Reproductive behavior in horseshoe crabs:Does density matter?

While the four species of horseshoe crabs share many common reproductive traits with respect to their reproductive systems, they do differ with respect to their mating behavior （monogamy vs. polygynandry）. Past research has attributed these differences to a number of factors including： spawning densities, operational sex ratios （OSR＇s）, male condition （or age）, environmental and/or genetic factors, or a combination thereof. Mating behaviors in the three Asian horseshoe crab species （Tachy-pleus gigas, T. tridentatus, and Carcinoscorpius rotundicauda） with low spawning densities and 1：1 operational sex ratios are typically monogamous. In Limuluspolyphemus, mating behavior is more variable ranging fi＇om monogamy to polygynandry. Here we provide evidence, through a long term behavioral study, that variation in mating behavior is influenced by population density in L. polyphemus. Our study population on two beaches in Connecticut （Long Island Sound） have a spawning density 400 times less than that found in Delaware Bay （0.002 females/m2 vs. 0.8 females/m2） but similar operational sex ratios. Between 90%-95% of all spawning females in CT were paired with only one male, thus exhibiting monogamous behavior. In contrast, between 30 and 60% of spawning females in Delaware Bay have more than one mate and produce clutches of eggs with multiple paternities. Male condition played no role in mating behavior in CT populations. We also observed that on average 18% of the females on the spawning beaches are single. These results suggest that population density is an important condition that determines mating behavior. Also, low population density may lead to decreased mate finding ability and lost opportunities for spawning

The evolution of complex brains and behaviors in African cichlid fishes

In this review, I explore the effects of both social organization and the physical environment, specifically habitat complexity, on the brains and behavior of highly visual African cichlid fishes, drawing on examples from primates and birds where appropriate. In closely related fishes from the monophyletic Ectodinii clade of Lake Tanganyika, both forces influence cichlid brains and behavior. Considering social influences first, visual acuity differs with respect to social organization （monogamy versus polygyny）. Both the telencephalon and amygdalar homologue, area Dm, are larger in monogamous species. Monogamous species are found to have more vasotocin-immunoreactive cells in the preoptic area of the brain. Habitat complexity also influences brain and behavior in these fishes. Total brain size, telencephalic and cerebellar size are positively correlated with habitat complexity. Visual acuity and spatial memory are enhanced in cichlids living in more complex environments. However habitat complexity and social forces affect cichlid brains differently. Taken together, our field data and plasticity data suggest that some of the species-specific neural effects of habitat complexity could be the consequence of the corresponding social correlates. Environmental forces, however, exert a broader effect on brain structures than social ones do, suggesting allometric expansion of the brain structures in concert with brain size and/or co-evolntion of these structures [Current Zoology 56 （1）： 144-156, 2010].

The Babysitter： A Feminist Interpretation

Sexual violence, a prevalent problem in the spousal relationship, is closely related to the issue of female consciousness. In The Babysitter, Coover （1989） tells of a teenage girl babysitting two kids and a baby and of two of her male peers and the children＇s father altogether exploring their obsession towards her and, moreover, traces the evaluation and devaluation of women to the presentation of TV exploring its influence on his heroines, namely Mrs. Tucker and the babysitter serving as victims of the patriarchal society. Through a close engagement with the sexual objectification theory, this paper analyzes in detail men＇s aggressive oppressions upon women as well as women＇s compromise and rebellion towards the sexual violence, and investigates that the awakening of female independent consciousness is a key factor in effectively helping women achieve the gender equality between sexes.

The role of behavior in tern conservation

Behavioral research has long had an important role in the conservation of terns （Ayes： Stemidae）. Habitat management and restoration of breeding colony sites depends on knowledge of the cues used to select colony and nest sites. For example, conspecific attraction with playback and decoys is commonly used to bring terns to suitable colony sites and habitat modification is often used to increase the availability of suitable nest sites. Tern colonies are interconnected by dispersal, and a metapopulation approach is needed for effective management. Population dynamics are therefore affected by behaviors that influence the frequency of movement among colony sites： site fidelity, natal and breeding dispersal, and group adherence. The monogamous breeding system of terns should keep effective population size similar to census population size, but variation in sex ratios （likely resulting from sex differences in behavior） and in parental quality can result in a smaller than expected effective population size. In addition to the behavior of terns, knowledge of the behavior of predators on terns contributes to management plans, because predator behavior can sometimes be manipulated and predation is often performed by only a few specialized individuals. Other examples of links between tern behavior and conservation are also briefly reviewed, such as behavioral toxicology research and studies of behavioral responses to human disturbance and manmade structures. More work is needed on the behavior of migratory terns at staging sites, stopover sites and wintering grounds, and on the behavior of less well-studied species and species in less well-studied geographic regions [Current Zoology 60 （4）： 500-514, 2014].

Breeding ecology of ground tits in northeastern Tibetan plateau, with special reference to cooperative breeding system

Data on breeding ecology of a color-band marked population of the ground tit Parus humilis were collected in north Qinghai on the Tibetan plateau, during 2008 and 2009. In spring the birds excavated 0.8-3.2 m long nesting burrows under the ground. First-egg laying occurred between late April and late June during which a pair produced one brood. Incubation was done by female alone for 15-16 days and nestling-feeding by both sexes and helpers in any for 23-25 days. Average brood size at fledging was 5.8 （＋ 1.4 SD, 3-8） and all the 27 observed nesting attempts fledged at least one young. At the population level, brood sex ratio did not differ from 1：1. The birds are a territory-living resident, with annual resight rates being 48% （22 of 46） in adult breeders and 10% （7 of 67） in yearlings. Pairs were socially monogamous, of which 23% （9 of 40） contained one and some- times two male helpers, most likely being philopatric sons of the breeders. The formation of cooperative groups is similar to the population in central Tibet but differs from that in south Guansu where breeding ground tits exhibit a high level of annual turnover

The evolution of sexual imprinting in socially monogamous populations

Sexual imprinting is a common mechanism of mate preference learning. It is thought to influence how traits evolve and in some cases to promote speciation. Recently there has been increasing interest in how sexual imprinting itself evolves. Theoretical work on polygynous mating systems predicts that females will evolve paternal imprinting, which means they learn to prefer phenotypes expressed by their fathers. In nature however, females of some species learn to prefer phenotypes expressed by their mothers instead. We used a dynamical systems model and tools from adaptive dynamics to study how sexual imprinting evolves in species with socially monogamous mating systems. We considered cases in which the target trait for imprinting is un- der viability selection but is not a reliable signal of paternal investment. Thus, the target trait signals the genetic benefits rather than the parental care benefits of mate choice. When mating is socially monogamous and there is some extra-pair patemity, we show that maternal imprinting can be favored over paternal imprinting. Counterintuitively, females often become choosier when selecting social partners in systems where extra-pair mating is more frequent. That is, females may be more selective when choosing social partners that will sire a smaller percentage of their offspring. Our results offer new testable hypotheses, and ad- vance our understanding of the mechanisms that drive the evolution of mate choice strategies in nature .

Affairs happen---to whom？ A study on extrapair paternity in common nightingales

Most birds engage in extrapair copulations despite great differences across and within species. Besides cost and benefit considerations of the two sex environmental factors have been found to alter mating strategies within or between populations and/or over time. For socially monogamous species, the main advantage that females might gain from mating with multiple males is probably increasing their offspring＇s genetic fitness. Since male （genetic） quality is mostly not directly meas- urable for female birds, （extrapair） mate choice is based on male secondary traits. In passerines male song is such a sexual ornament indicating male phenotypic and/or genetic quality and song repertoires seem to affect female mate choice in a number of species. Yet their role in extrapair mating behavior is not well understood. In this study, we investigated the proportion of extrapair paternity （EPP） in a population of common nightingales Luscinia megarhynchos. We found that EPP rate was rather high （21.5% of all offspring tested） for a species without sexual dimorphism and high levels of paternal care. Furthermore, the occurrence of EPP was strongly related to the spatial distribution of male territories with males settling in densely occupied areas having higher proportions of extrapair young within their own brood. Also, song repertoire size affected EPP： here larger repertoires of social mates were negatively related to the probability of being cuck- olded. When directly comparing repertoires sizes of social and extrapair mates, extrapair mates tended to have larger repertoires. We finally discuss our results as a hint for a flexible mating strat- egy in nightingales where several factors--including ecological as well as male song features-- need to be considered when studying reproductive behavior in monogamous species with complex song.

Endocrine correlates of mate choice and promiscuity in females of a socially monogamous avian mating system with alternative male reproductive phenotypes

While our understanding of male reproductive strategies is informed by extensive investigations into endocrine mechanisms, the proximate mechanisms by which females compete for mates and adjust reproduction to social environment remains enigmatic. We set out to uncover endocrine correlates of mate choice, social environment, and reproductive investment in female red-backed fairy-wrens Malurus melanocephalus. In this socially monogamous, yet highly sexually promiscuous species, females experience discrete variation in the phenotype of their mates, which vary in both plumage signals and level of paternal care, and in the composition of their breeding groups, which consist of either the pair alone or with an additional cooperative auxiliary; fe- male investment varies according to these social parameters. We found that androgen, estrogen, and glucorticoid levels varied with reproductive stage, with highest androgen and estrogen concentrations during nest construction and highest corticosterone concentrations during the pre-breeding stage. These stage-dependent patterns did not vary with male phenotype or auxiliary presence, though androgen levels during pre-breeding mate selection were lower in females obtaining red/black mates than those obtaining brown mates. We found no evidence that androgen, estrogen, or corticosterone levels during the fertile period were re- lated to extra-pair young （EPY） frequency. This study demonstrates clear changes in steroid levels with reproductive stage, though it found little support for variation with social environment. We suggest hormonal responsiveness to social factors may be physiologically constrained in ways that are bypassed through exogenous hormone manipulations.

Body attributes of both parents jointly affect offspring sex allocation in a socially monogamous, size-monomorphic passerine

Theory predicts that because males are more variable in reproductive success than females, a mother should produce more sons to maximize fitness return from the sex allocation if she is of high-quality （the female quality hypothesis） or mates with a high-quality male （the male quality hypothesis）. While most previous studies have looked at each hypothesis, we tested both of them simultaneously in the white-rumped snowfinch Montifringilla taczanowskii, a socially monogamous, sexually monomorphic passerine where body size is a potential indicator of individual quality in intrasexual competition and territory de- fense. Brood sex ratios at the population level did not deviate from random expectation. Among individual broods, the proportion of sons did not depend on body size of either male or female parent, but on interaction of this trait of both parents. Further analy- ：~es revealed that brood sex ratios were independent of body size of male or female parents when their mates were smaller, but positively related with body size of male or female parents when their mates were larger. These results suggest that mechanisms underlying the two hypotheses may act jointly on offspring sex allocation. The mechanisms are expected to evolve through size-assortative mating which is often reached by sexual selection [Current Zoology 59 （2）： 271-277, 2013].