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While scholars largely agree men's infidelity evolved by increasing offspring quantity, the evolutionary drivers of women's infidelity remain debated. The "good genes" (dual mating strategy) hypothesis posits infidelity allows women to pair the preferred genes of an affair partner with the preferred investment of their primary partner (Gangstad & Thornhill, 1998). The mate-switching hypothesis instead argues infidelity helps women obtain a new mate without a period of deprivation (Buss et al., 2017). To test these hypotheses, we conducted a pre-registered survey of 254 individuals from 19 countries and 6 continents who were previously or currently engaged in infidelity. We measured individuals' perception of their primary partner and their affair partner across four domains: physical attractiveness, personal attractiveness, attractiveness as a co-parent, and overall desirability (mate value). We also asked participants to report their motivations for the affair. Consistent with a dual mating strategy, women experienced stronger physical attraction to their affair partners and stronger parental attraction to their primary partners. Contrary to the mate-switching hypothesis, women did not prefer their affair partners overall, parentally, or personally. There were no significant gender differences in these findings, suggesting strategic dualism in men as well. Our qualitative data revealed a more nuanced story at the individual level, with participants reporting motives consistent with a variety of evolutionarily coherent strategies. While our quantitative results speak to the relevance of the dual-mating hypothesis to understanding infidelity, our findings also suggest that seeking infidelity's primary explanation in either gender is, perhaps, too simple an approach to the issue. [ABSTRACT FROM AUTHOR]

The widespread occurrence of extra-pair paternity (EPP) in birds adds rich complexity to our understanding of sexual selection and mating system evolution. Extra-pair matings are typically cryptic so for most species, we lack the detailed behavioral observations needed to fully determine whether both sexes benefit from EPP and when trait correlations with EPP are found, whether they reflect female choice or male intrasexual competition. Here we examine behavioral and morphological correlates of EPP in the lark bunting (Calamospiza melanocorys), a grassland songbird where EPP-seeking behaviors of males are unusually overt and conspicuous. Males sought EPP by closely following receptive pairs, often in groups. Virtually all observed extra-pair copulation attempts involved male aggression, were resisted by females, and larger females had a lower rate of extra-pair paternity in their nests. Male plumage traits predicted both male effort in seeking EPP (number of mating groups joined) and fitness gained through EPP; these same male traits have previously been linked to male-male competition but were not linked to consistent mate choice in lark buntings. There was no trade-off between investment in seeking EPP and fitness at a male's own nest, indicating that fitness from EPP is likely a potent driver of sexual selection in lark buntings, one that may not entirely be driven by female fitness interests. [ABSTRACT FROM AUTHOR]

There is growing evidence that engaging in extra‐pair copulations may be a strategy by which females can modify their initial mate choice if they are constrained by primary choice of the social mate. Several factors such as genetic similarity and adult phenotypic traits can affect extra‐pair paternity (EPP) patterns, but the relative importance of these factors may vary among species. Moreover, interactive effects of male and female characteristics have rarely been considered. Here, we aimed to study how multiple parameters characterizing a breeding pair (i.e. genetic similarity between mates, partners' age and laying date) predict the occurrence of EPP at the brood level. The study uses 4 years of data from a wild population of Blue Tits Cyanistes caeruleus. Contrary to predictions of the inbreeding avoidance hypothesis, we did not find a positive relationship between the occurrence of EPP and the relatedness of social mates. We also found that the probability of EPP was unrelated to laying date. However, EPP was predicted by an interaction of social partners' ages. Specifically, EPP was less likely when old females were paired with old males in comparison to old females paired to young males. Our study suggests that the occurrence of EPP may be the result of behavioural interactions in which both male and female age are important for determining the outcome. Our results confirm the importance of considering the interactions of male and female characteristics in studies investigating EPP patterns. [ABSTRACT FROM AUTHOR]

Sexual conflict in producing and raising offspring is a critical issue in evolutionary ecology research. Individual experience affects their breeding performance, as measured by such traits of provisioning of offspring and engagement in extra-pair copulations, and may cause an imbalance in sexual conflict. Thus, divorce is hypothesized to occur within aged social pairs, irrespective of current reproductive success. This concept was explored in the azure-winged magpie Cyanopica cyanus by investigating the divorce of a social pair and its relationship to their changes in breeding performance with prior experience. Females engaging in extra-pair copulation may intensify sexual conflicts and may be the main reason for divorce. Once divorced, females repairing with an inexperienced male realized higher reproductive success than that repairing with an experienced male; males repairing with an experienced female realized higher reproductive success than that repairing with an inexperienced female. This finding indicates that the fitness consequence of divorce depends on the breeding experience of new mates. Divorced females can obtain more extra-pair copulations, whereas divorced males cannot, when they repair with inexperienced breeders. Divorced females provisioned a brood at lower rates than inexperienced females whereas divorced males had no such difference. It appears that divorced females can obtain an advantage in sexual conflicts with inexperienced mates in future reproduction. Consequently, females are probably more active than males in divorcing their aged mates so as to select an inexperienced male as a new mate. Azure-winged magpies thus provide novel insights into the implications of sexual conflict in birds. [ABSTRACT FROM AUTHOR]

Molecular studies have shown that, although most avian species are socially monogamous, they can exhibit different reproductive strategies, such as extra-pair paternity (EPP) and intraspecific brood parasitism (IBP). We investigated the genetic mating system of the Magellanic Penguin, Spheniscus magellanicus, a species that is reported to be monogamous, with little or no evidence of extra-pair paternity, high partner faithfulness over the years and intense biparental care. Thus, we proposed that if EPP does occur, the rate will be low and could be related to increased genetic diversity among offspring or the body condition of parents. As a consequence, we hypothesize that offspring from EPP will exhibit faster growth than non-EPP offspring, thus increasing their survival probability. In contrast to expectations, EPP was detected in 31% of the offspring and 48% of the nests had at least one extra-pair young. In addition, 6% of chicks were not the offspring of the putative mother or either member of the social pair, indicating evidence of IBP. However, we did not find a difference in genetic diversity between nests with or without EPP, nor did we find differences in parent body condition. Offspring from EPP showed slightly faster growth than non-EPP offspring, although this difference was not statistically significant. These results reveal a high rate of EPP and a low rate of IBP, both of which were previously unknown for this species. Our findings demonstrate that the Magellanic penguin has a more complex social mating system than previously thought. [ABSTRACT FROM AUTHOR]

Basic knowledge about the genetic mating system is lacking for the great majority of the approximately 10,000 extant bird species. Filling this knowledge gap is not only critical for a comprehensive understanding of the reproductive ecology of each particular species, but also for increasing the power of comparative approaches to uncover and explain interspecific patterns of variation in avian reproductive traits. Using six polymorphic microsatellite markers, we here present the first parentage study in the socially monogamous Fieldfare Turdus pilaris. In parallel, we also examine variation in sperm morphology and relationships between sperm traits and paternity loss of social males. Across two study years, extra-pair paternity was detected in 46.4% (95% CI: 28.9–64.9%) of 28 broods, and on average 27.6% (95% CI: 16.8–41.9%) of nestlings per brood were extra-pair offspring in a population in central Norway. These observed extra-pair paternity rates fall within the range of reported estimates of extra-pair paternity for four congeneric Turdus species (between 36 and 65% of broods and 27 and 46% of nestlings). Sperm total length was 87.0 ± 2.9 (SD) μm (range 79.7‒96.8 μm) and 59.3% (95% CI: 37.1–73.3%) of the total phenotypic variation in sperm total length was explained by differences between sperm samples collected from 17 different males. The among-sample coefficient of variation in mean sperm total length was 2.70% (95% CI: 1.99–3.17%). We found no evidence for effects of sperm total length or relative midpiece length on loss of paternity among broods of 13 males. [ABSTRACT FROM AUTHOR]

Seabirds are long-lived birds that invest in offspring at very high levels, for which male parental care is indispensable. These characteristics are thought to explain seabirds' generally low level of extra-pair paternity (EPP). Although the Streaked Shearwater (Calonectris leucomelas) is a socially monogamous seabird, it is known to copulate outside its social pair bond, which implies the frequent occurrence of EPP. In the closely related Cory's Shearwater Calonectris borealis, cuckoldry is related to body size of the social male. To determine whether body-size-related EPP occurs among Streaked Shearwaters, we established 39 new microsatellite markers for parentage analysis and compared body size between cuckolded and non-cuckolded males. With the new markers, we found that extra-pair males sired 17 (15.0%) of 113 offspring during the 2014-2016 study period, which included three 1.5-month chick-rearing periods. This percentage is among the highest recorded for seabirds. We also found the bill and wing length of cuckolded males to be significantly shorter than those of non-cuckolded males, and that females can reject attempted copulations. These observations imply that EPP in this species is size related and involves female acceptance. [ABSTRACT FROM AUTHOR]

Raptors are considered genetically monogamous birds. In particular, only one case of extra-pair paternity has been recorded in the Northern Goshawk (Accipiter gentilis) in North America. In Europe, a few observations of extra-pair copulations have been reported in this species. In 2012, we checked two closely neighbouring nests (1.37 km) of the Northern Goshawk in a woody landscape near the Liberec town (north of the Czech Republic). We caught both parents (male M1 and female F1) at one nest and the female (F2) at the other nest to obtain blood samples for a DNA analysis. Moreover, a single nestling at one nest and three nestlings at the other nest were blood-sampled. DNA analysis revealed that the M1 male was a father of two nestlings in the two different nests. This is the first record of extra-pair paternity in the Northern Goshawk in Europe. Moreover, our study proved that in Europe extra-pair copulations in the Northern Goshawk do not occur only in urbanized populations. [ABSTRACT FROM AUTHOR]

Males of many bird species feed their mates during the pre‐incubation period. The food provisioned by males during these courtship feedings (CFs) represents the key source of energy for the female during egg formation. Non‐pair males may trade food for extra pair copulations (EPC) with females during extra pair courtship feeding (EPCF), while females may trade copulations for food with non‐pair males to obtain additional resources. Because EPCs can be costly to the females, they are expected to behave in ways that will deceive non‐pair males to obtain additional resources at no cost to themselves. We investigated EPCFs in whiskered terns Chlidonias hybrida breeding in food‐rich conditions, on carp ponds in southern Poland. Almost all CFs (n = 2751) took place during the female's fertile period and peaked just before clutch initiation. 10% of all CFs were performed by non‐pair males. Females tried to obtain food from the non‐pair male during 39% of EPCFs, by swindling (the female solicits a non‐social male for copulation and tries to swindle food with no cloacal contact) or by snatching (the female tries to take the gift without engaging in copulation). In the remaining 61% of EPCFs, females did not react or chased the visiting male away. The probability of a female's obtaining food during EPCF was much higher (0.69, 95% CI: 0.47–0.85) if she swindled rather than snatched (0.08, 95% CI: 0.02–0.22). Only 0.7% of EPCFs were followed by EPCs. The high availability of food in the study area allows males to perform frequent EPCFs, despite the very low probability of obtaining EPCs. This is the first time that ‘true deception’ during EPCFs has been reported in birds: swindling females obtain food from non‐pair males at no immediate detectable cost to themselves. [ABSTRACT FROM AUTHOR]

The origin and maintenance of polyandry is one of the key unresolved questions in evolutionary biology. In particular, extra-pair paternity (EPP) due to polyandry is observed in most (socially-) monogamous female birds and the frequency of EPP is surprisingly high (up to 72% in a clutch on average in some species). Many case-by-case hypotheses have been presented to explain this phenomenon but a ubiquitous explanation is still lacking. One possible general explanation is bet-hedging, which is a strategy to avoid the risk associated to mating with a single unsuitable male and thus to minimize the chances of complete reproductive failure by the female. Here, we present a mathematical solution to demonstrate that bet-hedging polyandry becomes highly effective if the risk of extinction of a female lineage attributable to male deficiencies is high in small subpopulation or under limited mate availability. Therefore, cuckoldry or polyandry may be a female strategy to spread the risk of extinction of her genotype over multiple males. The results agree well with the observed EPP frequencies in natural populations and the results of a meta-population simulation model. Our theory contributes new insights applicable not only to birds but also to a broad taxonomic range of animals. [ABSTRACT FROM AUTHOR]

The Cape VultureGyps coprotheresis an Endangered colonial cliff-nesting species that is typically cited as monogamous. Observations of wild Cape Vulture colonies note extra-pair breeding activities but homosexual activity has never been confirmed. Observations of breeding behaviours within a captive colony were conducted at VulPro’s breeding facilities in South Africa The captive breeding programme included 10 breeding pairs and a total of 41 non-releasable, individually recognisable, and genetically sexed subadults or adults. Observations were conducted over the 2014 breeding season as part of a study investigating the social and rearing conditions of chicks intended for release in a population supplementation programme. A high percentage of total colony copulation attempts (22%) were extra-pair copulations but only 23 interactions resulted in cloacal contact or possible sperm transfer. Four paired males formed extra-pair relationships, two of which were homosexual. [ABSTRACT FROM PUBLISHER]

Several studies have suggested that vegetation structural complexity can influence the frequency of extra-pair copulations, especially by reducing mating-guarding efficiency. Here we investigate if habitat structural complexity affects broad patterns of extra-pair paternity (EPP) and extra-pair broods (proportion of nests presenting at least one extra-pair young-EPB), specifically testing the prediction that species living in habitats with denser vegetation would have a higher frequency of EPP or EPB. We reviewed studies reporting EPP and EPB levels and categorized structural complexity of vegetation for the study population into five habitat categories. Using both phylogenetic ANOVA and phylogenetic generalized least squares (PGLS), we found no significant effects in either EPP or EPB rates. Under the mating-guarding point of view, possible explanations for the lack of support are (i) trade-offs between the possibilities for females to escape from male surveillance and the difficulty to encounter neighbor extra-pair males by visual orientation in areas with dense vegetation; (ii) the predominance of passerine birds in most categories of vegetation complexity, which are small and agile, such that even less vegetated areas may allow extra-pair copulation to be concealed; (iii) environmental components other than vegetation, such as rocks and cliffs, also could provide concealment opportunities for extra-pair copulation; and (iv) the performance of predawn forays, when habitat complexity may play a weak role on guarding effectiveness. A macroecological understanding of EPP and EPB is a continuing challenge for understanding variation in avian mating systems. Our results contribute to improving the knowledge of the impact of habitat in sexual selection. Significance statement: Although a vast literature on avian extra-pair paternity (EPP) and its causes exists, the influence of a number of environmental parameters remains poorly addressed. One such parameter is habitat structural complexity. Scattered pieces of evidence from single-species studies have supported the idea that in more complex habitats, i.e., dense vegetation, extra-pair copulation (EPC) is facilitated by concealment opportunities. Here we provide a broad review on studies reporting EPP and EPB (proportion of nests presenting at least one extra-pair young) levels, and we classified study sites into five habitat categories, which were then compared. After controlling for phylogenetic effect, we found no significant effect. Possible explanations for the nonsignificance under a mating-guard perspective can involve trade-offs between the possibilities for females to escape from social surveillance and the difficulty to encounter neighbor extra-pair mates, the availability of habitat components other than vegetation providing concealment for EPC, and the use of strategies such as predawn forays to avoid mate-guarding consequences. Our results further expand the role of habitat in avian sexual selection. [ABSTRACT FROM AUTHOR]

An increasing number of empirical studies in animals have demonstrated male mate choice. However, little is known about the evolution of postpairing male choice, specifically which occurs by differential allocation of male parental care in response to female signals. We use a population genetic model to examine whether such postpairing male mate choice can evolve when males face a trade-off between parental care and extra-pair copulations (EPCs). Specifically, we assume that males allocate more effort to providing parental care when mated to preferred (signaling) females, but they are then unable to allocate additional effort to seek EPCs. We find that both male preference and female signaling can evolve in this situation, under certain conditions. First, this evolution requires a relatively large difference in parental investment between males mated to preferred versus nonpreferred females. Second, whether male choice and female signaling alleles become fixed in a population versus cycle in their frequencies depends on the additional fecundity benefits from EPCs that are gained by choosy males. Third, less costly female signals enable both signaling and choice alleles to evolve under more relaxed conditions. Our results also provide a new insight into the evolution of sexual conflict over parental care. [ABSTRACT FROM AUTHOR]

Aechmophorus grebes are socially monogamous and copulate only on floating nests. Motion-activated cameras were used to study the copulation behavior of Aechmophorus grebes at Clear Lake, Lake County, California, USA, during 2015-2016. The sex of both partners was determined in 226 of 435 copulations; of these, 8.0% were female mounting male (reverse mountings), including 6.4% by Western Grebe ( A. occidentalis; n = 171), 0% by Clark's Grebe ( A. clarkii; n = 31), and 42.9% by mixed pairs ( n = 14). One copulation comprised two Western Grebes mounting a third individual on a nest; the sexes could not be determined, but most likely consisted of two males mounting a female. Another copulation comprised a male-male mounting by Western Grebes. These records provide the first documentation of simultaneous extra-pair copulation and male-male mounting in the Western Grebe. [ABSTRACT FROM AUTHOR]

Over the last two decades, several studies have shown that the mating systems of various birds are more com- plex than previously believed, and paternity tests performed with molecular techniques have proved, for instance, that the commonly observed social monogamy often presents important variations, such as extra-pair paternity. However, data are still largely biased towards temperate species. In our study, at an area of the Brazilian Atlantic Forest, we found broods containing at least one extra-pair young (EPY) in the socially monogamous White-necked Thrush Turdus albicollis (Vieillot, 1818). Paternity tests using six heterologous microsatellite loci revealed that four of 11 broods (36.4%) presented at least one extra-pair young (EPY). This rate of EPY is within the range found for other studies in the tropics. This is one of the few studies that present detailed paternity analyses of a Neotropical rainforest passerine. Our findings corroborate the early insights that breeding strategies involving cheating can also be widespread among Neotropical socially monogamous songbirds. [ABSTRACT FROM AUTHOR]

Previous field studies of gibbon groups of the genus Nomascus have shown that multi-female polygynous groups are present and quite common in the northernmost species. Our research shows that multi-female groups are also present in the southernmost species, the Southern Yellow-cheeked Crested Gibbon Nomascus gabriellae (Thomas). Various gibbon groups are being followed and habituated in Seima Protection Forest by local and international researchers. Data collected during the first nine months of observations shows the presence of a stable multi-female family group in the study area, with two breeding females with infants. This is the first time this has been reported and confirmed for this particular species of Nomascus. [ABSTRACT FROM AUTHOR]

Social partners of some bird species copulate during the incubation period; explanations for this include strengthening social bonds and/or reducing the risk of extra-pair paternity in consecutive clutches within the same season. According to current opinion, Northern Lapwings Vanellus vanellus exhibit this behavior, uncommon in shorebirds, in order to strengthen social bonds. Based upon field observations at 36 nests, I found that mating frequency increased after cessation of male incubation bouts, i.e., after the male had been unable to guard the female and prevent opportunities for extra-pair mating. This pattern is consistent with the sperm competition hypothesis: increased rates of copulation may be a way of devaluing the sperm of possible competitors and a strategy to secure paternity in subsequent clutches, which Northern Lapwings frequently lay throughout the breeding season. This explanation extends the previous interpretation of the frequent mating of Northern Lapwings during the incubation period. [ABSTRACT FROM AUTHOR]

Extra-pair copulation without apparent direct benefits is an evolutionary puzzle that requires indirect fitness benefits to females to explain its ubiquity in socially monogamous mating systems. Using wild scarlet rosefinches ( Carpodacus erythrinus), we tested if genetic benefits in the form of global (microsatellite) heterozygote advantage, adaptive genes (major histocompatibility complex), or complementary genes (using both markers) were responsible for female extra-pair mate choice, while considering that the benefits of mate choice may be conditional on female genotype. We found no evidence for assortative or relatedness-based mating (complementary genes), but higher MHC diversity, microsatellite heterozygosity, and condition were significantly related to male extra-pair paternity (EPP) success. In contrast, female probability of having extra-pair offspring decreased with increasing heterozygosity. Interestingly, extra-pair and within-pair males had higher heterozygosity than their female mates and extra-pair males had higher MHC supertype diversity. The only genetic difference between extra-pair and within-pair offspring was lower variance in MHC allelic diversity within extra-pair offspring, providing limited support for indirect genetic fitness benefits for the markers tested. Offspring had both higher neutral heterozygosity and number of MHC supertypes than adults, as well as significant identity disequilibrium, potentially suggesting that mates are chosen to increase offspring diversity in the period of the present study. Overall, our results point to an EPP heterozygote advantage for males, especially when involving less heterozygous females, and suggest that heterozygosity effects on reproduction may differ between the sexes. [ABSTRACT FROM AUTHOR]

Despite advances in knowledge, in many bird species, the true mating system is unknown, and especially so for birds breeding at low densities under natural conditions. We studied paternity at the population and breeding pair level in the Red-breasted Flycatcher (Ficedula parva), a small, migrant passerine breeding in old-growth Białowie a Forest. Over seven breeding seasons we genotyped a total of 159 nestlings and 25 adult males as fathers from 33 broods of the Red-breasted Flycatcher. Extra-pair young were present in eight broods (24.2%). Twelve (7.5%) chicks mismatched with the 'social' male in several loci. Both low breeding density and synchrony in breeding phenology can explain such findings. Also of interest was the share of extra-pair paternity at the individual level, in relation to the age/ornamentation of the extra-pair male. Male Red-breasted Flycatchers exhibit delayed plumage maturation. Young males (second year) are without an orange badge on the throat and breast, while older males (after-second year) are ornamented and have an orange badge. The extra-pair nestlings were found in eight broods , four with young males as a fathers (36.4%) and four in broods of old males (18.2%). However, in all seven cases when the age of the extra-pair partner was known, irrespective of the age of the social father, the extra-pair partner was a male with an orange patch on the breast. This indicated female preference for ornamented males as partners for extra-pair copulation. [ABSTRACT FROM AUTHOR]

Active pursuit of extra-pair mating has been reported for Indri indri, the socially monogamous largest living lemur. This study, conducted in a mountain rainforest in eastern Madagascar, presents the first evidence for extra-pair mating of indri and discusses the alternative mating strategy and alteration of the social, territorial, spatial, and vocal behavior of the adult female of a group of wild indris. Further studies may investigate whether extra-pair copulation is an attempt to breed with a partner of superior quality and thus lead to extra-pair paternity. If so, it could potentially play a role in maintaining genetic variability within a population. [ABSTRACT FROM AUTHOR]

Fairy-wrens (genus Malurus) maintain territories year round, and breed cooperatively, with all members of the social group provisioning young. Despite living with several adult males, the breeding female typically cuckolds all of them, seeking fertilisations from extra-group males that provide no care to her offspring, instead caring for the young reared on their own territory. We trace the evolutionary origins and persistence of this extraordinary combination of traits. We argue that the high rate of infidelity in some fairy-wrens facilitates social pairing among nuclear family relatives, rather than being an evolutionary response to avoid inbreeding. It seems likely that females mate with extra-group males to improve the genetic quality of their offspring. The ability of males to maintain breeding plumage for long periods is the primary criterion for female choice; only older males can do so. Several features of the mating system undermine the accuracy of female choice, and low-quality males exploit this uncertainty. Extra-group matings by low-quality males can help stabilise the mating system but may leave it vulnerable to collapse under certain circumstances. Nonetheless, sexual selection in most species is very strong, confirming the utility of fairy-wrens as model organisms for the study of mate choice and intersexual selection. [ABSTRACT FROM AUTHOR]

Cooperative breeding among birds was first discovered in the genus Malurus (Maluridae), the fairy-wrens. Cooperative care arises because male, and sometimes female, offspring remain in their natal territory and help the adults rear offspring. Early uses of data from Superb Fairy-wrens (Malurus cyaneus) to illustrate how kin altruism can explain helping behaviour were based on flawed assumptions. Most importantly, high rates of extra-group mating mean that the helpers often assist adults to which they are unrelated. However, measuring the costs and benefits of altruism has also proved difficult. Helping behaviour and its outcomes among species of Malurus are surprisingly diverse, despite similar founding conditions for cooperative breeding. First, species differ in whether help provides fitness benefits, in the recipients of those benefits, and whether benefits are immediate or deferred. Second, species vary greatly in whether females are philopatric and the extent to which female auxiliaries (supernumeraries), when present, provide care. Finally, male auxiliaries are much less sensitive to the needs of the brood than females. In this review we show that these three aspects of helping behaviour lack compelling explanations. We develop hypotheses to explain each phenomenon. Distinguishing among these hypotheses will greatly enhance our understanding of the remarkable social system of Malurus, and inform the study of cooperative breeding and sexual conflict in general. [ABSTRACT FROM AUTHOR]

Birds are commonly sexually promiscuous, which can lead to conflict between the sexes and the evolution of paternity assurance strategies, such as mate guarding. Adaptive explanations for mate guarding have tended to focus on fitness consequences for males, but mate guarding and participation in being guarded is also likely adaptive for females in certain contexts. To better understand the adaptive explanations for mate guarding as well as the observed variation in paternity patterns, it is necessary to explore the relative costs and benefits of guarding (and being guarded) from both the male and female perspective. To investigate these costs and benefits, we conducted an experiment with the Australian zebra finch ( Teniopygia guttata) in which we independently varied the perceived opportunity for each member of a captive breeding pair to engage in extra-pair copulation (EPC) solicitation behavior; as an individual's EPC opportunity increased, the partner's EPC opportunity remained constant. Our results indicate that, for males, mate guarding intensity increases when their female's EPC opportunity increases but decreases when their own (i.e., male) EPC opportunity increases. We did not find evidence of flexible female guarding behavior, but we found that females do not evade their partners more as female EPC opportunity increases. [ABSTRACT FROM AUTHOR]

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Whooping Cranes (Grus americana) are a long-lived, monogamous avian species, yet little documentation of copulatory behavior and timing in relation to egg-laying has occurred in wild populations. We monitored 10 crane pairs in Florida before and during the 2010 breeding season to document copulation timing and pre-and post-copulatory behavior. Monitoring began 111 days before incubation initiation for the first nest of the season. Pairs were observed for 124.62 hrs (̄x = 76.30 min, range = 14-375 min) during 98 observation periods; 17 observation periods occurred on days with precipitation. Three copulations were observed, two by one established pair and another by unpaired individuals. The copulations by the established pair occurred 9 and 18 days before incubation began. The third was an extra-pair copulation, which occurred between a paired female and a lone male, the first documented for the species. No copulations were observed on days with precipitation. We examined flock monitoring accounts from 1999 through 2009 in this non-migratory population; 21 observations of copulations revealed Whooping Cranes copulated up to 62 days before incubation began and between 0510-1345 hrs EST. Our data suggest copulation occurs between early morning and early afternoon and does not appear to be associated with precipitation. [ABSTRACT FROM AUTHOR]

Abstract: Men and women differ in sleep duration and timing of sleeping. Men sleep shorter and are later chronotypes, thus go to bed and get up later than women. This sexual dimorphism in chronotype is most striking between the beginning of puberty and beginning of menopause indicating the possibility of a sexually selected trait. Sleep duration, however, is different between the sexes already before and after the reproductive phase, suggesting a trait that is not under sexual section. In men, the most influential predictor of mating success was extraversion, followed by age, propensity to stay out late and evening orientation. This was confirmed by structural equation modeling showing both, an indirect and a direct fitness benefit of eveningness even when imposing extraversion and age as important predictor variables. As eveningness is related to an array of problematic behaviors, we suggest that it can be viewed as a kind of handicap. [Copyright &y& Elsevier]

Individual behaviors of animals do not evolve separately; they do so in association with other behaviors caused by single shared genetic or physiological constraints and/or favored by selection. Thus, measuring behavioral syndromes-suites of correlated behaviors across different contexts-leads to a better understanding of the adaptive significance of variations in behaviors. However, relatively few studies have examined behavioral syndromes in wild animal populations in changing environments. We investigated a potential behavioral syndrome across antipredator nest defense, territorial defense, chick provisioning, and mating behaviors of male Black-tailed Gulls Larus crassirostris in two successive years under different conspecific territorial intrusion risks and food conditions. Males that presented high levels of antipredator nest defense (aggressive antipredator defenders) against a crow decoy (crows are egg predators) defended their territories against conspecific intruders more frequently than did other males (nonaggressive antipredator defenders), independent of the risk of intrusion. Aggressive antipredator defenders also fed their chicks more frequently than nonaggressive males, but only in a year of low food availability. Taken together, this indicates that males show consistent aggressiveness regardless of breeding context (antipredator and territorial defense), but can regulate food provisioning according to food availability. [ABSTRACT FROM AUTHOR]

Hybridization and genetic introgression can be associated with secondary contact between closely related species. Previous models have examined the ecological and demographic conditions leading to hybridization and introgression, but few have examined the role of behavior. Alternative mating behaviors are common throughout the animal kingdom but have rarely been recognized as a potential mechanism for hybridization. We developed an individual-based genetic model to examine the hypothesis that extra-pair copulations (EPCs) can lead to hybridization and genetic introgression even when assortative mating preferences are intact. Our model showed that female choice, whether pre- or post-copulation, reinforced species boundaries and that hybrids were relatively uncommon when no EPCs occurred. However, when EPCs were introduced into the model, the proportion of hybrids in the population depended on the strength of female mate or sperm choice, the strength of male pursuit of EPCs, and habitat-induced effects on the species composition of the neighborhood. As predicted, male pursuit of EPCs caused extensive introgression, but female preference for conspecific paternity reinforced species differences. Inclusion of mitochondrial markers of species identity revealed significant effects of interspecific and intersexual behavior during EPCs on the direction of introgression. These results suggest that an alternative mating tactic may have major effects on the level of genetic homogenization and can cause local extinction of a species. [ABSTRACT FROM AUTHOR]

The article discusses a study on the preferences in mate choice in relation to reproductive stand and age in Ansell's mole-rates as well as the fidelity of the reproductive animals and their likelihood to engage in extra-pair copulations and abandon their respective partners. The species Fukomys anselli involved in the study were either born in captivity or captured in the field. Three copulations were recorded involving queens and non-reproductive males. It indicates that non-breeding mole-rates of both genders are motivated to mate if there is an opportunity and concludes that the reproductive status is critical for reproductive decisions.

Although functional explanations for female engagement in extra-pair copulation have been studied extensively in birds, little is known about how extra-pair paternity is linked to other fundamental aspects of avian reproduction. However, recent studies indicate that the occurrence of extra-pair offspring may generally decline with laying order, possibly because stimulation by eggs induces incubation, which may suppress female motivation to acquire extra-pair paternity. Here we tested whether experimental inhibition of incubation during the laying phase, induced by the temporary removal of eggs, resulted in increased extra-pair paternity, in concert with a later cessation of laying, in blue tits ( Cyanistes caeruleus). As expected, experimental females showed a more gradual increase in nocturnal incubation duration over the laying phase and produced larger clutches than controls. Moreover, incubation duration on the night after the first egg was laid predicted how extra-pair paternity declined with laying order, with less incubation being associated with more extra-pair offspring among the earliest eggs in the clutch. However, incubation duration on this first night was unrelated to our experimental treatment and independent of final clutch size. Consequently, the observed decline in extra-pair paternity with laying order was unaffected by our manipulation and larger clutches included proportionally fewer extra-pair offspring. We suggest that female physiological state prior to laying, associated with incubation at the onset of laying, determines motivation to acquire extra-pair paternity independent of final clutch size. This decline in proportion of extra-pair offspring with clutch size may be a general pattern within bird species. [ABSTRACT FROM AUTHOR]

Engagement in extra-pair copulations is an example of the abundant conflicting interests between males and females over reproduction. Potential benefits for females and the risk of cuckoldry for males are expected to have important implications on the evolution of parental care. However, whether parents adjust parental care in response to parentage remains unclear. In Eurasian penduline tits Remiz pendulinus, which are small polygamous songbirds, parental care is carried out either by the male or by the female. In addition, one third of clutches is deserted by both male and female. Desertion takes place during the egg-laying phase. Using genotypes of nine microsatellite loci of 443 offspring and 211 adults, we test whether extra-pair paternity predicts parental care. We expect males to be more likely to desert cuckolded broods, whereas we expect females, if they obtain benefits from having multiple sires, to be more likely to care for broods with multiple paternity. Our results suggest that parental care is not adjusted to parentage on an ecological timescale. Furthermore, we found that male attractiveness does not predict cuckoldry, and we found no evidence for indirect benefits for females (i.e., increased growth rates or heterozygosity of extra-pair offspring). We argue that male Eurasian penduline tits may not be able to assess the risk of cuckoldry; thus, a direct association with parental care is unlikely to evolve. However, timing of desertion (i.e., when to desert during the egg-laying phase) may be influenced by the risk of cuckoldry. Future work applying extensive gene sequencing and quantitative genetics is likely to further our understanding of how selection may influence the association between parentage and parental care. [ABSTRACT FROM AUTHOR]

Abstract: Previous studies show that post-hatch oral exposure of zebra finches to estradiol benzoate compromises male fertility, but the basis of the infertility is not clear. In this study, zebra finch nestlings were orally dosed with estradiol benzoate (at 1, 10, or 100nmol/g BW per day, post-hatch days 5 to 11 [EB1, EB10, and EB100, respectively]). EB10 and EB100 males exhibited no significant differences in the frequency of mounting behavior (compared to canola oil [vehicle]-treated controls), when observed for six weeks as adults in communal breeding cages with similarly treated females; EB1 males showed reduced mounting behavior compared to controls (p <0.05). EB- and control-treated adult pairs were subsequently co-housed in a communal breeding trial to determine the extent of parentage outside the established pair-bond. Microsatellite analysis was consistent with EB-treated males having lower success than controls in obtaining paternity outside the established pair-bond. Histological examination of testes revealed dose-related disruption of normal morphology: disrupted basal-to-lumen laminarity of spermatogenesis stages, increased vacuolization within seminiferous tubules, decreased sperm aggregation and decreased spermatid density. Additionally, EB100 and control males were housed individually, implanted with testosterone propionate (TP) and presented with a female 3, 5, 9, and 11days post-implantation for assessment of male sexual behavior. EB-treated, TP-implanted birds showed a slight decrease in mounting and singing behavior on day 5 after implantation; other male courtship behaviors (display, solicitation) were unaffected. Taken together, these results suggest that infertility in male zebra finches resulting from early oral estrogen exposure is more likely due to disrupted testicular morphology than altered sexual behavior. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

The causes of variation in rates of extra-pair paternity among avian populations remain unclear, but could include environmental factors such as breeding density and synchrony. By experimentally manipulating nest site availability, we tested the effects of breeding density on the frequency of extra-pair paternity in eastern bluebirds ( Sialia sialis). We also examined the role of breeding synchrony on extra-pair paternity using natural timing of nests. Microsatellite analysis revealed 34 of 305 nestlings (11.2%) were the result of extra-pair fertilizations; and 21 of 79 broods (26.6%) had at least one extra-pair nestling. Several measures of breeding density had independent effects on extra-pair paternity. First, experimental plot type affected extra-pair paternity, with 28 of 34 (82.4%) extra-pair young from nests in high density areas, and only six (17.6%) from nests in low density areas. Independently of plot type, the number of breeding neighbors within a 320-m radius was a significant predictor of the likelihood of extra-pair paternity at the nest. Extra-pair paternity was associated with temporal factors such as absolute timing of breeding and natural levels of local breeding synchrony, but only in bivariate comparisons. We found a positive interaction between density of neighbors within a 320-m radius and local breeding synchrony; this term reduced the main effects of synchrony and number of neighbors, but not experimental treatment. Our results demonstrate the importance of utilizing multiple aspects of proximity in breeding density analyses and testing for interactions between ecological factors that can influence the behavioral events leading to extra-pair fertilizations. [ABSTRACT FROM AUTHOR]

The article presents a study that evaluates two ecological hypotheses explaining the cluster formation during reproduction of the Blue-black Grassquit or Voltainia jacarina. Study shows that territories were clustered in habitat with more food and a more complex vegetation structure. It is noted that the aggregation of Blue-black Grassquit territories can be associated with habitat heterogeneity.

Parrots are generally considered monogamous, forming strict pairs when breeding. Echo parakeets are unusual in that, although traditional breeding pairs occur, there are also multi-male breeding groups. This raises questions about the potential for extra-pair copulations, Genotype data were obtained from the dominant male and female in eight breeding groups (including three with profiles of attendant auxiliary males) and their 36 offspring. A further 34 offspring were available from eight breeding groups where profiles were available for a single parent. This study utilized four microsatellite genetic markers, originally developed for the African grey parrot. Parentage testing was undertaken using genotype comparisons with the dominant pair within the breeding group as well as auxiliary males where available. Although four markers were insufficient to provide conclusive evidence they do suggest that extra-pair copulation occurs in this species. The echo parakeet is classified as endangered (<500 birds) and understanding its mating system would be valuable in its future conservation. [ABSTRACT FROM AUTHOR]

The article presents a study on copulation duration during courtship which predicts fertility in the Eurasian kestrel called Falco tinnunculus, which was conducted in Spain. The hypothesis was tested in the kestrel by studying the relationship between copulation frequency, duration and variables that are considered indexes of quality in this species. It was found that males having larger clutches showed shorter copulas. No relationship was found between copulation frequency and any of the studied indexes of male quality. Related topics are further discussed including the study methods.

With the availability of highly variable microsatellite loci, many previously elusive aspects of the lives of animals have been revealed. One important finding is that multiple paternity (MP) appears to be somewhat common throughout the metazoa. Frequently, along with the discovery of MP are assertions that it can increase the genetically effective size of the population ( NE). I argue that MP is not likely to have a positive effect on NE because it increases the variance in male reproductive success. Published studies suggesting the contrary have implicitly or explicitly included other changes to the breeding system, and these additions are likely responsible for the presumed increase in NE. [ABSTRACT FROM AUTHOR]

The article examines the impact of food supplementation on the extraterritorial behavior in female Northern Cardinal. It predicts that the females on supplemented territories will spend more time off the territory if the extraterritorial movements function to gain extra-pair matings. It notes the absence of significant difference the home range sizes between the treatment groups.

Abstract: Male genital mutilation (MGM) takes several forms and occurs in about 25% of societies. This behavior has puzzled anthropologists, doctors and theologians for centuries, and presents an evolutionary challenge since it involves dangerous and costly surgery. I suggest that MGM is likely to reduce insemination efficiency, reducing a man''s capacity for extra-pair fertilizations by impairing sperm competition. MGM may therefore represent a hard-to-fake signal of a man''s reduced ability to challenge the paternity of older men who are already married. Men who display this signal of sexual obedience may gain social benefits if married men are selected to offer social trust and investment preferentially to peers who are less threatening to their paternity. Clitoridectomy and vaginal infibulation serve a parallel signaling function in women, increasing a husband''s paternity certainty and garnering his increased investment. Especially in societies where paternity uncertainty and reproductive conflict are high, the social benefits of MGM as a signal may outweigh its costs. This ‘sexual conflict’ hypothesis predicts that MGM should be associated with polygyny, particularly when co-wives reside far apart, and that MGM should reduce the frequency of extramarital sex. MGM rituals should facilitate access to social benefits; they should be highly public, watched mainly by men, and performed by a nonrelative. I found support for these six predictions in two cross-cultural samples. I also examined an alternative hypothesis suggesting that MGM signals group commitment for collective action, particularly inter-societal warfare. Although other forms of male scarification fit this model, the distribution of MGM is not predicted by frequency of inter-societal warfare. [Copyright &y& Elsevier]

Current mating system theory predicts that the number of females breeding in a group will depend on the number of females in the group and the accessibility of unrelated males, whereas the number of males breeding in a group will depend on the ability of males to control access to reproductive females. By combining information on group composition with genetic data, I determined whether breeding patterns in a rock-dwelling rodent, Ctenodactylus gundi, were concordant with these expectations. C. gundi breeding patterns varied from facultative monogamy to uni-male polygyny to multi-male polygyny. The number of reproductive individuals of each sex in a group increased with group size. Whereas communal breeding among related females tended to increase female reproductive success, males breeding in the same group were unrelated to other group members and seemed to compete over access to matings. While some males were assigned offspring from neighboring social groups, most group-living males successfully monopolized the reproduction of females within their group. There was no evidence that females had multiply sired litters, although some bred with alternative males in separate breeding attempts. Although numerous individuals were not assigned as parents or offspring, genetic information enabled me to determine that most unassigned individuals were philopatric group members, whereas only a few were unrelated immigrants into their current social group. Together, these results provide evidence that C. gundi social groups represent fairly distinct reproductive units whose breeding patterns are dependent on group size and composition in accordance with theoretical predictions. [ABSTRACT FROM AUTHOR]