Urban-like night illumination reduces melatonin release in European blackbirds (Turdus merula): implications of city life for biological time-keeping of songbirds

<p>Introduction: Artificial light-at-night is known to affect a broad array of behaviours and physiological processes. In urbanized bird species, light-at-night advances important biological rhythms such as daily cycles of activity/rest and timing of reproduction, but our knowledge of the underlying physiological mechanisms is limited. Given its role as chronobiological signal, melatonin is a strong candidate for mediating the effects of light-at-night.</p> <p>Results: We exposed urban and rural European blackbirds (Turdus merula) to two light treatments equal in photoperiod but with different light intensities at night. The control group was exposed to 0.0001 lux (almost darkness), while the experimental group was exposed to 0.3 lux at night, simulating conditions recorded previously on free-living urban blackbirds. We obtained diel profiles of plasma melatonin for all birds in summer (July) and winter (January), while simultaneously recording locomotor activity. Daily patterns of melatonin concentrations were clearly affected by light-at-night in both seasons. In winter, melatonin concentrations of light-at-night birds were lower in the early and late night than in those of birds kept in darkness. In summer, melatonin concentrations of the light-at-night birds were lower through all night compared to birds kept in darkness. Locomotor activity in light-at-night birds was overall higher than in control individuals, both during the day and at night, and it increased sharply before dawn. In winter, the amount of activity before dawn in the light-at-night group correlated with changes in melatonin from midnight to late night: the greater the decrease in melatonin, the greater the amount of pre-dawn activity. Urban and rural birds responded similarly to light-at-night with respect to melatonin, but differed in their behaviour, with rural birds showing more locomotor activity than urban counterparts.</p> <p>Conclusions: This study points to reduced melatonin release at night as a potential physiological mechanism underlying the advanced onset of morning activity of urbanized birds. Based on the pattern of melatonin secretion, we suggest that birds responded to light-at-night as if they were exposed to a longer day than birds kept under dark nights.</p&gt

Building Babies - Chapter 16

In contrast to birds, male mammals rarely help to raise the offspring. Of all mammals, only among rodents, carnivores, and primates, males are sometimes intensively engaged in providing infant care (Kleiman and Malcolm 1981). Male caretaking of infants has long been recognized in nonhuman primates (Itani 1959). Given that infant care behavior can have a positive effect on the infant’s development, growth, well-being, or survival, why are male mammals not more frequently involved in “building babies”? We begin the chapter defining a few relevant terms and introducing the theory and hypotheses that have historically addressed the evolution of paternal care. We then review empirical findings on male care among primate taxa, before focusing, in the final section, on our own work on paternal care in South American owl monkeys (Aotus spp.). We conclude the chapter with some suggestions for future studies.Deutsche Forschungsgemeinschaft (HU 1746/2-1) Wenner-Gren Foundation, the L.S.B. Leakey Foundation, the National Geographic Society, the National Science Foundation (BCS-0621020), the University of Pennsylvania Research Foundation, the Zoological Society of San Dieg

Methodological considerations in the analysis of fecal glucocorticoid metabolites in tufted capuchins (Cebus apella)

Analysis of fecal glucocorticoid (GC) metabolites has recently become the standard method to monitor adrenocortical activity in primates noninvasively. However, given variation in the production, metabolism, and excretion of GCs across species and even between sexes, there are no standard methods that are universally applicable. In particular, it is important to validate assays intended to measure GC production, test extraction and storage procedures, and consider the time course of GC metabolite excretion relative to the production and circulation of the native hormones. This study examines these four methodological aspects of fecal GC metabolite analysis in tufted capuchins (Cebus apella). Specifically, we conducted an adrenocorticotrophic hormone (ACTH) challenge on one male and one female capuchin to test the validity of four GC enzyme immunoassays (EIAs) and document the time course characterizing GC me- tabolite excretion in this species. In addition, we compare a common field-friendly technique for extracting fecal GC metabolites to an established laboratory extraction methodology and test for effects of storing “field extracts” for up to 1 yr. Results suggest that a corticosterone EIA is most sensitive to changes in GC production, provides reliable measures when extracted according to the field method, and measures GC metabolites which remain highly stable after even 12 mo of storage. Further, the time course of GC metabolite excretion is shorter than that described yet for any primate taxa. These results provide guidelines for studies of GCs in tufted capuchins, and underscore the importance of validating methods for fecal hormone analysis for each species of interest

Effects of the social environment during adolescence on the development of social behaviour, hormones and morphology in male zebra finches (Taeniopygia guttata)

Abstract Background Individual differences in behaviour are widespread in the animal kingdom and often influenced by the size or composition of the social group during early development. In many vertebrates the effects of social interactions early in life on adult behaviour are mediated by changes in maturation and physiology. Specifically, increases in androgens and glucocorticoids in response to social stimulation seem to play a prominent role in shaping behaviour during development. In addition to the prenatal and early postnatal phase, adolescence has more recently been identified as an important period during which adult behaviour and physiology are shaped by the social environment, which so far has been studied mostly in mammals. We raised zebra finches ( Taeniopygia guttata ) under three environmental conditions differing in social complexity during adolescence\ua0-\ua0juvenile pairs, juvenile groups, and mixed-age groups - and studied males\u2019 behavioural, endocrine, and morphological maturation, and later their adult behaviour. Results As expected, group-housed males exhibited higher frequencies of social interactions. Group housing also enhanced song during adolescence, plumage development, and the frequency and intensity of adult courtship and aggression. Some traits, however, were affected more in juvenile groups and others in mixed-age groups. Furthermore, a testosterone peak during late adolescence was suppressed in groups with adults. In contrast, corticosterone concentrations did not differ between rearing environments. Unexpectedly, adult courtship in a test situation was lowest in pair-reared males and aggression depended upon the treatment of the opponent with highest rates shown by group-reared males towards pair-reared males. This contrasts with previous findings, possibly due to differences in photoperiod and the acoustic environment. Conclusion Our results support the idea that effects of the adolescent social environment on adult behaviour in vertebrates are mediated by changes in social interactions affecting behavioural and morphological maturation. We found no evidence that long-lasting differences in behaviour reflect testosterone or corticosterone levels during adolescence, although differences between juvenile and mixed-age groups suggest that testosterone and song behaviour during late adolescence may be associated

Do Seasonal Glucocorticoid Changes Depend on Reproductive Investment? A Comparative Approach in Birds

Animals go through different life history stages such as reproduction, moult, or migration, of which some are more energy-demanding than others. Baseline concentrations of glucocorticoid hormones increase during moderate, predictable challenges and thus are expected to be higher when seasonal energy demands increase, such as during reproduction. By contrast, stress-induced glucocorticoids prioritize a survival mode that includes reproductive inhibition. Thus, many species down-regulate stress-induced glucocorticoid concentrations during the breeding season. Interspecific variation in glucocorticoid levels during reproduction has been successfully mapped onto reproductive investment, with species investing strongly in current reproduction (fast pace of life) showing higher baseline and lower stress-induced glucocorticoid concentrations than species that prioritize future reproduction over current attempts (slow pace of life). Here we test the >glucocorticoid seasonal plasticity hypothesis>, in which we propose that interspecific variation in seasonal changes in glucocorticoid concentrations from the non-breeding to the breeding season will be related to the degree of reproductive investment (and thus pace of life). We extracted population means for baseline (for 54 species) and stress-induced glucocorticoids (for 32 species) for the breeding and the non-breeding seasons from the database >HormoneBase>, also calculating seasonal glucocorticoid changes. We focused on birds because this group offered the largest sample size. Using phylogenetic comparative methods, we first showed that species differed consistently in both average glucocorticoid concentrations and their changes between the two seasons, while controlling for sex, latitude, and hemisphere. Second, as predicted seasonal changes in baseline glucocorticoids were explained by clutch size (our proxy for reproductive investment), with species laying larger clutches showing a greater increase during the breeding season-especially in passerine species. In contrast, changes in seasonal stress-induced levels were not explained by clutch size, but sample sizes were more limited. Our findings highlight that seasonal changes in baseline glucocorticoids are associated with a species' reproductive investment, representing an overlooked physiological trait that may underlie the pace of life

IUCN Conservation Status Does Not Predict Glucocortoid Concentrations in Reptiles and Birds

Circulating glucocorticoids (GCs) are the most commonly used biomarkers of stress in wildlife. However, their utility as a tool for identifying and/or managing at-risk species has varied. Here, we took a very broad approach to conservation physiology, asking whether International Union for the Conservation of Nature (IUCN) listing status (concern versus no obvious concern) and/or location within a geographic range (edge versus non-edge) predicted baseline and post-restraint concentrations of corticosterone (CORT) among many species of birds and reptiles. Even though such an approach can be viewed as coarse, we asked in this analysis whether CORT concentrations might be useful to implicate species at risk. Indeed, our effort, relying on HormoneBase, a repository of data on wildlife steroids, complements several other large-scale efforts in this issue to describe and understand GC variation. Using a phylogenetically informed Bayesian approach, we found little evidence that either IUCN status or edge/non-edge location in a geographic distribution were related to GC levels. However, we did confirm patterns described in previous studies, namely that breeding condition and evolutionary relatedness among species predicted some GC variation. Given the broad scope of our work, we are reluctant to conclude that IUCN status and location within a range are unrelated to GC regulation. We encourage future more targeted efforts on GCs in at-risk populations to reveal how factors leading to IUCN listing or the environmental conditions at range edges impact individual performance and fitness, particularly in the mammals, amphibians, and fish species we could not study here because data are currently unavailable

HormoneBase, a Population-Level Database of Steroid Hormone Levels Across Vertebrates

Hormones are central regulators of organismal function and flexibility that mediate a diversity of phenotypic traits from early development through senescence. Yet despite these important roles, basic questions about how and why hormone systems vary within and across species remain unanswered. Here we describe HormoneBase, a database of circulating steroid hormone levels and their variation across vertebrates. This database aims to provide all available data on the mean, variation, and range of plasma glucocorticoids (both baseline and stress-induced) and androgens in free-living and un-manipulated adult vertebrates. HormoneBase (www.HormoneBase.org) currently includes \u3e6,580 entries from 476 species, reported in 648 publications from 1967 to 2015, and unpublished datasets. Entries are associated with data on the species and population, sex, year and month of study, geographic coordinates, life history stage, method and latency of hormone sampling, and analysis technique. This novel resource could be used for analyses of the function and evolution of hormone systems, and the relationships between hormonal variation and a variety of processes including phenotypic variation, fitness, and species distributions

Macroevolutionary Patterning in Glucocorticoids Suggests Different Selective Pressures Shape Baseline and Stress-Induced Levels

Glucocorticoid (GC) hormones are important phenotypic mediators across vertebrates, but their circulating concentrations can vary markedly. Here we investigate macroevolutionary patterning in GC levels across tetrapods by testing seven specific hypotheses about GC variation and evaluating whether the supported hypotheses reveal consistent patterns in GC evolution. If selection generally favors the “supportive” role of GCs in responding effectively to challenges, then baseline and/or stress-induced GCs may be higher in challenging contexts. Alternatively, if selection generally favors “protection” from GC-induced costs, GCs may be lower in environments where challenges are more common or severe. The predictors of baseline GCs were all consistent with supportive effects: levels were higher in smaller organisms and in those inhabiting more energetically demanding environments. During breeding, baseline GCs were also higher in populations and species with fewer lifetime opportunities to reproduce. The predictors of stress-induced GCs were instead more consistent with the protection hypothesis: during breeding, levels were lower in organisms with fewer lifetime reproductive opportunities. Overall, these patterns indicate a surprising degree of consistency in how some selective pressures shape GCs across broad taxonomic scales; at the same time, in challenging environments selection appears to operate on baseline and stress-induced GCs in distinct ways

Metabolic Scaling of Stress Hormones in Vertebrates

Glucocorticoids (GCs) are stress hormones that can strongly influence physiology, behavior, and an organism’s ability to cope with environmental change. Despite their importance, and the wealth of studies that have sought to understand how and why GC concentrations vary within species, we do not have a clear understanding of how circulating GC levels vary within and across the major vertebrate clades. New research has proposed that much interspecific variation in GC concentrations can be explained by variation in metabolism and body mass. Specifically, GC concentrations should vary proportionally with mass-specific metabolic rates and, given known scaling relationships between body mass and metabolic rate, GC concentrations should scale to the -1/4 power of body mass and to the power of 1 with mass-specific metabolic rate. Here, we use HormoneBase, the newly compiled database that includes plasma GC concentrations from free-living and unmanipulated vertebrates, to evaluate this hypothesis. Specifically, we explored the relationships between body mass or mass-specific metabolic rate and either baseline or stress-induced GC (cortisol or corticosterone) concentrations in tetrapods. Our phylogenetically-informed models suggest that, whereas the relationship between GC concentrations and body mass across tetrapods and among mammals is close to -1/4 power, this relationship does not exist in amphibians, reptiles, and birds. Moreover, with the exception of a positive association between stress-induced GC concentrations and mass-specific metabolic rate in birds, we found little evidence that GC concentrations are linked to metabolic rate, although the number of species sampled was quite limited for amphibians and somewhat so for reptiles and mammals. Nevertheless, these results stand in contrast to the generally accepted association between the two and suggest that our observed positive association between body mass and GC concentrations may not be due to the well-established link between mass and metabolism. Large-scale comparative approaches can come with drawbacks, such as pooling and pairing observations from separate sources. However, these broad analyses provide an important counterbalance to the majority of studies examining variation in GC concentrations at the population or species level, and can be a powerful approach to testing both long-standing and new questions in biology

Intralocus conflicts associated with a supergene

This is the final version. Available from Nature Research via the DOI in this record. Data Availability: The datasets generated and analysed during the current study are available in Edmond the Open Research Data Repository of the Max Planck Society, https://doi.org/10.17617/3.71. Source Data are provided within the Source Data file. Source data are provided with this paper.The code for the evolutionary model and all statistical analyses are available as R scripts in Edmond the Open Research Data Repository of the Max Planck Society, https://doi.org/10.17617/3.71.Chromosomal inversions frequently underlie major phenotypic variation maintained by divergent selection within and between sexes. Here we examine whether and how intralocus conflicts contribute to balancing selection stabilizing an autosomal inversion polymorphism in the ruff Calidris pugnax. In this lekking shorebird, three male mating morphs (Independents, Satellites and Faeders) are associated with an inversion-based supergene. We show that in a captive population, Faeder females, who are smaller and whose inversion haplotype has not undergone recombination, have lower average reproductive success in terms of laying rate, egg size and offspring survival than Independent females, who lack the inversion. Satellite females, who carry a recombined inversion haplotype and have intermediate body size, more closely resemble Independent than Faeder females in reproductive performance. We inferred that the lower reproductive output of Faeder females is primarily balanced by higher than average reproductive success of individual Faeder males, driven by negative frequency-dependent selection. These findings suggest that intralocus conflicts may play a major role in the evolution and maintenance of supergene variants.Projekt DEA