A model comparison reveals dynamic social information drives the movements of humbug damselfish (Dascyllus aruanus).

Animals make use a range of social information to inform their movement decisions. One common movement rule, found across many different species, is that the probability that an individual moves to an area increases with the number of conspecifics there. However, in many cases, it remains unclear what social cues produce this and other similar movement rules. Here, we investigate what cues are used by damselfish (Dascyllus aruanus) when repeatedly crossing back and forth between two coral patches in an experimental arena. We find that an individual's decision to move is best predicted by the recent movements of conspecifics either to or from that individual's current habitat. Rather than actively seeking attachment to a larger group, individuals are instead prioritizing highly local and dynamic information with very limited spatial and temporal ranges. By reanalysing data in which the same species crossed for the first time to a new coral patch, we show that the individuals use static cues in this case. This suggests that these fish alter their information usage according to the structure and familiarity of their environment by using stable information when moving to a novel area and localized dynamic information when moving between familiar areas.

The lifetime costs of increased male reproductive effort: courtship, copulation and the Coolidge effect.

The reproductive effort that a male directs to a familiar female declines over time, suggesting decreasing marginal returns. But is this diminishing returns a function of increasing reproductive costs or decreasing benefits of sustained effort? Here, we use the restoration of male reproductive effort with unfamiliar females to differentiate the role of diminishing returns and lifetime costs of increased reproductive effort of male guppies. We kept males with familiar or unfamiliar females throughout their lives and manipulated their ability to either court or mate with females. We found that increased male reproductive effort with novel mates lead to an immediate trade-off in the form of reduced foraging effort. Further, males able to mate with a series of unfamiliar females had lower lifetime growth, indicating the primary cost of male reproductive effort in guppies arises from copulation rather than courtship. The lifetime growth trade-offs were significant only when males mated with unfamiliar mates, suggesting that male reproductive effort with familiar females declines before it is restricted by physical exhaustion. These findings provide some of the first evidence of longitudinal costs of increased male reproductive effort in a vertebrate.

Sampling and data collection methods in the National Evaluation of School Nutrition Programs.

A nested sampling design is described in which school districts are selected, schools within those districts that cover grades one through 12 are selected, and finally students within each of the grades are selected. The article describes how nutritional status information is collected from each student, economic and food expenditure data are collected from the students' parents, and information on food services is collected from district and school administrators. Sample weighting and adjustments for nonresponse bias are discussed in the appendix.

The National Evaluation of School Nutrition Programs: data analysis methods.

An overview of the analytic methods used in the National Evaluation of School Nutrition Programs is provided. A path model is described that shows the hypothesized relationships between outcome and predictor variables. The outcome variables are participation in the School Nutrition Programs and the effects of participation on family food expenditures and student dietary intake and anthropometric measurements. Individual student participation in the programs is seen as the last of a series of participation decisions that include the school's decision to offer the program and the prices charged for meals. Selection of specific statistical and structural models to present these relationships are discussed. The decision to use ordinary least square estimates of impact rather than a modified two-stage least squares approach is explained.

Monitoring health status, access to health care, and compliance behavior in a large urban community: a report from the Los Angeles health survey.

This article summarizes results from 2 health surveys conducted in Los Angeles County in 1974 and 1977. The original objective of this analysis was to identify aggregate changes in the health status of this population, in access as measured by the use/disability ratio, and in self-reported compliance with medical regimens. Additionally, we have suggested that this study illustrates the value of local population surveys for health policy--particularly in regard to recent Health Systems Agencies legislation. Substantial correspondence was found between the health status characteristics of both samples and national estimates, particularly for the prevalence of chronic illness. We also found a 3-year trend of increasing disability that is consisted with national data. However, unlike the national estimates, we found evidence of improved access relative to disability, and a corresponding reduction in the traditional income differential. Analysis of self-reported compliance showed little change over time, with Anglos and the middle and upper socioeconomic groups reporting less compliance with their doctors' recommendations.