Ranging behavior of the mountain gorillas (Gorilla beringei beringei) in Bwindi Impenetrable National Park, Uganda: a test of the ecological constraints model

The ecological constraints model predicts that daily travel distance and home range size of social animals will increase as group size increases in order to meet the dietary needs of additional group members. This theory has been supported more predominantly by studies of frugivorous primate species than by studies of folivorous species. We examined the ranging patterns of mountain gorillas in Bwindi Impenetrable National Park, Uganda, who include both herbaceous vegetation and fruit in their diet, to determine how ecological, behavioral, and social parameters influence movement patterns. Data were collected from three groups of gorillas with overlapping home ranges at a low-altitude location (1,450–1,800 m) and one group at a high-altitude location (2,100–2,500 m) in Bwindi from September 2001 to August 2002. We analyzed daily travel distance and home range size in relation to group size, while also considering patterns of frugivory, rainfall, and location (proxy for food availability) within the park. Both daily travel distance and home range size were positively related to group size. In addition, the degree of frugivory positively influenced daily travel distance and home range size, while rainfall negatively influenced daily travel distance only. Finally, groups at the low-altitude location, with higher fruit availability, traveled less than the group at the high-altitude location. These results demonstrate that mountain gorillas in Bwindi provide support for the ecological constraints model, but further studies are needed to determine how fine-scale spatial and temporal availability of food resources influence movement patterns. Ranging patterns of Bwindi gorillas are compared to those observed in other gorilla populations in the context of the ecological constraints model.Communicated by D. Watts     

Food sharing among retaliators: sequential arrivals and information asymmetries

Many animals share food, that is, to tolerate competitors at a defensible clump. Most accounts of resource sharing invoke special evolutionary processes or ecological circumstances that reduce their generality. Surprisingly, the Hawk–Dove game has been unable to address in a simple and general way why so many group foraging animals share food. We modify the Hawk–Dove game by allowing a finder the opportunity of retaliating if joiners escalate and by considering the consequences of information asymmetries concerning resource value among players. Introducing the first change, the retaliator strategy was sufficient to predict widespread sharing in habitats where food clumps are of intermediate richness. When information asymmetry between finder and joiner is created by allowing the quality of clumps to vary, we show that the conditions for sharing are even more easily met and apply to a wider range of resource qualities. Our model therefore offers one of the most parsimonious and potentially general evolutionary accounts of the origin of non-aggressive resource sharing.     

Food supply during prelaying period modifies the sex-dependent investment in eggs of Eurasian kestrels

The theory of sex allocation suggests that if the reproductive value and the cost of producing/rearing offspring differ between male and female offspring, parents should invest differently in sexes depending on environmental conditions. Female parents could allocate more resources to eggs of one sex to compensate potential sex-dependent constraints later during the nestling period. In this study, we tested the influence of environmental conditions on sexual dimorphism in eggs of Eurasian kestrels (Falco tinnunculus) by experimentally manipulating food availability before laying. We found that an increase in food abundance before laying did not increase egg mass but changed sex-dependent resource distribution in eggs. In food-supplemented pairs, but not in control pairs, egg mass and hatchling mass were similar between males and females. In addition, we found, in the food-supplemented group, that the latest hatched females showed shorter hatching times than in the control group. In control pairs, female eggs, hatchlings and nestlings were heavier than males. In addition, male fledglings in the food-supplemented group gained less mass than those in the control group. As that food abundance was only increased until the onset of laying, female kestrels were expected to invest in eggs taking food abundance before egg formation as a predictor of future conditions during brood rearing. Our study shows that environmental conditions before laying promote a subtle adjustment of the resources invested in both sexes of offspring rather than in other breeding parameters. This adjustment resulted in a shortening of hatching time of the last hatched females that possibly gives them advantages in their competitive capacity with respect to male nest-mates.     

Food availability,intrusion pressure and territory size: an experimental study of Anna's hummingbirds (Calypte anna)

Theoretical considerations implicate food availability and intrusion pressure as important determinants of territory size, but empirical studies have led to contradictory conclusions about cause-and-effect relationships among these three variables. To investigate this problem, we provided patches of electronically controlled artificial flowers, which were defended by male Calypte anna. Food availability was experimentally manipulated, and intrusion rate and territory size were calculated from behavioral observations of the territory owner. Changes in both food availability and intrusion rate were found to be significantly correlated with changes in territory size under certain conditions. Intrusion rate, which was influenced by food availability, was negatively associated with territory size so long as food availability was high. This association persisted even after possible effects of food availability were controlled statistically. Food availability was negatively correlated with territory size only when intrusion rates were high and after owners had been defending territories for 3 days. As food availability and intrusion rate increased, owners increasingly restricted their defense to the patch itself; partial regressions revealed a significant association for intrusion rate but not food availability. When intrusion rate was low and food availability varied from low to high levels, no relationship was observed between food availability and territory size, apparently because of opposing influences of food abundance on territory size. Correspondence to: P.W. Ewald     

Blue water scarcity in the Black Sea catchment: Identifying key actors in the water-ecosystem-energy-food nexus

Large-scale water scarcity indicators have been widely used to map and inform decision makers and the public about the use of river flows, a vital and limited renewable resource. However, spatiotemporal interrelations among users and administrative entities are still lacking in most large-scale studies. Water scarcity and interrelations are at the core of the water-ecosystem-energy-food nexus. In this paper, we balance water availability in the Black Sea catchment with requirements and consumptive use of key water users, i.e., municipalities, power plants, manufacturing, irrigation and livestock breeding, accounting for evaporation from major reservoirs as well as environmental flow requirements. We use graph theory to highlight interrelations between users and countries along the hydrological network. The results show that water scarcity occurs mainly in the summer due to higher demand for irrigation and reservoir evaporation in conjunction with relatively lower water resources, and in the fall-winter period due to lower water resources and the relatively high demand for preserving ecosystems and from sectors other than irrigation. Cooling power plants and the demands of urban areas cause scarcity in many isolated locations in the winter and, to a far greater spatial extent, in the summer with the demands for irrigation. Interrelations in water scarcity-prone areas are mainly between relatively small, intra-national rivers, for which the underlying national and regional governments act as key players in mitigating water scarcity within the catchment. However, many interrelations exist for larger rivers, highlighting the need for international cooperation that could be achieved through a water-ecosystem-energy-food nexus.     

Application of a Swab Sampling Method for the Detection of Norovirus and Rotavirus on Artificially Contaminated Food and Environmental Surfaces

Noroviruses and rotaviruses are the leading causes of non-bacterial gastroenteritis in humans worldwide. Virus-contaminated food and surfaces represent an important risk to public health. However, established detection methods for the viruses in food products are laborious and time-consuming. Here, we describe a detailed swabbing protocol combined with real-time RT-PCR for norovirus and rotavirus detection on artificially contaminated food and environmental surfaces. Recovery rates between 2 and 78% for norovirus and between 8 and 42% for rotavirus were determined for contaminated food surfaces of apple, pepper, cooked ham and salami. From contaminated environmental surfaces (stainless steel, ceramic plate, polyethylene, wood), recovery rates between 26 and 52% (norovirus) and between 10 and 58% (rotavirus) were determined. The results demonstrate the suitability of the swab sample method for virus detection on food and environmental surfaces. Compared to other methods, it is easy to perform and significantly time-saving, predestining it for routine testing.     

Environmental impact of packaging and food losses in a life cycle perspective: a comparative analysis of five food items

The environmental concern and development issues regarding packaging has for 20 years to a high extent been on packaging when it has become waste. To reduce the environmental impact from the whole food packaging system it is also important to develop the packaging’s ability to reduce food waste. In some cases it may be necessary to increase the environmental impact of packaging in order to reduce food waste. In this paper, the environmental impact of packaging and food losses and the balance between the two has been examined for five different food items. The results show that packaging’s that reduce food waste can be an important tool to reduce the total environmental impact, even if there is an increase in impact from the packaging itself. This is especially true for food items where the environmental impact of the food is high relative the packaging, for example cheese, and for food items with high losses, for example bread. It is important to analyse the risk of increasing food losses when packaging design changes, for example, when the aim is less packaging material, which is the main intention of the packaging and packaging waste directive of the European Union.     

Modeling individual and population dynamics in a consumer–resource system: Behavior under food limitation and crowding and the effect on population cycling in Daphnia

In population modeling, a considerable level of complexity is often required to provide trustworthy results, comparable with field observations. By assuring sufficient detail at the individual level while preserving the potential to explore the consequences at higher levels, individual-based modeling may thus provide a useful tool to investigate dynamics at different levels of organization. Still, population dynamics resulting from such models are often at odds with observations from the field. This may be partly caused by a lack of focus on the individual dynamics under conditions of food stress and starvation. I developed a physiologically structured, individual-based simulation model to investigate life history of Daphnia and its effect on population dynamics in response to the productivity of the system. In verifying model behavior with available literature data on life history and physiology, I paid special attention to the dynamics of food intake and the verification of individual level results under conditions of food limitation and starvation. I show that the maximum filtering rates under low food levels used in the current model are much closer to measured filtering rates than the ones used in other models. Being consistent with results on physiology and life history from experiments at a wide range of food availability (including starvation), the model generates low amplitude or high amplitude population density cycles depending on the productivity of the system, as observed in field and experimental populations of Daphnia and with the minimum population densities being one to two orders of magnitude lower in the high amplitude than in the low amplitude cycles. To generate results which are not only qualitatively but also quantitatively comparable to experimental and field observations, however, a crowding effect on the filtering response has to be incorporated in the model.     

Bioconcentration factors of mercury by Parasol Mushroom (Macrolepiota procera)

To examine bioconcentration factors (BCFs) of mercury by Parasol Mushroom (Macrolepiota procera) roughly similarly sized (a cap diameter) fruiting bodies of this fungus and underlying soil (0–10 cm) samples were collected at 15 sites in Poland between 1995 and 2003. The total mercury content of the individual caps and stipes of Parasol Mushroom ranged from 0.05 to 22 mg Hg/kg dry matter (d.m.) and from 0.05 to 20 mg Hg/kg d.m., while the means were from 1.1 to 8.4 mg Hg/kg d.m. and from 0.83 to 6.8 mg Hg/kg d.m., respectively. The caps generally contained higher concentrations of mercury when compared to stipes, and the means of the cap to stipe mercury concentration quotient ranged from 1.3 to 4.6. The range of mercury concentration in topsoil samples collected at the sites where the fruiting bodies were collected was from 0.01 to 0.54 mg/g d.m. (means ranged from 0.022 to 0.36 mg/g d.m.). The BCFs factors for total mercury varied from 0.52 to 470 for individual caps and 0.52 to 360 for stipes, while average values, depending on the site, were from 16 to 220 and from 7.6 to 130 for caps and stipes, respectively.     

Adaptations in a hierarchical food web of southeastern Lake Michigan

Two issues in ecological network theory are: (1) how to construct an ecological network model and (2) how do entire networks (as opposed to individual species) adapt to changing conditions? We present a novel method for constructing an ecological network model for the food web of southeastern Lake Michigan (USA) and we identify changes in key system properties that are large relative to their uncertainty as this ecological network adapts from one time point to a second time point in response to multiple perturbations. To construct our food web for southeastern Lake Michigan, we followed the list of seven recommendations outlined in Cohen et al. [Cohen, J.E., et al., 1993. Improving food webs. Ecology 74, 252–258] for improving food webs. We explored two inter-related extensions of hierarchical system theory with our food web; the first one was that subsystems react to perturbations independently in the short-term and the second one was that a system's properties change at a slower rate than its subsystems’ properties. We used Shannon's equations to provide quantitative versions of the basic food web properties: number of prey, number of predators, number of feeding links, and connectance (or density). We then compared these properties between the two time-periods by developing distributions of each property for each time period that took uncertainty about the property into account. We compared these distributions, and concluded that non-overlapping distributions indicated changes in these properties that were large relative to their uncertainty. Two subsystems were identified within our food web system structure (p < 0.001). One subsystem had more non-overlapping distributions in food web properties between Time 1 and Time 2 than the other subsystem. The overall system had all overlapping distributions in food web properties between Time 1 and Time 2. These results supported both extensions of hierarchical systems theory. Interestingly, the subsystem with more non-overlapping distributions in food web properties was the subsystem that contained primarily benthic taxa, contrary to expectations that the identified major perturbations (lower phosphorous inputs and invasive species) would more greatly affect the subsystem containing primarily pelagic taxa. Future food-web research should employ rigorous statistical analysis and incorporate uncertainty in food web properties for a better understanding of how ecological networks adapt.