When to feed: decision making in sticklebacks,Gasterosteus aculeatus

Synopsis The functional analysis of feeding, territory defense and nest-directed activities by reproductively mature male three-spined sticklebacks, Gasterosteus aculeatus, was carried out under controlled laboratory conditions. Territorial males were placed in motivational conflict between feeding and nest-directed activities by making performance of the two necessary activities spatially incompatible. During a limited time each day they had to choose between staying close to their nests to carry out nest-directed activities, and moving into a separate compartment of the observation tank to feed. Males were trapped for varying lengths of time within a central, neutral compartment as they moved between the nest compartment at one end of the tank and the feeding compartment at the other. Their choice of either compartment following such trapping was recorded as indicative of their dominant motivation state. Males tended to be nest dominant in these observations, but motivational dominance could be altered. Males deprived of food for longer periods of time, or presented with an empty food cup during the observation were more likely to be food dominant. If they had not been previously deprived of food, or if a sexually mature conspecific had just been presented in the territory, males were more likely to be nest dominant. The length of time males were trapped in a neutral compartment while in transit between the nest and food also significantly influenced their subsequent behavior. Longer interruptions were more likely to result in a change in the direction in which the male was moving, but only when he was moving towards the subdominant activity. This effect supports the hypothesis of time sharing as the mechanism regulating motivation in these fish.     

A colour and size dimorphism in the green swordtail (population Jalapa): female mate choice,male–male competition,and male mating strategies

Two types of males are present in the Jalapa population of Xiphophorus helleri: Males with a black or dark brownish mid-lateral stripe ("black males") mature earlier and are smaller than males with a red or brownish mid-lateral stripe ("red males"). We tested the hypothesis that the colour patterns of red males may be regarded as ornaments, which evolved as the result of inter- and/or intrasexual selection. As predicted, in choice tests females exhibited a strong preference for red versus black males. Furthermore, in competition experiments red males became dominant over black males with no exception, both when body size was equal and even when red males were 3–5 mm smaller than black males. However, contrary to our prediction, sneak–chase behaviour in black males was not detected, and courtship displays occurred at similar rates in both morphs. Red males are always heterozygous, with one allele for red and another for black colouration. This genetic constraint potentially prevents the extinction of the black morph. Possibly, the colour patterns of red males are functioning as indicators of heterozygosity. According to the "heterozygosity theory of mate choice", the female's preference for red males may be adaptive.     

食物因素对笼养褐马鸡冬季打斗行为的影响

绝大多数动物社群中都存在着等级行为[2 ,10 ] ,高等级个体在取食、交配等方面都拥有优先权 ,最终导致高等级个体具有更高的存活率和繁殖率[1,3 ,4 ,7～ 9] 。这种等级行为可以避免频繁的打斗所带来的伤害和能量消耗。但是当争夺的资源很重要时 ,低等级个体将会忍受一定程度的代价以打斗的方式去争夺资源[6] 。有关食物分布格局和饥饿状况对鸟类取食打斗行为的影响几乎还为未见报道 ,本文利用冬季集群期内的一个笼养褐马鸡(Ｃｒｏｓｓｏｐｔｉｌｏｎｍａｎｔｃｈｕｒｉｃｕｍ )人工种群 ,研究了不同食物分布格局和饥饿状况下取食和打斗行为…     

Great expectations: dominance,breeding success and offspring sex ratios in red deer

Differences in dominance rank among red deer (Cervus elaphus) females (hinds) on Rhum were related to their breeding success as well as to the comparative success of male and female offspring. Males (stags) born to mothers above median rank were more successful than hinds, while hinds born to subordinate mothers were more successful than stags. The ratio of male to female calves produced by dominant mothers was significantly higher than that produced by subordinates. Since dominance rank among hinds is related to their body weight as adults and to their birth weight, these results suggest that the birth sex ratio may be affected by environmental factors operating during a female's early development.     

Transmission of stridulatory signals of the burrower bugs, Scaptocoris castanea and Scaptocoris carvalhoi (Heteroptera: Cydnidae) through the soil and soybean

Abstract.  Males and females of the burrower bug species Scaptocoris castanea Perty and Scaptocoris carvalhoi Becker emit stridulatory signals when on the roots of soybean. The substrate-borne components of the signal can be recorded on the plant but not on the surrounding soil surface. The stridulatory apparatus is composed of the tergal plectrum (lima) and the stridulitrum (stridulatory vein) on the underside of the hind wings. The male plectrum has one ridge and the female lima has 13 ridges. Stridulitra of different species differ in the length and in the number of teeth. Rubbing of plectrum (lima) ridges over the stridulitrum in one or both directions produces pulse trains. The velocity of signals that are recorded less than 0.5 cm from the bug is below 0.013 mm s⁻¹ on the soil and below 0.066 mm s⁻¹ on the leaf surface. Broadband spectra have a dominant frequency of less than 1 kHz and subdominant peaks extending up to 7 kHz. The dominant frequency of the stridulatory signal transmitted through a plant decreases together with the proportion of its higher frequency spectral components. Signals are attenuated for 3–9 dB cm⁻¹ when transmitted through the soil or soybean leaf and for approximately 1 dB cm⁻¹ when transmitted through soybean stem.     

Sexual Differences in Offspring Defense in a Monogamous Cichlid Fish

Solitary male and female Texas cichlids, Cichlasoma cyanoguttatum employ different tactics when defending their offspring. Males emphasize the lateral display against an intruder and make infrequent return visits to the young while the intruder is present. The female is more likely to attack, attempting to bite the intruder and also making frequent return visits to the offspring. These differences disappear with increasing age of the offspring as the male becomes more like the female with more violent attacks. Both defense systems appear effective, in the short term, against intruders.     

Hormonal and social factors affecting evoked sexual behavior in Rhesus monkeys

Male rhesus monkey sexual behavior occurring spontaneously or evoked by remotely-controlled hypothalamic stimulation was studied in dominant and subdominant males with both dominant and subdominant, estrogen-treated or untreated, ovariectomized females. The behavior was quantified in terms of number and duration of ejaculatory sequences, number of thrusts, and number of mounts per sequence. Little or no spontaneous sexual behavior was observed with an untreated ovariectomized female. However, evoked sexual behavior with the exception of evoked ejaculation could be obtained whether the females were treated or untreated. Spontaneous and evoked sexual behavior was directed towards both dominant and subdominant females. The female chosen by the male was in part determined by the dominance status of the female. Evoked sexual behavior differed from spontaneous behavior in terms of an increased number of thrusts per mount, an increased number of ejaculations per session, and a decrease in latency between ejaculatory sequences.     

Vibratory signals of the harlequin bug and their transmission through plants

Abstract. Males of the harlequin bug, Murgantia histrionica (Hahn), produce five different vibrational songs, whereas females produce one song. Songs differ from those of other stink bugs primarily in their species‐specific temporal characteristics. The broad band male courtship songs of M. histrionica are achieved by a combination of different frequency modulated and/or narrow band subunits, with several higher harmonic frequencies. Males rather than females initiate substrate‐borne vibrational communication, and the longer‐range calling songs found typically in other pentatomid species are lacking. Interindividual differences in song temporal and spectral characteristics are discussed. Transmission of vibrational songs through a cabbage head is more efficient along veins than along lamina. Attenuation of signals transmitted through veins is low and similar to that reported previously for plant stalks. On the leaf vein, distances between peak amplitude minima and maxima are different for the dominant and subdominant frequencies. At any distance from the vibration source, a different relationship between spectral peak amplitudes can be recorded. Resolution of these differences, together with velocity differences between signals recorded on the vein and lamina, may help small stink bugs to estimate distance and to locate each other on a plant.     

Two Overlapping Subdominant Epitopes Identified by DNA Immunization Induce Protective CD8+ T-Cell Populations with Differing Cytolytic Activities

Subdominant CD8(+) T-cell responses contribute to control of several viral infections and to vaccine-induced immunity. Here, using the lymphocytic choriomeningitis virus model, we demonstrate that subdominant epitopes can be more reliably identified by DNA immunization than by other methods, permitting the identification, in the virus nucleoprotein, of two overlapping subdominant epitopes: one presented by L(d) and the other presented by K(d). This subdominant sequence confers immunity as effective as that induced by the dominant epitope, against which >90% of the antiviral CD8(+) T cells are normally directed. We compare the kinetics of the dominant and subdominant responses after vaccination with those following subsequent viral infection. The dominant CD8(+) response expands more rapidly than the subdominant responses, but after virus infection is cleared, mice which had been immunized with the "dominant" vaccine have a pool of memory T cells focused almost entirely upon the dominant epitope. In contrast, after virus infection, mice which had been immunized with the "subdominant" vaccine retain both dominant and subdominant memory cells. During the acute phase of the immune response, the acquisition of cytokine responsiveness by subdominant CD8(+) T cells precedes their development of lytic activity. Furthermore, in both dominant and subdominant populations, lytic activity declines more rapidly than cytokine responsiveness. Thus, the lysis(low)-cytokine(competent) phenotype associated with most memory CD8(+) T cells appears to develop soon after antigen clearance. Finally, lytic activity differs among CD8(+) T-cell populations with different epitope specificities, suggesting that vaccines can be designed to selectively induce CD8(+) T cells with distinct functional attributes.     

Agonistic Encounters Among Male Elephant Seals: Frequency, Context, and the Role of Female Preference

SYNOPSIS. Aggressive interactions between male northern elephantseals, Mirounga angustirostris, observed during the course ofthree breeding seasons are analyzed from the perspective ofcosts and benefits to individuals. Males spend less than onepercent of their time in aggressive activities and the overwhelmingmajority of agonistic interactions consist only of visual andvocal threats rather than physical combat. Males are most likelyto threaten other males when the likelihood that they will besuccessful in displacing the opponent is high. Males who aremounting females, or who are in close proximity to females,are threatened more frequently than males who are otherwiseoccupied. However, high ranking bulls do regularly issue threatswhich are not provoked by the location or behavior of the recipient.Despite the obvious costs of such threats, this behavior maybe favored as a result of female choice. Estrous females aremore receptive when mounted by a male who has just dominatedanother than when mounted by a male of similar rank who hasbeen resting or recently displaced by a stillmore dominant male. A general argument is made that in species where social statusof males is correlated with their genetic fitness, female choiceis likely to be based on social signals which are used incompetitionbetween males.     

False Alarm Calls as a Means of Resource Usurpation in the Great Tit Parus major

Great tits Parus major regularly gave alarm calls in winter without the presence of actual or potential predators. Such false alarm calls were given to deceive both conspecifics and heterospecifics. False calls were given when flock-feeding sparrows Passer spp. monopolized a concentrated food source; if the food resource was dispersed false alarm calls were not used, independently of the presence of sparrows. Dominant great tits used alarm calls deceptively if a dominant conspecific was present on a concentrated food source but not if a subdominant individual was present; subdominant great tits were displaced by means of threat displays. Subdominant individuals gave false alarm calls both if dominant or subdominant conspecifics were present. False alarm calls were especially used when food was scarce or when great tits were feeding at a high rate, i.e. during snow storms and in the morning and the afternoon.     

Social housing influences the composition of volatile compounds in the preputial glands of male rats

In rodents the preputial glands are one of the major sources of pheromones. These volatile chemosignaling compounds are known to elicit specific behavioral and physiological effects in their conspecifics. While social stress can alter both the behavior and hormonal status of rodents, little is known about its influence on the volatile constituents of the preputial glands. We have examined the composition of volatile compounds in the preputial glands of gonadally intact male rats housed for 70 days in either unisex triads (three/cage) or singly. The rank status of triad-housed rats was based on quantitative behavioral assessments taken during the initial 30 min of triad housing. Dominant rats had heavier preputial glands compared to subdominant and subordinate rats. Capillary gas chromatography-mass spectrometry identified 56 volatile preputial compounds, of these 17 did not differ between groups while 26 compounds were significantly higher in the single-housed compared to the triad-housed rats. Six additional volatile compounds were higher in the dominant compared to the other 3 groups, while another six compounds were higher in both the dominant and single-housed rats compared to the subdominant and subordinate rats. It can be concluded that both housing condition and social rank status have significant but different effects on the composition of volatile compounds found in preputial glands of male rats. The physiological and behavioral significance of these changes in preputial gland volatile compound composition in rats remain to be investigated.     

Personality and fitness consequences of flight initiation distance and mating behavior in subdominant male reindeer (Rangifer tarandus)

Animal personality has been studied extensively in recent years, yet multidimensionality in tendencies of risk‐related behavior, and the role of such consistency from a mating tactics perspective, is yet to be investigated. We used a semi‐domesticated herd of reindeer (Rangifer tarandus) to examine individual subdominant male propensity to risk mating attempts on guarded females, as well as flight initiation distance (FID), within the personality paradigm to elucidate potential fitness consequences of consistency from an adaptive perspective. Data were collected at the Kutuharju Reindeer Research Station in Kaamanen, Finland, where measures of personality were generated using field observation data based on the relative frequency of dominant male–subdominant male agonistic interactions over 4 years and subdominant males' FID measured over 1 year. Individual propensity for transient mating attempts was not significantly repeatable and did not significantly predict reproductive success or somatic cost during the mating season. Individuals varied consistently in FID, and although repeatable, FID was not related to reproductive success or somatic cost. Proximate state‐dependent or social mechanisms may be driving decision‐making with respect to mating effort, whereas consistent between‐individual differences in FID may be maintained by mechanisms unrelated to life‐history trade‐offs involving productivity.     

Red clothing increases perceived dominance,aggression and anger

The presence and intensity of red coloration correlate with male dominance and testosterone in a variety of animal species, and even artificial red stimuli can influence dominance interactions. In humans, red stimuli are perceived as more threatening and dominant than other colours, and wearing red increases the probability of winning sporting contests. We investigated whether red clothing biases the perception of aggression and dominance outside of competitive settings, and whether red influences decoding of emotional expressions. Participants rated digitally manipulated images of men for aggression and dominance and categorized the emotional state of these stimuli. Men were rated as more aggressive and more dominant when presented in red than when presented in either blue or grey. The effect on perceived aggression was found for male and female raters, but only male raters were sensitive to red as a signal of dominance. In a categorization test, images were significantly more often categorized as ‘angry’ when presented in the red condition, demonstrating that colour stimuli affect perceptions of emotions. This suggests that the colour red may be a cue used to predict propensity for dominance and aggression in human males.     

Differential effects of two dominant plant species on community structure and invasibility in an old-field ecosystem

Aims In this study, we examined the effects of Solidago altissima (hereafter Solidago) and two species in the genus Verbesina, Verbesina virginica and Verbesina occidentalis (hereafter Verbesina), on the structure of an old-field plant community and establishment by an invasive plant species, Lespedeza cuneata (hereafter Lespedeza).Methods We removed Solidago, Verbesina and both Solidago and Verbesina from 4-m 2 plots in an intact old-field community during two growing seasons. We then quantified the effects of these removals on richness, evenness, diversity and composition of the subdominant plant community. We also measured the total aboveground biomass and the aboveground biomass of the subdominant community. To assess how these removals affected establishment by Lespedeza, we planted 20 seeds in each plot and tracked seedling emergence and survival for one growing season.Important findings Subdominant community evenness and Shannon diversity were higher in plots from which Solidago and Verbesina were removed relative to control plots. However, there were no effects of dominant species removal on species richness or composition of the subdominant community. Total aboveground biomass was not affected by dominant species removal, suggesting that the community of subdominant species exhibited compensation. In fact, subdominant community biomass was greater when Solidago, but not Verbesina, was removed. Light availability was also greater in plots where Solidago was removed relative to control plots throughout the growing season. In addition, removal of dominant species, in particular Solidago, indirectly reduced the emergence, but not survival, of Lespedeza seedlings by directly promoting subdominant community biomass. Taken together, our results suggest that dominant old-field plant species affect subdominant community structure and indirectly promote establishment by Lespedeza .     

Reproduction in the endangered African wild dog: basic physiology, reproductive suppression and possible benefits of artificial insemination

The African wild dog (Lycaon pictus) is an endangered exotic canid with less than 5500 animals remaining in the wild. Despite numerous strategies to conserve this species, numbers of free-living animals are in decline. It is a highly social species with a complex pack structure: separate male and female dominant hierarchies with, typically, participation of subdominant adults in the rearing of the dominant breeding pairs' pups. Basic reproductive knowledge is largely missing in this species, with only limited information available on the profile of reproductive hormones, based on non-invasive endocrine monitoring. The dominant or alpha male and female are reproductively active and the subdominants are generally reproductively suppressed. However, the occasional production of litters by subdominant females and evidence of multiple paternity within litters suggests that fertility of subordinates is not completely inhibited. In this respect, there are still considerable gaps in our knowledge about the mechanisms governing reproduction and reproductive suppression in African wild dogs, particularly the influence of dominance and pack structure on both male and female fertility. Given concerns over the long-term survival of this species, further research in this area is essential to provide valuable information for their captive breeding and conservation. Reproductive information can also be applied to the development of Assisted Reproductive Techniques for this species; the utility of which in African wild dog conservation is also discussed.     

Strength of asymmetric competition between predators in food webs ruled by fluctuating prey: the case of foxes in tundra

In food webs heavily influenced by multi‐annual population fluctuations of key herbivores, predator species may differ in their functional and numerical responses as well as their competitive ability. Focusing on red and arctic fox in tundra with cyclic populations of rodents as key prey, we develop a model to predict how population dynamics of a dominant and versatile predator (red fox) impacted long‐term growth rate of a subdominant and less versatile predator (arctic fox). We compare three realistic scenarios of red fox performance: (1) a numerical response scenario where red fox acted as a resident rodent specialist exhibiting population cycles lagging one year after the rodent cycle, (2) an aggregative response scenario where red fox shifted between tundra and a nearby ecosystem (i.e. boreal forest) so as to track rodent peaks in tundra without delay, and (3) a constant subsidy scenario in which the red fox population was stabilized at the same mean density as in the other two scenarios. For all three scenarios it is assumed that the arctic fox responded numerically as a rodent specialist and that the mechanisms of competition is of a interference type for space, in which the arctic fox is excluded from the most resource rich patches in tundra. Arctic fox is impacted most by the constant subsidy scenario and least by the numerical response scenario. The differential effects of the scenarios stemmed from cyclic phase‐dependent sensitivity to competition mediated by changes in temporal mean and variance of available prey to the subdominant predator. A general implication from our result is that external resource subsidies (prey or habitats), monopolized by the dominant competitor, can significantly reduce the likelihood for co‐existence within the predator guild. In terms of conservation of vulnerable arctic fox populations this means that the likelihood of extinction increases with increasing amount of subsidies (e.g. carcasses of large herbivores or marine resources) in tundra and nearby forest areas, since it will act to both increase and stabilize populations of red fox.     

Protective efficacy of serially up-ranked subdominant CD8+ T cell epitopes against virus challenges

Immunodominance in T cell responses to complex antigens like viruses is still incompletely understood. Some data indicate that the dominant responses to viruses are not necessarily the most protective, while other data imply that dominant responses are the most important. The issue is of considerable importance to the rational design of vaccines, particularly against variable escaping viruses like human immunodeficiency virus type 1 and hepatitis C virus. Here, we showed that sequential inactivation of dominant epitopes up-ranks the remaining subdominant determinants. Importantly, we demonstrated that subdominant epitopes can induce robust responses and protect against whole viruses if they are allowed at least once in the vaccination regimen to locally or temporally dominate T cell induction. Therefore, refocusing T cell immune responses away from highly variable determinants recognized during natural virus infection towards subdominant, but conserved regions is possible and merits evaluation in humans.     

Dominant clonotypes within HIV-specific T cell responses are programmed death-1high and CD127low and display reduced variant cross-reactivity

HIV epitope-specific T cell responses are often comprised of clonotypic expansions with distinct functional properties. In HIV(+) individuals, we measured programmed death-1 (PD-1) and IL-7Rα expression, MHC class I tetramer binding, cytokine production, and proliferation profiles of dominant and subdominant TCR clonotypes to evaluate the relationship between the composition of the HIV-specific T cell repertoire and clonotypic phenotype and function. Dominant clonotypes are characterized by higher PD-1 expression and lower C127 expression compared with subdominant clonotypes, and TCR avidity positively correlates with PD-1 expression. At low peptide concentrations, dominant clonotypes fail to survive in culture. In response to stimulation with peptides representing variant epitopes, subdominant clonotypes produce higher relative levels of cytokines and display greater capacity for cross-recognition compared with dominant clonotypes. These data indicate that dominant clonotypes within HIV-specific T cell responses display a phenotype consistent with ongoing exposure to cognate viral epitopes and suggest that cross-reactive, subdominant clonotypes may retain greater capacity to suppress replication of viral variants as well as to survive in the absence of strong antigenic signaling.     

Comparative food web structure of larval macrolepidoptera and their parasitoids on two riparian tree species

Single species or groups of species can be subjected to differing levels of parasitism on different plants. Previous studies have reported that parasitism of larval macrolepidoptera in an assemblage on box elder (Acer negundo L.) was significantly greater than on black willow [Salix nigra (Marsh)]. In this study, quantitative food webs, parasitoid overlap diagrams and other food web attributes were used to identify and describe direct and indirect interactions, and to compare assemblages on each tree species. These comparisons helped identify possible mechanisms explaining the differential parasitism observed. Although links among numerically dominant species in each assemblage were not strong, links between numerically dominant and subdominant species were strong. That is, numerically dominant and subdominant species interacted via shared parasitoids. The degree of parasitoid sharing by numerically dominant and subdominant species differed in each tree. There was less sharing of parasitoids on black willow than on box elder. Further, on box elder, the majority of parasitoids affecting numerically subdominant species originated from numerically dominant species, unlike in willow. These results lead to a working hypothesis—the source/nursery hypothesis—that proposes that community-wide levels of parasitism are highest in circumstances in which numerically subdominant species share parasitoid species in common with numerically dominant species, and most parasitoids attacking subdominant species originate from numerically dominant species. Thus, differences in degree of sharing and the types of herbivores sharing parasitoids may explain differential parasitism. Further, the source/nursery hypothesis may explain why the vast majority of species in most assemblages are numerically subdominant. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.