Assessment of Potential Predation Costs of Male Decoration and Courtship Display in Wolf Spiders Using Video Digitization and Playback

We used video digitization and playback techniques to examine the potential predation risk of leg decorations and visual displays of male wolf spiders, which vary across the genus Schizocosa (Araneae: Lycosidae). Video images of courting males of four Schizocosa species were modified by adding or removing tufts and presented on LCD minitelevisions to the wolf spider Hogna helluo, a common predator of Schizocosa. Predatory responses of H. helluo varied significantly among stimuli and were highest for S. ocreata (which has decorative tufts and leg-waving displays) and lower for S. rovneri, S. duplex, and S. uetzi (which lack decorations and visual displays). Removal of tufts from S. ocreata significantly reduced predatory responses of H. helluo, but addition of tufts to other species had no effect. Results suggest that leg decorations may increase detection of active leg-waving displays and thereby increase predation risk.     

Mating Behavior, Sexual Selection, and Copulatory Courtship in a Promiscuous Beetle

The function of male movements during copulation is unclear. These movements may be a result of the necessary mechanics of insemination, or they may also have further function, for instance, stimulating or courting a female during mating, perhaps influencing female mate choice. We present data from three experiments exploring the mating behavior and copulatory movements of the highly promiscuous beetle Psilothrix viridicoeruleus. Male mating success in the struggle over mating was not related to male or female size (measured by weight) but successful males were more vigorous in terms of copulatory movements. These males took longer to mount females but copulated longer and remained mounted longer. We discuss these results in terms of the mating system of Psilothrix and also in terms of observations of the timing of insemination during copulation. We suggest that copulatory movements in this species are best understood as copulatory courtship.     

The Influence of Parental Status on Courtship Effort in a Paternal Caring Fish

It is widely assumed that caring for young limits the motivation of parents to seek additional mating opportunities. However, in situations where parental care does not involve direct provisioning of the offspring, but rather activities directed at the brood as a whole (e.g. guarding), it may be more efficient for parents to care for large numbers of young at once. This may be especially true for species with exclusive paternal care, with fathers that have recently acquired a brood of young potentially benefitting from vigorously courting prospective mates, so as to maximise their chances of attaining a large number of young to rear together. We experimentally tested this hypothesis in the three‐spined stickleback (Gasterosteus aculeatus), a fish with male only care. Contrary to our predictions, we found no evidence of any differences in courtship between recently spawned egg‐tending fathers and males that had not spawned. However, males that were permitted to spawn, but then had their eggs taken from them, courted less vigorously. Together, the results of our study suggest that the potential benefits of vigorous courtship in terms of acquiring additional young may be offset by additional costs faced by parental males.     

Courtship Roles of Male and Female European Earwigs, Forficula auricularia L. (Dermaptera: Forficulidae), and Sexual Use of Forceps

Detailed observations of the courtship and mating of the European earwig Forficula auricularia revealed a complex of sexual behaviors for both males and females. A sequential analysis of the transition frequencies between male preceding-following behaviors showed that courtship is intricate and nonstereotyped. The significance of the male forceps was demonstrated by their use in early courtship with displays and later use as a tactile stimulus for the female. A study of males from which the forceps had been removed showed no mating by altered males. Male forcep length was bimodally distributed and positively allometric, while female forcep length was normally distributed. Males with longer forceps did not have a mating advantage. Receptive females were behaviorally active during courtship. The possible evolutionary development of the sexual dimorphism of the earwig is discussed.     

Predators, reproductive parasites, and the persistence of poor males on leks

Lekking males are thought to face strong directional selectionon secondary sexual traits. How variation in male traits canpersist under these conditions remains problematic (the lekparadox). Here, we present several game-theoretic models thatshow that avoidance of costly and mobile predators, sneakers,or brood parasites (enemies) leads to variation in female choice.This can result in maintenance of variation in male quality."Enemies" will congregate around higher quality males. Femalesmust then trade-off the benefits of mating with high-qualitymales against the increased risk of enemies. At equilibrium,the models predict a positive correlation between the qualityof a male and the proportions of both enemies and females visitinghim. In the first model, we use this framework to predict thelowest quality male on the lek that will receive any matings.In the second model, we examine the influence of this female-enemygame on the maintenance of variation in male quality. Low-qualitymales are likely to persist when enemies are costly to femalesor occur at high density, and when there is some spatial structureon the lek, so that neighboring males are typically of similarquality. If enemies are more costly to males than to females,high-quality males may benefit from receiving fewer female visits.In the third model, we consider the special case when enemiesare male reproductive parasites. These models illustrate theimportance of considering the simultaneous decisions of multipleplayers in mate choice games.     

Courtship in long-legged flies (Diptera: Dolichopodidae): function and evolution of signals

Analyzing the courtship behavior of long-legged flies (Diptera:Dolichopodidae), we focus on the evolutionary development ofcourtship signals. Long-legged flies may serve as a model forthis evolutionary process, because males of some species presentsexually dimorphic badges during courtship, whereas others donot exhibit such conspicuous signals but present lavish courtshipbehavior, including dynamic flight maneuvers. A comparison ofthese two groups within a single taxonomic family provides insightinto the evolution of courtship signals and the correspondingbehavior. Males of the closely related Empididae do not possesssuch badges. Within the super-family Empidoidea, we proposean evolutionary shift from dynamically courting and mating onthe wing (in Empididae) to courting and mating on ground (inDolichopodidae), accompanied by signaling through badge-waving.By comparing previously published data and observations on courtshipbehavior in Dolichopodidae, we present the hypothesis that thelatter replaced the former energetically expensive behavioras a case of automimicry and sensory trap.     

Courtship success and multivariate analysis of sexual selection on morphometric traits inDrosophila buzzatii (Diptera: Drosophilidae)

Using wild-reared flies, we examined sexual selection on five phenotypic traits (thorax length, wing length, wing width, head width, and face width) inDrosophila buzzatii, by scoring copulatory status in nine mass mating cages. Only male face width was identified as a direct target of sexual selection in an analysis of selection gradient, while indirect selection was present on all other studied traits, as expected from their correlations with face width. In contrast to males, there was no indication of selection in females. Nor was there evidence of assortative mating. The suggested direct selection on face width seems to take place during licking behavior of the courtship and might be related to courtship feeding. This study suggests that courtship success gives rise to indirect selection on body size.     

The Use of Digitally-modified Videos to Study the Function of Ornamentation and Courtship in the Guppy, Poecilia reticulata

The use of video playback, digitally-modified video images, and animations is a potentially powerful tool for exploring the interactions between morphological and behavioral components of complex sexually selected traits. The utility of digitally-modified video was evaluated by the responses of females to male images in which either the behavioral components of display or the colors of ornamentation were manipulated. Females were presented with paired male images that varied only in the size of the orange or blue spot on the body (19.1% vs. 8.6%), courtship duration (7sec vs. 2.3sec), or courtship rate (3 displays min^-1 vs. 1 display min^-1). Females preferred male images with more vigorous courtship displays (both duration and rate) but did not discriminate between images differing in spot size. The results of the present study suggest that females discriminate more strongly between variation in male behavior than in their morphological attributes. The results of morphological manipulations should be interpreted with caution, however, because several factors could have contributed to the lack of female responses to color spot variation. Among them are lowered resolution of the computer image, which fails to capture the precision and complexity of the color pattern. Despite these potential difficulties, digitally-modified video promises to be a powerful method to study complex visual communication systems, where the function of and interaction between the various morphological and behavioral components is as yet poorly understood.     

The Relationship Among Swimming Performance, Courtship Behavior, and Carotenoid Pigmentation of Guppies in Four Rivers of Trinidad

In the laboratory, courtship behavior and carotenoid pigmentation of male guppies are condition-dependent traits, since their expression is affected by physical vigor and environmental factors such as water velocity and diet. Whether these relationships exist in guppies under field conditions is yet to be determined. We compared the swimming performance, courtship behavior, and carotenoid pigmentation of guppies from headwater and downstream localities in four rivers of Trinidad. Swimming performance and courtship behavior of males differed among rivers and between headwater and downstream sites. Guppies from headwater sites swam significantly faster and had higher display rates than those from downstream sites. Mean swimming performance across sites was positively correlated with mean water velocity, but was correlated with the number of orange color spots (carotenoid pigment) in only one river. These results indicate that the courtship behavior of Trinidadian guppies is condition-dependent because the amount of display behavior is positively correlated to swimming performance, a measure of physical endurance. The proximal cause for this condition-dependence may be predator induced variation in microhabitat use by guppies in headwater and downstream locations.     

The Influence of Pedipalp Autotomy on the Courtship and Mating Behavior of Pardosa milvina (Araneae: Lycosidae)

Male Pardosa milvina wolf spiders use their pedipalps both for copulation and courtship. Pedipalp loss is significantly more common among adult males compared to females. We measured the courtship and mating effects associated with the loss of one or both pedipalps among adult male P. milvina. Pedipalp loss significantly reduced courtship intensity, but had no influence on mounting success. Intact males were less likely to be cannibalized and suffered fewer predatory attacks by females than autotomized males. Loss of the left pedipalp resulted in significantly less intense courtship, higher female aggression levels, and delayed onset of courtship whereas loss of the right pedipalp minimally affected male and female behavior relative to intact males. Pedipalp displays may function in reducing female aggression rather than increasing female receptivity.     

田间蜘蛛集团对飞虱的每日捕食量与室内、盆栽水稻的捕食作用比较

采用控制论中的脉冲采样法结合杀死飞虱计数法研究了田间蛛蛛对飞虱的每日捕食量估计并与室内,盆栽罩笼水稻功能反应的捕食作用进行了比较,结果表明田间蜘蛛平均每头每日对飞虱的捕食量为0.669头,这一捕食量比室内和盆栽水稻的捕食量要小得多;田间捕食百分率与飞虱密度呈二次抛物线关系,即飞虱低密度和高密度捕食百分率均低于中等密度,在每穴10头飞虱左右,捕食量和捕食百分率最高,在有一定存量蜘蛛时,捕食量与微蛛,狼蛛数量呈显著的二元线性回归关系,但偏相关系数为负,由此表明随蜘蛛密度的增加捕食量反而下降,这与一些多物种共存系统和田间罩笼的研究结果相一致。     

Group Effects and Background Color Patterns Affect the Exploratory Behavior of Tree Sparrows

Exploratory behavior serves the function of acquiring information when facing environmental uncertainty, thus plays an important role for animals living on patchy or ephemeral resources. Our study tested the hypothesis that exploratory behavior is affected by ecological factors associated with the risk of predation. We conducted experiments to examine exploration behavior of wild‐caught Eurasian tree sparrows (Passer montanus) under the influences of background color patterns (white or camouflaged) and group sizes (single vs. five sparrows). We further conducted two‐pattern choice experiments and offered sparrows backgrounds combining those two color patterns. In comparisons with single sparrows, flocking sparrows had shorter landing latencies, started exploring sand patches earlier, spent less total time on the ground before pecking at the first patch and nearly successfully located and pecked all patches. In contrast, sparrows responded nearly indifferently to the two single‐pattern backgrounds; yet when given a choice, sparrows still favored the camouflaged portion in the two‐pattern backgrounds and first landed more frequently there. Twice as many patches were left untouched on the two‐pattern backgrounds, mostly by single sparrows, than on both types of single‐pattern backgrounds. In tests of flocks, sparrows that first landed on the ground to initiate exploration had a higher chance to also first explore a sand patch than random expectation on single‐pattern backgrounds, but not necessarily on two‐pattern backgrounds. Our results demonstrate context‐specific effects of social exploration, suggest possible influence of individual variation and offer evidence for advantages of group living in situations where explorers have to cope with environmental uncertainty.     

The Effect of Limb Loss on the Courtship and Mating Behavior of the Wolf Spider Pardosa milvina (Araneae: Lycosidae)

Limb loss is common in the wolf spider Pardosa milvina, appearing in nearly one third of adult males but occurring less frequently among adult females and juveniles. Since males wave their first pair of legs during courtship displays, the reproductive consequences of limb loss may be significant. We measured the courtship and mating effects of the loss of one, two, or four legs among adult male P. milvina. Missing one or two legs did not significantly reduce a male's ability to mate, but missing four legs was detrimental to mating success, reduced both courtship intensity and copulation duration, and increased cannibalism frequency. Results suggest behavioral flexibility in compensating for limited leg loss and a defensive function of the anteriormost legs to thwart female cannibalism attempts.     

棒络新妇和悦目金蛛拖丝超微结构与力学行为

采用SEM对棒络新妇Nephila clavata腹部向上和向下在水平纱窗上爬行时纺出的拖丝、悦目金蛛Argiope amoena捕食拖丝与垂直向下缓慢纺出的拖丝及其圆网的铆钉丝进行了超微结构观察,采用电子单纤强力仪对棒络新妇拖丝与悦目金蛛圆网铆钉丝进行了力学拉伸试验.结果 表明棒络新妇和悦目金蛛拖丝均呈现出一至多根细丝纤维的多样化超微结构特征,其中悦目金蛛圆网铆钉丝还呈现出"S"形似弹簧的结构.两种蜘蛛丝的力学行为和性能与各自的功能要求相一致.蜘蛛能调节拖丝的超微结构、纤维组成和直径大小以适应其在不同环境条件下对力学性能和功能的瞬时需要.研究结果有助于拓宽和加深人们对蜘蛛丝超微结构、力学性能与生物学功能之间关系的认识和理解.     

Spiders,microbes and sex: Bacterial exposure on copulatory organs alters mating behaviour in funnel‐web spiders

Environmental microbes have the potential to be involved in nearly all behavioural processes. For example, mating systems where males use intromittent organs to transfer sperm to females represent a means by which environmental microbes collected by males can breach entry into females' body cavities during mating. However, the degree to which the acquisition of environmental microbes onto important sex structures alters courtship behaviours remains unknown. Here, we collected bacteria from the copulatory organs of Agelenopsis pennsylvanica funnel‐weaving spiders in situ to test whether exposure to bacteria on copulatory organs can alter hosts' courtship behaviour, reproductive success and survival. We used a standardized assay to repeatedly measure each spider's aggressiveness, a behavioural component of both male courtship and female sexual receptivity. Then, we experimentally altered the bacteria present on male and female spiders' copulatory organs with an application of either (a) a mixture of bacteria collected from conspecifics to increase bacterial presence, (b) an antibiotic to reduce bacterial presence or (c) a procedural control. Each spider was paired with a size‐matched spider of the opposite sex whose copulatory organs were unaltered, and we measured the latency until the onset and the duration of courtship. Spiders were then isolated, and we measured each individual's time until death and female fecundity over the next 40 days. We found that female exposure to bacteria had multiple effects on mating dynamics. Males took over four times longer to begin courting females that had been exposed to bacteria compared to unexposed and antibiotic‐treated females. Only when courting these bacteria‐exposed females, males began courtship sooner when females were more aggressive. Lastly, females whose mate had been exposed to bacteria experienced reduced survival. These data suggest that bacteria present on animals' copulatory organs can alter courtship behaviours, female survivorship, and may potentially play a role in mating dynamics.     

Copulatory Courtship in Drosophila: Behavior and Songs of D. birchii and D. serrata

D. birchii and D. serrata, two endemic Australian Drosophila species, have a copulatory courtship. The males of these species begin to court the female after mounting her and often go on with the courtship after the copulation is over. In the present paper we have described behavioral interactions between the male and the female and analyzed acoustic signals produced by the flies during courtship. Species differences were more pronounced in female than in male behavior. Variation within the species was obvious in the relative proportions of time the flies spent in different behaviors. Even though courtship took place nearly solely during copulation, some remains of precopulatory courtship were observed in both species. It is suggested that copulatory courtship exhibited by D. birchii and D. serrata flies is a derived rather than a primitive character.     

Courtship behavior,swimming performance,and microhabitat use of Trinidadian guppies

Synopsis We document differences in the use of microhabitats, male courtship behavior, and swimming performance of populations from headwater and downstream sites in two rivers of the Oropuche drainage in Trinidad. Guppies from headwater sites used microhabitats with higher water velocities, had a higher swimming performance, and were less patchily distributed than guppies from downstream sites. Although males from the headwater and downstream sites had similar display rates, males from headwater sites displayed in microhabitats with higher velocities (riffles) whereas males in downstream sites courted in still pools. Subtle effects of female choice maintain the honesty of male courtship behavior in various microhabitats. In downstream sites, where predators impose a survivorship cost on ornamental males, swimming performance was positively correlated with area of carotenoid ornamentation. In headwater sites, males frequently displayed in fast-flowing water, thus paid a higher metabolic cost of courtship. Interactions between characteristics of the physical habitat and predation pressure not only affect the distribution of guppies, but also have subtle effects on the types of condition-dependent traits favored by females.     

Bumpus in the snake den: effects of sex, size, and body condition on mortality of red-sided garter snakes

Huge breeding aggregations of red-sided garter snakes (Thamnophis sirtalis parietalis) at overwintering dens in Manitoba provide a unique opportunity to identify sources of mortality and to clarify factors that influence a snake's vulnerability to these factors. Comparisons of sexes, body sizes, and body condition of more than 1000 dead snakes versus live animals sampled at the same time reveal significant biases. Three primary sources of mortality were identified. Predation by crows, Corvus brachyrhynchos (590 snakes killed), was focussed mostly on small snakes of both sexes. Crows generally removed the snake's liver and left the carcass, but very small snakes were sometimes brought back to the nest. Suffocation beneath massive piles of other snakes within the den (301 dead animals) involved mostly small males and (to a lesser extent) large females; snakes in poor body condition were particularly vulnerable. Many emaciated snakes (n = 142, mostly females) also died without overt injuries, probably due to depleted energy reserves. These biases in vulnerability are readily interpretable from information on behavioral ecology of the snakes. For example, sex biases in mortality reflect differences in postemergence behavior and locomotor capacity, the greater attractiveness of larger females to males, and the high energy costs of reproduction for females.