Variation in the food hoarding behaviour of red squirrels

Summary To investigate variation in food storing behaviour within a population of red squirrels (Tamiasciurus hudsonicus) we intensively sampled the size and spatial dispersion of hoards. Single-item and large hoards were far more prevalent than expected by chance (Figs. 1 and 2) and appeared to be distinct components of the hoarding tactic employed in this population. Scattered single-item hoards represented more than half of all hoards constructed and approximately one-fifth of all cones stored. Large hoards (> 10 cones) comprised less than 15% of all hoards, and about 50% of all cones stored. In response to experimental manipulations, squirrels altered their hoarding behaviour in order to concentrate cones in the litter and brush heaps we provided, but still scattered a large proportion of their stores. We conclude that hoarding patterns in red squirrels are more variable and plastic than has previously been recognized, and discuss this variability in terms of adaptive explanations. Offprint requests to: R.J. Robertson     

Germination and seedling growth of the water cress Rorippa sp. exposed to the chelant [S,S]-EDDS

With the implementation of the new EU environmental framework directives, high tier risk assessments of chemicals will be increasingly needed. For high production chemicals, additional tests will complement the standard battery for aquatic toxicity assessments (daphnids, algae, and fish). In the context of a new chemical notification at the European Union level, we have developed a seed germination and root elongation toxicity test with the freshwater aquatic plant Rorippa nasturtium-aquaticum (water cress) to confirm the low environmental risk of the chelant [S,S]-EDDS. A 14 day semi-static growth inhibition test was conducted with daily renewal of the test solution. No concentration related inhibition was found on the basis of any of the criteria investigated, i.e., time and extent of germination, biomass, number of leaves, stalk and root lengths. The no-observed effect concentration was considered to be >or=387 mg SS-EDDS/l. Although germination was selected as an appropriate endpoint to assess the effect of a chelant on an aquatic plant (other endpoints would have been dependant on essential metals that are chelated in standard culture tests), the absence of dose related effects requires further tests with higher exposure concentrations and/or other toxicant(s) to assess the validity of the test as a general tool for aquatic risk assessment.     

A framework for understanding ecological traps and an evaluation of existing evidence

When an animal settles preferentially in a habitat within which it does poorly relative to other available habitats, it is said to have been caught in an "ecological trap." Although the theoretical possibility that animals may be so trapped is widely recognized, the absence of a clear mechanistic understanding of what constitutes a trap means that much of the literature cited as support for the idea may be weak, at best. Here, we develop a conceptual model to explain how an ecological trap might work, outline the specific criteria that are necessary for demonstrating the existence of an ecological trap, and provide tools for researchers to use in detecting ecological traps. We then review the existing literature and summarize the state of empirical evidence for the existence of traps. Our conceptual model suggests that there are two basic kinds of ecological traps and three mechanisms by which traps may be created. To this point in time, there are still only a few solid empirical examples of ecological traps in the published literature (although those few examples suggest that both types of traps and all three of the predicted mechanisms do exist in nature). Therefore, ecological traps are either rare in nature, are difficult to detect, or both. An improved library of empirical studies will be essential if we are to develop a more synthetic understanding of the mechanisms that can trigger maladaptive behavior in general and the specific conditions under which ecological traps might occur.     

Evaluation of approaches for terrestrial hazard classification

Hazard assessment is an essential element in the evaluation of the potential effects of chemical substances on the environment. To date, most work has focused on hazard assessment schemes for the aquatic environment, but in recent years, a number of proposals have been developed for other environmental compartments. Due to limited datasets, the suitability of the toxicity cut-off values in these schemes has not been fully determined and the practicalities associated with using these approaches have not been fully established. This study, which focused on the soil compartment, was performed to examine cut-off values proposed by two terrestrial hazard assessment schemes and establish the availability of data. Data on earthworms indicated that current proposals for toxicity cut-off values are appropriate. However, analysis of IUCLID (International Uniform ChemicaL Information Database) indicates that even for commonly used high production volume chemicals, insufficient data are available to enable classification. Whilst the necessary data may already be available for selected groups of substances (e.g. pesticides and veterinary medicines), a significant experimental testing programme would therefore be required before a terrestrial classification system could be applied widely. Such data may become available in the future as a result of initiatives such as REACH.     

Paternity and performance of golden-winged warblers (<Emphasis Type="Italic">Vermivora chrysoptera</Emphasis>) and golden-winged X blue-winged warbler (<Emphasis Type="Italic">V. pinus</Emphasis>) hybrids at the leading edge of a hybrid zone

We examined two components of reproduction in a population of golden-winged warblers in the initial stages of hybridization with blue-winged warblers. First, we used genetic analyses of mate choice to determine whether copulations outside the social pairbond (extra-pair copulations; EPCs) occur in these species and their hybrids. Second, we compared several aspects of reproduction (pairing success, clutch size, hatching success, fledging success, and loss of paternity) in nests raised by phenotypic golden-winged warblers to those raised by hybrid individuals. Together, these data provide us with the first quantitative analysis of reproduction within this hybrid system. Our data suggest several reasons why the level of hybridization between these species is likely being underestimated. First, many birds in our population showed only subtle phenotypic signs of introgression indicating that hybrid status can only be determined by close examination. Second, high rates of extra-pair paternity indicate that we cannot base our estimates of hybridization on pairbond data alone. More than 30% of nestlings were the result of EPCs, occurring in 55% of all nests. Third, there was no difference in the number of hybrid or “pure” golden-winged warbler males chosen as social mates, relative to their abundance. Indeed, based on several components of nesting success, it appears as though hybrids are having as great realized reproductive success as are phenotypic golden-winged warblers in our population. Accordingly, we argue that hybrid reproductive success and extra-pair fertilizations are likely playing a major role in the ongoing hybridization between blue-winged and golden-winged warblers. Studies such as this one are important to our understanding of the process and implications of hybridization, and findings may be applicable to other hybrid zones.     

“Killing them with kindness”? A study of service employees' responses to uncivil customers

Experiencing uncivil customers is a frequent reality for many people working in the service industry. Past research has established that dealing with uncivil customers can be distressing for employees and can sometimes lead them to engage in reciprocal, discourteous behavior. The purpose of our research is to delve deeper into the experience of customer incivility from the perspective of service employees in order to better understand the various ways in which they respond to customer incivility. We conducted 64 interviews with service employees across an array of occupations and developed a typology of responses to customer incivility. These responses fell into four categories based on the extent to which service employees' actions were intended to promote social harmony (and therefore could broadly be considered civil or uncivil), as well as their perceived agency in the situation. We describe how each response was associated with different interpersonal and intrapersonal consequences and explain the implications of our typology for management theory and practice.     

Multi-model vs. EPS-based ensemble atmospheric dispersion simulations: A quantitative assessment on the ETEX-1 tracer experiment case

Several techniques have been developed over the last decade for the ensemble treatment of atmospheric dispersion model predictions. Among them two have received most of the attention, the multi-model and the ensemble prediction system (EPS) modeling. The multi-model approach relies on model simulations produced by different atmospheric dispersion models using meteorological data from potentially different weather prediction systems. The EPS-based ensemble is generated by running a single atmospheric dispersion model with the ensemble weather prediction members. In the paper we compare both approaches with the help of statistical indicators, using the simulations performed for the ETEX-1 tracer experiment. Both ensembles are also evaluated against measurement data. Among the most relevant results is that the multi-model median and the mean of EPS-based ensemble produced the best results, hence we consider a combination of multi-model and EPS-based approaches as an interesting suggestion for further research.     

Dietary antioxidants (selenium and N-acetylcysteine) modulate paraoxonase 1 (PON1) in PCB 126-exposed rats

Environmental pollutants polychlorinated biphenyls (PCBs), especially dioxin-like PCBs, cause oxidative stress and associated toxic effects, including cancer and possibly atherosclerosis. We previously reported that PCB 126, the most potent dioxin-like PCB congener, not only decreases antioxidants such as hepatic selenium (Se), Se-dependent glutathione peroxidase, and glutathione (GSH) but also increases levels of the antiatherosclerosis enzyme paraoxonase 1 (PON1) in liver and serum. To probe the interconnection of these three antioxidant systems, Se, GSH, and PON1, we examined the influence of varying levels of dietary Se and N-acetylcysteine (NAC), a scavenger of reactive oxygen species (ROS) and precursor for GSH synthesis, on PON1 in the absence and presence of PCB 126 exposure. Male Sprague–Dawley rats, fed diets with differing Se levels (0.02, 0.2, or 2 ppm) or NAC (1 %), were treated with a single intraperitoneal injection of corn oil or various doses of PCB 126 and euthanized 2 weeks later. PCB 126 significantly increased liver PON1 mRNA, protein level and activity, and serum PON1 activity in all dietary groups but did not consistently increase thiobarbituric acid levels (thiobarbituric acid reactive substances, TBARS), an indicator of lipid oxidation and oxidative stress, in liver or serum. Inadequate (high or low) dietary Se decreased baseline and PCB 126-induced aryl hydrocarbon receptor (AhR) expression but further increased PCB 126-induced cytochrome P450 1A1 (CYP1A1) expression, the enzyme believed to be the cause for PCB 126-induced oxidative stress. In addition, a significant inverse relationship was observed not only between dietary Se levels and PON1 mRNA and PON1 activity but also with TBARS levels in the liver, suggesting significant antioxidant protection from dietary Se. NAC lowered serum baseline TBARS levels in controls and increased serum PON1 activity but lowered liver PON1 activities in animals treated with 1 μmol/kg PCB 126, suggesting antioxidant activity by NAC primarily in serum. These results also show an unexpected predominantly inverse relationship between Se or NAC and PON1 during control and PCB 126 exposure conditions. These interactions should be further explored in the development of dietary protection regimens.     

Extra-pair paternity and the reproductive role of male floaters in the tree swallow (Tachycineta bicolor)

In many avian species, a part of the population is present at the breeding grounds but does not breed. Current theories generally assume that floaters are younger or lower-quality individuals, and empirical data confirm this. However, floating could also arise as an alternative strategy to breeding, if floaters are able to reproduce via extra-pair copulations. Until the present study, there has been no evidence that floaters father offspring. We studied a population of tree swallows (Tachycineta bicolor), a species with one of the highest levels of extra-pair paternity known in birds. Using microsatellite markers, we determined the biological fathers of 65% of the extra-pair young. Of a total of 53 extra-pair young (52% of all offspring), 47% were fathered by local residents, 6% by residents breeding elsewhere (up to 2 km from the focal grid), and 13% by floaters. Residents seemed to be more successful and they were also more likely to return as territory holders in the next breeding season compared to floaters. Extra-pair males were on average in better condition than the within-pair males they cuckolded. Interestingly, resident males that disappeared (possibly to float) during the fertile period were heavier than males that stayed, and floaters were heavier than residents, but not different in any other characteristic. Although alternative interpretations of the data are possible, we propose that floating might be a conditional strategy in tree swallows whereby males in good condition gain more paternity via extra-pair copulations, whereas males in worse condition are more successful by providing parental care.