Mate Guarding in Male Dall's Porpoises (Phocoenoides dalli)

Mate guarding, whereby a male closely attends and defends a fertile female from extra‐pair matings, is one mating tactic males of many species use to protect their paternity. Although female defense occurs in many species of terrestrial mammal, comparable examples among cetaceans are largely absent, potentially as a result of the wide dispersion and mobility of females and their prey. Here, we investigate whether the close association of individual male Dall's porpoises with individual females during the breeding season is consistent with mate guarding. As mate guarding is predicted to be costly, and in other taxa is often associated with a reduction in foraging efficiency, we also examine whether males trade‐off this activity with time at depth. Males maintained longer associations and closer distances with female partners than with male ones. They also surfaced in greater synchrony with, and more often approached, their female partners than male ones. In contrast to males with male partners, males paired with females engaged in agonistic interactions with other adult males, and infrequently affiliated with extra‐pair individuals. These data suggest males are actively attempting to maintain their associations with females, while also acting to reduce female extra‐pair copulations and increase their own paternity. Guarding males also undertook shorter dives than non‐guarding males, suggesting that they trade‐off time at depth with guarding. Such a trade‐off is likely to involve a reduction in foraging opportunities, due to a decrease in time spent at foraging depth. Mate guarding in this species may be facilitated by the relatively smaller size and decreased mobility of newly calved, estrous females, particularly if females also benefit from guarding.     

Mate Guarding in the Androdioecious Clam Shrimp Eulimnadia texana: Male Assessment of Hermaphrodite Receptivity

Precopulatory mate guarding primarily occurs when males encounter receptive females at a low enough rate that such females become a valuable resource once encountered. Such circumstances are common in aquatic crustaceans wherein females are only receptive for a short period directly after molting. In these species, males commonly mate guard by physically attaching themselves to their prospective mates for hours to days at a time. To be effective in mate guarding, males must be able to assess the time to receptivity in their mates, which is commonly via chemical cues associated with molting. Clam shrimp in the genus Eulimnadia exhibit mate guarding, but with an important variation: these species are mixtures of males and hermaphrodites (androdioecy) rather than males and females. Nonetheless, the mate guarding behaviors of these shrimp are much the same as in other aquatic crustaceans. In this study, three projects were undertaken to determine the ability of Eulimnadia texana males to assess hermaphroditic receptivity. Males were found to be unable to assess receptivity without physically contacting hermaphrodites. However, after physical contact, males spent a significantly greater amount of time guarding receptive relative to non‐receptive hermaphrodites. Additionally, male interest in mate guarding was highest during the period between the dropping of one clutch of eggs and the extrusion of the following clutch. Because this period is also associated with hermaphroditic molting, it is consistent with the notion that males cue into chemicals associated with molting to determine hermaphroditic receptivity. These findings are consistent with previous studies of mating behavior in this species, and we discuss their importance to future tests of optimal mate guarding planned for these shrimp.     

Part-Time Mate Guarding Affects Paternity in Male Reed Buntings (Emberiza schoeniclus)

Male mate guarding by close following has been reported in many socially monogamous bird species and is generally believed to function as a paternity guard. Many aspects of the dynamics and effectiveness of this behavior are still however poorly understood. Here, we describe the temporal variation in mate guarding behavior in male reed buntings (Emberiza schoeniclus) with a particular focus on how males allocate their mating effort between mate guarding and extrapair mating in a context of intense sperm competition. In our highly synchronous study population most males have to balance the simultaneous and mutually exclusive demands of mate guarding and seeking extrapair copulations (EPCs). We found that males frequently switched between guarding their mates and performing intrusions to neighboring territories. Both activities seemed to have significant fitness payoffs, as male mate guarding effort had a positive effect on paternity, and a large fraction of extrapair fertilizations occurred during the days when the sire guarded its own female. The reed bunting is thus an example of how discontinuous or part‐time mate guarding can still be effective in securing paternity. Female reed buntings were not particularly active in initiating EPCs as they never were observed performing extraterritorial forays. We argue that the absence of female‐initiated EPCs is a prerequisite for males to trade mate guarding against seeking EPCs. Otherwise, if females circumvent male mate guarding by timing their EPCs to periods of male absence, males should guard their mates almost continuously or rely on alternative paternity guards.     

Costs of Mate Guarding and Opportunistic Mating Among Wild Male Japanese Macaques

A trade-off relationship between mating and feeding effort is important when considering reproductive strategies of long-lived species. I compared the influence of male sexual activities, female mate-choice behaviors and the daily activity budget on male mating success among males in a group of wild Japanese macaques (Macaca fuscata yakui) on Yakushima Island. The 1st-ranking male, which had immigrated into the troop at this rank, more frequently approached peri-ovulatory females, spent more time grooming peri-ovulatory females and in mounting series and spent less time feeding than subordinate males did. The 1st-ranking male attained the highest mating success as a result of his high expenditure of time and energy in sexual behaviors directed toward peri-ovulatory females. Mating success of subordinate males did not relate to the amount of sexual effort, but instead to the frequency of female approaches, female rush toward males and the number of peri-ovulatory females within the group. The pattern of intermale competition shifted from nearly contest competition to scramble competition as the number of peri-ovulatory females in the group increased. Feeding time of subordinate males did not vary between the days when they copulated and the days when they did not. The findings demonstrate that mate guarding in the 1st-ranking male is a high-cost mating tactic, while opportunistic mating in subordinate males is a low-cost mating tactic. The differences in male mating tactics are probably related to male life history and to the formation of groups with a high socionomic sex ratio.     

Nuptial Coloration and Mate Guarding Affect Escape Decisions of Male Lizards Psammodromus algirus

Males of many species show conspicuous breeding colours that are important for status signalling, but that may decrease crypsis and increase predation risk. However, prey may adjust their escape response, such that the optimal distance at which an animal starts to flee (approach distance) would be the point where the costs of staying exceed the cost of fleeing. We examined in the field the escape response of Psammodromus algirus lizards, to test the hypothesis that more conspicuous old males, showing orange nuptial coloration on most of the head, which presumably have a higher probability of being detected (i.e. increased costs of staying), have longer approach distances, independent of other environmental variables. As predicted, old brightly coloured males had significantly longer approach and flight distances than young dull males, and young males had longer ones than females. In contrast, neither the distance to the nearest refuge nor the air temperature when the lizards escaped were significantly different. In addition, although male and female lizards differed in their use of microhabitats, old and young males did not differ. We also found that old males guarding a female (i.e. increased costs of fleeing) had shorter approach distances than old males that were found alone.     

Seasonal Changes of Vocal Rates and Their Relation to Territorial Status in Male Galápagos Sea Lions (Zalophus wollebaeki)

Male vocal displays play an important role in sexual selection through both male–male competition and female choice. While this is supported by numerous studies in birds, much less attention has been paid to the role of such displays in mammals. We investigated the function of vocal displays in a polygynous mammal, the Galápagos sea lion (Zalophus wollebaeki). In our study population a large proportion of mature males are unable to establish a territory, providing the opportunity to compare the vocal behaviour between territorial and non‐territorial males. We examined how seasonal patterns of vocalizations differed between territorial and non‐territorial males and how the number of females present in a territory influenced behaviour of territorial males. We found that territorial males vocalized at higher rates than non‐territorial males, and territorial males vocalized more at the onset than towards the end of territory tenure. During the onset of territory‐tenure vocalizations of territorial males were directed more often towards other males than females. Furthermore, we found that vocalizations of territorial males were not only given in male–male interactions, but were also actively directed towards females. Territorial males vocalized at higher rates when more females were present in their territory. Our results suggest that vocalizations are important in male–male interactions, are relevant in territorial disputes and are used as a proxy for females to assess a male’s quality.     

Male Mating Tactics in the Shrimp Palaemonetes pugio (Decapoda, Caridea): Precopulatory Mate Guarding vs. Pure Searching

The guarding of females approaching a limited period of sexual receptivity is a common mating tactic of males. In many decapod crustaceans, such as the shrimp Palaemonetes pugio , females can only copulate during a short period after a reproductive molt. It has been predicted that mate guarding by males (pre-copula) evolves in such species if sex ratios are not highly female-biased and if males can detect the molt stage of the female. The mating tactics of males were investigated in P. pugio . Time-lapse video observations were made on interactions among two males, a pre-molt female, and an inter-molt female (20 replicates). There was no evidence that males recognized a pre-molt female until 24 h before its molt. Significant numbers of male contacts with pre-molt females occurred 1 h before and after the female molt. Copulation took place within 1–3 min of the molt. No behavior commonly associated with mate guarding in decapods was observed – no clasping, agonistic behavior, or close association. It is concluded that the male's mating tactic is pure searching, wherein males haphazardly contact many females in order to find a receptive one. The high encounter rate in nature of these very mobile, aggregated shrimps is proposed as the factor responsible for the evolution of pure searching. It is hypothesized that pure searching is the male tactic of the many species of decapod shrimps with small males, sexually monomorphic cheliped weapons, and aggregated populations.     

The Conflict between Nest Guarding and Mate Guarding in Penduline Tits (Remiz pendulinus)

In penduline tits (Remiz pendulinus), polygynous males build several very elaborate nests successively during one breeding season to attract females. The time and effort invested in nest building is positively related to their mating success. Intraspecific competition for nest material resulting in nest material theft, delays males' nest building progress which in turn decreases their mating success. Therefore, a nest guarding strategy was predicted. In many bird species, males develop some kind of paternity strategy during the female fertile phase. However, as nest building and the female fertile phase frequently coincide, one would expect a trade-off between these strategies. In this study we determined in particular how nest guarding in males conflicts with their mate guarding behaviour in penduline tits. Our results show that nest building is costly in terms of a male's time budget. Thieves benefit by increasing their rate of acquiring nest material which reduces the effort invested in nest building. Nest guarding is an efficient strategy to avoid thieves, as indicated by the negative relation between the presence of the male near the nest and the frequency of nest material theft. Nest guarding is required for the whole building period but males, however, increased their mate guarding effort during the peak fertile phase to ensure their paternity. The data suggest that, for the trade-off “mate guarding versus nest guarding”, paternity insurance seems to be more important.     

Mate Discrimination in Invasive Whitefly Species

Mate discrimination could be critical for invasive species that need to locate rare suitable mates and avoid costs associated with misdirected courtships to establish in new environments. Here, we tested whether individuals of two invasive whitefly species in the Bemisia tabaci species complex, commonly known as the B and Q biotypes, could discriminate between potential mates based on their species and sex. Behavioral observations showed that B females were more discriminating than Q females. Males of both species were able to discriminate between mates based on their species and sex, but in general B males discriminated more effectively than Q males. By incorporating these behavioral data into a conceptual model, we show that variation in mating behavior between females of different species was a more significant factor affecting mating than variation between males. These results indicate that mate discrimination could affect interactions between whitefly species and influence a species’ ability to colonize novel environments.     

The Cost of Male Aggression and Polygyny in California Sea Lions (Zalophus californianus)

In polygynous mating systems, males often increase their fecundity via aggressive defense of mates and/or resources necessary for successful mating. Here we show that both male and female reproductive behavior during the breeding season (June–August) affect female fecundity, a vital rate that is an important determinant of population growth rate and viability. By using 4 years of data on behavior and demography of California sea lions (Zalophus californianus), we found that male behavior and spatial dynamics—aggression and territory size—are significantly related to female fecundity. Higher rates of male aggression and larger territory sizes were associated with lower estimates of female fecundity within the same year. Female aggression was significantly and positively related to fecundity both within the same year as the behavior was measured and in the following year. These results indicate that while male aggression and defense of territories may increase male fecundity, such interactions may cause a reduction in the overall population growth rate by lowering female fecundity. Females may attempt to offset male-related reductions in female fecundity by increasing their own aggression—perhaps to defend pups from incidental injury or mortality. Thus in polygynous mating systems, male aggression may increase male fitness at the cost of female fitness and overall population viability.     

Male Mate Choice in Trichogramma Turkestanica

In most animals it is the sex that invests the most in reproduction, generally the female, that expresses mate choice. However, in numerous species, males or both males and females are choosy. We investigated mate choice in males of the egg parasitoid Trichogramma turkestanica Meyer (Hymenoptera: Trichogrammatidae). We tested the impact of age and feeding status of males on their capacity to choose between virgin or mated and kin or non-kin females. As expected, males showed no preference between kin and non-kin mates, but inseminated virgin females over mated ones. No effect of age on the level of choosiness was found, but unfed males were choosier than fed ones. This is the first study to show an effect of feeding status of males on mate choice in insect parasitoids.     

Male Mate Choice in Lemur catta

Though females are generally more selective in mate choice, males may also derive reproductive benefits from exercising mate selectivity if one or more factors limit male reproductive success and females differ in reproductive potential. I used male mating effort as a proxy for male mate choice in ring-tailed lemurs (Lemur catta). I calculated mating effort as the rate of male-male agonism during each female's estrous period 30 min before and 30 min after the first and last mountings with intromission. I collected data on 1 free-ranging Lemur catta troop during 2 consecutive breeding seasons on St. Catherines Island, USA. In both yrs, male mating effort differed significantly among troop females once I adjusted male-male agonistic rates to reflect agonistic intensity, and I corrected for the number of observed mates per female (2000: χ² = 27.43, df = 3, p < 0.0001; 2001: χ² = 21.10, df = 3, p < 0.001). Results strongly suggest male mate choice. Contrary to expectation, males did not expend the greatest mating effort for females with the highest dominance status nor the highest reproductive success. Males preferred females that either: (1) belonged to the age class in which fecundity and infant survival is the highest at this site (4–9 yrs), or 2) were older females (≥10 yrs) with high reproductive success. Female reproductive potential appears to be an important variable determining male mating effort in Lemur catta.     

Sperm Competition in Humans: Mate Guarding Behavior Negatively Correlates with Ejaculate Quality

In species where females mate with multiple males, the sperm from these males must compete to fertilise available ova. Sexual selection from sperm competition is expected to favor opposing adaptations in males that function either in the avoidance of sperm competition (by guarding females from rival males) or in the engagement in sperm competition (by increased expenditure on the ejaculate). The extent to which males may adjust the relative use of these opposing tactics has been relatively neglected. Where males can successfully avoid sperm competition from rivals, one might expect a decrease in their expenditure on tactics for the engagement in sperm competition and vice versa. In this study, we examine the relationship between mate guarding and ejaculate quality using humans as an empirical model. We found that men who performed fewer mate guarding behaviors produced higher quality ejaculates, having a greater concentration of sperm, a higher percentage of motile sperm and sperm that swam faster and less erratically. These effects were found independent of lifestyle factors or factors related to male quality. Our findings suggest that male expenditure on mate guarding and on the ejaculate may represent alternative routes to paternity assurance in humans.     

Mate Guarding in the Cricket Gryllodes sigillatus: Influence of Multiple Potential Partners

There are several hypotheses as to the function of postcopulatory mate guarding. Control over the mate-guarding period by either sex could potentially influence relative reproductive success. Mate-guarding behaviour in Gryllodes sigillatus was studied under several conditions: 1. undisturbed pairs; 2. pairs with a single male intruder; 3. pairs exposed acoustically, visually and olfactorily to several other males; 4. pairs exposed freely to several other males; and 5. pairs exposed freely to several other females. The results provide support for the spermatophore retention and rival defence hypotheses. The efficacy of mate guarding was not compromised by the pair being in acoustic, visual and olfactory contact with several other males. Once pairs were exposed to free contact with several other males, the spermatophore retention time by the female declined significantly, indicating that the mate guarder's efficiency declines under competition from several rivals. In pairs exposed to contact with several females after mating, the mate-guarding period and spermatophore retention time declined as the mate guarder abandoned the mated female and pursued the other females. Termination of the effective mate-guarding period by either sex seems to be influenced by the number of other potential partners present.     

Absence of Mate Guarding in the Yellowhammer (Emberiza citrinella)?

The mate guarding behaviour of male yellowhammer (Emberiza citrinella) was studied with special reference to the effects of age, body size (tarsus length) and coloration of males. Measurements of intra-pair distance do at the most provide evidence for relatively lax mate guarding. On the other hand, patterns of male song activity and inter-male aggression were more in agreement with the predictions of the mate guarding hypothesis. The reasons for the comparatively low mate guarding intensity in the yellowhammer may be that males do not need to guard their mates intensely. Age differences were found in song and aggressive activity, older males singing and fighting the most. Size had no effect on guarding behaviour. Coloration was correlated with inter-male aggressiveness and conflict initiation propensity. Less colourful males fought the most in the pre-fertile period of their mates, whereas colourful and old males fought the most during the fertile period. This suggests that coloration may be an indicator of individual fighting and guarding ability.     

Model of Familiarity Discrimination in the Perirhinal Cortex

Much evidence indicates that recognition memory involves two separable processes, recollection and familiarity discrimination, with familiarity discrimination being dependent on the perirhinal cortex of the temporal lobe. Here, we describe a new neural network model designed to mimic the response patterns of perirhinal neurons that signal information concerning the novelty or familiarity of stimuli. The model achieves very fast and accurate familiarity discrimination while employing biologically plausible parameters and Hebbian learning rules. The fact that the activity patterns of the model's simulated neurons are closely similar to those of neurons recorded from the primate perirhinal cortex indicates that this brain region could discriminate familiarity using principles akin to those of the model. If so, the capacity of the model establishes that the perirhinal cortex alone may discriminate the familiarity of many more stimuli than current neural network models indicate could be recalled (recollected) by all the remaining areas of the cerebral cortex. This efficiency and speed of detecting novelty provides an evolutionary advantage, thereby providing a reason for the existence of a familiarity discrimination network in addition to networks used for recollection.     

Flexible Mate Guarding Tactics in the Dragonfly Sympelrum Internum (Odonata: Libellulidae)

Mate guarding–a behaviour prevalent in odonates–is a post copulatory association during which males prevent females from re-mating. Some species use two forms of guarding: contact mate guarding, which is energetically costly but highly effective and non-contact mate guarding, which is less costly but less effective. This study aimed to determine if male Sympetrum internum (Odonata:Libellulidae) adjust the duration of contact mate guarding according to environmental, temporal and physiological factors. There was a significant interaction between male density and season on duration of contact mate guarding. Early in the season males increased the duration of contact guarding as the density of rivals increased. Later in the season males guarded mates longer irrespective of male density. Wind and temperature did not detectabiy alter the duration of contact mate guarding, suggesting that the trade-off between current and future reproductive success was more important than were physiological costs.     

Male Mate Preferences in the Mosquitofish Gambusia holbrooki

Although male mosquitofish invest little in their progeny, the simultaneous availability of many potential mates and the large variance in their quality are expected to favour the evolution of mechanisms of male mate choice. Males of Gambusia holbrooki were shown to exhibit sexual preferences when presented simultaneously with two potential mates. When females differed in size, males showed more sexual activity directed at the larger of the two and the time spent with this female increased with the difference between the two females. This preference, however, was lower than expected if males spent time in direct proportion to the difference in fertility between females. In the second part of the study, females which had just delivered were found to be clearly preferred over gravid females. Attractiveness of females dropped after the third day, and disappeared in the sixth day after parturition. The results are discussed in relation to the probable occurrence of sperm competition and sperm displacement in this species.