Presence Of Other Males Research Articles

EFFECTS OF MATE ATTRACTION AND MALE-MALE COMPETITION ON PATERNAL CARE IN A GOBY

Individuals should invest energy into current reproduction in relation to the possibility of gaining additional reproduction in the future. This study investigated reproductive trade-offs and paternal care in the two-spotted goby, Gobiusculus flavescens. Specifically, it provides the first experimental test of the hypothesis that increased mate availability leads to an increase in filial cannibalism. We also tested whether filial cannibalism increased with increased cost of care (presence of other males), as might be expected. In addition, we investigated whether conflicting demands (i.e. presence of potential mates and male competitors) results in lower parental expenditure. We found no evidence that male two-spotted gobies caring for eggs adjust their degree of filial cannibalism in relation to mate availability or the cost of care. However, caring males reduced the level of parental care with an increased mating effort, suggesting that they trade care of eggs against the chance of future reproduction. This effect was also apparent when other males were present, suggesting a conflict between direct egg care and defence of the nest.

Comportamiento social y reproductivo del roedor subterráneo solitario Ctenomys talarum (Rodentia: Ctenomyidae) en condiciones de semicautiverio

The social and reproductive behavior of the subterranean rodent Ctenomys talarum (Thomas, 1898) was studied in a seminatural enclosure resembling both the complexity of the natural burrow system and the sex ratio observed in wild populations. Contrary to expectations based on their solitariness and their rather simple social system, the interactions among individuals of this species were diverse and complex. Auditory, tactile and chemical communication were of importance during territory guarding, courtship and copulatory behavior. Individuals from different populations differing in ecological attributes behaved in substantially different ways. Males from Mar de Cobo, a population characterized by a high density and a skewed sex ratio favouring females, behaved aggressively, which resulted in frequent wounding. Males from Mar de Cobo established a dominance hierarchy among them, which preceded courtship and, eventually, resulted in the dominant male monopolizing mating activity. On the contrary, males from Necochea, a population showing low density and an even sex ratio, behaved less aggressively; dominance relationships were absent, and males performed courtship behaviors in the presence of other males.

Body size and paternal investment in the genus Onthophagus (Coleoptera, Scarabaeoidea)

AbstractDuring reproduction, dung beetles of the genus Onthophagus typically bury portions of dung removed from the dung pad. Even though females are capable of successfully constructing and provisioning nests when unaccompanied by males, extensive levels of co‐operation between sexes have been reported. In some species, males show a clear dimorphism in body plan and only large horned males are known to assist females. In O. taurus this form of paternal investment is facultative and depends on social context (namely the presence of other males). We studied relationships between body size and paternal investment in five Onthophagus species (i.e. O. coenobita, O. fracticornis, O. illyricus, O. taurus and O. vacca). Two types of tests were established. In test A, a large and a small male were placed with a single, medium‐size female; in test B, a large and a small female were placed with a single large male. In controls one male was placed with one female. Individuals were maintained for 10 days. Then the enclosures were opened to assess the position of each beetle. When two mates were found in close vicinity or in the same tunnel provisioning dung, a co‐operative behaviour was assumed. In competitive tests, small males and small females never co‐operated with their potential mates whilst large and medium‐size individuals often co‐operated with mates inside the same tunnels. No differences in frequencies of co‐operation were found between large and medium‐size females. Small females and small males scarcely co‐operated with large or medium‐size mates in controls. These results suggest that large individuals outcompete the small ones. They also suggest that paternal investment depends on body size of both mates. Large males of all species assist medium‐size and large females, whereas small males do not. However, large males do not invest much parental effort on small females that, in fact, are poorly assisted. We assume that large individuals of both sexes are reproductively superior to small ones. The propensity of both small females and small males to excavate was lower than that of larger individuals; accordingly, digging capacity could be a proximate factor explaining facultative paternal investment in these species.

The effects of prenatal stress, and of prenatal alcohol and nicotine exposure, on human sexual orientation

Background: Studies of rats have shown that mothers who are subjected to stress during pregnancy are more likely than mothers who are not stressed during pregnancy to have male offspring who exhibit female-typical sexual receptivity postures (lordosis) in the presence of other males following the onset of puberty. More recent animal experiments have indicated that prenatal exposure to alcohol affects the sexual preferences of male offspring in ways that are similar to the effects of prenatal stress. Research with human subjects have thus far yielded inconsistent findings regarding the effects of prenatal stress on male sexual orientation, and no research has yet addressed the possible involvement of prenatal exposure to alcohol or other widely used recreational drugs, such as nicotine. Purpose: The present study was undertaken to determine if prenatal stress could be one of the causes of variations in sexual orientation in humans, both singularly and in conjunction with prenatal exposure to alcohol and nicotine. Methods: Over 7500 offspring and their mothers provided information regarding the offspring's sexual orientation and the mother's stressful experiences and use of alcohol and nicotine during pregnancy. Results: Findings indicate that prenatal stress has a modest but significant effect on the sexual orientation of male offspring, particularly when the stress occurred during the first trimester of pregnancy. Regarding prenatal exposure to alcohol, no evidence was found to suggest that it impacted offspring sexual orientation of either males or females. Prenatal nicotine exposure, however, appears to significantly increase the probability of lesbianism among female offspring, especially if the exposure occurred in the first trimester along with prenatal stress in the second trimester. Conclusion: The present study is consistent with animal models suggesting that prenatal stress disrupts the typical sex hormonal milieu within which male fetal brains are sexed, thereby feminizing/demasculinizing the male's sexual orientation. However, little support was found for similar effects of prenatal alcohol exposure. In the case of prenatal nicotine, this study is the first to suggest that this drug has masculinizing/defeminizing effects on the sexual orientation of female offspring.

The interaction of male and female reproductive strategies and paternity in wild Japanese macaques, Macaca fuscata

Japanese macaques reside in large, mixed-sex social groups in which various reproductive strategies of both sexes operate simultaneously. This report represents the first study combining behavioural and genetic data to examine the interaction of male and female reproductive strategies in primates (N=15 adult males, N=15 adult females, Yakushima Island, Japan). During one mating season, socially dominant males monopolized most female matings. Furthermore, the six offspring sired by troop males were more likely sired by higher-ranking males than lower-ranking males. Nontroop males sired three additional offspring in the troop. Lower-ranking troop males avoided direct competition with higher-ranking males by engaging in sneak copulations with females outside of the presence of other males. Also, females expressed mate choice behaviour towards multiple males of various dominance ranks. Thus, the female strategy of attempting to mate with multiple males conflicted with the mate-guarding strategy of high-ranking males. Despite some female mate choice for mid- and low-ranking males and alternative male mating tactics by subordinate males, high-ranking males were able to monopolize most, but not all, within-troop mating and paternity. This result was due in part to the low number of females mating at the same time. The mean number of females displaying mating behaviour per day was 2.42 (range 1–5), and higher-ranking males more successfully monopolized females on days when fewer females were mating. The number of females mating simultaneously influences the outcome of reproductive conflicts between the sexes.

The presence of neighbors affects waving display frequency by Scopimera globosa (Decapoda, Ocypodidae)

Scopimera globosa, a small ocypodid crab, rhythmically raises and lowers its body and both chelae in a waving display when it is not interacting directly with another individual. To determine whether waving is a social signal and to deduce its possible function, we manipulated the sex and density of crabs in a field enclosure and recorded the waving frequency of males. Males with abundant female neighbors waved significantly more often than when the same males were caged with abundant male neighbors. Males caged with fewer neighbors of either sex seldom waved. Thus, males waved most in the presence of females, especially at high density, and least in the presence of other males, suggesting that waving may function in female acquisition.

For Whom The Bird Sings: Context-Dependent Gene Expression

Male zebra finches display two song behaviors: directed and undirected singing. The two differ little in the vocalizations produced but greatly in how song is delivered. “Directed” song is usually accompanied by a courtship dance and is addressed almost exclusively to females. “Undirected” song is not accompanied by the dance and is produced when the male is in the presence of other males, alone, or outside a nest occupied by its mate. Here, we show that the anterior forebrain vocal pathway contains medial and lateral “cortical–basal ganglia” subdivisions that have differential ZENK gene activation depending on whether the bird sings female-directed or undirected song. Differences also occur in the vocal output nucleus, RA. Thus, although these two vocal behaviors are very similar, their brain activation patterns are dramatically different.

Transfer, Perception, and Activity of Male Pheromone of Acrolepiopsis assectella with Special Reference to Conspecific Male Sexual Inhibition

In the leek moth, Acrolepiopsis assectella, the male, stimulated by a calling female, produces a sexual pheromone that is active on the female. The male-produced pheromone blend contains eight alkanes previously isolated from the male hair-pencils. We used EAG techniques to study the effect of the pheromone on females reared on leek or on artificial diet and on males reared on leek. The optimal stimulation duration appeared to be 1.6 sec exposure to the pheromone or components. The concentrations tested on the antenna were of the order of 1012 molecules/cm3. The hair-pencil extract tested was of an estimated concentration of around 109 molecules/cm3. The antennal responses are expressed relative to responses to a standard, amyl acetate, but also as an absolute value. Generally, females reared on artificial diet and males reared on leek responded better than females reared on leek. Of the alkanes tested, those present in hair-pencils gave higher responses, with hexadecane always giving the strongest response. A possible inhibiting activity of male leek moth pheromone on the sexual behavior of conspecific males was investigated. The behavior of sexually stimulated males was observed in the presence of other males, hair-pencil extracts, and different compounds either pure or in a mixture. The experiments established that in this species, male pheromone inhibits wing fluttering duration of conspecific males. This inhibition was obtained not only with fluttering males as a source of pheromone but also with all the alkanes tested. The inhibition was due to hair-pencil chemicals, particularly if these were perceived by olfaction plus contact. Wing fluttering increased the inhibitory activity of male-derived alkanes.

Post-copulative guarding: mating behavior of non-territorial male sika deer ( Cervus nippon) in an enclosure

The mating behavior of captive male sika deer ( Cervus nippon), which hold no territory or no harem, was studied on Nozaki Island, in October 1990. During the study period two females came into estrus and a dominant male monopolized the copulation with these females. We observed two characteristic behaviors, which had never been observed in harem-making or territorial males. First, the dominant male usually tolerated the presence of other males. However, he was seen to drive away other males, defending the one receptive female on her day of estrus. The frequency of aggressive interactions, e.g., aggressive approach and chasing, increased on the day of estrus (aggressive approach: U = 2, z = − 1.835, p = 0.06; chasing: U = 0, z = − 2.820, p < 0.01). Second, the dominant male remained within a radius of 5 m of the served female following copulation for more than 10 h, and chased away any males approaching the female. This behavior, therefore, was considered post-copulative guarding. Multiple copulation by females was observed in the wild population on Nozaki Island. High tolerance to subordinate males and post-copulative guarding of females are mating tactics of the dominant male associated with captivity.

Female egg dumping and the effect of sex ratio on male egg carrying in a coreid bug

PhyUomorpha lacmiata Vill (Heteroptera, Coreidae) is unique among teiieauial infects in that females ghie eggi on the back* of other conspecifics. Egg carrying by P. lacmiata males has previously been considered as paternal care. We explored female oviposidon with respect to previous mating experience of females and tested whether sex ratio affects male egg-carrying. The hypothesis that male egg-carrying is a form of paternal care predicts that a male should always accept eggs after mating with a female. However, if male egg-carrying is a form of postcopulatory mate guarding rather than paternal care, egg carrying should increase in die presence of other males. When two couples were placed together, females laid eggs on the backs of all individuals enclosed, including the backs of other females. However, when a female was accompanied by 2 males, 22 out of 26 females oviposited on their mating partner. Thus, sexual compeddon rather than paternity alone, affects a male's eagerness to carry eggs. However, even if males sometimes carry their own eggs, females lay eggs on the backs of all conspecifics they can easily acquire. Thus, egg carrying in P. lacmiata is partially voluntary and partially die result of female egg dumping. Ktj words: Coreidae, egg carrying, Heteroptera mate guarding, paternal care, PhyUomorpha lacmiata, sex ratio. [Bthav Ecol 8:429-432 (1997)1

Aggression and preputial gland of male mice affected by the presence of other males

The level of aggressiveness and the weight of preputial gland and testis in male mice (Mus musculus) were influenced by housing condition, especially by the presence of cohabitant males. In this study, the relation between aggressiveness and the preputial gland and testis weight was studied for various housing conditions. The mouse individually housed in a cage that was linked to another cage containing another male separated by wire net was more aggressive than isolated or paired mice. The preputial gland weight also showed the same tendency, suggesting that the odor from other males promotes pituitary-gonadal activity in males, and that long-term cohabitance inhibits it.

Male Reproductive Success in Sessile Invertebrates: Competition for Fertilizations

Recent in situ fertilization studies of free spawning and brooding marine organisms have focused almost exclusively on the yield of fertilized ova (female reproductive success). As a consequence, we known little about the factors that determine male reproductive success. If marine organisms compete for fertilizations (as do many terrestrial organisms), then a male's reproductive success should be reduced by the presence of other males. We tested this hypothesis via in situ experiments employing allozyme markers for both a colonial ascidian (Botryllus schlosseri) and a bryozoan (Celleporella hyalina). Under moderate density conditions, the presence of closer male—functioning colonies reduced the fertilization success of more distant males in both species. In C. hyalina, male fertilization success also increased with allocation to sperm production. In addition, selfing rates in this species were negatively correlated with the abundance of outcross sperm. These results suggest that male reproductive success in sessile marine invertebrates must be assessed as a function of the gamete output and spatial distribution of other males in a population, and that the performance of isolated males may yield overestimates of male fertilization success in natural populations.

Aspects of mating behaviour in two harpacticoid copepods: tigriopus fulvus and tisbe holothuriae

The results reported here demonstrate that, inTigriopus fulvus: 1) males discriminate among females belonging to different developmental stages; 2) males paired with copepodid females react to the presence of other males, making pairing more stable. It also appears that, inTisbe holothuriae, both males and females release a compound which promotes the attraction of specimens belonging to the opposite sex. The significance of the differences in mating behaviour betweenTigriopus andTisbe are discussed.

Dominance among male chimpanzees in the Mahale Mountains National Park, Tanzania: A preliminary study

Dominance relationships among male chimpanzees in the Mahale Mountains National Park, Tanzania, were analyzed. Although all adolescent males were unequivocally subordinate to all adult males, dominance relationships within the age classes were much less clear. Especially among adolescent males, few pant-grunts or agonistic interactions occurred. While adolescent males frequently pant-grunted at adult males, these latter males, except the alpha and the youngest, rarely pant-grunted to one another. This suggests that a difference of social status exists between adolescent and adult males. Adult males rarely display overt dominance to one another probably because the presence of other males affects their interactions. Moreover, they seem to try to keep their dominance relationship ambiguous when making it overt is not advantageous to them. This may be a political way for males to coexist with one another in a unit-group.

The influence of the ambient sex ratio and intermale competition on the sexual behavior of the red-spotted newt, Notophthalmus viridescens (Amphibia: Urodela: Salamandridae)

This paper extends previously published observations of the sexual behavior of the redspotted newt. In encounters between single males and females, the male either performs a brief lateral, or ‘hula’, display or clasps the female and holds her in amplexus for as long as 3 h. Experimental manipulation of the ambient sex ratio in an observation aquarium showed that the number of females available to a male did not influence his ‘decision’ whether to perform hula display or-attempt amplexus. In the presence of other males, a courting male showed a greater tendency to adopt the amplexus mode of courtship. Males interfered with one another's attempts to court and inseminate females. Unpaired males tried to displace those engaged in amplexus, but were seldom successful. During the spermatophore deposition and transfer stage of both courtship modes, unpaired males mimicked female behavior, apparently in order to obtain inseminations. Hula courtships were the most vulnerable to this type of competition; multiple insemination of the female was occasionally observed. The various costs and benefits associated with the various sexual strategies of male newts are discussed, together with some relevant ecological data. Similarly complex behavior in some other animals is also considered.

Female Promiscuity and Male Reproductive Success in Social Birds and Mammals

The selective pressures that influence the evolution of mating systems in multimale social groups that persist throughout the breeding season may differ significantly from those that operate in one-male systems. Within this type of group, females may increase their reproductive success by mating with several males, if they can thereby induce those males to provide care for their young. Males may benefit from the presence of other males during reproduction, either through joint feeding of the young or through other cooperative activities. When males are related to each other, inclusive fitness benefits arising from the reproductive success of other males also will be important. Extending the approach of Maynard Smith (1977, 1978), I develop a model for the evolution of different mating systems within multimale groups. The analysis considers the effects on reproductive success and inclusive fitness when a male either shares mates with other males, or leaves the group and attempts to breed elsewhere. The model suggests that when promiscuity is advantageous to the female, a male should not interfere with copulations by other males when male-male cooperation is important to the survival of the young, and when subordinate males are likely to leave the group if prevented from breeding. Males should attempt to monopolize matings with a female when subordinate males are closely related to the breeders, and when they have a low probability of finding new mates if they leave the group.

Silk Production in Adult Males of the Wolf Spider Pardosa Amentata (Cl.) (Araneae, Lycosidae)

A method is described for selectively sealing the spinnerets of adult males of Pardosa amentata. The silk produced by males with various spinnerets sealed was investigated. Males, by themselves, in the presence of adult males and in the presence of adult females were tested. It was found that all the silk produced came from the anterior spinnerets. This indicates that no silk is produced from the glandulae aciniformes under these circumstances. The glandulae ampullaceae produce the drag-lines and the glandulae piriformes the attachment discs. Silk from the glandulae piriformes is used to produce two further silk patterns when the male is in the presence of other males or females. The nature of these silk patterns is dependent on the manner in which the male walks in the two situations and the striking feature about this silk production by the glandulae piriformes is that during courtship large quantities of piriform silk are produced compared with the quantities produced in other situations. The meaning of the term drag-line is discussed.