Spatio-Temporal Dynamics of Field Cricket Calling Behaviour: Implications for Female Mate Search and Mate Choice

Amount of calling activity (calling effort) is a strong determinant of male mating success in species such as orthopterans and anurans that use acoustic communication in the context of mating behaviour. While many studies in crickets have investigated the determinants of calling effort, patterns of variability in male calling effort in natural choruses remain largely unexplored. Within-individual variability in calling activity across multiple nights of calling can influence female mate search and mate choice strategies. Moreover, calling site fidelity across multiple nights of calling can also affect the female mate sampling strategy. We therefore investigated the spatio-temporal dynamics of acoustic signaling behaviour in a wild population of the field cricket species Plebeiogryllus guttiventris. We first studied the consistency of calling activity by quantifying variation in male calling effort across multiple nights of calling using repeatability analysis. Callers were inconsistent in their calling effort across nights and did not optimize nightly calling effort to increase their total number of nights spent calling. We also estimated calling site fidelity of males across multiple nights by quantifying movement of callers. Callers frequently changed their calling sites across calling nights with substantial displacement but without any significant directionality. Finally, we investigated trade-offs between within-night calling effort and energetically expensive calling song features such as call intensity and chirp rate. Calling effort was not correlated with any of the calling song features, suggesting that energetically expensive song features do not constrain male calling effort. The two key features of signaling behaviour, calling effort and call intensity, which determine the duration and spatial coverage of the sexual signal, are therefore uncorrelated and function independently.     

Territoriality and Male Mating Success in the Dart-poison Frog,Epipedobates femoralis (Dendrobatidae,Anura)

The social and reproductive behaviour of the dart-poison frog, Epipedobates femoralis, was studied in Amazonian Peru for 14 months. Males defended territories with advertisement calls and, ultimately, fighting. Territory size ranged from 0.25 to 26 m² and was positively correlated with duration of residence and calling activity of the owner. Females were not territorial and were never attacked when approaching calling males. Males and females only mated once and females sampled calling males before mating. Male mating success was closely correlated with territory size and calling activity. No correlation was found between male body size and mating success. Territories provide residents with sufficient space for mate attraction and reproduction without interference from rivals. Since territory size is dependent on calling activity which involves high energetic costs, it is suggested that territory size reveals male quality.     

Mating behaviour and male mating success in the green treefrog

Green treefrogs, Hyla cinerea, at a study site in eastern Georgia behaved as prolonged breeders: there were many more males present each night than females, the arrival of which was unpredictable. Individual males were usually consistent in their behaviour during a single night, and were most often observed calling. There was a weak, negative correlation between male size (snout-vent length, unless otherwise stated) and the frequency of satellite behaviour, defined as a non-calling male's being situated near a calling male. In 2 of 3 years, the mean size of males observed as satellites was less than that of the calling males with which they were associated on a given night; however, many satellites were the same size or larger than calling males. The distributions of matings per male during three seasons were not significantly different than Poisson distributions with the same means. Individual mating success was best predicted by attendance at the breeding site; mating success was negatively related to the frequency of satellite behaviour in some analyses, but very little of the variance was explained. An exhaustive series of analyses failed to show any pattern of size-dependent mating, including weight-assortative mating, even when males that were frequently satellites were excluded. The relative sizes of males and females in amplexus had little effect on fertilization success. On a seasonal basis, males were clumped in their spatial distribution, and matings tended to occur where male density was highest. Individual males were highly variable in their patterns of movement, which were not correlated with size or mating success. Mating success was also unrelated to the frequency (Hz) of the low-frequency spectral peak in the advertisement call of the male; male size and weight were negatively correlated with the frequency of the low-frequency peak.     

Lifetime mating success in the damselfly Coenagrion puella

Lifetime mating success of male azure damselflies (Coenagrion puella) was measured in a natural population. The major determinant of mating success is the number of days a male spends at the breeding site, which is mostly determined by a male's adult lifespan. Long-lived males have a higher mating rate than short-lived males, and daily mating rate increases with age up to 6 days, then falls. Large males live longer, but have a lower daily mating rate than small males. These effects of size are very weak, accounting for no more than 2% of the daily variance in mating success. The only overall effect of size on lifetime mating success is that males at both extremes of the size distribution are more likely to fail to mate. Chance differences in the number of females encountered are sufficient to account for the remaining variance in mating success. The weather is also shown to have a major effect on mating success. We draw attention to the ways in which it may be misleading to draw conclusions about the action of sexual selection from studies of daily, rather than lifetime, reproductive success. We provide evidence to support the view that variance in male reproductive success is neither evidence for sexual selection, nor a measure of its intensity.     

Acoustic Preference of Frog‐Biting Midges (Corethrella spp) Attacking Túngara Frogs in their Natural Habitat

In many animals, males aggregate to produce mating signals that attract conspecific females. These leks, however, also attract eavesdropping predators and parasites lured by the mating signal. This study investigates the acoustic preferences of eavesdroppers attracted to natural choruses in a Neotropical frog, the túngara frog (Engystomops pustulosus). In particular, we examined the responses of frog‐biting midges to natural variation in call properties and signaling rates of males in the chorus. These midges use the mating calls of the frogs to localize them and obtain a blood meal. Although it is known that the midges prefer complex over simple túngara frog calls, it is unclear how these eavesdroppers respond to natural call variation when confronted with multiple males in a chorus. We investigated the acoustic preference of the midges using calling frogs in their natural environment and thus accounted for natural variation in their call properties. We performed field recordings using a sound imaging system to quantify the temporal call properties of males in small choruses. During these recordings, we also collected frog‐biting midges attacking calling males. Our results revealed that, in a given chorus, male frogs calling at higher rates and with higher call complexity attracted a larger number of frog‐biting midges. Call rate was particularly important at increasing the number of midges attracted when males produced calls of lower complexity. Similarly, call complexity increased attractiveness to the midges especially when males produced calls at a low repetition rate. Given that female túngara frogs prefer calls produced at higher repetition rates and higher complexity, this study highlights the challenge faced by signalers when increasing attractiveness of the signal to their intended receivers.     

Callers and satellites in the natterjack toad: evolutionarily stable decision rules

Male natterjack toads, Bufo calamita, sometimes called to attract females and sometimes behaved as silent satellites, attempting to intercept females attracted by callers. Small males with low intensity calls most frequently adopted the satellite tactic and preferred to parasitize the loudest callers. Because body size and call intensity were highly correlated with male mating success, small males with weak calls were at a reproductive disadvantage, and probably achieved greater success by exploiting the displays of larger, louder males than by calling themselves. The behaviour adopted by individual males in a given situation was predicted by a game theory model which assumed that males used an evolutionarily stable decision rule when choosing between alternative mating tactics. However, the model provided close agreement with observed behaviour only when it assumed that males have imperfect information about the behaviour of competitors. It is concluded that male toads adopt a conditional strategy which depends on their attractiveness to females. By switching between mating tactics appropriately, males maximized expected mating success within the constraint of the information available to them. The decision rule of the model qualitatively corresponds to a proximate mechanism that males appeared to use when switching between tactics. The model offers insights into the behaviour of other species in which males display in groups to attract females.     

Temporal spacing of breeding activity in the natterjack toad,Bufo calamita

Summary The reproductive behaviour of the toad Bufo calamita was studied in a large population in the northern Rhineland, Germany. Toads bred at four spatially separated but neighbouring areas including 34 breeding ponds. Three methods were applied to monitor quantitatively the intensity of breeding and migratory activity: capture-mark-recapture, a mechanical tracking device, and radio-telemetry. In 1987 a twofold temporal spacing of breeding activity was observed: (1) division of the reproductive period into early, main, and late breeding periods; (2) subdivision of each breeding period into several short calling periods. Since weather conditions were favourable during most of the reproductive period, environmental factors contributed little (23.4%–41.0%) to the temporal variation in breeding intensity as shown by multivariate statistics. The period of vocalization (April to August) included the activity of three distinct male groups. The first group called from April to mid-May (2 calling periods), the second from May to early July (5 calling periods) and the third from mid-July to August (2 calling periods). Within a calling period most males stayed near their calling sites and migratory activity was low. Extensive movements were detected when a new group of males immigrated from the feeding regions to the breeding areas and males that had been calling previously emigrated, at least partly. However, exchange of males among the neighbouring breeding choruses were clearly audible. It is suggested that the energetic costs of vocalization impeded continuous calling activity in individuals and accounted for the periodical variations in chorus size. The short-time variations of breeding activity therefore probably reflect the physiological limits of toads in a situation where the weather permits continuous reproductive activity.     

Age Influence on Sexual Behavior of the Lesser Cornstalk Borer, <Emphasis Type="Italic">Elasmopalpus lignosellus</Emphasis> (Zeller) (Lepidoptera: Pyralidae)

The objective of this work was to evaluate the reproductive behavior and response of Elasmopalpus lignosellus (Zeller) males to calling females. Frequency of mating was recorded in couples during the first 7 days of the adult stage. Calling behavior of females was observed during the first 4 days of the adult stage and responses of males, in the same age intervals, to calling females were recorded in wind tunnel bioassays. The maximum number of matings occurred when the couple was between 24 and 48 h old. The scotophase period significantly influenced mating behavior, which peaked between 6 and 8 h of darkness and the mean mating duration was 93.9 ± 4.2 min. Calling females, when evaluated in a wind tunnel, attracted significantly more males than in bioassays with clean air (control). The number of individuals in calling behavior was significantly lower for females that were between 0 to 24 h old compared to the other females evaluated, but this did not influence male response. A lower proportion of males between 48 to 72 h old responded to calling females and these responses were delayed in comparison with males of other ages (0 to 24, 24 to 48, and 72 to 96 h old). These results indicate that the age of E. lignosellus males influences the response to conspecific calling females.     

Inter-male Spacing and Aggression in African Painted Reed Frogs,Hyperolius marmoratus

Inter-male spacing and the role of aggression in the maintenance of spatial organization was examined in choruses of Hyperolius marmoratus males housed in a semi-natural enclosure. The effects of chorus size on spacing patterns, nearest neighbour distances and male aggressive behaviour were examined. Males were found to reduce nearest neighbour distances as chorus size increased. This was accompanied by a shift in spacing pattern from even in small choruses (5–9 males) to random in choruses of 10 to 13 males. In choruses of 14, spacing patterns were once again even. The reason for these shifts is unclear but may reflect a sudden, rather than gradual increased tolerance by individuals to high neighbour call intensity as space to call from becomes more limited. The level of male aggression was influenced by chorus size and the time of night. In general, more aggressive interactions occurred in high density choruses. However, this did not translate into higher levels of individual male aggression as density increased. Individual male aggression was high in early evening choruses and declined to a minimum at peak chorusing time. High levels of aggression during early evening may reflect the establishment of calling sites by males, while the drop in aggression at peak chorusing time may occur in response to the presence of females in the chorus at this time or as a consequence of masking of neighbours calls.     

Male moth songs tempt females to accept mating: the role of acoustic and pheromonal communication in the reproductive behaviour of Aphomia sociella

Background

Members of the subfamily Galleriinae have adapted to different selective environmental pressures by devising a unique mating process. Galleriinae males initiate mating by attracting females with either chemical or acoustic signals (or a combination of both modalities). Six compounds considered candidates for the sex pheromone have recently been identified in the wing gland extracts of Aphomia sociella males. Prior to the present study, acoustic communication had not been investigated. Signals mediating female attraction were likewise unknown.

Methodology/Principal Findings

Observations of A. sociella mating behaviour and recordings of male acoustic signals confirmed that males initiate the mating process. During calling behaviour (stationary wing fanning and pheromone release), males disperse pheromone from their wing glands. When a female approaches, males cease calling and begin to produce ultrasonic songs as part of the courtship behaviour. Replaying of recorded courting songs to virgin females and a comparison of the mating efficiency of intact males with males lacking tegullae proved that male ultrasonic signals stimulate females to accept mating. Greenhouse experiments with isolated pheromone glands confirmed that the male sex pheromone mediates long-range female attraction.

Conclusion/Significance

Female attraction in A. sociella is chemically mediated, but ultrasonic communication is also employed during courtship. Male ultrasonic songs stimulate female sexual display and significantly affect mating efficiency. Considerable inter-individual differences in song structure exist. These could play a role in female mate selection provided that the female''s ear is able to discern them. The A. sociella mating strategy described above is unique within the subfamily Galleriinae.     

Alternative mating tactics in the Great Plains toad

Male Great Plains toads, Bufo cognatus, exhibit two mating tactics. At any time, most males give advertisement calls to attract females, while other males, ‘satellites’, remain silent and station themselves near callers in an attempt to intercept females. Females are usually capable of moving through choruses undetected by males. Those females detected by males can avoid being clasped by quickly darting away; but if clasped, can detach the male by inflating. Females initiated amplexus with callers; subsequently calling males mated with 92% of the females and satellites mated with the remaining 8%. Toads employing the satellite tactic associated with males that had longer calls and that were larger, although call duration was the stronger predictor. The percentage of males exhibiting satellite behaviour during a sampling period varied from 0 to 57%. Several hypotheses explaining satellite frequency were explored, including variation in male density, male quality, and operational sex ratio. Of the variables considered, only two aspects of male density (namely, the number of unmated males per m of shoreline and number of calling males per m shoreline) affected satellite frequency. High male density may cause at least some calling males to lose vocal conspicuousness, thereby favouring satellite behaviour. However, male density accounted for only 17% of the observed variation in satellite frequency. This, plus the fact that up to 74% of marked males switched between tactics, suggests that factors such as higher energetic demands of calling may affect satellite frequency.     

Male Reproductive Tactics in an Explosive Breeding Toad Population

American toad (Bufo amencanus) males use one of two differentreproductive tactics. Some males are stationary and call. Othersare silent and mobile. Based on field studies, I developed acomputer program that simulates the behavior of females andmales to determine the probability of mating success of malesengaging the different tactics and the factors that effect malereproductive success. Field studies indicate that non-calling males can be successful.Non-calling males were more numerous and smaller than callingmales. Population size changed greatly both between and withinnights. Contact rates for non-calling males were greater thanthose for calling males. The results of the preliminary simulations indicate that malemating success is a function of the population size and theoperational sex ratio. In small populations, contact rate hasno effect on male success. The effect of contact rate on malesuccess has not been tested in large populations. In large populations,mating success is also a function of the ratio of calling tonon-calling males. Generally, in small populations (n > 20)calling males are more successful than non-calling males. Inlarge populations (n > 40) the success of noncalling malesis equal to or greater than the success of calling males.     

Courtship and Mating Behavior of the Cockroach <Emphasis Type="Italic">Oxyhaloa deusta</Emphasis> [Thunberg, 1784] (Blaberidae,Oxyhaloinae): Attraction Bioassays and Morphology of the Pheromone Sources

In this paper, we focus on the reproductive behavior of the cockroach Oxyhaloa deusta. Within the Oxyhaloinae subfamily, mating strategies and glandular areas involved in pheromone production have been studied for several genera belonging to the Nauphoetini and Gromphadorhini tribes. However, this is the first time that courtship and mating behavior have been explored within the genus Oxyhaloa, and in a more general way within the Oxyhaloini tribe. This work, comprising behavioral observations, olfactometric bio-assays and morphological data, highlights unusual behaviors and novelties in potential sex pheromone gland location, in both males (tergite 8) and females (supra-valvular area). Surprisingly, our results also indicate that mate finding is initiated by the female. This is quite remarkable inasmuch as the Oxyhaloinae subfamily is the only cockroach group in which males initiate mate finding by means of a sex pheromone, emitted during the calling posture by extending abdominal tergites. In the Oxyhaloinae subfamily, this occurrence of various reproductive behavioral patterns (including all the mating patterns known at present in Blattaria) in closely-related species is striking, and makes this group a suitable model for studying the changes in mating behavior correlated with the location of sexual glands.     

Mating strategy shifts in male green treefrogs (Hyla cinerea): An experimental study

Four field experiments were designed to study calling and satellite mating strategies in the green treefrog, Hyla cinerea. (1) The calling male was removed from 19 satellite associations and 11 of the 19 satellite males began calling. (2) After the calling male was removed from 10 satellite associations, a speaker broadcast synthetic mating calls. All of the satellite males oriented to the speaker. (3) Synthetic mating calls were played back to 14 calling males. Eleven males stopped calling and oriented to the speaker during at least one trial. (4) Sequences of synthetic mating calls and synthetic encounter calls were broadcast to 12 calling males. Nine males became satellites when the speaker emitted mating calls; none did so when encounter calls were presented.     

Resolving mechanisms of short-term competitive fertilization success in the red flour beetle

Postcopulatory sexual selection occurs when sperm from multiple males occupy a female’s reproductive tract at the same time and is expected to generate strong selection pressures on traits related to competitive fertilization success. However, knowledge of competitive fertilization success mechanisms and characters targeted by resulting selection is limited, partially due to the difficulty of discriminating among sperm from different males within the female reproductive tract. Here, we resolved mechanisms of competitive fertilization success in the promiscuous flour beetle Tribolium castaneum. Through creation of transgenic lines with fluorescent-tagged sperm heads, we followed the fate of focal male sperm in female reproductive tracts while tracking paternity across numerous rematings. Our results indicate that a given male’s sperm persist and fertilize eggs through at least seven rematings. Additionally, the proportion of a male’s sperm in the bursa (the site of spermatophore deposition), which is influenced by both timing of female’s ejecting excess sperm and male size, significantly predicted paternity share in the 24 h following a mating. Contrary to expectation, proportional representation of sperm within the female’s specialized sperm-storage organ did not significantly predict paternity, though spermathecal sperm may play a role in fertilization when females do not have access to mates for longer time periods. We address the adaptive significance of the identified reproductive mechanisms in the context of T. castaneum’s unique mating system and ecology.     

The Sounds of Silence as an Alarm Cue in Túngara Frogs,Physalaemus pustulosus

In many species males vocally advertise for mates in choruses and these choruses serve as acoustic beacons to conspecific females as well as to eavesdropping predators and parasites. Chorusing will often cease in response to disturbances, such as the presence of predators. In some cases the cessation is so rapid and over such a large area that it seems improbable that males are all responding directly to the same local disturbance. Here, we demonstrate experimentally in Neotropical túngara frogs, Physalaemus pustulosus, that the cessation of calling by males spreads rapidly through the chorus. The cessation of chorusing in response to the cessation of playbacks of three calling males is more effective in inducing chorus cessation than is the cessation of one male calling. When three males are calling, the cessation of complex calls is more effective in inducing chorus cessation than simple calls. There is no main effect on whether the final call of the male is complete or is interrupted. We thus conclude that the sudden lack of signals—the ‘sounds of silence’—becomes an alarm cue that can explain the rapid cessation of choruses that are common in many chorusing species.     

Effect of morph types, body size and prior residence on food-site holding by males of the male-dimorphic stag beetle Prosopocoilus inclinatus (Coleoptera: Lucanidae)

Mate-securing tactics of small males in male-polymorphic species exhibiting male–male combat is an important issue in behavioral ecology. While most studies have focused on the outcomes of such combat encounters, the holding of a mating resource like a feeding site has a greater impact for obtaining reproductive success. We examined the effects of the prior residence at a feeding site on resource acquisition in the male-dimorphic stag beetle, Prosopocoilus inclinatus. More than 70 % of encounters did not result in combat. While larger males tended to occupy a food site after a combat, smaller males with prior residence tended to occupy food sites when no fighting occurred. Morph types or body size have no effect on the occurrence of combat, meaning that small males do not hesitate to fight with large males. These findings show that, under experimental conditions, the prior residence has a positive effect to hold food site in P. inclinatus.     

MATE CHOICE OCCURS ONLY IN SMALL CHORUSES OF PAINTED REED FROGS HYPEROLIUS MARMORATUS

ABSTRACT

In two-choice discrimination experiments, females of Hyperolius marmoratus preferred the calls of lower frequency of the pair of stimuli. This preference was not shown in mating patterns observed in natural choruses, but is when females are phonotactically orienting in small choruses in an experimental enclosure. With an increase in chorus size, the mating pattern shifts from size-based, non-random (with some evidence of size-assortative) mating to random mating. This is the first time that frequency-based mate-choice by female anurans has been associated with chorus size, and hence with the sonic complexity of the acoustic environment.     

Are Centrally Displaying Males Always the Centre of Female Attention? Acoustic Display Position and Female Choice in a Lek Mating Subterranean Insect

Several conceptual models seek to explain patterns of male display and factors that influence female mate choice in lek mating systems. The central advantage model predicts that males displaying at or near the lek centre should be more attractive to females than are males positioned along the lek periphery. Females may exhibit biases toward these centrally displaying males based on either spatial or display‐related cues. We tested the prediction of the central advantage model in investigating the importance of male display position in the subterranean and lek mating prairie mole cricket (Gryllotalpa major). Gryllotalpa major males form mating aggregations in the early spring and produce an acoustic advertisement signal from a constructed calling chamber at the soil surface. Pair formation occurs in the calling chamber, and males typically maintain these structures for the duration of the reproductive season. To assess whether G. major females exhibit a preference for males calling from centrally located acoustic burrows, we documented the spatial position and number of female attractions for all advertising males across the focal lek. Six spatial attributes related to display position were reduced using principal component analysis and examined for an association with male attractiveness. We found that in general, female attractions were distributed randomly across the lek; male attractiveness was not related to proximity to the lek centre nor to any factor associated with display position. The most highly attractive males, however, were located further from the lek centre and from nearest calling neighbours than other attractive males. Advertising males that segregate themselves within the aggregation and locate nearer the lek margin may gain a geometric advantage resulting in the increased probability of attracting a searching female.     

Mechanisms and evolution of inter-male spacing in the painted reedfrog (Hyperolius marmoratus)

Inter-male spacing in Hyperolius marmoratus choruses was studied at a natural breeding site. Calling males maintain minimum inter-individual distances of 50 cm. Agonistic behaviour and encounter calling appear to help maintain spacing. Males wrestle with one another by grappsling with their forelimbs and attempt to displace each other with powerful kicks from the hindlimbs. Acoustic playback experiments demonstrated that inter-male spacing was vocally mediated and that signal intensity provides cues regarding the proximity of near neighbours. When given a choice of three identical calls, differing only in their spatial separation, females displayed selective phonotaxis to the most widely spaced call. Such discrimination by females must generate strong selective pressure for males to maintain adquate spacing if they are to attract mates successfully.