The stellar halo of the Galaxy

Stellar halos may hold some of the best preserved fossils of the formation history of galaxies. They are a natural product of the merging processes that probably take place during the assembly of a galaxy, and hence may well be the most ubiquitous component of galaxies, independently of their Hubble type. This review focuses on our current understanding of the spatial structure, the kinematics and chemistry of halo stars in the Milky Way. In recent years, we have experienced a change in paradigm thanks to the discovery of large amounts of substructure, especially in the outer halo. I discuss the implications of the currently available observational constraints and fold them into several possible formation scenarios. Unraveling the formation of the Galactic halo will be possible in the near future through a combination of large wide field photometric and spectroscopic surveys, and especially in the era of Gaia.Comment: 46 pages, 16 figures. References updated and some minor changes. Full-resolution version available at http://www.astro.rug.nl/~ahelmi/stellar-halo-review.pd

Factors underlying age-related changes in discrete aiming

Age has a clear impact on one’s ability to make accurate goal-directed aiming movements. Older adults seem to plan slower and shorter-ranged initial pulses towards the target, and rely more on sensory feedback to ensure endpoint accuracy. Despite the fact that these age-related changes in manual aiming have been observed consistently, the underlying mechanism remains speculative. In an attempt to isolate four commonly suggested underlying factors, young and older adults were instructed to make discrete aiming movements under varying speed and accuracy constraints. Results showed that older adults were physically able to produce fast primary submovements and that they demonstrated similar movement-programming capacities as young adults. On the other hand, considerable evidence was found supporting a decreased visual feedback-processing efficiency and the implementation of a play-it-safe strategy in older age. In conclusion, a combination of the latter two factors seems to underlie the age-related changes in manual aiming behaviour

Why male orangutans do not kill infants

Infanticide is widespread among mammals, is particularly common in primates, and has been shown to be an adaptive male strategy under certain conditions. Although no infanticides in wild orangutans have been reported to date, several authors have suggested that infanticide has been an important selection pressure influencing orangutan behavior and the evolution of orangutan social systems. In this paper, we critically assess this suggestion. We begin by investigating whether wild orangutans have been studied for a sufficiently long period that we might reasonably expect to have detected infanticide if it occurs. We consider whether orangutan females exhibit counterstrategies typically employed by other mammalian females. We also assess the hypothesis that orangutan females form special bonds with particular “protector males” to guard against infanticide. Lastly, we discuss socioecological reasons why orangutan males may not benefit from infanticide. We conclude that there is limited evidence for female counterstrategies and little support for the protector male hypothesis. Aspects of orangutan paternity certainty, lactational amenorrhea, and ranging behavior may explain why infanticide is not a strategy regularly employed by orangutan males on Sumatra or Borneo

Genomic Dissection of Bipolar Disorder and Schizophrenia, Including 28 Subphenotypes

publisher: Elsevier articletitle: Genomic Dissection of Bipolar Disorder and Schizophrenia, Including 28 Subphenotypes journaltitle: Cell articlelink: https://doi.org/10.1016/j.cell.2018.05.046 content_type: article copyright: © 2018 Elsevier Inc

Effect of age at release on the post-release survival of head-started Spoon-billed Sandpipers

Headstarting, in which eggs are taken from the nests of wild birds, incubated artificially and the chicks reared in captivity before release to the wild, has been conducted since 2012 on the subarctic breeding grounds of the Critically-Endangered Spoon-billed Sandpiper Calidris pygmaea in an attempt to increase the production of fledged juveniles. We used resightings of individually-marked head-started juveniles after they had moved away from the natal release site to assess differences in post-release survival of birds released at the same site on the same date in relation to differences in the age at which they were released. There was an unexpected significant tendency for survival to decrease with increasing age at release, both for survival beyond the period immediately after release and also to one year old. This effect of age at release is likely to be causal because multiple logistic regression analyses indicated that potential confounding effects of year of release and hatching date did not have statistically significant effects when included in models along with age at release. The mechanism underlying the effect of age at release is unknown, but possible explanations include increased stress or risk of disease or injury of individuals kept captive for longer periods. Our results suggest that releasing all juveniles at the typical age at fledging of wild birds (ca. 17 days) would improve post-release survival substantially. Possible further research could include experiments in which groups of juveniles matched for hatching date and other covariates are released at different ages in the same year and correlative studies of the condition and health of captive juveniles in relation to previous avicultural interventions and the duration of time in captivity.BirdsRussia, Royal Society for the Protection of Birds, Wildfowl and Wetlands Trust, Mangrove Conservation Fund and other donors provided financial support for headstarting and associated studies

Dark Activation of the Stationary Flight of the Fruitfly Drosophila

The fruitfly Drosophila and the housefly Musca develop, under conditions of stationary flight in still air, greater thrust in complete darkness than at constant illumination. This effect of “dark activation” has been demonstrated in earlier experiments with Musca by L. MAF-FEI. The present investigations establish similar reactions in Drosophila. The thrust reduction as a function of luminance resembles the transducer characteristics of light receptors. Dark activation can be elicited throughout the visual field. The effect is mainly mediated by the directly stimulated visual element of the compound eye, provided that the source luminance is low enough to prevent stray light effects in neighbouring elements. Covering the ocelli has little, if any, effect on the dark activation. An influence of position and distribution of the light stimulus on the dark activation is expected, respectively, from the discontinuities of the receptive fields and from possible lateral interactions between neighbouring visual elements. However, an estimate of the expected variations shows that a considerable experimental effort would be necessary to distinguish these variations from statistical fluctuations of the dark activation

Evaluating the Impact of Headstarting on the Critically Endangered Spoon-Billed Sandpiper Calidris pygmaea

Peer reviewed: TrueFunder: Wildfowl and Wetlands Trust (WWT)Funder: Royal Society for the Protection of Birds (RSPB)Funder: Mangrove Conservation Fund (MCF)Headstarting is a conservation approach that suggests offering an advantage to a population by improving egg production, survival of embryos and/or juveniles. In this article, we are providing the quantitative data obtained during 10 years for different stages of headstarting (production of eggs per pair, hatching and fledging rates) and the resulting impact (survival to maturity, philopatry rate, sex ratio, apparent survival, growth/decline rate) on the local population of the critically endangered spoon-billed sandpiper. We have shown that headstarting gains are reduced over time from fledging to long-term recruitment to the local breeding population. The possible reasons for this reduction are suggested and discussed. The unexpected finding was a drastic difference in sex ratios of the new recruits, which was about even for headstarting, but strongly male-biased for wild-reared birds. We suggest this happens due to increased mortality of female chicks in nature. We have also shown only headstarting could stop the global decline of the species, particularly once the suggested improvements are implemented and the number of pairs involved is scaled up. Headstarting also had a significant social effect due to the involvement of increasing numbers of people both in the local communities in Chukotka and from many countries on the flyway into searching for marked birds and learning about waders, raising awareness about ecological problems on the East Asian–Australasian Flyway. Thus, it has made the need for conservation actions on the flyway more obvious and sensible.</jats:p