The present study investigated processes by which job stress and satisfaction unfold over time by examining the relations between daily stressful events, mood, and these variables. Using a Web-based daily survey of stressor events, perceived strain, mood, and job satisfaction completed by 14 university workers, 1,060 occasions of data were collected. Transfer function analysis, a multivariate version of time series analysis, was used to examine the data for relationships among the measured variables after factoring out the contaminating influences of serial dependency. Results revealed a contrast effect in which a stressful event associated positively with higher strain on the same day and associated negatively with strain on the following day. Perceived strain increased over the course of a semester for a majority of participants, suggesting that effects of stress build over time. Finally, the data were consistent with the notion that job satisfaction is a distal outcome that is mediated by perceived strain.

The conservation of bison (Bison bison) from near extinction to >4,000 animals in Yellowstone National Park has led to conflict regarding overabundance and potential transmission of brucellosis (Brucella abortus) to cattle. We estimated survival and birth rates from 53 radiocollared adult female bison during 1995–2001, and we used calf:adult (C:A) ratios to estimate reproduction with the combined effects of pregnancy, fetal loss, and neonatal mortality during 1970–1997. Annual survival of adult females was high (0.92; 95% CI = 0.87‐0.95) and constant. Birth rates differed by brucellosis status and age. Birth rates were 0.40 calves per female (95% CI = 0.15‐0.65) for brucellosis‐positive 3 year olds, 0.63 (95% CI = 0.39‐0.87) for individuals testing negative, and 0.10 (95% CI = 0.00‐0.24) for individuals contracting brucellosis that birth year (sero‐converters). Birth rates were 0.64 (95% CI = 0.52‐0.76) for brucellosis‐positive individuals ≥4 years old, 0.81 (95% CI = 0.73‐0.89) for brucellosis‐negative individuals, and 0.22 (95% CI = 0.00‐0.46) for sero‐converters. Spring C:A ratios were negatively correlated with snow pack (β = −0.01 to −0.03, R2 = 0.26‐0.60, P < 0.05). Growth rate was highly elastic to adult survival (0.51), and juvenile survival (0.36) was 3 times more elastic than fecundity (0.12). Simulations suggested brucellosis eradication via vaccination would result in increased birth rates and a 29% increase in population growth (γ = 1.09), possibly leading to more bison movements outside the park. Our results will help park managers evaluate bison population dynamics and explore consequences of management actions and disease control programs.

: Understanding the relative importance of density‐dependent and density‐independent feedback on population growth is essential for developing management strategies to conserve wildlife. We examined a 99‐year time series of annual counts and removals for 2 bison (Bison bison) herds occupying northern and central Yellowstone National Park in the western United States. Yellowstone's aggressive management intervention effectively recovered bison from 46 animals in 1902 to > 1,500 animals in 1954. Supplemental feeding of the northern herd facilitated rapid growth (r = 0.16) during 1902 to 1952. Augmentation of the central herd with 71 animals also led to rapid growth over 1936 to 1954 (r = 0.10). In 1969, manipulative management ceased in the park, and we detected evidence of density‐dependent changes in population growth rates for both herds during 1970 to 2000 as numbers increased to >3,000 animals. The central herd showed evidence of a constant density‐dependent response over 1970 to 2000. In contrast, density dependence had a stronger effect on the northern herd's growth rate during 1970 to 1981 than during 1982 to 2000. We found evidence to suggest that these trends resulted from pulses of emigration from the central herd to the northern range beginning in 1982 in response to resource limitation generated by an interaction between density and severe snow pack. Corroborative evidence supporting this interpretation included 1) the annual growth of the central herd was negatively correlated with snow pack but that of the northern herd was not, 2) growth rates of the central and northern herds were uncorrelated during 1970 to 1981 but significantly and negatively correlated during 1982 to 2000, and 3) the northern herd could not have sustained the high removals experienced during 1984 to 2000 without immigration. Density‐related emigration from the central herd to the northern range may be fueling bison emigration onto private and public lands where large‐scale removals occur, exacerbating the brucellosis controversy for natural resource managers.

No abstract

The advent of modern industrial processes, the globalization of the economy, and the proliferation of information technology, among other factors, have contributed to the creation of a 24-hour society in recent times. As the demand for 24-hour availability of goods and services has risen over the past few decades, the prevalence of shiftwork has likewise increased. In the United States, approximately 20% of all nonagricultural workers experience some type of shiftwork, and 25% of these shiftworkers work at night (U.S. Congress, Office of Technology Assessment, 1991). Estimates for European workers are similar (Wedderburn, 1996).Shiftwork is defined as any arrangement of daily working hours that differs from the standard daylight hours. Organizations that adopt shiftwork systems extend their hours of work past eight hours by using successive teams of workers. The nature of shift systems can vary widely along several dimensions, including the number and length of shifts, the presence or absence of night work, the direction and speed of the shift rotation (or whether the shift rotates or not), the length of the shift cycles, the start and stop times of each shift, and the number and placement of days off.The scientific community has long maintained that individuals who regularly work atypical hours (i.e., shiftwork of some type) are at greater risk for physical and psychological impairment or disease than typical day workers (e.g., Costa, 1996;Costa, Folkard, & Harrington, 2000). This risk is assumed to originate from the physical and psychological stress that develops from work schedule-related disruptions of their biological functions, sleep, and social and family life. The risk is further exacerbated by extended hours of work beyond the standard 40-hour week, a trend that has also been increasing over the past several years (Costa et al., 2000).In this chapter, we explore the relationships between shiftwork and health. We do not attempt to be comprehensive, but rather representative, in our review of the published research literature. First, we provide general background information on circadian rhythms to prepare the reader for the balance of the chapter. Second, we review the empirical literature on shiftwork and various types of health-related strains or outcomes. Third, we examine some of the factors (e.g., age, personality) that have been investigated in the search for the "shiftwork tolerant" individual. Fourth, we explore the various types of interventions that have been attempted to 163