Early-life diet composition affects phenotypic variation of correlated animal personality traits.

Behavioural traits are under both genetic and environmental influence during early life stages. Early environmental conditions related to the amount and type of food have been found to alter behaviour in many organisms. However, how early life diet affects the variation in and the correlation between behavioural traits is largely unknown. Using a multivariate approach, we investigated how variation in parental prey selection is related to three repeatable nestling personality traits, and explored the within and between-individual covariation between these behaviours in a wild passerine, the great tit (Parus major). Our results confirm that breath rate, docility and handling aggression (HA) in great tit nestlings are repeatable traits. Contrary to our expectation, the three nestling personality traits did not form a behavioural 'syndrome' on the phenotypic level in the study population, but we found two of three expected phenotypic correlations, mostly at the within-individual level. Moreover, we found that breath rate significantly decreased with a higher number of spiders in the diet, and docility and handling aggression were significantly and inversely related to higher numbers of noctuids and tortricids in the diets of individuals within broods. Thus, our findings suggest that provisioning quantity and quality during the early life, affects variation in behavioural phenotypes, which occurs mainly at the within-individual level.

The scent of offspring: chemical profiles of larvae change during development and affect parental behavior in a burying beetle.

Chemical cues and signals, especially in insects, play a pivotal role in mediating interactions between individuals. Past studies have largely focused on adult semiochemicals and have neglected those of juvenile stages. Especially in the context of parental care, the larval odor might have a profound impact on parenting behavior, guiding parents in how much resources they should allocate to the different developmental stages. However, whether ontogenetic changes occur in subsocial species and whether larval-emitted scents influence parent-offspring interactions is largely unknown. Using 3 different sampling techniques, we analyzed the cuticular and VOC profile of the 3 larval instars of the burying beetle Nicrophorus vespilloides, which is known for its elaborate parental care. We found distinct differences in the cuticular and VOC profiles across the 3 larval stages. Second-instar larvae, which receive more frequent feedings from parents than the other larval stages, released greater amounts of acetophenone, methyl geranate, and octanoic acid isopropyl ester than the first and third instar. Additionally, using a newly developed bioassay with automated video tracking, we found that adding the odor of second-instar larvae to first-instar larvae increased the number of maternal feeding trips. Our results suggest that the odor produced by larvae plays an important role in mediating parent-offspring interactions. Given these findings, burying beetles might emerge as a promising candidate for identifying a potential begging pheromone.

Effect of melatonin supplementation upon parental care and nestling growth in arctic-breeding songbirds.

Arctic-breeding birds exhibit around-the-clock activity, and these activity cycles are postulated to maximize reproductive success during the short breeding season characteristic of high-latitude regions. Two closely related species of arctic-breeding songbirds, Lapland longspurs (Calcarius lapponicus; ground-nesting) and snow buntings (Plectrophenax nivalis; cavity-nesting) exhibit extended activity cycles throughout the polar day (71° N) except for 4-5 h of daily quiescence. Ground-nesting Lapland longspurs experience higher levels of nest predation than cavity-nesting snow buntings, and this difference is reflected in elevated nest vigilance in male longspurs compared with snow buntings. In this study, we examined the effect of melatonin supplementation upon male parental care, corresponding measures of nestling growth, and ability to reduce activity (and increase sleep). A pharmacological dose of melatonin in captive snow buntings dampened the amplitude of activity rhythms over the polar day with no detectable phase-shifting compared with control-implanted birds. Melatonin treatment reduced nest visits and overall time spent on the nest by male snow buntings compared with controls. There was no significant increase in time spent by female snow buntings on the nest to compensate for this, and there was no significant effect on offspring growth rates. There were no effects of melatonin supplementation on longspur adults or offspring, suggesting behavioral insensitivity to exogenous melatonin treatment. These differences in sensitivity underscore the importance of nest defense in ground-nesting longspurs compared with cavity-nesting snow buntings, which participate minimally in nest defense.

A pheromone receptor in cichlid fish mediates attraction to females but inhibits male parental care.

Reproductive behaviors differ across species, but the mechanisms that control variation in mating and parental care systems remain unclear. In many animal species, pheromones guide mating and parental care. However, it is not well understood how vertebrate pheromone signaling evolution can lead to new reproductive behavior strategies. In fishes, prostaglandin F2α (PGF2α) drives mating and reproductive pheromone signaling in fertile females, but this pheromonal activity appears restricted to specific lineages, and it remains unknown how a female fertility pheromone is sensed for most fish species. Here, we utilize single-cell transcriptomics and CRISPR gene editing in a cichlid fish model to identify and test the roles of key genes involved in olfactory sensing of reproductive cues. We find that a pheromone receptor, Or113a, detects fertile cichlid females and thereby promotes male attraction and mating behavior, sensing a ligand other than PGF2α. Furthermore, while cichlid fishes exhibit extensive parental care, for most species, care is provided solely by females. We find that males initiate mouthbrooding parental care if they have disrupted signaling in ciliated sensory neurons due to cnga2b mutation or if or113a is inactivated. Together, these results show that distinct mechanisms of pheromonal signaling drive reproductive behaviors across taxa. Additionally, these findings indicate that a single pheromone receptor has gained a novel role in behavior regulation, driving avoidance of paternal care among haplochromine cichlid fishes. Lastly, a sexually dimorphic, evolutionarily derived parental behavior is controlled by central circuits present in both sexes, while olfactory signals gate this behavior in a sex-specific manner.

Sexual selection and life history interact to influence the evolution of paternal care.

Parental care is essential to offspring survival in many species. Understanding why males of some species provide care, whereas others do not, has received substantial attention. Previous research has found that sexual selection can favor paternal care, yet we still do not fully understand why sexual selection favors male care in some species but not others. It is also unclear when paternal care versus other preferred male trait(s) will be favored by sexual selection. We hypothesize that sexual selection can interact with basic life history to influence the conditions under which paternal care and/or another preferred male trait will be favored by sexual selection. We used a mathematical approach in which males alone provide parental care and exhibit a non-care trait that is preferred in mate choice. Using this approach, we demonstrate that life-history characteristics (stage-specific mortality, fertilization success, gamete numbers) can interact with sexual selection to influence the evolution of paternal care and/or a preferred non-care trait. In particular, whether (1) adult mortality, egg mortality, and fertilization success are high versus low and (2) a tradeoff exists between paternal care and a non-care preferred trait will influence whether selection most strongly favors additional paternal care or a non-care preferred trait. In general, we would expect strong selection for more male care when it is preferred in mate choice. In some cases, mate preferences for paternal care can inhibit selection for a preferred non-care trait. Mate preferences for paternal care can also broaden the life-history conditions under which we would expect the elaboration of male care to occur.

Revisiting the ecology and evolution of burying beetle behavior (Staphylinidae: Silphinae).

Investigating fundamental processes in biology requires the ability to ground broad questions in species-specific natural history. This is particularly true in the study of behavior because an organism's experience of the environment will influence the expression of behavior and the opportunity for selection. Here, we provide a review of the natural history and behavior of burying beetles of the genus Nicrophorus to provide the groundwork for comparative work that showcases their remarkable behavioral and ecological diversity. Burying beetles have long fascinated scientists because of their well-developed parenting behavior, exhibiting extended post-hatching care of offspring that varies extensively within and across taxa. Despite the burgeoning success of burying beetles as a model system for the study of behavioral evolution, there has not been a review of their behavior, ecology, and evolution in over 25 years. To address this gap, we leverage a developing community of researchers who have contributed to a detailed knowledge of burying beetles to highlight the utility of Nicrophorus for investigating the causes and consequences of social and behavioral evolution.

A novel quadrant spatial assay reveals environmental preference in mouse spontaneous and parental behaviors.

Environmental factors have well-documented impacts on brain development and mental health. Therefore, it is crucial to employ a reliable assay system to assess the spatial preference of model animals. In this study, we introduced an unbiased quadrant chamber assay system and discovered that parental pup-gathering behavior takes place in a very efficient manner. Furthermore, we found that test mice exhibited preferences for specific environments in both spontaneous and parental pup-gathering behavior contexts. Notably, the spatial preferences of autism spectrum disorder model animals were initially suppressed but later equalized during the spontaneous behavior assay, accompanied by increased time spent in the preferred chamber. In conclusion, our novel quadrant chamber assay system provides an ideal platform for investigating the spatial preference of mice, offering potential applications in studying environmental impacts and exploring neurodevelopmental and psychiatric disorder models.

Parental care and overprotection predict worry and anxiety symptoms in emerging adult students.

Anxiety disorders represent a prevalent mental health concern, with escalating rates, especially among emerging adults. University students, in particular, face a myriad of academic and life stressors that can amplify feelings of worry and anxiety. While early parental bonding seem to predict anxiety disorders later in life, the applicability to emerging adult students and its applicability to predict sub-clinical and transdiagnostic anxiety features remain unclear. This study aims to examine i) the relationship between demographic variables and key features of anxiety disorders (i.e., worry and anxiety symptoms); and ii) the predictive association between early parental bonding and anxiety-related features. A sample of 370 university students in Italy (n = 279 females; M age = 20.84 years, SD age = 1.81 years) completed the Parental Bonding Instrument, the Penn State Worry Questionnaire, and the Beck Anxiety Inventory. Females reported higher levels of worry and anxiety compared to males. Significantly higher worry and anxiety symptoms were reported by individuals who experienced affectionless control (low care and high overprotection) as compared to those exposed to optimal parenting (high care and low overprotection). Predictive models indicated that scores of parental care (i.e., the principal component between maternal and paternal care scores) and parental overprotection (i.e., the principal component between maternal and paternal overprotection scores) are robust predictors of worry and anxiety symptoms. However, this relationship showed a gender-specific pattern: lower parental care was more significant in predicting anxiety features in males, while high overprotection was more significant in females. The findings contribute to the comprehension of the risk factors influencing the susceptibility of emerging adult students to anxiety disorders.

Prolactin modulates changes in parental care behaviour in response to perceived paternity in bluegill sunfish (Lepomis macrochirus).

Prolactin is a hormone conserved across all vertebrates and is renowned for its role in reproduction and parental care. Previous studies on prolactin in fish have primarily relied on administration of mammalian prolactin and have suggested that increases in prolactin lead to greater parental care. However, the influence of endogenous prolactin on fish parental care remains unknown. Here, we measure circulating concentrations of endogenous prolactin during parental care in a fish and link these concentrations to parental care behaviour. We provide evidence that male bluegill sunfish with higher circulating concentrations of prolactin provide more parental care to their offspring. Furthermore, we show that nesting males with experimentally reduced perceived paternity have lower circulating prolactin concentrations and perform fewer parental behaviours, facilitating an adaptive investment in offspring in response to paternity cues. Our findings not only confirm the role of endogenous prolactin in modulating parental care behaviour in a fish but also provide a mechanism underlying the adaptive changes in parental care made in response to perceived paternity.

Female alternative reproductive tactics: diversity and drivers.

It is often argued that anisogamy causes alternative reproductive tactics (ARTs) to be more common in males than females. We challenge this view by pointing out logical flaws in the argument. We then review recent work on the diversity of female ARTs, listing several understudied types such as solitary versus communal breeding and facultative parthenogenesis. We highlight an important difference between male and female ARTs that caused female ARTs to be overlooked: male ARTs tend to focus on successful fertilization, whereas female ARTs occur at many stages of reproduction and often form complex networks of decision points. We propose to study correlated female ARTs as a whole to better understand their drivers and eco-evolutionary dynamics.

Odor cues rather than personality affect tadpole deposition in a neotropical poison frog.

Animals constantly need to evaluate available external and internal information to make appropriate decisions. Identifying, assessing, and acting on relevant cues in contexts such as mate choice, intra-sexual competition, and parental care is particularly important for optimizing individual reproductive success. Several factors can influence decision-making, such as external environmental cues and the animal's own internal state, yet, we have limited knowledge on how animals integrate available information. Here, we used an entire island population (57 males, 53 females, and 1,109 tadpoles) of the neotropical brilliant-thighed poison frog Allobates femoralis to investigate how 2 factors (olfactory cues and personality traits) influence the ability of males to find and use new resources for tadpole deposition. We experimentally manipulated the location of tadpole deposition sites and their associated olfactory cues, and repeatedly measured exploration and boldness in adult males. We further reconstructed tadpole deposition choices via inferred parent-offspring relationships of adult frogs and tadpoles deposited in our experimental pools using molecular parentage analysis. We found that the discovery and use of new rearing sites were heavily influenced by olfactory cues; however, we did not find an effect of the measured behavioral traits on resource discovery and use. We conclude that in highly dynamic environments such as tropical rainforests, reliable external cues likely take priority over personality traits, helping individuals to discover and make use of reproductive resources.

Odor cues rather than personality affect tadpole deposition in a neotropical poison frog.

Animals constantly need to evaluate available external and internal information to make appropriate decisions. Identifying, assessing, and acting on relevant cues in contexts such as mate choice, intra-sexual competition, and parental care is particularly important for optimizing individual reproductive success. Several factors can influence decision-making, such as external environmental cues and the animal's own internal state, yet, we have limited knowledge on how animals integrate available information. Here, we used an entire island population (57 males, 53 females, and 1,109 tadpoles) of the neotropical brilliant-thighed poison frog Allobates femoralis to investigate how 2 factors (olfactory cues and personality traits) influence the ability of males to find and use new resources for tadpole deposition. We experimentally manipulated the location of tadpole deposition sites and their associated olfactory cues, and repeatedly measured exploration and boldness in adult males. We further reconstructed tadpole deposition choices via inferred parent-offspring relationships of adult frogs and tadpoles deposited in our experimental pools using molecular parentage analysis. We found that the discovery and use of new rearing sites were heavily influenced by olfactory cues; however, we did not find an effect of the measured behavioral traits on resource discovery and use. We conclude that in highly dynamic environments such as tropical rainforests, reliable external cues likely take priority over personality traits, helping individuals to discover and make use of reproductive resources.

Improved Chinese Giant Salamander Parental Care Behavior Detection Based on YOLOv8.

Optimizing the breeding techniques and increasing the hatching rate of Andrias davidianus offspring necessitates a thorough understanding of its parental care behaviors. However, A. davidianus' nocturnal and cave-dwelling tendencies pose significant challenges for direct observation. To address this problem, this study constructed a dataset for the parental care behavior of A. davidianus, applied the target detection method to this behavior for the first time, and proposed a detection model for A. davidianus' parental care behavior based on the YOLOv8s algorithm. Firstly, a multi-scale feature fusion convolution (MSConv) is proposed and combined with a C2f module, which significantly enhances the feature extraction capability of the model. Secondly, the large separable kernel attention is introduced into the spatial pyramid pooling fast (SPPF) layer to effectively reduce the interference factors in the complex environment. Thirdly, to address the problem of low quality of captured images, Wise-IoU (WIoU) is used to replace CIoU in the original YOLOv8 to optimize the loss function and improve the model's robustness. The experimental results show that the model achieves 85.7% in the mAP50-95, surpassing the YOLOv8s model by 2.1%. Compared with other mainstream models, the overall performance of our model is much better and can effectively detect the parental care behavior of A. davidianus. Our research method not only offers a reference for the behavior recognition of A. davidianus and other amphibians but also provides a new strategy for the smart breeding of A. davidianus.

The Negative Effect of Siblings on Perspective-Taking in Adulthood under Chinese Culture.

Evidence from Western developed countries has consistently found that children with sibling(s) showed better perspective-taking (PT) than only children. However, this was not the case in developing countries like China. Our study investigates whether the potentially hindering effect of having sibling(s) on PT persists into adulthood within the context of contemporary Chinese culture. We employed self-report questionnaires to measure PT, perceived parental care, and sibling relationships among Chinese young adults (21.93 ± 2.35 years old). Our findings indicate that in China, (1) having sibling(s) hinders individuals' PT in adulthood, (2) a potential mechanism for this effect is that having sibling(s) leads individuals to perceive less parental care during early life, and (3) for those with sibling(s), higher sibling intimacy can enhance PT, particularly among older sister-younger brother pairs. These results suggest that in developing countries such as China, while sibling(s) may diminish PT to some extent, factors like parental care and sibling intimacy can serve as protective factors that mitigate the negative impacts of sibling(s) on PT.

Who cares? Elucidating parental care evolution in extant birds.

Extant birds stand out among vertebrates in the diversity of parental care types they present, spanning absence of care to uniparental care by either sex, biparental or even cooperative care. Despite years of research, key questions remain regarding parental care evolution in birds. Firstly, the parental care type in the most recent ancestor of extant birds is a matter of controversy, with proposed ancestral states including no care, uniparental male or female care, and biparental care. Another unsolved question is the direction, order, and frequency of transitions between parental care types. We address these key questions using a database of 5,438 bird species (~50% of extant diversity) and modern phylogenetic comparative methods controlling simultaneously for model and phylogenetic uncertainty as well as potential confounding effects of state-dependent diversification. Our results indicate that the most likely ancestral state for extant birds is male-only care, with a posterior probability of 0.8. Transition rates across parental care types were generally low and heterogenous; loss of parental care virtually never occurs and transitions away from female only or cooperative care most often lead to biparental care. Given the low transition rates, future research should analyze the factors favoring the maintenance of care types.

Evolutionary biology of social expertise.

There is increasing evidence that competent handling of social interactions among conspecifics has positive effects on individual fitness. While individual variation in social competence has been appreciated, the role of long-term experience in the acquisition of superior social skills has received less attention. With the goal of promoting further research, we integrate knowledge across disciplines to assess social expertise, defined as the characteristics, skills and knowledge allowing individuals with extensive social experience to perform significantly better than novices on a given social task. We focus on three categories of social behaviour. First, animals can gain from adjusting social behaviour towards individually recognised conspecifics that they interact with on a regular basis. For example, there is evidence that some territorial animals individually recognise their neighbours and modify their social interactions based on experience with each neighbour. Similarly, individuals in group-living species learn to associate with specific group members based on their expected benefits from such social connections. Individuals have also been found to devote considerable time and effort to learning about the spatial location and timing of sexual receptivity of opposite-sex neighbours to optimise reproduction. Second, signallers can enhance their signals, and receivers can refine their response to signals with experience. In many birds and insects, individuals can produce more consistent signals with experience, and females across a wide taxonomic range can adaptively adjust mating preferences after perceiving distinct male signals. Third, in many species, individuals that succeed in reproducing encounter the novel, complex task of caring for vulnerable offspring. Evidence from a few species of mammals indicates that mothers improve in providing for and protecting their young over successive broods. Finally, for social expertise to evolve, heritable variation in social expertise has to be positively associated with fitness. Heritable variation has been shown in traits contributing to social expertise including social attention, empathy, individual recognition and maternal care. There are currently limited data associating social expertise with fitness, most likely owing to sparse research effort. Exceptions include maternal care, signal refinement, and familiarity with neighbours and group members. Overall, there is evidence that individuals in many species keep refining their social skills with experience throughout life. Hence we propose promising lines of research that can quantify more thoroughly the development of social expertise and its effects on fitness.

Exploring the Unique and Interactive Effects Between Callous-Unemotional and Autistic Traits with Parental Practices, Care, and Distress in a Community Sample.

Parental practices and stress are associated with both CU and autistic traits, with parents of children with these traits facing challenges that other parents do not encounter. However, the majority of available studies focused mainly on the unique effects of CU and autistic traits with parental stress and practices without exploring their interaction. The current study examines the distinct associations and interactions between CU and autistic traits with parental practices (parental involvement, poor monitoring, inconsistent discipline, and corporal punishment), care, and distress after considering the effect of conduct problems (CPs), age and sex in a Greek-Cypriot sample (N = 146, Mage = 7.30, SD = 1.43). Hierarchical multiple regression analysis revealed that children with CU traits were more likely to experience negative parenting, while parents showed heightened levels of distress. Notably, the study found no association between CU traits and positive parental practices. Further analysis indicated no significant relation between autistic traits and interactions with the target variables, signifying that these traits are not associated with difficulties in parenting and distress. No sex differences were found in all analyses. Age was negatively significant only in relation to parental distress These findings provide valuable insights into the impact of CU traits and underscore the need for additional studies investigating the impact of autistic traits, possibly within clinical samples.

Coevolution of longevity and female germline maintenance.

An often-overlooked aspect of life-history optimization is the allocation of resources to protect the germline and secure safe transmission of genetic information. While failure to do so renders significant fitness consequences in future generations, germline maintenance comes with substantial costs. Thus, germline allocation should trade off with other life-history decisions and be optimized in accordance with an organism's reproductive schedule. Here, we tested this hypothesis by studying germline maintenance in lines of seed beetle, selected for early (E) or late (L) reproduction for 350 and 240 generations, respectively. Female animals provide maintenance and screening of male gametes in their reproductive tract and oocytes. Here, we reveal the ability of young and aged E- and L-females to provide this form of germline maintenance by mating them to males with ejaculates with artificially elevated levels of protein and DNA damage. We find that germline maintenance in E-females peaks at young age and then declines, while the opposite is true for L-females, in accordance with the age of reproduction in the respective regime. These findings identify the central role of allocation to secure germline integrity in life-history evolution and highlight how females can play a crucial role in mitigating the effects of male germline decisions on mutation rate and offspring quality.

Effects of acute inhibition of dopamine ß-hydroxylase on neural responses to pups in adult virgin male California mice (Peromyscus californicus).

The neural mechanisms underlying paternal care in biparental mammals are not well understood. The California mouse (Peromyscus californicus) is a biparental rodent in which virtually all fathers are attracted to pups, while virgin males vary widely in their behavior toward unrelated infants, ranging from attacking to avoiding to huddling and grooming pups. We previously showed that pharmacologically inhibiting the synthesis of the neurotransmitter norepinephrine (NE) with the dopamine ß-hydroxylase inhibitor nepicastat reduced the propensity of virgin male and female California mice to interact with pups. The current study tested the hypothesis that nepicastat would reduce pup-induced c-Fos immunoreactivity, a cellular marker of neural activity, in the medial preoptic area (MPOA), medial amygdala (MeA), basolateral amygdala (BLA), and bed nucleus of the stria terminalis (BNST), brain regions implicated in the control of parental behavior and/or anxiety. Virgin males were injected with nepicastat (75 mg/kg, i.p.) or vehicle 2 hours prior to exposure to either an unrelated pup or novel object for 60 minutes (n = 4-6 mice per group). Immediately following the 60-minute stimulus exposure, mice were euthanized and their brains were collected for c-Fos immunohistochemistry. Nepicastat reduced c-Fos expression in the MeA and MPOA of pup-exposed virgin males compared to vehicle-injected controls. In contrast, nepicastat did not alter c-Fos expression in any of the above brain regions following exposure to a novel object. Overall, these results suggest that the noradrenergic system might influence MeA and MPOA function to promote behavioral interactions with pups in virgin males.

Inhibition of alloparental behavior by acute stress in virgin male California mice (Peromyscus californicus).

In many biparental mammals, such as California mice (Peromyscus californicus), fathers display affiliative behavior toward unfamiliar infants whereas reproductively naïve adult males show highly variable responses. Sources of this variability are not well understood, but evidence suggests that stress can either enhance or inhibit alloparental care. We evaluated immediate and delayed effects of acute stress on pup-directed behavior in adult virgin male California mice. Mice underwent three 10-minute tests with unfamiliar pups at 48-hour intervals. Stressed mice (N=22) received a subcutaneous oil injection immediately before tests 1 and 2, whereas controls (N=22) were left undisturbed. In controls, but not stressed mice, latency to approach the pup decreased and duration of alloparental behavior increased across the three tests. At each time point, stressed males were less likely than controls to perform alloparental behavior. Controls spent significantly more time performing alloparental behavior than stressed mice in tests 1 and 2 but not in test 3. Pup-directed aggression did not differ between the groups at any time point. These findings suggest that acute stress can both inhibit alloparental behavior in the short term and prevent the increase in alloparental behavior that typically occurs with repeated exposure to pups in virgin male California mice.