Antennal Contact Research Articles

Ecological principles for the evolution of communication in collective systems.

Communication allows members of a collective to share information about their environment. Advanced collective systems, such as multicellular organisms and social insect colonies, vary in whether they use communication at all and, if they do, in what types of signals they use, but the origins of these differences are poorly understood. Here, we develop a theoretical framework to investigate the evolution and diversity of communication strategies under collective-level selection. We find that whether communication can evolve depends on a collective's external environment: communication only evolves in sufficiently stable environments, where the costs of sensing are high enough to disfavour independent sensing but not so high that the optimal strategy is to ignore the environment altogether. Moreover, we find that the evolution of diverse signalling strategies-including those relying on prolonged signalling (e.g. honeybee waggle dance), persistence of signals in the environment (e.g. ant trail pheromones) and brief but frequent communicative interactions (e.g. ant antennal contacts)-can be explained theoretically in terms of the interplay between the demands of the environment and internal constraints on the signal. Altogether, we provide a general framework for comparing communication strategies found in nature and uncover simple ecological principles that may contribute to their diversity.

The Phenomenon of a Mixed Colony: the Case of Lasius brunneus and Lasius umbratus (Hymenoptera, Formicidae)

The aim of this work is to study to find out why, in the case of temporary social parasitism, a mixed colony of Lasius brunneus (Latreille, 1798) and Lasius umbratus (Nylander, 1846) exists in this state for many years. In 2023, a mixed colony of L. brunneus (host species) / L. umbratus (temporary social parasite) was discovered in Moldova. This mixed colony is located at the same site where another mixed colony containing Lasius fuliginosus (Latreille, 1798), L. umbratus disappeared in 2017. Video recordings of the intensity of movement of workers of the two species along the trails were made to study the frequency of antennal contacts and to calculate the colony population. Based on the previously used algorithms, it was assumed that the queen oviposition rate of L. umbratus is 1.5 times higher than that of L. niger, while that of L. brunneus is comparable to that of Lasius niger (Linnaeus, 1758). Chi-square test and post-hoc Dunn's test were used for statistical analysis of the data. Mathematical modelling was used to analyse the rate of colony development. Results of the analysis of worker activity on the trail showed that L. brunneus had 11 times more foragers than L. umbratus. A high number of interspecific antennal contacts between workers was recorded. The population of the mixed colony was estimated to be 48.880 L. brunneus and 24.433 L. umbratus workers. Mathematical modelling confirmed the failure of L. brunneus monogyny in a mixed colony and suggested that high L. brunneus abundance is ensured by multiple queens (oligogyny). Probably in 2021, the L. brunneus colony moved to a new habitat, which was invaded by the L. umbratus queen. After the invasion, several L. brunneus queens survived, allowing a mixed colony to exist.

Aggregation Role of Mandibular Gland Secretions in the Giant Tropical Ant Paraponera clavata (Formicidae: Paraponerinae)

Social insects exhibit sophisticated behavioral repertoires to maintain communication and regulate colony activities. To elucidate the behavioral mechanisms of social insects is essential a thorough understanding of morphophysiological characteristics, such as the functionality of exocrine gland secretions. In this study, it was analyzed whether the mandibular gland secretions influence the aggregation behavior of workers of the ant Paraponera clavata. Associated behavioral acts were also studied. Bioassays indicated that mandibular gland extract triggers aggregation behaviors in P. clavata workers. The observed behavioral acts include mandible opening, raising of the antennae, antennal contact with treated filter paper, selfgrooming, cleaning of the abdominal tip, and allogrooming. These observations demonstrate the potential multifunctionality of compounds secreted by mandibular glands within the behavioral repertoire of P. clavata.

Experimentally seeded social cues in the wild: costs to bearers and potential benefits to receivers

Abstract Conspecifics can provide social cues about the presence of key features of the surrounding environment, such as food or predators. Attending to social cues may therefore potentially benefit receivers, or at least be worth following. Yet, bearing social cues could also be costly, particularly if it increases the likelihood of close-range interaction with non-kin. Here, we experimentally seeded social cues in the wild onto focal individuals of the social hermit crab (Coenobita compressus), testing (1) the “potential benefits to receivers” hypothesis, which predicts that receivers will follow social cues to orient toward valuable resources, and (2) the “costs to bearers” hypothesis, which predicts that bearers of social cues will experience direct (physical) costs or indirect (constrained movement) costs due to interaction with receivers. Consistent with hypothesis (1), in natural encounters, conspecifics that crossed paths frequently made antennal contact, potentially gathering social information at close range. In experiments, naive conspecifics followed focal individuals bearing “positive” social cues (about a valuable food resource) significantly more often than they followed individuals bearing less attractive (“neutral” or “ambivalent”) social cues, pointing to a potential benefit. Consistent with hypothesis (2), individuals bearing positive social cues incurred greater direct and indirect costs, being physically flipped more often and achieving shorter displacements compared to individuals bearing other social cues. We conclude that experimentally seeded social cues in the wild can confer costs to bearers and potentially benefit receivers. Broadly, the costs of bearing social cues, revealed here, underscore the importance of not overlooking that social cues may be costly.

Scaling of ant colony interaction networks

In social insect colonies, individuals are physically independent but functionally integrated by interaction networks which provide a foundation for communication and drive the emergence of collective behaviors, including nest architecture, division of labor, and potentially also the social regulation of metabolic rates. To investigate the relationship between interactions, metabolism, and colony size, we varied group size for harvester ant colonies (Pogonomyrmex californicus) and assessed their communication networks based on direct antennal contacts and compared these results with proximity networks and a random movement simulation. We found support for the hypothesis of social regulation; individuals did not interact with each other randomly but exhibited restraint. Connectivity scaled hypometrically with colony size, per-capita interaction rate was scale-invariant, and smaller colonies exhibited higher measures of closeness centrality and edge density, correlating with higher per-capita metabolic rates. Although the immediate energetic cost for two ants to interact is insignificant, the downstream effects of receiving and integrating social information can have metabolic consequences. Our results indicate that individuals in larger colonies are relatively more insulated from each other, a factor that may reduce or filter noisy stimuli and contribute to the hypometric scaling of their metabolic rates, and perhaps more generally, the evolution of larger colony sizes.

Active tactile exploration and tactually induced turning in tethered walking stick insects.

Many animals use their tactile sense for active exploration and tactually guided behaviors such as near-range orientation. In insects, tactile sensing is often intimately linked to locomotion, resulting in the orchestration of several concurrent active movements, including turning of the entire body, rotation of the head, and searching or sampling movements of the antennae. The present study aims at linking the sequence of tactile contact events to associated changes of all three kinds of these active movements (body, head and antennae). To do so, we chose the Indian stick insect Carausius morosus, an organism commonly used to study sensory control of locomotion. Methodologically, we combined recordings of walking speed, heading, whole-body kinematics and antennal contact sequences during stationary, tethered walking and controlled presentation of an 'artificial twig' for tactile exploration. Our results show that object presentation episodes as brief as 5s are sufficient to allow for a systematic investigation of tactually induced turning behavior in walking stick insects. Animals began antennating the artificial twig within 0.5 s, and altered the beating fields of both antennae in a position-dependent manner. This change was mainly carried by a systematic shift of the head-scape joint movement and accompanied by associated changes in contact likelihood, contact location and sampling direction of the antennae. The turning tendency of the insect also depended on stimulus position, whereas the active, rhythmic head rotation remained unaffected by stimulus presentation. We conclude that the azimuth of contact location is a key parameter of active tactile exploration and tactually induced turning in stick insects.

Spatial perception mediated by insect antennal mechanosensory system

ABSTRACTAnimals perceive their surroundings using various modalities of sensory inputs to guide their locomotion. Nocturnal insects such as crickets use mechanosensory inputs mediated by their antennae to orient in darkness. Spatial information is acquired via voluntary antennal contacts with surrounding objects, but it remains unclear whether the insects modulate behaviors mediated by other sensory organs based on that information. Crickets exhibit escape behavior in response to a short air puff, which is detected by the abdominal mechanosensory organs called cerci and is perceived as a ‘predator approach’ signal. We placed objects of different shapes at different locations with which the cricket actively made contact using its antennae. We then examined the effects on wind-elicited escape behavior. The crickets changed their movement trajectory in response to nearby objects such as walls so that they could avoid collision with these obstacles even during the cercal-mediated behavior. For instance, when a wall was placed in front of the crickets so that it was detected by one antenna, the escape trajectory in response to a stimulus from behind was significantly biased toward the side opposite the wall. Even when the antenna on the free side without the wall was ablated, this collision avoidance was also observed, suggesting that the mechanosensory inputs from one antennae detecting an object edge would be sufficient to perceive the location of obstacle in front. This study demonstrated that crickets were able to use the spatial information acquired with their antennal system to modify their behavior mediated by other sensory organs.

The effect of temperature on host patch exploitation by an egg parasitoid.

The effect of temperature during host patch exploitation by parasitoids remains poorly understood, despite its importance on female reproductive success. Under laboratory conditions, we explored the behaviour of Anaphes listronoti, an egg parasitoid of the carrot weevil, Listronotus oregonensis, when foraging on a host patch at five temperatures. Temperature had a strong effect on the female tendency to exploit the patch: A. listronoti females parasitized more eggs at intermediate temperature (20 to 30°C) compared to those foraging at the extreme of the range (15.9°C and 32.8°C). However, there was no difference in offspring sex-ratio and clutch size between temperature treatments. Mechanisms of host acceptance within a patch differed between temperatures, especially at 32.8°C where females used ovipositor insertion rather than antennal contact to assess whether a host was already parasitized or not, suggesting that host handling and chemical cues detection were probably constrained at high temperature. Females spent less time on the host patch with increasing temperatures, but temperature had no effect on patch-leaving rules. Our results show that foraging A. listronoti females behave better than expected at sub-optimal temperatures, but worse than expected at supra-optimal temperatures. This could impair parasitoid performance under ongoing climate change.

Condition-dependent male copulatory courtship and its benefits for females.

Postcopulatory sexual selection has shaped the ornaments used during copulatory courtship. However, we know relatively little about whether these courtship ornaments are costly to produce or whether they provide indirect benefits to females. We used the mealworm beetle, Tenebrio molitor, to explore this. We challenged males using an entomopathogenic fungus and compared their courtship (frequency of leg and antennal contacts to the female), copulation duration, number of eggs laid, and hatching rate against control males. Infected males copulated for longer yet they reduced their leg and antennal contacts compared to control males. However, there was no obvious relation between infection, copulation duration, and courtship with egg production and hatching success. In general, our results indicate that the ornaments used during postcopulatory courtship are condition‐dependent. Moreover, such condition dependence cannot be linked to male fitness.

Input of hair field afferents to a descending interneuron.

In insects the tactile sense is important for near-range orientation and is involved in various behaviors. Nocturnal insects, such as the stick insect Carausius morosus, continuously explore their surroundings by actively moving their antennae when walking. Upon antennal contact with objects, stick insects show a targeted front-leg movement. As this reaction occurs within 40 ms, descending transfer of information from the brain to the thorax needs to be fast. So far, a number of descending interneurons have been described that may be involved in this reach-to-grasp behavior. One of these is the contralateral ON-type velocity-sensitive neuron (cONv). cONv was found to encode antennal joint-angle velocity during passive movement. Here, we characterize the transient response properties of cONv, including its dependence on joint angle range and direction. As antennal hair field afferent terminals were shown to arborize close to cONv dendrites, we test whether antennal hair fields contribute to the joint-angle velocity encoding of cONv. To do so, we conducted bilateral extracellular recordings of both cONv interneurons per animal before and after hair field ablations. Our results show that cONv responses are highly transient, with velocity-dependent differences in delay and response magnitude. As yet, the steady state activity level was maintained until the stop of antennal movement, irrespective of movement velocity. Hair field ablation caused a moderate but significant reduction of movement-induced cONv firing rate by up to 40%. We conclude that antennal proprioceptive hair fields contribute to the velocity-tuning of cONv, though further antennal mechanoreceptors must be involved, too.NEW & NOTEWORTHY Active tactile exploration and tactually induced behaviors are important for many animals. They require descending information transfer about tactile sensor movement to thoracic networks. Here, we investigate response properties and afferent input to the identified descending interneuron cONv in stick insects. cONv may be involved in tactually induced reach-to-grasp movements. We show that cONv response delay, transient and steady state are velocity-dependent and that antennal proprioceptive hair fields contribute to the velocity encoding of cONv.

Goals and Limitations of Modeling Collective Behavior in Biological Systems

Local social interactions among individuals in animal groups generate collective behavior, allowing groups to adjust to changing conditions. Historically, scientists from different disciplines have taken different approaches to modeling collective behavior. We describe how each can contribute to the goal of understanding natural systems. Simple bottom-up models that describe individuals and their interactions directly have demonstrated that local interactions far from equilibrium can generate collective states. However, such simple models are not likely to describe accurately the actual mechanisms and interactions in play in any real biological system. Other classes of top-down models that describe group-level behavior directly have been proposed for groups where the function of the collective behavior is understood. Such models cannot necessarily explain why or how such functions emerge from first principles. Because modeling approaches have different strengths and weaknesses and no single approach will always be best, we argue that models of collective behavior that are aimed at understanding real biological systems should be formulated to address specific questions and to allow for validation. As examples, we discuss four forms of collective behavior that differ both in the interactions that produce the collective behavior and in ecological context, and thus require very different modeling frameworks. 1) Harvester ants use local interactions consisting of brief antennal contact, in which one ant assesses the cuticular hydrocarbon profile of another, to regulate foraging activity, which can be modeled as a closed-loop excitable system. 2) Arboreal turtle ants form trail networks in the canopy of the tropical forest, using trail pheromone; one ant detects the volatile chemical that another has recently deposited. The process that maintains and repairs the trail, which can be modeled as a distributed algorithm, is constrained by the physical configuration of the network of vegetation in which they travel. 3) Swarms of midges interact acoustically and non-locally, and can be well described as agents moving in an emergent potential well that is representative of the swarm as a whole rather than individuals. 4) Flocks of jackdaws change their effective interactions depending on ecological context, using topological distance when traveling but metric distance when mobbing. We discuss how different research questions about these systems have led to different modeling approaches.

Movement, Encounter Rate, and Collective Behavior in Ant Colonies.

Spatial patterns of movement regulate many aspects of social insect behavior, because how workers move around, and how many are there, determines how often they meet and interact. Interactions are usually olfactory; for example, in ants, by means of antennal contact in which one worker assesses the cuticular hydrocarbons of another. Encounter rates may be a simple outcome of local density: a worker experiences more encounters, the more other workers there are around it. This means that encounter rate can be used as a cue for overall density even though no individual can assess global density. Encounter rate as a cue for local density regulates many aspects of social insect behavior, including collective search, task allocation, nest choice, and traffic flow. As colonies grow older and larger, encounter rates change, which leads to changes in task allocation. Nest size affects local density and movement patterns, which influences encounter rate, so that nest size and connectivity influence colony behavior. However, encounter rate is not a simple function of local density when individuals change their movement in response to encounters, thus influencing further encounter rates. Natural selection on the regulation of collective behavior can draw on variation within and among colonies in the relation of movement patterns, encounter rate, and response to encounters.

Exploring the factors involved in the absence of parasitism of Chaetosiphon fragaefolii by generalist parasitoids in strawberry

Chaetosiphon fragaefolii Cockerell (Hemiptera: Aphididae) is a worldwide strawberry pest with scarce records of parasitoids for its control. The parasitization rate of two generalist parasitoids, Aphidius colemani Viereck and Aphidius matricariae Haliday, their behavior and aphid defensive behaviors were evaluated with Aphis gossypii Glover (Hemiptera: Aphididae) as a comparative host. Defensive endosymbionts were also surveyed. C. fragaefolii was never parasitized in simple-choice tests, whereas in preference tests both parasitoids chose A. gossypii over C. fragaefolii. No contacts of A. matricariae with C. fragaefolii were observed while A. colemani made more antennal contacts and “stings” on A. gossypii than on C. fragaefolii with the latter exhibiting less defensive behaviors against the parasitoid. The bacterium Acinetobacter sp. was detected in all samples of C. fragaefolii, but with an unknown function. Further research on the possible defensive role of the glandular hairs covering the body of this aphid, the role of chemical signals and the existence of defensive internal mechanisms against parasitoids could provide plausible explanations for the absence of parasitism found.

Bottom-up regulation of a tritrophic system by Beet yellows virus infection: consequences for aphid-parasitoid foraging behaviour and development.

Effects of plants on herbivores can cascade up the food web and modulate the abundance of higher trophic levels. In agro-ecosystems, plant viruses can affect the interactions between crops, crop pests, and natural enemies. Little is known, however, about the effects of viruses on higher trophic levels, including parasitoids and their ability for pest regulation. We tested the hypothesis that a plant virus affects parasitoid foraging behaviour through cascading effects on higher trophic levels. We predicted that the semi-persistent Beet yellows virus (BYV) would influence plant (Beta vulgaris) quality, as well as aphid host (Aphis fabae) quality for a parasitoid Lysiphlebus fabarum. We determined amino acid and sugar content in healthy and infected plants (first trophic level), lipid content and body size of aphids (second trophic level) fed on both plants, as well as foraging behaviour and body size of parasitoids (third trophic level) that developed on aphids fed on both plants. Our results showed that virus infection increased sugars and decreased total amino acid content in B. vulgaris. We further observed an increase in aphid size without modification in host aphid quality (i.e., lipid content), and a slight effect on parasitoid behaviour through an increased number of antennal contacts with host aphids. Although the BYV virus clearly affected the first two trophic levels, it did not affect development or emergence of parasitoids. As the parasitoid L. fabarum does not seem to be affected by the virus, we discuss the possibility of using it for the development of targeted biological control against aphids.

Functional unification of sex pheromone-receptive glomeruli in the invasive Turkestan cockroach derived from the genus Periplaneta

Female Periplaneta americana cockroaches emit two cooperatively working pheromone components, periplanone-B (PB) as a long-range attractant and periplanone-A (PA) as a short-range arrestant, and males develop enlarged glomeruli for processing them separately in the first-order olfactory center. Using intracellular recordings and neuronal labelings, we found that the Turkestan cockroach, Blatta lateralis, which is phylogenetically close to P. americana but having adapted to inground habitats, has an extraordinary large glomerulus. This is caused by drastic enlargement of the PB-responsive glomerulus but not the PA-responsive glomerulus during the late nymphal stage. The output neuron from the macroglomerulus is sensitive to both PA and PB, at a dose of only 0.1 fg. Nevertheless, B. lateralis males never exhibited courtship rituals in response to the presentation of periplanones or natural sex pheromone but exhibited courtship rituals in response to antennal contact with females. Our findings indicate that the unique behavioral ecology and habitats of B. lateralis are related to the functional unification of the pheromone processing system, opposite to the functional differentiation that often underlies species diversification.

Queen and king recognition in the subterranean termite, Reticulitermes flavipes: Evidence for royal recognition pheromones.

Royal recognition is a central feature of insect societies, allowing them to maintain the reproductive division of labor and regulate colony demography. Queen recognition has been broadly demonstrated and queen recognition pheromones have been identified in social hymenopterans, and in one termite species. Here we describe behaviors that are elicited in workers and soldiers by neotenic queens and kings of the subterranean termite, Reticulitermes flavipes, and demonstrate the chemical basis for the behavior. Workers and soldiers readily perform a lateral or longitudinal shaking behavior upon antennal contact with queens and kings. When royal cuticular chemicals are transferred to live workers or inert glass dummies, they elicit antennation and shaking in a dose-dependent manner. The striking response to reproductives and their cuticular extracts suggests that royal-specific cuticular compounds act as recognition pheromones and that shaking behavior is a clear and measurable queen and king recognition response in this termite species.

Antennae and the role of olfaction and contact stimulation in mate recognition by males of the pollinating fig wasp Ceratosolen gravelyi (Hymenoptera: Agaonidae)

ABSTRACTFinding a mate is a crucial step in sexual reproduction. The mutualism between figs and their pollinators is exploited by many figwasps that develop within their galls and attain sexual maturity simultaneously. Male pollinators carry the specific burden of detecting and opening mating holes in galls containing conspecific females before mating with them. The mating behaviourand antennal sensilla of male pollinators associated with Ficus semicordata was investigated to understand mate recognition. Male Ceratosolen gravelyi located female-containing galls from a distance, but only attempted to chew a mating hole after antennal contact with the gall surface was made. They showed similar responses to females and body extracts but failed to respond to washed female bodies. This behaviour indicates that unidentified chemicals present on the body surfaces of females are sufficient to elicit olfactory attraction and tactile confirmation. Multiporous plate sensilla are candidates for olfactory reception from a distance while basiconic sensilla may be involved in contact chemoreceptor. All of the sensilla are highly localised, on the distal part of the terminal flagellomere, suggesting a response to selection for strong directionality in the complex odour environment of the fig in which messages produced by hundreds of females may confuse precise mate localisation.

Mate Recognition by the Green Mate Borer, Hedypathes betulinus (Coleoptera: Cerambycidae): the Role of Cuticular Compounds

Green mate, Ilex paraguariensis (Aquifoliaceae), is native to South America and its range includes the south of Brazil. Hedypathes betulinus (Coleoptera: Cerambycidae) is considered the most important insect pest of green mate, causing severe damage to plants and significant economic losses. In previous work, laboratory assays were performed to document the mating sequence of this species and the male long-range sex pheromone was identified. Previous reports of the mating sequence suggested that males recognize females only after antennal contact and consequently the existence of a contact sex pheromone. To test the hypothesis that mate-recognition in H. betulinus is mediated by a contact sex pheromone, this study analyzed male and female body extracts by GC-MS. Extracts were fractionated to separate the compounds by polarity, producing hexane, cyclohexene and ether fractions. Active fractions were identified with laboratory bioassays. Bioassays were performed by introducing female cadavers to live males and male copulation response scored (± ). In assays using solvent washed female cadavers, males did not recognize female cadavers, but attempted copulation with female cadavers with the extract re-applied. Cumulatively, these results suggest that a contact sex pheromone on the cuticle of females mediates mate recognition. Laboratory bioassays and analysis of the female solvent extracts produced by fractionation, individually and in binary and ternary combinations, suggests that the more polar compounds present in the ether fraction are crucial to mate recognition in this species.

Regulation of harvester ant foraging as a closed-loop excitable system.

Ant colonies regulate activity in response to changing conditions without using centralized control. Desert harvester ant colonies forage for seeds, and regulate foraging to manage a tradeoff between spending and obtaining water. Foragers lose water while outside in the dry air, but ants obtain water by metabolizing the fats in the seeds they eat. Previous work shows that the rate at which an outgoing forager leaves the nest depends on its recent rate of brief antennal contacts with incoming foragers carrying food. We examine how this process can yield foraging rates that are robust to uncertainty and responsive to temperature and humidity across minute-to-hour timescales. To explore possible mechanisms, we develop a low-dimensional analytical model with a small number of parameters that captures observed foraging behavior. The model uses excitability dynamics to represent response to interactions inside the nest and a random delay distribution to represent foraging time outside the nest. We show how feedback from outgoing foragers returning to the nest stabilizes the incoming and outgoing foraging rates to a common value determined by the volatility of available foragers. The model exhibits a critical volatility above which there is sustained foraging at a constant rate and below which foraging stops. To explain how foraging rates adjust to temperature and humidity, we propose that foragers modify their volatility after they leave the nest and become exposed to the environment. Our study highlights the importance of feedback in the regulation of foraging activity and shows how modulation of volatility can explain how foraging activity responds to conditions and varies across colonies. Our model elucidates the role of feedback across many timescales in collective behavior, and may be generalized to other systems driven by excitable dynamics, such as neuronal networks.

Loser in Fight but Winner in Love: How Does Inter-Male Competition Determine the Pattern and Outcome of Courtship in Cricket Gryllus bimaculatus?

Animal females are generally assumed to prefer males that tend to win fights (dominant males). However, a growing number of studies in numerous animal taxa demonstrate no correlation between the male fighting ability and their attractiveness, or even female preferences for fight losers (subordinate males). One of the methods to measure female preferences implies using no-choice tests that evaluate a female’s latency to mating when placed with a single male. Considering that courtship behavior generally contains multimodal signaling, we analyzed 19 behavioral elements demonstrated by both sexes of cricket Gryllus bimaculatus during courtship. To estimate the male dominance status, the males were preliminarily tested in two rounds of fights. The females were shown to mount equally often dominant and subordinate males, but the latencies from the start of antennal contact to mount appeared to be shorter in subordinate than dominant males. During courtship, dominant males demonstrated one of the elements of agonistic display, rocking the body, more frequently and longer than subordinate males. This element was negatively correlated with singing in fight winners but was positively correlated with singing a courtship song in fight losers. Rocking is suggested thereby to function as multiple messages. The song parameters were poorly related with male mating success. The dominant males, rather than subordinate males, tended to produce a higher number of calling chirps, which could be explained by inability of dominant males to quickly shift from aggression to courtship behavior. The results obtained suggest that an increased aggression is likely to interfere with subsequent courtship.