Home About us Contact
|
Home About us Contact | ||
|
|
||
Subordinate Males (subordinate + male)
Selected AbstractsWhy are Male Columbian Ground Squirrels Territorial?ETHOLOGY, Issue 11 2008Theodore G. Manno Male territorial defence is a component of many vertebrate mating systems and is often regarded as a tactic for acquiring mates. Traditionally considered within the context of overt site-specific defence, territoriality actually may have several components which encompass a variety of behavioural tactics (e.g. post-copulatory mate-guarding, defence of resources that females need, defence of area around females) that underlie a mating system. The purpose of our study was to evaluate such influences on the territorial behaviour of male Columbian ground squirrels in southwestern Alberta, Canada. Males were dominant and territorial if they defended a minimum convex polygon activity range by chasing other males more within the activity range than they were chased. Subordinate males had no territory and were chased throughout their ranges, but they competed for mates by increasing chases in their activity range when nearby females were oestrous. Dominant males exhibited conditional breeding tactics, tending to chase other dominant males from their territory when nearby females were oestrous, but travelling outside their activity ranges to chase subordinate males when females were not oestrous. Although females mated first with a dominant male on whose territory they resided (and in order from oldest to youngest if several territories overlapped), mating pairs were not exclusive, as females usually mated with additional males. Males also guarded females after copulation and defended females directly just before oestrus, rather than defending territory per se during those times. Thus, males possess a repertoire of behaviours that complement site-specific territoriality, and territory ownership serves to facilitate a first mating with females that live on the territory. [source] Patterns of helping effort in co-operatively breeding banded mongooses (Mungos mungo)JOURNAL OF ZOOLOGY, Issue 2 2003Michael A. Cant Abstract In most co-operative breeding species, some individuals contribute much more to helping behaviour than others. The most well-established explanation of such variation is based on kin selection and suggests that, in the absence of detectable differences in relatedness, individuals who suffer lower costs for a given level of help should contribute more. Differences in helping effort between dominance/sex categories were investigated in co-operatively breeding banded mongooses Mungos mungo in Uganda. The most conspicuous form of help in this species is provided by individuals who babysit offspring at the den while the rest of the pack goes off to forage. Across eight groups, the survival rate of pups increased with the average number of babysitters guarding them, consistent with the hypothesis that helpers benefit the brood that they guard. There was no difference between dominant males, subordinate males and breeding females in total contributions to babysitting. Subordinate males, however, contributed more to babysitting in the mornings, which were the longest and presumably the most energetically expensive sessions of the day. In six litters in one well-studied pack, dominant males and breeding females reduced their contribution to babysitting for the period that females were in oestrus. By contrast, subordinate males increased their contribution to become the main babysitters during this time. These results are consistent with the hypothesis that, where helping conflicts with breeding, individuals with little chance of direct reproduction can help at a lower fitness cost than those with a high probability of successful reproduction. [source] Sexual selection for male dominance reduces opportunities for female mate choice in the European bitterling (Rhodeus sericeus)MOLECULAR ECOLOGY, Issue 5 2005M. REICHARD Abstract Sexual selection involves two main mechanisms: intrasexual competition for mates and intersexual mate choice. We experimentally separated intrasexual (male,male interference competition) and intersexual (female choice) components of sexual selection in a freshwater fish, the European bitterling (Rhodeus sericeus). We compared the roles of multiple morphological and behavioural traits in male success in both components of sexual competition, and their relation to male reproductive success, measured as paternity of offspring. Body size was important for both female choice and male,male competition, though females also preferred males that courted more vigorously. However, dominant males often monopolized females regardless of female preference. Subordinate males were not excluded from reproduction and sired some offspring, possibly through sneaked ejaculations. Male dominance and a greater intensity of carotenoid-based red colouration in their iris were the best predictors of male reproductive success. The extent of red iris colouration and parasite load did not have significant effects on female choice, male dominance or male reproductive success. No effect of parasite load on the expression of red eye colouration was detected, though this may have been due to low parasite prevalence in males overall. In conclusion, we showed that even though larger body size was favoured in both intersexual and intrasexual selection, male,male interference competition reduced opportunities for female choice. Females, despite being choosy, had limited control over the paternity of their offspring. Our study highlights the need for reliable measures of male reproductive success in studies of sexual selection. [source] Even adult sex ratios in lemurs: Potential costs and benefits of subordinate males in Verreaux's sifaka (Propithecus verreauxi) in the Kirindy Forest CFPF, MadagascarAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2009Peter M. Kappeler Abstract Optimal group size and composition are determined by both the costs and benefits of group living for the group's members. Verreaux's sifakas (Propithecus verreauxi), a diurnal lemur, form multimale multifemale groups with the tendency toward even adult sex ratios despite a small average number of females per group. The unexpected presence of multiple adult males may be explained by tolerance of other group members if subordinate males provide benefits to the group that outweigh the costs associated with their presence. Results based on both demographic data collected over a 13-year period and behavioral observations suggest that subordinate males provide no benefits in terms of infant survival and defense against group takeover by outside males. Although groups with more males are more likely to win intergroup encounters, subordinate males do not participate in these encounters more often than expected. Subordinate males are not costly to other group members in terms of direct intragroup feeding competition, but aggression rates between dominant and immigrated subordinate males increase in the mating season. Even though subordinate males provide very few benefits to the group, they are not very costly either and thus may be tolerated by resident females and dominant males. This tolerance may help to partially explain the tendency towards their unusual adult sex ratio. Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc. [source] Perspective: Masculinized dominant females in a cooperatively breeding species, a case of cross-sexual transfer?MOLECULAR ECOLOGY, Issue 7 2007ELLEN D. KETTERSON This issue of Molecular Ecology includes an exciting article by Aubin-Horth et al. in which they examine behaviour, hormone levels, and gene expression in dominant and subordinate male and female cichlid fishes of the African species Neolamprologus pulcher. Their fascinating experiments take us one important step closer to an understanding of one of life's persistent mysteries: why males differ from females and how such differences develop and evolve. [source] Drought, Domestic Budgeting and Wealth Distribution in Sahelian HouseholdsDEVELOPMENT AND CHANGE, Issue 5 2000Matthew Turner Over the past twenty-five years, Sahelian households have experienced recurrent harvest failure and greater reliance on remittances from migratory wage labour. Household subsistence has become less dependent on household grain stores and more on the liquidation of individual wealth stores. This study investigates how these broader changes have affected struggles between household members over obligations to support the household in the Zarmaganda region of western Niger. As the land-derived leverage of male patriarchs has declined and household dependence on individual wealth stores has increased, domestic budgeting has become more contested. Household heads make case-by-case moral claims on other household members during times of grain shortage. Women and subordinate males invoke Islamic law, which accords primary provisioning responsibility to the household head, to protect their individual wealth in times of grain deficit. This article investigates the nature of these budgetary struggles, showing how individuals' decisions to contribute individual wealth to support the household are best understood as highly situated, affected not only by the specific material conditions of the household but also the interplay of the moral, structural, and individualistic imperatives that derive from one's position within the household. Using reconstructed livestock wealth histories for the members of fifty-four households in western Niger, this study investigates the material consequences of these struggles. Male heads of corporate households, the historic managers of the household's land and agricultural labour, have lost wealth relative to their wives and married male subordinates since the drought of 1984. [source] Social context affects testosterone-induced singing and the volume of song control nuclei in male canaries (Serinus canaria)DEVELOPMENTAL NEUROBIOLOGY, Issue 10 2006Géraldine Boseret Abstract The contribution of social factors to seasonal plasticity in singing behavior and forebrain nuclei controlling song, and their interplay with gonadal steroid hormones are still poorly understood. In many songbird species, testosterone (T) enhances singing behavior but elevated plasma T concentrations are not absolutely required for singing to occur. Singing is generally produced either to defend a territory or to attract a mate and it is therefore not surprising that singing rate can be influenced by the sex and behavior of the social partner. We investigated, based on two independent experiments, the effect of the presence of a male or female partner on the rate of song produced by male canaries. In the first experiment, song rate was measured in dyads composed of one male and one female (M-F) or two males (M-M). Birds were implanted with T-filled Silastic capsules or with empty capsules as control. The number of complete song bouts produced by all males was recorded during 240 min on week 1, 2, 4, and 8 after implantation. On the day following each recording session, brains from approximately one-fourth of the birds were collected and the volumes of the song control nuclei HVC and RA were measured. T increased the singing rate and volume of HVC and RA but these effects were affected by the social context. Singing rates were higher in the M-M than in the M-F dyads. Also, in the M-M dyads a dominance-subordination relationship soon became established and dominant males sang at higher rates than subordinates in T-treated but not in control pairs. The differences in song production were not reflected in the size of the song control nuclei: HVC was larger in M-F than in M-M males and within the M-M dyads, no difference in HVC or RA size could be detected between dominant and subordinate males. At the individual level, the song rate with was positively correlated with RA and to a lower degree HVC volume, but this relationship was observed only in M-M dyads, specifically in dominant males. A second experiment, carried out with castrated males that were all treated with T and exposed either to another T-treated castrate or to an estradiol-implanted female, confirmed that song rate was higher in the M-M than in the M-F condition and that HVC volume was larger in heterosexual than in same-sex dyads. The effects of T on singing rate and on the volume of the song control nuclei are thus modulated by the social environment, including the presence/absence of a potential mate and dominance status among males. 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] Why are Male Columbian Ground Squirrels Territorial?ETHOLOGY, Issue 11 2008Theodore G. Manno Male territorial defence is a component of many vertebrate mating systems and is often regarded as a tactic for acquiring mates. Traditionally considered within the context of overt site-specific defence, territoriality actually may have several components which encompass a variety of behavioural tactics (e.g. post-copulatory mate-guarding, defence of resources that females need, defence of area around females) that underlie a mating system. The purpose of our study was to evaluate such influences on the territorial behaviour of male Columbian ground squirrels in southwestern Alberta, Canada. Males were dominant and territorial if they defended a minimum convex polygon activity range by chasing other males more within the activity range than they were chased. Subordinate males had no territory and were chased throughout their ranges, but they competed for mates by increasing chases in their activity range when nearby females were oestrous. Dominant males exhibited conditional breeding tactics, tending to chase other dominant males from their territory when nearby females were oestrous, but travelling outside their activity ranges to chase subordinate males when females were not oestrous. Although females mated first with a dominant male on whose territory they resided (and in order from oldest to youngest if several territories overlapped), mating pairs were not exclusive, as females usually mated with additional males. Males also guarded females after copulation and defended females directly just before oestrus, rather than defending territory per se during those times. Thus, males possess a repertoire of behaviours that complement site-specific territoriality, and territory ownership serves to facilitate a first mating with females that live on the territory. [source] PLASTICITY IN REPRODUCTIVE PHENOTYPES REVEALS STATUS-SPECIFIC CORRELATIONS BETWEEN BEHAVIORAL, MORPHOLOGICAL, AND PHYSIOLOGICAL SEXUAL TRAITSEVOLUTION, Issue 5 2008Charlie K. Cornwallis Reproductive success is determined by a complex interplay between multiple sexual traits that promote mate acquisition and, following copulation, provide control over paternity. The intensity of sexual competition that individuals experience often fluctuates, and here we investigate how this influences the expression of reproductive traits and their relationships. We show in the fowl, Gallus gallus, that males of different social status, which experience different intensities of sexual competition, before and after copulation, have different reproductive phenotypes. Dominant males are more vigilant, feed less, and have larger sexual ornaments than subordinate males. Experimentally manipulating social status revealed that these differences were phenotypically plastic, indicating multiple sexual traits were dependent on the social environment. We integrated these data with previous published findings on changes in sperm numbers and velocity to show that relationships between traits were different for males when they were dominant and when they were subordinate. Furthermore, when males switched status a complex array of negative and positive correlations between the degree traits changed was observed. Our results suggest that variation in the intensity of sexual competition generates reversible plasticity in reproductive phenotypes and that relationships between sexual traits may be variable and influence the evolution of reproductive strategies. [source] Long-range call use in dominance-structured Crested Tit Parus cristatus winter groupsJOURNAL OF AVIAN BIOLOGY, Issue 1 2000Indri?is Krams In this study on free-ranging Crested Tits Parus cristatus, I examine the relationship between social dominance and the frequency of use of long-range communication calls. Calling rates of trills were highest among socially dominant individuals and they gave more calls when close to the boundary of their territories. Dominant females uttered fewer calls than their mates. However, they gave significantly more calls than subordinate males and subordinate females, the latter calling least. A removal and playback experiment revealed a relationship between the utterance of trilled calls and the defence of the winter territory in the Crested Tit. Although territorial vocalizations could incur costs, territorial individuals may gain from improved winter survival by decreasing the risk of food stealing by Crested Tits from adjacent territories. [source] Patterns of helping effort in co-operatively breeding banded mongooses (Mungos mungo)JOURNAL OF ZOOLOGY, Issue 2 2003Michael A. Cant Abstract In most co-operative breeding species, some individuals contribute much more to helping behaviour than others. The most well-established explanation of such variation is based on kin selection and suggests that, in the absence of detectable differences in relatedness, individuals who suffer lower costs for a given level of help should contribute more. Differences in helping effort between dominance/sex categories were investigated in co-operatively breeding banded mongooses Mungos mungo in Uganda. The most conspicuous form of help in this species is provided by individuals who babysit offspring at the den while the rest of the pack goes off to forage. Across eight groups, the survival rate of pups increased with the average number of babysitters guarding them, consistent with the hypothesis that helpers benefit the brood that they guard. There was no difference between dominant males, subordinate males and breeding females in total contributions to babysitting. Subordinate males, however, contributed more to babysitting in the mornings, which were the longest and presumably the most energetically expensive sessions of the day. In six litters in one well-studied pack, dominant males and breeding females reduced their contribution to babysitting for the period that females were in oestrus. By contrast, subordinate males increased their contribution to become the main babysitters during this time. These results are consistent with the hypothesis that, where helping conflicts with breeding, individuals with little chance of direct reproduction can help at a lower fitness cost than those with a high probability of successful reproduction. [source] Male dominance, paternity, and relatedness in the Jamaican fruit-eating bat (Artibeus jamaicensis)MOLECULAR ECOLOGY, Issue 9 2003Jorge Ortega Abstract We analysed variation at 14 nuclear microsatellite loci to assess the genetic structure, relatedness, and paternity of polygynous Jamaican fruit-eating bats. A total of 84 adults captured in two caves exhibited little genetic differentiation between caves (FST = 0.008). Average relatedness among adult females in 10 harem groups was very low (R = 0.014 ± 0.011), providing no evidence of harem structure. Dominant and subordinate males shared paternity in large groups, while dominant and satellite males shared paternity in smaller groups. However, our results suggest that male rank influences paternity. Dominant males fathered 69% of 40 offspring, followed by satellite (22%) and subordinate males (9%). Overall adult male bats are not closely related, however, in large harem groups we found that subordinate and dominant males exhibited relatedness values consistent with a father-offspring relationship. Because dominant and subordinate males also sired all the pups in large groups, we propose that their association provides inclusive fitness to them. [source] Even adult sex ratios in lemurs: Potential costs and benefits of subordinate males in Verreaux's sifaka (Propithecus verreauxi) in the Kirindy Forest CFPF, MadagascarAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2009Peter M. Kappeler Abstract Optimal group size and composition are determined by both the costs and benefits of group living for the group's members. Verreaux's sifakas (Propithecus verreauxi), a diurnal lemur, form multimale multifemale groups with the tendency toward even adult sex ratios despite a small average number of females per group. The unexpected presence of multiple adult males may be explained by tolerance of other group members if subordinate males provide benefits to the group that outweigh the costs associated with their presence. Results based on both demographic data collected over a 13-year period and behavioral observations suggest that subordinate males provide no benefits in terms of infant survival and defense against group takeover by outside males. Although groups with more males are more likely to win intergroup encounters, subordinate males do not participate in these encounters more often than expected. Subordinate males are not costly to other group members in terms of direct intragroup feeding competition, but aggression rates between dominant and immigrated subordinate males increase in the mating season. Even though subordinate males provide very few benefits to the group, they are not very costly either and thus may be tolerated by resident females and dominant males. This tolerance may help to partially explain the tendency towards their unusual adult sex ratio. Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc. [source] Agonistic behavior and electrical stimulation of the antennae induces Fos-like protein expression in the male cricket brainARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 1 2010Kaushik Ghosal Abstract Immediate early genes (IEG) such as c-Fos and Fos-related antigens (FRA) have been used as markers of neuronal activation. In this study, we determined whether the expression of c-Fos/FRAs is increased in the brains of adult male Acheta domesticus crickets following agonistic interactions. We looked for c-Fos/FRA proteins in the brain of un-fought, control male crickets and of dominant and subordinate male crickets sacrificed at different time periods following an agonistic interaction. Using immunoblot analysis, we found four different c-Fos/FRA-like proteins in the adult cricket brain. Continuous agonistic interaction increased c-Fos/FRA protein expression in the brains of subordinate males compared to control and dominant males. In addition, direct electrical stimulation of the male cricket antennae increased c-Fos/FRA-like protein in the brain. We identified the specific brain regions that exhibit c-Fos/FRA-like immunoreactivity in crickets. We detected c-Fos/FRA-like cellular immunoreactivity in different functional regions of the adult brain including the pars intercerebralis, protocerebrum, deutocerebrum, and the cortex of the mushroom bodies. © 2010 Wiley Periodicals, Inc. [source] | ||||||||||