Unpaired Individuals Research Articles

Winter pairs of ruddy shelducks at Lashihai Lake, southwest China

It has been suggested that pairing behavior during winter in migratory ducks represents a trade-off between costs (defense of the female) and benefits (early access to females). To investigate the benefits and costs for both sexes in wintering pairs of ruddy shelducks (Tadorna ferruginea), we compared time budgets for paired males and females, and surveyed the sex ratio of the birds wintering at Lashihai Lake, southwest China. The behavior of the paired ruddy shelducks was monitored for 5 activity types: feeding, resting (including sleeping), preening, drinking and warning. Feeding was the most dominant activity. The feeding time of both sexes increased as the winter season progressed. However, the paired females always spent significantly more time feeding and less time warning than the paired males. Paired ruddy shelducks had access to better feeding grounds than unpaired individuals, resulting in a food benefit for paired individuals over single individuals. Because the sex ratio of the wintering population was strongly male biased (M:F = 1.44:1.00), the paired male also gained the benefit of accessing a female in advance of the breeding season.

Genetic and environmental influences of white and gray matter signal contrast: A new phenotype for imaging genetics?

The estimation of cortical thickness is in part dependent on the degree of contrast in T1 signal intensity between white matter and gray matter along the cortical mantle. The ratio of white matter to gray matter signal (WM/GM contrast) has been found to vary as a function of age and Alzheimer's disease status, suggesting a biological component to what might otherwise be labeled as a nuisance variable. The aim of the present study was to determine if measures of WM/GM contrast are genetically influenced, as well as the degree to which this phenotype may be related to the genetic and environment determinants of cortical thickness. Participants were 514 male twins (130 monozygotic, 97 dizygotic pairs, and 60 unpaired individuals) from the Vietnam Era Twin Study of Aging. Ages ranged from 51 to 59 years. Measures of WM/GM contrast and cortical thickness were derived for 66 cortical regions of interest (ROI) using FreeSurfer-based methods. Univariate and bivariate twin analyses were used in order to estimate the heritability of WM/GM contrast, as well as the degree of shared genetic and environmental variance between WM/GM contrast and cortical thickness. WM/GM contrast was found to be significantly heritable in the majority of ROIs. The average heritability across individual ROIs was highest in the occipital lobe (.50), and lowest in the cingulate cortex (.24). Significant phenotypic correlations between WM/GM contrast and cortical thickness were observed for most of the ROIs. The majority of the phenotypic correlations were negative, ranging from ?.11 to ?.54. Of the 66 associations, only 17 significant genetic correlations were found, ranging from ?.16 to ?.34, indicating small amounts of shared genetic variance. The majority of the phenotypic correlations were accounted for by small unique environmental effects common between WM/GM contrast and cortical thickness. These findings demonstrate that like cortical thickness, WM/GM contrast is a genetically influenced brain structure phenotype. The lack of significant genetic correlations with cortical thickness suggests that this measure potentially represents a unique source of genetic variance, one that has yet to be explored by the field of imaging genetics.

Physiological implications of pair-bond status in greylag geese

In group-living vertebrates, reliable social allies play a decisive role in dealing with stressors. For example, support by social allies is known to dampen glucocorticoid responses. It remains unknown, however, how social embedding affects the sympatho-adrenergic axis as indicated by heart rate (HR) in non-human animals. We studied the relationships between HR, pair-bond status and distance from the pair-partner in twenty-five free-ranging greylag geese (Anser anser) in a natural social environment. In three individuals, we investigated HR responses following partner loss. Overall, we found a context- and sex-dependent difference in HR between paired and unpaired individuals, paired males having a lower HR during agonistic encounters, and unpaired females having a lower HR during resting. Also, in paired females HR increased with increasing distance from the partner. Our data suggest that HR is modulated by pair-bond status in greylag geese in a context- and sex-dependent manner, which may be representative for social vertebrates in general. Despite the low sample size, the present study indicates that proper social embedding may optimize an individual's physiological investment in the social domain. This reduces individual energy expenditure and may benefit health and reproductive success.

Effect of isolation and conspecific presence in a novel environment on corticosterone concentrations in a social avian species, the zebra finch (Taeniopygia guttata)

Zebra finches are a highly social and monogamous avian species. In the present study, we sought to determine the effect of social isolation (separation from the flock) in a novel environment with and without a conspecific present on the adrenocortical activity of paired and unpaired individuals of this species. With regard to paired birds, we hypothesized that the presence of the mate during isolation from the group would act as a social buffer against the stressful effects of isolation. We observed that 10 but not 30minutes of social isolation resulted in elevated concentrations of corticosterone in unpaired and paired male zebra finches in comparison to baseline concentrations of corticosterone. Furthermore, the presence of a mate during isolation in a novel environment did not have a buffering effect against increases in corticosterone concentrations. Additionally, to compare concentrations of corticosterone in response to isolation (in a novel environment) to a previously well-established stressor, we subjected groups of birds to restraint. We observed that 10 or 30minutes of restraint led to significantly higher concentrations of corticosterone as compared to baseline. Finally, to rule out the possibility that merely handling a bird would result in significantly elevated concentrations of corticosterone as compared to baseline samples, we measured corticosterone concentrations 10 or 30minutes after handling involving capture and release only. Our results suggest that handling alone might have contributed to the elevation of corticosterone in birds exposed to 10minutes but not 30minutes of restraint. Handling by itself did not account, however, for the elevated corticosterone in birds socially isolated for 10minutes.

Constrained mate choice in social monogamy and the stress of having an unattractive partner

In socially monogamous animals, mate choice is constrained by the availability of unpaired individuals in the local population. Here, we experimentally investigate the physiological stress endured by a female (the choosy sex) when pairing with a non-preferred social partner. In two experimental contexts, female Gouldian finches (Erythrura gouldiae) socially paired with poor-quality mates had levels of circulating corticosterone that were three to four times higher than those observed in females that were paired with preferred mates. The elevated level of this stress hormone in response to partner quality was observed within 12 h of the experimental introduction and maintained over a period of several weeks. Our findings demonstrate the extent of intra-individual conflict that occurs when individuals are forced to make mate-choice decisions that are not perfectly aligned with mate-choice preferences. The elevated level of corticosterone also suggests a mechanistic route through which females might adaptively manage their responses to intersexual conflict over reproductive investment.

Transitive inference in free-living greylag geese, Anser anser

Living in large, stable groups is often considered to favour the evolution of cognitive abilities related to social living, such as the ability to track relationships among group members and to make transitive inferences about relationships based on indirect evidence. Greylag geese are relatively small brained, but live in complex societies with social support and clan structures. They form dominance hierarchies in which families dominate pairs and unpaired individuals. However, competition is costly and the ability to transitively infer relationships among flock members may be highly advantageous. We tested five free-living, juvenile greylag geese embedded in a flock of 150 birds for their ability to track multiple dyadic relationships and their transitive inference competence. Individuals were trained on discriminations between successive pairs of five implicitly ordered colours (A–E). All individuals learned to track four dyadic relationships simultaneously and showed transitive inference when presented with nonadjacent colours. Remarkably, the amount of training required was related to the individual’s early social environment. Our study is one of the first to show transitive inference in a precocial bird and suggests an influence of early social experience on sociocognitive abilities. Furthermore, it improves our understanding of social complexity as an important selection pressure for the evolution of cognition.

Social but not genetic monogamy is associated with greater breeding success in prairie voles

Much attention has focused on distinguishing between social and genetic monogamy in avian taxa. However, surprisingly few studies have directly investigated this distinction among mammals. We investigated the genetic mating system of the prairie vole, Microtus ochrogaster, a popular model for mammalian monogamy and human attachment. We used space use patterns to define paired and single animals and assessed paternity using microsatellite loci. Prairie voles in this study engaged in significantly more extrapair fertilizations than predicted under genetic monogamy but fewer than predicted under random mating, demonstrating social but not genetic monogamy. Furthermore, we found that paired individuals were more likely to produce offspring than were unpaired individuals of either sex. This finding was true for both sexes and was attributable to differences in fertilization rates rather than litter sizes. Among mated individuals, however, faithful animals were no more successful than those that mated outside a pair. Taken together, our data demonstrate that paired prairie voles have greater breeding success than single voles, but such success is not contingent on mating exclusively with a social partner. If this species is to serve as a model for human love, our findings emphasize the need to distinguish between mammalian social attachment and sexual fidelity.

농촌 지역의 너구리 Nyctereutes procyonoides 행동권

본 연구의 목적은 농촌지역의 너구리 행동권과 핵심지역의 면적을 분석하는 것으로서, 이를 위해 22개체를 포획하여 원격 무선추적을 실시하였다. 이 중 3개월 이상 무선 추적이 실시된 9개체의 행동권을 분석한 결과 평균 <TEX>$0.80km^2$</TEX> (100% MCP)를 나타내었다. 성별 행동권은 수컷이 평균 <TEX>$0.98km^2$</TEX> (100% MCP)를 나타내었고, 암컷은 평균 <TEX>$0.58km^2$</TEX> (100% MCP)를 나타내어 수컷의 행동권이 넓었다. 그러나 95% MCP (Minimum Convex Polygon)를 적용했을 경우 수컷이 평균 <TEX>$0.63km^2$</TEX>, 암컷이 <TEX>$0.42km^2$</TEX>로서 차이가 많이 줄었다. 또한 암수 쌍이 함께 무선 추적된 두 쌍의 행동권은 95% MCP를 적용했을 경우 암수가 각각 <TEX>$0.26km^2$</TEX>와 <TEX>$0.28km^2$</TEX>로서 차이가 매우 적거나, <TEX>$0.36km^2$</TEX>와 <TEX>$0.36km^2$</TEX>로 통일했으며, 4 계절 모두 짝을 지어 함께 지냈다. 따라서 짝이 없거나 영역이 정해지지 않은 등의 경우를 제외하고 정상적으로 암수가 한 쌍이 되어 지내는 일상의 경우에는 암수의 행동권이 같다고 판단되어진다. 원격 무선 추적된 너구리 중 4 개체는 암수 쌍을 이루고 있었으며, 이들 두 쌍 모두 일부 일처제를 이루고 함께 이동하며 생활하였다. The objectives of this paper are to estimate home range and core habitat area of raccoon dog living in the rural area of Korea. A radio-telemetry study was carried out on 22 raccoon dog individuals. Among these individuals, 4 raccoon dogs made 2 pairs and they were monogamous and moved together all the year round. Mean home-range size of 9 individuals which were radio-tracked more than 3 months was <TEX>$0.80km^2$</TEX> (100% MCP). The mean home range size of male individuals was <TEX>$0.98km^2$</TEX> (N=5, 100% MCP) and that of female individuals was <TEX>$0.58km^2$</TEX> (N=4, 100% MCP). On the other hand, in case 95% MCP(Mininlum Convex Polygon) was applied, the gap of home-range size between sex distinction was closed to <TEX>$0.63km^2$</TEX> (male) and <TEX>$0.42km^2$</TEX> (female). The home range size of two pairs of which the male and the female were radio-tracked at the same time showed little difference. In case of one pair, the home range size(95% MCP) was <TEX>$0.28km^2$</TEX> (male) and <TEX>$0.26km^2$</TEX> (female) and in case of the other pair, it was <TEX>$0.36km^2$</TEX> each (male and female). Consequently there seems no significant difference in the home-range size between a male and a female racoon dog except the unusual cases such as unpaired individuals or the ones with no fixed territory.

Precopulatory mate guarding affects predation risk in two freshwater amphipod species

Contact mate guarding may increase predation risk in the presence of active, size-selective predators by increasing the apparent size or decreasing the escape ability of an individual. These same characteristics may, however, make paired individuals less vulnerable to sit-and-wait, non-size-selective predators. Because the costs and benefits associated with mate guarding are likely to depend on local ecological conditions, species or populations should vary in the duration of the guarding phase. In this study, I investigate whether precopulatory mate guarding increases an individual's predation risk for two freshwater amphipod species within the Hyalella azteca species complex that experience different predators. When larval dragonflies, Anax junius and Tramea lacerata, were used as predators in laboratory trials, single, unpaired individuals were more likely to be consumed than paired individuals. Conversely, predatory fish consumed paired females more often than single females. Therefore, the short precopulatory mate guarding duration observed in the species that co-occurs with predatory fish may be due to habitat-specific, predator-driven costs associated with precopulatory mate guarding. Furthermore, the predation cost associated with precopula was greater for females than males when predatory fish were used as predators, implying that intersexual conflict over the duration of the guarding period may be more intense for the species that co-occurs with predatory fish.

Effects of Habitat Fragmentation on Pairing Success of Ovenbirds: Importance of Male Age and Floater Behavior

AbstractBetween 1996 and 1998, we compared pairing success of territorial male Ovenbirds (Seiurus aurocapillus) in forest fragments created by forestry (n = 3) and agriculture (n = 10) to contiguous forest plots (n = 3) in the southern boreal mixedwood forest of central Saskatchewan. The percentage of Ovenbird males paired per site was lower in fragments created by agriculture (86 ± 3%) and forestry (87 ± 3%) than in contiguous forest (97 ± 3%). At the individual level, second-year males (82%) were less likely to be paired than after-second-year males (94%), whereas males closer to edges were less likely to be paired than those in forest interiors. Although pairing success differed among landscapes, those differences were smaller than reported in studies conducted in eastern North America. The high density of birds in our study area may have resulted in intense intraspecific competition, which could have prevented unpaired individuals from maintaining territories. Removal experiments in 1997 and 1998 demonstrated floaters occurred in contiguous forest, but rarely occurred in fragments created by agriculture. The presence of floaters in contiguous forest suggests the ratio of breeding to nonbreeding males in forest fragments and contiguous forest may be similar, but that the strategy (i.e. floater vs. territorial) used by unpaired birds may differ among landscapes.

Pairing Patterns in Japanese Beetles (Popillia japonica Newman): Effects of Sex Ratio and Time of Day

Size-related patterns between unpaired and paired individuals and between males and females of a given pair give clues about both a species' sexual behavior and the environmental factors affecting its sexual behavior. We studied the mating patterns of Japanese beetles (Popillia japonica) in east–central Illinois. The frequency of male–female pairs varied significantly among days and within a day, with pairs being significantly more common in the morning and the evening. The sex ratio on the food plants was significantly male biased, but although the sex ratio fluctuated among days and among time periods, the variation in the frequency of mating pairs was not explained by variation in the sex ratio. We found no assortative pairing with respect to size, but sizes of paired and unpaired individuals did differ. Paired females were larger than unpaired females at all time periods. In contrast, paired males were larger at 0700 and smaller at 1000, and little difference existed at other times of the day. The size of males and females, sex ratio, and pairing frequency also differed among days. Much of this variation in size and pairing frequency was related to a seasonal effect: later in the summer, beetles of both sexes were smaller and pairs were less common. Interestingly, pairs were also less frequent on days with higher average temperatures. This between-day variation in pairing, in combination with the within-day pairing differences, suggests that the temperature may alter the cost, and hence likelihood, of pairing in this species.

EFFECTS OF HABITAT FRAGMENTATION ON PAIRING SUCCESS OF OVENBIRDS: IMPORTANCE OF MALE AGE AND FLOATER BEHAVIOR

Abstract Between 1996 and 1998, we compared pairing success of territorial male Ovenbirds (Seiurus aurocapillus) in forest fragments created by forestry (n = 3) and agriculture (n = 10) to contiguous forest plots (n = 3) in the southern boreal mixedwood forest of central Saskatchewan. The percentage of Ovenbird males paired per site was lower in fragments created by agriculture (86 ± 3%) and forestry (87 ± 3%) than in contiguous forest (97 ± 3%). At the individual level, second-year males (82%) were less likely to be paired than after-second-year males (94%), whereas males closer to edges were less likely to be paired than those in forest interiors. Although pairing success differed among landscapes, those differences were smaller than reported in studies conducted in eastern North America. The high density of birds in our study area may have resulted in intense intraspecific competition, which could have prevented unpaired individuals from maintaining territories. Removal experiments in 1997 and 1998 dem...

KINSHIP, SOCIAL RELATIONSHIPS, AND DEN SHARING IN KIT FOXES

We used 11 microsatellites, highly variable nuclear markers, to infer kinship among 35 San Joaquin kit foxes,Vulpes macrotis mutica, and combined this information with field observations to gain insight into fox social behavior. Fox social units consisted of solitary foxes, mated male–female pairs, and trios consisting of a mated pair plus another adult. Pair-mates were not closely related. The additional adult (1 male, 1 female) in 2 trios was the offspring of at least 1 of the pair-mates. Foxes living on adjacent home ranges tended to be more closely related than foxes that did not live on adjacent home ranges, largely because females on adjacent home ranges were often closely related. FIS values indicated a deficiency of homozygotes that was likely due to clusters of relatives living on adjacent home ranges. Foxes that shared the same den on the same day were usually members of the same social group. Contrary to expectations, however, we sometimes found foxes sharing dens with foxes from other social groups. Many cases involved unpaired individuals and appeared to be unsuccessful attempts at pair formation. Other cases involved members of 2 adjacent social groups, a pair and a trio. Both members of the pair were closely related to ≥1 member of the trio, indicating that kit foxes can maintain enduring social relationships with adult offspring or siblings that have dispersed to a new home range and found a mate.

The effects of two acanthocephalan parasites, Pomphorhynchus laevis and Polymorphus minutus, on pairing success in male Gammarus pulex (Crustacea: Amphipoda)

Parasites can decrease male mating success in host species in various ways, in particular by affecting male competitive ability for access to females. However, male-male competition can take different forms (i.e. interference vs exploitation competition) and which type of competition is most affected by parasites is not always clear. We investigated the influence of two acanthocephalan parasites Pomphorhynchus laevis and Polymorphus minutus on the pairing success of their intermediate host, Gammarus pulex, using field-based studies and complementary laboratory-based studies. We first studied male pairing success in the field using four large samples of paired and unpaired individuals collected at different dates. In three of the samples, the effects of size and parasite infection were significant, whereas for one sample only male size had a significant effect. There was no difference in size distributions between infected and uninfected gammarids. Large males were paired more often than smaller males, and uninfected males were paired more frequently than infected males, the pairing success of P. minutus-infected males being more severely affected than that of P. laevis-infected males. We then experimentally tested the ability to enter into precopula with a receptive female in the presence or absence of competitors. In competitive situations, the pairing success of P. laevis- and P. minutus-infected males was significantly lower than that of uninfected males, with pairing success being more affected in P. laevis-infected than in P. minutus-infected males. In the absence of competition, males infected with P. laevis were significantly less likely to enter into precopula compared with uninfected males and P. minutus-infected males, whereas there was no difference between uninfected and P. minutus-infected males in their inclination to pair with a receptive female. However, for both parasites, latency time to pair formation was significantly shorter for uninfected than for infected males. In a third experiment, we tested for a potential effect of vertical segregation on the pairing success of infected and uninfected males, but found no evidence for it. We conclude that infected males may be less competitive than uninfected males in competition by exploitation between males for females.

An ESS model for divorce strategies in birds

We present a theoretical investigation of divorce. Arguments are couched in terms of birds, but should be applicable to other groups of organisms. We model a population in which there is a range of both male and female qualities, and decisions on whether to divorce are made by both members of a breeding pair. The reproductive success of a pair is additive in male and female qualities in the baseline case, but we also consider the effect of quality interactions. The availability of new mates depends on the divorce strategy of all population members. We allow for the possibility that mate choice is associative in quality, although we do not explicitly model the mate choice process. Using a game–theoretical model which incorporates these factors we investigate the following issues: the form of the evolutionary stable strategy, and the implications of this strategy for quality correlations in breeding pairs and for the distribution of qualities among unpaired individuals; divorce rates, reproductive success and mate quality changes over the lifetime of an individual, and the dependence of these qualtities on the individual's quality; mean population divorce rates and their dependence on costs of divorce, longevity and the extent of quality variation in the two sexes; initiators of divorce and reproductive success before and after divorce.

Multi-locus DNA fingerprinting supports genetic monogamy in Florida scrub-jays

Extensive behavioural and pedigree data on a colour-marked population of Florida scrub-jays (Aphelocoma coerulescens) suggested that this cooperatively breeding species is monogamous, with extremely rare exceptions in which males have two mates. We used multi-locus DNA fingerprinting to test these observations by determining genetic parentage. Despite restricted dispersal and high relatedness between behavioural parents and non-breeding members of the group, DNA fingerprints provided sufficient variability to determine parentage unambiguously in almost all cases. We found no evidence of extra-pair fertilisation of females or egg dumping, and confirmed a suspected case of polygyny in which a mother and daughter laid and incubated in the same nest. Our results confirm that detailed behavioural data allow accurate assignment of genetic parentage in this species. In Florida scrub-jays, large territory size may limit opportunities for cuckoldry, and persistent intense competition for limited breeding space may lead to low variance in the quality of established male breeders. These factors would reduce both the opportunity for, and benefits of engaging in extra-pair fertilisations. Delayed dispersal and cooperative breeding in this species have not evolved as avenues for direct reproduction by unpaired individuals.

Survival estimation and the effects of dependency among animals

Survival models assume that fates of individuals are independent, yet the robustness of this assumption has been poorly quantified. We examine how empirically derived estimates of the variance of survival rates are affected by dependency in survival probability among individuals. We used Monte Carlo simulations to generate known amounts of dependency among pairs of individuals and analyzed these data with Kaplan-Meier and Cormack-Jolly-Seber models. Dependency significantly increased these empirical variances as compared to theoretically derived estimates of variance from the same populations. Using resighting data from 168 pairs of black brant ( Branta bernicla nigricans ), we used a resampling procedure and program RELEASE to estimate empirical and mean theoretical variances. We estimated that the relationship between paired individuals caused the empirical variance of the survival rate to be 155% larger than the empirical variance for unpaired individuals. Monte Carlo simulations and use of this resampling strategy can provide investigators with information on how robust their data are to this common assumption of independent survival probabilities.

Assortative pairing in Gammarus insensibilis (Amphipoda) infected by a trematode parasite.

We have investigated the influence of Microphallus papillorobustus (Trematoda) on the reproductive biology and mating patterns of its intermediate host Gammarus insensibilis (Amphipoda). Infected Gammarus species show altered behaviour which renders them more susceptible to predation by Charadriiform birds, the parasite's definitive hosts. In a natural population of G. insensibilis, mean parasite intensity was higher for unpaired individuals than for paired individuals. Fecundity was reduced in infected amphipods. Size-assortative pairing was significant, although infected males were found with smaller females compared to uninfected males of the same size. There was also a positive assortative pairing by parasitic prevalence. Vertical segregation between infected and uninfected individuals, male-male competition for access to uninfected females, and female choice may explain assortative mating for prevalence. This study provides the first empirical evidence that parasites can have a direct effect on patterns of mating in gammarids.

Body size and condition, age, plumage quality, and foods of prenesting male cinnamon teal in relation to pair status

Male-biased sex ratios in waterfowl may contribute to sexual selection and permit females to be the deciding sex in mate selection. Male characteristics potentially influencing female choice include male age, size, plumage quality, and body condition (i.e., relative body mass, fat content, or protein content). By examining characteristics of prenesting male cinammon teal (Anas cyanoptera) relative to their pair status we evaluated the predictions that (i) paired males are older and physically superior to unpaired males and (ii) older and physically superior males pair in advance of other males. Diets of paired and unpaired males were similar, as were body size, ingesta-free body mass, fat, breast, and leg muscle protein contents, and testis, liver, and plumage masses. Likewise, pair status was not associated with male age. Body protein content and percentage of alternate plumage were generally greater in paired than unpaired males, but for some unpaired individuals these values were higher than the mean values for paired males. Thus, we found only limited evidence to support the above hypotheses. Our data suggest a possible link between winter nutrition and male participation in reproduction. That is, characteristics which enable males, during winter, to acquire nutrients for initiating and completing the prealternate molt in advance of other males also may be associated with ability to obtain a mate.

Monogamy, spawning and skin-shedding of the sea moth, Eurypegasus draconis (Pisces: Pegasidae)

The Red Sea seamoth, Eurypegasus draconis, has a social structure that involves close pair-bonding with a monogamous mating system. The occurrence of 61 specimens, 95.1% paired, were recorded in the Gulf of Aqaba, during summers 1989 and 1990. Fourteen pairs were tagged and seven of them were seen again at least once. Cumulative location maps for tagged individuals showed that they were not territorial or site-attached, home ranges of pairs overlapped, they had low mobility, and occurred in low densities. Dissections and histological analyses showed that pairs (n = 12) were heterosexual and all individuals were sexually mature. E. draconis is sexually dimorphic. Females (n = 13) have significantly larger carapace volumes than males (n = 13). In aquaria, pairs spawned repetitively at dusk. At the peak of a spawning rise they released pelagic eggs from which embryos hatched in 24–29h at 27.2°C. Unpaired individuals probably have little opportunity to meet and mate. Close pair-bonding that ensures the availability of a mate, probably evolved as a style for increasing reproductive success in these small fish that occur in low density. E. draconis sheds its skin in one piece every 1 to 5 days.