Factors influencing mate guarding and territory defence in the stitchbird (hihi)

Socially monogamous male birds are predicted to maximise their reproductive success by pursuing extra-pair copulations (EPCs) while engaging in anti-cuckoldry behaviour such as mate guarding. In the stitchbird, Notiomystis cincta, high levels of forced EPCs and a high proportion of nestlings resulting from extra- pair fertilisations lead to the prediction that males of this species should exhibit intense paternity guarding behaviours. While studying an isolated stitchbird population on Tiritiri Matangi Island New Zealand (3636'S, 17453'E), I collected daily behavioural data throughout the breeding season from 15 males in 2000/01 and 27 males in 2001/02. In this study, male stitchbirds demonstrated clear paternity guarding by exhibiting: (1) an increased likelihood of being close to their mate during her fertile period, (2) an increased initiation of mate contact during her fertile period, (3) switching from site-specific territorial defence during the pre-fertile period to defending an area centring on the their female partners location during her fertile period, and (4) an increased following of the female to communal feeding sites outside the territory during her fertile period. For polygynous males, mate guarding and territorial defence were conditional on which of their females was fertile. Additional evidence supporting the hypothesis that mate guarding in this species is a form of paternity assurance, rather than protection from harassment, is that males protected their partner from harassment by other stitchbird males but did not intervene when females were harassed by male bellbirds, Anthornis melanura. While mate-guarding intensity in many species is conditional on the stage of female fertility, male stitchbirds also modified their behaviour depending on the location of the female and the rate of intrusions by extra-pair males. Resident males adopted a best-of-a-bad-job tactic when they were unable to locate their female by defending an area around her last known location. Furthermore, when the rate of intrusions by extra-pair males increased they traded-off the area they could defend within their territory against their ability to guard the female. Territory takeovers were uncommon, but when they did occur older males displaced younger males and healthy birds displaced sick ones. Contrary to the prevailing view that mate guarding is a male response to female infidelity, male stitchbirds appear to use mate guarding primarily to prevent paternity losses from forced EPCs. Future assessments of mate guarding function should consider the possibility that mate guarding involves a combination of conflict and co-operation between the sexes.     

Explicit experimental evidence for the effectiveness of proximity as mate-guarding behaviour in reducing extra-pair fertilization in the Seychelles warbler

Extra-pair copulations (EPCs; copulations outside the pair bond) are widespread in birds and may result in extra-pair fertilizations (EPFs). To increase reproductive success, males should not only seek to gain EPFs, but also prevent their own females from gaining EPFs. Although males could reduce the number of EPCs by their mates, this does not necessarily mean that they reduce the number of EPFs; indeed several studies have found no association between EPCs and EPFs. Male Seychelles warblers (Acrocephalus sechellensis) follow their partner closely during the period when the pair female is most receptive (fertile period). We show that males that guarded their mates more closely were less likely to have extra-pair young in their nest. This study on the Seychelles warbler is the first to provide explicit experimental evidence that mate guarding is effective in reducing EPFs. First, in territories where free-living males were induced to stop mate guarding during the pair female's fertile period, extra-pair parentage was higher than in the control group. Second, in the experimental group, the probability of having an extra-pair nestling in the nest was positively associated with the number of days during the fertile period for which mate guarding was artificially stopped. Thus, male mate guarding was effective in reducing the risk of cuckoldry.     

Proximity between the sexes in ring doves: Social bonds or surveillance?

Most bird species are monogamous, and in many instances the male provides a substantial contribution to the care of the young. Traditionally, the initial phase of the relationship between the sexes has been characterized in terms of pair formation and an increasing bond between the sexes. But recent formulations emphasize the role of guarding, surveillance, and other behavioural devices that protect the genetic relationship of the male to the offspring for which he cares. Ring doves were studied to determine whether the details of the relationship during the initial period are consistent with this latter view. Experiment 1 reveals that males remain in close proximity to their mates until the first egg is laid and the fertile period of the female ends; social contact then falls to a low level. Experiment 2 shows that when the female is removed during her fertile period, the male searches and calls more vigorously than does a female when her partner is absent. Finally, Experiment 3 demonstrates that it is visual contact rather than simply proximity that the male maintains during the fertile period of the female. These observations are consonant with the view that males maintain surveillance over their mates, but they do not exclude the possibility that the behaviour patterns might provide other benefits as well.     

Spatial and Temporal Distribution of Song in the Yellowhammer Emberiza citrinella

The temporal and spatial distribution of song was studied in a population of yellowhammers Emberiza citrinella. Song was most frequent during the breeding season, and within the breeding season during the fertile period of both first, second, and replacement clutches. Song activity peaked at sunrise and sunset. During the fertile period most singing took place in the central parts of the territory. Song post heights peaked during the fertile period, and more song posts lacked foliage at that time. Intrusions by male conspecifics peaked in the fertile period and in territories where males sang relatively little. Song activity and mate guarding were strongly positively correlated. Song volume was loud and song was thus apparently used in long-distance communication. These observations are in accordance with a male deterrence hypothesis, suggesting that males sing to deter neighbouring males from trespassing during the fertile period of their mate. A female attraction hypothesis, suggesting that males sing to attract neighbouring females and thereby obtain extra-pair copulations, and a female reproduction hypothesis, suggesting that males sing to start the female reproductive cycle, were partly supported by observations.     

Signaling of Reproductive Status in Captive Female Golden-Headed Lion Tamarins (Leontopithecus chrysomelas)

In species in which paternal care has an important impact on the offspring's fitness, concealment of reproductive status has been proposed as a strategy employed by females to prevent males from practicing desertion and polygamy, which would then lead to monogamous or polyandrous mating systems or both. We investigated whether the female's reproductive status is being concealed in golden-headed lion tamarins, which exhibit extensive paternal care and a mainly monogamous/polyandrous mating system. We used a combination of behavioral observations and endocrine data to determine female reproductive status and to examine changes in sociosexual behaviors over the ovarian cycle and between conceptive and nonconceptive cycles. Females clearly signaled their reproductive status by way of proceptive sexual presenting. Males showed increased frequencies of anogenital sniffing and mounting during the fertile period, indicating that they detected changes in olfactory and behavioral cues emitted by females, and they adjusted their mounting behavior accordingly. Males and females also remained in closer proximity before and during the fertile period, which suggests the existence of mate guarding. We discuss a possible function of behavioral advertisement of reproductive status in shaping the mating system in Leontopithecus chrysomelas.     

OCCURRENCE AND MOVEMENT OF MIGRATORY SPECIES IN RHODESIA AND SOUTHERN AFRICA DURING THE PERIOD 1950-1953

Summary

Seiler, H. W. &; Pr?s-Jones, R. P. 1989. Mate competition, mate guarding, and unusual timing of copulations in the Cape Sugarbird (Promerops cafer). Ostrich 60:159-164.

Focal observations on two breeding pairs of the Cape Sugarbird were undertaken in the Cape Peninsula, South Africa. During the presumed fertile period of the female the male was significantly less likely to become separated from his mate than during other stages of the breeding cycle. This is interpreted as mate paring, which might be triggered by the female well in advance of her actual fertile period. The presumed fertile period was closely accompanied by a sharp increase in territorial intrusions by other males. Copulations were observed only outside the presumed fertile period.     

Decoy presentations as a means to manipulate the risk of extrapair copulation: an experimental study in a semicolonial raptor, the Montagu's harrier (Circus pygargus)

Mate guarding and frequent copulations are two alternative paternity assurance strategies found in birds. In species with intensecourtship feeding, like raptors, the "frequent copulation"strategy is expected because male food provisioning conflictswith mate guarding. We evaluated experimentally the paternityassurance behavior of a semicolonial raptor, the Montagu'sharrier Circus pygargus, using decoy presentations to simulateterritorial intrusions. Breeding pairs were exposed to maleand female decoys at different periods during the female's reproductive cycle. Agonistic responses to decoys were intra-sexual,and the timing and intensity of male attacks toward male decoyssupported responses related to the risk of extrapair copulation(EPC): Male aggression peaked during the presumed fertile periodand almost disappeared after clutch completion. During thefertile period, copulation rate was significantly higher, andcopulations lasted longer, during male decoy presentations than during controls. Males also spent more time close to the femaleduring male decoy presentations compared to controls, bothduring the early prelaying and fertile periods, but not duringincubation. In the fertile period, males also increased presencetime close to the female in the hour following the removal of the male decoy. Conversely, female decoy presentations hadno significant effect on copulatory behavior or male presencetime. These results showed that the risk of EPC can be experimentallymanipulated by the means of decoy presentations, simulatingmale territorial intrusions, and that male Montagu's harriersincrease their short-term copulation frequency and female surveillancewhen they perceive themselves at an increased EPC risk.     

Territoriality as a paternity guard in the European robin, Erithacus rubecula

To investigate the relative importance of paternity defences in the European robin we used behavioural observations, simulated intrusions and temporary male removal experiments. Given that paired males did not increase their mate attendance, copulation rate or territory size during the female's fertile period, the most frequently quoted paternity assurance strategies in birds were absent. However, males with fertile females sang and patrolled their territories more regularly, suggesting that territorial motivation and vigilance were elevated when the risk of cuckoldry was greatest. In addition, there was a significant effect of breeding period on response to simulated intrusions: residents approached and attacked freeze-dried mounts more readily in the fertile period. During 90-min removals of the pair male in the fertile period, neighbours trespassed more frequently relative to prefertile and fertile period controls and appeared to seek copulations with unattended females. When replaced on their territories, males immediately increased both song rate and patrolling rate in comparison with controls. We propose that male robins sing to signal their presence, and increase their territorial vigilance and aggression in the fertile period to protect paternity. Copyright 2000 The Association for the Study of Animal Behaviour.     

Female body odour is a potential cue to ovulation

Human body odours have been reported to influence female mate choice. Women prefer the odours of immunocompatible men and, during their fertile period, judge the body odours of men with symmetrical bodies--which is indicative of genetic quality--as sexy and pleasant. The reproductive success of men largely depends on mating with fertile women, but it is not known whether men can detect a woman's fertile period. We asked women who had regular menstrual cycles and who were not using hormonal contraceptives to wear a T-shirt for three consecutive nights during their late follicular (ovulatory) phase and another T-shirt during the luteal (non-ovulatory) phase of their menstrual cycle. Male raters judged the odours of T-shirts worn during the follicular phase as more pleasant and sexy than odours from T-shirts worn during the luteal phase. The odour differences between the follicular and luteal phases did not dissipate quickly over time as male raters were able to detect and judge follicular phase body odours as more pleasant and sexy than the odours from the luteal phase even after the T-shirts were kept at room temperature for one week. These findings suggest that ovulation may not be concealed and that men could use ovulation-linked odours in their mate selection.     

Female ovarian cycle phase affects the timing of male sexual activity in free-ranging Barbary macaques (Macaca sylvanus) of Gibraltar

Although all macaques have a multimale multifemale mating system, the degree of promiscuity shown by the Barbary macaque is considered to be extreme in terms of both mating frequency and number of mating partners. How mating activity is distributed throughout the female menstrual cycle and whether or not copulations are concentrated around the fertile phase as in other members of the genus is, however, not known. To examine this, we collected data on rates of copulation throughout 29 ovarian cycles from 13 free-ranging females of the Gibraltar Barbary macaque population and related them to the time of ovulation and the female fertile phase as determined from fecal hormone analysis. In addition, patterns of male inspection of females and time spent in consortship, both indicators of female attractivity, were also analyzed. The results indicate that both mating behavior and female attractivity vary predictably with ovarian cycle stage. Rates of copulation were found to increase toward the time of ovulation, with a distinct peak of ejaculatory (but not non-ejaculatory) copulations occurring in the fertile phase. Additionally, we show that frequency of inspection of females by males and time spent in consortship were also highest during the fertile phase and that ejaculatory copulations and male pericopulatory behaviors were significantly correlated with levels of female sex hormones. Our findings indicate that the Barbary macaque shows a mating pattern during the cycle similar to that described for other members of the genus. More importantly, however, our study provides clear evidence that despite an extreme degree of promiscuity Barbary macaque males concentrate their reproductive effort to the fertile phase, implying that they are able to discern this period and that thus timing of ovulation is not concealed from them. Estrogen-related cues appear to be involved in the process of recognition of female reproductive status by males, but the exact nature of these cues and how male Barbary macaques use them remains to be clarified.     

Sociosexual behavior, male mating tactics, and the reproductive cycle of giraffe Giraffa camelopardalis

Female distribution exerts a major impact on male mating tactics. Giraffe cows have a reproductive cycle, and a social system, that should favor a male roaming reproductive tactic. We conducted a 2-year study of female Rothschild's giraffe (G. c. rothschildi) reproductive endocrinology in order to characterize attributes of the reproductive cycle and investigate how female endocrine and behavioral cues influence mating activity. We used non-invasive fecal steroid methods to determine reproductive state among females residing in a herd in a large outdoor enclosure. We found that females had an estrous cycle of 14.7 days and that they regularly had multiple ovarian cycles prior to conception. Adult males were more likely to associate with, and sexually investigate, females when they were cycling than when they were either pregnant or acyclic. During the estrous cycle, male-female proximity and sociosexual behavior were more pronounced during the probable fertile phase than the rest of the cycle. Sexual activity between giraffe coincided with the periovulatory period, with male interest in females peaking during the fertile window in the absence of proceptive behavior by females. We conclude that males detect reliable cues revealing female reproductive status and partition their reproductive effort in response to such cues. We propose that male giraffe adopt a roaming reproductive strategy with their large size, enabling them to search for and mate guard fertile females while minimizing metabolic costs.     

Changes in Song Complexity Correspond to Periods of Female Fertility in Blue Grosbeaks (Guiraca caerulea)

Song complexity is thought to be a sexually selected trait in passerine birds; however, quantifying relevant parameters of song complexity is the first step in testing the theory that song complexity is a sexually selected trait. We show here that blue grosbeak (Guiraca caerulea) males sing a single song type but the properties of that song type vary between renditions. This pattern of song delivery potentially provides females with an opportunity to assess dimensions of song complexity other then repertoire size. Here we characterize song complexity using four measures: (i) element repertoire size, (ii) proportion of distinct song variant, (iii) song versatility, and (iv) syntax consistency. We studied the functional significance of song complexity by comparing measures of song complexity before and after periods of female fertility. We found that male blue grosbeaks sing more song variants, use more versatile arrangements of elements, and maintain more syntax consistency during the fertile period of their social mate than during their social mate's non‐fertile period. These results point to a functional relationship between changes in song complexity and periods of female fertility in this species.     

Kin conflict in seed plants

Kin selection theory proposes that individuals value the reproductive success of relatives at a rate determined by their probability of shared alleles. The theory predicts when the interests of relatives are in accord and when they conflict. Though kin selection arguments have revolutionized the study of animal behavior, they have only recently been applied to plants. Kin selection has already been claimed to explain the formation of endosperm by double fertilization. This is the character that distinguishes angiosperms from gymnosperms. Plant life cycles involve interactions among kinds of relatives not encountered in animals. These interactions should be a fertile field for new applications of theory and the testing of ideas originally developed elsewhere.     

Testosterone Manipulation of Male Attractiveness has no Detectable Effect on Female Home-Range Size and Behavior During the Fertile Period

Female dark‐eyed juncos (Junco hyemalis) are socially monogamous, but they engage in extra‐pair copulations (EPCs). We examined spatial activity and behavior of female juncos during their fertile period to determine whether they engaged in tactics likely to facilitate EPCs and whether any such tactics varied with the attractiveness of their social mates. We manipulated the attractiveness of social mates by implanting experimental males with tubes containing testosterone (T‐males) and control males with empty tubes (C‐males). Previous findings in free‐living juncos showed that females mated to C‐males were more likely to produce extra‐pair young than females mated to T‐males. We radio‐tracked 13 females (eight C‐mated, five T‐mated) for an average of 15 h each over 3 d during their fertile periods. We predicted that C‐mated females, to compensate for the induced relative unattractiveness of their social mates, would foray from their territories to seek EPCs and as a result would have larger home ranges than T‐mated females. Females of both treatment groups made extra‐territorial forays, some of considerable distances, but we observed no EPCs during forays. Further, neighboring T‐ and C‐males frequently made incursions into the home ranges of T‐ and C‐mated females but we saw no EPCs during these incursions. Our ability to detect statistical differences was limited by sample size, but given that constraint, we found no detectable difference in female home‐range size in relation to the treatment of their mates, nor did other female behavior differ according to male treatment. Male behavior was significantly affected by testosterone treatment. C‐males guarded their mates more closely than did T‐males. We conclude that female juncos make extra‐territorial movements during their fertile period without regard to male attractiveness (testosterone treatment), but we found no evidence that these function as a special tactic to gain EPCs.     

Female reproductive signaling, and male mating behavior, in the olive baboon

Baboon sexual swellings are among the largest and most colorful signals displayed by any mammal, and many baboon studies have shown an association between sexual swellings and both female and male sexual behavior. However, the extent to which female behavior and sexual swellings combine to signal the timing of ovulation and the fertile period to males, and the extent to which males use these and other signals when determining patterns of mating behavior, remain key topics of research. Here we assess the social and sexual behavior of both female and male olive baboons with respect to detailed measures of swelling size made from digital photographs, measures of fecal progestogen and estrogen levels, and estimates of the timing of ovulation and the fertile period based on those levels. Female aggression and grooming behavior were unrelated to fecal progestogen and estrogen levels, but there were some significant relationships between these hormonal measures and presenting behaviors. Measures of female behavior collected during the study did not appear to reveal the timing of ovulation or the fertile period. Male consortship behavior was closely tied to fine-scale changes in sexual swelling size, but copulation behavior was not. Copulation behavior of consorting males was, however, linked to the timing of both ovulation and the fertile period, suggesting that males did have knowledge about these timings. Together these results suggest that males used fine-scale swelling size changes when deciding when to consort, but that consorting males did not use fine-scale swelling size changes in deciding when to copulate. We propose that swelling size may advertise the period during which males should consort with females, with other signals available only from closer inspection then used by consorting males to assess the timing of the fertile period more accurately. An important implication of this interpretation is that different males may have access to different signals of ovulation at any one time. Such a system would allow females to offer different males different information simultaneously, perhaps offering a solution to the ‘female dilemma’ of how females can simultaneously assure and confuse paternity in multi-male societies.     

Menstrual cycle variation in women's preferences for the scent of symmetrical men.

Evidence suggests that female sexual preferences change across the menstrual cycle. Women''s extra-pair copulations tend to occur in their most fertile period, whereas their intra-pair copulations tend to be more evenly spread out across the cycle. This pattern is consistent with women preferentially seeking men who evidence phenotypic markers of genetic benefits just before and during ovulation. This study examined whether women''s olfactory preferences for men''s scent would tend to favour the scent of more symmetrical men, most notably during the women''s fertile period. College women sniffed and rated the attractiveness of the scent of 41 T-shirts worn over a period of two nights by different men. Results indicated that normally cycling (non-pill using) women near the peak fertility of their cycle tended to prefer the scent of shirts worn by symmetrical men. Normally ovulating women at low fertility within their cycle, and women using a contraceptive pill, showed no significant preference for either symmetrical or asymmetrical men''s scent. A separate analysis revealed that, within the set of normally cycling women, individual women''s preference for symmetry correlated with their probability of conception, given the actuarial value associated with the day of the cycle they reported at the time they smelled the shirts. Potential sexual selection processes and proximate mechanisms accounting for these findings are discussed.     

Experimentally Elevated Plasma Testosterone Levels Do Not Influence Singing Behaviour of Male Blue Tits (Parus caeruleus) During the Early Breeding Season

Sexual selection theory suggests that females might prefer males on the basis of testosterone (T)‐dependent secondary sexual traits such as song. Correlational studies have linked high plasma T‐levels to high diurnal song output. This has been confirmed in experiments where T‐levels were kept high at times when natural T‐levels have decreased. However, surprisingly little is known about the relation between T‐levels during the early breeding season and song. In many passerine birds males sing at a high rate at dawn early in the breeding season, referred to as the dawn chorus. In blue tits (Parus caeruleus), the dawn chorus coincides with the fertile period of the female, whereas diurnal song occurs throughout the breeding season. Previous studies on blue tits showed that characteristics of the dawn chorus correlate with male reproductive success. We experimentally elevated plasma T‐levels in male blue tits during the pre‐fertile and fertile period. Our aim was to test whether increased plasma T‐levels affect dawn song characteristics and increase the amount of diurnal song. Although T‐implants successfully raised circulating T‐levels, we did not find any difference between T‐ and control males in temporal performance measures of dawn song or in diurnal song output. Our results suggest that either there is no direct causal link between song output or quality and individual T‐levels, or experimental manipulations of T‐levels using implants do not permit detection of such effects during the early breeding season. Although we cannot exclude that individual T‐levels are causally linked to other (e.g. structural) song parameters, our results cast doubt on T‐dependence as the mechanisms that enforces honesty on song as a sexually selected trait.     

Seasonal patterns of singing in the willow warbler: evidence against the fertility announcement hypothesis

Males of many bird species use a variety of behaviour patterns that reduce their chances of being cuckolded. The 'fertility announcement' hypothesis (M?ller 1991, American Naturalist, 138, 994-1014) proposes that song might be one such paternity guard. According to this hypothesis, paired males would announce their female's fertile status by singing. This has been interpreted as an honest signalling, evolutionarily stable strategy. Contrary to the predictions of this hypothesis, male willow warblers, Phylloscopus trochilus, sang very little when females were fertile. Intrusions by other males in the fertile period were not less common when males sang at higher rates. Mate guarding and singing are best interpreted as two conflicting behaviours during this period, the former being directed to the fertile female and the latter to attracting a second female, or an extrapair female. A survey of recent studies suggests that, in most passerine species studied, males do not sing during the fertile period of their females. The different conclusions of M?ller (1991) are probably due to his use of population-wide estimates of the timing of singing behaviour and egg laying. Breeding asynchronies within populations would be responsible for the apparent matching between the peaks of singing activity and fertility. Copyright 1999 The Association for the Study of Animal Behaviour.     

Intersexual conflict across women's ovulatory cycle

A growing literature shows that the features women find particularly attractive in men vary across the ovulatory cycle. Women furthermore appear to more frequently report attraction to men other than primary partners when they are fertile in their cycle than in the infertile luteal phase. Previous studies have shown that men are more vigilant of or attentive to their primary partners during the fertile phase compared to the luteal phase. This study had several aims: First, to replicate and extend previous findings concerning men's vigilance of partners using male as well as female reports of men's behavior; second, to examine changes in women's behavior toward partners across the cycle; third, to examine ways in which women resist men's attempts to mate-guard across the cycle. Results indicate that (a) men are particularly self-assertive toward partners when their partners are fertile; (b) similarly, women are especially self-assertive toward partners when they are fertile; (c) women report engaging in more behaviors that resist male vigilance and mate guarding when they are fertile, especially in ways that are unobservable to male partners; and (d) these effects are especially strong when women themselves report greater attraction to men other than partners when they are fertile, compared to the luteal phase.     

The transition from vegetative to fertile tissue in Fucus vesiculosus

At various stages of receptacle development, segments of Fucus vesiculosus thallus subtending the fertile tips have been grown in culture. At the times of gamete maturation and gamete shedding a number of both reproductive and vegetative branches are regenerated from the wound callus. This is the only region of the Fucus thallus which has been found capable of regenerating fertile receptacles. The effects of a number of growth regulatory substances were studied. 1-naphthoxyacetic acid stimulated budding but no substance increased the proportion of fertile branches. Extracts prepared from mature receptacles did not induce the regeneration of fertile branches from vegetative thallus, but they markedly inhibited the regeneration of any branches. Subsequent estimations of the growth regulatory substances in the receptacles showed that there was a marked increase in growth inhibitors during gamete development. Growth stimulatory substances were also present but these were masked in crude extracts by the amount of inhibitors.