Signaling Aggression

The interrelationship between sleep disturbance symptoms and aggression before and after the campus closure of the COVID-19 pandemic: insight from a cross-lagged panel network model

Background

The COVID-19 pandemic is detrimental to sleep quality and increases aggression among college students. Nevertheless, relevant studies were rare. Hence, we collected longitudinal data during and post-campus closure in the current study to investigate the relationship between sleep disturbance and aggression.

Methods

Data from 665 college students (59.2% females, Meanage = 19.01, SD age = 1.25) were collected before (wave 1) and after (wave 2) the campus closure of COVID-19. All participants were asked to fill out the Buss-Perry Aggression Questionnaire and the Youth Self-Rating Insomnia Scale. Two symptom networks and a cross-lagged panel network were formed and tested.

Results

Hostility has the highest centrality in the symptom network both in waves 1 and 2, and it bridges sleep disturbance and aggression. "Easily be woken" - "wake up too early" and "wake up with tired" - "function hindrance" are two important symptom associations in networks of waves 1 and 2. All symptoms except "difficulty in falling asleep" and "easily be woken" ameliorated after closure. Moreover, "physical aggression" and "hostility" can trigger other symptoms in wave 2.

Conclusion

As the first study about aggression and sleep disturbance in the background of COVID-19, we provide valuable information about the relationship between sleep disturbance and aggression on the symptom dimension.

Social regulation of reproduction: control or signal?

Traditionally, dominant breeders have been considered to be able to control the reproduction of other individuals in multimember groups that have high variance in reproductive success/reproductive skew (e.g., forced sterility/coercion of conspecifics in eusocial animals; sex-change suppression in sequential hermaphrodites). These actions are typically presented as active impositions by reproductively dominant individuals. However, how can individuals regulate the reproductive physiology of others? Alternatively, all contestants make reproductive decisions, and less successful individuals self-downregulate reproduction in the presence of dominant breeders. Shifting perspective from a top-down manipulation to a broader view, which includes all contenders, and using a multitaxon approach, we propose a unifying framework for the resolution of reproductive skew conflicts based on signalling rather than control, along a continuum of levels of strategic regulation of reproduction.

Untangling behaviours: independent expressions of female-female aggression and snake-like hissing in the blue tit (Cyanistes caeruleus)

Aggression plays a crucial role in deterring predators and securing resources to promote fitness. Nevertheless, studies focussing on female aggression remain scarce. In songbirds, aggression is prevalent during the breeding season, when same-sex individuals compete for limited resources. Additionally, females of some bird species exhibit snake-like hissing behaviour during incubation presumably to lower predation rates and improve fitness. Such behaviours may co-vary, forming a behavioural syndrome that could constrain trait expression. Here, we investigated a resident population of blue tits (Cyanistes caeruleus), to examine the repeatability and covariation of female-female aggression and hissing behaviour, aiming to determine if these constitute a behavioural syndrome. We quantified female-female aggression during simulated territorial intrusions and measured number of hissing calls in response to a simulated predator intrusion into the nest box. We found that both female-female aggression and hissing behaviour were repeatable traits, and that older females approached the intruder less. However, we found no evidence of covariation between female-female aggression and hissing behaviour. Thus, our findings suggest that female-female aggression and hissing behaviour, although both displayed in a nest defence context, are evolutionarily independent traits in the blue tit.

Genetic correlation between aggressive signals and fighting

Theoretical analyses indicate that aggressive signals should positively correlate with the signallers' willingness and abilities to fight. Few experimental studies, however, have tested this prediction. In two experiments employing distinct, ecologically realistic protocols, we quantified the association between aggressive signals and fighting in fruit fly genotypes and found high positive genetic correlations between threat and fighting (rG = 0.80 and 0.74). Our results add to the growing body of experimental work indicating that aggressive signals have relatively high informational value.

Females Are More Aggressive Than Males towards Same- and Opposite-Sex Intruders in the Blue Tit (Cyanistes caeruleus)

During the breeding season, aggression is expressed to gain access to resources such as territories and mates and protect offspring. Female aggressiveness has received much less attention than male aggressiveness, and few studies have examined female and male aggressiveness towards intruders of both sexes in the same species. We compared female and male aggressiveness towards same- and opposite-sex intruders during the egg-laying period in blue tits (Cyanistes caeruleus) using simulated territorial intrusions. For each sex, we examined the occurrence of different behavioural responses during agonistic encounters, and compared the intensity and individual consistency of intra- and inter-sexual aggression using same- and opposite-sex taxidermy mounts. Our results show that females are the more aggressive sex. Both sexes showed similar behaviours during simulated intrusions, although females were never observed singing and males never entered the nest box. In females, aggression was predominantly independent of the sex of the intruder, while males sang more from a distance during male-male encounters. The relative levels of aggression (pecking and perching on the mounts) during intra- and intersexual conflicts were consistent for females, but not for males. Females might be under stronger selection for aggressive phenotypes due to nest-hole competition and larger reproductive investments.

Pre-exposure via wire-mesh partition reduces intraspecific aggression in male, wild-type Norway rats

There are instances when animals are introduced and expected to live alongside unfamiliar conspecifics within zoos, laboratories and wildlife sanctuaries. These pairings of unfamiliar animals may result in stress, trauma, or even death, in addition to reduced confidence in data resulting from these subjects. For species that communicate relatedness, sex, social status, and emotional state through olfactory cues (eg pheromones), one means of counteracting aggression may involve a period of partial separation — where animals are close enough to become acquainted — while a permeable barrier maintains separation. For our study, we evaluated the use of a novel, autoclavable, wire-mesh partition to separate potential aggressors. We tested different pairs of 24 wild-type male Norway rats (Rattus norvegicus), previously kept in social isolation for seven days. Each control pair were merged directly into one cage, while pairs from the experimental groups underwent three pre-exposure sessions that lasted two to four days. We used continuous video recordings to assess five common threat displays: lateral threat, keep down, upright posture, chase, and clinch attack. We used two types of bedding: new (unscented) bedding and recently used bedding that conveyed scents from both merged rats. We found that rats subjected to pre-exposure demonstrated lower aggression levels across three of the five metrics (lateral threats, upright postures, and keep downs). We conclude that permeable partitions show promise as a humane mechanism to mix new individuals into preexisting colonies. Further research may explore whether partitions could be helpful with other species that communicate social information by pheromones or direct visual inspection.

Brains, brawn, and beauty: The complementary roles of intelligence and physical aggression in attracting sexual partners

The current study compared physical aggression to factors affecting socioeconomic status in the accumulation of sex partners over the life course. Our data sample was drawn from the National Longitudinal Study of Adolescent to Adult Health (men, n = 5,636; women, n = 6,787). Participants were examined in terms of the number of lifetime sex partners they reported, nonrelationship partners, cheating or infidelity, and concurrent relationships. Intelligence and physical violence emerged as being especially likely to boost sex partner accumulation for the number of lifetime sex partners and nonrelationship partners in men. Intelligence also interacted positively with men's violence in cross-sectional models but not longitudinally. Women's violence was not significant regardless of the outcome or model specification. Intelligence showed less consistent effects for women's mating indicators compared to men. Analyses controlled for well-known correlates of aggression and sexual behavior and factors associated with beauty, including interviewer reports of survey participants' physical attractiveness and maturity, as well as self-reported attractiveness, maturity, and health. Findings are consistent with evolutionary ideas regarding costly signaling as an effective mating strategy among men.

The Evolution and Ecology of Bacterial Warfare

Bacteria have evolved a wide range of mechanisms to harm and kill their competitors, including chemical, mechanical and biological weapons. Here we review the incredible diversity of bacterial weapon systems, which comprise antibiotics, toxic proteins, mechanical weapons that stab and pierce, viruses, and more. The evolution of bacterial weapons is shaped by many factors, including cell density and nutrient abundance, and how strains are arranged in space. Bacteria also employ a diverse range of combat behaviours, including pre-emptive attacks, suicidal attacks, and reciprocation (tit-for-tat). However, why bacteria carry so many weapons, and why they are so often used, remains poorly understood. By comparison with animals, we argue that the way that bacteria live - often in dense and genetically diverse communities - is likely to be key to their aggression as it encourages them to dig in and fight alongside their clonemates. The intensity of bacterial aggression is such that it can strongly affect communities, via complex coevolutionary and eco-evolutionary dynamics, which influence species over space and time. Bacterial warfare is a fascinating topic for ecology and evolution, as well as one of increasing relevance. Understanding how bacteria win wars is important for the goal of manipulating the human microbiome and other important microbial systems.

Facial expression as a potential measure of both intent and emotion

Facial expressions convey information on emotion, physical sensations, and intent. The much debated theories that facial expressions can be emotions or signals of intent have largely remained separated in animal studies. Here we integrate these approaches with the aim to 1) investigate whether pigs may use facial expressions as a signal of intent and; 2) quantify differences in facial metrics between different contexts of potentially negative emotional state. Facial metrics of 38 pigs were recorded prior to aggression, during aggression and during retreat from being attacked in a dyadic contest. Ear angle, snout ratio (length/height) and eye ratio from 572 images were measured. Prior to the occurrence of aggression, eventual initiators of the first bite had a smaller snout ratio and eventual winners showed a non-significant tendency to have their ears forward more than eventual losers. During aggression, pigs' ears were more forward orientated and their snout ratio was smaller. During retreat, pigs' ears were backwards and their eyes open less. The results suggest that facial expressions can communicate aggressive intent related to fight success, and that facial metrics can convey information about emotional responses to contexts involving aggression and fear.

The Current State of Cephalopod Science and Perspectives on the Most Critical Challenges Ahead From Three Early-Career Researchers

Here, three researchers who have recently embarked on careers in cephalopod biology discuss the current state of the field and offer their hopes for the future. Seven major topics are explored: genetics, aquaculture, climate change, welfare, behavior, cognition, and neurobiology. Recent developments in each of these fields are reviewed and the potential of emerging technologies to address specific gaps in knowledge about cephalopods are discussed. Throughout, the authors highlight specific challenges that merit particular focus in the near-term. This review and prospectus is also intended to suggest some concrete near-term goals to cephalopod researchers and inspire those working outside the field to consider the revelatory potential of these remarkable creatures.

Dramatic Fighting by Male Cuttlefish for a Female Mate

Male cuttlefish compete for females with a repertoire of visually dramatic behaviors. Laboratory experiments have explored this system in Sepia officinalis, but corroborative field data have eluded collection attempts by many researchers. While scuba diving in Turkey, we fortuitously filmed an intense sequence of consort/intruder behaviors in which the consort lost and then regained his female mate from the intruder. These agonistic bouts escalated in stages, leading to fast dramatic expression of the elaborate intense zebra display and culminating in biting and inking as the intruder male attempted a forced copulation of the female. When analyzed in the context of game theory, the patterns of fighting behavior were more consistent with mutual assessment than self-assessment of fighting ability. Additional observations of these behaviors in nature are needed to conclusively determine which models best represent conflict resolution, but our field observations agree with laboratory findings and provide a valuable perspective.

Contests with deadly weapons: telson sparring in mantis shrimp (Stomatopoda)

Mantis shrimp strike with extreme impact forces that are deadly to prey. They also strike conspecifics during territorial contests, yet theoretical and empirical findings in aggressive behaviour research suggest competitors should resolve conflicts using signals before escalating to dangerous combat. We tested how Neogonodactylus bredini uses two ritualized behaviours to resolve size-matched contests: meral spread visual displays and telson (tailplate) strikes. We predicted that (i) most contests would be resolved by meral spreads, (ii) meral spreads would reliably signal strike force and (iii) strike force would predict contest success. The results were unexpected for each prediction. Contests were not resolved by meral spreads, instead escalating to striking in 33 of 34 experiments. The size of meral spread components did not strongly correlate with strike force. Strike force did not predict contest success; instead, winners delivered more strikes. Size-matched N. bredini avoid deadly combat not by visual displays, but by ritualistically and repeatedly striking each other's telsons until the loser retreats. We term this behaviour 'telson sparring', analogous to sparring in other weapon systems. We present an alternative framework for mantis shrimp contests in which the fight itself is the signal, serving as a non-lethal indicator of aggressive persistence or endurance.

Socially induced serotonergic fluctuations in the male auditory midbrain correlate with female behavior during courtship

Cues from social partners trigger the activation of socially responsive neuromodulatory systems, priming brain regions including sensory systems to process these cues appropriately. The fidelity with which neuromodulators reflect the qualities of ongoing social interactions in sensory regions is unclear. We addressed this issue by using voltammetry to monitor serotonergic fluctuations in an auditory midbrain nucleus, the inferior colliculus (IC), of male mice (Mus musculus) paired with females, and by concurrently measuring behaviors of both social partners. Serotonergic activity strongly increased in male mice as they courted females, relative to serotonergic activity in the same males during trials with no social partners. Across individual males, average changes in serotonergic activity were negatively correlated with behaviors exhibited by female partners, including broadband squeaks, which relate to rejection of males. In contrast, serotonergic activity did not correlate with male behaviors, including ultrasonic vocalizations. These findings suggest that during courtship, the level of serotonergic activity in the IC of males reflects the valence of the social interaction from the perspective of the male (i.e., whether the female rejects the male or not). As a result, our findings are consistent with the hypothesis that neuromodulatory effects on neural responses in the IC may reflect the reception, rather than the production, of vocal signals.

Short Review on the Aggressive Behaviour: Genetical, Biological Aspects and Oxytocin Relevance

In this mini-review we were interested in describing the main genetic, biological and mechanistic aspects of the aggressive behaviour in human patients and animal models. It seems that violent behaviour and impulsive traits present a multifactorial substrate, which is determined by genetic and non-genetic factors. Thus, aggressivity is regulated by brain regions such as the amygdala, which controls neural circuits for triggering defensive, aggressive or avoidant behaviour. Moreover, other brain structures such as the anterior cingulate cortex and prefrontal cortex regions could modulate circuits involved in aggression. Regarding the genetic aspects, we could mention the mutations in the monoamine oxidase or the polymorphisms of the genes involved in the metabolism of serotonin, such as tryptophan hydroxylase. Also, besides the low levels of serotonin metabolites, which seem to be associated with impulsive and aggressive traits, there are good evidences that deficiencies in glutamate transmission, as well as testosterone, vasopressin, hypochloesterolemia or oxytocin modifications could be related to the aggressive behaviour. Regarding oxytocin we present here in the last chapter the controversial results from the current literature regarding the various effects exhibited by oxytocin administration on the aggressive behavior, considering the increased interest in understanding the role of oxytocin on the main neuropsychiatric disorders.

Short Review on the Aggressive Behaviour: Genetical, Biological Aspects and Oxytocin Relevance

In this mini-review we were interested in describing the main genetic, biological and mechanistic aspects of the aggressive behaviour in human patients and animal models. It seems that violent behaviour and impulsive traits present a multifactorial substrate, which is determined by genetic and non-genetic factors. Thus, aggressivity is regulated by brain regions such as the amygdala, which controls neural circuits for triggering defensive, aggressive or avoidant behaviour. Moreover, other brain structures such as the anterior cingulate cortex and prefrontal cortex regions could modulate circuits involved in aggression. Regarding the genetic aspects, we could mention the mutations in the monoamine oxidase or the polymorphisms of the genes involved in the metabolism of serotonin, such as tryptophan hydroxylase. Also, besides the low levels of serotonin metabolites, which seem to be associated with impulsive and aggressive traits, there are good evidences that deficiencies in glutamate transmission, as well as testosterone, vasopressin, hypochloesterolemia or oxytocin modifications could be related to the aggressive behaviour. Regarding oxytocin we present here in the last chapter the controversial results from the current literature regarding the various effects exhibited by oxytocin administration on the aggressive behavior, considering the increased interest in understanding the role of oxytocin on the main neuropsychiatric disorders.

Power Plays

Both transient and stable facial cues have evolved as essential features of social communication in humans. Accumulating research links actual and perceived aggression to a higher ratio between the height and bizygomatic width of a person’s face (facial width-to-height ratio [WHR]) and shows that digitally increasing this ratio can alter apparent aggressiveness. We present evidence that facial behaviors associated with anger—the state most closely associated with aggressive intentions—also increase facial WHR, mimicking the facial morphology of aggressive individuals. In Study 1, individuals induced to appear aggressive naturally increased their facial WHR using anger-related facial behaviors. In Study 2, we found that validated anger expressions increased facial WHR and that this change predicts increased attributions of aggressiveness. We also found statistical suggestions that anger-related facial behaviors may serve as cues that overrepresent the expresser’s aggressiveness. Our findings suggest that facial behaviors associated with anger may have emerged to facilitate aggressive encounters.

Wake up and smell the conflict: odour signals in female competition

Odour signals used in competitive and aggressive interactions between males are well studied in the context of sexual selection. By contrast, relatively little is known about comparable signals used by females, despite current interest in the evolution of female ornaments and weaponry. Available evidence suggests that odour signals are important in competitive interactions between female mammals, with reductions or reversals of male-biased sexual dimorphism in signalling where female competition is intense. Scent marking is often associated with conflict between females over access to resources or reproductive opportunities. Female scent marks may therefore provide reliable signals of competitive ability that could be used both by competitors and potential mates. Consistent with this hypothesis, we report that aggressive behaviour of female house mice is correlated with the amount of major urinary protein (MUP) excreted in their urine, a polymorphic set of proteins that are used in scent mark signalling. Under semi-natural conditions, females with high MUP output are more likely to produce offspring sired by males that have high reproductive success, and less likely to produce offspring by multiple different sires, suggesting that females with strong MUP signals are monopolized by males of particularly high quality. We conclude that odour signals are worthy of more detailed investigation as mediators of female competition.

How a songbird with a continuous singing style modulates its song when territorially challenged

In songbirds of the temperate zone, often only males sing and their songs serve to attract females and to deter territorial rivals. In many species, males vary certain aspects of their singing behavior when engaged in territorial interactions. Such variation may be an honest signal of the traits of the signaler, such as fighting strength, condition, or aggressive motivation, and may be used by receivers in decisions on whether to retreat or to escalate a fight. This has been studied intensively in species that sing discontinuously, in which songs are alternating with silent pauses. We studied contextual variation in the song of skylarks (Alauda arvensis), a songbird with a large vocal repertoire and a continuous and versatile singing style. We exposed subjects to simulated territorial intrusions by broadcasting conspecific song and recorded their vocal responses. We found that males sing differently if they are singing spontaneously with no other conspecific around than if they are territorially challenged. In this last case, males produced lower-frequency syllables. Furthermore, they increased the sound density of their song: they increased the proportion of sound within song. They seem to do so by singing different elements of their repertoire when singing reactively. Furthermore, they increased the consistency of mean peak frequency: they repeated syllable types with less variability when singing reactively. Such contextual variation suggests that skylarks might use low frequencies, sound density, and song consistency to indicate their competitive potential, and thus, those song features might be important for mutual assessment of competitive abilities.