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PubMed1998

Do female pigeons trade pair copulations for protection?

Male pigeons, Columba livia, employ intense mate guarding and frequent copulation apparently as strategies to ensure their paternity. The aim of this study was to investigate the benefits to females of mate guarding by males and frequent copulation. Field observations showed that females initiated the majority of copulations and females that solicited copulations more frequently were guarded more closely by their partner. Experimental removal of guarding male partners showed that: (1) unguarded, fertile females suffered increased harassment from extrapair males which reduced their foraging efficiency; and (2) unguarded, fertile females did not seek copulations with extrapair males. Various explanations for frequent pair copulation initiated by females are discussed and we conclude that female pigeons trade pair copulations for protection (mate guarding) against sexual harassment from other males. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed2005

Comparison of behavioral sequence of copulation between chimpanzees and bonobos.

We compared sex differences in behaviors leading to copulation of chimpanzees (Pan troglodytes) in the Kalinzu Forest, Uganda with those of bonobos (Pan paniscus) at Wamba, D.R. Congo, using the same definition. Female chimpanzees were more likely to initiate copulation than female bonobos. While most of copulations (96%) were initiated by males in bonobos, among chimpanzees only 63% of copulations were initiated by males. Female bonobos initiated an interaction leading to copulation when males approached them within a short distance. On the other hand, both male and female chimpanzees initiated behavior at a longer distance. Higher proceptivity and a higher copulation rate during the maximal swelling period of female chimpanzees might suggest that they gain greater benefits from a high frequency of copulations than do female bonobos.

Animals↗

PubMed1989

Failure of fertilization following abbreviated copulation in the ferret (Mustela putorius furo).

In the first experiment, copulations in 10 domestic ferrets were interrupted 5 minutes after penetration. Ten control females were bred without interruption to the same males. Both control and experimental animals were rebred in the same manner to the same males 24 hours later. Sperm were present in all postcoital washes. We allowed all females from the first experiment to proceed to their expected date of parturition. All females who had been interrupted during copulation failed to conceive, whereas all controls produced litters. In a second experiment, the same procedure was followed; however, in this experiment, ferret oviducts and uteri were flushed 10 days after copulation. Nine control females (one failed to ovulate) averaged 5.2 blastocysts (range 2-10; S.D. = 5.8) per animal. Of nine interrupted copulation ferrets (one failed to ovulate), only one animal produced a single blastocyst. The interrupted copulation group averaged 4.4 unfertilized eggs (range 2-10; S.D. = 5.0) per female. Although ferrets ovulated during short copulations, those eggs are not likely to be fertilized.

Animals↗

PubMed2006

Non-reproductive copulation behavior among Tibetan macaques (Macaca thibetana) at Huangshan, China.

Non-reproductive copulation, which takes place outside of the mating season and does not result in conception and birth, was studied in a free-ranging group of Tibetan monkeys (Macaca thibetana) at Mt. Huangshan, China, in the birth seasons of 1992 and 1997. We employed all occurrence and focal animal samplings to record sexual and related behaviors and affiliation interactions, respectively. Compared with sexual behavior in mating season, non-reproductive copulation occurred at a lower frequency, with less frequent ejaculation, less harassment, shorter mount duration, and an absence of pause with vocalization. It often took place in a situation in which non-lactating females were involved in social conflict or approached males for mating. Neither pregnant nor lactating females were observed to mate in the birth seasons. Copulation during the birth season did not increase a sexually receptive female's delivery the next year, nor was it associated with increased proximity, grooming, or agonistic aid for the mating pair. However, copulated pairs spent more time co-feeding, presumably reflecting an increased tolerance on the part of the male. Adolescent males, who rarely copulated in the mating season, engaged in mating activity in birth seasons as well. Therefore, though birth-season copulation had no reproductive functions, it may have fulfilled social functions for females, such as post-aggression appeasing by males or gaining access to resources. This also offered good opportunities for adolescent males and females to develop their sexual skills for later competition.

Animals↗

PubMed1989

Testosterone implanted in the preoptic area of male Japanese quail must be aromatized to activate copulation.

Intracranial implantation of minute pellets of gonadal steroids was combined with aromatase inhibitor treatment to determine if aromatization within the preoptic area (POA) is necessary for androgens to activate sexual behavior in the Japanese quail (Coturnix japonica). In this species, implantation of pellets of testosterone propionate (TP) or estradiol benzoate (EB) in the POA of castrated males restores male-typical copulatory behavior. In Experiment 1, adult male castrated quail were implanted intracranially with 200-micrograms pellets of equimolar mixtures of crystalline TP + cholesterol (CHOL), TP + 1,4,6-androstatriene-3,17-dione (ATD, an aromatase inhibitor), EB + ATD, or CHOL and behavior-tested with intact males and females. Copulation was stimulated by POA implants containing TP or EB (three of six CHOL + TP males and two of seven ATD + EB males copulated vs zero of four CHOL males), but copulation was not inhibited by combining ATD with TP (three of four ATD + TP males copulated). In Experiment 2, adult male castrated quail were injected systemically with ATD or oil for 6 days prior to and 14 days after intracranial implantation of 200-micrograms pellets containing the same amounts of TP or EB as in Experiment 1. The ATD injections completely blocked copulatory behavior in males with TP implants in the POA such that ATD/TP and Oil/TP mount frequencies differed significantly, but failed to block copulation in males with EB implants in the POA (proportions of males copulating were ATD/EB, 6/8; ATD/TP, 0/6; Oil/TP, 4/7). The cloacal foam gland, an androgen-sensitive secondary sex character, was unaffected by the dose of ATD used. We conclude that activation of copulatory behavior by TP implants in the POA is not due to nonspecific effects of high local testosterone concentrations but rather to aromatization. These results support the hypothesis that cells within the POA aromatize testosterone to estrogens, which directly stimulate the cellular processes leading to activation of male-typical copulatory behavior.

Androstatrienes↗

PubMed1993

Male rats classified as copulators and noncopulators respond differentially on the hot plate test.

Sexually naive male rats that fail to copulate with a sexually receptive female (noncopulators) have been shown to be less responsive to a variety of environmental stimuli in comparison to rats that do engage in copulation (copulators). In this experiment, it was found that noncopulators were less responsive than copulators to noxious thermal stimulation as determined by their latency to paw lick on a 50 degrees C hot plate. Pain sensitivity was not influenced in either noncopulators or copulators by exposure to a sexually receptive female. These results add to the list of differences between copulators and noncopulators.

Animals↗

PubMed1994

Effects of copulation on apomorphine-induced erection in rats.

By testing the effects of antecedent copulation on subsequent apomorphine-induced penile erection we sought to test an implicit assumption in the research on drug-induced "spontaneous" erection--namely, that this research provides information relevant to the regulation of erection in copula. In experiment 1, male rats were observed after being injected SC with 0, 15, 30, 60, or 120 micrograms/kg apomorphine (APO); 60 micrograms/kg yielded the maximum probability of erection and yawning. In experiment 2, males were injected with 60 micrograms/kg APO after no exposure to females, after three intromissions, or after copulation to sexual satiety. There was no significant effect of three intromissions, but sexually sated males displayed no erections, the first evidence that copulation affects drug-induced erections. In experiment 3, males had one ejaculation, three intromissions, or no exposure to females immediately before injection with APO (60 micrograms/kg, SC) or ascorbic acid vehicle. APO induced both erection and yawning, but neither behavior was reliably affected by copulation in APO-treated males. Among vehicle-treated males, those having three intromissions or one ejaculation before the test had shorter erection latencies and more erections than males not exposed to females. Thus, a relatively small amount of copulation resulted in a level of erectile response similar to that of APO-treated males. Optimal doses of APO may be no more effective in promoting erection in male rats than are the natural neurochemical sequelae to copulation.

Animals↗

PubMed1997

Testosterone, preoptic dopamine, and copulation in male rats.

Steroid hormones prime neural circuits for sexual behavior, in part by regulating enzymes, receptors, or other proteins affecting neurotransmitter function. Dopamine facilitates male sexual behavior in numerous species and is released before and/or during copulation in three integrative neural systems. The nigrostriatal system enhances readiness to respond; the mesolimbic system promotes many appetitive behaviors; the medial preoptic area (MPOA) contributes to sexual motivation, genital reflexes, and copulation. We have reported a consistent relationship between precopulatory dopamine release in the MPOA, when an estrous female was behind a perforated barrier, and the ability to copulate after the barrier was removed. Recent, but not concurrent, testosterone was necessary for the precopulatory dopamine response and copulation. The deficit in MPOA dopamine release in castrates was observed in basal conditions as well as the sexual context. However, dopamine in tissue punches from castrates was higher than in intact males. Because tissue levels represent primarily stored neurotransmitter, dopamine appeared to have been synthesized normally, but was not being released. Amphetamine induced greater dopamine release in castrates, again suggesting excessive dopamine storage. The decreased release may result from decreased activity of nitric oxide synthase in the MPOA of castrates. A marker for this enzyme showed lower activity in castrates than in intact males. Finally, blocking nitric oxide synthase in intact males blocked the copulation-induced release of dopamine in the MPOA. Therefore, one means by which testosterone may promote copulation is by upregulating nitric oxide synthesis in the MPOA, which in turn enhances dopamine release.

Animals↗

PubMed2003

Determinants of sperm transfer in the scorpionfly Panorpa cognate: male variation, female condition and copulation duration.

Recent studies suggest that sperm production and transfer may have significant costs to males. Male sperm investment into a current copulation may therefore influence resources available for future matings, which selects for male strategic mating investment. In addition, females may also benefit from actively or passively altering the number of sperm transferred by males. In the scorpionfly Panorpa cognata, the number of sperm transferred during copulation depended on copulation duration and males in good condition (residual weight) copulated longer and also transferred more sperm. Moreover, sperm transferred and stored per unit time was higher in copulations with females in good condition than in copulations with females in poor condition. Males varied greatly and consistently in their sperm transfer rate, indicative of costs associated with this trait. The duration of the pairing prelude also varied between males and correlated negatively with the male's sperm transfer rate, but no other male character correlated significantly with male sperm transfer rate. The results are consistent with strategic mating effort but sperm transfer could also be facilitated by the physical size of females and/or females in good condition may be more cooperative during sperm transfer.

Adaptation, Physiological↗

PubMed1993

Rhesus monkey copulation calls: honest signals for female choice?

In a wide variety of mating systems, female choice is based on the assessment of male signals, both morphological and behavioural, presumed to correlate with fitness. A crucial problem, therefore, is for females to determine whether the signal represents an 'honest' reflection of male fitness. A dominant theoretical perspective in evolutionary biology suggests that signals are honest if and only if they are costly to produce. At present, there are relatively few empirical studies of the costs and benefits of signalling in the mating context, and this is especially the case for Primates. In this paper, I examine the possibility that copulations calls--vocalizations that often elicit aggressive competition within the mating arena--are honest signals of male quality. Observations of rhesus monkey (Macaca mulatta) mating behaviour reveal that the proportion of copulating males who call decreases as competition for oestrous females increases. Males who call during copulation are more likely to be aggressively attacked than males who are silent during copulation. However, males who give copulation calls obtain more matings than males who do not, and this is true for high- and low-ranking males. Because of the cost-benefit tradeoffs, copulation calls are interpreted as honest indicators of quality that may serve an important function in female mate choice.

Animals↗

PubMed1999

Forced copulation results in few extrapair fertilizations in Ross's and lesser snow geese.

Extrapair paternity varies from 0 to over 70% of young among various populations of birds. Comparative studies have suggested that this variation is related to nesting density, breeding synchrony and the proportion of extrapair copulations. We used minisatellite DNA fingerprinting to examine levels of extrapair paternity in Ross's geese, Chen rossi, and lesser snow geese, C. caerulescens c. (hereafter snow geese) nesting in the largest known goose colony in the world. These geese have one of the highest known percentages of extrapair copulation (46-56% of all attempted copulations), and all of these appeared to be forced. Among all successful copulations, 33 and 38% were extrapair in Ross's and snow geese, respectively. Despite the high percentage of extrapair copulations, extrapair paternity was low in both Ross's and snow geese (2-5% of young). Extrapair paternity was not related to nest density in either species. However, in snow geese, extrapair paternity was more likely to occur in nests of females that nested asynchronously, either early or late in the season. This is one of a few reported examples of a negative relationship between extrapair paternity and breeding synchrony. Extrapair young also tended to come from eggs laid later in the clutch. Although forced extrapair copulations appear to be a relatively inefficient reproductive tactic for males, they may provide a reproductive advantage for some males. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed1999

Resource presence and operational sex ratio as determinants of copulation duration in the fly Rhagoletis juglandis.

The effects of the interaction between the operational sex ratio (OSR) and a resource (i.e. oviposition site) on mating dynamics have rarely been considered. We examined the effect of the resource presence and its interaction, with the effect of OSR on copulation duration in Rhagoletis juglandis, a tephritid fly species characterized by a resource-defence mating system in which males defend territories on walnut fruit. In this species, copulation duration varies from 30 s to over 1 h and was shown previously to respond strongly to changes in OSR. In the field, short copulations tended to begin and end on fruit, whereas most long copulations generally began on fruit but ended in the foliage, suggesting a possible effect of resource presence on the copulation duration. In laboratory assays of isolated pairs, copulations were significantly shorter in the presence of a surrogate fruit, confirming the effect of resource presence. In another laboratory assay, in which we manipulated OSR independently of resource presence, resource presence and OSR were additive in their effects. Results are discussed in the context of sperm competition theory. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed2000

Copulation duration and fertilization success in a damselfly: an example of cryptic female choice?

Copulation duration is highly variable (0.5-3 h) in the damselfly, Ceriagrion tenellum (Coenagrionidae). Using laboratory experiments, we tested four adaptive hypotheses to explain this variation: the effect of time constraints, in-copula mate guarding, sperm displacement and cryptic female choice. Copulation duration was negatively correlated with time of day, as predicted by the first two hypotheses, and positively correlated with male density, as predicted by the mate-guarding hypothesis. Males prolonged copulation in response to the volume of sperm stored by females, suggesting they were able to detect and quantify the amount of sperm stored. This behaviour is not explained by mate guarding or time constraint effects. Males removed all the sperm from the bursa copulatrix in just 10 min. Our results also suggest that, because the duct is too narrow to allow male genitalia to enter, males do not remove spermathecal sperm. Therefore, direct sperm removal could not explain long copulations. Prolonged copulations could also have evolved as a result of cryptic female choice if they increase male fertilization success by female-mediated processes. Our results support this idea: male fertilization success was greater after long copulations. Apparently, male copulatory behaviour elicits female responses that increase male fertilization success. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed2003

Sex differences in copulation attempts in wild bonobos at Wamba.

We examined sex differences in copulation attempts in a group of wild bonobos at Wamba, Congo, by analyzing the behavioral sequence. Most copulation attempts were initiated by approach or courtship behaviors by males. Males showed these behaviors when they were more than 5 m from females, whereas females did so only when males solicited them from within 5 m. Most copulations involved females showing perineal swelling, because males solicited those females more frequently and those females accepted copulation more frequently than did females in the non-swelling phase. Nevertheless, males solicited females in the non-swelling phase in one-third of copulation attempts, and those females accepted copulation in half of those attempts. This is markedly different from chimpanzees, in which sexual behaviors almost exclusively involve females in the swelling phase. The perineum of female bonobos during the non-swelling phase is soft and wrinkled but fairly large, which may attract males to some extent. The low, but existing, attractiveness and receptivity of female bonobos during the non-swelling phase might have evolved to control sexual competition among males and provide higher social status for females.

Animals↗

PubMed2000

Copulating with multiple mates enhances female fecundity but not egg-to-adult survival in the bruchid beetle Callosobruchus maculatus.

Postcopulatory sexual selection theory has come a long way since the evolutionary implications of sperm competition were first spelled out by Parker (1970). However, one of the most enduring questions remains: why do females copulate with multiple males? Here we show that females copulating with multiple males lay more eggs than those copulating repeatedly with the same male. We also show egg-to-adult survival to be more variable when females copulate multiply with different males and less variable when they copulate multiply with the same male. This supports the notion that egg-to-adult survival may depend on the genetic compatibility of males and females. However, pre-adult survival was highest when females copulated repeatedly with the same male rather than with different males. Thus, it would appear that polyandry in this species does not function to reduce the risk of embryo failure resulting from fertilization by genetically incompatible sperm.

Animals↗

PubMed1998

The energetic cost of copulation in a polygynandrous millipede

We determined the energetic cost of copulation in both sexes of Alloporus uncinatus, a polygynandrous millipede in which copulation can last for several hours and involves physical restraint of the female by the male. We found an elevation in the rate of oxygen consumption by males and a depression in the rate of oxygen consumption by females during copulation. The rate of oxygen consumption of females, but not of males, was elevated immediately after copulation, indicating that females had built up and were repaying an oxygen debt. On this basis, we estimated energy expenditure during copulation to be 30 % above resting levels in males and 14 % above resting levels in females. As matings are frequent in this species in the wild throughout the 4 month breeding season, we suggest that the energetic demands of copulation are a previously overlooked potentially significant cost of reproduction in this species and in other invertebrate species with similar mating patterns.

Journal Article↗

PubMed2002

Information content of female copulation calls in yellow baboons.

In a wide variety of animal species, females produce vocalizations just before, during, or immediately after copulation. Observational and experimental evidence indicates that these copulation calls are sexually selected traits, functioning to promote competition between males for access to the calling female. In this paper, we present an acoustic analysis of variation in the form of copulation calls of female yellow baboons, Papio cynocephalus cynocephalus. In particular, we examine whether information about three factors-the calling female's reproductive state, the occurrence or absence of ejaculation, and the dominance rank of the mating male-is encoded in call structure and hence is potentially available to male receivers attending to the signal. Although several features of copulation calls were correlated with each of these factors, when all three were included in multiple regressions only reproductive state and rank of the mating male had independent effects on call form. These findings indicate that female copulation calls in this species signal information about the proximity to ovulation of the calling female and also the relative competitive strength of her mating partner.

Animals↗

PubMed1977

Secretion in the rat coagulating gland (anterior prostate) after copulation.

The effect of copulation on the rat coagulating gland (anterior prostate) was studied. At 4 to 6 h after the beginning of copulation the coagulating glands of rats that had produced copulatory plugs were nearly empty of secretion. Ultrastructurally, the coagulating gland has large cisternae of rough endoplasmic reticulum (RER) and few condensing vacuoles or secretion granules. After copulation the number of secretion granules and the frequency of their expulsion into the lumen increased. Also in the lumen were "fragmentation" vesicles (50-100 nm diameter) that were bounded by a unit membrane and appeared to arise from microvilli. At 4, 6, and 7h after the beginning of copulation there was an increase in apical blebbing. Blebbing was found in both perfusion and immersion-fixed tissue. Also, after copulation there was an increase in "light cells" that were characterized by reduced RER cisternae, an electron lucent cytoplasm, and atrophic Golgi apparatus. The luminal ground substance, secretion granules, and some Golgi elements, contained polysaccharides as seen with the periodic acid-thiocarbohydrazide-silver proteinate method.

Animals↗