Seasonal Hair Glucocorticoid Fluctuations in Wild Mice (Phyllotis darwini) within a Semi-Arid Landscape in North-Central Chile.

Mammals in drylands face environmental challenges exacerbated by climate change. Currently, human activity significantly impacts these environments, and its effects on the energy demands experienced by individuals have not yet been determined. Energy demand in organisms is managed through elevations in glucocorticoid levels, which also vary with developmental and health states. Here, we assessed how anthropization, individual characteristics, and seasonality influence hair glucocorticoid concentration in the Darwin's leaf-eared mouse (Phyllotis darwini) inhabiting two areas with contrasting anthropogenic intervention in a semi-arid ecosystem of northern Chile. Hair samples were collected (n = 199) to quantify hair corticosterone concentration (HCC) using enzyme immunoassays; additionally, sex, body condition, and ectoparasite load were recorded. There were no differences in HCC between anthropized areas and areas protected from human disturbance; however, higher concentrations were recorded in females, and seasonal fluctuations were experienced by males. The results indicate that animals inhabiting semi-arid ecosystems are differentially stressed depending on their sex. Additionally, sex and season have a greater impact on corticosterone concentration than anthropogenic perturbation, possibly including temporal factors, precipitation, and primary production. The influence of sex and seasonality on HCC in P. darwini make it necessary to include these variables in future stress assessments of this species.

Integrating alpha, beta, and phylogenetic diversity to understand anuran fauna along environmental gradients of tropical forests in western Ecuador.

The study of current distribution patterns of amphibian species in South America is of particular interest in areas such as evolutionary ecology and conservation biology. These patterns could be playing an important role in biological interactions, population size, and connectivity, and potential extinction risk in amphibians. Here, we tested the effects of spatial and environmental factors on the variation, turnover, and phylogenetic diversity of anuran amphibian species in tropical forests of western Ecuador. Data for presence/absence of 101 species of 34 genera and 10 families registered in 12 sites (nested in four biogeographic units) were obtained through fieldwork, museum collections, and literature records. We examined the influence of geographical, altitudinal, temperature, and precipitation distances on differences in anuran composition between sites. We found significant positive correlations among all of these variables with anuran distribution. The greatest alpha diversity (species richness) was found in the Equatorial Chocó biogeographic unit. Equatorial Pacific biogeographic unit could act as a transition zone between the Equatorial Chocó and Equatorial Tumbes. The western Andes (Western Cordillera biogeographic unit) was the most dissimilar and exhibited a higher species turnover rate than the other biogeographic units. Our results suggest that precipitation and elevation play a key role in maintaining the diversity of amphibian species in western Ecuador.

Protected areas' effectiveness under climate change: a latitudinal distribution projection of an endangered mountain ungulate along the Andes Range.

BACKGROUND: Climate change is one of the greatest threats to biodiversity, pushing species to shift their distribution ranges and making existing protected areas inadequate. Estimating species distribution and potential modifications under climate change are then necessary for adjusting conservation and management plans; this is especially true for endangered species. An example of this issue is the huemul (Hippocamelus bisulcus), an endemic endangered deer from the southern Andes Range, with less than 2,000 individuals. It is distributed in fragmented populations along a 2,000 km latitudinal gradient, in Chile and Argentina. Several threats have reduced its distribution to <50% of its former range. METHODS: To estimate its potential distribution and protected areas effectiveness, we constructed a species distribution model using 2,813 huemul presence points throughout its whole distribution range, together with 19 bioclimatic layers and altitude information from Worldclim. Its current distribution was projected for years 2050 and 2070 using five different Global Climate Models estimated for scenarios representing two carbon Representative Concentration Routes (RCP)-RCP4.5 and RCP6.0. RESULTS: Based on current huemul habitat variables, we estimated 91,617 km2 of suitable habitat. In future scenarios of climate change, there was a loss of suitable habitat due to altitudinal and latitudinal variation. Future projections showed a decrease of 59.86-60.26% for the year 2050 and 58.57-64.34% for the year 2070 according to RCP4.5 and RCP6.0, respectively. Protected areas only covered only 36.18% of the present distribution, 38.57-34.94% for the year 2050 and 30.79-31.94% for 2070 under climate change scenarios. DISCUSSION: Modeling current and future huemul distributions should allow the establishment of priority conservation areas in which to focus efforts and funds, especially areas without official protection. In this way, we can improve management in areas heavily affected by climate change to help ensure the persistence of this deer and other species under similar circumstances worldwide.

Masculinized females produce heavier offspring in a group living rodent.

Alternative morphotypes have been reported less frequently in females than in males. An exception to this rule is the gradient of phenotypical masculinization reported in some female mammals, in which feminized and masculinized females represent two opposite ends along this gradient. These phenotypical differences originate during prenatal development as the consequence of maternal effects. Feminized and masculinized females differ in several traits, including morphological, physiological, behavioural and reproductive traits. Differences previously reported in reproductive traits between feminized and masculinized females come mostly from mechanistic studies performed in the laboratory, and not necessarily on social species. As a result, it is unclear to what extent these reported differences between female alternative morphotypes materialize in wild, natural populations. We quantified the effect of female alternative morphotype on female reproductive traits in a natural population of Octodon degus, a highly social rodent. We assessed female alternative morphotype through a continuous gradient of anogenital distance. Thus, feminized females were close to the short end of anogenital distance, while masculinized females were close to the long end of this gradient. We also tested the hypothesis that the social environment interacts with female morphotype to influence female reproductive traits. In female degus, only body weight affected litter size, where heavier females weaned more offspring. Masculinized females delivered male-biased litters and weaned heavier offspring. Lastly, masculinized females gave birth later in the breeding season compared to feminized females. Contrary to previous claims, our findings do not support that masculinized females are less fertile than feminized females. Moreover, masculinized females produced heavier, potentially higher quality offspring compared with feminized females.

Do cortisol and corticosterone play the same role in coping with stressors? Measuring glucocorticoid serum in free-ranging guanacos (Lama guanicoe).

Habitat can constrain and shape successful ecological and physiological strategies, thus providing the context for the evolution of life-history traits. However, unpredictable challenges, such as storms, natural disasters, and human activities can also have great effects on stress. Glucocorticoids (GCs) are adrenal steroid hormones that play an important role in how vertebrates cope with these predictable and unpredictable environmental challenges. Although assessing GCs levels can have many applications in the study of wildlife and/or captive animals, with or without capturing individuals, it requires a species-specific complete validation (analytical and biological) before its use. In this work, our aim was to: (a) validate a radioimmunoassay (RIA) for measuring GCs levels in L. guanicoe serum; (b) assess cortisol and corticosterone levels (if present) in serum of wild L. guanicoe individuals; and (c) compare the response to acute stressors (handling, shearing, and release). Our results successfully: (a) validated RIA for asses GCs levels in wild ungulates; (b) confirmed the presence for cortisol and corticosterone and showed that both GCs are differently affected by environmental stimuli in L. guanicoe; and (c) showed that GCs exhibit different patterns in the field and in response to acute stressors, making these camelids an interesting endocrinological model when seeking the adaptive functions of a given variation and further emphasizing the complexity of GC physiology in wild mammals.

Social structure in a family group of Guanaco (Lama guanicoe, Ungulate): is female hierarchy based on 'prior attributes' or 'social dynamics'?

Social life involves costs and benefits mostly associated with how individuals interact with each other. The formation of hierarchies inside social groups has evolved as a common strategy to avoid high costs stemming from social interactions. Hierarchical relationships seem to be associated with different features such as body size, body condition and/or age, which determine dominance ability ('prior attributes' hypothesis). In contrast, the 'social dynamic' hypothesis suggests that an initial social context is a determinant in the formation of the hierarchy, more so than specific individual attributes. Hierarchical rank places individuals in higher positions, which presumably increases resource accessibility to their benefit, including opportunities for reproduction. We evaluate the maintenance of hierarchy in a family group of guanacos (Lama guanicoe) and evaluate the possible mechanisms involved in the stability of these interactions and their consequences. We estimate the linearity of social hierarchy and their dynamics. We find evidence of the formation of a highly linear hierarchy among females with males positioned at the bottom of the hierarchy. This hierarchy is not affected by physical characteristics or age, suggesting that it is established only through intra-group interactions. Rank is not related with calves' weight gain either; however, subordinated females, with lower rank, exhibit higher rates of allosuckling. We found no evidence of hierarchical structure in calves suggesting that hierarchical relationship in guanacos could be established during the formation of the family group. Hence, our results suggest that hierarchical dynamics could be related more to social dynamics than to prior attributes. We finally discuss the importance of hierarchies established by dominance and their role in minimizing social costs of interactions.

Fecal cortisol levels predict breeding but not survival of females in the short-lived rodent, Octodon degus.

The cort-adaptation hypothesis indicates that an association between glucocorticoid (cort) levels and fitness may vary with the extent to which reproduction or breeding effort is a major determinant of cort levels. Support for a context dependent association between cort and fitness comes mostly from relatively long-lived, bird species. We tested the hypothesis that there are gender and context (life-history) specific cort-fitness relationships in degus, a short-lived and generally semelparous social rodent. In particular, we used demographical records on a natural population to estimate adult survival through seasons and years and linked that to records of baseline cort (based on fecal cortisol metabolites). We found no evidence for a direct relationship between baseline cort and adult survival across seasons, and this lack of association was recorded irrespective of sex and life history stage. Yet, cort levels during early lactation predicted the probability that females produce a second litter during the same breeding season, supporting a connection between baseline cort levels and breeding effort. Overall, the differential effects of cort on survival and breeding supported that the extent of cort-fitness relationships depends on the fitness component examined.

Trophic interactions of the endangered Southern river otter (Lontra provocax) in a Chilean Ramsar wetland inferred from prey sampling, fecal analysis, and stable isotopes.

Non-invasive methodological approaches are highly recommended and commonly used to study the feeding ecology of elusive and threatened mammals. In this study, we use multiple lines of evidence to assess the feeding strategies of the endangered Southern river otter, by determining seasonal prey availability (electrofishing), analysis of undigested prey remains (spraints), and the use of stable isotopes (δ(15)N and δ(13)C) in otter spraints (n = 262) and prey in a wetland ecosystem of southern Chile (39°49'S, 73°15'W). Fecal and isotopic analyses suggest that the otter diet is restricted to a few prey items, particularly the less-mobile, bottom-living, and larger prey such as crayfish (Samastacus spinifrons, 86.11%) and crabs (Aegla spp., 32.45%), supplemented opportunistically by cyprinids (Cyprinus carpio, 9.55%) and catfish (Diplomystes camposensis, 5.66%). The results suggest that the river otter is highly specialized in bottom foraging. Isotopic signatures of food sources and feces revealed a mid-upper trophic position for the Southern river otter, with either higher or lower δ(15)N values than their potential prey items. δ(13)C values for river otters were less enriched than their potential food resources. We suggest that due to their narrow trophic niche and possible dependence on only a few food items, this species may be highly vulnerable to the reduction in its prey populations. Finally, maintaining the ecological interactions between Southern river otters and their prey is considered a central priority for the survival of this endangered carnivore mammal.

Aerobic power, huddling and the efficiency of torpor in the South American marsupial, Dromiciops gliroides.

During periods of cold, small endotherms depend on a continuous supply of food and energy to maintain euthermic body temperature (T(b)), which can be challenging if food is limited. In these conditions, energy-saving strategies are critical to reduce the energetic requirements for survival. Mammals from temperate regions show a wide arrange of such strategies, including torpor and huddling. Here we provide a quantitative description of thermoregulatory capacities and energy-saving strategies in Dromiciops gliroides, a Microbiotherid marsupial inhabiting temperate rain forests. Unlike many mammals from temperate regions, preliminary studies have suggested that this species has low capacity for control and regulation of body temperature, but there is still an incomplete picture of its bioenergetics. In order to more fully understand the physiological capacities of this "living fossil", we measured its scope of aerobic power and the interaction between huddling and torpor. Specifically, we evaluated: (1) the relation between basal (BMR) and maximum metabolic rate (MMR), and (2) the role of huddling on the characteristics of torpor at different temperatures. We found that BMR and MMR were above the expected values for marsupials and the factorial aerobic scope (from [Formula: see text]CO(2)) was 6.0±0.45 (using [Formula: see text]CO(2)) and 6.2±0.23 (using [Formula: see text]O(2)), an unusually low value for mammals. Also, repeatability of physiological variables was non-significant, as in previous studies, suggesting poor time-consistency of energy metabolism. Comparisons of energy expenditure and body temperature (using attached data-loggers) between grouped and isolated individuals showed that at 20°C both average resting metabolic rate and body temperature were higher in groups, essentially because animals remained non-torpid. At 10°C, however, all individuals became torpid and no differences were observed between grouped and isolated individuals. In summary, our study suggests that the main response of Dromiciops gliroides to low ambient temperature is reduced body temperature and torpor, irrespective of huddling. Low aerobic power and low time-consistency of most thermoregulatory traits of Dromiciops gliroides support the idea of poor thermoregulatory abilities in this species.

Gastrointestinal and blood parasite determination in the guanaco (Lama guanicoe) under semi-captivity conditions.

The breeding of wild animals for commercial purposes is becoming more frequent nowadays. This situation has led to an increase in contact rates between wild and domestic animals, with subsequent reciprocal transmission of parasites. In this study, we characterized the gastrointestinal and blood parasites of a group of 15 semi-captive guanacos (Lama guanicoe). We characterized gastrointestinal parasites by analyzing fecal samples through the sedimentation-flotation technique and hemoparasites by using blood smears stained with Giemsa. We found several gastrointestinal parasites including Nematoda and protozoans. The most frequently found parasites were Nematodirus sp. and Eimeria sp. In contrast with previous studies, neither Cestoda nor Fasciola were found. The only hemoparasite detected was Mycoplasma haemolamae, a parasite already described in llamas and alpacas. We conclude that the most frequent gastrointestinal parasites of semi-captive guanacos were nematodes and protozoans. Also, the hemoparasite M. haemolamae seems to be prevalent among captive populations of South American camelids. Finally, captive guanacos share several parasites with the traditional livestock. Therefore, keeping captive or semi-captive guanacos without an adequate sanitary protocol might have adverse consequences to adjacent traditional cattle farming and/or for wild animals.

Sociality, glucocorticoids and direct fitness in the communally rearing rodent, Octodon degus.

While ecological causes of sociality (or group living) have been identified, proximate mechanisms remain less clear. Recently, close connections between sociality, glucocorticoid hormones (cort) and fitness have been hypothesized. In particular, cort levels would reflect a balance between fitness benefits and costs of group living, and therefore baseline cort levels would vary with sociality in a way opposite to the covariation between sociality and fitness. However, since reproductive effort may become a major determinant of stress responses (i.e., the cort-adaptation hypothesis), cort levels might also be expected to vary with sociality in a way similar to the covariation between sociality and fitness. We tested these expectations during three years in a natural population of the communally rearing degu, Octodon degus. During each year we quantified group membership, measured fecal cortisol metabolites (a proxy of baseline cort levels under natural conditions), and estimated direct fitness. We recorded that direct fitness decreases with group size in these animals. Secondly, neither group size nor the number of females (two proxies of sociality) influenced mean (or coefficient of variation, CV) baseline cortisol levels of adult females. In contrast, cortisol increased with per capita number of offspring produced and offspring surviving to breeding age during two out of three years examined. Together, our results imply that variation in glucocorticoid hormones is more linked to reproductive challenge than to the costs of group living. Most generally, our study provided independent support to the cort-adaptation hypothesis, according to which reproductive effort is a major determinant, yet temporally variable, influence on cort-fitness covariation.

Validation of a radioimmunoassay for measuring fecal cortisol metabolites in the hystricomorph rodent, Octodon degus.

Determination of fecal steroid metabolites is a noninvasive technique that characterizes the physiological state of organisms without the physiological and psychological stress of handling. Although this technique has many applications in the study of wildlife and/or captive animals without the necessity of capturing individuals, it requires a species-specific validation before use. A complete validation includes an analytical and a physiological one. In the latter changes in fecal hormone metabolites are induced by previous manipulations of the respective plasma hormones. Here we validated a method for measuring fecal cortisol metabolites (FCM) in the hystricomorph rodent Octodon degus. We extracted feces with 80% ethanol and quantified steroids using a commercial available cortisol radioimmunoassay. We first compared baseline levels of blood cortisol and FCM, and then performed a challenge test with adrenocorticotropic hormone (ACTH) to demonstrate that FCM accurately reflect adrenocortical activity. We found a significantly positive relationship between concentrations of blood cortisol and its fecal metabolites. During the ACTH challenge test, blood cortisol levels peaked 30 min after injection, and FCM mirrored this peak with a delay of about 6 hr. Our successfully validated noninvasive method provides new opportunities for studies assessing the influence of social and ecological factors on degus under natural conditions.

Using haematological parameters to infer the health and nutritional status of an endangered black-necked swan population.

Living organisms are continuously faced with several forms of environmental perturbation, one of the most important being human activity. In this scenario, the role of physiological studies on wildlife has proved to be important given that in vivo physiological variables reflect a great deal how sensitive animals are to acute environmental changes. We studied the haematological parameters in black-necked swans (Cygnus melanocoryphus) at the Ramsar site at the Carlos Anwandter Sanctuary, which were experiencing a drastic population decrease. Through seven months, body mass (body mass corrected by total length) was reduced 30%, which was followed by significant reductions of haemoglobin concentration, haematocrit and red blood cell count. Mean cell volume and mean cell haemoglobin concentration did not change with time, whereas there was a significant increase of the white blood cells and heterophile / lymphocyte ratio. Our results, together with the published evidence, suggests that the proximal factors associated with the mass mortality and emigration of the black - necked swan population at the "Carlos Anwandter Sanctuary" was a drastic nutritional deficiency, and the potentially toxic effects of iron pollution in the waters of the Ramsar site.

Blood biochemistry reveals malnutrition in black-necked swans (Cygnus melanocoryphus) living in a conservation priority area.

The application of clinical biochemical techniques to determine the products of intermediary metabolism has proved to be a reliable approach for the study of the physiological state of animals in nature. More specifically, the determination of plasma metabolites, such as glucose, total proteins (PRO), albumin (ALB), globulins (GL), urea, uric acid, triglycerides (TG) and beta-hydroxy-butyrate (BHB), and plasma enzymes such as creatine kinase (CK) and aspartate aminotransferase (AST) in wild animals is a valuable possibility for a non-destructive assessment of health in endangered populations. Since August 2004 to January 2005, we conducted a temporal study in a conservation priority site, the "Carlos Anwandter Nature Sanctuary" to determine blood biochemistry of a wild population of black-necked swans (Cygnus melanocoryphus). This population was experiencing a drastic reduction, according to the actual knowledge about yearly fluctuations in numbers and breeding pairs. In six months, we periodically sampled about 12 swans (a total of 122 individuals), which exhibited a reduction near 30% in body mass (body mass corrected by total length). Our results showed reductions in most plasma biochemical parameters (glucose, PRO, ALB, uric acid, TG) and increase in BHB, which taken together indicated signs of chronic malnutrition. Also, the increase in AST and CK that we found, together with additional evidences of sub-lethal hepatic damage (in dead individuals), and iron pollution in aquatic plants and water confirmed that water pollution was the ultimate cause of this population reduction.

Social cues and hormone levels in male Octodon degus (Rodentia): a field test of the Challenge Hypothesis.

Social interactions are important factors determining and regulating individual behaviors. Testosterone has been related to agonistic interactions, while glucocorticoids have been related to social stress, especially during interactions of dominance. We compared testosterone and cortisol concentrations in male degus (Octodon degus, Rodentia) under laboratory conditions without male social interactions, with data from wild males in nature. Under natural conditions, males should present higher levels of testosterone during the breeding season due to social interactions (Challenge Hypothesis). Alternatively, intense social instability could act as a stressing environment, raising glucocorticoids, which inhibit testosterone concentrations. Our results show a significant increase in agonistic interactions between males during the breeding season, and disappearance of non-agonistic male interactions during this period. Hormone levels in breeding season show nonsignificant differences between laboratory groups, but testosterone concentrations in field males were significantly higher than in laboratory males. Testosterone levels were similar among pre-breeding and breeding periods, but in field animals the concentration was approximately 30% higher than in laboratory degus. In field animals, we found two different mating strategies: resident males, with territorial behavior, and transient males, displayed an opportunistic approach to females. Finally, cortisol presents a similar pattern in both laboratory and field animals; pre-breeding values of cortisol are higher than during the breeding season. This suggests that social interactions in O. degus activate a rise in testosterone, supporting the Challenge Hypothesis, and could be considered as partial support of the Social Stress Hypothesis.

Communal nesting and kinship in degus (Octodon degus).

Communal nesting is a fundamental component of many animal societies. Because the fitness consequences of this behavior vary with the relatedness among nest mates, understanding the kin structure of communally nesting groups is critical to understanding why such groups form. Observations of captive degus (Octodon degus) indicate that multiple females nest together, even when supplied with several nest boxes. To determine whether free-living degus also engage in communal nesting, we used radiotelemetry to monitor spatial relationships among adult females in a population of O. degus in central Chile. These analyses revealed that females formed stable associations of > 2-4 individuals, all of whom shared the same nest site at night. During the daytime, spatial overlap and frequency of social interactions were greatest among co-nesting females, suggesting that nesting associations represent distinct social units. To assess kinship among co-nesting females, we examined genotypic variation in our study animals at six microsatellite loci. These analyses indicated that mean pairwise relatedness among members of a nesting association (r=0.25) was significantly greater than that among randomly selected females (r=-0.03). Thus, communally nesting groups of degus are composed of female kin, making it possible for indirect as well as direct fitness benefits to contribute to sociality in this species.

Blood glucose concentration in caviomorph rodents.

Hystricomorph rodents are a group of species that belong to the suborder Hystricognathi. They mainly inhabit South American (caviomorph) and African (phiomorph) habitats. This group of rodents has a divergent insulin structure. For example, insulin in this group of rodents exhibits only 1-10% of biological activity in comparison to other mammals. Therefore, hystricomorph rodents may hypothetically be unable to regulate blood glucose concentration as non-hystricomorph mammals. In this work we evaluated blood glucose concentration in nine species of caviomorph rodents, with emphasis on species belonging to the families Abrocomidae, Ctenomyidae and Octodontidae. Specifically we: (1) measured glucose concentrations after a fasting period; and (2) conducted a glucose tolerance test. In the latter assay we used Octodon degus as a representative species of the genus Octodon. Results showed that blood glucose concentration values after fasting, and in the glucose tolerance test, were within the expected range for mammals. We postulate that this group of rodents has compensatory traits that may permit the maintenance of standard values of plasma glucose.