Diet preferences as the cause of individual differences rather than the consequence

Behavioural variation within a species is usually explained as the consequence of individual variation in physiology. However, new evidence suggests that the arrow of causality may well be in the reverse direction: behaviours such as diet preferences cause the differences in physiological and morphological traits. Recently, diet preferences were proposed to underlie consistent differences in digestive organ mass and movement patterns (patch residence times) in red knots (Calidris canutus islandica). Red knots are molluscivorous and migrant shorebirds for which the size of the muscular stomach (gizzard) is critical for the food processing rate. In this study, red knots (C. c. canutus, n = 46) were caught at Banc d'Arguin, an intertidal flat ecosystem in Mauritania, and released with radio-tags after the measurement of gizzard mass. Using a novel tracking system (time-of-arrival), patch residence times were measured over a period of three weeks. Whether or not gizzard mass determined patch residence times was tested experimentally by offering 12 of the 46 tagged red knots soft diets prior to release; this reduced an individual's gizzard mass by 20–60%. To validate whether the observed range of patch residence times would be expected from individual diet preferences, we simulated patch residence times as a function of diet preferences via a simple departure rule. Consistent with previous empirical studies, patch residence times in the field were positively correlated with gizzard mass. The slope of this correlation, as well as the observed range of patch residence times, was in accordance with the simulated values. The 12 birds with reduced gizzard masses did not decrease patch residence times in response to the reduction in gizzard mass. These findings suggest that diet preferences can indeed cause the observed among-individual variation in gizzard mass and patch residence times. We discuss how early diet experiences can have cascading effects on the individual expression of both behavioural and physiomorphic traits. This emphasizes that to understand the ecological consequences of individual differences, knowledge of the environment during development is required

Recent advances in understanding hypertension development in sub-Saharan Africa

Consistent reports indicate that hypertension is a particularly common finding in black populations. Hypertension occurs at younger ages and is often more severe in terms of blood pressure levels and organ damage than in whites, resulting in a higher incidence of cardiovascular disease and mortality. This review provides an outline of recent advances in the pathophysiological understanding of blood pressure elevation and the consequences thereof in black populations in Africa. This is set against the backdrop of populations undergoing demanding and rapid demographic transition, where infection with the Human Immunodeficiency Virus predominates, and where under and over-nutrition coexist. Collectively, recent findings from Africa illustrate an increased lifetime risk to hypertension from foetal life onwards. From young ages black populations display early endothelial dysfunction, increased vascular tone and reactivity, microvascular structural adaptions, as well as increased aortic stiffness resulting in elevated central and brachial blood pressures during the day and night, when compared to whites. Together with knowledge on the contributions of sympathetic activation and abnormal renal sodium handling, these pathophysiological adaptations result in subclinical and clinical organ damage at younger ages. This overall enhanced understanding on the determinants of blood pressure elevation in blacks encourages (a) novel approaches to assess and manage hypertension in Africa better, (b) further scientific discovery to develop more effective prevention and treatment strategies, and (c) policymakers and health advocates to collectively contribute in creating health-promoting environments in Africa

Student emotions in class : The relative importance of teachers and their interpersonal relations with students

This study highlights the importance of teachers in relation to the emotions students experience in class. First, in line with the work of Kenny, we argue that the specific relationship that evolves between teachers and students drives students' emotional experiences. We decompose variability in student emotions not only into the commonly investigated student and teacher facets but also into facets representing specific pairings of teachers with classes and students (so-called relationship effects). Second, using interpersonal theory, we assess the degree to which the interpersonal quality of teaching accounts for variability in student emotions. Cross-classified multilevel modelling of 8042 student ratings (N ¼ 1668 secondary school students, Mage ¼ 14.94) of 91 teachers indicated that a considerable amount of variability that is usually assigned to the student level may be due to relationship effects involving teachers. Furthermore, the way that teachers interpersonally relate to their students is highly predictive of student emotions. In sum, teachers may be even more important for student emotions than previous research has indicated

Data presented in the paper "Colony-breeding Eurasian spoonbills in the Netherlands: local limits to population growth with expansion into new areas"

The dataset contains three files, all relating to spoonbill breeding colonies in the Netherlands. We used this dataset to assess population growth of Spoonbills in the Netherlands, and especially in the Wadden Sea. The first file contains yearly breeding colony sizes, which were obtained by counting in each of the colonies in each year the number of breeding pairs. This was done mostly by local nature management teams. The second file contains for several colonies in the Wadden Sea area the average yearly breeding success. This number was obntained by counting the number of fledglings in the ebnd of the breeding season. This was also done mainly by local nature management teams. The last file contains data on the condition of individual chicks in several colonies. These were obtained by researchers from the University of Groningen and NIOZ, and by several Staatsbosbeheer officers

Structurally complex sea grass obstructs the sixth sense of a specialized avian molluscivore

Contains fulltext : 158880.pdf (publisher's version ) (Closed access