Zur Genetik und biologischen Bedeutung des Aggressionsverhaltens von Poecilia sphenops (Pisces,Poeciliidae)

The aggressive behaviour of hybrids between an epigeous and a cave-dwelling form of the toothcarp Poecilia sphenops was investigated in order to test whether a genetically determined reduction of aggressive behaviour exists in the cave population. The scores for five different elements of this behaviour as well as for the duration of fights support this hypothesis and suggest that aggressive behaviour in Poecilia spbenops is controlled by a closely linked polygenic system. On the basis of laboratory and field investigations, to aggressive behaviour is attributed the function of giving large ♂♂ a reproductive advantage within the framework of a body-size dependent rank order. Small ♀♀ appear to counteract this onesided selective advantage through a special strategy of sexual behaviour.     

Size-dependent male mating behaviour and sexual harassment in a population of Atlantic mollies (Poecilia mexicana) from a sulphur creek

The Atlantic molly Poecilia mexicana inhabits a variety of habitats. In previous studies, small males from clear-water populations showed considerably more sexual behaviours than large males. Males from a sulphur creek, the El Azufre, or from a sulphur cave (cave molly) showed comparatively low sexual activity, and typical size-dependent mating behaviour was either absent or large males showed even more sexual behaviour than smaller ones. Sexually deprived cave molly males increased their sexual activity, but small males still did not show more sexual behaviour than large ones, suggesting that the genetic basis for typical size-dependent mating behaviour has been lost. Likely, the extreme abiotic conditions (hypoxia and toxic hydrogen sulphide) have selected against energetically costly behaviours. In this paper, we examined how El Azufre males would respond to sexual deprivation. We found these males to also increase their sexual activity after sexual deprivation but, unlike cave mollies, small males now showed more sexual behaviour than large ones, suggesting that the genetic basis for this behaviour is not lost in this population. Differences between populations may be due to the less harsh characteristics of El Azufre (e.g. less H₂S), resulting in weaker selection against energy-consuming behaviours. Furthermore, we tested for potential costs of male sexual harassment for females in terms of reduced feeding efficiency in the presence of a male, as was shown for P. mexicana from a clear-water population, but was not found in cave mollies or the El Azufre fish. Test females were either starved for 1 week to increase hunger levels or male sexual deprivation and female starvation were combined; however, we found no evidence for male sexual harassment even after these treatments. Our results parallel previous findings in the cave molly and suggest that El Azufre males have lost specific behavioural traits that cause sexual harassment.     

Behavioral responses of male lobsters to Ecdysones

Four ecdysones with molting hormone activity, β‐ecdysone, inokosterone, ponasterone A, and cyasterone were tested for their capacity to elicit behavioral responses, especially sexual responses in the male lobster (Homarus americanus). Of these ecdysones, only β‐ecdysone elicited a low key alerting response. However, no particular type of behavior, such as feeding, aggressive or sexual behavior could be observed. A role of β‐ecdysone as a crustacean sex pheromone is not supported by these experiments and the general validity of this notion is discussed.     

Male aggression,limited female choice and the ontogeny of mating behaviour in the flesh fly Sarcophaga crassipalpis

Previous work has shown that male flesh flies (Sarcophaga crassipalpis Macquart) exhibit an ontogeny of behaviour from eclosion through sexual maturity that includes extensive changes in the expression of aggressive, non‐aggressive interactive and non‐interactive behaviours. To determine how the presence of a female flesh fly influences the manifestation of these behaviours, male flesh flies of different ages post‐eclosion are paired with same‐age females and their behaviours are monitored in a simple arena during a 50‐min observation period. All flies are socially isolated until pairing. Although the levels of expression of aggressive and non‐aggressive interactive behaviours are depressed relative to previous findings in male‐opponent pairs, the ontogeny of aggression still occurs as indicated by a significant increase, with age, in the agonistic behaviour ‘hold’. Similar to male‐opponent pairs and individual males, the performance by males of the non‐interactive behaviours ‘walking’ and ‘standing’ diminishes, whereas ‘upside‐down’ increases with age. By contrast, ‘grooming’ shows a significant age‐related decline. No courtship behaviours are observed in the males, although the aggressive behaviour ‘hold’ is a significant transition to mating. Females show no obvious courtship or rejection behaviours, although the significant increase in ‘upside‐down’ with age could possibly be a behavioural gateway to mating. The results of this study indicate that extensive age‐related changes encompassing the entire behavioural repertoire are intrinsic to male flesh flies and persist under a variety of different social contexts.     

Sexual and Aggressive Behaviour in Species Hybrids of Poecilia mexicana and Poecilia velifera (Pisces,Poeciliidae)

The inheritance of sexual behaviour patterns was studied in species hybrids of Poecilia mexicana and Poecilia velifera. In addition, the aggressive behaviour and some morphological characters have been investigated and checked for a possible correlation between and within these three different traits studied. All the characters are inherited polygenically. The minimum genetic factors could be estimated only for some characters.     

Territorial behaviour in corn mice, <Emphasis Type="Italic">Calomys musculinus</Emphasis> (Muridae: Sigmodontinae), with regard to mating system

We studied territorial behaviour of Calomys musculinus, a promiscuous-polygynous species, in order to test the predictions that during the breeding period, home-range-owner females are more aggressive than home-range intruders and that males do not display territorial behaviour. At the core of the breeding season, we conducted 136 intrasexual and 66 intersexual encounters. The study was carried out in four 0.25-ha enclosures, each containing one independent population. We studied territorial behaviour utilising focal animal sampling to record behaviour. Encounters were conducted in a circular opaque arena (COA) near the home-range’s activity mathematical centre (AMC). Amicable behaviour was not observed in any of the 78 trials among females. The rates of aggressive and submissive behaviour per female–female encounters varied in relation to whether they were home-range owners or intruders, the former being aggressive, the latter submissive. So we could link these drives to the territorial behaviour of C. musculinus. This result fits well with the already known territoriality of C. musculinus during the breeding season. In contrast, the 58 intrasexual male encounters did not show direct aggressive interactions between them. The rates of the different behaviours between males did not vary in relation to whether they were home-range owners or intruders. In our study, which took place during the breeding period, C. musculinus males were nonterritorial, and they never exhibited aggressiveness towards females.     

Effects of testosterone propionate on the social behaviour of groups of male comestic ducklings Anas platyrhynchos L.

One-month old testosterone-injected ducklings were observed in groups of three males and their social behaviour compared to that of oil-injected control birds. Most elements of adult sexual behaviour and one pattern of aggressive behaviour (chest fight) occurred more frequently in the experimental animals. It was shown that the same hormonal treatment induces different behavioural responses in different animals. Unlike previous studies, no social displays were observed in the testosterone-injected ducklings. Possible explanations of this fact are discussed.     

Spawning behaviour of Allis shad Alosa alosa: new insights based on imaging sonar data

Spawning behaviour of Alosa alosa was observed by high resolution imaging sonar. Detected clouds of sexual products and micro bubbles served as a potential indicator of spawning activity. Peak spawning time was between 0130 and 0200 hours at night. Increasing detections over three consecutive nights were consistent with sounds of mating events (bulls) assessed in hearing surveys in parallel to the hydro acoustic detection. In 70% of the analysed mating events there were no additional A. alosa joining the event whilst 70% of the mating events showed one or two A. alosa leaving the cloud. In 31% of the analysed mating events, however, three or more A. alosa were leaving the clouds, indicating that matings are not restricted to a pair. Imaging sonar is suitable for monitoring spawning activity and behaviour of anadromous clupeids in their spawning habitats.     

The Effect of Social Environment on Male–Male Competition in Guppies (Poecilia reticulata)

We examined male–male competition in guppies (Poecilia reticulata) to test for evidence of hierarchy formation and any subsequent effects on male mating success by comparing the interactions of pairs of males that were siblings and life‐long tank mates with those of unrelated pairs that had never met. These pairs of males were first observed in the absence of a female; then a female was added to gauge the effects of the initial male–male interactions on male sexual behaviour. The unfamiliar/unrelated pairs engaged in significantly more aggressive interactions such as physical contacts, nipping and chasing than the familiar/related pairs. Based on several previous studies, we suggest that familiarity played a greater role than relatedness in the differences in behaviour that we observed. Our results suggest that, in some circumstances, more aggressive males may have more mating opportunities than less aggressive males. Our results also indicate that males adjust their aggressive and courtship behaviours to the perceived intensity of competition for mates, based on the number of mature males in their rearing tanks. We suggest that male–male competition for mating opportunities may play a more important role in the guppy mating system than previously thought.     

Etude de l'influence des facteurs visuels sur les comportements sexuels et agressifs de Mollienesia (Poecilia) velifera (Pisces,Poeciliidae)

One of the most striking features of cave fishes is their pronounced ocular regression. They are, however, perfectly adapted since they multiply and display the behaviour patterns which are biologically important in their surroundings. It is therefore of interest to study the relative role of visual factors in the corresponding behaviour patterns in related epigean species.Other authors have previously demonstrated the dominant role of chemical stimuli in the releasing of sexual behaviour patterns in M. sphenops, of which some forms are cavernicolous. In M. velifera and M. latipinna, on the contrary, visual factors seem more important. The releasers of the aggressive behaviour patterns of these three species seem to be predominantly visual. In the present study, the importance of visual factors has been verified experimentally in M. velifera by comparing the observed behavioural differences in experimentally blinded individuals and normal controls.The results of the pre-experimental phase show that there is no difference between these two groups before blinding, neither in the frequency of the patterns, nor in their numerical values.The results of the first experimental phase confirm the importance of visual releasers in the sexual behaviour patterns of M. velifera. Thus, sexual approaches, mouth—abdomen contacts and copulation attempts are totally absent in blinded pairs. Sexual motivation however is still present since the gonopodal flexions are equally frequent in both groups. On the other hand, it seems that aggressive behaviour patterns are maintained in blinded individuals but only when the partners are very close to each other or when an actual contact has taken place.The comparison of pairs in which only one of the partners is blinded (second experimental phase), as well as results of the first phase, suggest that experimental blinding does not cause hormonal changes liable to influence the observed patterns. In addition to this, the role of the ♀ in courtship has been specified. When a ♀ individual is intact and receptive, it will initiate courtship when it is placed in the company of an inactive blinded partner.     

Aggressive behaviour in Montagu’s harrier Circus pygargus during the courtship period

Aggressive behaviour of Montagu’s harrier was observed during the pre-laying period in the 1992–1995 seasons on the calcareous marshes of Chelm in Eastern Poland. In total, 435 flights performed by 24 pairs of individually marked harriers were analysed. All flights were performed in relation to the territory of defence. Males performed 61% of aggressive interactions while females performed 39%. Intraspecific and interspecific aggression comprising direct attacks (58%), escorts (13%), pursuits (28%) and “mirror behaviour” (1%) were described for the first time. Interspecific aggressive behaviour occurred only near territory boundaries. The main intruders were marsh harriers Circus aeruginosus breeding on the same marshes. Occasionally, harriers attacked curlews Numenius arquata, short-eared owls Asio flammeus, magpies Pica pica, hooded crows Corvus corone cornix, common buzzards Buteo buteo or hobbies Falco subbuteo. Four cases of communal mobbing were observed. Three to five males from the neighbourhood attacked the intruders together. Intraspecific aggressive behaviour was observed in the pair territory, near the boundary or at a distance of up to 100 m from the defended area. Aggressive interactions performed by both sexes were more frequent towards birds of the same sex. Females defended their territories more aggressively against females. Similarly, males were more aggressive against males. All cases of aggressive behaviour were observed near harrier territories. Aggressive relations between birds outside breeding territories or when foraging around marshes were not observed.     

Reproductive status effects of pair-housed male pigs on natural,agonistic and sexual behaviours

Boar rearing, which avoids pain and suffering caused by surgical castration, provides better performance, a greater deposition of muscle tissue and leaner carcasses and thus has beneficial effects on both animal welfare and the product. Some countries that do not slaughter boars must consider their boar taint and aggressive and sexual behaviours. Considering that pigs are housed in large groups, which may complicate the formation of social hierarchies and increase fighting and mounting behaviours, some studies have conducted research with reduced numbers of pigs per pen, but these behaviours continued to be observed. However, a study of the reproductive status of pair-housed male pigs has yet to be reported. The aim of this study was to determine whether the reproductive status of uncastrated, immunocastrated and surgically castrated pair-housed male pigs alters their natural, agonistic and sexual behaviours. A total of 48 male pigs from Agroceres PIC™ genetics were assigned to three groups: surgically castrated (barrows), immunocastrated and uncastrated (boars). Natural, aggressive and sexual behaviours of the pigs were assessed by direct observations during four periods of 12 h each (six, five and three weeks before slaughter and the slaughter week). The pigs were housed in pairs from the growing phase until slaughter. Animal behaviour was observed from the finishing phase to slaughter. Carcass lesions were assessed according to five different classes (one: no injury; two to five: severely injured). Overall, boars spent more time lying and less time eating and drinking than barrows. In total of all the periods (48 h), boars expressed more aggressive and sexual behaviours than barrows, whereas immunocastrated pigs displayed similar behaviours to boars, before and after the second vaccine dose. No differences in carcass lesions between treatments and no prevalence of carcasses with severe injuries were observed. In conclusion, the reproductive status of pair-housed male pigs did not change the natural behaviour of boars, immunocastrated pigs or barrows. The agonistic and sexual behaviours of boars and barrows remained unchanged. When housing pigs in pairs, immunocastrated pigs presented similar agonistic and sexual behaviours to boars before and after the second immunocastration vaccine dose. The use of pair-housed uncastrated male pigs has generated welfare benefits for these animals, as the number of carcasses with injuries did not differ from barrows and immunocastrated pigs.     

Male nest building but not display behaviour directly influences mating success in the polygynous Red Bishop,Euplectes orix

Previous studies of the highly polygynous and strikingly sexually dimorphic Red Bishop, Euplectes orix (Ploceinae, weaverbirds), have suggested random female settlement patterns and no correlates of male reproductive success except the number of nest frames (‘cock's nests’) built by the male. Although this confirms the central role of the nest in weaverbird courtship it also contrasts with demonstrated sexual selection on male morphology and behaviour in several closely related Euplectes species. Two major aspects of male sexual advertising have not been included in previous studies; display behaviour and territory size. In this study we use multivariate selection analysis, with the number of active nests in a territory as the fitness measure, to identify direct and indirect sexual selection on male sexual behaviour, territory size and nest building. In accor–dance with previous findings, mating success was not strongly skewed among the territorial males, and females appeared to settle randomly with respect to available nests. The number of cock𠀧s nest built was the only determinant of male breeding success, even when controlling for male display activity and territory size. We argue that, despite their conspicuous sexual dimorphism, females settle independently of both male or territory quality, and that variance in male reproductive success is a consequence of male–male competition.     

Effects of Female‐Female Aggression in a Sexual/Unisexual Species Complex

The maintenance of sexual reproduction is still a largely unresolved question in evolutionary biology, and one of the most puzzling aspects of this is the coexistence of sexual and asexual females. This often leads to widespread niche overlap, posing an interesting challenge to competitive exclusion theory. In this study, we investigate how the aggressive behaviors between females in a sexual/unisexual mating complex of mollies (Poecilia latipinna and P. formosa) differ, and the effects these behaviors have on both the performer and receiver of aggressive acts. We exposed females to five treatments: (1) alone (control); (2) a large and small sexual female; (3) a large sexual female and a small unisexual female; (4) a small sexual female and a large unisexual female; and (5) a large and small unisexual female. We found that P. formosa females were on average more aggressive over time when compared to their sexual hosts, P. latipinna. The females of P. formosa, however, incurred a higher cost of being aggressive. Large, aggressor females of this species had a lower body fat content than their conspecific recipients. By contrast, P. latipinna females showed no differentiation between aggressors and recipients. Here, we combine life history methodology and behavioral observations to show that female competition can in fact be quantitatively measured and that these aggressive behaviors are costly to perform. The adaptive value of this interspecies aggression is not yet completely understood, but sexual competition, access to resources, and position within the shoal are all possible functions.     

A Comparative Study of Agonistic Behaviour in Hairy-footed Gerbils (Genus Gerbillurus)

Intraspecific agonistic behaviour was investigated by means of staged encounters in Gerbillurus paeba paeba, G. p. exilis, G. tytonis, G. setzeri and G. vallinus. Four groups of behaviour were identified by motivational analysis: i.e. “exploratory and solitary”, “aggressive”, “submissive”, and “sexual” behaviour. Frequencies of acts and levels of interaction differed among species and sexes. Cluster analysis of behaviour data revealed three clusters which agree partially with the karyology and taxonomy of the genus. G. p. paeba and G. tytonis were very aggressive and highly active; female G. p. exilis and G. setzeri less so; while male G. p. exilis and G. vallinus were least aggressive and active, performing more contact-promoting behaviour than other species. A range of social types is exhibited from solitary (G. p. paeba and G. tytonis) through semi-tolerant (G. setzeri and female G. p. exilis) to tolerant (male G. p. exilis and G. vallinus).     

Entire male pigs in farrow-to-finish pens—Effects on animal welfare

Aggressive and sexual behaviour can hamper animal welfare in entire male pig production. The aim of the present study was to investigate if rearing entire male pigs in sibling groups (in farrow-to-finish pens) could reduce aggressive and sexual behaviour and thereby improve animal welfare in entire male pig production. Frequencies of aggressive and sexual behaviour among finishing pigs were recorded in three different groups in one herd; FTF-group (entires + gilts, siblings), mix-group (entires + gilts, mixed) and castrate-group (castrates + gilts, siblings). Frequencies of skin wounds were recorded in this herd and in an additional herd (only FTF-group and mix-group) shortly before the animals were sent to slaughter. Higher skin lesion scores in the entire male pig groups were in accordance with the behaviour data. Rearing entire male pigs in sibling groups reduces aggressive behaviour, though the frequency of the aggressive behaviour bouts was still higher than it was in the castrate-group. The frequency of skin wounds in the FTF-group was reduced to similar levels as in the castrate-group. The findings suggest that rearing entire males in sibling groups may be an appropriate management strategy for improving animal welfare in entire male pig production.     

Precocious Courtship and Play in Emydid Turtles

In many mammal species, precocious sexual behaviour is a component of play. A recent model for the evolution of play fighting behaviour in muroid rodents by Pellis (1993) proposes that social play in those species has its origin in precocious sexual behaviour. Captive juvenile emydid turtles perform precocious sexual behaviour. After reviewing its occurrence, we focus on detailed observations of Pseudemys nelsoni. Precocious sexual behaviour in these turtles is characterized by the striking ‘titillation’ display, usually observed only when adult males court females. In this display, the digits of the front feet are rapidly vibrated above the eyes of the female. In our observations, both sexes performed the display, which was energetic, spontaneous, and inconclusive (in that sequences of precocious courtship typically ended when either the displayer or recipient stopped and rested, left, or started some other unrelated non-social behaviour). Displaying individuals clearly preferred conspecific recipients and often appeared to seek out specific individuals. We discuss several plausible explanations for precocious courtship in these turtles but find none entirely satisfying. The characteristics of the precocious courtship behaviour we observed most closely match those commonly listed for social play. Thus, we conclude that the most likely explanation for this behaviour is that it is a component of social play.     

Sexual attractiveness shared by both sexes mediates same‐sex sexual behaviour in the parasitoid wasp Telenomus triptus

The mating behaviour of a quasi‐gregarious egg parasitoid Telenomus triptus Nixon (Hymenoptera: Platygastridae), which exploits egg masses of a stink bug Piezodorus hybneri (Heteroptera: Pentatomidae), is examined in the laboratory. In this parasitoid wasp, male adults that emerge earlier stay at the natal egg mass and mate with subsequently emerging females. In the present study, a male adult that encounters the emergence of another male always waits for it to egress, and then mounts the newly emerging male. To examine why males of T. triptus show same‐sex sexual behaviour, male adults are presented with a parasitized host egg mass or a freshly killed wasp. Male adults are observed to remain at host egg masses from which only male wasp(s) had emerged. In addition, male adults attempt to copulate with freshly killed young male wasps. It is suggested that newly emerging male wasps are targets of same‐sex sexual behaviour because they possess cues for male sexual behaviour similar to the cues of females. Both the sex and age of freshly killed wasps affect the frequency of the sexual behaviour of male adults: females are more attractive than males, although their attractiveness declines with age. When the mating opportunity is restricted to the natal egg mass, the costs of failing to notice newly emerging female adults should be extremely high. Therefore, males are forced not to discriminate the sex, resulting in same‐sex sexual behaviour.     

Lateralisation in agonistic encounters: do mirror tests reflect aggressive behaviour? A study on a West African cichlid

In this study, population level lateralisation and the suitability of mirror tests as a test of natural aggressive behaviour in male rainbow kribs Pelvicachromis pulcher was investigated. Aggressive behaviour in live agonistic trials correlated positively with behaviours towards a mirror image and no visual lateralisation was detected.