Glucocorticoids enhance and suppress heart rate and behaviour in time dependent manner in greylag geese (Anser anser)

Supervised machine learning aided behavior classification in pigeons

Manual behavioral observations have been applied in both environment and laboratory experiments in order to analyze and quantify animal movement and behavior. Although these observations contributed tremendously to ecological and neuroscientific disciplines, there have been challenges and disadvantages following in their footsteps. They are not only time-consuming, labor-intensive, and error-prone but they can also be subjective, which induces further difficulties in reproducing the results. Therefore, there is an ongoing endeavor towards automated behavioral analysis, which has also paved the way for open-source software approaches. Even though these approaches theoretically can be applied to different animal groups, the current applications are mostly focused on mammals, especially rodents. However, extending those applications to other vertebrates, such as birds, is advisable not only for extending species-specific knowledge but also for contributing to the larger evolutionary picture and the role of behavior within. Here we present an open-source software package as a possible initiation of bird behavior classification. It can analyze pose-estimation data generated by established deep-learning-based pose-estimation tools such as DeepLabCut for building supervised machine learning predictive classifiers for pigeon behaviors, which can be broadened to support other bird species as well. We show that by training different machine learning and deep learning architectures using multivariate time series data as input, an F1 score of 0.874 can be achieved for a set of seven distinct behaviors. In addition, an algorithm for further tuning the bias of the predictions towards either precision or recall is introduced, which allows tailoring the classifier to specific needs.

Glucocorticoid metabolites in an ex situ nocturnal bird, the tropical screech owl Megascops choliba: effects of sex, activity period and inter-individual variation

Glucocorticoids mediate physiological processes to obtain energy, presenting daily variation in basal levels that may be related to behavioural activity pattern. Identification of plasticity in the secretion of these hormones is essential to understand their effects on physiology and behaviour of wild birds and, therefore, their success in their natural or artificial environment. Serial endocrine evaluations are facilitated by implementing non-invasive methodologies that minimize possible effects of manipulation on the animal's physiological variables. However, non-invasive endocrine-behavioural studies in nocturnal birds, such as owls, are immature. The present work aimed to validate an enzyme immunoassay (EIA) to quantify glucocorticoid metabolites (MGC) in Megascops choliba as well as to evaluate differences in their production at the individual, sexual or daily level. We recorded the behaviour of nine owls during three continuous days to establish activity budget under captive conditions and aiming to correlate with daily MGC variation. The EIA proved to be effective in analytical assays and in pharmacological testing with synthetic ACTH, validating this immunoassay for the species. Additionally, individual differences in MGC production were confirmed in relation to the time of day, especially at 1700 and 2100, but not in relation to sex. During night hours, the owls showed greater behavioural activity, positively related to MGC values. Higher MGC concentrations were significantly related to greater expressions of active behaviours, such as maintenance, while lower MGC concentrations were recorded during moments of higher alertness and resting. The results presented show daily MGC variation to be inversed in this nocturnal species. Our findings can aid future theoretical studies of daily rhythm and evaluations of challenging and/or disturbing situations that result in changes in behaviour or hormonal cascades of these changes in ex situ populations of owls.

A colonial-nesting seabird shows no heart-rate response to drone-based population surveys

Aerial drones are increasingly being used as tools for ecological research and wildlife monitoring in hard-to-access study systems, such as in studies of colonial-nesting birds. Despite their many advantages over traditional survey methods, there remains concerns about possible disturbance effects that standard drone survey protocols may have on bird colonies. There is a particular gap in the study of their influence on physiological measures of stress. We measured heart rates of incubating female common eider ducks (Somateria mollissima) to determine whether our drone-based population survey affected them. To do so, we used heart-rate recorders placed in nests to quantify their heart rate in response to a quadcopter drone flying transects 30 m above the nesting colony. Eider heart rate did not change from baseline (measured in the absence of drone survey flights) by a drone flying at a fixed altitude and varying horizontal distances from the bird. Our findings suggest that carefully planned drone-based surveys of focal species have the potential to be carried out without causing physiological impacts among colonial-nesting eiders.

Mirror Self-Recognition in Pigeons: Beyond the Pass-or-Fail Criterion

Spontaneous mirror self-recognition is achieved by only a limited number of species, suggesting a sharp "cognitive Rubicon" that only few can pass. But is the demarcation line that sharp? In studies on monkeys, who do not recognize themselves in a mirror, animals can make a difference between their mirror image and an unknown conspecific. This evidence speaks for a gradualist view of mirror self-recognition. We hypothesize that such a gradual process possibly consists of at least two independent aptitudes, the ability to detect synchronicity between self- and foreign movement and the cognitive understanding that the mirror reflection is oneself. Pigeons are known to achieve the first but fail at the second aptitude. We therefore expected them to treat their mirror image differently from an unknown pigeon, without being able to understand that the mirror reflects their own image. We tested pigeons in a task where they either approached a mirror or a Plexiglas barrier to feed. Behind the Plexiglas an unknown pigeon walked at the same time toward the food bowl. Thus, we pitched a condition with a mirror-self and a foreign bird against each other, with both of them walking close toward the food bowl. By a detailed analysis of a whole suit of behavioral details, our results make it likely that the foreign pigeon was treated as a competitor while the mirror image caused hesitation as if being an uncanny conspecific. Our results are akin to those with monkeys and show that pigeons do not equal their mirror reflection with a conspecific, although being unable to recognize themselves in the mirror.

Damage-Fitness Model: the missing piece in integrative stress models

Over the last decade, several theoretical models have been put forth to describe how animals respond to adverse environments and how this response changes under different physiological demands across life history stages. These models capture the context- and condition-dependent nature of stress responses. Yet, application of the models has been limited thus far in part because each model addresses different aspects of the problems facing the field of stress biology. Thus, there is a need for a unifying theoretical model that incorporates changes in physiological demand with life history stages and age, intricate relationships among physiological systems, and biphasic nature of stress responses. Here, I propose a new integrative framework, the Damage-Fitness Model. In this model, regulators, such as DNA repair mechanisms and glucocorticoids, work together as anti-damage mechanisms to minimize damage at both the cellular and organismal level. When the anti-damage regulators are insufficient or inappropriate, persistent damage accumulates. Previous studies indicate that these damage directly impact reproductive performance, disease risk, and survival. The types of regulators, the threshold at which they are initiated, and the magnitude of the responses are shaped by developmental and current environments. This model unites existing theoretical models by shifting our focus from physiological responses to downstream consequences of the stress responses, circumventing context specificity. Discussions include (1) how the proposed model relates to existing models, (2) steps to test the new model, and (3) how this model can be used to better assess the health of individuals and a population. Lay summary The field of stress physiology faces a challenge of characterizing dynamic cellular, physiological, and behavioral responses when animals encounter a stressor. This paper proposes a new theoretical model which links stress avoidance, damage repair and accumulation, and fitness components.

Social and environmental factors modulate leucocyte profiles in free-living Greylag geese (Anser anser)

Background

Blood parameters such as haematocrit or leucocyte counts are indicators of immune status and health, which can be affected, in a complex way, by exogenous as well as endogenous factors. Additionally, social context is known to be among the most potent stressors in group living individuals, therefore potentially influencing haematological parameters. However, with few exceptions, this potential causal relationship received only moderate scientific attention.

Methods

In a free-living and individually marked population of the highly social and long-lived Greylag goose, Anser anser, we relate variation in haematocrit (HCT), heterophils to lymphocytes ratio (H/L) and blood leucocyte counts to the following factors: intrinsic (sex, age, raising condition, i.e. goose- or hand-raised), social (pair-bond status, pair-bond duration and parental experience) and environmental (biologically relevant periods, ambient temperature) factors. Blood samples were collected repeatedly from a total of 105 focal birds during three biologically relevant seasons (winter flock, mating season, summer).

Results

We found significant relationships between haematological parameters and social as well as environmental factors. During the mating season, unpaired individuals had higher HCT compared to paired and family individuals and this pattern reversed in fall. Similarly, H/L ratio was positively related to pair-bond status in a seasonally dependent way, with highest values during mating and successful pairs had higher H/L ratio than unsuccessful ones. Also, absolute number of leucocytes tended to vary depending on raising condition in a seasonally dependent way.

Discussion

Haematology bears a great potential in ecological and behavioural studies on wild vertebrates. In sum, we found that HTC, H/L ratio and absolute number of leucocytes are modulated by social factors and conclude that they may be considered valid indicators of individual stress load.

Glucocorticoids, aerobic physiology, and locomotor behavior in California mice

The glucocorticoid hormones corticosterone (CORT) and cortisol influence numerous physiological, morphological, and behavioral functions. However, few studies have addressed possible relationships between individual differences in glucocorticoid concentrations and whole-animal performance or metabolism. Because CORT is important in glucose regulation and energy metabolism and can influence activity levels, we hypothesized that individual variation in baseline circulating CORT levels would correlate with individual differences in energy expenditure (routine and maximal), aerobic physiology, voluntary exercise on wheels, and organ masses. We tested this hypothesis in the California mouse (Peromyscus californicus). We collected data from 54 adult, colony-bred mice on baseline CORT levels (measured near both the circadian peak and the circadian trough), voluntary wheel running and its energetic costs, maximal oxygen consumption during forced treadmill exercise ([Formula: see text]), basal metabolic rate, and relative organ masses. We found surprisingly few statistically significant relationships among CORT, energy metabolism, behavior, and organ masses, and these relationships appeared to differ between males and females. These findings suggest that individual differences in baseline CORT levels are not an important determinant of voluntary activity levels or aerobic performance in California mice.