Squirrels in suburbia: influence of urbanisation on the occurrence and distribution of a common exotic mammal

Urbanisation is widely considered to promote the establishment of non-native species, but there is limited empirical evidence of the ecological factors driving their responses. The grey squirrel Sciurus carolinensis (Gmelin 1788) is native to North America, but is widespread in the UK and is starting to spread across Europe. It is regarded as one of the world’s worst invasive animals due to its adverse impacts on native biodiversity. We use the non-native grey squirrel population in Sheffield (UK) as a case study to assess which factors limit its distribution and abundance in urban environments. In 2010 the city-wide population of adult squirrels peaked at an estimated 6539 in autumn (0.46 squirrels/ha), with maximum local densities of 8.29/ha. These densities appear to be slightly lower than those recorded in urban environments in the species’ native range. Grey squirrels occurred more frequently at urban sites with larger amounts of green-space in the surrounding region. Local habitat characteristics were, however, more powerful predictors of urban grey squirrel occurrence and abundance than regional availability of green space. Canopy cover, seed bearing trees and supplementary feeders, provided for garden birds, positively influenced grey squirrels. The potential for grey squirrels to connect city dwellers with nature thus appears to be highest in urban locations that have considerable capacity to support native biodiversity. The beneficial impacts of supplementary feeding on grey squirrel populations is notable given concerns that squirrels can adversely influence bird populations. These habitat associations also imply that grey squirrels typically respond negatively to urbanisation, which challenges arguments that urbanisation favours exotic species.     

Why do People Disclose their HIV Status? Qualitative Evidence from a Group of Activist Women in Khayelitsha

Abstract

This study explores the bio-psychosocial context of HIV/AIDS in which eleven HIV-positive activist women from Khayelitsha negotiated the process of disclosing their HIV-positive status to significant others, specifically biological household members. The study is based on the narratives of a group of HIV-positive peer-educators in Cape Town, South Africa. The results suggest that community perceptions of HIV/AIDS are shaped by a wide variety of factors particular to the socio-cultural and political context of HIV/AIDS in South Africa. The process and outcomes of disclosure to others occurs within this shifting web of meanings, and in turn, reshapes them as people respond to the person who has just disclosed. Eight out of the eleven women disclosed to a close biological household member as these significant-others provided, or had the potential to provide, the appropriate support. Six of the eleven participants disclosed during the symptomatic phases of HIV/AIDS, while five were asymptomatic at the time. Four of the five who disclosed when asymptomatic were diagnosed while pregnant and had never experienced severe opportunistic infections. Additionally, these same four disclosed some time after diagnosis (nine months > t < two years). Of the six who disclosed in a state of ill-health, five disclosed immediately after diagnosis in order to access health-related social support. At this time, concerns regarding health and mortality superseded fears of rejection and discrimination due to AIDS-related stigma. The perceived potential benefits (social and health-related support) outweighed the perceived risks (stigmatisation and discrimination). When participants had never experienced serious illness, they disclosed in order to educate loved-ones, gain emotional support or challenge false popular perceptions of HIV/AIDS.     

Detection of multiple undocumented change-points using adaptive Lasso

The problem of detecting multiple undocumented change-points in a historical temperature sequence with simple linear trend is formulated by a linear model. We apply adaptive least absolute shrinkage and selection operator (Lasso) to estimate the number and locations of change-points. Model selection criteria are used to choose the Lasso smoothing parameter. As adaptive Lasso may overestimate the number of change-points, we perform post-selection on change-points detected by adaptive Lasso using multivariate t simultaneous confidence intervals. Our method is demonstrated on the annual temperature data (year: 1902–2000) from Tuscaloosa, Alabama.     

Piece rates and workplace injury: Does survey evidence support Adam Smith?

While piece rates are routinely associated with higher productivity and wages, they can also generate unanticipated effects. Using cross-country European data, we provide among the first general survey evidence of a strong link between piece rates and workplace injury. Despite controls for workplace hazards, job characteristics and worker effort, piece rates workers suffer a 5 percentage point greater likelihood of injury. This remains despite attempts to control for endogeneity and heterogeneity. As piece rate wage premium estimates rarely control for injury likelihood, this raises the specter that part of that premium reflects a compensating wage differential for risk of injury.     

Testing Multiple Forecasters

We consider a cross‐calibration test of predictions by multiple potential experts in a stochastic environment. This test checks whether each expert is calibrated conditional on the predictions made by other experts. We show that this test is good in the sense that a true expert—one informed of the true distribution of the process—is guaranteed to pass the test no matter what the other potential experts do, and false experts will fail the test on all but a small (category I) set of true distributions. Furthermore, even when there is no true expert present, a test similar to cross‐calibration cannot be simultaneously manipulated by multiple false experts, but at the cost of failing some true experts.     

LESSONS FOR RESEARCHERS AND FUNDING AGENCIES FROM HURRICANE KATRINA: A RESEARCH NOTE FROM MISSISSIPPI

We surveyed National Science Foundation (NSF)-funded research in Mississippi to determine the economic extent of research damage and delays due to Hurricane Katrina. While several facilities were physically damaged, we found that the largest effects were time delays and missed opportunities. While psychological factors were not part of the original economic impact study, it became clear that they played an important role. Specifically, the Principal Investigator's (PI's) attitude of “just another delay” was one cultural barrier to fully accounting for the cost of these research delays. We concluded that Principal Investigators, with the assistance of funding agencies, should be better trained to measure time and opportunity costs associated with their research, so future disaster recovery efforts can more fully address those needs.     

Time-on-task, technology and mathematics achievement

Information and communication technologies hold much promise for use in education in developing countries. This study reports on an evaluation conducted on the introduction of computers in the delivery of the mathematics curriculum in one of the provinces of South Africa. Although the request was for an outcome evaluation very early in the implementation of the program, it was tailored in such a way as to fulfill a more formative role. Despite substantial variability in implementation, and in most cases with very weak exposure of the learners to the intervention, sufficient evidence emerged to indicate that this mode of curriculum delivery may be effective. Improvement in mathematics performance was related to a range of variables: some concerned classroom teaching practices, some referred to social differences between the learners, and some to the specific intervention. The strongest of these predictors in the sample was the strength of the intervention: the more time learners spent on using the software to study mathematics, the more improvement they showed from 1 year to the next in their performance in the subject.