Harem Males Research Articles

Assessing the Home Range, Foraging Pattern and Roost Fidelity of Greater Short-nosed Fruit Bat (Cynopterus sphinx) in a Semi-Urban Environment

Radio telemetry is a method used in wildlife ecology to examine the movements and behaviours of animals, as well as to define their home ranges and habitat preferences. Bats, a highly diverse group of mammals, are recognized for their essential contributions to ecosystems, including seed dispersal, pollination, and pest control through their foraging activities. This study utilised radio telemetry to explore the basic foraging behaviours, range of movement, and roosting flexibility of the Cynopterus sphinx species. A total of 15 bats were equipped with compact, hand-wired, two-stage transmitter radio devices, including two harem males, nine harem females, and four non-harem males. Three groups used TRX-1000S receivers and collapsible 5-element Yagi antennas to track these radio-tagged bats. Our findings indicate that the radio-tagged female bats were the first to leave their roosts, with emergence times between 18:15 and 19:18 hrs. In contrast, harem males emerged last, following the quicker departure of non-harem males. The harem males covered an average foraging distance of 2.4 km (±0.3 km), whereas non-harem males travelled further. Both male and female bats visited multiple feeding sites nightly, with females travelling an average distance of 4.5 km (±0.9 km). Time spent at foraging sites varied among individuals. Males show higher roost fidelity than females, who frequently move between harems and roost sites. The study highlighted gender-specific differences in emergence times and distinct foraging behaviours, underlining the importance of understanding these patterns for conservation and habitat management efforts, which are crucial for supporting bats' roles as providers of ecosystem services.

Male condition and group heterogeneity predict extra-group paternity in a Neotropical bat

Extra-group paternity, in which offspring are sired by a male outside the breeding group, may alter the distribution of reproductive success in a population, thus affecting the opportunity for sexual selection. Both inter- and intraspecific studies have focused largely on mating systems in which females choose their social mates, and less is known about extra-group paternity in polygynous systems in which social mates are largely dictated by male-male competition. In this study, we examine the frequency and distribution of extra-group paternity in a harem-forming bat, Phyllostomus hastatus. We find that despite aggressive harem defense, males are unable to fully monopolize reproduction within their harem and over 70% of harems contain extra-group offspring. Harem males in better body condition suffered less paternity loss, but we found no effect of male age or body size. Even though the age and size of individual females did not predict offspring paternity, we found a significant effect of age heterogeneity within the group. Harems composed of differently aged females were more likely to contain extra-group offspring. Our results not only provide evidence for the role of male defense in preventing extra-group paternity but also suggest that social group composition has consequences for male reproductive success. In polygynous societies, the ability to monopolize mating is critical to reproductive success. As the group size increases, defense often becomes more difficult, resulting in increased rates of extra-group paternity. We find that among greater spear-nosed bats, extra-group offspring occur in most harems, but the overall rate of extra-group paternity is relatively low despite their large harems (15–30 females). Variation in the rate of extra-group paternity between harems is explained by male body condition (i.e., relative mass) but not harem size. Additionally, the rate of extra-group paternity is not explained entirely by male attributes, as we find that age heterogeneity within the female group is a significant predictor of the extra-group paternity rate. Our results support the hypothesis that not only the physical condition of a male influences his ability to monopolize reproduction but also the group composition influences the female mating behavior.

Experimental manipulation of reproductive tactics in Seba's short-tailed bats: consequences on sperm quality and oxidative status.

To reproduce, males have to fertilize the female’s eggs, sometimes in competition with ejaculates of other males. In species where males display alternative reproductive tactics, whereby territorial males secure mating and non-territorial males have to sneak copulations, the latter might be expected to invest relatively more resources towards sperm quality compared with the territorial males. Sperm cells are especially vulnerable to oxidative stress, which reduces male fertility. Therefore, antioxidant resources are expected to modulate sperm quality, and might be allocated differently between reproductive tactics. To test the link between reproductive tactics, redox profile and sperm quality, we experimentally induced changes in the reproductive tactics of 39 captive males Seba’s short-tailed bats Carollia perspicillata. We monitored the blood and ejaculate oxidative balance, and the sperm quality before, 7 days and 21 days after the manipulation of reproductive tactic. Although ejaculates’ oxidative damage was negatively related to sperm velocity, males exhibited similar blood and ejaculates redox profiles and similar sperm quality, regardless of their reproductive tactic. Possibly, these results arise as a consequence of some constraints having been lifted during the experiment. Our results also suggest that, in Seba’s short-tailed bats, the expression of alternative reproductive tactics is not subjected to strong oxidative constraints. Furthermore, our results could reflect an absence of trade-off between pre- and post-copulatory traits in harem males, as they could be selected to invest both in female attraction and sperm quality, as a consequence of their inability to fully monopolize females.

Male Resource Defence Behaviour Strengthens Harem Size in Promiscuously Mating Fruit Bats

Mating success in group forming animals largely depend on the ability of same-sex competitors (usually males) to monopolize local resources that are spatially limited and are of importance to their sexual partners. Across taxa, this resource defence behaviour (RDB) is predicted to maximize male reproductive success. Although RDB is widely observed in polygynous societies, its significance as an alternative male mating strategy among randomly mating individuals (i.e., promiscuous) is a less explored topic in ethology, especially within Chiroptera. In this study, we elucidate the relationship between RDB (measured here as male tent defence behaviour) and the harem size associated with adult males of Cynopterus sphinx. From 12 independent resident male removal experiments, we found that inter-male aggressive combats often exclusively occur while defending foliage tents in mating seasons. Further, our harem census data of usurper males (during usurpation) and resident males (post release), suggests a significant bias among females to preferentially roost with the resident males. This preferential association between harem females and the resident males that almost always recovers the foliage tent from the usurpers, suggests that C. sphinx harem males use RDB as an alternative mating strategy to monopolize roosting resources and maintain large harems. However, further research is required to identify the direct effects of RDB on individual male reproductive success.

Effect of female group size on harem male roosting behavior of the Indian short-nosed fruit bat Cynopterus sphinx

Mate guarding has been known to incur costs and cause constraints for harem males in many polygynous species. However, the effect of female group size on the harem male’s time budget in bats has received very limited attention. The Indian short-nosed fruit bat, Cynopterus sphinx, exhibits resource defense polygyny, in which tent roosting males construct tents and defend multiple female bats. We studied the effect of female group size on three aspects of harem male behavior: social grooming by reciprocal licking, tent maintenance, and tent guarding in the mast tree Polyalthia longifolia. In the process of reciprocal licking, all the bats in the harem were drenched in saliva before emergence, and this activity was positively and significantly correlated with female group size. Once females departed for foraging, harem males remained in their respective tents at night-time between intermittent foraging bouts and engaged in tent maintenance and tent guarding. Time invested by harem male bats in tent maintenance and tent guarding were positively and significantly correlated with female group size. Harem males extended their presence in tent by utilizing tents as feeding roosts. Female group size also influenced the emergence time of harem male bats, where males with largest group emerged later than did the smallest group. Likewise, harem male with the smallest group had more time available for foraging than the male with the largest group. Findings of this study suggest that having a larger harem may indeed be costly for the males by reducing their foraging time.

Alternative reproductive tactics, sperm mobility and oxidative stress in Carollia perspicillata (Seba’s short-tailed bat)

In social systems with alternative reproductive tactics, sneakers face a higher level of sperm competition than harem males and hence are predicted to allocate more resources to ejaculates. Antioxidants can protect sperm against oxidative stress, and thus, their allocation to the ejaculate may depend on mating tactic. In this study on the frugivorous bat Carollia perspicillata, we assessed, for harem and sneaker males, four sperm mobility traits, blood and ejaculate markers of the redox balance and the ejaculate to blood ratios of the redox markers. Under higher sperm competition, sneaker males should allocate proportionally more antioxidant resources to the protection of sperm than harem males. In contrast, harem males should favour pre-copulatory functions, which comprise the protection of blood. We found significantly higher sperm velocity and sperm survival in sneakers. There was no correlation between sperm mobility and sperm enzymatic antioxidant activity or ejaculate levels of lipid peroxidation (oxidative damage). Ejaculate levels of lipid peroxidation and sperm survival showed a significantly positive correlation, which could be attributed to the role of reactive oxygen species for sperm capacitation. Harem and sneaker males showed similar levels of redox balance markers in ejaculate and blood. However, harem males showed a higher ratio of oxidized over reduced glutathione in blood, which may indicate higher cellular stress due to higher metabolism. Overall, our findings suggest that sneakers of C. perspicillata compensate for a higher level of sperm competition by higher sperm mobility. In social systems with alternative reproductive tactics, sneakers face higher level of sperm competition than harem males and hence are predicted to allocate more resources to ejaculates. Antioxidants can protect sperm against oxidative stress, and thus, their allocation to the ejaculate may depend on mating tactic. In this study on the frugivorous bat Carollia perspicillata, we found sperm swimming significantly faster and longer in sneaker males compared to harem males. However, traits other than the investigated antioxidant may favour higher sperm mobility. Measured redox pattern in blood of harem males may indicate higher cellular stress due to higher metabolism. Our results provide support to the current sperm competition models at the intraspecific level, which is still debated for internal fertilizers. This study contributes to better understanding the trade-offs and adaptations resulting from alternative reproductive tactics in mammals.

How Pronghorn Females Avoid Inbreeding Depression

AbstractAfter a bottleneck in a closed population of pronghorn (Antilocapra americana), some inbred matings occurred, and we detected significant inbreeding depression. But inbred matings occurred less frequently than would be expected by chance. Pronghorn females chose mates after a sampling period and had complete control of the mating decision. Therefore, to discover the behavioral mechanism by which females avoided mating with close kin, we studied female movements and courtship sequences. When females moved from one harem to another in the sampling process, they did not shift to harem males of lower coancestry as they approached estrus. Rather, females progressed more slowly through the later courtship stages when the harem male was related vs. unrelated. Also, the rates of male courtship acts were higher within unrelated vs. related pairs. Some females appeared to use multiple mating as an inbreeding avoidance strategy. Our results suggested that inbreeding avoidance by female pronghorn occurred primarily by reactions to the late stages of male courtship, rather than by spatial avoidance of related males.

Alternative reproductive tactics and reproductive success in male Carollia perspicillata (Seba's short-tailed bat).

The use of alternative reproductive tactics (ARTs) is widespread in animals. Males of some species may change tactics depending on age, body condition and social environment. Many bat species are polygynous where a fraction of males only have access to fertile females. For polygynous bats, knowledge of the reproductive success of males using different ARTs is scarce, and it remains unclear how age of males is related to switching decisions between social statuses. We studied a large captive population of Carollia perspicillata, where males are either harem holders, bachelors or peripheral males. Using a multistate procedure, we modelled the age-related switches in reproductive tactics and in survival probability. From the model, we calculated the reproductive success and the frequencies of males displaying different reproductive tactics. As in mammals, the switch between social statuses is often related to age, we predicted that the transition probability of bachelor and peripheral males to harem status would increase with age. We show, however, that social status transition towards a harem holding position was not related to age. Reproductive success changed with age and social status. Harem males had a significantly higher reproductive success than bachelor males except between a short period from 3.8 to 4.4years of age where success was similar, and a significantly higher reproductive success than peripheral males between 2.6 and 4.4years of age. Harem males showed a clear decrease in the probability of maintaining social status with age, which suggests that senescence reduces resource holding potential.

Modification of sperm quality after sexual abstinence in Seba's short-tailed bat, Carollia perspicillata.

In polygynous mating systems, few males have stable access to sexual mates. With an expected higher copulation rate, harem males may deplete seminal fluids or increase epididymal sperm maturation, generating poor sperm quality. In a first study, we reported a higher sperm quality in sneaker males of Carollia perspicillata To test whether the lower sperm quality observed in harem males was generated by an elevated copulation rate, we temporarily removed males of both social statuses from the colony. We thus assessed status-related changes of sperm quality resulting from sexual abstinence. Moreover, released from territory and female guarding, harem males were expected to show a reduction in somatic costs. On the basis of sperm competition models, we predicted a higher resource investment in the ejaculate with the reduction of pre-copulatory efforts. In line with our predictions, sperm quality of harem males improved significantly in contrast to sneaker males, whose sperm quality did not change. Without an increase in ejaculate lipid peroxidation, our results also provide evidence that the duration of sexual abstinence was not sufficient to generate sperm oxidative damage through senescence. Harem males did not show a reduction in blood lipid peroxidation or in the ratio of oxidized to reduced glutathione. In line with the maintenance of these somatic costs, harem males did not invest more superoxide dismutase to the ejaculate to maintain sperm quality. Our results suggest that a difference in copulation rate rather than an adaptation to sperm competition provides sneaker males with higher sperm quality in C. perspicillata.

Social familiarity affects Diana monkey (Cercopithecus diana diana) alarm call responses in habitat-specific ways.

Male Diana monkeys produce loud and acoustically distinct alarm calls to leopards and eagles that propagate over long distances, much beyond the immediate group. Calling is often contagious, with neighbouring males responding to each other’s calls, indicating that harem males communicate both to local group members and distant competitors. Here, we tested whether male Diana monkeys responding to each other’s alarm calls discriminated familiar from unfamiliar callers in two populations in Taï Forest (Ivory Coast) and on Tiwai Island (Sierra Leone). At both sites, we found specific acoustic markers in male alarm call responses that discriminated familiar from unfamiliar callers, but response patterns were site-specific. On Tiwai Island, males responded to familiar males’ eagle alarms with ‘standard’ eagle alarm calls, whereas unfamiliar males triggered acoustically atypical eagle alarms. The opposite was found in Taï Forest where males responded to unfamiliar males’ eagle alarm calls with ‘standard’ eagle alarms, and with atypical eagle alarms to familiar males’ calls. Moreover, only Taï, but not Tiwai, males also marked familiarity with the caller in their leopard-induced alarms. We concluded that male Diana monkeys encode not only predator type but also signaller familiarity in their alarm calls, although in population-specific ways. We explain these inter-site differences in vocal behaviour in terms of differences in predation pressure and population density. We discuss the adaptive function and implications of this behaviour for the origins of acoustic flexibility in primate communication.

Sneaker males are not necessarily similar to females in colour in a sexually monochromatic cichlid

In species with alternative reproductive tactics (ARTs), males employing different tactics usually have different appearance. The clearest difference is body size: bourgeois males that monopolize access to females are larger than sneaker males that steal fertilizations from them. Sneakers are also known to be often dull in colour compared with bourgeois males and rather resemble females. However, this typical colour pattern is unlikely in the Lake Tanganyika cichlid Neolamprologus mondabu: we observed sneaking by two distinctive colour morphs, namely, black (which is apparently conspicuous against the background) and white (which is apparently background-matching). Because breeding females are black, this observation indicates that one type of sneakers contrasts female appearance. In this study, we conducted field studies to determine the expression of body colour in relation to ARTs in this fish. Body colour was dependent on size, but not sex and maturation, with black individuals being larger than white ones. Together with the presence of intermediate grey colour expressed by intermediate-sized individuals, this fish could ontogenetically changes their body colour from white to black. Both sexes of black individuals occupied feeding territories, but white individuals were non-territorial, indicating that the black body signals the possession of a feeding territory. Sexually active females were invariably black, whereas sexually active males were both black and white in colour. Few of the largest black males held harems, which included several female territories, whereas the remaining males were bachelors with no female territories. These bachelor males invested more in testes than harem males, suggesting that bachelors employ sneaking tactics, which is corroborated by our sneaking observations. To our knowledge, this is the first study showing that sneakers are entirely dissimilar to females in appearance. Herein, we discuss why sneakers are dichromatic in relation to their life histories.

Male courtship displays and vocal communication in the polygynous bat Carollia perspicillata

Male courtship behaviour towards choosy females often comprises elaborate displays that address multiple sensory channels. In bats, detailed quantitative descriptions of multimodal courtship displays are still fairly scarce, despite the taxon’s speciose nature. We studied male courtship behaviour in a polygynous Neotropical bat, Seba’s short-tailed fruit bat Carollia perspicillata, by monitoring harem males in a captive colony. Courting male C. perspicillata performed stereotypic tactile, visual and acoustic displays. A courtship sequence, directed at one female at a time, lasted up to 120 s. During courtship, males approached females by brachiating or flying, hovered in front of them, pursued them on the wing, sniffed them and repeatedly poked the females with one or both folded wings; the latter behaviour was the most conspicuous male courtship display. Immediately before copulation, males wrapped their wings around the females and bit their necks. As acoustic display, courting male C. perspicillata produced highly variable, monosyllabic courtship trills. The species’ vocal repertoire consisted of ten different social vocalisation types, three for benign interactions (courtship trills, wobbles, isolation calls), four for aggressive encounters (aggressive trills, down-sweeps, warbles, distress calls) and the remaining three for unknown behavioural contexts (V-shaped calls, flat down-sweeps, hooks). Courtship trills and aggressive trills were exclusively produced by males. We measured 245 courtship trills of five males and found statistical evidence for a strong individual signature which has the potential to facilitate female choice, mate recognition or neighbour–stranger recognition among male competitors.

Mother–offspring recognition in the bat Carollia perspicillata

Parental care is crucial for offspring survival in many taxa but its burden and costs are often not equally distributed between the sexes. In bats, the majority of parental care is provided by females, making examples of paternal support towards pups exceedingly rare. One exception to this general pattern seemed to be the polygynous Seba's short-tailed fruit bat Carollia perspicillata; two earlier studies suggested that paternal care occurs, i.e. that harem males prompt females to retrieve vocalizing pups. To corroborate this suggestion, we investigated the occurrence of maternal and paternal care in reaction to pup isolation calls in C. perspicillata. Acoustic measurements of 905 isolation calls from 17 pups revealed sufficient interindividual variation to encode an individual vocal signature. Correspondingly, mothers were capable of using this individual signature to discriminate between their own pups and age-matched pups from other females belonging to their colony. Maternal experience was positively correlated with the strength of response behaviour during playbacks. Thus, our results indicate that pup isolation calls were used to elicit maternal care and that mothers recognize their pups based on an individual signature in isolation calls. However, in contrast to the previous studies mentioned above, we found no evidence that harem males reacted to pup isolation calls by prompting the respective mothers to retrieve their vocalizing pups. Instead, our results demonstrate that harem males engaged in courtship activities that were unaffected by pup isolation calls.

Male greater sac-winged bats gain direct fitness benefits when roosting in multimale colonies

Social groups that are characterized by the presence of male kin are rare in mammals. Theory predicts that males reproducing in such groups need to overcome the costs of local mate competition, which are supposedly severe in polygynous or promiscuous mating systems. Here, we studied in a polygynous mammal with male philopatry whether male group size renders direct fitness benefits for males that could outweigh the costs of competing with related males for access to territories and mates. We used long-term behavioral observations and genetic data of the greater sac-winged bat to investigate the factors affecting lifetime breeding success (LBS) of harem males living in colonies that contain varying numbers of male residents. We show that tenure of harem males increased with the number of male coresidents and that harem male tenure explained a large proportion of variation in their LBS. Thus, our results provide evidence that males gain direct fitness benefits from a social organization in colonies that include additional harem territories and nonharem males. Immigration of males into colonies was significantly lower when nonharem males (young males that are often related to harem males) were permanently present in colonies, suggesting that larger male groups may be better able to maintain a patriline in a colony and thus also ensure future indirect fitness benefits. Key words: female-biased dispersal, lifetime breeding success, male tenure, Saccopteryx bilineata, social organization. [Behav Ecol]

Differences in plasma testosterone levels related to social status are more pronounced during mating than nonmating season in the tropical bat Saccopteryx bilineata (greater sac-winged bat)

Testosterone (T) concentrations often covary strongly with mating activities in temperate-zone vertebrates. Recent studies suggest that males of tropical species experience lower and year-round constant T levels. Here we studied plasma T concentrations in a tropical mammal with a seasonally invariant social system, the greater sac-winged bat ( Saccopteryx bilineata (Temminck, 1838)). Colony composition remains almost stable throughout the year, although mating is restricted to only a few weeks each year. Males follow one of two mating strategies: they either defend a territory with a female group (harem) or live peripheral without females. First, we compared T within the same individuals between seasons, asking whether T levels are higher during mating season. Second, we tested whether T levels are related to social status, and third, whether T correlates with parasite infection because of an immunosuppressive effect. We found high individual T variations. Testosterone was elevated during the mating season only in harem males and was, on average, higher than in peripheral males. We found no correlation between T and parasite infestation. Although reproduction is seasonal in S. bilineata, T concentrations showed no pronounced seasonal pattern, probably because colony members form long-term relationships and live in a year-round stable social system.

Intracolonial social distance, signaling modality and association choice in the greater sac-winged bat (Saccopteryx bilineata)

Understanding patterns and motivations for social spacing greatly illuminates the structure and internal dynamics of given groups or social systems. The highly social, polygynous greater sac-winged bat, Saccopteryx bilineata, represents an excellent model for social spacing analysis, since the choice of individual roost-sites within a day-roost constitutes an enduring, often repeated decision about relative proximity to conspecifics. Day-roost colonies consist of one or multiple harem groups, each with several females and a single male. Additionally, non-harem males without females may be present. A social-distance–time-budget metric revealed that harem males, females, and non-harem males differed significantly in their respective spatial associations while roosting. Harem males and females were most closely associated, with harem males located at the center of harems instead of at the borders. Non-harem males associated significantly closer with one another than with harem females that they were trying to access. The signaling modality mediating social interactions depended on the respective social distances between communicating bats. Our results suggest a concentric social organization based around harem males, which may select roost sites in closest possible proximity to females to enhance courtship signal strength. This constitutes an interesting deviation from the normative form of harem maintenance, patrolling borders, in mammals.

Molecular genetic perspective of group-living in a polygynous fruit bat, Cynopterus sphinx

In this study, we investigated the genetic social structure of a polygynous fruit bat, Cynopterus sphinx. We tested whether colonies of C. sphinx are substructured and if genetic relatedness among group members is non-random. Although we did not find statistical evidence of genetic structuring of harems within a colony, significant levels of inbreeding within colonies and social associations between related individuals were observed. The average pairwise relatedness was higher for females within a harem (average: 0.02) than within the colony (average: −0.03) ( p < 0.005). In most harems, the harem male was highly related to one harem female (with an average relatedness of 0.2). Further, statistical resampling suggested that this association is non-random, potentially suggesting mate selection. Although the average relatedness among males in colonies was zero, the range of relatedness (−0.43 to 0.49) was high. We conclude that colonies, to some extent are inbred units, comprising of both related and unrelated individuals, and that social associations might be kin based.

Duration of courtship displays corresponds to social status in male greater sac-winged bats (Saccopteryx bilineata)

In species with complex courtship displays, male courtship performance is often used by females to assess male quality. The greater sac-winged bat ( Saccopteryx bilineata (Temminck, 1838)) lives in a harem-based resource-defence polygyny. Courting males perform complex hover displays in front of roosting females. Males differ in their social status by having females permanently or sporadically in their day-roost territory (harem males vs. nonharem males). We compared the frequency and duration of hover displays from harem and nonharem males in free-living colonies. Male social status was correlated with male age and the number of females being courted; thus, these two effects were removed to compare the frequency and duration of hover displays for harem and nonharem males. The frequency of hover displays per hour did not differ between harem and nonharem males, whereas the mean duration of hover displays was linked to male social status, with harem males exhibiting significantly longer hover displays than nonharem males. When analysing each social status separately, the hover display duration of both harem and nonharem males was neither influenced by the number of competing males nor by the number of females being courted. Male age did not influence the hover display duration of nonharem males; however, it had a significant effect on the hover display duration of harem males, with older harem males hovering significantly longer than younger harem males. Because females are free to choose in which male territory to roost, they might use the duration of hover displays to evaluate the quality of courting males.

Temporal and Spatial Distribution of Male Scent Marks in the Polygynous Greater Sac-Winged Bat

Scent marks are relatively long-lived signals that can be perceived by conspecifics when the producer is absent. Therefore, it is often not obvious to whom the signal is directed. In daytime roosts of the polygynous greater sac-winged bat, males scent mark territories with facial gland secretions. Territories are a valuable resource for males, as they offer exclusive courtship opportunities, which results in increased male reproductive success and, consequently, increased male-male competition over territories. The information encoded in male scent marks could, therefore, be either directed at females as part of an olfactory courtship display or at male competitors as part of territorial behaviour. We expected territorial males to scent mark in the morning, shortly before females return to the territory and close to female roosting sites, if scent marks are directed at females as part of the courtship display. And we expected harem males to scent mark at the territory boundaries, where male-male encounters are most likely to occur, if scent marks are directed at male competitors. We found that males marked more frequently in the afternoon, at a time when all females have already left the territory, and harem males marked at the territory boundaries and not inside their territory in the area where females roost. At boundaries males fan volatiles from specialised wing sacs towards competitors outside the territory. Scent marking of male Saccopteryx bilineata might therefore be congruent with the assessment-hypothesis, which states that scent marks offer intruders the possibility to make an olfactory assessment of the territory owner without direct physical interaction. Thus, scent marks of male S. bilineata are most likely influenced by male-male competition and not by female choice.

Growth acceleration, behaviour and otolith check marks associated with sex change in the wrasse Halichoeres miniatus

In protogynous sex-changing fishes, females are expected to compete for the opportunity to change sex following the loss of a dominant male and may exhibit growth and behavioural traits that help them maintain their dominant status after sex change. A male removal experiment was used to examine changes in female growth and behaviour associated with sex change in the haremic wrasse Halichoeres miniatus and to test whether any changes in growth associated with sex change were recorded in otolith microstructure. Dominant females began displaying male-characteristic behaviour almost immediately after the harem male was removed. The frequency of interactions between females increased following male removal. In contrast, feeding frequency of females decreased. The largest one to three females in each social group changed sex following male removal and exhibited an increase in growth associated with sex change. Sex changers grew more than twice as fast as non-sex changers during the experimental period. This growth acceleration may enable new sex-changed males to rapidly reach a size where they can defend the remaining harem from other males. An optical discontinuity (check mark) was present in the otoliths of sex-changed fish, and otolith accretion rate increased significantly after the check mark, corresponding with the increased growth rate of sex-changing females. Wild caught males, but not females, exhibited an analogous check mark in their otoliths and similar increases in otolith increment widths after the check. This indicates that an increase in growth rate is a regular feature of sex-change dynamics of H. miniatus.