Effects of previous experience on the agonistic behaviour of male crickets, Gryllus bimaculatus

Male solitary animals frequently enter aggressive interactions with conspecific individuals to protect their territory or to gain access to females. After an agonistic encounter, the loser (subordinate individual) changes its behaviour from aggression to avoidance. We investigated agonistic interactions between pairs of male crickets to understand how dominance is established and maintained. Two na?ve males readily entered into agonistic interactions. Fights escalated in a stereotyped manner and were concluded with the establishment of dominance. If individuals were isolated after the first encounter and placed together 15 minutes later, subordinate crickets tended to avoid any further contact with the former dominant opponent. Moreover, subordinate males also avoided unfamiliar dominant and na?ve opponents. They displayed aggressive behaviour only towards unfamiliar subordinate opponents. This suggests that the subordinate male change their behaviour depending on the dominance status of the opponent. Dominant crickets, in contrast, displayed aggressive behaviour towards familiar as well as unfamiliar opponents. If the interval between the first and second encounter was longer than 30 minutes, the former subordinate male showed aggressive behaviour again. However, if the subordinate cricket was paired with the same opponent three consecutive times within 45 minutes, it avoided the former dominant opponent for up to 6 hours following the third encounter. Our results suggest that the maintenance of dominance in male crickets depends largely on the behavioural change of subordinate individuals. Possible mechanisms to maintain dominance are discussed.     

Mating behavior of cockerels: Effects of social status,group size and group density

Mating behavior was studied to reexamine the correlation between social status of cockerels and mating frequency. A moderate correlation of 0.30 (P < 0.025) was found between males-dominated and completed-matings-per-hour. This relationship was not as large as expected from the findings by Guhl and Warren (1946), but was closer to the results of Craig et al. (1977). Completed matings, aggressive acts and interferences increased relative to dominance categories in four combinations of group size and density. Males with more area had more (P < 0.05) courting, completed matings and aggressive acts, and smaller flocks showed more behavioral activity. Mating activities peaked between the second and third weeks after flock formation. Mating proficiency increased linearly over time and was adversely affected by interference until the fourth week.     

Social dominance in dairy cattle

The meaning of “social dominance” and the problems associated with its use are discussed. Most problems disappear if dominance is restricted to the phenomenon that in every pair of animals one member can inhibit the behaviour of the other. The dominance order of the group is the sum of all such inhibitory relationships. Dominant animals probably have been aggressive in the past to obtain their dominant positions, but a dominant animal need not be aggressive now. Measures of the dominance position of animals in a herd should be based on observations in the particular herd, contain sufficient observations to be reliable, reflect the actual magnitude of differences between animals, and be normally distributed. The method of Beilharz and Mylrea (1963) meets these requirements. The application of this method is discussed.The dominance structure of three dairy herds near Freiburg in South West Germany were studied. None of the herds had an individual cow who was dominant over all others in the herd. Parameters of social structure varied from herd to herd. The findings are discussed in relation to differences in space per animal, manner of recruitment of young stock to the herds, presence of horns and other features. It is concluded that the dominance relationship of any pair of animals is a result of learning, with many different factors, including trivial ones, being involved in the initial serious formation of the relationship. Once learnt, dominance relationships for each pair of animals persist for a long time. While bidirectional dominance relationships are found in young animals, where none has yet accepted dominance of others, mature animals of all species of domestic livestock generally have clear unidirectional dominance relationships. The dominance order of the group may be no more than the sum of the individual relationships. Dominant animals are freer than others in attending to stimuli from outside the herd.     

The relationship between the comb and social behaviour in laying hens

The question of whether attributes of the combs of laying hens have any consistent relationship with dominance behaviour has yet to be answered unequivocally. This study sought to address this by investigating whether a relationship existed between the competitive ability of hens within stable groups and the size or colour of their combs. Pullets (n = 120, Hy-line^® Variety Brown) were allocated randomly to eight groups of 15 hens for 32 weeks. Over this period the length and height of each hen's comb was measured regularly to estimate the total comb area and hens were weighed. In weeks 3-10 the aggressive interactions between hens in each group were observed to calculate a behavioural dominance score (David's score) for each hen. This score was based on the outcome of agonistic interactions with other group members; and accounts for the relative strengths of all opponents. Thus dominance scores reflected the competitive ability of hens from their overall within-group fighting success. The luminance, purity and dominant wavelength of the colour of each hen's comb was measured in week 27 using a telespectroradiometer. Hens with higher dominance scores had larger combs than those with lower dominance scores (gradient of slope = 0.008 ± 0.002, P < 0.001); this relationship was consistent across the experiment. There was no association between body weight and dominance score but there was a significant inverse relationship between dominance score and the dominant wavelength of the comb (gradient of slope = −0.067 ± 0.023, P < 0.01). This indicated that hens with combs perceived by humans as more yellow-red than pure red were generally more successful competitors. Further research is required to ascertain whether or not hens utilise this information on comb size and the underexplored area of comb colour to assess the competitive ability of their opponents.     

Social organization among young beef cattle in confinement

Social organization or dominance hierarchies were demonstrated among beef steers as young as 250 days of age. Two groups of five and seven crossbred beef steers were scored for agonistic encounters, and these data were used to determine dominant—subordinate relationships. The effects of removing and adding animals to groups were determined by mixing some members from the groups of five and adding new members to obtain the groups of seven. Weight was positively correlated (P< 0.05) with dominance value (0.55). There was evidence that the dominance orders were formed soon after weaning and that the orders remained stable even when the groups were moved to other pens.     

Polymorphisms of diacylglycerol acyltransferase 2 gene and their relationship with growth traits in goats

Diacylglycerol acyltransferase (DGAT) plays a critical role in the synthesis of triacylglycerol. In this study, PCR-SSCP and DNA sequencing methods were employed to screen the genetic variations of DGAT-2 gene in 299 goats from three breeds (Boer goat, Chinese Xuhuai white goat and Chinese Haimen goat). Three fragments of DGAT-2 gene were investigated, only exon 3 of DGAT-2 gene showed polymorphism. The alignment between nucleotide sequences of NM_205793.2 in GenBank and the sequencing results of three PCR products with different patterns revealed that there was one mutation (A????G) in exon 3 of DGAT-2 gene, which resulted in amino acid change (Lys????Arg) and constructed two genotypes (AA, AB). The frequencies of allele A and genotype AA were dominant in all three breeds. And there was no significant difference for genotypic and allelic frequencies among the three breeds. The genotype distributions were in good agreement with Hardy?CWeinberg equilibrium (P?>?0.05) in each breed. Significant statistical differences were only found in withers heights (P?<?0.05) in Xuhuai goat between genotypes. The results indicated that individuals with genotype AA were significantly higher than those of individuals with genotype AB in withers height (P?<?0.05). No polymorphism was detected in the intron 3, exon 8 and 3?? flanking region. So we suggested that DGAT-2 gene had the close relationship with growth traits in goats. And this mutation could be used as a perfect molecular marker for marker-assisted selection (MAS) in animal genetics and breeding.     

Can Individual Differences in History of Dominance Explain the Development of Linear Dominance Hierarchies?

Observed dominance hierarchies are often more linear than expected from randomly-formed dominance relationships, and in triads of animals attacks are distributed non-randomly. I hypothesize that an individual's history of dominance affects its probability of initiating aggressive interactions in the future and that individuals with winning records are more likely to initiate (winning begets initiating). Consistent with this hypothesis, evidence is presented that dominant individuals are more likely to attack than subordinate individuals. The winning begets initiating hypothesis may also explain why correlations between predicted dominance ranks (based on size, age etc.) and observed dominance ranks can be low: If the cost of engaging in and losing an interaction is high relative to the potential benefits of winning, then a large individual conditioned to be subordinate may refrain from contesting smaller, dominant individuals despite its actual competitive superiority.     

The influence of social factors on the use of shade by sheep

Individual differences in shading behaviour within a flock of sheep could be due to differences in thermoregulatory capabilities or to the influence of social factors. The possible influence of social factors on shade-use is examined in this paper.Two measures of dominance were made on 39 Merino wethers. These were based on the hierarchy determined by butting during feeding and on priority of access to limited feed. Leadership was also assessed while driving the sheep to a woolshed and as the sheep entered weighing scales. These behavioural traits were compared with leadership to shade and shade-use observed on 9 days during summer in a small pastureless enclosure containing natural shade. Maximum ambient temperature on these 9 days varied between 29.0 and 39.5°C.All behavioural traits examined were significantly repeatable. The two dominance ranks were negatively correlated (P<0.05). The butting hierarchy was correlated with shading behaviour; those sheep that butted the larger proportion of the flock were seen to shade for longer periods of time (P=0.05). This relationship became more significant as environmental temperature increased. Significant (P<0.05) differences in the amount of time each sheep spent shading were evident throughout the flock, but in particular seven individuals shaded much less than others. Shade-use increased in hot weather and was slightly more strongly correlated with radiation load than with air temperature. The non-shading leadership ranks were related neither to each other nor to the leadership to shade. However, the sheep that moved to shade first remained there longest (P<0.05). Reduced motivation to feed did not appear to explain early movement to shade.Few overtly aggressive or other interactions between animals were seen to be associated with movements to or within shade. Nonetheless, the results indicate that social forces do exert some influence on shade-use.     

The Maintenance of Stable Dominance Hierarchies and the Pattern of Aggression: Support for the Suppression Hypothesis

Three hypotheses have been proposed to explain the development and maintenance of dominance hierarchies. According to the first hypothesis the dominance hierarchy is a result of the animals fighting once at their first encounter and then using the outcome of that fight to determine the rank order. The second hypothesis proposes that a dominance hierarchy reflects the fighting ability of the individuals in the group at each moment and is therefore relatively fluid with individuals continuously fighting for position. A third hypothesis, the suppression hypothesis, states that the dominance hierarchy is based to a large extent on the outcome of the first fight between the individuals but the dominant animal in each pair continuously attacks the subdominant individuals to condition them to lose in future encounters. We studied six well‐established flocks containing six adult hens each (Gallus gallus domesticus). Five of the flocks had linear hierarchies. The aggression was significantly more often directed towards the next low‐ranking individual. There was a good correlation between rank and comb size (height × width), but no significant correlation between rank and weight, or rank and level of fluctuating asymmetry. There was no significant correlation between levels of aggression and similarity of comb size for individuals of neighboring ranks. Our results tentatively support the suppression hypothesis for the maintenance of dominance hierarchies in the domestic hen.     

Investigation of individual heterozygosity correlated to growth traits in Tongshan Black-boned goat

Ten single nucleotide polymorphisms were used for genotyping of 176 Tongshan Black-boned goats, which are Chinese indigenous goat colony for meat production. The average individual heterozygosity was 0.292. To assess the correlations between individual heterozygosity and growth in Tongshan Black-boned goat individuals, and the potential of using individual heterozygosity as an indicator of growth, the data of growth traits, including body weight, height at withers, body length, chest girth and cannon circumference, were collected. Significant correlations were observed between individual heterozygosity and body weight, height at withers, body length, heart girth, cannon circumference (P < 0.05). All the significant regression showed positive slope with R square values ranged from 0.0251 to 0.0368. These data suggests that individual heterozygosity is positively correlated with growth traits in Tongshan Black-boned goat individuals and associative overdominance may affect Tongshan Black-boned goat growth significantly. Therefore it is possible to use individual heterozygosity as an indicator of growth. Our results also provide a strong support to the overdominance hypothesis.     

Dominance hierarchies among communally held juvenile lobsters,Homarus americanus

An investigation was conducted to determine the time for establishment of dominance hierarchies, their stability, and their relationship to molting and death of cultured juvenile lobsters, Homarus americanus. Agonistic displays between communally held animals were monitored daily. Interactions between all possible pairs of animals within each group were used to determine formation of a dominance hierarchy. A decrease in the frequency of agonistic interactions was recorded after the first day of the experiment. A stable four‐rank hierarchy was established within 2–3 days. When the dominant animal was molting, the subordinates displayed aggressively toward all members of the group but remained submissive to the dominant. When the dominant animal died, stability was lost and aggressive interactions among subordinates established a new ranking. Molting subordinates were highly susceptible to injury and death. Loss of subordinates did not affect the ranking of individuals.     

An analysis of dyadic interactions of male Japanese monkeys (Macaca fuscata fuscata) in a cage-room observation

This is a laboratory observation (Home-cage and observation room) for individual and social behavior of four male Japanese monkeys. The monkeys were placed in a dyadic and trio situation with the purpose to investigate the relationships between aggressive and affinitive factors which regulated their social behaviour. Total amounts of attacks and receiving groom showed a consistent order for four monkeys through the pairwise conditions, which was presumed to indicate a dominance order. Grooming and mounting behavior, however, were influenced by the particular dyadic interactions, probably social attraction, rather than dominance order itself. The presence of the third animal facilitated such a social preference between animals positioned closely in the rank order as well as elicited aggression from the dominant animals.     

Female Japanese quail that ‘eavesdrop’ on fighting males prefer losers to winners

In a series of four experiments, we examined the relationship between male dominance and female preference in Japanese quail, Coturnix japonica. Female quail that had watched an aggressive interaction between a pair of males preferred the loser of an encounter to its winner. This superficially perverse female preference for losers may be explained by the strong correlation between the success of a male in aggressive interactions with other males and the frequency with which he engages in courtship behaviours that appear potentially injurious to females. By choosing to affiliate with less dominant male quail, female quail may lose direct and indirect benefits that would accrue from pairing with dominant males. However, they also avoid the cost of interacting with potentially harmful, more aggressive males.     

Hierarchical structure and the influence of individual attributes in the captive squirrel monkey (<Emphasis Type="Italic">Saimiri collinsi</Emphasis>)

The dominance structure of primate social groups varies widely. In addition to the groups’ composition, intrinsic attributes such as sex, body size and life experience are important factors that can affect hierarchical dominance relations. All primates are social animals, and the social environment has a direct influence on the physiological conditions of vital systems such as immunological, reproductive and cardiovascular systems. In this study, we analyze the hierarchical structure of Saimiri collinsi in captivity, including the hierarchical structure type, the influence of individual intrinsic characteristics (sex, age, weight and origin—born in captivity or in the wild) based on the prior-attributes model, the relation between agonistic behavior frequency and hierarchical position, and hierarchy steepness, which represents the dominance gradient. We found that the group order was characterized by a partial hierarchy: a dominance position could be occupied by more than one individual simultaneously, including individuals of both sexes. Intrinsic characteristics had no influence on hierarchical structure, with the exception of the male in the highest hierarchical position, which had a markedly larger body than all other group members. Thus, the prior-attributes model did not apply to hierarchical formation of S. collinsi in captivity. Only the frequency of agonistic behavior of males correlated with their hierarchical position, and they differed from all other group members in their more aggressive behavior. The steepness between adjacent positions along the dominance gradient was significant only between the dominant male and the next individual in the group, with a smooth gradient between the other positions in the rank. As the access to resources is directly related to hierarchical dominance, a smooth dominance gradient is to be expected in species that form very large groups, such as wild Saimiri populations.     

Hand-held lactate analyzer as a tool for the real-time measurement of physical fatigue before slaughter and pork quality prediction

The objectives of this study were to assess the relationship between blood lactate variation measured at the plant, and pork quality variation on a large sample size and under commercial preslaughter handling conditions. A total of 600 pigs were randomly chosen on arrival at a commercial slaughter plant and blood samples taken from the ear vein at unloading (UN), after lairage (LA), in the restrainer (RE; before stunning) and at exsanguination (EX) were analysed for lactate content using a Lactate Scout Analyzer (LSA). In order to have a large range of measures, pigs were distributed into two groups; one kept in lairage overnight (G1) and the other for 2 to 3 h (G2) before slaughter. Meat quality was assessed in the Longissimus thoracis (LT), Semimembranosus (SM) and Adductor (AD) muscles by measuring the pH 30 min postmortem (pH1) and at 24 h postmortem (pHu), the colour and the drip loss. Blood lactate levels did not differ between G1 and G2 (P>0.05). A reduced muscle lactate and glucose contents (P=0.02 and P=0.004, respectively) resulting in a lower (P<0.001) glycolytic potential (GP) was observed in the LT muscle of G1 pigs when compared with G2 loins. In the LT muscle of G1 pigs, the lower GP resulted in an increased pHu (r=−0.67; P<0.001), decreased drip loss (r=0.57; P<0.001) and darker colour (r=0.50; P<0.001) compared with G2. In both G1 and G2 pigs, the lower GP was correlated to higher pHu value in the SM and AD muscles (r=−0.73; P<0.001). The greatest correlation was observed in G2 between blood lactate levels at LA and pHu value of the SM and AD muscles (r=0.46 and r=0.44, respectively; P<0.001 for both muscles). The second greatest correlation was found between blood lactate levels at EX and pH1 value in the SM muscle in both groups (r=−0.37 and r=−0.41, respectively; P<0.001 for both groups). Based on the results of this study, it appears that blood lactate levels, as measured by the LSA, reliably reflect the physiological response of pigs to perimortem stress and may help explain the variation in pork quality.     

Factors influencing the priority of access to food and their effects on the carcass traits for Japanese Black (Wagyu) cattle

The factors influencing the priority of access to food and the effects of the priority of access to food on their carcass traits were analyzed for Japanese Black (Wagyu) cattle in a semi-intensive fattening production system. The records of 96 clinically healthy steers and heifers were analyzed. The calves at ∼3 to 4 months of age were allocated to pens with four animals per pen; all four animals in the same pen were of the same sex and of similar body size. The ranking of the animals’ priority of access to food (1^st, 2^nd, 3^rd and 4^th), which was determined by the farm manager, was used as an indicator of social dominance in the present study. Four models including sire line, maternal grandsire line and the difference in the animals’ birth dates as fixed effects were used to analyze factors influencing the priority of access to food. Ranking was represented by ordinal scores (highest=4, lowest=1) in Model 1, and the binary scores were assigned in Model 2 (highest=1; 2^nd, 3^rd and 4^th=0), Model 3 (1^st and 2^nd=1; 3^rd and 4^th=0) and Model 4 (1^st, 2^nd and 3^rd=1; lowest=0). The results showed that the difference in the animals’ birth dates had a significant effect on the establishment of the priority of access to food in Model 3 (P<0.05), suggesting that animals born earlier may become more dominant in the pen. The maternal grandsire line tended to affect the social rank score in Models 2 and 3 (P<0.10). Our results indicated that the maternal grandsire line may affect the temperament of calves through their mothers’ genetic performance and thereby more aggressive calves may be more dominant and have higher priority of access to food. On the other hand, there was a significant effect of the priority of access to food on beef marbling score (BMS; P<0.05), and the priority of access to food also tended to influence the carcass weight (P=0.09). The highest BMS was observed for animals with the first rank of the priority of access to food (P<0.05), and the higher-ranking animals had the tendency to be heavier carcass than the lower-ranking animals. Our findings emphasized the importance of information about the priority of access to food determined by farmers’ own observation on implementing best management practices in small-scaled semi-intensive beef cattle production systems.     

Piping as a display of dominance by wintering Oystercatchers Haematopus ostralegus

Although Oystercatchers Haematopus ostralegus wintering in the Exe Estuary performed the piping display in any type of aggressive encounter, it was predominantly observed in two contexts. ‘Solitary piping’ occurred when one individual piped without an obvious opponent being in the immediate vicinity. In ‘piping ceremonies’, two or more individuals piped at each other for prolonged periods at close distance. Prolonged contests over mussels were usually won by the individual that had initially started piping. The most aggressive and successful birds (the dominants), engaged most often in solitary piping and piping ceremonies, using up to 10% of their time this way. This suggests that the behaviour was associated with dominance rank. The hypothesis is that the two birds are likely to start piping if their relative status has not already been established, so that a quick end to a dispute over a mussel or feeding site is not achieved. A dominant individual performs solitary piping from a distance to suppress the aggressive activities of other birds within its feeding range. If this signal fails, the dominant may join the ceremony, explaining why three was the most frequent number of birds involved in piping ceremonies. The ‘butterfly’ flight, used mainly by apparently dominant birds as they arrived on the feeding grounds, may signal their high status to birds already there. The outcome of several piping ceremonies involving birds of known dominance was consistent with this explanation. The location of piping ceremonies involving only two birds (interpreted as piping ceremonies not joined by dominants) at the extremities of the feeding ranges of the most dominant individuals is also consistent with this hypothesis, because this is where their dominance would be expected to decline and would therefore be more likely to be contested. This explanation of piping and butterfly displays assumes that individuals can recognize other individuals or quickly assess their dominance. Since dominant individuals were attacked less often than subdominants and attacking birds were rebuffed less than would be expected if recognition did not occur, we suggest that some form of dominance or individual recognition did exist. The width of the white collar did not correlate with dominance, but the individual variations in this feature may enable birds to distinguish each other and thus learn their relative status. It is intriguing that the diplomatist posture, which is typically used to rebuff misguided attackers, seems almost designed to give the opponent a particularly clear view of the white collar.     

Being in the thick of things: context-dependent network centrality in a captive flock of American flamingos

We test the hypothesis that the relationship between networks resulting from unresolved agonistic interactions (URI) and social dominance was context-dependent in a captive group of American Flamingos (Phoenicopterus ruber ruber). URI formed networks that differed substantially from the dominance network and depended on the context in which the interactions occurred. Betweenness centrality in the URI network on the region (“the island”) where nesting took place was strongly correlated with dominance score. This correlation was particularly strong in the case of males, but, in both sexes, the dominant individual in a dyad was likely to have a higher betweenness centrality in the island URI. On the other hand, betweenness centrality in URI networks at the feeder did not show any relationship with dominance, but was associated with observed visits to the feeder. Thus, centrality in both the island URI network and the feeder URI network was associated with access to a resource over which individuals competed. Along with other results suggesting that non-dominance interactions may form social networks distinct from, but related to, dominance networks, our results support the hypothesis that relationships within animal social groups can be modeled as a series of distinct but inter-related networks.     

Effects of dominant microalgae species and bacterial quantity on shrimp production in the final culture season

The dominant microalgal species, quantity of heterotrophic bacteria and Vibrio in the intestines and gills of Litopenaeus vannamei (Pacific white shrimp), positive detection rate of white spot syndrome virus (WSSV), and water quality indices were investigated at the final culture stage (88th day in culture season). Correlation of microalgal community, bacteria quantity, and shrimp production were analyzed by statistical analysis methods. Every 10 days, probiotics were used in groups A, B, and C, consisting of Bacillus, photosynthetic bacteria (PSB), and equal parts Bacillus and PSB, respectively. The results showed that production (25597.33?±?928.46 kg ha^?1) and survival rate (77.06?±?9.00 %) was the highest in group C, but positive detection rate of WSSV was the lowest. The microalgal community of group C was significantly dominated by Chlorella pyrenoidosa, with an average density and dominance of (289.52?±?142.10)?×?10⁷ cells L^?1 and 0.878?±?0.161, respectively. The correlation analysis indicated a significant negative correlation between Cyanophyta dominance and shrimp production (P?<?0.05), while the relationship between production and Vibrio quantity was not significantly correlated (P?>?0.05). Accordingly, microalgal dominant species should be controlled as a key factor in the shrimp culture season; in particular, the dominance of Cyanophyta should be restricted to a low level. Meanwhile, the combined use of Bacillus and PSB probiotics was considered an effective solution to optimize microalgal communities and controlling the cell density of Cyanophyta.     

Responsiveness to “social” releasers in cattle. II. Relation between social status and responsiveness,and possible effect of previous familiarization with the test conditions

The data of two previous experiments, investigating the effects of social releasers in Friesian-Dutch heifers were analysed in order to verify whether the frequency of approach responses to models and calls of conspecifics was modified by pre-experimental factors. First, responsiveness was correlated to the social status of individuals; a social hierarchy was assessed on the basis of agonistic interactions recorded for a 2-month period prior to the experiments with models. A significant positive correlation was found between the total number of responses and the total number of escape-avoidance reactions to aggressive acts. The same result was found when individual ranks were assessed on a hierarchy re-presenting a dominance order established on the basis of the number of aggressive acts causing escape-avoidance reactions. In this case, also, animals with highest ranks presented a significantly higher number of responses to models than animals with lowest ranks. In our second experiment, a significant positive correlation was found between all criteria used to assess individual ranks in a hierarchy, while this result was not found necessarily in the first experiment.The other pre-experimental factor under consideration was a possible familiarization with the testing conditions (models/calls of conspecifics, handling, and other procedures); some of the group-members tested during the second experiment had already been tested in the first one, carried out a year before. Many results demonstrated that the frequency of responses to social releasers was significantly lower for the previously tested subjects than for the animals tested for the first time.