Copulation Frequency Research Articles

Females Use Multiple Mating and Genetically Loaded Sperm Competition to Target Compatible Genes

Individuals in socially monogamous species may participate in copulations outside of the pair bond, resulting in extra-pair offspring. Although males benefit from such extra-pair behavior if they produce more offspring, the adaptive function of infidelity to females remains elusive. Here we show that female participation in extra-pair copulations, combined with a genetically loaded process of sperm competition, enables female finches to target genes that are optimally compatible with their own to ensure fertility and optimize offspring viability. Such female behavior, along with the postcopulatory processes demonstrated here, may provide an adaptive function of female infidelity in socially monogamous animals.

The effect of breeding density and male quality on paternity-assurance behaviours in the house sparrow, Passer domesticus

Several factors can influence the risk of cuckoldry through extra-pair paternity for male birds. The number of neighbouring males is thought to affect the chance of females engaging in extra-pair copulations, and species which breed both socially (colonially) and solitarily provide an ideal opportunity to test the effect of close proximity on extra-pair behaviour and paternity guards. In this study, the extent to which male house sparrows, Passer domesticus, used two alternative strategies, namely frequent copulation and mate-guarding, to ensure paternity was investigated. We also examined how males vary the two paternity guards according to their breeding sociality. Pairs at the dense colony started to copulate at a higher rate at the beginning of the fertile period than those of the medium-sized colony and solitary breeding pairs. Male house sparrows appear to fine-tune their strategies according to the breeding density. Both strategies are alternatively used in the weak fertile period but are simultaneously used in the peak fertile period. Our results suggest that males modify their strategy according to their individual abilities: mate-guarding intensity was positively correlated with the black breast badge size.

Level of sperm competition promotes evolution of male ejaculate allocation patterns in a moth

The risk and intensity of sperm competition can influence male adaptations that ultimately affect male fertilization success, for example investment in sperm production and strategic sperm allocation patterns. Previous studies have examined male behavioural responses to variation in immediate levels of sperm competition. Here we quantified the evolutionary responses of male adaptations resulting from long-term manipulation of the level of sperm competition. By varying the adult sex ratio of populations of the Indian meal moth, Plodia interpunctella, we successfully altered the frequency of male and female copulations, and thus the level of sperm competition experienced by males. As predicted by theory, males evolving under higher levels of sperm competition increased investment in sperm production and differed in their sperm allocation patterns across matings, compared to males evolving under intermediate and low levels of sperm competition. However, we found no evidence for trade-offs between ejaculate components, or between total sperm production and male body size in this species.

A Bayesian analysis of the temporal change of local density of proboscis monkeys: Implications for environmental effects on a multilevel society

To understand the effects of environmental factors on a social system with multilevel society in proboscis monkey units, the temporal change of the local density of sleeping sites of monkeys was investigated along the Menanggul river from May 2005 to 2006 in Malaysia. Proboscis monkeys typically return to riverside trees for night sleeping. The sleeping site locations of a one-male unit (BE-unit) were recorded and the locations of other one-male and all-male units within 500 m of the BE-unit were verified. In addition, environmental factors (food availability, the water level of the river, and the river width) and copulation frequency of BE-unit were recorded. From the analyses of the distance from the BE-unit to the nearest neighbor unit, no spatial clumping of the sleeping sites of monkey units on a smaller scale was detected. The results of a Bayesian analysis suggest that the conditional local density around the BE-unit can be predicted by the spatial heterogeneity along the river and by the temporal change of food availability, that is, the local density of monkey units might increase due to better sleeping sites with regard to predator attacks and clumped food sources; proboscis monkeys might not exhibit high-level social organization previously reported. In addition, this study shows the importance of data analysis that considers the effects of temporal autocorrelation, because the daily measurements of longitudinal data on monkeys are not independent of each other.

Nonindependent mate choice in monogamy

Nonindependent mate choice in monogamy

Evidence for age-dependent mating strategies in the simultaneous hermaphrodite snail,Lymnaea stagnalis(L.)

In many mating systems female reproductive capacity is a limiting resource over which males will compete. As a consequence, males and females have usually different fitness optimization strategies which may give rise to sexual conflict. Since simultaneous hermaphrodites have, in theory, the option to mate as male or as female at any time, conflict will occur if partners insist in taking the same role. Several lines of evidence exists that body size influences gender choice. However, growth in many invertebrates is indeterminate and therefore age is generally a covariant of size. We therefore investigated the effect of age on mating choices in the simultaneous hermaphrodite Lymnaea stagnalis. Using fully sexually mature animals sampled from three different age groups we show that copulation frequency declines with age. Specifically, in age-matched couples the frequency of primary and reciprocal copulations declines with age. Furthermore, the younger partner tends to mate as male with greater probability in couples of unequal age. Size was never a factor in the sex role preference of Lymnaea. Thus, young Lymnaea always attempt to copulate as male independent of the age of their partner, whereas senior snails act primarily as female. The sex role choices of middle-aged snails appear to depend on their partner's age. In addition, we demonstrate that the likelihood that an animal will copulate as male is not correlated with prostate gland size but correlates with the level of afferent electrical activity recorded in the nerve originating in the prostate gland. Together, our results indicate the existence of an age- and not size-dependent mating system in Lymnaea.

Breeding Behaviors of Blue Tailed Bee-eater of Nujiang Valley

By the method of ad libitum sampling and all-occurrence recording, breeding behaviors of Blue Tailed Bee-eater in the Agricultural Region of Nujiang Valley were observed from 26th March to 17th July, 2007. The result showed the most common foods that male birds fed to female birds are Odonata and Hymenoptera insects, accounting for 83.56%. The frequency of females accepting the food provided by males was 96.83%, and the frequency of copulation was 17.49% following food acceptance. During the daytime of the incubation period, comparison of time on nest between male and female showed no significant difference. Male mean on nest time was (23.5±21.6)min and female (25.8±11.5)min. Once hatched, a decrease in time spent warming the young was seen until the 20th day where the parents bird ceased warming. The nursing period of Blue Tailed Bee-eater was found to be 29 - 33 days, with the presence of a helper significantly improving the success rate of reproduction.

Sound is involved in multimodal communication of Loxosceles intermedia Mello-Leitão, 1934 (Araneae; Sicariidae)

Signals of different modalities are involved during courtship of the brown spider Loxosceles intermedia. A spine on the pedipalp is rubbed against the grooves on the retrolateral region of the chelicerae producing stridulatory signals, which have a dominant frequency of the airborne component range around 770 Hz for females and around 170 Hz for males. These values are significantly lower for the substrate-borne component. The sound pressure level of stridulatory signals lies below 50 dB and the velocity values below 1mm/s. The copulation frequency does not depend on the presence of pedipalps in females; however, in males the removal of pedipalps decreases the courtship frequency. During courtship, females vibrate their abdomens after being touched by the courting male, producing tremulatory signals with the dominant frequency below 100 Hz, sound pressure level below 60 dB and velocity below 3mm/s. This vibration may function as a sign of the akinesia state since it precedes the introduction of the embolus. Cuticular compounds probably determine the recognition of the male by the female. Data from the present study corroborate the generalist nature of L. intermedia in which signals of different modalities are used during courtship.

Copulatory behaviour in the colonial Eurasian Griffon vulture Gyps fulvus

We examined copulation patterns and associated sexual behaviour in the colonial Eurasian Griffon vulture Gyps fulvus during the pre-laying period. Eurasian Griffon vulture pairs conducted an average of 71.7 copulation attempts per clutch, with an average copulation frequency of 1.2 copulation attempts per day. Low copulation frequencies compared to other raptors and absence of mate-guarding suggest that this species does not possess adaptive behaviour aimed at increasing paternity assurance. However, the gradual increase in copulations during the fertile period is consistent with the sperm competition hypothesis.

Behavioural and body mass changes before egg laying in the Barn Owl: cues for clutch size determination?

To investigate laying decision and clutch size determination in indeterminate layers, we analysed in-nest activity (nest presence, and copulation, prey deliveries, and entrance frequencies) and female body mass change, as well as their relation to clutch size variation in five Barn Owl pairs (Tyto alba) nesting in eastern France. Body mass of the female and behaviour [copulation frequency, entrance frequency, and prey delivery to the nest by the male (in number and mass)] were monitored using an automated weighing system and a video camera. There was a consistent change of behaviour and foraging activity among pairs ca. 18 days before laying indicating that the females may be tied to the nest at this time. Barn Owls being indeterminate layers have their clutch size determined at the oviposition of the first egg of the clutch. Window correlation analyses between the clutch size and the female body mass gain indicate that the clutch size might be determined no later than a few days before the laying of the first egg. Our results suggest that female Barn Owls may use the pre-laying period to determine the clutch size using cues such as the male food deliveries (a proxy for male quality).

Agonistic Behaviour and Sexual Conflict in Atypical Reproductive Groups: The Case of Bearded VultureGypaetus barbatusPolyandrous Trios

AbstractSocial behaviour in species forced to form atypical breeding coalitions is poorly documented. The saturation of optimum territories in the Bearded vultureGypaetus barbatuspopulation in the Pyrenees has led floating males to settle in already occupied territories, thereby forming polyandrous trios. We examined the patterns of intrasexual aggression in five trios (nine reproductive events in total) during courtship. Alpha males initiated 82% of agonistic encounters that were mainly aimed at preventing or disrupting copulations. During the fertile period in recently formed groups, intrasexual aggression had a negative influence on the frequency of heterosexual copulations, which may be a contributing factor to the lower productivity of polyandrous trios. Females rejected a higher proportion of beta male‐ than alpha male‐initiated copulations, and rejected copulations with both alpha and beta males more often when the other male was present close by. These results indicate that alpha males cannot effectively prevent all copulation attempts by beta males and that females avoid harassment by minimizing sexual activity when both males are present. Aggression between males decreased with time, occurring less often in established than in recent trios, despite the fact that the frequency of heterosexual copulations – the cause of conflicts – was similar. The frequency of homosexual interactions tended to increase in established trios, suggesting that this behaviour may help to regulate aggression within these groups, although no significant relationship between homosexual interactions and aggression was found. In summary, reproductive conflicts in trios seem to be unavoidable, although they tend to decrease if the group is maintained. This suggests that, for birds in these groups, the maintenance of a quality territory is more important than solving sexual conflicts.

Mating first, mating more: biological market fluctuation in a wild prosimian.

In biology, economics, and politics, distributive power is the key for understanding asymmetrical relationships and it can be obtained by force (dominance) or trading (leverage). Whenever males cannot use force, they largely depend on females for breeding opportunities and the balance of power tilts in favour of females. Thus, males are expected not only to compete within their sex-class but also to exchange services with the opposite sex. Does this mating market, described for humans and apes, apply also to prosimians, the most ancestral primate group? To answer the question, we studied a scent-oriented and gregarious lemur, Propithecus verreauxi (sifaka), showing female dominance, promiscuous mating, and seasonal breeding. We collected 57 copulations involving 8 males and 4 females in the wild (Berenty Reserve, South Madagascar), and data (all occurrences) on grooming, aggressions, and marking behaviour. We performed the analyses via exact Spearman and matrix correlations. Male mating priority rank correlated with the frequency of male countermarking over female scents but not with the proportion of fights won by males over females. Thus, males competed in an olfactory tournament more than in an arena of aggressive encounters. The copulation frequency correlated neither with the proportion of fights won by males nor with the frequency of male countermarking on female scents. Male-to-female grooming correlated with female-to-male grooming only during premating. Instead, in the mating period male-to-female grooming correlated with the copulation frequency. In short, the biological market underwent seasonal fluctuations, since males bargained grooming for sex in the mating days and grooming for itself in the premating period. Top scent-releasers gained mating priority (they mated first) and top groomers ensured a higher number of renewed copulations (they mated more). In conclusion, males maximize their reproduction probability by adopting a double tactic and by following market fluctuations.

Prevalence of avian influenza and sexual selection in ducks

Investigations of avian influenza have so far focused on the global circulation and conversion of virus strains and showed that wild waterfowl and especially ducks represent the reservoir and source of virus strains that can become highly pathogenic in domestic species. Information is largely missing regarding the routes of transmission between individuals and the species of concern for transmission. Moreover, evolutionary comparative studies only considered ecological factors and ignored other potential determinants of virus transmission. Such determinants include the mating strategies of hosts because links between sexual selection and parasites are well known. Here, we show that morphological adaptations associated with copulation frequency in both male and female hosts strongly explain differences in low-pathogenic influenza prevalence among wild duck species. Prevalence is negatively related to male phallus length and female vaginal complexity, traits that evolved due to sexual conflict over forced copulations. This pattern suggests a hitherto unrecognized transmission route of the virus via copulation and subsequent mother–offspring transfer. Due to a relationship between forced copulations and the expression of white wing covert patches, male covert patch expression and sexual dichromatism in covert patch expression are positively related to influenza prevalence. Our results suggest that the arms race between male and female reproductive tracts had epidemiological consequences. Our findings further suggest that morphological correlates of sexual selection in ducks, including conspicuous plumage ornamentation, could be robust clues to identify high-risk host species during the large-scale monitoring of avian influenza.

Pre-winter copulation enhances overwintering success of Orius females (Heteroptera: Anthocoridae)

The majority of insects that overwinter in the adult stage copulate post-winter. Some such insects copulate not only post-winter, but also pre-winter and/or during winter. In Orius species, only females overwinter. As they have no chance to copulate post-winter, they do so pre-winter. We expected pre-winter copulation to be associated with increased survival of females during overwintering; therefore, we tested the effects of pre-winter copulation on winter survival in females of three Orius species, O. sauteri, O. nagaii and O. strigicollis. Under semi-field conditions, clear differences in overwintering survival were observed between copulated and virgin females in the late overwintering period. Overwintering success of copulated females was higher than that of virgin females; however, copulation frequency did not affect winter survival of females. With regard to the mechanism increasing winter survival, two possible explanations arose from this study. The first is the donation of nutrients from males through copulation, and the second is that copulation affects diapause syndrome and/or behavioral changes in females.

Sexual selection does not influence minisatellite mutation rate

BackgroundMoller and Cuervo report a significant trend between minisatellite mutation rate and the frequency of extra-pair copulations in birds. This is interpreted as evidence that the high rate of evolution demanded by sexual selection has itself selected for a higher mutation rate in species where selection is strongest. However, there are good a priori reasons for believing that their method of calculating minisatellite mutation rates will be highly error prone and a poor surrogate measure of the evolutionary rate of genes. I therefore attempted to replicate their results using both their data and an independent data set based on papers they failed to locate.ResultsI find that Moller and Cuervo's data set contains numerous errors that act somewhat to strengthen their key regression. More importantly, data from uncited papers fail to replicate their reported trend and one species in particular, Vireo olivaceus, is apparently deliberately omitted, yet its inclusion removes significance from the original correlation. Over the small number of cases were comparisons can be made, mutation rate estimates do not differ between species but do vary significantly depending on the laboratory/operator.ConclusionThere appears to be no clear relationship between minisatellite mutation rate and EPC rate in birds. The previously reported trend can be attributed to data transcription errors and unfortunate data selection. My analysis highlights the importance of total methodological transparency when conducting meta-analyses.

Pre‐copulation intervals, copulation frequencies, and initial progeny sex ratios in two biotypes of whitefly, Bemisia tabaci

AbstractThe whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is a species complex, and its systematic classification requires controlled crossing experiments among its genetic groups. Accurate information on pre‐copulation intervals, copulation frequencies, and initial frequency of egg fertilization of newly emerged adults is critical for designing procedures for collecting the virgin adults necessary for these experiments. In the literature, considerable variation is reported between B. tabaci populations, with respect to the length of the pre‐copulation interval and the initial frequency of egg fertilization. Here, we used a video‐recording method to observe continuously the copulation behaviour of the Mediterranean/Asia Minor/Africa (B biotype) and the Asia II (ZHJ1 biotype) groups of B. tabaci. We also recorded the initial frequency of egg fertilization, as determined by the sex of the progeny. When adults were caged in female–male pairs on leaves of cotton plants, the earliest copulation events occurred 2–6 h after emergence; at 12 h after emergence 56–84% of the females had copulated at least once, and nearly all (92–100%) had copulated at least once by 36 h after emergence. Both females and males copulated repeatedly. Approximately 80 and 20% of copulation events occurred during the photophase and scotophase, respectively. By 72 h post‐emergence, the females of the B and ZHJ1 biotypes had copulated on average 6.1 and 3.9 times, respectively. When adults were caged in groups on plants 1–13 h after emergence, 30–35% of the eggs deposited during this period were fertilized, and approximately 90% of females were fertilized by the end of the 13 h. Although timing of copulation differed in detail between the two genetic groups, the results demonstrate that B. tabaci adults can start to copulate as early as 2–6 h post‐emergence and the majority of females can become fertilized on the day that they emerge.

Paternity assurance through frequent copulations in a wild passerine with intense sperm competition

Frequent copulation is assumed to be an important male reproductive strategy for paternity assurance in species with female sexual promiscuity. However, the empirical evidence supporting this hypothesis is limited. We examined copulation behaviour in relation to within-pair paternity in the socially monogamous tree swallow, Tachycineta bicolor, a passerine bird species with frequent copulation, a lack of mate guarding and high levels of extrapair paternity. We found that the frequency of within-pair copulation attempts increased and peaked just before the appearance of the first egg. A marked drop in the frequency of copulation attempts was observed once the first egg was laid. Furthermore, the frequency of successful within-pair copulations was highly repeatable for particular pairs within the 3 days prior to appearance of the first egg. Finally, males that obtained a higher number of successful within-pair copulations during this time also sired a larger proportion of the offspring in their own brood. Our findings suggest that frequent copulations just before the start of egg laying is an adaptation to decrease the risk of being cuckolded in the presence of sperm competition, and thus provide empirical support for the paternity assurance hypothesis. Crown Copyright 2008 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. All rights reserved. Paternity assurance is critical to male fitness, particularly in species in which females frequently participate in extrapair copulations (EPCs) and males provide costly parental care. In response to fitness loss due to cuckoldry, several types of paternity assurance behaviour have evolved across taxa. One strategy is constant mate guarding by following, as males can protect their paternity by ensuring that no other male has an opportunity to mate with their paired female (Moller & Birkhead 1991). However, for some species, constant mate guarding may be constrained by territory protection or other activities. The paternity assurance hypothesis (Moller 1987; Simmons 1990), also known as the paternity confidence hypothesis (Eens & Pinxten 1995) and the sperm competition hypothesis (Birkhead et al. 1987), suggests that for species in which EPCs are common, males copulate frequently with their pair females to avoid being cuckolded. Males may minimize cuckoldry through frequent copulation by devaluing EPCs that their mates

Do male paternity guards ensure female fidelity in a duetting fairy-wren?

Most socially monogamous bird species engage in extra-pair mating, and consequently males may adopt various behavioral strategies to guard paternity. However, the relationship between mate guarding and extra-pair paternity is unclear: low levels of extra-pair paternity can be associated either with no mate guarding or with intense mate guarding. We investigate paternity guards in the purple-crowned fairy-wren (Malurus coronatus), a duetting species where extra-pair paternity is rare. This species is unusual in a genus known for extremely high levels of extra-pair mating. We examine the behavioral interactions between the sexes underlying these low rates of extra-pair paternity and show that male purple-crowned fairy-wrens do not use frequent copulation or courtship feeding to assure paternity or guard females acoustically by duetting. Males maintain close proximity to females both when they are fertile and when they are not breeding and do not invest in courtship displays to extra-pair females. Consistent with predictions of theoretical models, low extra-pair paternity in this species may be related to female fidelity rather than male paternity assurance strategies, but short-term removal of males would be necessary to test this experimentally.

The role of uropygial gland on sexual behavior in domestic chicken Gallus gallus domesticus

Recent studies have indicated that avian social behavior is influenced by olfactory cues. During the reproductive season a change in the chemical composition of uropygial gland secretion has been reported in some species and the hypothesis that olfactory signals may be produced by this gland has been proposed. To examine this hypothesis we performed two behavioral experiments to determine whether a female's uropygial gland produces chemical signals that stimulate mating behaviors in domestic chickens. In Experiment 1 the role of the female's uropygial gland in male mating behavior was examined by removing and examining the female's uropygial gland. The frequency of mounts and copulations of intact male birds with sham-operated female birds was significantly higher than with uropygial glandectomized female birds. With respect to the number of waltzing that is one of the courtship displays intact males showed no significant difference between sham-operated female birds and uropygial glandectomized female birds. In Experiment 2 the relationship between male olfaction and the female's uropygial gland was investigated using olfactory bulbectomized male birds. The number of mounts and copulations of sham-operated male birds with sham-operated female bird was significantly higher than with uropygial glandectomized female birds. In contrast olfactory bulbectomized male birds showed no significant differences in the number of mounts and copulations between sham-operated female birds and uropygial glandectomized female birds. These results indicate that intact and sham-operated male birds prefer to mate with female birds with the uropygial gland. The number of courtship waltzing of sham-operated male birds showed no significant difference. However olfactory bulbectomized male birds significantly courted to uropygial glandectomized female birds. Summarizing our results show that while anosmic males did not have any preference, both intact and sham-operated male birds chose to mate with female birds having an intact uropygial gland, suggesting that mate preference involves in male olfaction and that the female's uropygial gland acts as a source of social odor cues in domestic chickens.

Female attractiveness mediates the relationship between in-pair copulation frequency and men’s mate retention behaviors

More attractive women are more likely to be pursued as mates by men other than their long-term partner and, therefore, to place their partner at greater risk of cuckoldry (investing unwittingly in a child to whom he is genetically unrelated). Men partnered to more attractive women perform more mate retention behaviors – behaviors designed to thwart a woman’s infidelity. With greater risk of female infidelity, men may perform additional anti-cuckoldry tactics such as frequent in-pair copulations (IPC). We secured self-reports from 277 men in a long-term relationship and investigated: (1) the relationship between female partner’s attractiveness and IPC frequency and (2) the mediating role of female partner’s attractiveness on the relationship between IPC frequency and male mate retention behaviors. The results indicated that female attractiveness: (1) predicts IPC frequency and (2) partially mediates the relationship between IPC frequency and male mate retention behaviors. The discussion addresses the mediated relationship, notes limitations of the research, and highlights directions for future research.