Combining simulation modeling and stable isotope analyses to reconstruct the last known movements of one of Nature’s giants

The spatial ecology of rare, migratory oceanic animals is difficult to study directly. Where incremental tissues are available, their chemical composition can provide valuable indirect observations of movement and diet. Interpreting the chemical record in incremental tissues can be highly uncertain, however, as multiple mechanisms interact to produce the observed data. Simulation modeling is one approach for considering alternative hypotheses in ecology and can be used to consider the relative likelihood of obtaining an observed record under different combinations of ecological and environmental processes. Here we show how a simulation modeling approach can help to infer movement behaviour based on stable carbon isotope profiles measured in incremental baleen tissues of a blue whale (Balaenoptera musculus). The life history of this particular specimen, which stranded in 1891 in the UK, was selected as a case study due to its cultural significance as part of a permanent display at the Natural History Museum, London. We specifically tested whether measured variations in stable isotope compositions across the analysed baleen plate were more consistent with residency or latitudinal migrations. The measured isotopic record was most closely reproduced with a period of residency in sub-tropical waters for at least a full year followed by three repeated annual migrations between sub-tropical and high latitude regions. The latitudinal migration cycle was interrupted in the year prior to stranding, potentially implying pregnancy and weaning, but isotopic data alone cannot test this hypothesis. Simulation methods can help reveal movement information coded in the biochemical compositions of incremental tissues such as those archived in historic collections, and provides context and inferences that are useful for retrospective studies of animal movement, especially where other sources of individual movement data are sparse or challenging to validate.© 2019 Trueman et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited

The backward-bending commute times of married women with household responsibility

The purpose of this paper is to examine theoretically and empirically whether the commute times of married women follow a backward-bending pattern with respect to wage rates. The existing literature has shown that married women tend to choose short commutes because of their relatively low wages combined with comparatively heavy household responsibilities. However, a workleisure model, which includes the simultaneous decision wives take regarding commute times and wage rates, suggests that married women employed in highly paid positions also undertake short commutes, while married women with wage rates in the middle range choose long commutes. These results suggest that the commute times of married women display a backward-bending pattern. Applying an instrumental variable strategy that accounts for the endogeneity of wage rates, the empirical results for employed married women in Japan appear to support this nding. Moreover, one of our results suggests that highly paid married women can still secure greater leisure time with short commutes, despite retaining a heavy load of domestic responsibilities.Working Paper, No.234, 2008.9.1版http://hdl.handle.net/10110/254

Future directions in research on beaked whales

Until the 1990s, beaked whales were one of the least understood groups of large mammals. Information on northern bottlenose whales (Hyperoodon ampullatus) and Baird’s beaked whales (Berardius bairdii) was available from data collected during whaling, however, little information existed on the smaller species other than occasional data gleaned from beach-cast animals. Recent research advances have been plentiful. Increasing global survey effort, together with morphometric and genetic analyses have shown at least 22 species in this group. Longitudinal field studies of at least four species (H. ampullatus, B. bairdii, Ziphius cavirostris, Mesoplodon densirostris) have become established over the last three decades. Several long-term studies support photo-identification catalogs providing insights into life history, social structure and population size. Tag-based efforts looking at diving, movements and acoustics have provided detail on individual behavior as well as population structure and ranges. Passive acoustic monitoring has allowed long-term and seasonal monitoring of populations. Genetic studies have uncovered cryptic species and revealed contrasting patterns of genetic diversity and connectivity amongst the few species examined. Conservation concern for these species was sparked by mass strandings coincident with military mid-frequency sonar use. Fat and gas emboli have been symptomatic indicators of mortalities related to sonar exposure, suggesting that their vulnerability stems from the physiological exertion of extreme diving for medium-sized whales. Behavioral response experiments have now shown that beaked whales appear to cease foraging and delay their return to foraging and/or leave the area in association with exposure to mid-frequency signals at low acoustic levels. Future priorities for these species will be to (1) continue field-studies to better understand smaller-scale habitat use, vital rates and social structure; (2) develop better detection methods for larger-scale survey work; (3) improve methodology for monitoring energetics, individual body condition and health; (4) develop tools to better understand physiology; (5) use recent genetic advances with improved sample databanks to re-examine global and local beaked whale relationships; (6) further quantify anthropogenic impacts (both sonar and other noise) and their population consequences (7) apply acquired data for realistic mitigation of sonar and other anthropogenic impacts for beaked whale conservation.Publisher PDFPeer reviewe

2008 Lawrence R. Klein Lecture - Comparative Economic Development: Insights from Unified Growth Theory

This paper explores the implications of Unified Growth Theory for the origins of existing differences in income per capita across countries. The theory sheds light on three fundamental layers of comparative development. It identifies the factors that have governed the pace of the transition from stagnation to growth and have thus contributed to contemporary variation in economic development. It uncovers the forces that have sparked the emergence of multiple growth regimes and convergence clubs, and it underlines the persistent effects that variations in pre-historical biogeographical conditions have generated on the composition of human capital and economic development across the globe

Bending fatigue strength and lifetime of fiber ropes

Modern fiber ropes have several distinctive properties which predestine them amongst others for high dynamic applications in robotics. Beside their great breaking load due to their high tensile strength, the extremely low density and weight are the most important advantages over steel wire ropes. For steel wire ropes, it is generally known that their lifetime drops when raising the dynamic stress on running or static ropes. The long-time behavior of high-dynamically stressed fiber ropes is totally unexplored up to now. This lack impedes the breakthrough of fiber ropes and causes a safety gap, which has to be closed. This paper describes the research on modern fiber ropes regarding their lifetime in normal and high dynamic applications. The derived results are interpretered with respect to application in robotics