applications for chelonian species.

Parasites, stress and reindeer: infection with abomasal nematodes is not associated with elevated glucocorticoid levels in hair or faeces

Stress hormones (glucocorticoids), incorporated into hair/fur and faeces, have been proposed as biomarkers of overall health in wildlife. Although such biomarkers may be helpful for wildlife conservation and management, their use has rarely been validated. There is a paucity of studies examining the variation of stress hormones in mammals and how they relate to other health measures, such as parasitism. Parasites are ubiquitous in wildlife and can influence the fitness of individual animals and populations. Through a longitudinal experiment using captive reindeer (Rangifer tarandus tarandus), we tested whether animals infected with Ostertagia gruehneri, a gastrointestinal nematode with negative impacts on fitness of the host, had higher stress levels compared with those that had been treated to remove infection. Faecal samples were collected weekly for 12 weeks (June-September) and hair was collected at the start and end of the study; glucocorticoids were quantified using enzyme immunoassays. Contrary to what was expected, infected reindeer had similar levels of cortisol in hair and slightly lower glucocorticoid metabolites in faeces compared with uninfected reindeer. Faecal corticosterone levels were higher than faecal cortisol levels, and only corticosterone increased significantly after a handling event. These results suggest that reindeer may use a tolerance strategy to cope with gastrointestinal nematodes and raise the question as to whether moderate infection intensities with nematodes are beneficial to the host. By removing nematodes we may have altered the gut microbiota, leading to the observed elevated faecal glucocorticoid metabolite levels in the treated reindeer. These findings demonstrate the importance of considering both cortisol and corticosterone in physiological studies, as there is mounting evidence that they may have different functionalities.

Conservation implications of a lack of relationship between baseline glucocorticoids and fitness in a wild passerine

The application of physiological measures to conservation monitoring has been gaining momentum and, while a suite of physiological traits are available to ascertain disturbance and condition in wildlife populations, glucocorticoids (i.e., GCs; cortisol and corticosterone) are the most heavily employed. The interpretation of GC levels as sensitive indicators of population change necessitates that GCs and metrics of population persistence are linked. However, the relationship between GCs and fitness may be highly context-dependent, changing direction, or significance, depending on the GC measure, fitness metric, life history stage, or other intrinsic and extrinsic contexts considered. We examined the relationship between baseline plasma corticosterone (CORT) levels measured at two periods of the breeding season and three metrics of fitness (offspring quality, reproductive output, and adult survival) in female Tree Swallows (Tachycineta bicolor). Specifically, we investigated whether (1) a relationship between baseline CORT metrics and fitness exists in our population, (2) whether the inclusion of energetic contexts, such as food availability, reproductive investment, or body mass, could alter or improve the strength of the relationship between CORT and fitness, and (3) whether energetic contexts could better predict fitness compared to CORT metrics. Importantly, we investigated these relationships in both natural conditions and under an experimental manipulation of foraging profitability (feather clipping) to determine the influence of an environmental constraint on GC-fitness relationships. We found a lack of relationship between baseline CORT and both short- and long-term metrics of fitness in control and clipped birds. In contrast, loss in body mass over reproduction positively predicted reproductive output (number of chicks leaving the nest) in control birds; however, the relationship was characterized by a low R² (5%), limiting the predictive capacity, and therefore the application potential, of such a measure in a conservation setting. Our results stress the importance of ground-truthing GC-fitness relationships and indicate that baseline GCs will likely not be easily employed as conservation biomarkers across some species and life history stages. Given the accumulating evidence of temporally dynamic, inconsistent, and context-dependent GC-fitness relationships, placing effort towards directly measuring fitness traits, rather than plasma GC levels, will likely be more worthwhile for many conservation endeavours.

A method to determine integrated steroid levels in wildlife claws

Glucocorticoids act throughout life to regulate numerous physiological and behavioral processes. Their levels are therefore highly labile, reacting to varying conditions and stressors. Hence, measuring glucocorticoids (and other steroids) in wildlife is challenging, and devising methods that are unaffected by the stress of capture and handling should be explored. Here we use the tip of free-ranging chameleons' claws that were cut to allow individual identification, and report a steroids extraction and quantification method. Claw steroids present an integrated level representing the period of claw growth. We found that we could measure corticosterone in small amounts of chameleon claw matrix using commercial EIA kits. Using this method, we learned that in wild male chameleons, claw corticosterone levels were associated with body size. We suggest that claw-testing can potentially provide an ideal matrix for wildlife biomonitoring.