Unfamiliar Males Research Articles

Persistent vocal learning in an aging open-ended learner reflected in neural FoxP2 expression

BackgroundMost vocal learning species exhibit an early critical period during which their vocal control neural circuitry facilitates the acquisition of new vocalizations. Some taxa, most notably humans and parrots, retain some degree of neurobehavioral plasticity throughout adulthood, but both the extent of this plasticity and the neurogenetic mechanisms underlying it remain unclear. Differential expression of the transcription factor FoxP2 in both songbird and parrot vocal control nuclei has been identified previously as a key pattern facilitating vocal learning. We hypothesize that the resilience of vocal learning to cognitive decline in open-ended learners will be reflected in an absence of age-related changes in neural FoxP2 expression. We tested this hypothesis in the budgerigar (Melopsittacus undulatus), a small gregarious parrot in which adults converge on shared call types in response to shifts in group membership. We formed novel flocks of 4 previously unfamiliar males belonging to the same age class, either “young adult” (6 mo − 1 year) or “older adult” (≥ 3 year), and then collected audio-recordings over a 20-day learning period to assess vocal learning ability. Following behavioral recording, immunohistochemistry was performed on collected neural tissue to measure FoxP2 protein expression in a parrot vocal learning center, the magnocellular nucleus of the medial striatum (MMSt), and its adjacent striatum.ResultsAlthough older adults show lower vocal diversity (i.e. repertoire size) and higher absolute levels of FoxP2 in the MMSt than young adults, we find similarly persistent downregulation of FoxP2 and equivalent vocal plasticity and vocal convergence in the two age cohorts. No relationship between individual variation in vocal learning measures and FoxP2 expression was detected.ConclusionsWe find neural evidence to support persistent vocal learning in the budgerigar, suggesting resilience to aging in the open-ended learning program of this species. The lack of a significant relationship between FoxP2 expression and individual variability in vocal learning performance suggests that other neurogenetic mechanisms could also regulate this complex behavior.

Acquiring Social Safety Engages Oxytocin Neurons in the Supraoptic Nucleus: Role of Magel2 Deficiency

Introduction: Exposure to social trauma may alter engagement with both fear-related and unrelated social stimuli long after. Intriguingly, how simultaneous discrimination of social fear and safety is affected in neurodevelopmental conditions remains underexplored. The role of the neuropeptide oxytocin is established in social behaviors and yet unexplored during such a challenge post-social trauma. Methods: Using Magel2 knockout mice, an animal model of Prader-Willi syndrome (PWS) and Schaaf-Yang syndrome (SYS), we tested memory of social fear and safety after a modified social fear conditioning task. Additionally, we tracked the activity of oxytocin neurons in the supraoptic (SON) and paraventricular (PVN) nuclei of the hypothalamus by fiber photometry, as animals were simultaneously presented with a choice between fear and safe social cue during recall. Results: Male Magel2 KO mice trained to fear females with electrical footshocks avoided both unfamiliar females and males during recalls, lasting even a week post-conditioning. On the contrary, trained Magel2 WT avoided only females during recalls, lasting days rather than a week post-conditioning. Inability to overcome social fear and avoidance of social safety in Magel2 KO mice were associated with the reduced engagement of oxytocin neurons in the SON but not the PVN. Conclusion: In a preclinical model of PWS/SYS, we demonstrated region-specific deficit in oxytocin neuron activity associated with behavioral generalization of social fear to social safety. Insights from this study add to our understanding of oxytocin action in the brain at the intersection of social trauma and PWS/SYS.

High-resolution ethograms, accelerometer recordings, and behavioral time series of Japanese quail

Although many small vertebrates are capable of performing high-speed behaviors, most studies continue to focus on low-resolution temporal scales (>>1 s). Herein, we present video-recordings, behavior time series, and the computer software for video-analysis of Japanese quail within social groups. Home-boxes were monitored using both top and side video-cameras. High-resolution ethograms were developed for analyses. Pairs of females were assigned as either controls or using one of two methods for attachment of an accelerometer (patch or backpack). Behavior was recorded during 1 h on the first 2-days, sampled at 1 s intervals (days 1 and 2). On day 8, an unfamiliar male was placed in the home-box and its behavior was recorded during the first 10 min, sampled every 1/15 s. Male accelerometer recordings were also obtained. Video-recordings and resulting detailed high-resolution behavioral time series are valuable for reuse in comparative studies regarding the temporal dynamics of behavior within social environments. In addition, they are necessary for the assessment of novel machine learning algorithms that could be used for deciphering the output of accelerometer recordings.

Learning to identify talkers: Do 4.5-month-old infants distinguish between unfamiliar males?

Vocal recognition of socially relevant conspecifics is an important skill throughout the animal kingdom. Human infants recognize their own mother at birth, and they distinguish between unfamiliar female talkers by 4.5 months of age. Can 4.5-month-olds also distinguish between unfamiliar male talkers? To date, no adequately powered study has addressed this question. Here, a visual fixation procedure demonstrates that, unlike adults, 4.5-month-olds (N = 48) are worse at telling apart unfamiliar male voices than they are at telling apart unfamiliar female voices. This result holds despite infants' equal attentiveness to unfamiliar male and female voices.

Evidence for maintenance of key components of vocal learning in ageing budgerigars despite diminished affiliative social interaction.

In some species, the ability to acquire new vocalizations persists into adulthood and may be an important mediator of social interactions. While it is generally assumed that vocal learning persists undiminished throughout the lifespan of these open-ended learners, the stability of this trait remains largely unexplored. We hypothesize that vocal learning exhibits senescence, as is typical of complex cognitive traits, and that this decline relates to age-dependent changes in social behaviour. The budgerigar (Melopsittacus undulatus), an open-ended learner that develops new contact call types that are shared with social associates upon joining new flocks, provides a robust assay for measuring the effects of ageing on vocal learning ability. We formed captive flocks of 4 previously unfamiliar adult males of the same age class, either 'young adults' (6 mo-1 y) or 'older adults' (≥ 3 y), and concurrently tracked changes in contact call structure and social interactions over time. Older adults exhibited decreased vocal diversity, which may be related to sparser and weaker affiliative bonds observed in older adults. Older adults, however, displayed equivalent levels of vocal plasticity and vocal convergence compared to young adults, suggesting that many components of vocal learning are largely maintained into later adulthood in an open-ended learner.

Oxytocin receptor antagonism during early vocal learning reduces song preference and imitation in zebra finches

In species with vocal learning, acquiring species-typical vocalizations relies on early social orienting. In songbirds, for example, learning song requires dynamic social interactions with a “tutor” during an early sensitive period. Here, we hypothesized that the attentional and motivational processes that support song learning recruit the oxytocin system, which is well-understood to play a role in social orienting in other species. Juvenile male zebra finches naïve to song were each tutored by two unfamiliar adult males. Before exposure to one tutor, juveniles were injected subcutaneously with oxytocin receptor antagonist (OTA; ornithine vasotocin) and before exposure to the other, saline (control). Treatment with OTA reduced behaviors associated with approach and attention during tutoring sessions. Using a novel operant paradigm to measure preference while balancing exposure to the two tutor songs, we showed that the juveniles preferred to hear the song of the control tutor. Their adult songs more closely resembled the control tutor’s song, and the magnitude of this difference was predicted by early preference for control over OTA song. Overall, oxytocin antagonism during exposure to a tutor seemed to bias juveniles against that tutor and his song. Our results suggest that oxytocin receptors are important for socially-guided vocal learning.

Olfatory HLA-associated mechanism of formation of married couples in the development of congenital heart diseases in children

Taking into account the significance of the HLA complex in the inflammatory and immune responses, we can assume that the potential for limiting or developing pathology in the next generation will be determined at the stage of selection of certain alleles in the spousal genotype.The aim. To study the role of HLA assortativity in couples with healthy children and couples with children with congenital heart diseases (CHD) through the prism of immunogenetic mechanisms of mutual olfactory choice.Materials and methods. We studied the distribution of HLA-DRB1 alleles in married couples with healthy children and with children having CHD. To identify the associations of HLA-DRB1 alleles with odor preferences, we also studied the group included young males and females. HLA-DRB1 gene typing was carried out in all participants.Results. The combination of HLA-DRB1 alleles in couples with healthy children was similar to the combination of these alleles in the mutual olfactory sympathy between unfamiliar young males and females. Allele combinations in the spouses from the experimental group differ from the group of random selection. The frequency of matches for HLA-DRB1 alleles in married couples with children having CHD without was significantly higher than in the control group.Conclusion. The first stage of selection, associated with olfactory selection, is aimed to the whole population, and it is significantly manifested in the control group (married couples with healthy children). At the same time, in the experimental group (couples with children having CHD), some deviations from the main selection were discovered. Generally, specific HLA-DRB1 allele combinations obtained on the basis of olfactory assessments, indicate the involvement of HLA molecules in pheromone reception.

Locus Coeruleus-Noradrenergic Neurons Regulate Stress Coping During Subchronic Exposure to Social Threats: A Characteristic Feature in Postpartum Female Mice.

Stress-coping strategies have been implicated in depression. The control of stress coping may improve the symptom and higher prevalence of depression during the postpartum period in women. However, the neuronal mechanisms underlying stress coping remain to be fully elucidated in postpartum women. In this study, we examined how locus coeruleus-noradrenergic (LC-NA) neurons, which have been associated with both stress coping and depression, regulate changes in coping style induced by subchronic exposure to unfamiliar male mice as a social threat in postpartum female mice. In contrast to virgin females, dams exposed to unfamiliar males daily for four consecutive days showed reduced immobility duration in the forced swim test, indicating that exposure to unfamiliar males decreased passive stress coping in dams. Exposure to unfamiliar males also decreased sucrose palatability in the sucrose preference test and suppressed the crouching behavior in the maternal care test but did not affect anxiety-like behavior in the hole-board test in dams. In fiber photometry analyses, LC-NA neurons showed differential activity between dams and virgin females in response to unfamiliar males. Chemogenetic inhibition of LC-NA neurons during exposure to unfamiliar males prevented the social threat-induced decrease in immobility duration in the forced swim test in dams. Furthermore, inhibition or activation of LC-NA neurons exacerbated crouching behavior in dams. These results indicate that LC-NA neurons regulate the social threat-induced decrease in passive stress coping and relieve social threat-induced inhibition of maternal care in postpartum female mice.

Social impact of mara pair disruption on the formation of new bonds and reproduction in a multiple mate choice context

Maras, Dolichotis patagonum , combine social monogamy and plural breeding, an unusual mating system for mammals. We tested how maras adapt to the forced separation of pair-bonded partners and how the potential new mates perform over the breeding season and during the process of forming new pairs. Fourteen established pairs from a captive population were randomly assigned to a control (C-group; N = 7) or an experimental (E-group; N = 7) condition. The experiment consisted of replacing seven paired males with seven socially unfamiliar males (new potential mates). Individual behaviour and social interactions were recorded over a 6-month period (spring–summer; i.e. 14 sessions) from 0800 to 1800 hours, totalling 11 hourly sampling points per session. We measured pair behaviours and degree of general behavioural synchrony over sessions 1–7 (early) and over sessions 8–14 (late). We also measured how social disruption affected the social networking of individuals forming new pair bonds as compared to individuals with established mates. We furthermore assessed the level of activity of females exposed to mate switching and the production of offspring over the breeding season. In the E-group, maras showed a reduction in pair behaviours and synchronization of activities. There were also multiple interactions among females with several males, revealing initial mate choice activity during the early time period. The period of mate choice was characterized by instability in social networking and changes in the strength of a pair's fidelity. Although the E-group included five newly established pairs, offspring production was similar to that of the C-group. Our findings show that after presumably stressful experimental social disruption, most maras re-paired in captivity, although with some delay in offspring production, suggesting that this species has the plasticity to cope with male partner loss under semicontrolled environmental conditions. However, the strength of monogamous bonds was affected by this social disruption. • Pair-bonding disruption affected the behaviour of maras, D. patagonum. • Female and male interactions during mate choice caused social instability. • Most female maras were able to re-pair after the loss of their male partner. • Offspring were unaffected by social disruption during the breeding season. • Monogamy level of male–female pairs was affected by social disruption.

The impacts of management interventions on the sociality of African lions (Panthera leo): Implications for lion conservation

Abstract African lion (Panthera leo) populations normally consist of several neighbouring prides and multiple adult males or groups of males that interact competitively. In large, open systems, cub defence from infanticidal males and territory defence drive group living in lions. However, in smaller (<1000 km2), fenced wildlife reserves, opportunities for natural immigration and emigration are limited which means that the evolutionary drivers of lion sociality may collapse. Here, we use lion behavioural data collected from 16 wildlife reserves across South Africa to test how management‐induced ecological conditions alter lion social dynamics. The number of lionesses observed together was best predicted by pride size, prey biomass and biome. Lionesses were less likely to group together as pride size increased, but more likely to group together as prey biomass and habitat productivity increased. In addition, adult males were observed more frequently with prides that had young (<12 months) cubs in reserves that had unfamiliar adult males present compared to reserves without any unfamiliar adult males. Our results demonstrate how intraspecific competition between lions drives their sociality, and this may break down in small, fenced wildlife reserves where lions are actively managed. Although small, fenced reserves in South Africa have made a significant contribution to increasing lion numbers on the continent, our work highlights several important ecological implications of active lion management. For wildlife managers, mimicking the outcomes of different levels of intraspecific competition is likely a critical management tool for the persistence of lions in small reserves.

From Mating to Milk Access: A Review of Reproductive Vocal Communication in Mice

Vocalisations play a central role in rodent communication, especially in reproduction related behaviours. In adult mice (Mus musculus) the emission of ultrasonic vocalisations (USVs) has been observed in courtship and mating behaviour, especially by males. These have been found to have distinctive individual signatures that influence female choice of mating partner. The most recent findings show that vocal communication also has a role in parental cooperation, in that female mice communicate with male partners in ultrasonic frequencies to induce paternal behaviour. Infant vocalisations form the other important part of reproductive vocal communication. Although born deaf, neonatal mice are capable of producing vocalisations since birth. As an altricial species, successful mother-infant communication is essential for survival, and these vocalisations are important modulators of maternal behaviour. Three main types of infant vocalisations have been identified and characterised. Most research has addressed pure USVs, related to stressful situations (e.g., cold, isolation, handling, presence of unfamiliar males or predators), which usually elicit maternal search and retrieval. In addition, broad-band spectrum signals, emitted post-partum during cleaning of foetal membranes, inhibit biting and injury by adults and “wriggling calls,” emitted during suckling, release maternal behaviour (such as licking). Several variables have been identified to modulate vocalisations in mice, including individual characteristics such as strain/genotype, age, sex, and experimental factors such as pharmacological compounds and social context. In recent years, there has been a big increase in the knowledge about the characteristics of vocal communication in rodents due to recent technological advances as well as a growing interest from the neuroscience community. Vocalisation analysis has become an essential tool for phenotyping and evaluating emotional states. In this review, we will (i) provide a comprehensive summary of the current knowledge on mouse reproductive vocal communication and (ii) discuss the most recent findings in order to provide a broad overview on this topic.

Blocking olfactory input alters aggression in male and female California mice (Peromyscus californicus).

Olfactory input into the brain can be disrupted by a variety of environmental factors, including exposure to pathogens or environmental contaminants. Olfactory cues are often eliminated in laboratory rats and mice through highly invasive procedures like olfactory bulbectomy, which may also disrupt accessory olfactory pathways and detection of non-volatile odors. In the present study, we tested whether inducing anosmia through intranasal infusion of zinc gluconate alters aggression in a monogamous, biparental rodent species, the California mouse (Peromyscus californicus). This less invasive method of manipulating olfaction selectively targets the olfactory epithelium and reduces the detection of volatile odors. Treatment with zinc gluconate extended the time required for male and female California mice to find hidden pieces of apple and reduced the amount of time spent investigating bedding that was soiled by unfamiliar males. Moreover, inhibition of olfaction with zinc gluconate reduced aggressiveness in both sexes as demonstrated by an increased attack latency in the resident-intruder test among same-sex dyads from the same treatment group. These results suggest that volatile olfactory cues are necessary for agonistic responses in both male and female California mice. Therefore, even in species with complex social systems that include territorial aggression and monogamy, volatile olfactory cues modulate agonistic behavior.

Responses of a pair‐living, sexually monogamous primate to the simulated presence of solitary individuals: A field playback experiment

AbstractLoud calls play an important function in regulating the use of space and structuring social groups and mating systems in a wide range of taxa. In pair‐living territorial animals, where encounters with neighbors and solitary conspecifics are common, these calls are mainly associated with resource defense or mate guarding behaviors. Owl monkeys (Aotus azarae) live in groups of one pair of reproducing adults and 1–4 younger, non‐reproducing individuals. Both sexes disperse when they are around 3 years of age; they become solitary floaters who compete to replace same‐sex adults from other groups. Here, we examined the behavioral responses of Azara's owl monkey pairs toward calls of unpaired and unfamiliar males and females to better understand if the competition between floaters and groups is in relationship to the defense of their territory, their mates, or both. We collected behavioral data from six groups, before, during, and after the playing back of unfamiliar male and female loud calls and of a control stimulus at the center and border of their home ranges. Overall, our results showed that the playback location did not elicit differential responses in the monkeys and that both sexes were more reactive to male than female unfamiliar calls, as evidenced by higher rates of sociosexual and vocal responses, movement toward the playback, and intergroup encounters during and after the experiments. Our study indicates that paired male and female owl monkeys mainly defend their partners toward intruders and emphasizes the need of including the role of sexual competition on both sexes in models about the evolution of pair‐living social organizations and sexual monogamy mating systems.

Odour-based social recognition in Damaraland mole-rats, Fukomys damarensis

The ability to discriminate between conspecifics functions in mate choice, kin-selected cooperation and territory defence. In mammals, olfaction plays a key role in such social interactions. Olfactory cues may be particularly important for subterranean mammals, for which visual and acoustic cues are less effective. Damaraland mole-rats live in groups comprising a breeding pair and their nonbreeding offspring. They are xenophobic, obligate outbreeders and independent dispersal represents the usual route to reproduction for both sexes. As yet, little is known about how dispersing individuals locate mates. Using a series of behavioural experiments, we reveal that mole-rats can discriminate between unfamiliar breeding groups and solitary, nonbreeders of the opposite sex by using odour cues. Our experiments showed that subjects spent more time investigating sand taken from other mole-rat groups than control sand, indicating an ability to recognize substrate-borne conspecific odours. Mole-rats also spent more time digging and sweeping in sand taken from the tunnels of unfamiliar, solitary animals of the opposite sex than sand taken from unfamiliar breeding groups and removed a higher volume of this sand during the experiments. Together, these results suggest an olfactory preference in both sexes for solitary, opposite-sex animals over breeding groups. Our results are supported by observations from the field that immigration into breeding groups is rare, with dispersing females typically establishing new groups, where they are subsequently joined by unfamiliar males. This study supports olfaction as a potential recognition cue which may facilitate adaptive dispersal. • Damaraland mole-rats recognize conspecifics using substrate-borne odour cues. • Both sexes dig the most in sand from the tunnels of unfamiliar, opposite-sex mole-rats. • Digging effort is reduced in sand taken from the tunnels of other breeding groups. • A primary role for olfaction in social recognition is supported in this species.

A behavioral logic underlying aggression in an African cichlid fish

AbstractSocial rank in a hierarchy determines which individuals have access to important resources such as food, shelter, and mates. In the African cichlid fish Astatotilapia burtoni, rank is under social control, such that larger males are more likely than smaller males to be dominant in rank. Although it is well known that the relative size of A. burtoni males is critical in controlling social rank, the specific behaviors underlying responses to males of different sizes are not well understood. In many other fish species, when size asymmetries between competing males are small, physical aggression is likely to be used to settle territorial disputes. Our goal was to characterize these responses in male A. burtoni by performing resident‐intruder assays, in which aggressive behaviors were measured in territorial males in response to the introduction of unfamiliar males that differed in relative standard length (SL). We found that the relative SL of intruders played an important role in determining behavioral performance. Resident males that were smaller than the intruder (resident >5% smaller in SL) or matched (resident between 0 and 5% smaller or larger in SL) in size to the intruder performed more lateral displays, a type of non‐physical aggression, than resident males that were larger than the intruder (resident >5% larger in SL). However, physical aggression, such as chases and bites, did not differ as a function of relative SL. Thus, contrary to what was expected based on work in other species, our results demonstrate that dominant resident A. burtoni increase non‐physical aggression to settle territorial disputes when non‐dominant intruders are closer in size. This behavioral strategy may aid in readily settling conflicts when size asymmetries are small.

Influence of female coalitionary aggressive behavior on the success of male introductions to female groups of rhesus macaques (Macaca Mulatta)

Migration patterns of wild rhesus macaque males are often mimicked in captivity by introducing unfamiliar males to female groups every few years. This strategy prevents inbreeding and has been shown to encourage group stability once males are fully integrated. The current study focused on female coalitionary aggressive behavior directed toward males during introductions to describe factors that predict its frequency and any relationship with introduction success. Observational data (755 h) were collected during eight introductions of male cohorts (3–7 individuals) to established female groups (14–39 breeding-age females). Female coalitionary aggression (FCA), defined as four or more females simultaneously attacking an individual male, was recorded 114 times and occurred during all introductions. Data showed that male groups with alpha males who aggressed females during the coalitionary events were more likely to be successfully integrated than those with alpha males who did not retaliate against females. Stepwise multiple regression analyses of individual females (N = 183) revealed that females from larger groups and older females were more likely to be involved in coalitionary aggression, while rank, family size and number of matrilines in the group did not play a role. A rating system of the severity of FCA events revealed male groups receiving more severe FCA were less likely to be successfully introduced, and larger male groups received more severe FCA than did smaller groups of males. Based on these data, it is recommended that colony managers expect FCA to occur during introductions, especially with older females and larger groups. Colony managers should monitor the alpha male’s response to FCA, as well as the severity of the FCA since those factors may predict introduction success.

Offspring and adult chemosensory recognition by an amphisbaenian reptile may allow maintaining familiar links in the fossorial environment.

Kin recognition is a phenomenon with an important function in maintaining cohesive social groups in animals. Several studies have examined parent–offspring recognition in species with direct parental care. Few studies have, however, explored parent–offspring recognition in animals that, at best, only show apparent indirect parental care, such as some reptiles. In this study, we investigated reciprocal parent–offspring recognition in the fossorial amphisbaenian Trogonophis wiegmanni, a viviparous species that shows potential stable ‘family groups’ in the form of parent-offspring long-term associations. We examined whether adult males and females could discriminate via chemical cues between familiar juveniles which associate with them within their family groups, and are potentially their offspring, to that of unfamiliar juveniles, and whether juveniles could discriminate between familiar adult males and females of their family group (probably their parents) and unfamiliar unrelated adults. We measured tongue flick behavior to study chemosensory responses to the scent of conspecifics. We found that adult female amphisbaenians, but not males, could discriminate between scents of familiar and unfamiliar juveniles. Juvenile amphisbaenians did not discriminate between familiar and unfamiliar adult females, but recognize familiar from unfamiliar males. We discuss our results of parent–offspring recognition according to its potential social function in an ecological fossorial context where visibility is limited and chemosensory kin recognition may contribute to the establishment of stable family groups.

Effect of infant pelage colour on infant caring by other group members: a case study of wild Javan lutungs (Trachypithecus auratus)

Abstract We observed interactions of group members with seven Javan lutungs (Trachypithecus auratus) infants from January to March 2018. Infants’ pelage colouration changed from bright yellow to black, and it took about 2.9 months (on average) until the yellowness disappeared, and about 6.1 months (on average) until the colouration change was completed. Infants with yellow pelage spent more time being held and screaming, while infants with black pelage spent more time moving and feeding. The number of neighbouring animals decreased as the infants’ pelage became black, which implied that group members are attracted to the yellowness of infants. As the pelage became black and the infant aged, the neighbouring animals exhibited more social behaviour. Our results implied that bright yellow pelage colour triggers their parental instincts. The bright pelage colour would benefit infants because group members protect them from unfamiliar males and predators.

Особенности социального поведения мышей после длительного действия психоэмоционального и инфекционного факторов

The behavior of male mice of the inbred C57B/6 strain was investigated after prolonged exposure to two factors ‒ social stress and helminth infection, the combination of which is often observed in humans. Four experimental groups of mice were compared: 1) with a long-lasting experience of social defeats in intermale confrontations (30 days) (SS); 2) infected with O. felineus helminths (6 months) (OF); 3) exposed to both factors (SS + OF); 4) intact mice without influence of any factors (CON). The behavior of all animals was assessed in the open field test with a box placed in it, which was empty for the first 3 min of the test and kept an unfamiliar male of the inbred BALB/c strain for the second 3 min. Social stress had a more pronounced effect on the assessed behavioral parameters of mice in this test than infection. Mice SS were the most active in exploring of the box with an unfamiliar male inside than other animals: they climbed on it much more often and had a longer average time spent near the box. In addition, they had increased exploratory (number of wall rearings) and grooming (the number and duration) activities. Behavior of infected OF mice did not differ from CON one in both the first and the second 3 min of the test. In mice with a combined effect of factors (SS + OF), non-social forms of behavior also did not differ from the control indices, and the reaction to an unfamiliar male in the box was weaker than in mice SS. It was concluded that long-lasting experience of social defeats in intermale confrontations has a more pronounced effect on the social and non-social behavior in mice, compared with chronic infection of animals with O. felineus helminths. Moreover, the combination of two influencing factors promotes to the decreasing of social interest in mice.

Differential effects of progesterone on social recognition and the avoidance of pathogen threat by female mice

Although pathogen threat affects social and sexual responses across species, relatively little is known about the underlying neuroendocrine mechanisms. Progesterone has been speculated to be involved in the mediation of pathogen disgust in women, though with mixed experimental support. Here we considered the effects of acute progesterone on the disgust-like avoidance responses of female mice to pathogen threat. Estrous female mice discriminated and avoided the urinary and associated odors of males subclinically infected with the murine nematode parasite, Heligmosomoides polygyrus. These avoidance responses were not significantly affected by pre-treatment with progesterone. Likewise, brief (1 min) exposure to the odors of infected males attenuated the subsequent responses of females to the odors of the normally preferred unfamiliar males and enhanced their preferences for familiar males. Neither progesterone nor allopregnanolone, a central neurosteroid metabolite of progesterone, had any significant effects on the avoidance of unfamiliar males elicited by pre-exposure to a parasitized male. Progesterone and allopregnanolone, did, however, significantly attenuate the typical preferences of estrous females for unfamiliar uninfected males, suggestive of effects on social recognition. These findings with mice indicate that progesterone may have minimal effects on the responses to specific parasite threat and the expression of pathogen disgust but may influence more general social recognition and preferences.