Effects of Pair-Bond and Social Context on Male–Female Interactions in Captive Titi Monkeys (Callicebus moloch, Primates: Cebidae)

In monogamous species, an abiding relationship between a specific adult male and a specific adult female is a defining feature of the social system. The interactions between these individuals are influenced by many factors, including not only the history of their relationship (for example, development of a mutual bond), but also the immediate effects of the prevailing social context (for example, presence and sex of extra‐pair conspecifics). In this study we examined the effects of an existing bond and of social context on interactions between adult heterosexual pairs of the monogamous titi monkeys (Callicebus moloch). Twelve adult males and 12 adult females were tested with their cagemates and with an unfamiliar partner of the opposite sex in five social contexts: (1) mated male–female pair; (2) unfamiliar pair; (3) single female; (4) single male; and (5) empty stimulus cage. Results show that mated pairs were more affiliative than unfamiliar pairs and differentiated social contexts more sharply. Males were more responsive to context than females. Distance between mates was less and physical contact was more frequent in the presence of male–female pairs or a single male, than in the presence of a single female or an empty cage. These findings suggest that the presence and sex of strangers have a stronger influence on male–female interactions when the pair has an existing relationship.     

Etude des interactions sociales entre male et femelle chez la Genette (Genetta genetta L.): Relations entre marquage olfactif et agression

Study on Social Interactions between Male and Female Genets (Genetta genetta L.): Relations between Scent Marking and Aggression The aim of this work was to study the relations between marking behaviour and aggression in genets (Genetta genetta L.). Observations on social interactions were made on a socially stable pair and during encounters between unfamiliar pairs. In the first case, there appeared to be a relationship between marking activity in the male and aggression. During aggression periods, marking with the ano-urogenital region increased in the male and decreased in the female. Another striking variation concerned flank rubbing and hindleg rubbing. In both male and female these marking frequencies increased significantly during aggression periods and flank rubbing was modified by visual cues. Data recorded during encounters between unfamiliar pairs (one male being introduced in a female's cage) showed that agonistic behaviours were released through visual cues in females and olfactory cues in males. The same changes in marking frequencies were observed. These results also showed that ano-urogenital marking was inhibited in females during aggression periods. The adaptative significance of these phenomena is discussed.     

Behavioral and cardiophysiological responses of common marmosets (Callithrix jacchus) to social and environmental changes

Under captive conditions common marmosets (Callithrix jacchus) show socially monogamous propensities. Male and female form a social bond as characterized by signs of behavioral arousal during separation of the pairmates, high levels of affiliative interactions between pairmates and agonistic responses towards strange conspecifics. In the present study behavioral and cardiophysiological responses of mated individuals of common marmosets were recorded while the animals were in an unfamiliar environment (1) alone, (2) with the pairmate, or (3) with an opposite-sexed stranger. Pairmates of 6 established pairs were tested in 3 replicates yielding a total of 36 trials per experiment. A trial was divided into three 10-min segments (baseline; unfamiliar environment; reunion). Behavioral responses were videotaped with a remote controlled camera system installed within the cage. Systolic (SBP) and diastolic blood pressure (DBP), and heart rate (HR) as well as locomotor activity (ACT) were recorded telemtrically through peritoneally implanted transmitters. The individuals’ responses measured while in an unfamiliar environment was only reduced by the pairmate, but not by an opposite-sexed stranger. No affiliative behaviors occurred between strange conspecifics, whereas aggressive and sexual behaviors were observed. During reunion with the pairmate individuals recovered physiologically. The present study shows that an individualized pair bond exists between pairmates of common marmosets. Further, it becomes evident that establishing a social bond with the pairmate is important for maintaining physiological homeostasis.     

Pairing context determines condition-dependence of song rate in a monogamous passerine bird

Condition-dependence of male ornaments is thought to provide honest signals on which females can base their sexual choice for genetic quality. Recent studies show that condition-dependence patterns can vary within populations. Although long-term association is thought to promote honest signalling, no study has explored the influence of pairing context on the condition-dependence of male ornaments. In this study, we assessed the influence of natural variation in body condition on song rate in zebra finches (Taeniopygia guttata) in three different situations: during short and long encounters with an unfamiliar female, and within heterosexual mated pairs. We found consistent individual differences in male directed and undirected song rate. Moreover, body condition had a positive effect on song rate in paired males. However, male song rate was not influenced by body condition during short or long encounters with unfamiliar females. Song rate appears to be an unreliable signal of condition to prospective females as even poor-condition birds can cheat and sing at a high rate. By contrast, paired females can reliably use song rate to assess their mate''s body condition, and possibly the genetic quality. We propose that species'' characteristics, such as mating system, should be systematically taken into account to generate relevant hypotheses about the evolution of condition-dependent male ornaments.     

Close Proximity of the Heterosexual Partner Reduces the Physiological and Behavioral Consequences of Novel-Cage Housing in Black Tufted-Ear Marmosets (Callithrix kuhli)

The present studies assessed the extent to which heterosexual pairmates could buffer marmosets (Wied's black tufted-ear marmoset,Callithrix kuhli)against stress. Six male and six female marmosets from established groups were exposed to two experimental manipulations together with a control condition. Each condition lasted a total of 4 days. For the two experimental conditions, animals were removed from the family group and housed in a novel cage for 48 h in either the presence or the absence of the heterosexual pairmate. During the 48-h novel-cage housing period and for 48 h upon reunion of the subjects with the family group, concentrations of urinary cortisol were measured in the first void sample of the day and behavioral observations were conducted. When animals were housed alone in a novel cage they exhibited significant elevations in levels of urinary cortisol after 24 and 48 h of novel-cage exposure. In contrast, when marmosets were housed in the novel cage in the presence of the pairmate, levels of urinary cortisol did not change across the 4-day period. The presence of the social partner also reduced the behavioral manifestations of exposure to novelty. Upon reunion with the family group, animals that had been housed in the novel cage alone spent significantly more time in close proximity to the pairmate than animals that had been housed with the partner. A second experiment was conducted to determine the effect that separation from the pairmate, only (independent of any effects of novelty), had on levels of cortisol. Concentrations of urinary cortisol were measured in subjects housed in the familiar home cage, but in the absence of the pairmate, over a 48-h period and compared to concentrations of excreted cortisol immediately prior to separation. Separation from the pairmate did not elevate cortisol levels when the subject was housed in the home cage, suggesting that elevated cortisol levels in animals housed alone in the novel cage were in response to novelty exposure rather than to separation from the pairmate. Since the physical presence of the heterosexual partner reduced the physiological and behavioral effects of novel-cage housing, social attachments might function as homeostatic regulators of HPA function in marmosets.     

Social facilitation of agonistic responses to strangers in pairs of saddle back tamarins (Saguinus fuscicollis)

The effect of the presence of a familiar social partner on the interactions of saddle back tamarins with unfamiliar conspecifics was studied. Fifteen adult male-female pairs, of which six were composed of a castrated male and an intact female, served as subjects. All subject pairs were given two social encounters during which both mates met a strange male and two encounters during which they met a strange female. In addition, all subjects were given four encounters during which they met the same strangers while their own pair mates were absent. As a group, the subjects showed higher intensities of injurious aggression and of agonistic displays when they met strangers in the presence of their own pair mates. Females and castrated males, as subgroups, showed significant increases in most agonistic responses when they met strangers in the presence of their pair mates. Intact males, however, did not.     

Testing multiple hypotheses for the maintenance of male homosexual copulatory behaviour in flour beetles

Diverse animal groups exhibit homosexual interactions, yet the evolutionary maintenance of such behaviours remains enigmatic as they do not directly increase reproductive success by generating progeny. Here, we use Tribolium castaneum flour beetles, which exhibit frequent male homosexual copulations, to empirically test several hypotheses for the maintenance of such behaviours: (1) establishing social dominance; (2) practice for future heterosexual encounters; and (3) indirect sperm translocation. We found no evidence that Tribolium males use homosexual copulations either to establish dominance or to practice behaviours that increase their subsequent heterosexual reproductive performance. Our results provide limited support for the hypothesis of indirect sperm translocation: when males from two genetic strains mated with females immediately following a homosexual copulation, females produced progeny sired not only by the directly mating male, but also by that male’s homosexual partner. However, this phenomenon was detected in only 7% of homosexual pairs, and in each case such indirectly sired progeny accounted for < 0.5% of females’ total progeny. Direct observations indicated that mounting males often released spermatophores during homosexual copulations. These observations suggest that homosexual copulations may be a behavioural mechanism that allows males to expel older, potentially low‐quality sperm. Additional work is needed to test this new hypothesis, and to determine whether sperm release during homosexual copulations occurs in other groups.     

Chemosensory cues allow male Tenebrio molitor beetles to assess the reproductive status of potential mates

Males of many insect species, including beetles, choose their mates according to their reproductive status. However, the ways in which male beetles evaluate female reproductive status have received little attention. We tested the existence of male mate choice in the mealworm beetle, Tenebrio molitor, by observing mating and courtship behaviour of males given simultaneous access to pairs of females differing in their reproductive status: (1) mature versus immature; (2) virgin versus previously mated; (3) familiar (mated with the experimental male) versus unfamiliar (mated with a different male). Males courted and mated preferentially with mature and virgin females. To determine whether chemical cues played a role in these discriminations, we exposed males to filter paper squares bearing chemical cues from different types of females: (1) virgin versus mated; (2) mature versus immature. Males were significantly more attracted to those squares bearing chemical cues from virgin and mature females, suggesting that males can assess female reproductive status on the basis of chemical cues alone.     

Kin recognition and adjustment of reproductive effort in zebra finches

The differential allocation theory predicts that females should invest more in offspring produced with attractive partners, and a number of studies support this prediction in birds. Females have been shown to increase reproductive investment when mated to males showing elaborated sexual traits. However, mate attractiveness might also depend on the interaction between male and female genotypes. Accordingly, females should invest more in offspring sired by individuals that are genetically dissimilar or carry superior alleles. Here, we show in zebra finches (Taeniopygia guttata) that pairs of unfamiliar genetic brothers and sisters are less likely to reproduce in comparison with randomly mated pairs. Among the brother–sister pairs, those that attempted to breed laid smaller clutches and of lower total clutch mass. Our results provide the first experimental evidence that females adjust their reproductive effort in response to the genetic similarity of their partners. Importantly, these results imply a female ability to assess relatedness of a social mate without prior association.     

The behavior of the callitrichid monkey,Saguinus labiatus labiatus,in the laboratory

Observations of several aspects of the behavior of the tamarin Saguinus labiatus labiatusin the laboratory are presented. Some patterns of the behavioral repertoire emphasize areas of contrasting pelage;the leg standaccompanied by piloerectiondisplays the orange coloration of the ventrum. Several facial expressions (possibly rare in other species of callitrichid) emphasize the contrast between the white circumbuccal area and the black face. The behavior of three mated pairs was compared. Agonistic and sexual behaviors were rare. Males allogroomed their mates more than females did. Females performed the most scent marking. In two of the three pairs, one animal (the male in one case, the female in the other) determined the amount of contact and proximity between the mates. Experimental introductions of unfamiliar tamarins resulted in small amounts of both amicable and agonistic behavior. The tendency of adults to attack familiar same-sex conspecifics, reported in other callitrichids, was not evident in these experiments, although the presence of the mate stimulated social interaction between unfamiliar tamarins.     

Developmental changes in responsiveness to parents and unfamiliar adults in a monogamous monkey (Callicebus moloch)

Titi monkeys (Callicebus moloch) are monogamous New World primates that are characteristically found in family-type groups consisting of a mated adult pair and one or two young. The factors maintaining the small size of these groups are not known. Based on observations of free-ranging and captive families, parental aggression toward older offspring seems unlikely to play a significant role. Maturing individuals themselves, however, could undergo behavioral changes that weaken ties to their natal group. These might include waning of affiliative relations with parents, or subtle forms of aversion. Independent of such changes, increasing interest in unfamiliar conspecifics could be a factor. We examined these possibilities in the present study by assessing changes in social behavior and social preferences from initial ambulatory independence (6 months) through reproductive maturity (24 months) in a combined cross-sectional/longitudinal study of 21 captive titi monkeys living with their parents. Responses to both parents and to an unfamiliar adult heterosexual pair, a single unfamiliar adult male, and a single unfamiliar adult female were observed when subjects were given a choice between parents and strangers presented simultaneously or as the only social incentive. Social stimuli were at opposite ends of a 16.8-m-long test corridor. Subjects could move freely about the corridor for 5 min with each configuration of social stimuli. They stayed closer to parents than to strangers at all ages. Responsiveness to strangers increased with age and suggested growing ambivalence, particularly toward the male stranger. As they approached 24 months of age, male subjects showed a dramatic increase in the frequency and intensity of agonistic behaviors toward male strangers, behaviors that were rarely directed toward female strangers or parents. Waning of attraction to parents may be less important in dispersal from the natal group than changing reactions to strangers.     

Behavioral and cardiophysiological responses of common marmosets (<Emphasis Type="Italic">Callithrix jacchus</Emphasis>) to confrontations with opposite-sexed strangers

Common marmosets exhibit under captive conditions socially monogamous propensities. During confrontation with opposite-sexed stranger, in the presence of the pairmate, common marmosets often respond aggressively. However, in the absence of their mates, males actively solicit contact and even sexual interactions with strange females whereas mated females are indifferent to strange males. In the present study behavioral and cardiophysiological responses of pairmates of six established pairs of common marmosets were recorded during confrontation with an opposite-sexed stranger (1) in the presence or (2) in the absence of the familiar pairmate. Systolic and diastolic blood pressure, heart rate as well as locomotor activity were recorded telemetrically through peritoneally implanted transmitters. Behavioral responses were videotaped and in addition, urine samples from the female individuals were analyzed for their estrogen concentrations to monitor their ovarian cycles. The cardiophysiological values did not differ significantly between the two confrontation conditions. However, compared to baseline, heart rate values of both sexes and in males also blood pressure values, were significantly higher during confrontations. Hence, confrontations with an opposite-sexed conspecific clearly affect cardiophysiological parameters. Between confrontees affiliative behaviors could not been recorded but aggressive and sexual behaviors occurred.     

Sexual behaviour and its olfactory control in the desert woodrat (Neotoma lepida lepida)

In studies 1 and 2 nine pairs of desert woodrats (Neotoma lepida lepida) were observed for copulatory behaviour when the female was in a state of naturally occurring oestrus (study 1) and following ovariectomy and oestrogen and progesterone replacement (study 2). Males and females respond in a similar way under conditions of natural and hormone-induced oestrus. Males show a consummatory pattern involving multiple mounts and ejaculations, with ejaculations occurring after single intromissions. Females show the lordosis reflex accompanied by hop-and-dart and ear-wiggling responses. In addition, both sexes show appetitive precopulatory behaviours; the male emits an audible rasping vocalization as he trails and mounts the female, following a period of intense sniffing of the female's anogenital region. The female also frequently approaches and sniffs the male. In study 3, the role of female odours in the sexual behaviour of the male was examined in eight of the nine pairs used in studies 1 and 2. This was done by applying to the anogenital region of ovariectomized females a combination of urine and vaginal secretions taken from familiar and unfamiliar, and oestrogen-primed or non-oestrogen-primed females. The results show that odours from oestrogen-primed females are not sufficient to elicit male sexual behaviour, if the female is not sexually active. In study 4 the eight males were tested for their preferences for urine and vaginal secretion odours taken from females in different reproductive states and applied to cotton swabs. These males spent more time sniffing unfamiliar oestrous odours than unfamiliar non-oestrous odours and more time sniffing oestrous odours from a familiar female over those taken from an unfamiliar female.In study 5, 12 sexually active males were tested with oestrogen-primed females before and after either olfactory bulb removal or sham-surgery. Bulbectomized animals ceased copulating with females although females showed precopulatory approaches.Taken together, these studies suggest that normal sexual behaviour in the male woodrat requires that the female both possess the attractive odours (of oestrus) and that she engage in appetitive precopulatory behaviour.     

Sexual dimorphism in responses to unfamiliar intruders in the tamarin, Saguinus oedipus

Aspects of social structure in group-living species can be inferred by observing the responses of individuals to unfamiliar animals. This study examined the responses of mated pairs of cotton-top tamarins (Saguinus oedipus oedipus) to presentation of either unfamiliar conspecifics or members of a related tamarin species, the saddle-back tamarin (Saguinus fuscicollis fuscicollis). Male and female responses to intruders differed: resident males threatened, displayed piloerection, approached, and attacked intruders, especially males, while resident females showed increases in suprapubic scentmarking in the presence of intruders. Both males and females discriminated between the species of intruders, exhibiting more threats, scent-marking, piloerection, and approaches in the presence of conspecific intruders. There are pronounced sex differences in the signals and behaviour patterns that are elicited in an aggressive or territorial encounter with unfamiliar conspecifics in this monogamous primate.     

The first weeks of cohabitation of newly-formed heterosexual pairs of common marmosets (Callithrix jacchus)

16 pairs of common marmosets were formed, six of which were observed for 7 weeks, and ten for 4 weeks. A variety of behaviours was recorded, including sexual mounting, male tongue-smacking, female slit-eyed tongue-flicking, scent marks, huddling, allogrooming and autogrooming. Behaviours associated with sexual encounters occurred initially at high levels but declined during the study period. The incidence of sexual mounting was closely related to that of male tongue-smacking and female slit-eyed tongue-flicking. Other social behaviours including scent-marking and allogrooming did not show a consistent pattern of occurrence with respect to time or sexual activity.     

Opportunities for female choice in the bed bug Cimex lectularius

Bed bugs are cited as exemplars of sexual conflict because mating can only occur via traumatic insemination. However, past antagonistic coevolution between the sexes does not necessarily preclude current female choice. Here, we investigate opportunities for precopulatory female choice in bed bugs. We examined whether females seek out mating opportunities when they gain the most benefit: when females are virgin and/or have recently fed. But, we found that female mating and feeding status had little effect on female attraction to males and male odor. To determine whether females approach male harborages (home crevices) to seek matings in nature, we investigated where matings occurred among unfamiliar pairs of bed bugs. We found that, despite female attraction to male odor, matings were most likely to take place in the female's harborage rather than the male's harborage. We also examined the effect of feeding on male and female ability to mate. Whereas previous research reported that engorgement impaired female ability to refuse matings, we found that male feeding status had a larger effect on the success of mating encounters than female feeding status. Fed males had poor mating success, suggesting that males may be faced with a trade‐off between mating and feeding.     

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.     

Laboratory breeding studies of freshwater crayfish, Austropotamobius pallipes (Lereboullet)

SUMMARY. 1. Mature crayfish, collected from an Irish lake before breeding had started, were held in breeding combinations and their mating and brooding activities observed.
2. All mating attempts were initiated by the male. A single mating led to spawning within 6 days but a subsequent mating cancelled the effects of the first. Males mated more often when there were more females present. Males lacking a major cheliped mated less often than did normal males.
3. Larger males mated more often than did smaller males, and although males showed no female size preference, matings were less frequent and generally unsuccessful when males were much larger than females; the female was usually killed. Large females mated successfully with smaller males.
4. Females held at high densities with a larger male mated earlier than at low densities. However, aggression also increased with density; at high densities males fought and killed females.
5. Males held in pairs without females fought; in occasional mating attempts spermatophores were not positioned correctly. Paired females rarely fought; all spawned normally although unmated. Although their eggs soon died and were removed during grooming, brooding behaviour continued for at least 2 months.
6. Brooding females held in pairs shed pleopodal eggs during aggressive encounters. Females held singly showed a lower initial rate of egg loss.     

Size-related mating success in the shore crab Carcinus maenas (Crustacea: Brachyura)

The relationship between the size of a given mating male Carcinus maenas (L.) (Brachyura, Portunidae) and the size of the female with which it was paired was studied for 1248 pairs of crabs collected from the shore In 764 of these pairs the female was in pre-moult and so the pair were in pre-copula. In the remaining 484 pairs the female had already moulted and the pairs were in copula. There were significant correlations between the sizes of the males and females in both pre-copula and copula pairs. It was found that male Carcinus collected in mating pairs and tested in the laboratory were unable to distinguish between females in terms of their size or stage of pre-moult. The positive correlation between the sizes of males and females in mating pairs on the shore is proposed to be, in part, a function of a mechanical constraint of the size of female that a given male can hold, defend and copulate with. In addition, encounters between solitary males and males carrying females, resulting in the formation of new pairs, appear to enhance the size-related mating pattern observed.     

Social aspects of the termination of incubation behaviour in the ring dove (Streptopelia risoria)

The role of male and female ring doves (Streptopelia risoria) in the termination of incubation behaviour was studied first by observing heterosexual pairs (male and female) and homosexual pairs (female and female) (experiment 1). Male/female pairs incubate for 22 days whether squab or unhatched eggs are in the nest; female/female pairs incubate for 25 days or more. Males take the lead in terminating incubation. Another group of doves, separated from their (heterosexual) partners late in incubation, were exposed to one of four stimulus conditions: (a) an incubating dove; (b) a reproductively-inactive dove; (c) a reproductively-active dove; (d) visual isolation. Females extended the duration of their incubation when exposed to the sight of another dove, except when the stimulus dove was reproductively active. Males did not extend their incubation in response to these social cues. These social stimuli terminating incubation behaviour coordinate the withdrawal from the nest of male and female in preparation for the next breeding episode in this monogamous species.