Costs of courtship and mating in a sexually cannibalistic orb-web spider: female mating strategies and their consequences for males

The costs of courtship and mating may include increased risks of predation, the transmission of pathogens, and a loss of foraging opportunities. Thus, a female's decision to tolerate a courting male will depend upon how these costs offset the benefits of mating, which will depend on her reproductive and nutritional status. While these costs may be similar for mated and unmated females, the benefits of mating will be less for mated than virgin females. However, the cost of lost foraging opportunities may be higher for females with fewer nutritional reserves necessary for forming eggs. We examined how these costs and benefits influence the courtship and mating behaviour of male and female orb-web spiders, Argiope keyserlingi. In the field, females on webs that also contained a courting male intercepted fewer prey items per hour than females on webs without a male. In the laboratory, the presence of a courting male at the hub also attracted mantid predators to the web, increasing the risk of predation for both male and female. Staged mating experiments in the laboratory revealed that the frequency of female attacks and pre-copulatory cannibalism was greater among mated than virgin females. Feeding history did not affect aggression in virgin females but, among mated females, food-deprived spiders attacked and cannibalized males more frequently than sated females and only the latter ever remated. These differences in female behaviour influenced male mating strategies. Choice experiments demonstrated that males preferred to venture onto the silk threads of virgin rather than those of mated females. Similar patterns of mate selectivity were observed in the field; females with narrow abdomens attracted more males to the webs than females with broad abdomens, and copulations were observed more frequently among females with narrow abdomens. These smaller females are likely to be virgins that have recently molted. Males that preferentially mate with virgin females will not only avoid potentially fatal attacks but also obtain, on average, a higher fertilization success.     

Male remating and female fitness in the wolf spider Pardosa astrigera: the role of male mating history

Although the effects of male mating history on female reproductive output and longevity have been studied in insects, few such studies have been carried out in spiders. In a mating system in which females are monandrous while males are polygynous, females may incur the risk by mating with successful males that have experienced consecutive matings and suffer from the possible depletion of sperm and/or associated ejaculates. Here, we examine the effects of male mating history on male courtship and copulation duration, female reproductive fitness, and female adult longevity of the wolf spider, Pardosa astrigera. Results indicated that male mating frequency had little effect on their subsequent copulation success, and of 35 males tested, about half of the males were able to copulate with five virgin females successively at an interval of 24 h. Male mating history had little effect on their courtship duration. However, male mating history significantly affected male copulation duration, female adult longevity, and reproductive output. Males that mated more frequently copulated longer and more likely failed to cause their mates to produce a clutch, although there was no significant difference in the number of eggs laid and the number of eggs hatched regardless of the first clutch or the second one. Multiple mating of male P. astrigera resulted in significant reduction in female adult longevity. Our results indicate that monandrous females mating with multiple-mated males may incur substantial fitness costs.     

Exogenous testosterone increases female aggression in the European starling (<Emphasis Type="Italic">Sturnus vulgaris</Emphasis>)

In the European starling, Sturnus vulgaris, optimal mating systems differ between males and females. Males gain from polygyny, whereas monogamy increases female fitness. The cost of polygyny to females lead to intense female–female competition, and it has previously been shown that the intensity of female aggression during the pre-breeding period can predict the realised mating system. The physiological regulation of such female aggression in starlings is not yet known. This study examines the role of testosterone in mediating aggressive behaviours involved in intra-specific reproductive competition in female starlings. Testosterone levels were experimentally elevated with testosterone implants in females during the pre-laying period. To simulate a situation in which an additional female tried to mate with the focal female’s mate, a caged female was presented close to a nest-site to which the male could attract a secondary female. Testosterone was significantly related to several behaviours involved in female–female interactions. Females with testosterone implants spent significantly more time close to the caged female and produced more song bouts than control females. In contrast, male behaviour was unrelated to the experimental status of the mate. Females mated to males that attracted a secondary female were less aggressive towards the caged female than those that remained monogamously mated. The effect of exogenous testosterone in this study indicates that androgens may mediate social behaviours in female starlings during the breeding season.     

Moulting and reproduction of the spiny lobster Jasus edwardsii (Decapoda: Palinuridae) in northern New Zealand

Aspects of moulting and reproduction of a primarily adult population of the spiny lobster Jasus edwardsii (Hutton) (Palinuridae) were investigated in the field and at an adjacent laboratory in northeast New Zealand from 1982 to 1986. Most males moulted in October/November, ensuring they were in intermoult stage at mating. Females moulted in late April–June, 2 to 3 mo later than females from more southern latitudes. For individual females the specific timing of ecdysis and mating and the length of the interval between them were related to size. Larger females (125 to 135 mm carapace length), tended to moult earlier and wait longer (up to 38 d) before mating, but did so prior to smaller females (95 to 105 mm carapace length, CL) which moulted later, but mated within as few as 9 d. These differences are explained equally well by size-dependent growth processes and by social or chemical inhibition by larger females. Most spiny lobsters (93 to 131 mm CL) moulted at night at depths <10 m. No clear reasons for these behaviours could be found. Eggs were incubated for 101 to 116 d by females in the study population, 70% of the time recorded for more southern areas, these differences probably being related to differences in water temperature. A consequence of earlier female moulting and egg-laying, and longer egg-incubation periods with increasing latitude is that the majority of J. edwardsii larvae hatch in September–November.     

Movements of lobsters (Homarus americanus) tagged in the Bay of Fundy,Canada

Of the 18 359 American lobsters (Homarus americanus) tagged and released at three locations in the Bay of Fundy during 1977–1980, 5 375 lobsters (29.3%) were recaptured within 6 yr of release. Mature lobsters (95-mm carapace length, CL) on average moved significantly greater distances than immature lobsters (<95-mm CL). Many (16.4%) of the mature lobsters were recaptured >92.6 km (50 nautical miles) from the release sites; the farthest distance moved was 798 km for a male at liberty for 3.5 yr. Examination of the direction of movements indicates some intermixing of lobsters within the Bay of Fundy, and throughout the Gulf of Maine and the adjoining Continental Shelf and slopes. Mature lobsters were recaptured in deeper waters during winter than during summer. The seasonal shallow-deep migration of mature lobsters in the Bay of Fundy is possibly associated with maximizing degree-days for molting, growth, gonadal development, and egg development. In some areas, mature females on average moved farther and seasonally earlier into deeper waters than mature males. Although the seasonal migration resulted in many lobsters returning to the original release area year after year, some lobsters made extensive long-distance movements away from the Bay of Fundy. Temperature-dependent, seasonal deep-shallow migration can explain both the local returns and the long distance migrations of mature lobsters in the Bay of Fundy and the Gulf of Maine. To achieve appropriate seasonal temperature regimes, mature lobsters have to move different distances and directions, depending on local topography.     

Ecdysial rhythms in megalopae and first instars of the Dungeness crab Cancer magister

Diel molting cycles of megalopae and first instar Dungeness crabs Cancer magister Dana captured in the Grays Harbor estuary (46° 55N; 124° 05 W) in May 1991 were studied under laboratory conditions. Sixtyone percent of the megalopae and 76% of the first instar crabs molted during periods of ambient darkness under a normal light — dark diel regime, and molting pattern was not affected by changes in the photoperiod (24 h daylight or 24 h darkness). Time until metamorphic molt increased as conspecific density increased. Habitat type (shell or mud) did not affect time until molt of megalopae and first instar crabs, nor did it affect daily molting rhythm of first instars. We hypothesize that nightly ecdysis of megalopae and first instar Dungeness crabs and density-dependent molting may be an adaptive response to predation and cannibalism among young-of-the-year.Contribution No. 875 from the School of Fisheries, WH-10, University of Washington, Seattle, Washington     

Influence of mating order on courtship displays and stored sperm utilization in Hermann's tortoises (Testudo hermanni hermanni)

Sperm storage is widespread in many vertebrate groups, and it is frequently associated with promiscuous mating systems. Chelonian species are one of the most outstanding examples of a promiscuous group capable of long-term sperm storage; specialized structures have evolved within the oviducts of these vertebrates to ensure sperm vitality across reproductive cycles. Thus far, few studies have investigated the factors regulating multiple paternity, sperm usage by females and paternity distribution in successive clutches. This study aimed to investigate the effect of mating order on male mounting and reproductive success in Testudo hermanni hermanni, combining behavioural and genetic data. A series of planned matings were performed, within which experimental females were mated sequentially to two different males under controlled conditions. Observations conducted during experimental matings revealed that courtship displays did not significantly differ between the first and second males to mate with a female. Interactions ending with a mount were characterized by a significantly higher intensity and occurrence of determinate courtship behaviours, for example biting and running after the female. Paternity analysis performed on hatchlings produced from experimental females revealed that 46 % of the clutches were multi-sired. A significant contribution of previous years' partners was still found, thus confirming the long-term sperm storage within the female oviduct in this species. Finally, mating order did not significantly affect the reproductive success of experimental males during the on-going reproductive season.     

Male-male competition selects for delayed sex change in the protandrous shrimp<Emphasis Type="Italic"> Pandalus latirostris</Emphasis>

In most protandrous species, male size advantage is generally regarded as unimportant in determining the timing of protandrous sex change. In pandalid shrimp, the size/age of male sex change often fluctuates among years and populations, but the adaptive significance of late reversing males (LRMs) is not well understood. This study experimentally examined the adaptive significance of LRMs in the protandrous pandalid shrimp Pandalus latirostris Rathbun. Field and laboratory studies were carried out in August–September of 1998–2002 on P. latirostris in Notoro Lagoon, Japan (44°03′N; 144°10′E). Mature females that had molted (i.e. mate receptive) were tethered in the field and their mating behavior with wild males was observed. Copulations occurred with a single male at a time, although other males could sequentially mate with a tethered female. Because tethered females rejected male approaches, males had difficulty transferring their spermatophores. In the laboratory, males copulated with non-tethered, recently molted females for only 15 min after molting. Recently molted females are wary of potential predators, since their soft exoskeleton makes them particularly vulnerable. Fast access by males enhanced fertilization success in this shrimp. The effect of male size on mating success in the laboratory was examined. Both small and large males successfully inseminated females in the absence of competitors. In experiments where large, medium, and small males competed for a female, however, larger males guarded females longer than smaller males, until the female molted and became receptive. Moreover, large males were more successful at copulating once molting occurred. These results imply that male-male competition drives delayed sex change in some situations.     

Fecundity,egg weight and longevity in relation to multiple matings in females of the monarch butterfly

Summary In many insects nutrients transferred by the male at mating are later incorporated into both the eggs and soma of the mated females. Accordingly, it has been suggested that insect females can use these male-derived nutrients for somatic maintenance and enhancement of their fecundity and fitness of their offspring. I this paper we tested the validity of these predictions by studying the longevity and reproductive output of 1, 2, 3, 4 or 5 times mated female monarchs Danaus plexippus, a nectar-feeding butterfly that is long-lived and strongly polyandrous and emerges as an adult without mature eggs. Females mated five times received ejaculates that corresponded to an average of 38% of their body weight at eclosion. However, we found that the number of times females had mated had no effect on their longevity, life-time fecundity, or egg weight. Although negative evidence should always be interpreted with caution, our study suggests that male-derived nutrients are less important for female longevity and reproductive output than are larval and adult food.     

Reproductive sharing and proximate factors mediating cooperative breeding in the African wild dog (Lycaon pictus)

Although dominant African wild dogs (Lycaon pictus) are generally believed to be the sole breeders within a pack, earlier behavioral and endocrine data suggest that reproduction could be shared with subordinates. We performed an extensive behavioral, demographic, and genetic evaluation of a wild dog population in South Africa to examine the level of such sharing and the proximate mechanisms influencing reproductive contributions of each sex. While a majority of pups were born to dominants because of a lack of subordinate potential breeders, we discovered a substantial portion of reproductive sharing between dominants and subordinates. Compared with alpha females that mated annually, subordinate beta females bred in 54.5% of years whereas thetas never bred. The three top-ranking males all sired pups (56.0%, 32.0%, and 12.0%, respectively) when three or more adult males were present. With only two pack males, alpha and beta individuals shared reproduction nearly equally (55.2% and 44.8%, respectively), and litters of mixed paternity were discovered on eight of 15 (53.3%) occasions. A skewed adult sex-ratio and frequent alpha mortalities for females and behavioral aggression in males allowed most individuals to attain dominant status in their lifetime, creating a constantly shifting social hierarchy. Genetic parentage results corresponded to reported hormone profiles, suggesting physiological suppression in some lower-ranked individuals of both sexes. Thus, a combination of demographic, behavioral, and hormonal proximate factors mediates reproductive partitioning in wild dogs. We conclude that reproductive sharing can be significant in this species, especially for males that have less robust suppressive mechanisms than females.     

The assessment of female reproductive state during courtship and scramble competition in the fiddler crab, Uca paradussumieri

Male fiddler crabs, Uca paradussumieri, mate underground during a 4- to 7-day period each full and new moon. As soon as the tide recedes, males enter the burrows of females that will ovulate the following day ('pre-ovigerous' females). Males copulate with and guard these females until they ovulate. When interrupted by an intruding male, the first male to reach the female is usually able to defend her and successfully mate with her. In fiddler crabs, females mate multiply and there is last male sperm precedence. Before each semi-lunar mating period, male U. paradussumieri were more likely to court females with whom they would later mate than other nearby females with whom they did not mate. This suggests that males collect information on female reproductive state prior to the females becoming ovigerous. In this species, aggression was common between males that courted the same female. When previously courted females were approached by other males, the initial courter attempted to forcefully disrupt the courtship. This behavior may allow males the exclusive use of information on female reproductive condition. It also suggests a type of scramble competition between males over females. Furthermore, it indicates that males are able to locate receptive females prior to their becoming ovigerous. The shorter guarding period observed in this species, as compared with other fiddler crabs, is caused by females rejecting longer guarding periods. Male ability to assess female reproductive status may therefore be advantageous because it increases male mating success within a scramble type of competitive polygyny.     

Correlates between number of mates,shelter availability and reproductive behavior in the Tautog Tautoga onitis

Earlier studies on reproductive behavior of the tautog Tautoga onitis under laboratory conditions indicated that differences in courtship and spawning behavior were apparently related to the number of males attempting to spawn with a female. It had also been conjectured that certain ecological factors such as availability and distribution of food and shelter would play a role in the establishment of territoriality and defense of a female, indirectly influencing courtship activities and the resultant spawning mode. In the present work we have examined this question more closely by varying the number of males, females and amount of shelter available. Regardless of the social situation, in every instance single males, through aggression, attempted to limit access to a female and pair spawn. The degree to which this succeeded depended on the male's place in the dominance hierarchy, the number of males in proximity which were actively attempting to spawn and the availability of shelter. Courtship activity of the female was influenced by the amount of male attention. When attention was high, the nuptial shading of the female never developed maximally. On the other hand, when male attention was low, the female showed progressive and maximal shading development to attract males. The significance of the findings is discussed.     

Tactics, effectiveness and avoidance of mate guarding in the blue-footed booby (Sula nebouxii)

We examined the dynamics and avoidance of mate guarding, by males and females, in the blue-footed booby, in which the two social mates are usually simultaneously present on the territory but each of them is unmonitored by the other for one-quarter of its time. Both sexes were promiscuous and liable to switch mates. Cuckolded individuals did not increase their overall presence on the territory, but in response to the extra-pair (EP) courtships of their mates, both sexes doubled their rate of intra-pair (IP) courtship and sometimes showed aggression. The male or female's presence depressed the social mate's EP activity, but intra-pair courtship had no such effect, tending even to propitiate that EP activity. Similarly, when females responded to their social mates' EP courtship with approach or aggression, disruption of EP activity was short-lived. Promiscuous females modified their diurnal pattern of attendance, as if attempting to sidestep monitoring by their mates, but cuckolded males matched the modification. Both sexes tended to perform their EP activities at a distance when their mates were present, possibly to evade monitoring or disruption by their mates. Male and female boobies cannot monitor their mates continuously, they do little to facultatively adjust their presence on territory to the risk of infidelity, and their immediate responses to overt infidelity have only the briefest impact; but the information they acquire while monitoring their mates may be critical to constraining their mates' infidelity and also to calibrating their own reproductive investment.     

Mating in the afternoon: Time-saving in courtship and remating by females of a polyandrous butterfly Pieris napi L.

Summary Among butterflies where females are polygamous, interactions with males after the first mating entail time costs associated with both courtship and mating. In the green-veined white butterfly, Pieris napi, spermatophore counts on wild-caught females revealed that the average number of matings that females had performed increased gradually from 1.1 during the first week of the flight period to 2.4 during the 4th and final week. By dissecting pairs found in copula in the field, we found that female rematings occurred solely in the afternoon, whereas virgin females mated most frequently earlier in the day. We suggest that non-virgin females minimize the time cost of rematings by allocating them to an hour when the egglaying frequency has decreased to a low level. Virgin females were very attractive to males, judging by their courtship persistence (several minutes), but when mated, females became so unattractive that courting males left them within a few seconds. However, females' attractiveness increased again with time elapsed since the last mating. These observations support the idea that females emit repellent pheromones after mating, which may be male derived. Since newly mated females were not harassed by males or hindered in their egglaying activities, it is conceivable that the time cost of remating may be outweighed by the benefit of the regained ability to curtail male courtship. This advantage to newly remated females may in itself be an explanation for polyandry in P. napi and is alternative or complementary to the idea that females that remate receive a material benefit that can be used to increase their realized fecundity.     

Patterns of sexual cohabitation and female ejaculate storage in the American lobster (<Emphasis Type="Italic">Homarus americanus</Emphasis>)

Little is known of the time and ejaculate allocation strategies during mating of American lobster, Homarus americanus. This study investigated sexual cohabitation and female ejaculate accumulation patterns in a laboratory mating experiment, as well as female seminal receptacle load in exploited populations in the waters of the Magdalen and Anticosti Islands, in eastern Canada. In the laboratory experiment, the length of sexual cohabitation was proportionate to female size for large but not for small males. Also, large males cohabited with pre- and postmolt females longer than small males. These different time investment strategies can be explained by different mutual benefits. In the field and laboratory, larger females accumulated more ejaculate than smaller ones. This suggests that male lobsters tailor ejaculate to female size, a reliable index of her reproductive potential. Moreover, similarly-sized females accumulated more ejaculate when mated with large compared to small males. Comparison of receptacle loads between wild-mated and laboratory-mated females suggests that the former were mating mainly with smaller males, although some evidence of positive size-assortative mating existed, especially at the less exploited Anticosti site. The results are discussed in the context of evolutionary theory and of proposed management measures to increase egg production in exploited populations.Communicated by T. Czeschlik     

The basis for female choice in an avian brood parasite

Summary Behavioral observation and experimental manipulation of a marked population of brood parasitic brown-headed cowbirds (Molothrus ater) were conducted to determine whether or not females exhibit mate choice and to elucidate the ultimate basis for any such choice. Female choice was indicated by the fact that each female copulated with only one male, although most were courted by several. Patterns of female aggression towards males also revealed that females had the opportunity to display choice. Courtship by males was sometimes treated by females as harassment, but there was no conclusive evidence that a male provided his mate with protection from harassment by other males. Nor was there any indication of other proximate benefits or services males might have provided for females. Thus, there is no evidence that males provide females with anything other than their genes. An experimental removal of mated males and the pattern of subsequent remating of widowed females are consistent with female choice for male genetic quality. Offprint requests to: D.A. Yokel at the present address     

Effect of water temperature on the courtship behavior of the Alpine newt Triturus alpestris

Temperature is expected to have an effect on the behavioral patterns of all organisms, especially ectotherms. However, although several studies focused on the effect of temperature on acoustic displays in both insects and anurans, almost nothing is known about how environmental temperature may affect ectotherm visual courtship displays and sexual performance. The purpose of this study was to determine the effect of environmental temperature on the sexual behavior of Alpine newts (Triturus alpestris). We subjected T. alpestris to two different temperatures in controlled laboratory conditions. Temperature had a major effect on both male and female behaviors: at low temperature, the frequencies of several displays, including tail-raising during sperm deposition, are lowered. This variation is caused indirectly by temperature because it is due to female responsiveness, which is temperature-dependent. However, the fanning movement of the males tail during its main courtship display is independent of female behavior: at lower temperatures, the tail beats at a lower rate, but for a longer time. The similar reproductive success (i.e. sperm transfer) at the two temperature ranges indicates that breeding in cold water is not costly but instead allows males and females to mate early in the season. This is particularly adaptive because, in many habitats, the reproductive period is shortened by drying or freezing conditions, which may impair survival of branchiate offspring. This study also demonstrates the necessity of considering environmental parameters when modeling optimality and characteristics of ectotherm behaviors.Communicated by W. Cooper     

Unattractiveness of mated females to males in the parasitoid wasp Spalangia endius

Despite common stereotypes, males are not always indiscriminate and eager when it comes to mating. In the parasitoid wasp Spalangia endius, the initial response of males to females was almost always one of apparent excitement; however, this was followed by a clear preference for virgin females over mated females in both no-choice and choice situations. The no-choice data were collected from videotapes of male-female pairs of all possible combinations of mated and virgin individuals. Neither female nor male mating status had a significant effect on likelihood of, or time until, contact or male courtship fanning. However, a males first retreat was sooner when the female was mated than when she was virgin; mated males exhibited their first retreat sooner than did virgin males; and mated females were less likely to be mounted than were virgin females. In addition to the videotapes, male-choice experiments were performed. When given a choice of a virgin and a mated female, both virgin and mated males were more likely to mount and copulate with the virgin. The difference in response to virgin versus mated females seemed to be less in virgin males than in mated males, perhaps due to virgin males greater eagerness to mate: when a virgin male and a mated male were presented with a dead virgin female, the virgin male was usually the first to respond to the female. That males preferentially retreated from and avoided mounting mated females appears to be adaptive given that mated females rarely copulated.Communicated by N. Wedell     

Damselfly females prefer hot males: higher courtship success in males in sunspots

Males of some territorial calopterygid damselflies show an elaborate courtship display that involves high-frequency wing-beats directed toward an incoming female. Although it has been suggested that female mate preference is based on some characteristics of male’s courtship display, it is unclear whether the courtship display varies between males or is influenced by environmental conditions. We combined two recent technologies, thermographic imaging and high-speed digital videography, to show that the wing-beat frequency during courtship (i.e., courtship intensity) in a damselfly, Mnais costalis, is correlated with thorax temperature. Our data indicated that (1) male thorax temperature was associated with solar exposure in his territory, (2) environmentally derived thermal gain enhanced courtship intensity, (3) hotter males were more likely to copulate than others, and (4) female thorax temperature during oviposition within a territory was associated with solar exposure. Males with territories that have longer exposure to sun spots are expected to attain higher thorax temperatures for longer and so are able to successfully court more females. We suggest that females benefit from mating with hot males because they will be on a warmer territory while ovipositing. Hot males might also have greater mate guarding ability, and/or eggs may develop faster in warmer territories.     

Multiple signals in the palmate newt: ornaments help when courting

There is increasing evidence that female mate choice is often based on the assessment of multiple male traits, involving both morphology and behavior. We investigated female mate choice for multiple male traits in the palmate newt, Lissotriton helveticus, including male tail filament length, hind foot web size, crest development, body size, ventral coloration, and courtship display activity. Observations of courtship display in the field revealed that females spent more time in front of males with longer tail filaments. Laboratory experiments revealed a more detailed relationship between filament length and courtship display. We found that females took more sperm masses from males with both longer filaments and greater display activity. Experimental shortening of the tail filament length substantially decreased the number of male sperm masses transferred. However, when we experimentally reversed relative filament length between two males in mating trials, male mating success was explained by courtship activity and not by filament length. Our results show that female palmate newts value multiple traits during mate choice, including both morphological ornaments and reproductive behaviors in males. Our results further suggest that, when filament length is below a certain threshold, females may value the information content of courtship activity over that of filament length.