Behavioral reproductive isolation inDrosophila silvestris,D. heteroneura,and their F1 hybrids (Diptera: Drosophilidae)

We investigated the role that courtship and aggressive interactions may have for the maintenance of reproductive isolation betweenDrosophila silvestris andD. heteroneura. We examined the behavioral bases of reproductive isolation between the parental species and we examined the courtship success of each sex of both reciprocal F₁ hybrids when paired with the parental species. We found reduced copulation success among heterotypic parental pairs compared to homotypic pairs, which was primarily due to the lack of courtship initiation betweenD. silvestris males andD. heteroneura females. When hybrid males from both reciprocal crosses were paired with parental females their copulation successes were not significantly different from that of parental males. In contrast, hybrid females from both crosses had reduced copulation success withD. silvestris males, which in turn was primarily due to a reduced success of reaching later stages of courtship. The time spent in copulation by hybrid males was intermediate between the two parental males. We studied aggression by observing the interactions of males of heterotypic pairs, both between the parental species and between the hybrids and parental males. A lack of aggressive interactions betweenD. silvestris males andD. heteroneura males in addition to the lack of courtship suggests thatD. silvestris males do not respond toD. heteroneura individuals of either sex. Hybrid males were equally successful in winning fights with bothD. silvestris andD. heteroneura males. These results indicate that the behavioral isolation betweenD. silvestris andD. heteroneura may be largely a consequence of the earliest stages of interactions. The two species may differ either in activity levels or in morphological or chemical traits that are important for species and mate recognition. The relatively high copulation and aggressive success of hybrids indicates that sexual selection against hybrids alone is unlikely to be a sufficient force to reduce gene flow and maintain species distinctions.     

Giant otter alarm calls as potential mechanisms for individual discrimination and sexual selection

Acoustic variation can convey identity information, facilitate social interactions among individuals and may be useful in identifying sex and group affiliation of senders. Giant otters live in highly cohesive groups with exclusive territories along water bodies defended by the entire group by means of acoustic and chemical signals. Snorts are harsh alarm calls, emitted in threat contexts, which commonly elicit the cohesion and the alert behaviour of the members of the group. The aim of this study was to determine whether giant otter snorts have potential to be used for individual discrimination. We tested this hypothesis by verifying if the acoustic characteristics of snorts vary between two study areas, among social groups and individuals, and between males and females. Snort acoustic variables did not differ significantly among study areas, but varied significantly among groups, individuals and between sexes, with higher discrimination between sexes. The frequency of formants (F1–F5) and formant dispersion (DF) potentially allow identity coding among groups, individuals and sexes. The stronger sex discrimination of snorts may be related to information on body size carried by formant frequencies and dispersion, indicating acoustic sexual dimorphism in giant otters. Acoustic differences among groups and individuals are more likely learned, since we did not find evidence for a genetic signal encoded in the snort variables measured. We conclude that the snorts carry information that could be used for individual or group recognition.     

Effects of size and sex on the social organization of reef-associated hogfishes,Bodianus spp.

Synopsis Three species of wrasses (Labridae) were examined in the field to determine the relative importance of size and sex in structuring social organization. The Spanish hogfish, Bodianus rufus, was characterized by stable dominance hierarchies that were linearly organized according to sex and relative size. Males were the largest and most-dominant individuals within discrete social groups of females (harems) whose dominance increased with body size. Dominance rank also increased with body size among both males and females of the Mexican hogfish, B. diplotaenia. Most encounters occurred between the sexes and males were clearly dominant over females. The vieja, B. eclancheri, differed from the other congeners since social interactions were not strongly patterned by either relative body size or sex. Hogfish dominance relationships appear to develop according to the manner in which males compete for females, including the formation of harems in permanent territories with single-male pairspawns (B. rufus), defense of temporary reproductive territories with single-male pairspawns (B. diplotaenia) or maximizing sperm production in multi-male group spawns (B. eclancheri).     

A comparative study of litter size and sex composition in a large dataset of callitrichine monkeys

In many birds and mammals, the size and sex composition of litters can have important downstream effects for individual offspring. Primates are model organisms for questions of cooperation and conflict, but the factors shaping interactions among same‐age siblings have been less‐studied in primates because most species bear single young. However, callitrichines (marmosets, tamarins, and lion tamarins) frequently bear litters of two or more, thereby providing the opportunity to ask whether variation in the size and sex composition of litters affects development, survival, and reproduction. To investigate these questions, we compiled a large dataset of nine species of callitrichines (n = 27,080 individuals; Callithrix geoffroyi, Callithrix jacchus, Cebuella pygmaea, Saguinus imperator, Saguinus oedipus, Leontopithecus chrysomelas, Leontopithecus chrysopygus, Leontopithecus rosalia, and Callimico goeldii) from zoo and laboratory populations spanning 80 years (1938–2018). Through this comparative approach, we found several lines of evidence that litter size and sex composition may impact fitness. Singletons have higher survivorship than litter‐born peers and they significantly outperform litter‐born individuals on two measures of reproductive performance. Further, for some species, individuals born in a mixed‐sex litter outperform isosexually‐born individuals (i.e., those born in all‐male or all‐female litters), suggesting that same‐sex competition may limit reproductive performance. We also document several interesting demographic trends. All but one species (C. pygmaea) has a male‐biased birth sex ratio with higher survivorship from birth to sexual maturity among females (although this was significant in only two species). Isosexual litters occurred at the expected frequency (with one exception: C. pygmaea), unlike other animals, where isosexual litters are typically overrepresented. Taken together, our results indicate a modest negative effect of same‐age sibling competition on reproductive output in captive callitrichines. This study also serves to illustrate the value of zoo and laboratory records for biological inquiry.     

Cannibalism as an interacting phenotype: precannibalistic aggression is influenced by social partners in the endangered Socorro Isopod (Thermosphaeroma thermophilum)

Models for the evolution of cannibalism highlight the importance of asymmetries between individuals in initiating cannibalistic attacks. Studies may include measures of body size but typically group individuals into size/age classes or compare populations. Such broad comparisons may obscure the details of interactions that ultimately determine how socially contingent characteristics evolve. We propose that understanding cannibalism is facilitated by using an interacting phenotypes perspective that includes the influences of the phenotype of a social partner on the behaviour of a focal individual and focuses on variation in individual pairwise interactions. We investigated how relative body size, a composite trait between a focal individual and its social partner, and the sex of the partners influenced precannibalistic aggression in the endangered Socorro isopod, Thermosphaeroma thermophilum. We also investigated whether differences in mating interest among males and females influenced cannibalism in mixed sex pairs. We studied these questions in three populations that differ markedly in range of body size and opportunities for interactions among individuals. We found that relative body size influences the probability of and latency to attack. We observed differences in the likelihood of and latency to attack based on both an individual's sex and the sex of its partner but found no evidence of sexual conflict. The instigation of precannibalistic aggression in these isopods is therefore a property of both an individual and its social partner. Our results suggest that interacting phenotype models would be improved by incorporating a new conditional ψ, which describes the strength of a social partner's influence on focal behaviour.     

Bi-directional sex change and gonad structure in the gobiid fish <Emphasis Type="Italic">Trimma yanagitai</Emphasis>

Bi-directional sex change in the deep-water gobiid fish Trimma yanagitai was examined. The gonads of all individuals consisted of ovarian and testicular elements, and an accessory gonadal structure. In no gonads were both testicular and ovarian parts simultaneously active. Bi-directional sex changes occurred during the rearing experiments in aquaria under conditions of which there was co-existence of two males or plural females. The sex of individuals could be determined by their relative body size or social dominance: the largest individuals acting as male and the remainder as female.     

Anthropogenic injuries disrupt social associations of common bottlenose dolphins (Tursiops truncatus) in Sarasota Bay,Florida

Social connectivity is important for measuring the fitness of common bottlenose dolphins (Tursiops truncatus). While interactions in fission-fusion societies vary between individuals, studies show that repeated interactions enhance reproduction and foraging success. Injuries that potentially remove an individual from its association network may disrupt these interactions. Using data from the long-term resident dolphin community in Sarasota Bay, Florida, we investigated how anthropogenic injuries affect the dolphins' social associations by examining the differences before and after injury to individuals. We examined group size, strength, eigenvector centrality, clustering coefficient, and number of triangles and analyzed whether the animal's sex, age class, type of injury, or human intervention affected these values. We found that while group size did not change, injured dolphins had fewer preferred associates (HWI > 0.14) and were found in more fluid groups immediately after injury, but started returning to normal association levels after 2 years. This initial decrease in connectivity was not related to the age, sex, type of injury, or intervention. Despite the fluidity in individual associations, the strongest bonds remained stable, those between mothers and calves and those between male alliance partners. These findings provide some of the first information relating injuries and social networks for animals.     

Interindividual interactions of Molina’s hog-nosed skunksConepatus chinga in the Pampas grassland of Argentina

During one year, we radiotracked two female and two male Molina’s hog-nosed skunksConepatus chinga (Molina, 1782), a little studied mephitid, in the Pampas of central Argentina, to analyze the static and dynamic interactions between individuals. Mean home range overlap was large (44.5%), but males shared a smaller proportion of their home ranges than females. The average percentage of localizations in the overlap area (39.3%) indicates that these areas were not marginal sections of individual home ranges, but this value was greater for individuals of different genders than intrasexual dyads. The Coefficient of Spatial Association confirmed that the distances between individuals of different sexes were smaller than between animals of the same sex. During simultaneous locations, females were closer than males, but reciprocal distances between individuals varied over the time. These patterns are congruent with those described as typical for mustelids and mephitids. Our results confirm that an analysis of home range overlap should not be considered complete without the study of dynamic interactions among individuals and their temporal variations, which are necessary to overcome the limitations of spatial overlap analysis.     

Preliminary data on voluntary food sharing in brown capuchin monkeys

Spontaneous interactions over fruits and vegetables were observed in a captive group of Cebus apella. The group lacked fully grown males; 3 adult females dominated the remaining 11 individuals, most of which were adolescents and late juveniles. Apart from expressions of interest and unsuccessful attempts to claim food, interactions over food included two types of interindividual food transfer: forced claims (i.e., involuntary transfers) and peaceful sharing. These two categories represented 7.2% and 20.3% of 3,389 observed food interactions, respectively. Sharing of food was subdivided into four categories; the most frequent category was the collection of discarded food items from within reach of the possessor, and the least frequent was active giving of food items by the possessor. The voluntary nature of food transfers was further investigated in an experiment in which two monkeys were placed in adjacent cages with a wire-mesh partition between them. One subject received food; the other did not. Although this setup made it easy for possessors to prevent food transfers, sharing occurred in all 18 tests on different combinations of individuals. In 10 of the tests, possessors were observed to actively push food through the mesh partition to their partner. © 1993 Wiley-Liss, Inc.     

Affiliative and submissive communication in rhesus macaques

This study analyzed the occurrence of selected facial expressions, gestures, and postures, in relation to sex and rank of sender and receiver, context, and responses elicited in a large multi-male multi-female group of rhesus macaques (Macaca mulatta) living in captivity. The group was observed for 100 hr during the mating and the birth season. Data were collected with the behavior sampling method. The bared-teeth display and the hindquarter presentation were the most prominent signals in the rhesus submissive and affiliative repertoire. Both signals were primarily displayed in response to aggression and approaches; bared-teeth in response to approaches from the front, presentation in response to approaches from the rear. Lip-smack had a submissive component like baredteeth and presentation but was more likely to be displayed by approaching individuals and followed by affiliation than these behaviors. The distribution of hip-touch and mount was different from that of bared-teeth, presentation, and lip-smack, these behaviors mostly occurring between males, irrespective of their dominance rank. Other infrequent signals and behavioral sequences were limited to specific male-female and mother-infant interactions.     

Sex differences in intrasexual aggression among sex-role-reversed,cooperatively breeding cichlid fish <Emphasis Type="Italic">Julidochromis regani</Emphasis>

In sex-role-reversed species, females compete for resources (e.g., mates) more intensively than do males. However, it remains unclear whether these species exhibit sex differences in the intensity of aggressive behavior in the context of within-sex contests. Cichlid fish in the genus Julidochromis exhibit intraspecific variation in mating systems, ranging from monogamy to cooperative polyandry with sex-role reversal. In the study reported here, we observed aggressive interactions among three same-sex individuals in Julidochromis regani in the laboratory and tested whether inter-female aggression was more intense than inter-male aggression. Although difference in body size strongly determined the direction of aggression in fish, aggression by a smaller-sized individuals toward larger ones was occasionally observed. This type of aggression was common between individuals of a similar body size (≤5 mm) and occurred more frequently among females than males. In contrast, differences in body size and sex did not affect the frequency of aggression by larger-sized individuals against smaller ones. Bidirectional aggression (i.e., mouth fighting) occurred frequently when two individuals had similar body size, and there was no difference in its frequency between sexes. However, temporal analysis showed that females performed bidirectional aggression more persistently than males. These sex differences in the intensity of intrasexual aggression could be the behavioral mechanisms underpinning cooperative polyandry.     

Sociality in Callithrix penicillata: II. Individual Strategies During Intergroup Encounters

In social animals, intergroup interactions, whether through agonistic and competitive behaviors or affiliative ones, can influence important parameters such as home range, territory sizes, and access to resources, which may directly affect both female and male fitness. We studied the intergroup interaction patterns of a wild group of black-tufted-ear marmosets (Callithrix penicillata) in central Brazil. Agonistic interactions occurred at low frequencies during intergroup encounters. The marmosets directed agonistic interactions without physical aggression primarily against same-sex individuals, suggesting that male and female aggression patterns are shaped by their sexual interests. However, females of the focal group also directed agonistic behavior toward extragroup males that attempted copulation. The marmosets appeared to use intergroup encounters to gather information about possible partners and extragroup reproductive opportunities. Intergroup sexual interactions occurred mainly in the form of copulations or attempted copulations by all adults, with the exception of the dominant female. Our results suggest that a possible reproductive strategy used by males is to attempt fertilization of extragroup females. Adult males copulated with the same extragroup female during several opportunities, which suggests sperm competition or the establishment of social bonds with neighboring females.     

Social Interactions and Familiarity in a Communal Halictine Bee Lasioglossum (Chilalictus) hemichalceum

Social organization in Hymenoptera is quite variable, but most group-living species have a reproductive division of labor. Communal species, by definition, do not; all individuals work and all are reproductive. In order to understand the evolution and maintenance of such cooperative societies the essential first step is characterization of the behavioral interactions between individuals. In particular, it is important to investigate the influence of common group membership (familiarity) on these interactions. Circle-tube arenas were used to observe the interactions between 42 pairs of field-collected Lasioglossum (Chilalictus) hemichalceum females either from the same nest, from different nests but the same nest aggregation, or from different aggregations. Identical procedures were applied to 24 pairs of females from laboratory colonies. There was a striking lack of agonistic behavior with Lunging occurring in only 0.03% of all bouts, and C-Postures (threat behavior) in only 19% of bouts using field bees and 27 % of bouts using females held in the laboratory. Passing was virtually ubiquitous, occurring in 98 % of all bouts. None of these behavior patterns is significantly associated with the level of familiarity between females. The lack of agonistic behavior and the indiscriminate cooperative behavior (Passing) suggest that all conspecifics are accepted and are treated similarly. This is in contrast to previous studies of L. (Dialictus) zephyrum that demonstrated both kin recognition and nepotism. While Avoidance behavior was rare, significantly more was seen between bees taken from different nest aggregations. Trophallaxis Solicitation occurred in 13 bouts between field bees. While the proportion of bouts in which this occurred is not associated with familiarity, the number of solicitations per bout is greater between females from different nest aggregations. These minor but statistically significant differences suggest that L. hemichalceum females can discriminate between familiar and unfamiliar individuals. Therefore the proximate mechanism underlying universal acceptance of all conspecifics cannot be a lack of recognition cue expression or recognition cue perception. Rather, it is due to a lack of clearly preferential treatment toward familiar individuals. This suggests that some component of fitness is positively associated with group membership per se, or group size. The high levels of mutual tolerance suggest, as do other lines of evidence (Kukuk & Schwarz 1987), that communal societies are not intermediate between solitary and eusocial species.     

Physical interactions facilitate sex change in the protogynous orange-spotted grouper,Epinephelus coioides

Sex change in teleost fishes is commonly regulated by social factors. In species that exhibit protogynous sex change, such as the orange-spotted grouper Epinephelus coioides, when the dominant males are removed from the social group, the most dominant female initiates sex change. The aim of this study was to determine the regulatory mechanisms of socially controlled sex change in E. coioides. We investigated the seasonal variation in social behaviours and sex change throughout the reproductive cycle of E. coioides, and defined the behaviour pattern of this fish during the establishment of a dominance hierarchy. The social behaviours and sex change in this fish were affected by season, and only occurred during the prebreeding season and breeding season. Therefore, a series of sensory isolation experiments was conducted during the breeding season to determine the role of physical, visual and olfactory cues in mediating socially controlled sex change. The results demonstrated that physical interactions between individuals in the social groups were crucial for the initiation and completion of sex change, whereas visual and olfactory cues alone were insufficient in stimulating sex change in dominant females. In addition, we propose that the steroid hormones 11-ketotestosterone and cortisol are involved in regulating the initiation of socially controlled sex change.     

Effect of host density on offspring sex ratios and behavioral interactions between females in the parasitoid waspNasonia vitripennis (Hymenoptera: Pteromalidae)

Pairs of females of the parasitoid waspNasonia vitripennis were videotaped with one or two hosts. The presence of an additional host decreased the number of interactions between females but had no measured effect on the nature of the interactions, i.e., on whether the interaction involved physical contact or occurred while one of the females was parasitizing a host. The number of hosts did not itself affect offspring sex ratios but did influence which other factors were correlated with sex ratio. When there was one host, the proportion of sons was more positively correlated with utilization of previously drilled holes than with female-female interactions, whereas when there were two hosts, the reverse was true. Parasitizing an already parasitized host appeared to affect a female's sex ratio beyond any effects of the physical presence of another female: When two hosts were present, the proportion of sons was greater from hosts parasitized by both females than from hosts parasitized by only one female. The observation that parasitizations in previously drilled holes and female-female interactions are correlated with sex ratios is consistent with previous studies; however, that these relationships are host density dependent is a new result and remains unexplained.     

Smoking–gender interaction and risk for rheumatoid arthritis

The present case–control study was conducted to investigate the relationship between smoking and rheumatoid arthritis, and to investigate formally the interaction between sex, smoking, and risk for developing rheumatoid arthritis. The study was performed in the Central District of Finland. Cases were patients with rheumatoid arthritis and the control group was a random sample of the general population. Logistic regression models were used to evaluate the effect of smoking on risk for rheumatoid arthritis, after adjusting for the effects of age, education, body mass index, and indices of general health and pain. Overall, 1095 patients with rheumatoid arthritis and 1530 control individuals were included. Patients were older, less well educated, more disabled, and had poorer levels of general health as compared with control individuals (all P < 0.01). Preliminary analyses revealed the presence of substantial statistical interaction between smoking and sex (P < 0.001). In separate multivariable analyses, past history of smoking was associated with increased risk for rheumatoid arthritis overall in men (odds ratio 2.0, 95% confidence interval 1.2–3.2) but not in women. Among men, this effect was seen only for rheumatoid factor-positive rheumatoid arthritis. There were significant interactions between smoking and age among women but not among men. We conclude that sex is a biologic effect modifier in the association between smoking and rheumatoid arthritis. The role of menopause in the etiology of rheumatoid arthritis merits further research.     

Context and Development of Sexual Behavior of Wild Bonobos (Pan paniscus) at Wamba, Zaire

I studied sexual behavior of immature bonobos (Pan paniscus) in a wild group living at Wamba, Zaire, with special reference to its development. Even immature individuals under 1 year old performed sexual behavior. Sexual behavior occurred in almost all age–sex combinations, except between immature and mature females. Based on analyses of behavioral pattern and context, I classified sexual behavior involving immature individuals into three categories. (1) Genital contact between immature individuals was observed during play, and was performed by males more frequently than by females. This sexual behavior shared many traits with that of other great apes. (2) Copulation-like genital contact was observed between immature males and mature females. Its frequency increased with the immature male's age; it developed into copulation in adulthood. (3) Genital contact used to regulate interindividual relationships. This behavior, which is unique to bonobos, was absent among infants. It developed between late juvenile and early adolescent periods in association with changes in social circumstances.     

陕西米仓山国家级自然保护区猕猴的分布及种群数量调查

2013年8至12月,对陕西省米仓山国家级自然保护区境内野生猕猴的种群数量及其社会结构进行调查,并估测该物种栖息环境的偏好性。通过在预先选取的样区域内采用"V"型路线调查法调查,发现该区域生活12群,共有460—500只野生猕猴。结合对其中5个猴群长时间的持续跟踪观察,统计得出成年个体占45.93%,未成年个体占34.45%,幼仔占19.61%,成年与未成年比例为1.33,成年雄雌的比例为0.36。并证实猕猴倾向于选择海拔700—1600m裸露的悬崖峭壁、平缓山坡农田带上缘、灌丛-森林带和半山中部及以上区域的阔叶林带下缘活动。     

Recognition of social relationships in bridging behavior among Tibetan macaques (Macaca thibetana)

Bridging behavior among male Tibetan macaques (Macaca thibetana) was studied in a free-ranging group at Mt. Huangshan, China. This behavior was defined as a type of affiliative behavior in which two individuals simultaneously lifted up one infant. Bridging behavior occurred after an adult male carried an infant to another male or approached another male who was holding an infant. Each male frequently held and groomed a particular infant in the group, which was named an “affiliated” infant of the male. Males were more frequently provided with their affiliated infant by other males than with other non-affiliated infants. This finding suggests that male Tibetan macaques recognized the affiliative relationship between a male and his affiliated infant, and chose that infant for bridging behavior on the basis of this knowledge. Such choice might be important for effective bridging behavior or other affiliative interactions between males. © 1995 Wiley-Liss, Inc.