Adapted Original Music as an Environmental Enrichment in an Intensive Pig Production System Reduced Aggression in Weaned Pigs during Regrouping.

In intensive swine production systems,, the practice of regrouping unfamiliar pigs is common, often leading to aggressive behavior. Although the effect of different musical genres composed for humans has been evaluated in pigs to mitigate aggression, there have been few attempts to create music specifically for pigs. Here, we assess whether sensory stimulation through music, created by adapting the acoustic parameters in the sound mix, induces changes in the aggressive behaviors of pigs during regrouping. Six litters of 10-week-old piglets were randomly selected and assigned to different treatments. The control group (Group A) received no intervention, while Group B was exposed to music for two continuous hours in the morning and afternoon from the time of regrouping. Group C received musical stimulation for one continuous hour in the morning following regrouping. A significant reduction in the frequency and duration of aggressive behaviors was observed in the groups that received musical stimulation during regrouping. Additionally, social, and individual play behaviors showed a decrease in the musical stimulation groups. These findings provide evidence for the effectiveness of created music as a strategy in reducing aggressive behavior during pig regrouping, which can enhance the welfare of pigs and offer a practical solution for pig producers to minimize aggression and its associated negative impacts.

Spawning ecology of the Saint Paul's Gregory Stegastes sanctipauli, a damselfish endemic to the remote St Peter and St Paul's Archipelago.

We studied the spawning ecology of Stegastes sanctipauli, a damselfish endemic to the small and remote St Peter and St Paul's Archipelago (Brazil), aiming to determine the main correlates of reproductive success, as inferred from rates of egg losses along a spawning season. New clutches appeared mostly in the last quarter moon, when egg predation intensified. Predation by heterospecifics, particularly Halichoeres radiatus (Linnaeus, 1758), accounted for most egg losses, while filial cannibalism showed negligible influence. Predation pressure was highest for larger nests with higher initial density of eggs. Hatching of eggs occurred close to the new moon (i.e., ~5 days after spawning). Most nests occur in shallow reefs (<16 m depth), where main food resources for adults (turf algae) are concentrated, but abundance of egg predators, particularly H. radiatus, is also highest. This latter result suggests that the spawning activity of S. sanctipauli is influenced by the trade-offs between food accessibility by adults and egg predation risk. The patterns recorded here are similar to those known for other tropical damselfish species and may reflect strategies for attenuating predation pressure over new fry and eggs.

Hierarchy Establishment in Growing Finishing Pigs: Impacts on Behavior, Growth Performance, and Physiological Parameters.

In recent years, an increased number of studies have dealt with the analysis of social dominance related to animal behavior, physiology, and performance. This study aimed to investigate whether hierarchical ranking affects the coping style, non-social behavior during open field and novel object tests, performance, and physiological parameters of pigs. A total of 48 growing pigs (24 barrows and 24 females) were mixed three times during the growing-finishing period. The social and non-social behaviors of pigs were directly noted, and three behavioral tests were performed during the experimental period. Performance and physiological parameters were also recorded. Statistical analysis considered hierarchical classification (dominant vs. intermediary vs. subordinate) and p-values ≤ 0.05 were considered significant. After three regroupings, the pigs in different hierarchical classifications showed no change in hair cortisol values and open-field and novel object tests. Mean corpuscular hemoglobin concentration and leukocyte values increased in intermediary pigs, and the lowest counts were found in pigs classified as dominants. Furthermore, dominant pigs visited the feeder more but spent shorter time there compared to subordinate and intermediary pigs. Our results suggest that hierarchical classification influenced feeding behavior and physiological parameters without affecting cortisol values and growth performance, demonstrating a possible compensation skill.

Dominance style and intersexual hierarchy in wild bonobos from Wamba.

Dominance hierarchies vary between species and possess particular characteristics depending on the distribution and abundance of food resources that affect the competitive regime. Bonobos have been described as having female intersexual dominance, based mainly on female coalitionary support against males, and more egalitarian hierarchies than chimpanzees. In this study, we tested whether female intersexual dominance is dependent on female coalitions or whether it still arises when only dyadic interactions are considered. We also examined the role of food abundance in shaping dominance style in a wild population of bonobos in Wamba, Democratic Republic of Congo. We found partial support concerning our first prediction in which we expected a male dominance over females when only dyadic agonistic interactions were considered because females were not systematically dominant over males, finding instead an intersexual codominance pattern. We failed to find support for our second prediction that hierarchies become more despotic under low fruit abundance, in fact, we found the opposite pattern. We discuss that codominance based on dyadic interactions in this group may arise as a consequence of male deference rather than females winning conflicts against males and that more despotic hierarchies during high fruit season may arise as a consequence of competition for high-quality resources or variation in party size.

Aggressive interactions and consistency of dominance hierarchies of the native and nonnative cichlid fishes of the Balsas basin.

Dominance hierarchies are generally established based on the levels of aggressiveness that animals present. Frequently, animals fight to establish a dominance hierarchy and obtain a disputed resource. The Mexican mojarra Cichlasoma istlanum is a native species of the Balsas river basin and coexists there with four nonnative cichlids: tilapia Oreochromis sp., convict cichlid Amatitlania nigrofasciata, spotcheek cichlid Thorichthys maculipinnis, and green terror Andinoacara rivulatus. These five cichlid species compete for spaces for reproduction, feeding, and shelter and frequently engage in aggressive interactions to obtain these resources. We quantified dominance indices to evaluate the hierarchical structure of dominance among these five cichlids and the duration of aggressive behaviors of the Mexican mojarra during experimental contests between the native species and each of the four nonnative species. The Mexican mojarra was consistently dominant over the other four cichlid species, performing a larger number of aggressive behaviors and investing more time in attacking than the nonnative cichlids, which resulted in a higher hierarchical position. Our results show that the native fish, Mexican mojarra, established dominance over all four nonnative cichlid fish of the Balsas basin. Thus, the establishment of nonnative cichlid species in the Balsas basin is likely associated with factors other than behavioral dominance.

Boosting Antitumor Response by Costimulatory Strategies Driven to 4-1BB and OX40 T-cell Receptors.

Immunotherapy explores several strategies to enhance the host immune system's ability to detect and eliminate cancer cells. The use of antibodies that block immunological checkpoints, such as anti-programed death 1/programed death 1 ligand and cytotoxic T-lymphocyte-associated protein 4, is widely recognized to generate a long-lasting antitumor immune response in several types of cancer. Evidence indicates that the elimination of tumors by T cells is the key for tumor control. It is well known that costimulatory and coinhibitory pathways are critical regulators in the activation of T cells. Besides blocking checkpoints inhibitors, the agonistic signaling on costimulatory molecules also plays an important role in T-cell activation and antitumor response. Therefore, molecules driven to costimulatory pathways constitute promising targets in cancer therapy. The costimulation of tumor necrosis factor superfamily receptors on lymphocytes surface may transduce signals that control the survival, proliferation, differentiation, and effector functions of these immune cells. Among the members of the tumor necrosis factor receptor superfamily, there are 4-1BB and OX40. Several clinical studies have been carried out targeting these molecules, with agonist monoclonal antibodies, and preclinical studies exploring their ligands and other experimental approaches. In this review, we discuss functional aspects of 4-1BB and OX40 costimulation, as well as the progress of its application in immunotherapies.

Dear enemy effect in the Mexican volcano mouse Neotomodon alstoni: Implications of sex in the agonistic behaviour among neighbours.

Two opposite phenomena have been found in territorial animals, the "dear enemy'' and the "nasty neighbour'', which refer to individuals that show less aggression toward neighbours than toward strangers and vice versa. However, the need to maintain territory should differ for males and females because sexual reproduction is the result of the different adaptive strategies of the sexes. In this study, we explore territorial behaviour in the context of dear-enemy and nasty neighbour effects in the Mexican volcano mouse (Neotomodon alstoni). Patterns of spatial relationships between individuals and the degrees of agonistic behaviour among neighbours were analysed for a period of one year. Results exhibit a greater spatial proximity between male pairs during the non-reproductive period than during the reproductive period, and greater spatial proximity between pairs of females during the reproductive period than during the non-reproductive period. The analysis of agonistic behaviour showed that there is less tolerance for distant neighbours than for nearest neighbours. However, there is a greater frequency of aggression between male pairs than between females, while females appear to exhibit non-aggressive avoidance among individuals. The results support the theory that Mexican volcano mouse exhibits the "dear enemy phenomenon".

Effect of previous fighting on the dynamic of agonistic encounters in zebrafish males.

Aggression among individuals which compete for resources such as food or territory, or to establish dominance relationships, can cause injuries that may be risky for the contenders. In this way, individuals of many species have strategies to resolve conflicts reducing levels of aggression. Thus, if individuals are able to recognize each other and remember previous agonistic experiences and the result of the fight, they will resolve the subsequent encounter with lower levels of aggression. Here, we evaluated the effect of previous fighting experiences (24 h interval) on agonistic behaviors of subsequent encounters in zebrafish (Danio rerio) males. Specifically, we examined if any reduction in aggression is because of an individual's ability to remember other individuals from previous interactions, or if reductions come directly from winning or losing a fight. We found that when a pair of opponents (of the same size) had fought, and 24 h later the same dyad fought again, the number of bites decreases 85% and the duration of aggression decreases 73% in the second encounter, and this effect persisted in a third encounter (a decrease of 90% and 95%, respectively). To evaluate if the effect of previous experience on agonistic behaviors depended on facing the same opponent, in the second fight of a new experiment the opponent was changed. In this case, no decreases in the number of bites or in the duration of aggression was observed. In conclusion, pairs of zebrafish males resolve a conflict with lower levels of aggression when having previously fought with that particular opponent, but not with an unknown opponent. As a whole, these results suggest that zebrafish males are capable of recognizing the opponent, remembering previous experiences and changing their fighting strategies accordingly, but not only as a consequence of the result of a previous encounter.

Time of Grain Supplementation and Social Dominance Modify Feeding Behavior of Heifers in Rotational Grazing Systems.

Social hierarchy affects the access of animals to feed resources. On daily rotational pasture systems, supplementation time may influence feeding behavior. This trial was designed to test the effect of grain delivery time on the feeding behavior of heifers. Heifers divided into two groups according to breed (n = 15 Braford and n = 19 Jersey) were tested in a crossover design with two treatments: INITIAL-supplement at 8 am (entry time to a fresh paddock), and MIDDLE-supplement at 4 pm (middle time of paddock use). Animals entered a new paddock every morning, and grain supplement at 2 kg/animal/day was offered at the fence line (1 m/animal). Then, ingestive and other behaviors were registered by direct visual observation through scan sampling at 2-min intervals for 1 h after grain supply. Agonistic interactions were recorded continuously (instigator-victim) to build a social matrix whereby each heifer was defined as dominant, intermediate, or subordinate. Weekly pasture samples were collected according to the order that animals left the feeding area, using the hand-plucking technique, to determine crude protein and fiber content. Heifers spent more time grazing on the INITIAL treatment (p < 0.0001) but exhibited more behaviors on the MIDDLE treatment (p < 0.0001). Dominant heifers spent more time eating grain (p = 0.0008), whereas subordinate heifers spent more time grazing along the paddock (p = 0.0067), but not along the fence (p = 0.0008). The crude protein content of pasture samples was higher for the INITIAL treatment (p < 0.0001). Behavioral interaction occurred with respect to the order of leaving the feeding area, social rank, and crude protein consumed (p = 0.04). Subordinate heifers consistently grazed more and ate less grain supplement than dominant and intermediate heifers. However, when grain supplement was offered at the time animals entered the paddock, more grazing activity took place during supplement feeding, and subordinate heifers could select a high-protein diet. In the INITIAL treatment, this means that subordinate animals could benefit from the better pasture available, keeping a distance from dominant heifers, reducing agonistic interactions and likely improving their welfare.

Aggressive interactions among female, semi-captive pampas deer (Ozotoceros bezoarticus) increase within the hierarchy and after short-term removal of the male.

Two trials were carried out to determine: (a) if there is a positive relation between the frequency of aggressive interactions among female pampas deer and their position within the hierarchy (HI), (b) if short-term removal of the male triggers an increase in the frequency of aggression, and (c) if the magnitude of this increase is related to the individual rank position of the female. Each of 19 breeding groups comprised one adult male and from four to six adult females. The HI was determined for each female and all aggressive interactions were recorded. These were recorded while the male was present (i.e., all of Trial 1 and the "with male" period in Trial 2) and after removal of the male (i.e., the "without male" period in Trial 2). The individual percentage change in the frequency of aggressive interactions after male removal was calculated. In Trial 1 the HI, the frequency of different types of aggressive interaction and the total of aggressive interactions were positively related (all: p < .001; General Linear Mixed Model [GLMM]). In Trial 2, the frequency of total aggressive interactions increased after male removal (F(1, 27) = 3.5; p < .001; GLMM). The individual percentage changes in aggressive interaction between periods were positively related to HI (F(6, 24) = 2.56; p = .05; GLMM). For female pampas deer maintained in breeding groups, we conclude that the frequency of aggressive interactions increases within the hierarchy. Aggression also increases after the short-term removal of the male, mainly among females of higher social status.

O guardião dos campos: um estudo sobre o comportamento do quero-quero Vanellus chilensis (Aves: Charadriiformes) no sul do Brasil / Guardian of the fields: a study on the behavior of the Southern Lapwing Vanellus chilensis (Aves: Charadriiformes) in Southern Brazil

The Southern Lapwing Vanellus chilensis (Molina, 1782) is a common bird in Rio Grande do Sul state, south Brazil, but is widely distributed across South America. It inhabits grasslands and other open habitats and it is known by a distinctive black, grey, and white coloration, a conspicuous vocalization and both aggressive and territorial behaviors. Although being recognized as the bird symbol of Rio Grande do Sul, no study about its behavior has yet been carried out in the state. Here, we aimed to describe and quantify the behavioral repertoire of Southern Lapwing. Between December of 2017 and November of 2018, we carried out observations in an eight-hectares grassland site in northern Rio Grande do Sul. We used ad libitum and animal focusing techniques to identify and record the frequency and duration of specific behaviors. An ethogram was elaborated, representing the 23 detected behaviors, grouped in five categories: locomotion, maintenance, feeding, socio-agonistic, and reproduction. Our analysis showed that most behaviors vary in both frequency and duration over the year. We detected high frequency and duration of social-agonistic and reproductive behaviors during the breeding season, while other categories, like feeding and maintenance, showed a decrease in the same period, with greater commitment to protect the eggs and chicks. We also recorded three types of vocalization with different characteristics, one of which occurs exclusively during the breeding season. The results of our study allowed the identification and quantification of V. chilensis in southern Brazil, thus helping in understanding the relations between the species and its habitats in the region.(AU)

O quero-quero Vanellus chilensis (Molina, 1782) é uma ave típica do Estado do Rio Grande do Sul, mas possui ampla distribuição geográfica nos campos da América do Sul, sendo conhecido pelo canto imponente e pelos comportamentos relacionados com a agressividade e a territorialidade. Apesar de ser reconhecido como animal símbolo do estado, nenhum trabalho acerca dos comportamentos dessa ave foi desenvolvido no estado. Este trabalho teve como objetivo qualificar e quantificar o repertório comportamental de V. chilensis. Observações dos comportamentos dessa ave foram feitas em uma área de campo com oito hectares, no município de Torres, RS, entre dezembro de 2017 e novembro de 2018, totalizando 143 horas de observação. Utilizou-se a metodologia de observação de todas as ocorrências e observação de animal focal, coletando-se dados de frequência de ocorrência e duração de cada comportamento. Com os dados construiu-se um etograma. Registrou-se 23 comportamentos divididos em cinco categorias: locomoção, manutenção, alimentação, social-agonista e reprodução. Identificaram-se três formas de vocalização distintas em sonoridade, duração e ocasião, o que sugere diferentes funções para cada uma. As análises comprovaram a variação da maior parte dos comportamentos ao longo dos meses do ano, tanto em frequência como em duração. Constatou-se o aumento dos comportamentos sociais-agonistas e reprodutivos durante a estação reprodutiva, enquanto outras categorias como alimentação e manutenção apresentaram diminuição nesse período, havendo maior empenho dos animais na proteção dos ninhos e filhotes. O trabalho permitiu a caracterização dos comportamentos de V. chilensis no sul do Brasil, auxiliando no entendimento das relações entre espécie e ambiente típico da região.(AU)

O guardião dos campos: um estudo sobre o comportamento do quero-quero Vanellus chilensis (Aves: Charadriiformes) no sul do Brasil / Guardian of the fields: a study on the behavior of the Southern Lapwing Vanellus chilensis (Aves: Charadriiformes) in Southern Brazil

The Southern Lapwing Vanellus chilensis (Molina, 1782) is a common bird in Rio Grande do Sul state, south Brazil, but is widely distributed across South America. It inhabits grasslands and other open habitats and it is known by a distinctive black, grey, and white coloration, a conspicuous vocalization and both aggressive and territorial behaviors. Although being recognized as the bird symbol of Rio Grande do Sul, no study about its behavior has yet been carried out in the state. Here, we aimed to describe and quantify the behavioral repertoire of Southern Lapwing. Between December of 2017 and November of 2018, we carried out observations in an eight-hectares grassland site in northern Rio Grande do Sul. We used ad libitum and animal focusing techniques to identify and record the frequency and duration of specific behaviors. An ethogram was elaborated, representing the 23 detected behaviors, grouped in five categories: locomotion, maintenance, feeding, socio-agonistic, and reproduction. Our analysis showed that most behaviors vary in both frequency and duration over the year. We detected high frequency and duration of social-agonistic and reproductive behaviors during the breeding season, while other categories, like feeding and maintenance, showed a decrease in the same period, with greater commitment to protect the eggs and chicks. We also recorded three types of vocalization with different characteristics, one of which occurs exclusively during the breeding season. The results of our study allowed the identification and quantification of V. chilensis in southern Brazil, thus helping in understanding the relations between the species and its habitats in the region.

O quero-quero Vanellus chilensis (Molina, 1782) é uma ave típica do Estado do Rio Grande do Sul, mas possui ampla distribuição geográfica nos campos da América do Sul, sendo conhecido pelo canto imponente e pelos comportamentos relacionados com a agressividade e a territorialidade. Apesar de ser reconhecido como animal símbolo do estado, nenhum trabalho acerca dos comportamentos dessa ave foi desenvolvido no estado. Este trabalho teve como objetivo qualificar e quantificar o repertório comportamental de V. chilensis. Observações dos comportamentos dessa ave foram feitas em uma área de campo com oito hectares, no município de Torres, RS, entre dezembro de 2017 e novembro de 2018, totalizando 143 horas de observação. Utilizou-se a metodologia de observação de todas as ocorrências e observação de animal focal, coletando-se dados de frequência de ocorrência e duração de cada comportamento. Com os dados construiu-se um etograma. Registrou-se 23 comportamentos divididos em cinco categorias: locomoção, manutenção, alimentação, social-agonista e reprodução. Identificaram-se três formas de vocalização distintas em sonoridade, duração e ocasião, o que sugere diferentes funções para cada uma. As análises comprovaram a variação da maior parte dos comportamentos ao longo dos meses do ano, tanto em frequência como em duração. Constatou-se o aumento dos comportamentos sociais-agonistas e reprodutivos durante a estação reprodutiva, enquanto outras categorias como alimentação e manutenção apresentaram diminuição nesse período, havendo maior empenho dos animais na proteção dos ninhos e filhotes. O trabalho permitiu a caracterização dos comportamentos de V. chilensis no sul do Brasil, auxiliando no entendimento das relações entre espécie e ambiente típico da região.

O guardião dos campos: um estudo sobre o comportamento do quero-quero Vanellus chilensis (Aves: Charadriiformes) no sul do Brasil

ABSTRACT The Southern Lapwing Vanellus chilensis (Molina, 1782) is a common bird in Rio Grande do Sul state, south Brazil, but is widely distributed across South America. It inhabits grasslands and other open habitats and it is known by a distinctive black, grey, and white coloration, a conspicuous vocalization and both aggressive and territorial behaviors. Although being recognized as the bird symbol of Rio Grande do Sul, no study about its behavior has yet been carried out in the state. Here, we aimed to describe and quantify the behavioral repertoire of Southern Lapwing. Between December of 2017 and November of 2018, we carried out observations in an eight-hectares grassland site in northern Rio Grande do Sul. We used ad libitum and animal focusing techniques to identify and record the frequency and duration of specific behaviors. An ethogram was elaborated, representing the 23 detected behaviors, grouped in five categories: locomotion, maintenance, feeding, socio-agonistic, and reproduction. Our analysis showed that most behaviors vary in both frequency and duration over the year. We detected high frequency and duration of social-agonistic and reproductive behaviors during the breeding season, while other categories, like feeding and maintenance, showed a decrease in the same period, with greater commitment to protect the eggs and chicks. We also recorded three types of vocalization with different characteristics, one of which occurs exclusively during the breeding season. The results of our study allowed the identification and quantification of V. chilensis in southern Brazil, thus helping in understanding the relations between the species and its habitats in the region.

RESUMO O quero-quero Vanellus chilensis (Molina, 1782) é uma ave típica do Estado do Rio Grande do Sul, mas possui ampla distribuição geográfica nos campos da América do Sul, sendo conhecido pelo canto imponente e pelos comportamentos relacionados com a agressividade e a territorialidade. Apesar de ser reconhecido como animal símbolo do estado, nenhum trabalho acerca dos comportamentos dessa ave foi desenvolvido no estado. Este trabalho teve como objetivo qualificar e quantificar o repertório comportamental de V. chilensis. Observações dos comportamentos dessa ave foram feitas em uma área de campo com oito hectares, no município de Torres, RS, entre dezembro de 2017 e novembro de 2018, totalizando 143 horas de observação. Utilizou-se a metodologia de observação de todas as ocorrências e observação de animal focal, coletando-se dados de frequência de ocorrência e duração de cada comportamento. Com os dados construiu-se um etograma. Registrou-se 23 comportamentos divididos em cinco categorias: locomoção, manutenção, alimentação, social-agonista e reprodução. Identificaram-se três formas de vocalização distintas em sonoridade, duração e ocasião, o que sugere diferentes funções para cada uma. As análises comprovaram a variação da maior parte dos comportamentos ao longo dos meses do ano, tanto em frequência como em duração. Constatou-se o aumento dos comportamentos sociais-agonistas e reprodutivos durante a estação reprodutiva, enquanto outras categorias como alimentação e manutenção apresentaram diminuição nesse período, havendo maior empenho dos animais na proteção dos ninhos e filhotes. O trabalho permitiu a caracterização dos comportamentos de V. chilensis no sul do Brasil, auxiliando no entendimento das relações entre espécie e ambiente típico da região.

Dietary L-tryptophan modulates agonistic behavior and brain serotonin in male dyadic contests of a cichlid fish.

Although some studies have investigated the effects of dietary L-tryptophan on agonistic behavior, research on adult fish specimens is still lacking. Moreover, submissive behaviors have been generally overlooked. We focused on agonistic behavior between males of the cichlid fish Cichlasoma dimerus, in dyadic encounters held in a novel context after being fed or not with an L-tryptophan enriched diet (TRP) for 2 weeks. We arranged three different dyads: control/control (control conditions: not TRP enriched), control/TRP, and TRP/TRP. We also registered the response of the brain serotonergic system in four brain regions. TRP/TRP dyads showed higher latencies to first attack, lower overall aggression, and lower proportions of bites and passive copings (submissive display) compared to control/control. TRP dominant males performed fewer bites with respect to controls, and subordinate males opposed to TRP males showed fewer passive copings. Higher serotonergic activities were found in subordinates' optic tectum and in the telencephalon and preoptic area/hypothalamus of TRP males. Altogether, results point out that dietary L-tryptophan reduced males' motivation to attack and dominant aggression, which consequently influenced subordinate agonistic repertory. In addition, males within TRP/TRP dyads showed a switch in their behavioral agonistic repertory. These behavioral outcomes were probably due to modifications at brain serotonergic functioning.

Interactions between Invasive Monk Parakeets (Myiopsitta monachus) and Other Bird Species during Nesting Seasons in Santiago, Chile.

The monk parakeet (Myiopsitta monachus) is considered to be one of the most invasive bird species because its unique ability among parrots to build their own communal nests. Currently, they are considered an invasive species in 19 countries and a pest-even in their native distribution-because of economic losses derived from their impacts. During the reproductive seasons of 2017 and 2018, we registered interactions between invasive monk parakeets and resident bird species in Santiago, Chile. We observed agonistic and affiliative interactions, and further, we described monk parakeets' nest occupancy by nine bird species, two invasive and seven native. For this reason, we consider that the monk parakeet is an allogenic ecosystem engineer with the potential to shape distribution and richness of sympatric species in urban environments. Our results contribute to an assessment of the implications of the monk parakeet's ecological invasion to other synanthropic species, and raise concern of other potential impacts, such as pathogen transmission derived from these interactions.

What do we need to know to recognize a contest?

Animals frequently use agonistic contests as a way to solve disputes over indivisible resources. Such agonistic contests often represent interactions between an owner and a non-owner of a resource. However, some behaviors adopted by rivals during agonistic interactions are similar to behaviors adopted in other types of interactions. Thus, the possibility exists that some interactions between individuals can be misinterpreted as actual agonistic contests. Herein, we synthesize information from prior studies that present interactions that may be confounded with actual agonistic contests. We also point potential problems when different types of confoundment occur and provide suggestions of how to distinguish between agonistic contests and alternative interactions. For this, we made a distinction between completely non-agonistic interactions and quasi-agonistic interactions (i.e., interactions in which at least one rival is not motivated to fight). We also show potential biases in the understanding of how rivals decide who is the winner of a contest for studies that consider non- or quasi-agonistic interactions as actual agonistic contests.

Distinctive mechanisms underlie the emission of social electric signals of submission in Gymnotus omarorum.

South American weakly electric fish (order Gymnotiformes) rely on a highly conserved and relatively fixed electromotor circuit to produce species-specific electric organ discharges (EODs) and a variety of meaningful adaptive EOD modulations. The command for each EOD arises from a medullary pacemaker nucleus composed of electrotonically coupled intrinsic pacemaker and bulbospinal projecting relay cells. During agonistic encounters, Gymnotus omarorum signals submission by interrupting its EOD (offs) and emitting transient high-rate barrages of low-amplitude discharges (chirps). Previous studies in Gymnotiformes have shown that electric signal diversity is based on the segregation of descending synaptic inputs to pacemaker or relay cells and differential activation of the neurotransmitter receptors -for glutamate or γ-aminobutyric acid (GABA) - of these cells. Therefore, we tested whether GABAergic and glutamatergic inputs to pacemaker nucleus neurons are involved in the emission of submissive electric signals in G. omarorum We found that GABA applied to pacemaker cells evokes EOD interruptions that closely resemble natural offs. Although in other species chirping is probably due to glutamatergic suprathreshold depolarization of relay cells, here, application of glutamate to these cells was unable to replicate the emission of this submissive signal. Nevertheless, chirp-like discharges were emitted after the enhancement of excitability of relay cells by blocking an IA-type potassium current and, in some cases, by application of vasotocin, a status-dependent modulator peptide of G. omarorum agonistic behavior. Modulation of the electrophysiological properties of pacemaker nucleus neurons in Gymnotiformes emerges as a novel putative mechanism endowing electromotor networks with higher functional versatility.

All by myself? Meta-analysis of animal contests shows stronger support for self than for mutual assessment models.

Since the 1970's, models based on evolutionary game theory, such as war of attrition (WOA), energetic war of attrition (E-WOA), cumulative assessment model (CAM) and sequential assessment model (SAM), have been widely applied to understand how animals settle contests. Despite the important theoretical advances provided by these models, empirical evidence indicates that rules adopted by animals to settle contests vary among species. This stimulated recent discussions about the generality and applicability of models of contest. A meta-analysis may be helpful to answer questions such as: (i) is there a common contest rule to settle contests; (ii) do contest characteristics, such as the occurrence of physical contact during the fight, influence the use of specific contest rules; and (iii) is there a phylogenetic signal behind contest rules? To answer these questions, we gathered information on the relationship between contest duration and traits linked to contestants' resource holding potential (RHP) for randomly paired rivals and RHP-matched rivals. We also gathered behavioural data about contest escalation and RHP asymmetry. In contests between randomly paired rivals, we found a positive relationship between contest duration and loser RHP but did not find any pattern for winners. We also found a low phylogenetic signal and a similar response for species that fight with and without physical contact. In RHP-matched rivals, we found a positive relationship between contest duration and the mean RHP of the pair. Finally, we found a negative relation between contest escalation and RHP asymmetry, even though it was more variable than the other results. Our results thus indicate that rivals settle contests following the rules predicted by WOA and E-WOA in most species. However, we also found inconsistencies between the behaviours exhibited during contests and the assumptions of WOA models in most species. We discuss additional (and relatively untested) theoretical possibilities that may be explored to resolve the existing inconsistencies.

Vasotocinergic control of agonistic behavior told by Neotropical fishes.

The hypothalamic neuropeptides of the vasopressin-oxytocin family (and their homologs for non-mammalian species) are key modulators of the Social Brain Network, acting via specific receptors reported in all the nuclei of this network. Different conclusive examples have proven the context-dependency actions of hypothalamic nonapeptides on social behavior in several vertebrate taxa. Teleost fishes provide endless possibilities of experimental model systems to explore the underlying mechanisms of nonapeptide actions on social behavior given that they are the most diverse group of vertebrates. Although it has been difficult to identify commonalities of nonapeptide actions across species, indisputable evidence in many teleost species have demonstrated a clear role of vasotocin in the modulation of aggressive and sexual behaviors. Though Neotropical South American fish contribute an important percentage of teleost diversity, most native species remain unexplored as model systems for the study of the neuroendocrine bases of social behavior. In this review, we will revise recent data on the two model systems of Neotropical fish, South American cichlids and weakly electric fish that have contributed to this issue.

Unusual effect of chemical communication on social aggression in juvenile cichlid fish Cichlasoma paranaense (Cichliformes: Cichlidae)

Some fish species are socially organized and show a social rank order which is achieved through aggressive interactions. After hierarchy is settled, such species communicate their ranks through several sensorial cues; this communication is adaptive because it reduces detrimental effects from physical contests. Cichlid fish are socially organized and signal their social ranks through visual, acoustic and chemical communication. The response to signaling may vary according to the species and environment; the knowledge of different species is fundamental to understand the evolutionary forces upon their social communication. We tested the effect of chemical signaling on social groups of juvenile cichlid Cichlasoma paranaense by renewing the water in the aquarium, a procedure that washes away chemical information and increases aggressive interactions in other cichlid species. Two treatments were designed: 50% and 0% water renewal. Aggressive interactions were video-recorded immediately before water renewal, 1min, 1h, 2h, and 24h after water renewal. The treatment with the water renewal did not increase aggressive interactions within the group. The 50% water renewal apparently reduced aggressive interactions in this species, indicating an interspecific difference on the aggressive response to chemical variation in the social environment.(AU)

Algumas espécies de peixes são organizadas socialmente e apresentam uma ordem de rank social que é alcançada por meio de interações agressivas. Após o estabelecimento da hierarquia, essas espécies comunicam seu rank por diversas pistas sensoriais, essa comunicação é adaptativa, pois reduz os efeitos prejudiciais das lutas físicas. Peixes ciclídeos são socialmente organizados e sinalizam o rank social por comunicação visual, acústica e química. A resposta à sinalização pode variar de acordo com a espécie e o ambiente; o conhecimento sobre diferentes espécies é necessário para entender as forças evolutivas sobre sua comunicação social. Nós testamos o efeito da sinalização química em grupos sociais de juvenis do ciclídeo Cichlasoma paranaense por meio da renovação de água do aquário, um procedimento que dilui informações químicas e aumenta a interação agressiva em outras espécies de ciclídeos. Dois tratamentos foram realizados: 50% e 0% de renovação da água. A interação agressiva foi registrada imediatamente antes da renovação da água, 1min, 1h, 2h e 24h após a renovação da água. O tratamento com renovação não aumenta as interações agressivas dentro do grupo. A renovação de 50% da água do aquário aparentemente diminui as interações agressivas nessa espécie, indicando uma diferença interespecífica na resposta agressiva a variação química no ambiente social.(AU)