Males In Poor Condition Research Articles

Condition-dependent differences in male vibratory pre-copulatory and copulatory courtship in a nuptial gift-giving spider

Condition-dependent secondary sexual traits and signals are often crucial for mate choice decisions. Nuptial gifts, provided by the male to the female during mating, may represent an indicator of male condition, especially if production of the gift is energetically costly. Additionally, other signalling modalities may well play a role in mate choice in such systems. Females of the nursery web spider Pisaura mirabilis preferably mate with males that provide a prey item wrapped in silk. Apart from the nuptial gift, vibrational signals employed during courtship and mating may reveal additional information about male condition. We tested condition-dependence of male vibrational signals of well-fed versus starved males, when in contact with female dragline silk and during mating trials. Our results show that vibrational signals are produced in P. mirabilis, both during pre-copulatory courtship and during copulation. Male courtship signals were condition-dependent: males in good condition initiated signalling earlier and emitted more vibrational pulses than poor-condition males. They were also more likely to be accepted by the female for copulation. We additionally identified vibrational signals during copulation. These signals were different from pre-copulatory courtship vibrations but did not differ between the treatment groups. This study shows that vibrational communication plays an important role before and during copulation in P. mirabilis. It sets the stage for further experiments on spider biotremology associated with nuptial gift giving behaviour.Significance statementMale courtship behaviour can indicate a male’s condition and quality and be subject to female mate choice. Vibrational communication during mating plays a crucial role in many animal species. Spiders are known to be extremely sensitive towards vibrations, and there is evidence that vibratory signals are also used during courtship. Here, we study the nuptial gift-giving spider Pisaura mirabilis in which courtship entails providing a nuptial gift by the male to the female. The gift quality determines on the probability and duration of mating. We investigated the role of vibrational behaviour in this species by standardizing nuptial gifts. Our study demonstrates that vibratory signals comprise information about the male’s condition, that signals are also produced during mating and that courtship and copulatory signals are strikingly different. We suggest that vibrational communication provides important condition-dependent traits for female mate choice in addition to the nuptial gift.

Male treefrogs in low condition resume signaling faster following simulated predator attack

Current models indicate that an organism’s sensitivity to risk may be heavily influenced by the trade-off between current and future reproduction. Individuals that have fewer future reproductive opportunities are expected to show more risky behavior as they have less to lose if captured by a predator (the asset protection principle). In this study, we examined the effects of age and physical condition on risk taking behavior during sexual signaling in the gray treefrog (Hyla versicolor) to test the prediction that older and poor condition males will take greater risks than their younger or higher-condition counterparts. In accordance with these predictions, we found that males in low physical condition resumed signaling activity more rapidly following a simulated predator attack than their higher-condition counterparts, although this effect was only apparent in one of two study years. Further, males that resumed calling early did not offset their risk of detection by predators via reduced calling effort. Contrary to our predictions, we did not find age to be a significant predictor of risk taking in male signaling behavior. We conclude with a discussion of possible explanations for the discrepancy observed between years and highlight the potential reproductive consequences of variation in risk taking behavior.

Forced copulation as a conditional alternative strategy in camel crickets

In the animal kingdom, males typically acquire reproductive access to females through courtship, nuptial gifts, or combat. In many species, small or poor-condition males that are unable to produce an attractive display, proffer an adequate mating gift, or dominate in male–male competition may resort to forced copulation. Forced copulation has been previously demonstrated in the camel cricket Pristoceuthophilus marmoratus and is uniquely facilitated by male hind leg weaponry that functions in both intrasexual competition and sexual coercion. Because male leg armaments are positively allometric, the largest males would seem best equipped to force-copulate, although they might be the most attractive to females, and so least likely to adopt a forced copulation strategy. In order to resolve this potential paradox and determine which males are in fact most likely to force-copulate, we manipulated male body size using diet and performed mating trials. Results showed that (1) male size increased with diet quality, (2) females appear to prefer larger males, and (3) smaller males were more likely to attempt forced copulation. Our results thus suggest that forced copulation is a condition-dependent alternative mating tactic used by small males unattractive to females.

Evolution of worthless gifts is favoured by male condition and prey access in spiders

Males from gift-giving species attempt to obtain food to offer to females. Therefore, food access may affect both their body condition and their reproductive success. In some species, males reduce the costs associated with giving gifts by reusing gifts, or by offering inedible items. Males from the spider Paratrechalea ornata (Trechaleidae) offer fresh prey or ‘genuine gifts’ to females, but also offer prey leftovers or ‘worthless gifts’. We examined gift weight and content, and their relation to male condition in the field. We also investigated how gift content, male condition and female reproductive status (virgin/mated) affect male mating success. In the field, most gifts were worthless; genuine gifts were heavier than worthless ones; and gift weights (both genuine and worthless gifts combined) were positively correlated with male condition. In the laboratory, males in good condition had higher mating success than males in poor condition. Males offering gifts (genuine or worthless) to virgin females enjoyed similar mating success and duration; neither differed significantly when compared to males without gift. In contrast, mated females behaved differently. Males without gifts were consistently rejected by mated females, while those that offered worthless gifts achieved matings. The interplay between male condition, prey access, female mating history and female preferences for gifts can favour the evolution of worthless gifts under certain conditions. Females do not penalize males with non-nutritive items by not mating or by reducing mating duration, but penalties may be potentially exerted via postcopulatory process.

Silk wrapping of nuptial gifts as visual signal for female attraction in a crepuscular spider

An extensive diversity of nuptial gifts is known in invertebrates, but prey wrapped in silk is a unique type of gift present in few insects and spiders. Females from spider species prefer males offering a gift accepting more and longer matings than when males offered no gift. Silk wrapping of the gift is not essential to obtain a mating, but appears to increase the chance of a mating evidencing a particularly intriguing function of this trait. Consequently, as other secondary sexual traits, silk wrapping may be an important trait under sexual selection, if it is used by females as a signal providing information on male quality. We aimed to understand whether the white color of wrapped gifts is used as visual signal during courtship in the spider Paratrechalea ornata. We studied if a patch of white paint on the males' chelicerae is attractive to females by exposing females to males: with their chelicerae painted white; without paint; and with the sternum painted white (paint control). Females contacted males with white chelicerae more often and those males obtained higher mating success than other males. Thereafter, we explored whether silk wrapping is a condition-dependent trait and drives female visual attraction. We exposed good and poor condition males, carrying a prey, to the female silk. Males in poor condition added less silk to the prey than males in good condition, indicating that gift wrapping is an indicator of male quality and may be used by females to acquire information of the potential mate.

Detection of predator cues alters mating tactics in male wolf spiders

Males of the wolf spider, Rabidosa punctulata, exhibit condition-dependent alternative mating tactics, whereby small, poor condition males engage in multimodal courtship while large, good condition males adopt a direct mount tactic that forgoes courtship. This study explores the possibility that tactic-specific costs can help explain this unintuitive pattern of mating tactic expression. Specifically, we hypothesize that courtship signaling is costly with respect to eavesdropping by predators and that males can alter their tactic expression based upon the perceived environmental predation risk. We test this by first examining the risk of predation associated with different mating tactics. We use a co-occurring predatory heterospecific, R. rabida as our predator. We found support for the prediction that courting R. punctulata males tended to be attacked more often than non-courting males, and the likelihood of being attacked was best predicted by courtship activity. Given this documented cost, we hypothesized that R. punctulata males would adjust their mating tactic based upon perceived predation risk. In a second experiment, we manipulated perceived predation risk by providing R. punctulata males with different female silk cues (conspecific; predatory heterospecific; conspecific + predatory heterospecific) and examined mating tactic expression. In support of our hypothesis, males were more likely to adopt the direct mount tactic in the presence of predatory heterospecific or mixed silk cues and were more likely to court in the presence of conspecific cues. These results support the hypothesis that the cost of predation from eavesdroppers may influence the evolution and expression of male alternative mating tactics in R. punctulata.

Does Female Personality Determine Mate Choice Through Sexual Cannibalism?

AbstractAnimal personalities (e.g. consistent across‐context behavioural differences between individuals) can lead to differences in mate choice. However, evidence for this link remains limited. Pre‐mating sexual cannibalism can be a behavioural syndrome (i.e. a suboptimal personality) in which adaptive female aggression towards heterospecific prey spills over on non‐adaptive aggression towards courting males, independently of the female mating or feeding status (i.e. the ‘aggressive spillover hypothesis’,ASH). On the other hand, sexual cannibalism can also be a form of mate choice by which females selectively kill or mate with males depending on the male phenotype. We introduce the hypothesis that the most aggressive females in the population will not only attack males more frequently, but will be less likely to impose sexual selection on males through sexual cannibalism. Assuming that in a field common garden experiment in which females were fedad libitumthe rate of weight gain by a female may reflect her voracity or aggressiveness, we show that in the cannibalistic burrowing wolf spiderLycosa hispanica(formerlyL. tarantula), voracity towards heterospecific prey predicts a female's tendency towards sexual cannibalism. Unmated females with higher weight gains were more cannibalistic and attacked males regardless of the male phenotype. On the other hand, females that were less voracious tended to be less cannibalistic, and when they did kill a male, they were selective, killing males in poorer condition and mating with those in better condition. Our results demonstrate that females with different phenotypes (growth rates) differently imposed selection on male condition, tentatively supporting the hypothesis that female aggression levels can spill over on sexual selection through sexual cannibalism.

Within population variation in testis size in the mole-shrew (Anourosorex squamipes) (Mammalia: Soricidae)

Sperm competition is recognized as a key event occurring during postcopulatory sexual selection. The evolutionarily stable strategy (ESS) predicts that males in poor condition should invest more heavily in sperm compared with males in good condition. We explored the effects of body condition and season on testes mass in the mole-shrew (Anourosorex squamipes). We used the “scaled mass index” as body condition to analyze the effects of season, body condition and body length on testis size. The results showed that testes mass was greatest in summer. Head body-length also significantly affected testis size in the four seasons. In addition, males in good conditions had relatively heavier testes than those in poor conditions in spring, summer and autumn, but not in winter, suggesting that the finding contradicts the prediction of the evolutionarily stable strategy.

Measuring the costs of alternative reproductive tactics in horseshoe crabs, Limulus polyphemus

Trade-offs are inherent to alternative reproductive tactics (ARTs), and identifying the costs and benefits of tactics is essential to understanding their evolution and maintenance within a population. Male horseshoe crabs exhibit two condition-dependent ARTs: males that are in better condition arrive on spawning beaches attached to a female, while males in poorer condition join spawning pairs as satellites and engage in sperm competition. Previous research has identified several benefits to the attached tactic, but the costs are less well understood. We examined a previously uninvestigated potential cost to the attached male tactic: nutritional stress caused by a restricted ability to feed. We found that field-caught attached males produced 57% less faeces in a 12 h period than satellite males, and had 2.5 times emptier digestive tracts than satellite males. We further examined this cost using stable isotopes because nutritionally stressed animals are predicted to have higher δ15N levels. We found that field-caught attached males had higher δ15N values than satellite males. However, higher δ15N values could result from nutritional stress or from feeding on higher trophic levels. We tested this experimentally and found that starved animals had higher post-treatment δ15N values compared to animals that were fed. Furthermore, the digestive tracts of field-caught attached males contained three times more sea grass (lower tropic levels have lower δ15N values) than satellite males. These findings mean that the higher δ15N values of field-caught attached males likely result from fasting rather than differences in diet. Taken together, our results indicate that a period of nutritional stress caused by reduced food consumption is a novel cost of the attached tactic. This study provides a key piece of information to explain why ARTs in horseshoe crabs take the form they do and provides a novel method for studying costs associated with ARTs in other species.

How Reliable Is Song Learning Accuracy as a Signal of Male Early Condition?

That many species of songbirds learn their songs imitatively is well established, but it is less clear why they do so. A component of the developmental-stress hypothesis posits that young males in good condition learn songs more accurately than males in poor condition and that females use learning accuracy as an honest signal of male developmental history. An unresolved problem is how females reliably assess learning accuracy when they are not certain of the identity of the male's tutor and thus the specific model from which a song was copied. We therefore investigated whether song learning accuracy assessment (SLAA) can be reliable, using evolutionary simulation models of song learning. We found that SLAA is indeed less reliable than assessment in which male signals are compared to an unlearned standard, as a result of three types of errors in matching songs to their models. In the simplest models, SLAA was particularly unreliable, but when the model is made more realistic by including features such as geographically constrained learning, repertoire complexity, and, in particular, song categorization, the reliability of SLAA increased. Our results demonstrate a range of conditions under which the assessment of song learning accuracy might be reasonably reliable and therefore likely to evolve.

Female spiders ignore condition-dependent information from nuptial gift wrapping when choosing mates

In many species, condition-dependent secondary sexual traits are important for female choice. In the spider Pisaura mirabilis, males offer females a nuptial gift (prey wrapped in silk) during courtship. Gift construction may involve high costs for males, and those in low condition invest less time and silk in wrapping the prey. We investigated how male condition and gift wrapping affect male reproductive success and whether females use the wrapped gift as an honest indicator of male condition. We experimentally manipulated male condition (satiated and starved males) and gift wrapping (well- and poorly wrapped gifts) and carried out experiments in a fully factorial design. We found that males in good condition were more successful in obtaining matings and obtained longer copulations than males in poor condition. In contrast, gift wrapping did not affect female mate choice. Only good-condition males obtained offspring. Gift wrapping is an honest indicator of male condition, but in spite of this females did not use this information in mate choice. We argue that because gift wrapping mainly functions to promote male interests, good-condition males would also be better at cheating the female, for example using wrapping to hide a worthless gift. Females should therefore evolve to ignore the wrapping information and instead base their mate choice decision on male traits that unequivocally benefit their own reproductive success. Our results are consistent with this prediction, as females discriminated males based only on their actual feeding condition, and this choice provided them with direct reproductive benefits.

When Less Is Best: Female Brown-Headed Cowbirds Prefer Less Intense Male Displays

Sexual selection theory predicts that females should prefer males with the most intense courtship displays. However, wing-spread song displays that male brown-headed cowbirds (Molothrus ater) direct at females are generally less intense than versions of this display that are directed at other males. Because male-directed displays are used in aggressive signaling, we hypothesized that females should prefer lower intensity performances of this display. To test this hypothesis, we played audiovisual recordings showing the same males performing both high intensity male-directed and low intensity female-directed displays to females (N = 8) and recorded the females' copulation solicitation display (CSD) responses. All eight females responded strongly to both categories of playbacks but were more sexually stimulated by the low intensity female-directed displays. Because each pair of high and low intensity playback videos had the exact same audio track, the divergent responses of females must have been based on differences in the visual content of the displays shown in the videos. Preferences female cowbirds show in acoustic CSD studies are correlated with mate choice in field and captivity studies and this is also likely to be true for preferences elucidated by playback of audiovisual displays. Female preferences for low intensity female-directed displays may explain why male cowbirds rarely use high intensity displays when signaling to females. Repetitive high intensity displays may demonstrate a male's current condition and explain why these displays are used in male-male interactions which can escalate into physical fights in which males in poorer condition could be injured or killed. This is the first study in songbirds to use audiovisual playbacks to assess how female sexual behavior varies in response to variation in a male visual display.

Relationship Between Condition, Aggression, Signaling, Courtship, and Egg Laying in the Field Cricket, Gryllus assimilis

AbstractSexual selection theory suggests males in good condition should be more successful than males in poor condition when competing with rivals for territories and mates. Understanding how condition influences the interplay between aggression, mate attraction, and courtship displays could help explain why variation is maintained in traits that confer fitness. Using laboratory‐reared Jamaican field crickets, Gryllus assimilis, we found that fine‐scale temporal components of mate attraction signals were positively correlated with body condition (residual body mass) and body size; signaling effort was positively correlated with both body condition and fine‐scale temporal signaling components; aggression was positively correlated with signaling effort; number of eggs laid was positively correlated with female body size, male body condition and aggression. Together our correlative study suggests that variation in body condition and size may drive some of the variation in cricket mate attraction signaling and aggression. Given condition and body size are influenced by foraging ability, nutrient availability and the organism’s ability to uptake and retain these essential nutrients could explain some of the persistent variation in fitness conferring traits.

Reflectance characteristics are correlated with male condition in a population of threespine stickleback (Gasterosteus aculeatus) that has lost the species typical nuptial signal

Several populations of threespine stickleback (Gasterosteus aculeatus) on the Pacific Coast of North America remain drab during courtship and become melanic during parental care rather than adopt the species typical red signal. Male signal redness is an honest signal of male physiological condition. Here, I test the prediction that reflectance characteristics of drab males also honestly indicate male condition. I located, observed and captured nesting stickleback from Brannen Lake, British Columbia, Canada. I measured reflectance characteristics of each male’s signal right after capture and later measured its wet weight and total length to calculate Fulton’s condition index, K. Males in better condition, higher K, had lower total reflectance (i.e. were darker) than males in poorer condition. The principals underlying honest signaling appear to be operating despite the possession of a novel nuptial signal in Brannen Lake stickleback.

Reversed parasite-mediated selection in sticklebacks from eutrophied habitats

Sexual selection is often assumed to increase the viability of populations by increasing the quality of offspring produced. Presently, human-induced environmental changes are altering the process of sexual selection by influencing male–male interactions and female mate choice. Here, we show that increased density of filamentous algae due to eutrophication reverses parasite-mediated selection during reproduction in threespine sticklebacks (Gasterosteus aculeatus). When we manipulated the density of artificial algae in a breeding area in the Baltic Sea, more males nested in dense than in sparse vegetation, but the males in dense vegetation were more parasitized. Interestingly, heavily parasitized males acquired more eggs than less parasitized males in dense vegetation but not in sparse vegetation. The higher probability of reproduction for parasitized males in dense algae growth could be due to impaired visibility relaxing male–male competition or reducing female choosiness. This could favour males in poor condition that often invest more in attracting females than males in good condition. In sparse vegetation, parasitized males may have a lower reproductive success due to intense male–male competition, careful female choice and high predation rate selecting against parasitized males. The results suggest that eutrophication could alter the fraction of the population that reproduces, which could have long-term evolutionary consequences.

Exposure to Persistent Organic Pollutants and First-Year Survival Probability in Gray Seal Pups

Many studies have demonstrated that persistent organic pollutants are transferred from mother to pup during lactation in phocid seals, but none have been able to determine the significance of these findings for survivorship. The aim of this study was to investigate the relationship between blubber contaminant concentrations and first-year survival in gray seal pups. A mark-recapture framework was used to estimate survival probabilities and animals were "marked" using novel mobile phone tags. Individual and group covariates (sex, condition, and blubber contaminants) were embedded within a live-resighting model. The most significant covariates remained condition at weaning and sex (males in poor condition had the lowest survival probability), as was found previously, but there was also evidence indicating that higher blubber contaminants additionally decreased survivorship. The models' Akaike's Information Criteria (AICs) and their associated weights, point toward the tetrapolybrominated diphenyl ether congeners (dominated by BDE-47) as being the most important group of contaminants affecting survival probability, followed by the total dichlorodiphenyltrichloroethanes (DDTs) and pentapolychlorinated biphenyl congeners. These compounds were not the most abundant in the blubber, suggesting further studies into their toxicological effects in this species are necessary. The specific mechanisms driving the reduction in survivorship remain unknown.

Should I stay or should I go? Condition- and status-dependent courtship decisions in the scorpionfly Panorpa cognata

The occurrence of prolonged courtship behaviour in many animal species is a well-known phenomenon. The duration of courtship may be influenced by both females and males, often with different interests. In the scorpionfly Panorpa cognata, males offer a salivary secretion as a nuptial gift before copulation. However, males do not immediately initiate copulation by the production of the salivary mass. Instead pairs usually engage in prolonged courtship interactions. Yet the duration of courtship is highly variable, ranging between a few minutes and several hours. Furthermore, courtship does not always result in copulation; instead females often terminate courtship and abandon the male. The duration and outcome of courtship are likely to be influenced by factors such as body condition and female mating history, because they might influence individual attractiveness and motivation to mate. I examined to what extent these factors influence both male and female courtship decisions. Mated females were less keen to remain in courtship for long and abandoned males sooner than virgin females. Yet, male mating behaviour was unaffected by female mating status. Counterintuitively, females in poor condition interrupted courtship sooner with increasing body weight of their male partner. In addition, heavier males initiated copulations sooner than males in poorer condition. However, this effect was evident only in interactions with females in poor condition. A possible interpretation of these results is that males attempt to prevent females in poor condition from leaving prior to copulation by initiating copulation faster.

Should you eat your offspring before someone else does? Effect of an egg predator on filial cannibalism in the sand goby

Costs and benefits of parental care are expected to affect filial cannibalism. One factor that increases the costs and decreases the benefits of care is the presence of egg predators. In general, the effect of egg predators on filial cannibalism is unknown. Here, we examine the effect of an egg predator on filial cannibalism in the sand goby. Males caring for eggs were exposed to three treatments: no egg predator, visual cues from an egg predator, and chemical and visual cues from an egg predator. We hypothesized that the perceived benefits of providing care in the presence of an egg predator would be relatively low, and we expected filial cannibalism to increase in the presence of the egg predator, especially when both chemical and visual predator cues were present, as this might represent a greater threat. When both visual and chemical predator cues were present, whole-clutch cannibalism increased. In addition, larger males and males in poorer condition showed less whole-clutch cannibalism than smaller males or males in better condition. There was no effect of egg predator on partial-clutch cannibalism. However, males that engaged in partial-clutch cannibalism ate more of their eggs when the eggs were spawned by a female in relatively good condition, but a smaller proportion and number of eggs when only a single female spawned. In general, our findings suggest that male sand gobies are sensitive to the costs and benefits of care and are more likely to terminate care when the expected benefits are relatively low.

Public Versus Personal Information for Mate Copying in an Invertebrate

Organisms require information to make decisions about fitness-affecting resources, such as mates. Animals may extract "personal information" about potential mates by observing their physical characteristics or extract additional "public information" by observing their mating performance [1]. Mate copying by females [2-6] is a form of public information use that may reduce uncertainty about male quality, allowing more adaptive choices [2]. Experimental studies have produced evidence that female mate copying occurs in several species of fish [3], birds [5-7], and mammals [8], including humans [9]. We report the first evidence that a female invertebrate can exploit public information to select mates. In a first experiment, Drosophila melanogaster female prospectors increased their time in the attraction zones of poor-condition males, but not of good-condition males, after having observed them with a model female. This suggests that females appraised prospective mates by exploiting public information and did so mainly when it contrasted with personal information. In a second experiment, prospector females preferably mated with males of the color type they had previously observed copulating over males of the rejected color type, suggesting that female Drosophila can generalize socially learned information. The complexity of Drosophila decision-making suggests an unprecedented level of cognition in invertebrates. Our findings have implications for evolution given that socially learned mate preferences may lead to reproductive isolation, setting the stage for speciation [10].

Does Competition Allow Male Mate Choosiness in Threespine Sticklebacks?

The theory of mate choice posits that intensified competition for mates can generate variation in either the strength or the direction of mate preferences within the competing sex. Here, we show that intensified male competition, manipulated through the operational sex ratio, induced differential mate choosiness among threespine stickleback males Gasterosteus aculeatus. In the absence of male competition, males were choosy independent of their condition when presented sequentially with a large and a small female. However, in a male-biased social setting, males in poor condition became indiscriminate, whereas good-condition males continued to be selective. Hence, competition induced condition-dependent mate choosiness. This was probably due to mating opportunities decreasing more for poor-condition than for good-condition males when competition intensified, resulting in condition-dependent cost of choice. Variation in condition and cost of choice could thus allow the persistence of male mate choosiness in populations experiencing intense male competition.