Receptivity of female Neohelice granulata (Brachyura, Varunidae): different strategies to maximize their reproductive success in contrasting habitats

The extent of the receptive period may determine the mating strategies employed by female crabs to obtain mates. Here, we studied the receptivity of female Neohelice granulata (Dana, 1851) in the laboratory, including the form of the vulvae and the anatomy of the seminal receptacle (SR). We examined the factors that influence the duration of receptivity by comparing two populations inhabiting contrasting habitats: Mar Chiquita Coastal lagoon (MCL), which is an oligo-polyhaline estuary, and San Antonio Oeste (SAO), which is an eu-hyperhaline marine bay. Non-receptive females have immobile vulva opercula, while receptive females have mobile opercula. Histological sections of the SR showed that the degree of epithelium secretions was associated with the receptive stage of females, and they may be involved in the maintenance of viable sperm and in the dehiscence of spermatophores. The existence of a special tissue at the junction of the oviduct and the SR was described and proposed as an internal mechanism influencing the timing of ovulation. The duration of receptivity was dependent on the SR load and the capacity to lay eggs. Thus, females with empty SR exhibited longer receptivity and did not lay eggs, while those with full SR exhibited shorter receptivity and always laid eggs. Interpopulation differences showed that females from SAO had shorter receptivity and heavier SR and laid eggs more frequently than females from MCL. Based on our results, we suggest that N. granulata females can adjust the duration of their receptivity and control the moment of fertilization according to different internal mechanisms related to the morphology of the vulvae, the fullness of the SR and anatomical attributes of the SR. An important consequence of this control is greater sperm competition. The extent of the receptive period and the number of times that a female could become receptive in a single reproductive season may also depend on the habitat characteristics.     

Reproductive activity of ruffed lemurs (Varecia variegata variegata) in a Madagascar rain forest

Mating activity was observed during four breeding seasons in two groups of black and white ruffed lemurs (Varecia variegata variegata) living in lowland rain forest on Nosy Mangabe island, Madagascar. The onset of the May-July breeding season was signalled by behavioral changes in adult males. Males made forays outside their usual home ranges, were more aggressive to other males, and performed appetitive and other sex-specific behaviors more frequently. Females showed receptive and proceptive behaviors during a 1-2 day behavioral estrus. Ruffed lemurs mated monogamously, polyandrously, and polygynously. These observations do not support previous assertions that they live only in monogamous families. Limited evidence suggests females exercised mate choice and may have preferred familiar males. © 1993 Wiley-Liss, Inc.     

Differences in potential reproductive rates of male and female seahorses related to courtship roles

Dwarf seahorses, Hippocampus zosterae (Syngnathidae), are distinguished by extreme morphological specialization for paternal care, the formation of monogamous pair bonds and mating repeatedly over the course of a breeding season. To determine the potential reproductive rates of male and female dwarf seahorses, we measured (1) the maximum number of offspring produced per breeding cycle when sexually receptive mates were unlimited, and (2) the relative time each sex was unavailable for mating ('time out'). We paired sexually isolated males and females with sexually receptive partners and observed them from the day of introduction through to copulation, to determine the length of time it takes each sex to prepare to mate. We conducted additional experiments to determine the length of gestation, which when added to the time needed to prepare to mate and copulate gives an estimate of total reproductive cycle duration, T. We estimated potential reproductive rate by dividing the mean number of offspring produced per breeding cycle by the duration of the breeding cycle (T). We estimated reproductive 'time out' by identifying the period of time males and females were physiologically capable of mating ('time in', S) and subtracting time S from time T. When provided with sexually receptive partners, females took 2 days longer than males to complete courtship and copulation, but neither males nor females remated during gestation. Therefore, males could potentially produce 17% more offspring than females over the course of one breeding season. Females had reproductive 'times out' 1.2 times longer than did males, as they were only capable of mating during the 4 h directly preceding copulation. Thus, H. zosterae males have higher potential reproductive rates and shorter reproductive 'times out' compared with H. zosterae females. These results and previous work indicating that seahorses display traditional courtship roles support the prediction that the sex having the higher potential reproductive rate, or equivalently, the shorter 'time out', will compete more intensely for access to the opposite sex. Copyright 2000 The Association for the Study of Animal Behaviour.     

Mating status regulates post‐mating refractory period in Striacosta albicosta females

In polyandrous insect species, males may transfer substances to reduce sperm competition by affecting female sexual receptivity. In this study, we determined the incidence of polyandry in females of Western bean cutworm (WBC), Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), and investigated the influence of both previous female and male mating history on the duration of mating, the female refractory period, and subsequent calling behavior of females under controlled laboratory conditions. The mating status of WBC males influenced mating duration, with copulations involving previously mated males taking longer, possibly related to the time required to produce an ejaculate. The duration of the female refractory period and the onset time of recalling during the scotophase were both affected by female mating history, but not by that of the males. Females had a shorter refractory period and resumed calling activity earlier after their second and third matings than after their first mating. The earlier onset of calling by previously mated females could reduce competition with virgin females and their shorter refractory period could explain the high incidence of polyandry observed in nature.     

Female Sexual Interference in the Smooth Newt,Triturus vulgaris vulgaris

Competition between unmated females for males was observed in the smooth newt, T. vulgaris, during the early part of the breeding season. Females interfered at the spermatophore-transfer stage of courtship, preventing a rival female from picking up the sperm mass. Interference often resulted in the rival female abandoning the courtship encounter. In many of the encounters (70%), the interfering female was inseminated. However, interference between females was not observed after the commencement of ovulation. By contrast, the incidence of sexual interference between males was low during the preovulatory period and increased significantly post-ovulation. Sexual interference in newts and salamanders has previously only been observed between males. During the greater part of the breeding season, when females are ovipositing, eggs are the limiting resource and males compete for access to receptive females. However, this study suggests that early in the breeding season, prior to commencement of ovulation, the limiting resource may temporarily be sperm, due to the physiological constraint of spermatophore production. This may lead to female competition for mates.     

Size-related mating and mate guarding in the orb-web spiderNephila clavata (Araneae,Araneidae)

The orb-web spiderNephila clavata satisfies three conditions for assortative mating proposed by Ridley (The Explanation of Organic Diversity. The Comparative Method and Adaptations for Mating, Clarendon, Oxford, 1983); (1) a large male advantage in male-male competition, (2) a correlation between female size and fecundity, and (3) a long pairing duration. To test Ridley's hypothesis, size assortative mating and guarding were examined in the field. When data were pooled over time, assortative mating was found but this was due to temporal covariation of body sizes of males and receptive females. After controlling for the effect of time, size assortative guarding was not detected, although females guarded by males were larger than those not guarded in the early breeding season. Possible reasons for the absence of size assortative guarding were discussed.     

The breeding ecology of Cancer gracilis (Crustacea: Decapoda: Cancridae) and the mating systems of cancrid crabs

Brachyuran crabs in the family Cancridae are found in a variety of habitats, ranging from 'open' sandy or muddy grounds to 'structured' rocky bottoms rich in refuge space. Cancer gracilis Dana inhabits shallow open habitats in the north-east Pacific Ocean. Females in all reproductive conditions aggregate in relatively small areas, where mating activity appears most intense. Maximum mating activity was observed towards the end of the spawning/hatching season (August). Females play an active role in mating, often initiating interactions with the prospective male partner. Mating in the field was non-assortative with respect to size. There was no indication of direct mate choice by either males or females; resolution of male-male competitive interactions was size-based. Males below minimum mating size (77 mm carapace width) had spermatophores in the vas deferens but did not react to receptive females.
Sperm competition is likely because sperm can be retained across moults and multiple copulations are possible within a receptive period. Female spermathecae are of the 'ventral' type (contrary to what has been indicated for cancrids), and during intercourse are beyond the reach of male gonopods. Mechanisms to exclude competing sperm include male-produced sperm plugs and post-copulatory mate guarding.
Results are discussed in the context of the 'structured-to-open' habitat gradient, which may underlay much of the diversity in cancrid reproductive ecology. We argue that, by comparison with C. magister (a larger size sympatric species also found in open habitats), (1) reproductive asynchrony and female gregariousness in C. gracilis increase the environmental potential for polygyny, resulting in a female defence polygynous mating system, and (2) reproductive asynchrony inflates the operational sex ratio, leading to stronger sexual selection.     

Factors affecting female sexual receptivity in the planthopper, Prokelisia dolus

Abstract. The mating system of Prokelisia dolus Wilson (Homoptera: Delphacidae) was characterized by determining: if males and females multiply mate; when transitions occur in female sexual receptivity, what triggers sexual refractoriness; and what behaviours characterize unreceptive virgins, receptive virgins, and unreceptive mated females. Males copulated with up to six females in less than 1 h, but completely inseminate, on average, only the first four females. Females rarely mated more than once, unless males were depleted of sperm due to previous copulations or if copulation was interrupted (if duration was<2 min). Male and female calling was associated (100% and 91%, respectively) with sexual receptivity and resultant matings. The transition from unreceptive virgin to receptive (calling) mature virgin occurred 48 h posteclosion, and all were mated by day 4. Females that were sexually immature and those completely inseminated did not call. Rejection of males by females included walking away from approaching males (65%), female kicking (7%), and abdominal lifting (5%). Rejection of males was observed by immature, mature and calling, and mated females. Sexual refractoriness was not triggered by acoustic and visual stimuli or mechanical stimulation of genitalia. Refractoriness was also not triggered by reception of small quantities of sperm because some females laid a few viable eggs yet calling was not terminated. Sexual refractoriness was activated by a substance in the ejaculate as demonstrated by injection into the haemocoel of male accessory glands or testes and homogenates of seminal vesicles. This is the first study that documents the role of male ejaculate in inhibiting female sexual receptivity in Hemiptera (Homoptera).     

The sexual strategy of the central long-toed salamander, Ambystoma macrodactylum columbianum, in south-eastern Washington

The sexual strategies of salamanders are largely'unobservable'owing to the low visibility typical of their preferred breeding habitats. We conducted both field and laboratory studies to investigate the sexual strategy of the North American central long-toed salamander, Ambystoma macrodactylum columbianum. Capture-recapture and cohort-marking of salamanders at an aquatic breeding site indicated that males arrive before females and remain in the water for longer periods of time (measured in weeks, rather than days as for females). We estimate that the overall duration of the breeding season is short, three weeks or less. Courtship between single males and females is characterized by repeated bouts of axillary amplexus, separated by multiple episodes of spermatophore deposition. Amplectant males provide females with considerable tactile stimulation in the form of head-rubbing. Unpaired males attempt to displace amplectant males from their partners by wrestling with them. In addition, unpaired males appear to interfere in ongoing courtship encounters during the spermatophore deposition stage, perhaps attempting to 'steal'inseminations. We suggest that explosive scramble-competition polygyny best describes the mating system of A. m. columbianum. Operational sex ratios are probably male-biased throughout the short breeding season, leading to intense competition among males for mates. Mate choice (by either sex) probably is of little importance as a determinant of mating success.     

Further observations on estrus and ovulation in woodchucks (Marmota monax) in captivity.

The woodchuck is a seasonally breeding sciurid rodent. Female woodchucks are monoestrous and, when isolated from males, remain in a prolonged period of estrus characterized by a clear predominance of cornified cells in the vaginal smear. This study was designed to characterize relationships between the degree of vaginal cornification and sexual receptivity, and to study ovulation and related phenomena of this species in captivity. Fourteen individually caged adult females, maintained under standard laboratory conditions for 9-23 mo, were used in this investigation. Females exhibiting predominantly (67-97%) cornified smears were always receptive, regardless of the time interval from the onset of estrus, and mated within 24 h of pairing. Mated females allowed to complete pregnancy gave birth to live pups 30-32 days later. Litter size ranged from 3-7 pups. Serum progesterone (P) levels increased to approximately 2 ng/ml during the first week of pregnancy and greater than 5 ng/ml during the second and third weeks of pregnancy. Serum estradiol (E2) levels were elevated during the first week of pregnancy and began to decline thereafter. Examination of ovarian serial sections revealed that ovulation took place between 20 and 32 h after copulation. Serum levels increased significantly (4-fold) after ovulation (1.2 +/- 0.3 vs. 0.3 +/- 0.01 ng/ml). However, the circulating levels of E2 remained unchanged between the periods before (53 +/- 1 pg/ml) and after ovulation (60 +/- 3 pg/ml). Ovulation was not simultaneous in all mature follicles.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sex‐dependent response of primary moult to simulated time constraints in the rock sparrow Petronia petronia

There is growing evidence that moult speed affects plumage quality. In many bird species, males and females differ in terms of breeding effort, survival expectation and the relationship between fitness and plumage quality. Consequently, differences in moult strategies between the sexes can be expected. The aim of this study was to assess whether, under simulated time constraints and with no parental investment in the previous breeding season, males and females differed in: a) timing and duration of primary moult, b) growth rates of individual primary feathers, and c) number of concurrently growing feathers. We investigated the effect of time constraints generated by a treatment consisting of two decreasing photoperiods (slow changing photoperiod, SCP=2 min day^?1 and fast changing photoperiod, FCP=8 min day^?1) on the primary post‐nuptial moult of captive rock sparrows Petronia petronia. Females started to moult on average 14 and 15 days later than males in both experimental groups. Primary moult duration was 10 (FCP) and 24 (SCP) days longer in males than in females, and, within sex, 34 (females) and 48 (males) days longer in SCP birds than in FCP ones. Females renewed a larger number of primaries simultaneously (5.7% in FCP and 12.8% in SCP) and had a higher total daily feather mass grown (9.9% in FCP and 22.4% in SCP), even though daily growth rates of individual primaries did not differ between sexes. As a result, males and females completed their primary moult at the same time within treatment. The observed differences in timing, duration and energy allocation for primary moult between the sexes probably have a genetic basis, as birds did not engage in reproduction during the preceding breeding season.     

Age-related changes in plasma oestrogen concentration, behavioural responsiveness to oestrogen, and reproductive success in female gray-tailed voles, Microtus canicaudus

Age-related increases in the incidence of vaginal cornification were associated with increases in the reproductive success of female gray-tailed voles previously isolated from males. The pregnancy rate of females first paired with males at 30-50 days of age was significantly lower than that of females first paired at 90-120 or 150-200 days of age. The improvement was due to increases in propensities to display receptive behaviours and decreases in the incidence of sterile matings. Although plasma oestrogen concentrations increased with age and were higher in receptive than unreceptive females, plasma oestrogen values alone did not account completely for differences in receptive behaviours amongst females of different ages. Females ovariectomized at 30-50 days of age rarely displayed receptive behaviours when treated with large doses of oestradiol benzoate, whereas nearly all females similarly treated were receptive if ovariectomies were performed between 150 and 200 days of age. The receptivity rate of females ovariectomized between 90 and 150 days was intermediate between the rates of the other two groups.     

Variation in fecal testosterone levels, inter-male aggression, dominance rank and age during mating and post-mating periods in wild adult male ring-tailed lemurs (Lemur catta)

In primate species exhibiting seasonal reproduction, patterns of testosterone excretion in adult males are variable: in some species, peaks correlate with female receptivity periods and heightened male-male aggression over access to estrous females, in others, neither heightened aggression nor marked elevations in testosterone have been noted. In this study, we examined mean fecal testosterone ( f T) levels and intermale aggression in wild adult male ring-tailed lemurs residing in three groups at Beza Mahafaly Reserve, Madagascar. Results obtained from mating and post-mating season 2003 were compared to test Wingfield et al. [1990. Am Nat 136:829-846] "challenge hypothesis", which predicts a strong positive relationship between male testosterone levels and male-male competition for access to receptive females during breeding season. f T levels and rates of intermale aggression were significantly higher during mating season compared to the post-mating period. Mean f T levels and aggression rates were also higher in the first half of the mating season compared with the second half. Number of males in a group affected rates of intermale agonism, but not mean f T levels. The highest-ranking males in two of the groups exhibited higher mean f T levels than did lower-ranking males, and young males exhibited lower f T levels compared to prime-aged and old males. In the post-mating period, mean male f T levels did not differ between groups, nor were there rank or age effects. Thus, although male testosterone levels rose in relation to mating and heightened male-male aggression, f T levels fell to baseline breeding levels shortly after the early mating period, and to baseline non-breeding levels immediately after mating season had ended, offsetting the high cost of maintaining both high testosterone and high levels of male-male aggression in the early breeding period.     

Males of the seed bug Togo hemipterus (Heteroptera: Lygaeidae) use accessory gland substances to inhibit remating by females

In species in which females mate repeatedly, males can adopt several strategies to reduce the risk of sperm competition with future males. The refractory period of females significantly increased as the mating duration increased in the seed bug Togo hemipterus (Heteroptera: Lygaeidae). To elucidate the mechanisms by which mated females are inhibited from remating, we investigated the effects of male-derived substances on the inhibition of mating receptivity of virgin females by injecting the substances into their abdomens. The length of time from injection to mating in virgin females was significantly longer for females injected with accessory gland B solution than for those injected with seminal vesicle, accessory gland A, or control solutions. This is the first report showing that heteropteran males inhibit female remating by using substances from an accessory gland. We discuss and consider the adoption and evolution of this strategy by T. hemipterus males by focusing on female genitalia structures, oviposition habit, and paternity and comparing these traits with those of other heteropterids.     

Competing for last place: Mating behaviour in a pill-box crab, Halicarcinus cookii (Brachyura: Hymenosomatidae)

The mating strategy of Halicarcinus cookii was investigated to ascertain how males maximised their fitness through mate choice. An intertidal population at Kaikoura, New Zealand, was dominated by mature crabs of both sexes in summer and by immature crabs in the colder months. More than 95% of mature females were ovigerous with early stage and late stage broods found in almost every month, indicating that egg production and larval release is continuous. The operational sex ratio was less than 1 male/female in summer, but often more than 1.0 in the colder months. The gonosomatic index increased along with brood development so that as soon as zoeae were released, the next clutch of eggs was ready to be fertilised. Males searched for receptive females and began pre-copulatory mate guarding without any courtship display. They mated preferentially with late stage or non-ovigerous females: copulation duration was longest for stage 5 females as was post-copulatory guarding (mean 18.3 h). Late stage females were up to 14% of the female population. Mate attraction seems to be the result of an ovarian signal rather than from the developing brood. Manipulation of the sex ratio had effects upon copulation duration and post-copulatory guarding: presence of a rival male increased duration of guarding. Females showed precocious mating in the penultimate instar and were able to lay fertilised eggs after their pubertal moult in the absence of males. H. cookii females have many mates, but males attempt to ensure paternity by preferentially pursuing mature females close to egg laying and by guarding these females after copulation. These behaviours are all elements of a competitive strategy to ensure that a male loses (not wins) the race to copulate because females have a ventral seminal receptacle, giving sperm precedence to the last male to mate. Male mating behaviour is a consequence and evolutionary response to female morphology.     

Chromosomal Polymorphism and Female Receptivity in a Natural Population of DROSOPHILA PERSIMILIS

In a natural population of Drosophila persimilis (McDonald Ranch, Napa Valley, California), KL and MD chromosomal arrangement frequencies undergo a seasonal cycle, with MD common in spring and KL common in summer. Samples collected from spring and summer provided isofemale strains established as homozygous KL and MD pairs (kinlines) with each pair derived from a single heterokaryotype wild progenitor. Haploid doses of chromosomes 2 and 4 were controlled by marker-cross derivations of kinlines. Percentage onset of female receptivity was measured from cultures at 25° and at 15°, using ten kinlines from spring and nine from summer collections, with fast-mating hybrid males as standard testers. Mating tests consisted of 20 tester males x 20 females of specific age, karyotype, and kinline observed for 30 min. At 25° females became receptive at 48 hr after eclosion: parental line (KL_i/KL_i and MD_i/MD_i) females were approximately equal at 55 to 60% receptive, while among hybrids, MD_i/MD_j homokaryotype females were significantly less receptive (68%) than all other outbred combinations (73 to 77%). At 15°, females became receptive at four days of age, with increases on the fifth and sixth days: both parental line and outbred MD/MD females were significantly more receptive (28% at four days and 62% at six days) than all heterokaryotype females (20 to 26% at four days and 55 to 59% at six days), which in turn were more receptive than KL/KL parental and outbred females (10% at four days and 40% at six days). Heterosis was expressed at 25°, but not at 15°. Thus, dominance for female receptivity was temperature dependent. Females polymorphic for these third chromosomal karyotypes possess differential temperature sensitivity for onset of receptivity and are likely to contribute in a significant way to the observed seasonal frequency cycle in the natural population from which they have been derived.     

Interference competition among burying beetles (Silphidae, Nicrophorus)

Abstract. 1. This study investigated the impact of intraspecific and interspecific competition on the reproductive success of a biparental burying beetle, Nicrophorus defodiens Mannerheim.
2. Marked pairs or single females were placed on small and large mouse carcasses in the field in 1985 and 1986. Carcasses were exhumed after 9–10 days to determine the identity of the resident adult(s) and the production of young.
3. Competition was assessed by the prevalence of takeovers by intruders (unmarked adults). For N.defodiens , after the initial colonization of the carcass, interspecific competition from larger N.orbicollis Say and N.sayi Laporte was substantial and more intense than intraspecific competition. Competition was also greater in the middle of the breeding season and on large as opposed to small carcasses.
4. Successful takeovers resulted in the expulsion of the prior resident(s), killing of any offspring present on the carcass, and oviposition of a new clutch by the intruder.
5. Females aided by males were more likely than single females to avoid takeovers but did not produce larger broods or larvae of larger mass.
6. An additional laboratory experiment in 1985 and a field experiment in 1986 suggest that N.defodiens is able to reproduce on very small carcasses despite intense heterospecific activity.     

Sexual receptivity of Anastrepha obliqua (Diptera: Tephritidae) wild females affected by nutrition and egg load

The influence of feeding, egg load and stage of ovarian development on the sexual receptivity of some insect species has been reported. This work investigated the effects of different brewer's yeast concentrations in the diet offered to females of West Indian fruit fly, Anastrepha obliqua, on their sexual receptivity. Wild females were fed on artificial diets containing 2.0 g brewer's yeast per 100 mL of water (low‐yeast diet, LY diet), 6.5 g yeast per 100 mL of water (high‐yeast diet, HY diet) or only sucrose (Su diet) and then placed with the males. Female sexual receptivity tests were carried out in acrylic boxes in the laboratory under controlled conditions (temperature, humidity and light). Females fed on the HY diet were more sexually receptive to male courtship than the other females. Additionally, when fed on the same diet (HY diet), those females with higher egg load were more sexually receptive. The data suggest that the ingestion of a protein source is essential for increasing sexual receptivity and that egg load is the most important factor affecting sexual receptivity of A. obliqua females.     

Sexual receptivity and age in Glossina pallidipes Austen (Dipt., Glossinidae)

The recent success of the sterile insect technique (SIT) in eradicating Glossina austeni from Zanzibar has stimulated interest in applying this technology to control Glossina pallidipes. However, little is known about the mating behaviour of this species in relation to the development and implementation of an effective SIT programme. The effect of age on male and female receptivity to mating was evaluated together with copulation duration, sperm transfer and the growth of the accessory gland and follicle A in males and females, respectively. Females and males reached their optimal sexual receptivity 9–13 days after emergence. Mean copulation duration was 20–30 min for mature males and females. The growth of follicle A and the accessory gland (apical body) was a function of age of females and males, respectively. Ovulation was not observed in virgin females up to 15 days of age whereas mated females ovulated by day 9. Males aged 7–15 days were equally effective in inseminating. Cages of males and females of different ages were set up to monitor puparial production in relation to optimization of mass rearing. The results are discussed in relation to the development of an efficient mass rearing protocol for this species and an optimal release strategy for sterile males.     

Reproductive Behavior of Female Propithecus verreauxi at Beza Mahafaly,Madagascar

Prosimian and anthropoid females are generally thought to have divergent reproductive patterns, characterized by circumscribed and situation-dependent receptivity. This dichotomy underpins the traditional view that nonreproductive mating serves a social function in anthropoid females, distinguishing them from prosimians which, like most other mammals, mate only when conception is most probable. Circumscribed estrous cycles differ from anthropoid menstrual cycles by the presence of menstruation, and greater flexibility in timing and longer duration of receptivity in the latter. The degree to which sexual behavior is tightly synchronized to periovulatory events in Propithecus verreauxi was assessed via the behavioral, hormonal, and social correlates of reproduction in a free-ranging population. I collected data from two social groups before and during the 1990–1991 and 1991–1992 breeding seasons at Beza Mahafaly, Madagascar. I also conducted 644 focal-animal hours and collected 485 fecal samples from five marked females in the Vaovao and Vavy Masiaka social groups. Estrus was behaviorally characterized by 0.5–96-h periods of receptivity when females were motivated and willing to mate, the latter not always coincident with periovulatory events. Females exhibited age- and rank-related asynchronous receptivity, and in some cases, periovulatory synchrony within groups. Sifaka were not pair-bonded. Most females mated with multiple males, temporally ordering partners based on male residence and age. Mating was limited by male mate-guarding and sexual aggression by males, female mate competition, and aversions to mating with certain partners. It was facilitated by surreptitious copulations, positive mate choice, and the availability of non-resident mating partners.