137 resultados para Sexual selection in animals


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Women reporting childhood sexual abuse (CSA) that involved actual or attempted penetration may not identify this as their first sexual intercourse. Data were drawn from a population-based, prospective cohort study spanning adolescence to adulthood. CSA prior to age 16 and age of first sexual intercourse with a male were assessed retrospectively. More than half of women reporting CSA in the form of actual or penetrative abuse reported an age of first sexual intercourse at or beyond 16 years. Direct questioning about CSA is needed to accurately ascertain sexual history.

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One of the issues associated with pattern classification using data based machine learning systems is the “curse of dimensionality”. In this paper, the circle-segments method is proposed as a feature selection method to identify important input features before the entire data set is provided for learning with machine learning systems. Specifically, four machine learning systems are deployed for classification, viz. Multilayer Perceptron (MLP), Support Vector Machine (SVM), Fuzzy ARTMAP (FAM), and k-Nearest Neighbour (kNN). The integration between the circle-segments method and the machine learning systems has been applied to two case studies comprising one benchmark and one real data sets. Overall, the results after feature selection using the circle segments method demonstrate improvements in performance even with more than 50% of the input features eliminated from the original data sets.

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Abuse is rife in Disgrace by J.M. Coetzee and Cereus Blooms at Night by Shani Mootoo. Sexual violence is in both narratives, part of their richly textured social, emotional and political worlds. Fiction involving various traumas seems bleak, almost hopeless, perhaps weighted by sadness. Yet both these novels, even through depictions of rupturing, disruptive rape, trigger a recognition of possibility and potential among characters and perhaps readers. It is in this open ended potential for betterment of some kind that hope lies. What is the nature of hope and to what extent is it present in these novels? In this paper, I explore the emotion of hope in relation to the notion of becoming as elaborated on by Gilles Deleuze and Felix Guattari particularly in A Thousand Plateaus. They expound on Remy Chauvin‟s term “aparallel evolution” in relation to becoming (Deleuze and Guattari, 11). Deleuze also states that becoming is not a “phenomena of imitation or assimilation”. Rather, it is an encounter, “a double capture” (Deleuze and Parnet 2) between heterogeneous elements. There is no end or destination in becoming; it is constant change. I examine the transformative potential of becoming to elicit signs of hope in these novels. David Lurie, the self-absorbed womaniser and arguably rapist, becomes-dog by the end of Disgrace. How does this contribute to any sense of redemption and consequently hope? And how does hope emanate from the beaten, broken, brutally raped Mala Ramchandin in Cereus Blooms at Night? At heart, this paper is an acknowledgment of the unique relation literature has with life and the enriching insight that it may provide into the expression of hope.

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Conflicts in Rwanda and the former Yugoslavia and the work of related criminal tribunals established legal bases for rejecting tactical rape and sexual violence in war as violating international humanitarian and human rights law. The UN Security Council has acknowledged security threats posed by these violations. There remain significant challenges.

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The temporal distribution of nesting and mating in green turtles Chelonia mydas at Ascension Island (7°57¹S, 14°22¹W) in the South Atlantic is described. Mathematical description of the seasonal pattern of nesting showed extreme similarity between seasons, and evidence is presented to support the hypothesis that observed patterns are driven by prevailing environmental temperature. Mating was observed to begin before nesting and follow a pattern consistent with a modelled seasonal influx of suitable females into the annual breeding population. When available data on male size are compared with that of females from the same population (n = 12 populations), a pronounced and consistent sexual dimorphism, with males being smaller than females, is highlighted in all populations. The possible mechanisms behind the evolution of such a pattern are discussed.

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Conspecific nesting density affects many aspects of breeding biology, as well as habitat selection decisions. However, the large variations in breeding density observed in many species are yet to be fully explained. Here, we investigated the settlement patterns in a colonial species with variable breeding density and where resource distribution could be manipulated. The zebra finch, Taeniopygia guttata, is a classic avian model in evolutionary biology but we know surprisingly very little about nest site selection strategies and nesting densities in this species, and in fact, in nomadic species in general. Yet, important determinants of habitat selection strategies, including temporal predictability and breeding synchrony, are likely to be different in nomadic species than in the non-nomadic species studied to date. Here, we manipulated the distribution of nesting sites (by providing nest boxes) and food patches (feeders) to test four non-exclusive habitat selection hypotheses that could lead to nest aggregation: 1) attraction to resources, 2) attraction to breeding conspecifics, and 3) attraction to successful conspecifics and 4) use of private information (i.e. own reproductive success on a site). We found that wild zebra finches used conspecific presence and possibly reproductive success, to make decisions over where to locate their nests, but did not aggregate around water or food within the study areas. Moreover, there was a high degree of inter-individual variation in nesting density preference. We discuss the significance of our results for habitat selection strategy in nomadic species and with respect to the differential selection pressures that individuals breeding at different densities may experience.

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The captive zebra finch, Taeniopygia guttata, has become one of the key vertebrate model systems for studying a range of behavioural, physiological and neurological phenomena. In particular, this species has played a key role in developing our understanding of sexual selection and sperm competition. In contrast with the large number of studies using domesticated zebra finches, relatively few studies have focused on free-living populations of wild zebra finches. Investigating the incidence of extrapair paternity in zebra finches in the Australian desert, we found a very low level; 1.7% of 316 offspring from four of 80 broods fathered outside the pair bond. These numbers contrast with the high levels of extrapair paternity observed in domesticated aviary populations, and suggest a low level of sperm competition and sexual selection in natural populations. Our finding of such a low rate of extrapair paternity in the wild zebra finch suggests that it is one of the most genetically monogamous of all passerine species and that has important implications for future studies of this model organism in studies of sexual selection and reproductive biology. In addition, we found that 5.4% of 316 offspring were not related to either putative parent and hatched from eggs that had been dumped by intraspecific brood parasites.