Predation risk and the opportunity for female mate choice in a coral reef fish

The influence of predation risk on the opportunity for female mate choice was investigated in the tailspot wrasse Halichoeres melanurus at two sites on a coral reef in Okinawa, Japan. Females mated repeatedly with the nearest males, but they also changed mates frequently at both sites. Mate changes were seen not only in the context of spatiosocial changes (mate disappearance or shifts in male territories) but were also probably the result of actual mate choice by females. Females at one site (site A) changed mates more often and conducted longer spawning trips from their home ranges to male territories than at the other site (site B). Fish at site A were faced with a higher frequency of predators than that of site B. However, fish of site A suffered fewer attacks from predators because they had more shelter, suggesting lower predation risk in that site. These results suggest that females under higher predation risk had less opportunity to choose preferable mates and that they had to mate with the same, nearest males in most cases.     

Preliminary study on female choice of mates versus sites in a wrasse, Cirrhilabrus temminckii

Female choice of mates versus sites was studied in a wrasse, Cirrhilabrus temminckii. Males had territories within a restricted area on a rocky slope at which females visited and pair-spawned pelagic gametes. Females visited several males or territories before spawning, suggesting the opportunity of female choice. Of the four characteristics of territorial males examined—body size, ratio of pelvic fin length to body size, courtship, frequency and territory depth—only territory depth was significantly correlated with daily mating success of males. The former three male characters were not related to territory depth. These results suggest that female C. temminckii chooses deep sites rather than specific mates in mating.     

Female–female aggression is linked to food defence in a poison frog

Habitat occupancy by territorial animals is expected to depend on the distribution of critical resources. Knowledge on female territoriality is scarce, but it has been suggested as a mechanism to defend limited resources for reproduction. A previous study showed female intrasexual aggression to be associated with territorial behaviour in the strawberry poison frog Oophaga pumilio, a diurnal aposematic species with complex maternal care. Here, we investigate the link between spatial distribution of resources important for reproduction and female distribution and behaviour. We observed focal females in their natural habitat in Costa Rica, and recorded the distribution of ecological predictor variables in a grid system. We used the data for calculating home range and territory sizes and for connecting female habitat use to the distribution of potential resources by computing spatial habitat occupancy models. Even though we found females to occupy large home ranges, they were highly aggressive towards other females only inside a small part of their home range, here termed core area. Among the ecological factors, the sustained abundance of ants (main food item of the frogs), the presence of leaf litter and suitable rearing sites for tadpoles predicted female site occupancy patterns. The number of ants per grid was twice as high in the core areas compared to the rest of the female home ranges. Our results suggest that female spacing behaviour is principally driven by the spatial distribution of its main food resource, but that hiding places (leaf litter) and tadpole‐rearing sites also play a role. The defence of areas with sustainably high abundance of ants could be relevant, as egg production and maternal care are energetically highly demanding in this prolonged‐breeding species. Regarding the link between resource defence and maternal care, the reproductive strategy of female strawberry poison frogs resembles that of the females of small mammals comprising same‐sex competition for food and high investment in producing and rearing young.     

Environmental determinants of butterflyfish social systems

Synopsis Butterflyfishes (Chaetodontidae) display a variety of social systems, including monogamous pair-bonds, harems, and schooling with group spawning. The range of reproductive options available to butterflyfishes is shaped by their general life history characteristics, such as broadcast spawning with widely dispersed pelagic larvae, large body size and low adult mortality. The distribution and quality of food resources are major determinants of group size and mobility, thereby influencing the relative costs and benefits of available options, and determining specific social systems. Planktivorous and corallivorous butterflyfishes exemplify the relationship between food resources and social systems. Pelagic plankton is a patchy, but temporally and spatially unpredictable food resource which is efficiently exploited by fish in mobile schools. Neither sex is able to monopolize food resources necessary for the other sex, and plantivorous butterflyfishes appear constrained to spawn in groups. In contrast, corals are stable and predictable in space and time, favoring residence in one area and territorial defense of that space by coral-feeding butterflyfishes. Females defend food resources from other females, and males defend territories containing a female from other males. Males attempt to defend areas containing more than one female, but are unsuccessful. A monogamous social system results. This system favors the evolution of cooperative behavior between mates to increase female fecundity, as long as the male has an opportunity of sharing in that reproduction. Mate removal experiments conducted on two monogamous coral-feeding species,Chaetodon multicinctus andChaetodon quadrimaculatus reveal a division of labor between male and female pair-mates. Paired males assume most of the territorial defense activities, allowing their mates to feed more.     

Mate acquisition tactics in polyandrous spotted sandpipers (Actitis macularia): the role of age and experience

We consider resource-defense polyandry and mate-access polyandryas female mating tactics in spotted sandpipers (Actitis macularia).These tactics can be distinguished by the resource females defend,female interclutch movement, expected reproductive success aftermoving, and male and female dispersion. We examine these characteristicsrelative to patterns observed in a 17-year study of spottedsandpipers, a species traditionally considered resource-defensepolyandrous. On average, 26% of spotted sandpiper females eachyear were monogamous. Older females were more likely to be polyandrous,and polyandrous females of each age employed different matingtactics. Yearlings were typically sequentially resourcedefensepolyandrous. Two-year-olds were primarily simultaneously polyandrous,exhibiting equivalent proportions of resource-defense and mate-accesspolyandry. Older females were primarily simultaneously resource-defensepolyandrous. Females tended to stay on territories where theyand/or their mates had greater breeding experience (i.e., manyclutches laid for females, many clutches diat hatched for males);females that moved went to territories where their mates hada history of breeding success. Location changes between clutchesby polyandrous females were better described by breeding experienceon a territory than by age.     

Female defense polygyny in the territorial triggerfish <Emphasis Type="Italic">Sufflamen chrysopterum</Emphasis>

The occurrence of polygyny requires specific environmental conditions such as female aggregation or patchy resource distribution. However, it is difficult to determine the factors responsible for polygyny in species in which the territories of both sexes overlap. To overcome this, we performed female removal experiments in the polygynous triggerfish Sufflamen chrysopterum (Balistidae) in the Okinawa coral reef. Both sexes defended their territories exclusively against consexuals of the same species, and female aggregation was absent. Each male territory included 1–3 female territories, and nonterritorial males were significantly smaller than territorial males. Further, the body size of territorial males was positively correlated with that of the largest female in their territories, and larger males tended to mate with more females. The results of the female removal experiments (n = 10 females) indicated that females competed for better territories rather than larger mates. In contrast, males abandoned the territories once the females emigrated. These results strongly suggest that males defend females rather than sites and compete for larger and a greater numbers of females. Thus, in S. chrysopterum, female defense polygyny occurs in the absence of female aggregation.     

Male dominance determines female egg laying rate in crickets

A key prediction of theories of differential allocation and sexual conflict is that male phenotype will affect resource allocation by females. Females may adaptively increase investment in offspring when mated to high quality males to enhance the quality of their offspring, or males may vary in their ability to manipulate female investment post-mating. Males are known to be able to influence female reproductive investment, but the male traits underlying this ability have been little studied in taxa other than birds. We investigated the relationship between male dominance and female oviposition rate in two separate experiments using the field cricket, Gryllus bimaculatus. In both experiments, females mated to more dominant (but not larger) males laid more eggs. This reveals that either females allocate more effort to reproduction after mating with a dominant male or that dominance status is associated with male ability to manipulate their mates. This is the first evidence that dominance, rather than male attractiveness, has a post-copulatory effect on reproductive investment by females.     

Spawning dynamics of orange roughy,Hoplostethus atlanticus,in mid-slope waters of New Zealand

Synopsis The social and reproductive biology of the sand tilefish,Malacanthus plumieri (Malacanthidae), was studied at Glover's Reef, Belize, where this species occurs in colonies over sand-rubble flats. Individuals each occupy a home burrow refuge and a surrounding home range. Home range overlap among adjacent fish of the same sex is low, and individuals defend exclusive use of much of their home range against all conspecifics except mates (i.e., territoriality). Areas defended by males overlap the territories of up to 6 females; and male territory area is positively related to the number of female residents. Males maintain dominance over females within their territories by aggression, including intervention into some female disputes. Females spawn pelagically-dispersed eggs as frequently as every day. Each female spawns near her burrow, almost exclusively with the male whose defended area encompasses her territory (harem polygyny). Tilefish colonies therefore consist of a mosaic of female territories over which adjacent male territories are superimposed. Histological evidence and observation of behavioral sex change in one female revealed thatM. plumieri is capable of protogynous sex reversal. Females did not change sex in response to removal of one male. Occurrence of small transitional fish indicates that the onset of sex change is controlled by factors other than size-related social hierarchies within harems or colonies.     

Access to mates in a territorial ungulate is determined by the size of a male's territory, but not by its habitat quality

1. Territoriality is commonly associated with resource defence polygyny, where males are expected to gain access to females by anticipating how resources will influence female distribution and competing for resource-rich sites to establish their zone of dominance. 2. We tested this hypothesis in European roe deer (Capreolus capreolus) by simultaneously assessing the influence of resources on female distribution and the influence of female distribution on male distribution and breeding success using paternity analyses. 3. Females did not fully distribute themselves among male territories in relation to resources. As a result, relative female abundance in a male's territory depended on territory size, but not on its habitat quality. In turn, relative female abundance in a male's territory determined, at least partially, his breeding success. 4. Interestingly, male territory size, and hence access to females, was partly determined by male body mass (all males) and by residual antler size (subadults only). The latter result suggests that large antlers may be important to young males for establishing their first territory, which is then usually retained for all subsequent reproductive seasons. 5. To conclude, although territoriality of male roe deer has certainly evolved as a tactic for ensuring access to mates, our results suggest that it does not really conform to a conventional resource defence polygyny strategy, as males seem to gain no obvious benefit from defending a territory in an area of high habitat quality in terms of enhanced access to mates. 6. This may explain the stability of male territories between years, suggesting that male territoriality conforms to an 'always stay' and 'low risk-low gain' mating strategy in roe deer.     

Male foraging avoidance in female feeding territories in a harem polygynous cichlid in Lake Tanganyika

We studied foraging site partitioning between the sexes in Neolamprologus tetracanthus, a shrimp-eating Tanganyikan cichlid with harem-polygyny. Females maintained small territories against heterospecific food competitors within large territories of males, foraging exclusively at the inner side of their own territories (foraging areas). Males fed as frequently as females in their own territories, but mostly outside female foraging areas, although they frequently entered female territories and repelled food competitors from the territories. Soon after removal of the resident females, however, harem males, as well as many food competitors, invaded the vacant territories and intensively devoured prey of female foraging areas. This indicates that although female foraging areas appear to contain more food than outside the areas, harem males refrained from foraging there when the resident females were present. We suggest that harem males will attempt to keep female foraging areas in good condition, whereby they may get females to reside in male territories and/or promote female gonadal maturation.     

Population differences in female resource abundance, adult sex ratio, and male mating success in Dendrobates pumilio

In this study I examined the relationship among abundance ofreproductive resources, population density, and adult sex ratioin the strawberry dart-poison frog, Dendrobates pumilio, andhow these variables in turn influence the mating system, malereproductive success, and sexual selection. I studied the matingbehavior in two populations of D. pumilio living in a primaryand secondary rainforest on the Caribbean slope of Costa Rica.The abundance of tadpole-rearing sites (reproductive resourcesfor females) was approximately 10-fold higher in the secondary forest. Accordingly, the population density was higher and theadult sex ratio was strongly female biased in the secondaryforest, whereas the adult sex ratio was even in the primaryforest. The female-biased sex ratio was associated with a higherlevel of polygyny and higher male mating and reproductive successin the secondary forest. In contrast, the level of polyandrydid not differ between habitats. As expected, the opportunityfor sexual selection on male mating success was lower in thesecondary forest, the habitat with high female density. Inconclusion, my results suggest that ecological variables suchas resource availability have a great impact on the matingsystem and sexual selection through their effect on population structure. Moreover, the results of this study give furtherevidence that the opportunity for sexual selection is influencedby the adult sex ratio and hence by the operational sex ratioin a population.     

Female mate choice in the carpenter bee Xylocopa varipuncta (Hymenoptera: Anthophoridae)

Females of the carpenter bee Xylocopa (Neoxylocopa) varipuncta Patton exhibit highly active mate choice. During the spring in central Arizona, males of this species hover at shrubs and trees on or near ridgelines in late afternoons. Occasionally, females fly to and closely approach pheromone-releasing males on their territories, but in 65 of 85 approaches the female left without copulating. Some females visited several males in a few minutes. Copulation only occurred when the female landed on a spot that the resident male rubbed with his body upon the female's arrival. Males did not attempt to disrupt courtship or copulation by other males. In 1988 one creosote bush proved especially attractive to males, as measured by the frequency with which the site was occupied simultaneously by more than one male. The majority of close approaches by females occurred in this one bush. Simultaneous occupation of hovering sites was very rare in 1989. In this year, there was a weak but significant correlation between the frequency with which different sites were visited by intruder males and by females. These results support the hypothesis that males are able to identify locations most likely to attract potential mates.     

The evolution of the mating system of the Carpenter bee Xylocopa varipuncta(Hymenoptera: Anthophoridae)

The Carpenter bee, Xylocopa varipuncta , appears to have evolved a dispersed lek mating system. Males leave the natal nest in the late afternoon in March and April to hover for periods of up to two hours in the crowns of non-flowering trees growing in desert washes. Females and other males occasionally visit a hovering male, probably drawn by a sex pheromone. Resident males repel intruders of the same sex and attempt to induce females to alight on foliage, where mating occurs. The hovering territories do not contain nests, or potential nest sites, or food resources for females. Lek territoriality may have evolved in this species because nests are difficult to locate and the food-plants are evenly dispersed over a large area, making economical defence of patches of this resource unfeasible. Males are left with the option of demonstrating social dominance to potential mates through control of a superior landmark territory.     

Social relationships of immigrant and resident female mountain gorillas. I. Male-female relationships

Adult males are important social partners for all females in mountain gorilla social groups, but male-female relationships can vary in association with variation in female residence status, male age and mating status, and relatedness. Such variation occurred in a large group observed over a 3-year period. All females associated and interacted affiliatively relatively often with a young silverback with whom all mated. Long-term resident females also did so with an old, non-breeding male to whom most were related, but recent immigrants spent little time near him and had few non-aggressive interactions with him. The old male made agonistic interventions to support relatives; interventions in female conflicts by the younger male tended to ameliorate competitive differentials that immigrants faced and may have helped him to retain them as mates. Males aggression toward females was common, most probably served as a mating tactic, and did not involve resource competition. Extensive grooming by an adolescent male suggests that males may also use affiliative behavior to develop mating relationships. Females may have competed for proximity with and social access to the younger silverback; competitive success could influence how well females and their offspring are protected by silver-backs, but the extent of such competition was not clear. Large group size may have heightened differentiation of male-female relationships and competition among females, but comparative data from smaller groups generally corroborate the findings from the large group. © 1992 Wiley-Liss, Inc.     

The social and mating system of the maternal mouthbrooderTropheus moorii (Cichlidae) in Lake Tanganyika

Territorial behaviour, reproduction and migration of the epilithic algal eater,Tropheus moorii, were investigated in Lake Tanganyika, Africa. Adults of both sexes had individual feeding territories which adjointed each other. Males, who occupied higher rocks than females, usually stayed at the same sites for more than 5 months. Females left their territories to pair with males in the males’ territories. Paired females actively foraged under the protection of their mates for up to 3 weeks prior to spawning. After spawning, females usually settled in a site unoccupied by territory-holders to mouthbrood the offspring for a month. An examination of the ovaries and a removal experiment of dominant males suggest that females cannot attain fully mature ovaries in their own territories and choose males whose territories can provide enough food to satisfy their nutritive demand. The evolution of a number of local colour morphs in this fish is briefly discussed in relation to social selection.     

Spatial organization of the North Island Brown Kiwi Apteryx australis mantelli: sex, pairing status and territoriality

In Waitangi State Forest, 51 North Island Brown Kiwi Apteryx australis mantelli were tagged with radio transmitters and observed for an average of 2.3 months. All females and the majority of males were paired and maintained territories of 6.7 and 5.5 ha, respectively. Territories overlapped widely between partners but only narrowly with those of paired neighbours. Unpaired males had territories of 12.8 ha and extensively overlapped those of paired males. Territories were maintained by long distance calls and rare aggressive encounters. Males were more territorial than females. Within pairs, males called 1.5 times more often than females and initiated most pair calls. 60% of female calls were responses to their mates. Observers could often induce aggressive behaviour (calling, fast approach) in male kiwi (by playback, for example) but hardly ever in females. Kiwi territoriality cannot be explained by the distribution and availability of food and shelter sites, but seems to serve mainly a reproductive function.     

Lekking and the small-scale distribution of the sexes in the Caribbean fruit fly,Anastrepha suspensa (Loew)

Male and female Anastrepha suspensa(Loew) had a clumped distribution in the foliage of their guava host plants. Males were no closer to other males than they were to females or than females were to other females. Flies were often found in roughly the same locations over time. However, contemporaries (flies present at the same time) were closer to each other than subsequent flies were to their predecessors. Males were more likely to be found near spots previously occupied by males than they were to spots used previously by females. Some trees had more flies than others, but there was no regional (northwest, etc.) preference within trees. Females were no more likely to be found in the vicinity of clumped (lekking) males than they were by isolated males. About a third of the females taken from inside leks had sperm in their spermathecae, and it is not clear if their motive for being in these areas was sexual. In pairs of males (within 15 cm of each other), the larger fly tends to be in a position farther up the branch, suggesting that larger males may control preferred territories. It seems possible that males attempting to intercept females accumulate in favorable microhabitats where females are likely to be concentrated and that leks have evolved from such clumping.     

Loss of preferred mates forces female satin bowerbirds (Ptilonorhynchus violaceus) to increase mate searching

Variation in mate choice among females can have important consequences for the operation of sexual selection, and can result from differences in the way females search for mates. Our previous work indicates that female satin bowerbirds Ptilonorhynchus violaceus alter their mate-searching patterns according to long-term experience. Females which mate with very attractive males mate with the same males in the following year, thereby reducing their search. In contrast, females which fail to encounter very attractive males typically reject their previous mates and search for more attractive males in the following year, thereby increasing their search. Here we report results from a natural experiment consistent with these observations. Five males, including the most attractive male of 1997, failed to re-establish display sites in 1998, most probably dying over winter. We monitored the mate-searching behaviour of females which mated with these males in 1997 to determine how the loss of attractive mates affects subsequent mate-searching patterns. Females which lost their mates sampled more males compared with their own search patterns in 1997 and with faithful females in 1998. Results from this natural experiment indicate that the loss of attractive and preferred mates forces females to increase their search and provide evidence that long-term experience with males shapes mate-searching behaviour.     

Mate size and breeding success in a monogamous cichlid fish

Synopsis The patterns of mate size and parental care of a monogamous cichlid fish,Cichlasoma maculicauda, were studied in Gatun Lake, Panama. Males defend territories which serve as courtship and nest sites. Within a population most mates in pairs are of equal size rank. In each pair the male is larger than the female, probably because most mature males are larger than most mature females. Clutch size increases with female body size. Male size affects breeding success in two ways. First, larger males provide nest sites less susceptible to destructive wave action. Second, young of larger males grow faster than young of smaller males. Large males defeat small males in contests for position in feeding areas, and this may provide their young with better feeding conditions. In the laboratory young growth rates increase with food abundance, and at high levels of food surpass those observed in nature. Fast growth of young reduces their vulnerability to predators and should allow parents to breed more often. Young survival rates improve with the size of the parents, so that larger fish raise more offspring at each breeding attempt. These observations suggest why preference for large mates should occur.     

Females prefer mating males in the carmine triplefin,Axoclinus carminalis,a paternal brood-guarder

Synopsis This study investigates the role of male mating status in female choice patterns in the carmine triplefin, Axoclinus carminalis, a tripterygiid fish that exhibits paternal care. The distribution of daily reproductive activity is clumped, with many males receiving no mates and some receiving three or more. Females in this species do not prefer larger males, and characteristics of the oviposition site appear to have minimal effects on male mating success. When a female is removed from a male early in the daily spawning period, that male attracts fewer additional females for the remainder of the spawning period than does a control male. These changes in mating success are temporary, and do not affect mating success on subsequent days. A preference for mating males or males that are guarding eggs could provide asymmetric benefits for males to defend oviposition sites. This preference for males with eggs could be acting alone or with other factors such as high variance in oviposition site quality to favor the evolution of paternal care in fishes.