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Male Care (male + care)
Selected AbstractsDirect Male Care and Hominin Evolution: Why Male,Child Interaction Is More Than a Nice Social IdeaAMERICAN ANTHROPOLOGIST, Issue 1 2010Lee T. Gettler ABSTRACT, Early members of the genus Homo experienced heightened absolute metabolic costs, partially owing to increases in body size. However, as is characteristic of modern humans, they also likely began reproducing with shortened interbirth intervals. Male investment in offspring may help explain how this life history shift occurred. Evolutionary models of hominin male investment in offspring have traditionally focused on provisioning of females and young, yet the extent to which direct male care of offspring was evolutionarily important, from an energetic perspective, is largely unaddressed. I propose an evolutionary model of direct male care, demonstrating that males could have helped reduce the energetic burden of caregiving placed on mothers by carrying young. In doing so, males would have assisted females in achieving and maintaining an energetic condition sufficient for reproduction, thereby hastening the advent of shortened interbirth intervals that played a formative role in the success of our genus. [source] Parental investment, sexual selection and sex ratiosJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2008HANNA KOKKO Abstract Conventional sex roles imply caring females and competitive males. The evolution of sex role divergence is widely attributed to anisogamy initiating a self-reinforcing process. The initial asymmetry in pre-mating parental investment (eggs vs. sperm) is assumed to promote even greater divergence in post-mating parental investment (parental care). But do we really understand the process? Trivers [Sexual Selection and the Descent of Man 1871,1971 (1972), Aldine Press, Chicago] introduced two arguments with a female and male perspective on whether to care for offspring that try to link pre-mating and post-mating investment. Here we review their merits and subsequent theoretical developments. The first argument is that females are more committed than males to providing care because they stand to lose a greater initial investment. This, however, commits the ,Concorde Fallacy' as optimal decisions should depend on future pay-offs not past costs. Although the argument can be rephrased in terms of residual reproductive value when past investment affects future pay-offs, it remains weak. The factors likely to change future pay-offs seem to work against females providing more care than males. The second argument takes the reasonable premise that anisogamy produces a male-biased operational sex ratio (OSR) leading to males competing for mates. Male care is then predicted to be less likely to evolve as it consumes resources that could otherwise be used to increase competitiveness. However, given each offspring has precisely two genetic parents (the Fisher condition), a biased OSR generates frequency-dependent selection, analogous to Fisherian sex ratio selection, that favours increased parental investment by whichever sex faces more intense competition. Sex role divergence is therefore still an evolutionary conundrum. Here we review some possible solutions. Factors that promote conventional sex roles are sexual selection on males (but non-random variance in male mating success must be high to override the Fisher condition), loss of paternity because of female multiple mating or group spawning and patterns of mortality that generate female-biased adult sex ratios (ASR). We present an integrative model that shows how these factors interact to generate sex roles. We emphasize the need to distinguish between the ASR and the operational sex ratio (OSR). If mortality is higher when caring than competing this diminishes the likelihood of sex role divergence because this strongly limits the mating success of the earlier deserting sex. We illustrate this in a model where a change in relative mortality rates while caring and competing generates a shift from a mammalian type breeding system (female-only care, male-biased OSR and female-biased ASR) to an avian type system (biparental care and a male-biased OSR and ASR). [source] Harem size and oviposition behaviour in a polygynous bark beetleECOLOGICAL ENTOMOLOGY, Issue 5 2009TANYA M. LATTY Abstract. 1. Harem polygyny can have fitness benefits and costs on females. In bark beetles of the genus Ips the latter may include within-harem competition between larvae. However, earlier competition between females for male care and mating opportunities may also influence oviposition behaviour. There has been relatively little investigation into the relationship between harem size and initial egg output. The present study investigated this relationship in the bark beetle Ips grandicollis. 2. The measure of egg output used was the number of eggs in the gallery with the most eggs in each harem. Mean (±SE) harem size of 242 observed harems was 3.25 ± 0.10. A curvilinear relationship was found between egg output and harem size, with females in smaller harems (one to four females) laying more eggs with increased harem size. However, females in larger harems (five to seven females) laid fewer eggs as harem size increased. The optimal harem size (in terms of number of eggs laid) was close to four females. 3. We found no evidence from a behavioural assay that females could preferentially choose unmated males over mated males with harems of two females. Additionally, the distribution of harem sizes suggests that females distribute themselves among males randomly. 4. The results suggest that harem size has effects on female reproduction that extend beyond larval competition and influence patterns of oviposition. The mechanism that determines why egg laying is greatest at intermediate levels is unknown. There is no evidence that smaller harems belong to lower quality males, but females may adjust egg-laying behaviour in large harems as a result of reduced male attendance or anticipated larval competition. [source] Brood conspicuousness and clutch viability in male-caring assassin bugs (Rhinocoris tristis)ECOLOGICAL ENTOMOLOGY, Issue 2 2009JAMES GILBERT Abstract 1.,Conspicuousness to mates can bring benefits to both males (increased mating success) and females (reduced search costs), but also brings costs (e.g. increased predation and parasitism). Assassin bugs, Rhinocoris tristis, lay egg clutches either on exposed stems or hidden under leaves. Males guard eggs against parasitoids. Guarding males are attractive to females who add subsequent clutches to the brood. This is an excellent opportunity to study the effects of conspicuousness on the fitness of males and females. 2.,Using viable eggs in a multi-clutch brood as a correlate of fitness, the present study examined whether laying eggs on stems affected (1) female fitness, through exposure to parasitism and cannibalism, and (2) male fitness, through attracting further females. 3.,Stem broods were more parasitised. However, males on stems accumulated more mates and more eggs, a net benefit even accounting for parasitism. The eggs gained from being on a stem were cannibalised. By contrast, higher mortality on stems suggests that females should gain by ovipositing on leaves. To the extent that egg viability represents fitness, male and female interests may therefore differ. This suggests a potential for sexual conflict that may affect other species with male care. 4.,Despite higher costs, females actually initiated more broods, and subsequently added bigger clutches to broods, on stems than under leaves. This suggests either that viable eggs do not reflect fitness, or that females laid in unfavourable locations. The key is now to address lifetime fitness, since unmeasured factors may affect offspring viability post-hatching, and to investigate who controls the location of oviposition in R. tristis. [source] Sex roles, parental effort and offspring desertion in the monogamous Eurasian Curlew Numenius arquataIBIS, Issue 3 2001DAVE CURRIE The reasons for female desertion of offspring and the evolution of predominantly male care among monogamous bird species are not clearly understood. We studied parental effort during the incubation and chick rearing periods in the Eurasian Curlew Numenius arquata in western Finland, and compared timing of brood desertion with other populations in Europe. Males and females contributed equally to incubation and showed no differences in the intensity of mobbing behaviour towards a potential nest predator (stuffed crow) shortly after hatching. However, females deserted their offspring approximately halfway through the brooding period (c. 16 d after hatching), while males remained with chicks until independence (c. 35 d). Females with late-laid clutches deserted their offspring sooner after hatching than those with clutches produced earlier in the season. Curlew females deserted younger chicks in northeast Europe, where laying dates were later, breeding seasons shorter and migration distances were longer, than in western and central Europe. We suggest that the most likely reasons for offspring desertion by females may be associated with increased female survivorship and maintenance of pairbond between years. [source] Direct Male Care and Hominin Evolution: Why Male,Child Interaction Is More Than a Nice Social IdeaAMERICAN ANTHROPOLOGIST, Issue 1 2010Lee T. Gettler ABSTRACT, Early members of the genus Homo experienced heightened absolute metabolic costs, partially owing to increases in body size. However, as is characteristic of modern humans, they also likely began reproducing with shortened interbirth intervals. Male investment in offspring may help explain how this life history shift occurred. Evolutionary models of hominin male investment in offspring have traditionally focused on provisioning of females and young, yet the extent to which direct male care of offspring was evolutionarily important, from an energetic perspective, is largely unaddressed. I propose an evolutionary model of direct male care, demonstrating that males could have helped reduce the energetic burden of caregiving placed on mothers by carrying young. In doing so, males would have assisted females in achieving and maintaining an energetic condition sufficient for reproduction, thereby hastening the advent of shortened interbirth intervals that played a formative role in the success of our genus. [source] The effects of lactation and infant care on adult energy budgets in wild siamangs (Symphalangus syndactylus)AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2009Susan Lappan Abstract In mammals with biparental care of offspring, males and females may bear substantial energetic costs of reproduction. Adult strategies to reduce energetic stress include changes in activity patterns, reduced basal metabolic rates, and storage of energy prior to a reproductive attempt. I quantified patterns of behavior in five groups of wild siamangs (Symphalangus syndactylus) to detect periods of high energetic investment by adults and to examine the relationships between infant care and adult activity patterns. For females, the estimated costs of lactation peaked at around infant age 4,6 months and were low by infant age 1 year, whereas the estimated costs of infant-carrying peaked between ages 7 and 12 months, and approached zero by age 16 months. There was a transition from primarily female to male care in the second year of life in some groups. Females spent significantly less time feeding during lactation than during the later stages of infant care, suggesting that female siamangs do not use increased food intake to offset the costs of lactation. Female feeding time was highest between infant ages 16 and 21 months, a period of relatively low female investment in the current offspring that coincided with the period of highest male investment in infant care. This suggests that male care may reduce the costs of infant care for females in the later stages of a reproductive attempt. The female energy gain resulting from male care was likely invested in somatic maintenance and future reproduction, rather than the current offspring. Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc. [source] | ||||||||||