Sensory Trap Research Articles

Sensory trap leads to reliable communication without a shift in nonsexual responses to the model cue.

The sensory trap model of signal evolution suggests that males manipulate females into mating using traits that mimic cues used in a nonsexual context. Despite much empirical support for sensory traps, little is known about how females evolve in response to these deceptive signals. Female sea lamprey (Petromyzon marinus) evolved to discriminate a male sex pheromone from the larval odor it mimics and orient only toward males during mate search. Larvae and males release the attractant 3-keto petromyzonol sulfate (3kPZS), but spawning females avoid larval odor using the pheromone antagonist, petromyzonol sulfate (PZS), which larvae but not males, release at higher rates than 3kPZS. We tested the hypothesis that migratory females also discriminate between larval odor and the male pheromone and orient only to larval odor during anadromous migration, when they navigate within spawning streams using larval odor before they begin mate search. In-stream behavioral assays revealed that, unlike spawning females, migratory females do not discriminate between mixtures of 3kPZS and PZS applied at ratios typical of larval versus male odorants. Our results indicate females discriminate between the sexual and nonsexual sources of 3kPZS during but not outside of mating and show sensory traps can lead to reliable sexual communication without females shifting their responses in the original context.

Male Barn Swallows Tolerate Nestling-Like Courtship Calls of Rival Males

Animals often exhibit conspicuous, and sometimes curious, courtship traits, such as nestling-like courtship display in birds, though modern studies of nestling-like courtship display (and calls) are virtually lacking. An exception is previous experiments on the barn swallowHirundo rustica, demonstrating that females are equally attracted to playback of two structurally similar calls, nestling-like male courtship calls and nestling food-begging calls. The experiments support the sensory trap hypothesis, i.e., that male signals mimic nestling stimuli to exploit female parental care for nestlings. However, female attraction might not be the sole function of nestling-like traits, and males might also have a sensory bias toward nestling-like traits, in which males would be less aggressive toward characteristics typical of immature individuals. Here, I conducted playback experiments to study the function of nestling-like male courtship calls in the context of male–male interactions. Playback of male courtship songs induced frequent approaches by neighbouring males, while nestling-like male courtship calls or nestling food-begging calls induced fewer approaches, though male responses to the latter two vocalisations increased when approaching the nestling period. The observed pattern indicates that, by mimicking immature individuals, males attract intended signal receivers (i.e., females) while avoiding interference from eavesdroppers (i.e., neighbouring males). This unique function can explain why species with parental care exhibit immature-like behaviour.

Seabird bycatch risk correlates with body size, and relatively larger skulls, bills, wings and sensory structures

Many animals have sensory biases towards signals or cues that typically provide some fitness benefit. Sensory traps occur when other species or anthropogenic sources produce similar signals or cues but responding is no longer adaptive and can impose significant costs or even death. Bycatch of seabirds by fishing boats has devastating impacts, causing hundreds of thousands of seabird deaths per annum. Here, we explore whether fishing vessels are acting as a sensory trap, inadvertently targeting seabirds with certain life-history traits or larger skeletal or sensory structures. We surveyed the literature to compare seabird order, diet, wingspan, body size, and nesting preference (surface or burrow) of 70 seabirds with varying numbers of reported bycatch in one of the world’s most important regions for seabird breeding, in northern Aotearoa New Zealand. We also examined the skeletal and sensory measurements of six seabirds that co-occur spatially in this region, but have different numbers of reported bycatch and indices of bycatch risk. The literature survey revealed that the Charadriiformes and the Sphenisciformes were the most vulnerable groups (p = 0.01), especially to surface longline fisheries. There were no correlations with diet and foraging behaviour, but surface nesting seabirds and those with larger bodies and wingspans were at a greater risk of becoming bycatch. Skeletal measurements show that species with higher bycatch also have relatively larger skulls, bills and wings, eye sockets and nostrils (relative to body size) (p < 0.05). This suggests that having a larger overall body size and longer protruding body parts is a primary risk factor, but that species with relatively more sensitive sensory systems likely have even more acute bycatch risk. Considering fishing vessels as sensory traps provides a context to explore the multiple interconnecting factors of sensory sensitivity, sensory bias, behaviour and morphology.

Nestling, but not adult male, barn swallows emit short calls in noisy environments

Abstract Some, but not all, animals cope with anthropogenic noise by changing the structure of their acoustic signals, possibly due to two interrelated factors: the design of the acoustic signals and the intrinsic biological state. Here, using the barn swallow (Hirundo rustica) that breed solitarily along streets, we studied male enticement calls and nestling food-begging calls in relation to ambient noise. The former calls are structurally quite similar to the latter, perhaps functioning as a sensory trap to exploit female parental care for nestlings. This provides a unique opportunity to study whether intrinsic biological state (i.e. developmental stage, here), virtually independent of acoustic design, matters in acoustic adaptation to anthropogenic noise. We found that the syllable length of nestling food-begging calls, but not of male enticement calls, decreased with increasing local noise levels within populations. The syllable lengths of the father’s enticement calls and those of the nestling’s food-begging calls were positively related, which explains why male enticement calls as well as nestling food-begging calls had shorter syllables in a noisy urban population compared to those in a quiet rural population. The current findings indicate that the intrinsic biological state of two acoustically similar sounds explains their differential relationships with ambient noise.

Male lyrebirds create a complex acoustic illusion of a mobbing flock during courtship and copulation

Darwin argued that females' "taste for the beautiful" drives the evolution of male extravagance,1 but sexual selection theory also predicts that extravagant ornaments can arise from sexual conflict and deception.2,3 The sensory trap hypothesis posits that elaborate sexual signals can evolve via antagonistic coevolution whereby one sex uses deceptive mimicry to manipulate the opposite sex into mating.3 Here, the success of deceptive mimicry depends on whether it matches the receiver's percept of the model,4 and so has little in common with concepts of aesthetic judgement and 'beauty.'1,5-9 We report that during their song and dance displays,10 male superb lyrebirds (Menura novaehollandiae) create an elaborate acoustic illusion of a mixed-species mobbing flock. Acoustic analysis showed that males mimicked the mobbing alarm calls of multiple species calling together, enhancing the illusion by also vocally imitating the wingbeats of small birds. A playback experiment confirmed that this illusion was sufficient to fool avian receivers. Furthermore, males produced this mimicry only (1) when females attempted to exit male display arenas, and (2) during the lyrebirds' unusually long copulation, suggesting that the mimicry aims to prevent females from prematurely terminating these crucial sexual interactions. Such deceptive behavior by males should select for perceptual acuity in females, prompting an inter-sexual co-evolutionary arms race between male mimetic accuracy and discrimination by females. In this way the elaboration of the complex avian vocalizations we call 'song' could be driven by sexual conflict, rather than a female's preference for male extravagance.

Context-dependent consequences of color biases in a social fish

Abstract Colorful visual signals can provide receivers with valuable information about food, danger, and the quality of social partners. However, the value of the information that color provides varies depending on the situation, and color may even act as a sensory trap where signals that evolved under one context are exploited in another. Despite some elegant early work on color as a sensory trap, few empirical studies have examined how color biases may vary depending on context and under which situations biases can be overridden. Here, using Neolamprologus pulcher, a highly social cichlid fish from Lake Tanganyika, we conducted a series of experiments to determine color biases and investigate the effects of these biases under different contexts. We found that N. pulcher interacted the most with yellow items and the least with blue items. These biases were maintained during a foraging-based associative learning assay, with fish trained using yellow stimuli performing better than those trained using blue stimuli. However, these differences in learning performance did not extend to reversal learning; fish were equally capable of forming new associations regardless of the color they were initially trained on. Finally, in a social choice assay, N. pulcher did not display a stronger preference for conspecifics whose yellow facial markings had been artificially enhanced. Together, these findings suggest that the influence of color biases varies under different contexts and supports the situational dependency of color functions.

A pheromone antagonist liberates female sea lamprey from a sensory trap to enable reliable communication

The evolution of male signals and female preferences remains a central question in the study of animal communication. The sensory trap model suggests males evolve signals that mimic cues used in nonsexual contexts and thus manipulate female behavior to generate mating opportunities. Much evidence supports the sensory trap model, but how females glean reliable information from both mimetic signals and their model cues remains unknown. We discovered a mechanism whereby a manipulative male signal guides reliable communication in sea lamprey (Petromyzon marinus). Migratory sea lamprey follow a larval cue into spawning streams; once sexually mature, males release a pheromone that mimics the larval cue and attracts females. Females conceivably benefit from the mimetic pheromone during mate search but must discriminate against the model cue to avoid orienting toward larvae in nearby nursery habitats. We tested the hypothesis that spawning females respond to petromyzonol sulfate (PZS) as a behavioral antagonist to avoid attraction to the larval cue while tracking the male pheromone despite each containing attractive 3-keto petromyzonol sulfate (3kPZS). We found 1) PZS inhibited electrophysiological responses to 3kPZS and abated preferences for 3kPZS when mixed at the same or greater concentrations, 2) larvae released more PZS than 3kPZS whereas males released more 3kPZS than PZS, and 3) mixtures of 3kPZS and PZS applied at ratios measured in larval and male odorants resulted in the discrimination observed between the natural odors. Our study elucidates how communication systems that arise via deception can facilitate reliable communication.

Males sacrifice their legs to pacify aggressive females in a sexually cannibalistic spider

Monogynous male mating strategies have repeatedly evolved in spiders along with female-biased sexual size dimorphism (SSD) and extreme male mating investment. As a manifestation of sexual conflict, male African golden-silk spiders, Trichonephila fenestrata, are regularly attacked by females during copulation, and sexual cannibalism is common. Curiously, attacked males actively cast off (autotomize) their front legs and copulation continues while the female is feeding on these legs. Since the loss of legs is costly in reducing males’ ability to mate guard, it should yield significant benefits. In a series of experiments, we investigated the behavioural mechanism of male leg ejection and tested three hypotheses. First, we performed feeding experiments to test whether conspecific male legs are particularly attractive for females and act as a sensory trap. Second, we conducted mating experiments with sibling and nonsibling pairings to test whether males preferentially invest in high-quality mates. Third, by offering male legs during copulations, we tested whether male leg ejection serves to distract and pacify females. In support of the female pacifier hypothesis, our results confirm a significantly reduced probability of attacks in females that had been offered a male leg, but we found no relationship between simulated leg ejection and male survival. While there was no evidence for special properties of male legs, females accepted male legs significantly more often than insect food. The degree of male leg sacrifice did not depend on male–female relatedness, but large males lost more legs than small males, and small males achieved more copulations. However, total copulation duration was unrelated to male size. Male leg sacrifice in T. fenestrata may represent a rare example of an evolutionary transition in which the antipredation behaviour of autotomizing body parts has changed its function into a sexual context, here to pacify females and to facilitate undisturbed copulations.

Investigating the role of a mud structure in a fiddler crab: do semidomes have a reproductive function?

Sensory traps occur when a signal evolves to mimic a cue to which the receiver responds favorably in another context. For example, if females are attracted to the noise a prey item makes, then a conspecific male can mimic that noise, thereby attracting females in the context of mating. Thus, sensory traps can be beneficial to receivers since attraction helps locating males more efficiently. But what happens when receivers are less attracted by the sensory trap outside of the original context (due to the cost of the response for instance)? Does this weaken and eventually “break” the sensory trap? Here, we show that a rare, small mud structure (a semidome) built by some male fiddler crabs (Austruca mjoebergi) at their burrow entrances are most likely relics of the sensory traps used by other fiddler crabs (the larger, far more abundant hoods of Leptuca species). Females of A. mjoebergi have retained their tendency to move towards vertical structures for protection when threatened by a predator—the original context thought to be important in the evolution of sensory traps in other fiddler crab species. However, females show no significant preference for males with semidomes. Additionally, males do not use the semidomes as landmarks to relocate their burrows when courting. The results suggest that in A. mjoebergi, semidomes do not function as sensory traps, despite the existence of a pre-existing bias in females. We suggest that semidomes have lost their attractiveness in the mating context due to ecological features, such as predation and environmental heterogeneity. There is growing evidence of sensory traps in many animal species, with an ever-widening range of contexts from nuptial gift giving in spiders to egg recognition in non-brood-parasitized birds. While we are starting to understand the significance of sensory traps, little thought has been given to what happens when they break down. If there is a change in the original context that favored the receiver’s response, then there is likely to be a subsequent change in the receiver’s bias and finally, in the sensory trap. If the mimic of the original stimulus does not induce a beneficial response in the receiver anymore, the sensory trap would become inefficient and stop being selected. The effect will be most profound when the sensory trap was costly to set up, since there will be selection against its retention. Here, we show that a sensory trap can become a relic when ecological conditions change and make it not functional anymore. To our knowledge, it is the first study providing such empirical evidence.

Imperfect nestling-mimicry attracts high-quality females in the Asian barn swallow

The sensory trap hypothesis predicts that male signals mimic stimuli to which females respond in other contexts, yet these signals may not elicit equivalent responses from all females. Female barn swallows Hirundo rustica are attracted to male enticement calls, particularly high-pitched ones that resemble the food-begging calls of nestlings to a greater extent. However, male enticement calls are still distinguishable from nestling food-begging calls, denoting “imperfect mimicry”. It remains unknown why perfect mimicry is prevented given that nestling-like calls effectively attract females. Here, using Asian subspecies (H. r. gutturalis), we examined female preference for male enticement calls to nestling food-begging calls during the mating period in relation to the ornamentation of her previous mate and trial date, a proxy of female arrival date, in this experiment with the expectation that females vary their response depending on these variables. We found that female reaction to the playback of male enticement calls, relative to the playback of nestling food-begging calls, increased with increasing plumage coloration of her previous mate, and decreased with increasing trial date (and hence late arrival). This observation is predictable, because colorful males emit lower-pitched, i.e. less nestling-like, enticement calls, and because early-arriving females, which are more experienced females, would have higher discriminability than others. Imperfect mimicry to nestling food-begging calls would attract relatively high-quality females, and thus males should not emit enticement calls that closely resemble nestling food-begging calls except when high-quality females are not available.

Not all crabs are created equal: diverse evolutionary paths of female preferences for courtship structures in fiddler crabs (genus Uca)

ᅟMales of fiddler crabs (genus: Uca) construct courtship structures using mud or sand to attract mate-searching females for underground mating. A sensory trap hypothesis proposes that the courtship structures have evolved by trapping the sensory bias for any objects which the crab approach to evade predators. We tested if the sensory bias commonly exists in three species of fiddler crabs and the outgroup Ocypode stimpsoni, by placing crabs individually at the center of an arena, from which they could choose between burrows with and without structures. Contrary to previous results in other species, male U. lactea showed no orientation response toward holes with or without semidomes. Female U. lactea predominantly visited holes with semidomes during reproductive periods but did not show the response during non-reproductive periods. In contrast, female U. arcuata and male U. terpsichores and even the outgroup female O. stimpsoni showed a strong orientation response to an artificial structure. By inferring the evolutionary history of sensory biases and courtship structures, we conclude that the preference for the courtship structures evolved before the genus Uca branched out from the common ancestor of genus Uca and Ocypode and yet that the sensory bias has been modified or lost in U. lactea. We tested the sensory trap hypothesis for preference for courtship structures in three species of fiddler crabs in different locations and the outgroup O. stimpsoni. Contrary to previous results in other species, one species which build courtship structures (U. lactea) showed sex- and context-dependent orientation responses in the non-courtship context. On the other hand, the other species tested had a strong orientation response to structures. This is the first comparative study supporting that the preference for the courtship structures in fiddler crabs could have different evolutionary paths.

Sand ornaments used to attract females are avoided by rival males in the fiddler crab Uca lactea

Males of several fiddler crab species sometimes construct sand structures at the entrances to their burrows to which they attract females for mating. Sand structures are thought to exploit fiddler crabs’ risk-reducing behaviour by enticing them into the burrows, so males as well as females are expected to be attracted by the structures. Males with structures may thus incur greater costs to repel intruding males than males without structures, and only males that can afford such costs are likely to build structures. Given that the sand structures are constructed only by males that have sufficient ability to fend off intruders, other crabs may regard the structures as an indicator of those males’ potential fighting ability. In the present study, I showed that burrowless males of Uca lactea were averse to burrows with structures when there were no predators nearby, but that burrowless females showed no such tendency. Sand structures in fiddler crabs may have originated as a sensory trap to attract females, but other males may use the structure as an indicator of the resident male’s fighting ability. However, the sand structures did not appear to function as a signal to attract females.

Prey Luring Coloration of A Nocturnal Semi‐Aquatic Predator

AbstractBody coloration serves a variety of purposes in animals. Diurnal and nocturnal predators such as spiders may use their body coloration to lure prey. We predicted here that the white patches on the forelegs on females of the nocturnal semi‐aquatic spider Dolomedes raptor lure prey, explaining why they are primarily displayed when the spider forages along the water edge. To test our prediction, we developed a color vision model assessing whether the patches are visible to pygmy grasshoppers, the spider's primary prey. We conducted a field experiment using cardboard dummies that resemble D. raptor in size, shape, and color, but with half of them lacking leg patches, and we staged interactions between pygmy grasshoppers and D. raptor with and without leg patches in a greenhouse. We found the white patches to be visible to grasshoppers. The dummies with white patches attracted more grasshopper prey than the dummies without the patches. Moreover, grasshoppers were more attracted to spiders when their white patches were present. Our results supported the hypothesis that the white patches of D. raptor lure prey. Our findings, nevertheless, could not be explained as the spider's body coloration acting as a sensory trap but it should not be ruled out. More studies on a wider range of predators and prey will give more meaningful insights into the co‐evolution of predatory lures and prey sensory modalities.

Female sea lamprey shift orientation toward a conspecific chemical cue to escape a sensory trap

The sensory trap model of signal evolution hypothesizes that signalers adapt to exploit a cue used by the receiver in another context. Although exploitation of receiver biases can result in conflict between the sexes, deceptive signaling systems that are mutually beneficial drive the evolution of stable communication systems. However, female responses in the nonsexual and sexual contexts may become uncoupled if costs are associated with exhibiting a similar response to a trait in both contexts. Male sea lamprey (Petromyzon marinus) signal with a mating pheromone, 3-keto petromyzonol sulfate (3kPZS), which may be a match to a juvenile cue used by females during migration. Upstream movement of migratory lampreys is partially guided by 3kPZS, but females only move toward 3kPZS with proximal accuracy during spawning. Here, we use in-stream behavioral assays paired with gonad histology to document the transition of female preference for juvenile- and male-released 3kPZS that coincides with the functional shift of 3kPZS as a migratory cue to a mating pheromone. Females became increasingly biased toward the source of synthesized 3kPZS as their maturation progressed into the reproductive phase, at which point, a preference for juvenile odor (also containing 3kPZS naturally) ceased to exist. Uncoupling of female responses during migration and spawning makes the 3kPZS communication system a reliable means of synchronizing mate search. The present study offers a rare example of a transition in female responses to a chemical cue between nonsexual and sexual contexts, provides insights into the origins of stable communication signaling systems.

Modeling the decline and potential recovery of a native butterfly following serial invasions by exotic species

Population sizes and range of the native butterfly Pieris oleracea declined after habitat loss and parasitism by an exotic braconid wasp (Cotesia glomerata) introduced to control the exotic invasive butterfly Pieris rapae. Further declines are attributed to the invasive exotic weed garlic mustard (Alliaria petiolata), an oviposition sensory trap on which P. oleracea larval survival and growth are very poor. But a population of P. oleracea has adapted to garlic mustard over the past several decades, coincident with the introduction of a second parasitoid, C. rubecula, a specialist on P. rapae that is competitively dominant to C. glomerata. We used stochastic simulation models to assess the plausibility of a hypothesis that reduced parasitoid pressure over this time period enabled P. oleracea to adapt to A. petiolata. We simulated scenarios of trait proliferation via spontaneous mutation or immigration of the trait, and residual variation in the trait following the butterfly’s isolation in North America. Results indicate that the most likely scenario for the population that has adapted to garlic mustard includes (1) a change in selection following garlic mustard invasion to favor previously neutral residual variation in the population, (2) release from parasitism, and (3) evolution of improved larval survival on garlic mustard, which allowed an increased host range, and potentially, population size.

Male nestling-like courtship calls attract female barn swallows, Hirundo rustica gutturalis

Courtship behaviours of males often resemble the food-begging behaviour of their young, at least from a human perspective. Although it is argued that this represents a sensory trap, it is still unclear whether such behaviour in males is objectively similar to nestling behaviour and can elicit female parental care (e.g. attraction to nestlings) in courtship, as predicted by the sensory trap hypothesis. In this study, we demonstrated that the enticement calls of male barn swallows structurally resemble the food-begging calls of nestlings, compared with the other three male vocalizations (i.e. songs, alarm calls and contact calls). In addition, we used experimental playback of the vocalizations to compare the response of females towards male enticement calls and nestling food-begging calls during the courtship period. We found that females were attracted to the playback of nestlings' food-begging calls during the courtship period, despite nestlings being absent at this time. The response of females to food-begging calls was similar and positively correlated with their response to male enticement calls. These observations support the sensory trap hypothesis, i.e. that male signals mimic stimuli to which females respond for parental care.

Foraging costs drive female resistance to a sensory trap

Male ornaments can evolve through the exploitation of female perceptual biases such as those involved in responding to cues from food. This type of sensory exploitation may lead to confusion between the male signals and the cues that females use to find/recognize food. Such interference would be costly to females and may be one reason why females evolve resistance to the male ornaments. Using a group of species of viviparous fish where resistance to a sensory trap has evolved, we demonstrate that females exposed to an ornament that resembles food have a diminished foraging efficiency, that this effect is apparent when foraging on a food item with which the ornament shares visual attributes, and that not all species are equally affected by such confusion. Our results lend support to the model of ornamental evolution through chase-away sexual conflict.

Mating stimulates female feeding: testing the implications for the evolution of nuptial gifts

Nutritional benefits from nuptial gifts have been difficult to detect in some species, raising the question: what maintains nuptial feeding when gifts do not benefit females? The sensory trap hypothesis proposes that nuptial feeding may be explained by pre-existing sensory responses that predispose females to ingest gifts. Recent studies have shown that male seminal proteins can induce a nonspecific increase in female feeding after mating, which may represent a sensory trap for nuptial feeding if it results in increased intake of post-mating gifts. I tested these ideas using female beetles that ingest a spermatophore after mating. I show that males stimulate strongly increased female feeding post-mating. However, there was little evidence for dose dependence in the feeding response that could allow males to stimulate feeding beyond the female optimum. Moreover, the post-mating feeding response could not explain nuptial feeding: despite feeding more in general, newly mated females were less likely than nonmated females to ingest spermatophore gifts.

Condition-Dependent Pheromone Signaling by Male Rock Lizards: More Oily Scents Are More Attractive

Pheromones of vertebrates are often a mixture of several chemicals with different properties and messages, and their production seems condition dependent. Thus, pheromones are a good, but little studied, example of multiple sexual signals. Femoral gland secretions of male rock lizards Iberolacerta cyreni contain steroids that may act as pheromones, but there are also many other lipids, such as oleic acid, whose allocation to secretions may be costly because it has to be diverted from body fat reserves. This suggests that oleic acid could also have some function in secretions. Chemical analyses showed that proportions of oleic acid in femoral secretions of males were positively related to body condition of males, suggesting that the oleic acid secreted may reflect the amount of body fat reserves of a male. Tongue-flick bioassays showed that females were able to detect by chemosensory cues alone differences in proportions of oleic acid in secretions of males. Scents of males with more oleic acid elicited stronger chemosensory responses by females. Further tests with chemical standards confirmed that females distinguished oleic acid, and changes in its concentration, from other chemicals that are naturally found in secretions of males. Moreover, choice trials of scent-marked substrates showed that females were more attracted to areas that were experimentally manipulated to increase the proportion of oleic acid in natural scent marks of males. We suggest that oleic acid in femoral secretions might be a reliable advertisement of a male's body condition, which females could use to select high-quality mates in conjunction with information provided by other chemicals. Alternatively, scent marks with more oleic acid might be simply more attractive to females if chemosensory responses of females to scent of males were originated by a preexisting sensory bias for food chemicals such as the oleic acid. Nevertheless, this sensory trap might have evolved into an honest signal because the elaboration of the signal seems differentially costly for males with different body conditions.

Why Do Males of the Spider Pisaura mirabilis Wrap Their Nuptial Gifts in Silk: Female Preference or Male Control?

AbstractMales of the spider Pisaura mirabilis present a nuptial prey gift to the female during courtship as a mating effort. The gift is usually round and wrapped in white silk. It was suggested that the wrapped gift functions as a sensory trap by mimicking the female’s eggsac implying that males exploit the female maternal care instinct and not her foraging motivation in a sexual context. The shape of the gift (round) and appearance (white) should then increase female acceptance of males. We tested these predictions experimentally and found that neither gift shape (round or oblong) nor silk wrapping (wrapped or unwrapped) facilitated female acceptance, in contrast unwrapped gifts were accepted faster than wrapped ones. Instead, we found that silk wrapping benefited the males because it significantly decreased the risk of females stealing the gift without copulation and consequently directly increased male mating success. Large oblong gifts were difficult for males to handle during copulation, resulting in shorter copulations for oblong vs. round gifts. Thus, round gifts were not preferred by the females but were beneficial to the males. Our results indicate two adaptive benefits to males of wrapping the nuptial gift: to reduce the risk of losing the gift to females without copulation, and make it possible to reshape an oblong prey into a round gift that facilitates the male’s access to the female’s genitalia. Our results suggest that the male gift wrapping trait may be selected though sexual conflict over remating rate.