Encounter rate and task allocation in harvester ants

As conditions change, social insect colonies adjust the numbers of workers engaged in various tasks, such as foraging and nest work. This process of task allocation operates without central control; individuals respond to simple, local cues. This study investigates one such cue, the pattern of an ant's interactions with other workers. We examined how an ant's tendency to perform midden work, carrying objects to and sorting the refuse pile of the colony, is related to the recent history of the ant's brief antennal contacts, in laboratory colonies of the red harvester ant, Pogonomyrmex barbatus. The probability that an ant performed midden work was related to its recent interactions in two ways. First, the time an ant spent performing midden work was positively correlated with the number of midden workers that ant had met while it was away from the midden. Second, ants engaged in a task other than midden work were more likely to begin to do midden work when their rate of encounter per minute with midden workers was high. Cues based on interaction rate may enable ants to respond to changes in worker numbers even though ants cannot count or assess total numbers engaged in a task. Received: 1 July 1998 / Accepted: 15 November 1998     

The moderating role of task characteristics in determining responses to a stressful work simulation

Two experimental studies were conducted to examine whether the stress‐buffering effects of behavioral control on work task responses varied as a function of procedural information. Study 1 manipulated low and high levels of task demands, behavioral control, and procedural information for 128 introductory psychology students completing an in‐basket activity. ANOVA procedures revealed a significant three‐way interaction among these variables in the prediction of subjective task performance and task satisfaction. It was found that procedural information buffered the negative effects of task demands on ratings of performance and satisfaction only under conditions of low behavioral control. This pattern of results suggests that procedural information may have a compensatory effect when the work environment is characterized by a combination of high task demands and low behavioral control. Study 2 (N=256) utilized simple and complex versions of the in‐basket activity to examine the extent to which the interactive relationship among task demands, behavioral control, and procedural information varied as a function of task complexity. There was further support for the stress‐buffering role of procedural information on work task responses under conditions of low behavioral control. This effect was, however, only present when the in‐basket activity was characterized by high task complexity, suggesting that the interactive relationship among these variables may depend on the type of tasks performed at work. Copyright © 1999 John Wiley & Sons, Ltd.     

Sequestered defensive toxins in tetrapod vertebrates: principles, patterns, and prospects for future studies

Chemical defenses are widespread among animals, and the compounds involved may be either synthesized from nontoxic precursors or sequestered from an environmental source. Defensive sequestration has been studied extensively among invertebrates, but relatively few examples have been documented among vertebrates. Nonetheless, the number of described cases of defensive sequestration in tetrapod vertebrates has increased recently and includes diverse lineages of amphibians and reptiles (including birds). The best-known examples involve poison frogs, but other examples include natricine snakes that sequester toxins from amphibians and two genera of insectivorous birds. Commonalities among these diverse taxa include the combination of consuming toxic prey and exhibiting some form of passive defense, such as aposematism, mimicry, or presumptive death-feigning. Some species exhibit passive sequestration, in which dietary toxins simply require an extended period of time to clear from the tissues, whereas other taxa exhibit morphological or physiological specializations that enhance the uptake, storage, and/or delivery of exogenous toxins. It remains uncertain whether any sequestered toxins of tetrapods bioaccumulate across multiple trophic levels, but multitrophic accumulation seems especially likely in cases involving consumption of phytophagous or mycophagous invertebrates and perhaps consumption of poison frogs by snakes. We predict that additional examples of defensive toxin sequestration in amphibians and reptiles will be revealed by collaborations between field biologists and natural product chemists. Candidates for future investigation include specialized predators on mites, social insects, slugs, and toxic amphibians. Comprehensive studies of the ecological, evolutionary, behavioral, and regulatory aspects of sequestration will require teams of ecologists, systematists, ethologists, physiologists, molecular biologists, and chemists. The widespread occurrence of sequestered defenses has important implications for the ecology, evolution, and conservation of amphibians and reptiles.     

Older rural women living with drought

ABSTRACT

Women’s experiences of drought are often made invisible particularly in terms of their long-term effects. Drought differs from other “natural disasters” in that droughts are, by definition, experienced over an extended time. This means those experiencing drought do so as they age, with elderly cohorts particularly vulnerable. As such, there is a need to better understand the longitudinal needs and experiences of women living with drought. This study investigates the experiences of drought for 15 Australian women aged over 70, over a period of 12 years. Longitudinal qualitative free-text comments written by the oldest cohort of women in the Australian Longitudinal Study on Women’s Health were subject to a thematic analysis. Findings indicate that experiences of drought have a relationship to women’s ability to age in ways they may have hoped. Themes of Work and Physical activity, Connection to place, and, Service access were prominent in women’s comments. These results demonstrate that place is an important aspect in the experience of ageing, that work and physical activity often intensify during drought for elderly people who might otherwise be expecting to retire, and that drought presents particular challenges for older women in terms of access to services. This study highlights the complex interactions of living and ageing in drought for Australian women.     

Advocates for environmental justice: the role of the champion in public participation implementation

That segment of the community I would say is just in general pretty disenfranchised. We found that if you want participation you have to go to them. I mean there are days when you just need to go knock on the door.

Brownfields developer in a poor urban neighbourhood

This article considers the role that champions play as advocates for socioeconomically disadvantaged community member involvement in environmental management decision-making. Six case studies of brownfields redevelopment projects located in poor urban neighbourhoods are examined. Analysis of these case studies reveals how champion behaviour, which has typically been studied only in the context of technological innovation, is enacted in public participation efforts in the service of environmental justice. The study finds that champions who emerge in these settings lead the development and implementation of non-standard public participation process innovations.     

Urban Sustainability as a Function of Compromises Households Make Deciding Where and How to Live: Portland and Seattle compared

Planners and policy makers in the UK and the USA widely believe that negative attendants of growth, such as congestion, pollution and sprawl, can be stemmed by mixed-use 'urban village' design solutions. It is assumed that concentrating jobs, housing, shops and schools within compact communities reduces individual recourse to energy-consuming movement. This paper critically examines this assumption. It draws on detailed observation of dual-earner household decisions concerning where and how to live, focusing on the two west-coast US cities of Portland and Seattle. The question is asked whether co-ordination of home and work is more manageable for working parents living in a compact city such as Portland. Contrary to popular belief, urban living is not synonymous with more localised modes of living. Residential preference does not hinge on job location or household structure alone. Equally, job location, child care and shopping practices do not hinge on residential location. For dual-earner households, tensions exist not only between individuals balancing the demands of competing careers but also between mutually exclusive tastes and identitities. Preferences associated with children's education, attachment to place, local social networks and moral cultures effectively cross-cut those of housing choice, journey to work and personal environmental ethos. The resulting 'compromises' profoundly shape the profile and quality of the built environment and its associated ecological footprint. Understanding this requires further development of a household approach to urban social and environmental sustainability. Planificadores y creadores de normas en Gran Bretaña y en Los Estados Unidos creen ampliamente que las asociaciones negativas de crecimiento, tales como congestión, polución y el crecimiento urbano descontrolado, pueden ser detenidas mediante el uso combinado de soluciones de diseño de villas urbanas. Se asume que concentrar empleos, vivienda, almacenes y escuelas dentro de comunidades compactas reduce el recurso individual del consumo de energía por movimiento. Este documento examina críticamente este supuesto. Describe con detallada observación las decisiones de hogares con doble ingreso concerniendo donde y como vivir, centrandose en las dos ciudades de la Costa Oeste de Los Estados Unidos, Portland y Seattle. La pregunta es si la coordinación de hogar y trabajo es mas manejable para padres trabajadores que viven en ciudades compactas como Portland. Contrario a la creencia popular, vida urbana no es sinónimo de mas localizados estilos de vida. La preferencia residencial no depende de la ubicación del trabajo o la sola estructura del hogar. Igualmente, la ubicación del trabajo, guarderias para niños y practicas de compra no dependen del lugar de residencia. Para hogares con doble ingreso, las tensiones no solo existen entre los individuos equilibrando las demandas de carreras competentes sino tambien entre exclusivos gustos e identidades mutuas. Las Preferencias asociadas con la educacion de los niños, el apego al lugar, las redes sociales locales y las culturas morales cortan eficazmente esas de selección de vivienda, trayecto al trabajo y carácter ambiental personal. Los 'acuerdos' resultantes moldean profundamente el perfil y la calidad del ambiente construido y su huella ecológica asociada. Para entender esto se requiere un desarrollo adicional del enfoque del hogar hacia el sostenimiento ambiental y social urbano.     

Positive Planning for Wind-Turbines in an Urban Context

Abstract

An international concern with climate change has prompted a political commitment to the use of renewable energies. Yet, the operationalization and management of this political objective may be frustrated at the local level, where, it is suggested, an implementation impasse exists. This paper reports on a case study that examines the planning issues around the harvesting of wind at an urban brownfield site in Scotland. The paper discusses the nature of the state–market–civil relations involved in the development management of private wind-energy infrastructure, and the potential for a positive mediating role for the planning system.     

Genomic erosion in a demographically recovered bird species during conservation rescue

The pink pigeon (Nesoenas mayeri) is an endemic species of Mauritius that has made a remarkable recovery after a severe population bottleneck in the 1970s to early 1990s. Prior to this bottleneck, an ex situ population was established from which captive-bred individuals were released into free-living subpopulations to increase population size and genetic variation. This conservation rescue led to rapid population recovery to 400–480 individuals, and the species was twice downlisted on the International Union for the Conservation of Nature (IUCN) Red List. We analyzed the impacts of the bottleneck and genetic rescue on neutral genetic variation during and after population recovery (1993–2008) with restriction site-associated sequencing, microsatellite analyses, and quantitative genetic analysis of studbook data of 1112 birds from zoos in Europe and the United States. We used computer simulations to study the predicted changes in genetic variation and population viability from the past into the future. Genetic variation declined rapidly, despite the population rebound, and the effective population size was approximately an order of magnitude smaller than census size. The species carried a high genetic load of circa 15 lethal equivalents for longevity. Our computer simulations predicted continued inbreeding will likely result in increased expression of deleterious mutations (i.e., a high realized load) and severe inbreeding depression. Without continued conservation actions, it is likely that the pink pigeon will go extinct in the wild within 100 years. Conservation rescue of the pink pigeon has been instrumental in the recovery of the free-living population. However, further genetic rescue with captive-bred birds from zoos is required to recover lost variation, reduce expression of harmful deleterious variation, and prevent extinction. The use of genomics and modeling data can inform IUCN assessments of the viability and extinction risk of species, and it helps in assessments of the conservation dependency of populations.     

How colony growth affects forager intrusion between neighboring harvester ant colonies

Summary Colonies of the harvester ant, Pogonomyrmex barbatus, adjust the direction and length of foraging trails in response to the foraging behavior of their conspecific neighbors. In the absence of any interaction with its neighbor, a mature colony expands its foraging range at a rate of 0.85 ± 0.15 m per day. Exclusion experiments show that if a colony is prevented from using its foraging trails, the neighbors of that colony will enter its foraging range within 10 days. Exclusion experiments were performed with three age classes of colonies: young (1 year old), intermediate (3–4 years old), and old (5 years old or more). Colonies 3–4 years old are most likely to expand foraging ranges, and to retain newly-gained areas. To examine the relation of colony age (in years) and colony size (in numbers of workers), colonies of known age were excavated. Colonies increase greatly in size in years 3 and 4. Foraging area may be of greater current or prospective value for younger, smaller, quickly growing colonies than for older, larger ones of stable size. Correspondence to the second address