Anthropogenic habitat modification can reshape dispersal dynamics, social organisation, and ultimately the genetic structure of populations. In cooperatively breeding species, where philopatry and helping are common, dispersal events are rare but critical for maintaining gene flow and reducing inbreeding. Using microsatellite data (N = 211 individuals) and long-term (1985 - 2023) social kinship data from the cooperatively breeding Arabian babblers (Argya squamiceps) living in natural and modified habitats in the hyper-arid Arava Valley (Israel), we examined how habitat modification influences the social and genetic structure. We combined spatial autocorrelation analyses, within-group relatedness estimates, and social kinship to assess patterns of dispersal, connectivity, and kinship across habitats. We found high gene flow across habitats and only weak differentiation among subpopulations, consistent with recent habitat changes that do not produce strong divergence. However, subtle but significant differences emerged between natural and modified habitats. Groups inhabiting modified areas showed shorter dispersal distances and lower within-group relatedness, suggesting higher turnover and increased immigration of unrelated individuals. In contrast, groups in natural habitats maintained stronger kin-based cohesion and broader positive spatial genetic structure. Our results indicate that habitat modification does not reduce connectivity in this system but reshapes the balance between philopatry and dispersal, favouring earlier dispersal and reduced kinship within groups. Modified habitats attract and concentrate individuals from multiple origins, while natural habitats function as demographic sources. These findings corroborate previous behavioural evidence of an accelerated pace of life in modified habitats and demonstrate that such life-history adjustments are detectable in the genetic and social structure. More broadly, our study highlights how anthropogenic changes in arid ecosystems can leave rapid genetic signatures in cooperative breeders, underscoring the importance of integrating behavioural, demographic, and genetic perspectives to understand population responses to environmental change.

The role of the endocannabinoid system (ECS) in the development of depression and anxiety is being actively studied, with evidence suggesting that elevation of ECS signaling can have anxiolytic and antidepressant properties. The current study explored the therapeutic potential of Oleoyl Serine (OS), an endocannabinoid-like lipid, and HU-910, a synthetic selective Cannabinoid type 2 (CB2) receptors agonist, in depression and anxiety, using both sexes of the depressive-like genetic model: Wistar Kyoto (WKY) rats. The aim was to investigate behavioral and molecular mechanisms associated with acute and sub-chronic intraperitoneal administration of these compounds. We showed that, in females, acutely administered OS yielded antidepressant-like and anxiolytic-like effects in the Forced Swim Test (FST) and Open Field Test (OFT), respectively. In males, OS yielded acute and sub-chronic anxiolytic-like effects. HU-910 yielded an acute anxiolytic-like effect in females and an acute antidepressant-like effect in males. Sub-chronic administration of imipramine (IMI), used as a positive control, yielded an antidepressant-like effect in both sexes but an anxiogenic-like effect in females. Sub-chronic administration of all the treatments increased hippocampal Cannabinoid Receptor 1 (CNR1) mRNA expression (but not Fatty Acid Amide Hydrolase (FAAH)) in males. Exploratory in silico absorption, distribution, metabolism, and excretion (ADME) profiling suggests that sex-dependent pharmacokinetic variability may partly underlie the observed behavioral differences, in addition to possible pharmacodynamic factors. Our study provides a lead towards unraveling the putative sex differences in response to both conventional antidepressants (e.g., IMI) and emerging pharmacological agents (e.g., OS, HU-910). Further, our study helps advance the field of neuropharmacology by elucidating the anxiolytic-like and antidepressant-like effects of OS and HU-910.

Abstract Risk-taking behaviour permeates daily decision-making across many taxa and has significant impact on fitness outcomes. Previous research finds that individuals display consistent tendencies in their propensity to take risks, often labelled as a “Boldness-Shyness” personality trait. In this experimental study, we investigated repeatability in risk-taking behaviour in 241 wild vervet monkeys by measuring their responses to capture threat (via human-initiated darting procedure) and predation threat (via two predator models). We further examined the influence of socio-demographic, group identity and hormonal factors on risk-taking behaviour. We found that multiple behavioural responses, including the likelihood of approaching a food source under threat, were consistent across contexts. Risk-taking behaviour was influenced by age, sex, dominance rank, and hormonal profiles: juveniles, males, and higher-ranking individuals were more likely to approach food under (perceived) predation risk. Additionally, we observed significant among-group differences, suggesting that individuals within the same social group exhibit similar risk sensitivities, potentially due to social facilitation or shared environmental effects. The findings contribute to our understanding of animal personality and the ecological and social drivers underlying variation in risk-related behaviours.

Inter-individual differences are necessary for selection to act, while plasticity (intra-individual variation) may buffer against selection. Sleep is a critical self-maintenance behaviour but, unlike most behaviours, the causes and consequences of its inter- and intra-individual variation in wild animals is poorly understood, particularly in neonates where sleep plays a key role in development. We have shown previously that free-ranging neonate fallow deer (Dama dama) differ in sleep during the first few weeks of life. Here, we test whether individual variability in sleep is organised systematically across the population, and whether these individual differences are associated with chronic stress measured using hair cortisol, or the timing of birth. Four dimensions of sleep behaviour (total sleep time, sleep fragmentation, sleep quality, and sleep distribution over 24-h) were quantified using state-of-the-art triaxial accelerometers. We then used a multivariate mixed-effects model in a Bayesian framework to evaluate covariation between multiple dimensions of sleep behaviour, and quantify the relative importance of chronic stress and the timing of birth, while accounting for the confounding effects of environmental conditions and age. We found that the timing of birth and chronic stress were not associated with changes in sleep between individuals. While both total sleep time and the number of bouts per day declined with age, their rate of development covaried, but no other sleep dimensions covaried. Our results represent an in-depth analysis of natural variation in sleep, and show that individual differences in four aspects of sleep architecture in free-living fallow deer fawns are strong but independent of one another and unrelated to chronic stress or the timing of birth. We suggest that covariation between sleep dimensions might emerge later in life and effects of cortisol and birth timing might be very short and transient.

Maternal phenotypes can have long-term effects on offspring phenotypes. These maternal effects may begin during gestation, when maternal glucocorticoid (GC) levels may affect foetal GC levels, thereby having an organizational effect on the offspring phenotype. Recent studies have showed that maternal effects may be different between the sexes. However, how maternal GC levels relate to foetal levels is still not completely understood. Here we related, for the first time in a free-ranging large mammal, the fallow deer (Dama dama), maternal GC levels with foetal in utero GC levels. We did this in a non-invasive way by quantifying cortisol metabolites from faecal samples collected from pregnant does during late gestation, as proxy for maternal GC level. These were then related to GC levels from hair of their neonate offspring (n = 40). We have shown that maternal GC levels were positively associated with foetal GC levels, but only in female offspring. These findings highlight sex differences, which may have evolved to optimize male growth at the cost of survival.

BACKGROUND:The hypothalamic-pituitary-adrenal (HPA) and -gonadal (HPG) axes are two major pathways that connect the neural and endocrine systems in vertebrates. Factors such as prenatal stress and maternal exposure to exogenous steroids have been shown to affect these pathways during fetal development. Another less studied factor is the transfer of hormones across fetuses in multifetal pregnancies. This form of transfer has been shown to influence the morphology, anatomy, physiology, and behavior of the offspring in litter-bearing mammals, an influence termed the intrauterine position (IUP) effect. In this study, we sought to delineate how the IUP effects HPA and HPG brain receptors, peptides, and enzymes (hereafter components) in utero and how these influences may differ between males and females. METHODS:We utilized the unconventional model of culled free-ranging nutria (Myocastor coypus), with its large natural variation. We collected brain tissues from nutria fetuses and quantified the expression of key HPA and HPG components in three brain regions: prefrontal cortex, hypothalamus, and striatum. RESULTS:We found an interaction between sex and IUP in the mineralocorticoid receptor (MR), gonadotropin-releasing hormone receptor (GNRHR), androgen receptor (AR), and estrogen receptor alpha (ESR1). IUP was significant in both gonadotropin-releasing hormone (GnRH) and its receptor GNRHR, but in different ways. In the hypothalamus, fetuses adjacent to same-sex neighbors had higher expression of GnRH than fetuses neighboring the opposite sex. Conversely, in the cortex, GNRHR exhibited the inverse pattern, and fetuses that were neighboring the opposite sex had higher expression levels than those neighboring the same sex. Regardless of IUP, in most components that showed significant sex differences, female fetuses had higher mRNA expression levels than male fetuses. We also found that HPA and HPG components were highly related in the early stages of gestation, and that there was an interaction between sex and developmental stage. In the early stages of pregnancy, female component expression levels were more correlated than males', but in the last trimester of pregnancy, male components were more related to each other than female's. CONCLUSIONS:This study suggests that there are sexually different mechanisms to regulate the HPA and HPG axes during fetal development. Higher mRNA expression levels of endocrine axes components may be a mechanism to help females cope with prolonged androgen exposure over a long gestational period. Additionally, these findings suggest different coordination requirements of male and female endocrine axes during stages of fetal development.

Binge eating (BE) is consuming large amounts of food in a short time, while experiencing loss of control over eating behavior. BE can be hereditary, and juvenile stress (JS) may contribute to its onset. We examined the impact of JS on BE-like behavior, in an animal model of intergenerational BE. Twenty-four female Wistar rats received 2-h access to palatable food (PF) three or five times a week (3 TW or 5 TW) for 4 weeks, followed by the open field test (OFT). At postnatal day (PND)27-29, female offspring either underwent JS (O-JSC) or not (O-CC). At PND51-53, offspring's stress levels were assessed behaviorally. At PND70-85, offspring received 2-h access to PF three times a week to assess their BE-like tendency. Hair samples were collected afterwards. Compared to 5 TW, 3 TW had a greater binge size. In the elevated plus maze and dark\light box, in O-JSC, offspring of 3 TW (O-3TW) spent less time in the open arms and lit area compared to O-5TW. O-3TW consumed more PF than O-5TW. O-JSC consumed more than O-CC. O-3TW-JSC had higher hair CORT levels than O-3TW-CC and O-5TW-JSC. This study highlights the interplay between maternal and offspring experiences, allowing for the study of underlying mechanisms.

The menstrual cycle is characterized partially by fluctuations of the ovarian hormones estradiol (E2) and progesterone (P4), which are implicated in the regulation of cognition. Research on attention in the different stages of the menstrual cycle is sparse, and the three attentional networks (alerting, orienting and executive) and their interaction were not explored during the menstrual cycle. In the current study, we used the ANT-I (attentional network test – interactions) to examine two groups of women: naturally cycling (NC) – those with a regular menstrual cycle, and oral contraceptives (OC) – those using OC and characterized with low and steady ovarian hormone levels. We tested their performance at two time points that fit, in natural cycles, the early follicular phase and the early luteal phase. We found no differences in performance between NC and OC in low ovarian hormone states (Both phases for the OC group and early follicular phase for the NC group). However, the NC group in the early luteal phase exhibited the same pattern of responses for alerting and no-alerting conditions, resulting in a better conflict resolution (executive) when attention is oriented to the target. Results-driven exploratory regression analysis of E2 and P4 suggested that change in P4 from early follicular to early luteal phases was a mediator for the alerting effect found. In conclusion, the alerting state found with or without alertness manipulation suggests that there is a progesterone mediated activation of the alerting system during the mid-luteal phase.

1. Behavioural variation at the individual level has been shown to play an important role in animal ecology and evolution. Whereas most studies have focused on subadult or adult subjects, neonates have been relatively neglected, despite studies showing that neonates can exhibit consistent inter-individual differences during early developmental stages. 2. Steroid hormones, including glucocorticoids (e.g. cortisol) and androgens (e.g. testosterone), play a crucial role in foetal development and maturation and could therefore drive neonate behaviour, although this relationship is poorly understood in wild animal populations. 3. Our study addresses these knowledge gaps by investigating the association between neonate fallow deer Dama dama fawn inter-individual variability in behavioural response to human handling and hair cortisol and testosterone levels. 4. We found strong evidence that individual neonates display repeatable differences in the way they cope with a risky situation during their first days of life, and showed how these differences are linked to cortisol and testosterone levels accumulated in utero. We showed that, when both steroids are included in the same model, neonates with high cortisol and low testosterone levels coped in a more proactive way with human handling (higher heart rate during handling and shorter latency to leave when released) compared to those with low cortisol and high testosterone levels (lower heart rate and longer latency to leave). These results provide novel insights into the proximate mechanism leading to neonate inter-individual variation in a wild population of large mammals.

Maternal resources mediate fetal growth and development. This study analyzes the association between maternal cortisol and testosterone levels in late pregnancy and litter size in sheep. Concentrations of cortisol and testosterone in the plasma and wool were determined by enzyme-linked immunosorbent assay (ELISA) kits in Afec-Assaf ewes with one to four fetuses. Concentrations of cortisol in the plasma at 130 days of gestation, and in wool grown in the last 2 months of gestation were greater (P < 0.05) in ewes lambing two or more lambs, compared to ewes producing a single lamb. Whereas there was no association between litter size and plasma concentration of testosterone at 130 days of gestation (P > 0.05), testosterone concentration in the wool was significantly associated with litter size (P < 0.05). We suggest that elevated cortisol and testosterone levels in ewes with multiple fetuses may serve as a mechanism to lower fetal weight, thereby decreasing fetus-related metabolic load in prolific sheep.

Glucocorticoid hormone levels vary within a forager based upon environmental stressors such as illumination and riskier habitats, and a forager’s response to environmental variables depends upon its glucocorticoid levels. Here, we report on a laboratory experiment in which we manipulated cortisol in Allenbyi’s gerbils ( Gerbillus andersoni allenbyi ) to test the relationship between cortisol and behavior. We then quantified the resulting blood cortisol levels and feeding behavior in gerbils. Thirty gerbils were injected with 21-day slow-release cortisol pellets drawn from 5 different dosages. We quantified the physiological response to pellet implantation in gerbils by measuring cortisol level in blood serum using ELISA (Enzyme Linked Immunosorbent Assay). We fed gerbils daily by mixing millet seeds into the sand inside rodent cages and measured the remaining seeds the following day to quantify feeding efforts. Some evidence supports that subcutaneous supplementation of glucocorticoids (GCs) in the gerbils led to higher blood serum levels. Cortisol levels varied according to time period of measurement. Gerbils that received lower dosages consumed most of the food presented to them when compared to those receiving the highest doses. In this manner, we delineate a pattern on cortisol hormone level variation over time following dosing and consequences in feeding behavior.

-Although testosterone (T) is a key regulator in vertebrate development, physiology, and behaviour in both sexes, studies suggest that its regulation may be sex-specific. We measured circulating T levels in Baluchistan gerbils (Gerbilles nanus) in the field and in the lab all year round and found no significant sex differences. However, we observed sex differences in circulating T levels following gonadotropin-releasing hormone (GnRH) challenge and T implants in this non-model species. Whereas only males elevated T following a GnRH challenge, females had higher serum T concentrations following T implant insertion. These differences may be a result of different points of regulation along the hypothalamic-pituitary-gonadal (HPG) axis. Consequently, we examined sex differences in the mRNA expression of the androgen receptor (AR) in multiple brain regions. We identified AR and I3-actin sequences in assembled genomic sequences of members of the Gerbillinae, which were analogous to rat sequences, and designed primers for them. The distribution of the AR in G. nanus brain regions was similar to documented expression profiles in rodents. We found lower AR mRNA levels in females in the striatum. Additionally, G. nanus that experienced housing in mixed-sex pairs had higher adrenal AR expression than G. nanus that were housed alone. Regulation of the gerbil HPG axis may reflect evolutionary sex differences in lifehistory strategies, with males ready to reproduce when receptive females are available, while the possible reproductive costs associated with female T direct its regulation upstream.

Food-animal welfare is a major ethical and social concern. Pork is the most consumed meat worldwide, with over a billion pigs slaughtered annually. Most of these pigs routinely undergo painful surgical procedures (surgical castration, tail docking, teeth clipping), which farmers often reluctant to avoid, claiming it would increase cost and reduce production efficiency. Herein, this study indicates that these procedures compromise pigs' health and condition. Replacing surgical castration with immunocastration, avoiding tail docking and teeth clipping, and providing environmental enrichment, resulted in significant increase in weight gain, lowered risks for injuries and death, and reduced saliva and hair cortisol, both biomarkers for stress. Testosterone and DHEA analyses confirmed that immunocastration was an effective alternative to surgical castration. Economic models for the entire US swine market revealed that following across-the-board acceptance of this management, pork meat price is expected to drop, while the total annual social welfare (combined consumer and producer surplus) is expected to increase by $US 1.48 to 1.92 billion. In conclusion, sustainable swine farming management can be beneficial for both animals and farmers. Applying such welfare-friendly management is expected to reduce stress, enhance piglet/pig welfare and production, and improve the economics of swine operations in the global agro-food system.

Testosterone is a key regulator in vertebrate development, physiology and behaviour. Whereas technology allows extraction of a wealth of genetic information from extant as well as extinct species, complementary information on steroid hormone levels may add a social, sexual and environmental context. Hair shafts have been previously used to sequence DNA from >50000 C-14 years old Siberian woolly mammoths (Mammuthus primigenius). Hair-testing has also been used to measure endogenous steroids in multiple extant species. Here we use small quantities of woolly mammoth hair samples to measure testosterone, and a genomics-based approach to determine sex, in permafrost-preserved mammoths dated to c. 10000-60000 C-14 years. Our validated method opens up exciting opportunities to measure multiple steroids in keratinized tissues from extinct populations of mammals. This may be specifically applied to investigating life histories, including the extinct Quaternary megafauna populations whose remains are preserved in the permafrost throughout the northern hemisphere.

Testosterone plays multiple roles in the regulation of development, physiology, reproduction, and behavior. Age-related testosterone declines are expected in the population. However, measuring circulating testosterone is especially challenging because concentrations are labile, responding to social situations and challenges. Matrices that integrate long-term testosterone levels are therefore valuable as biomarkers of endogenous levels as well as chronic exposures. Here, we report on a simple method to extract and measure accumulated testosterone from human fingernails using commercial enzyme immunoassay kits. Furthermore, we demonstrate known human testosterone sex and age trends. Our method is especially useful for quantifying testosterone in men's nails, where a small amount of matrix is required. Thus, this approach is a potential tool for biomonitoring endogenous as well as exogenous testosterone exposure. We suggest considering nails as an alternative matrix for quantifying other steroids as well.

Hair analysis is emerging as a popular tool to examine stress and reproduction hormone levels in wild mammals. The reliability of this approach, however, depends on an understanding of steroid hormone incorporation into hair as well as appropriate validations. We reviewed studies that have examined steroid hormones in wildlife hair with the goal of summarizing the analytical, physiological, and biological evidence that this approach is meaningful. Accordingly, we differentiated among validations aimed at evaluating the reliability of the analytical method versus those designed to assess whether hormone levels in hair reflect physiologically meaningful processes in the target species. Our literature survey revealed that endogenous steroids have been examined in hair from 40 species of nonhuman animals across seven mammalian classes. Although the majority (85%) of 72 studies reported analytical validations of the method, physiological validations have only been reported for five species. Moreover, results of physiological validations were inconsistent among studies. This highlights the need for further research, carefully designed to differentiate between the multiple purported models of steroid incorporation into hair in species with different types of hair and different hair growth patterns. To complement our review of published studies, we present new data supporting a positive relationship between levels of the steroid, cortisol, in hair and blood across eight mammalian species. In addition, we present novel results from a laboratory‐based study showing variable hair growth in genetically identical laboratory mice that were kept under controlled conditions. Synthesis and applications. Collectively, this Review reveals substantial progress towards the validation of stress hormone assays in hair from a variety of wildlife species. Further validations of reproductive steroids, combined with appropriate physiological validations, would expand the potential applications of hair analyses in wildlife research. As a key example, physiological data can provide mechanistic insights into species’ responses to change and may therefore contribute to conservation planning.

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.

Testosterone (T) is a key androgen that mediates vertebrate molecular, cellular, and behavioral processes. Its manipulation is therefore of interest to a vast number of researchers studying animal behavior and reproduction, among others. Here, the usage of silastic implants across wildlife species is reviewed, and a method to manipulate rock hyrax (Procavia capensis) testosterone levels using silastic implants is presented. Using a series of in-vitro and in-vivo experiments, the secretion patterns of silastic tubes and silastic glue were tested and were surprisingly found to be similar. In addition, we studied endogenous T levels in wild-captured rock hyraxes (Procavia capensis), and using T implants succeeded in elevating T to the maximal physiological concentrations recorded during the mating period. The number of implants that were inserted was the only predictor of T levels, and seven 20mm implants were found to be the optimal dose. Implants induced sexual behaviors in the non-reproductive period. The duration of time that the implants were in the hyrax was the only significant factor that influenced the amount of T left over in the implant once it was removed. All together we affirm that T implants may offer a versatile tool for wildlife behavioral research by elevating T levels in the non-breeding period to maximal breeding levels.

Steroids play multiple roles in the regulation of development, physiology, reproduction, and behavior. Measuring circulating steroids is especially challenging since concentrations are extremely labile, responding to stressors within minutes. Matrices that integrate long-term steroid levels are therefore valuable as biomarkers of baseline, as well as chronic steroid exposures. Here we report on a simple method to extract and measure accumulated testosterone from human fingernails using commercial EIA kits. Further, we demonstrate known human testosterone sex and age trends. Thus, this method is a potential tool for biomonitoring endogenous as well as exogenous steroid exposure.

The parasite Trypanosoma brucei is the causative agent of human African sleeping sickness. T. brucei genes are constitutively transcribed in polycistronic units that are processed by trans-splicing and polyadenylation. All mRNAs are trans-spliced to generate mRNAs with a common 5' exon derived from the spliced leader RNA (SL RNA). Persistent endoplasmic reticulum (ER) stress induces the spliced leader silencing (SLS) pathway, which inhibits trans-splicing by silencing SL RNA transcription, and correlates with increased programmed cell death. We found that during ER stress induced by SEC63 silencing or low pH, the serine-threonine kinase PK3 translocated from the ER to the nucleus, where it phosphorylated the TATA-binding protein TRF4, leading to the dissociation of the transcription preinitiation complex from the promoter of the SLRNA encoding gene. PK3 loss of function attenuated programmed cell death induced by ER stress, suggesting that SLS may contribute to the activation of programmed cell death.