Den Ecology of the Arctic Fox Alopex lagopus beringensis (Carnivora,Canidae) on Bering Island,Commander Islands

The spatial distribution of 33 Arctic fox dens on Bering Island was studied, and a relationship between the burrowing activity of Arctic foxes and the pattern of vegetation near their dens was revealed. This activity was shown to change the structure of the plant cover, with the degree of change depending on the type of biotope.     

Spillover of Agriculturally Subsidized Predators as a Potential Threat to Native Insect Herbivores in Fragmented Landscapes

Abstract:  Habitat loss and fragmentation can have strong negative impacts on populations of some native species. Spillover of generalist natural enemies from the surrounding landscape matrix is one mechanism potentially generating such effects, yet this has been rarely studied in insects. We examined the influence of habitat conversion to agriculture on the abundance and potential effects of predatory coccinellid beetles on native insect herbivores within 12 grassland remnants in central Nebraska (U.S.A.). Results of sweep sampling revealed that coccinellids were three to six times more abundant at native grassland sites embedded within cropland-dominated landscapes compared with control sites in grassland-dominated landscapes over the 3 years of the study. Exclusion experiments further demonstrated that predation intensity was strongly related to coccinellid abundances across sites and that coccinellids can dramatically reduce densities of a native aphid herbivore. In contrast to studies of specialized insect parasitoids, which have generally found reduced enemy pressure in fragmented landscapes, our results suggest that native herbivores may in some cases experience increased consumer pressure in landscapes with increasing habitat loss because of spillover of generalist predators from surrounding cropland habitats.     

Shell acquisition by hermit crabs: which tactic is more efficient?

Gastropod shells are limited resources for most hermit crab species, acting as primary factors in various aspects of their biology. To investigate the efficacy of different behavioral tactics adopted for their acquisition (locomotion, attendance at shell-supplying sites, interactions with conspecifics in aggregation) we conducted observations and experiments at a salt marsh in New England (USA). Locomotion, fast and meandering, significantly increased the chances of encountering empty shells and conspecifics. However, shell exchanges were rare. Simulated gastropod predation sites quickly attracted a larger number of hermit crabs than the other shell-supplying sites tested (live and dead conspecifics, live snails) and induced the rapid occupancy of all the empty shells offered, usually by the first crabs arriving at the site. Aggregations seemed not to function as shell exchange markets, as previously suggested for several other species. In the short run, exploitation seems to be more efficient for the acquisition of new shells by Pagurus longicarpus. In the long run, it is the density of nondestructive gastropod predators that regulates the availability of new shells of good quality in the pool available to this hermit crab species.     

Pre-ingestive treatment of bombardier beetles by jays: food preparation by “anting” and “sand-wiping”

Summary. Evidence is presented, obtained with two species of jays, that these birds differ in the ways in which they prepare bombardier beetles for ingestion. Blue Jays subject bombardiers to “anting,” a procedure by which the beetles are induced to eject their spray into the plumage of the birds. Florida Scrub Jays, in contrast, which live in an area where the soil is sandy, subject bombardiers to “sand-wiping,” causing the beetles to eject their spray into the substrate. Both strategies lend themselves also to pre-ingestive treatment of other chemically protected arthropods. Anting is a strategy widely practiced by birds, possibly because it can be put to use no matter what the nature of the terrain. Sand-wiping, as implied by its name (which we here coin), may be of more restricted occurrence, given that it can be carried out only on loose, penetrable soil.     

Variable predation risk and the dynamic nature of mosquito antipredator responses to chemical alarm cues

Summary. Predation is a pervasive selective agent highly variable in space and time. Due to the costs associated with antipredator responses, prey would be at a selective advantage if they respond to predation threats with an intensitfy matching the threat posed by the predator. Many aquatic organisms have been shown to use chemical alarm cues present in the water to assess the level of risk in their environment. This includes mosquito larvae which show antipredator responses to conspecific alarm cues. In this study, we investigated the nature of the responses of larval mosquitoes Culex restuans to those cues. In our initial observations, we showed pond/population differences in the response intensity of C. restuans to alarm cues. In experiment 1, we showed that the response intensity to alarm cues could be increased by increasing the background level of risk in the mosquitoes’ environment (by adding salamander predators) and once turned on, the response intensity to alarm cues was likely maintained for the remainder of the mosquitoes’ aquatic life. In experiments 2 and 3, we investigated if the increase in response intensity to alarm cues was directly correlated with the level of background risk in the mosquitoes’ environment. When given increasing levels of background risk, mosquito larvae subsequently showed a graded response to conspecific alarm cues. This series of experiments demonstrates that the response intensity of larval mosquitoes to a standard concentration of alarm cues is not fixed, but rather dependent on the background level of risk in the environment. An understanding of the background level of risk is particularly important for comparing antipredator responses of prey between habitats.     

Edge Effects in the Great Tit: Analyses of Long-term Data with GIS Techniques

Abstract:  In contemporary fragmented landscapes, edges are commonplace, and understanding the effects of edge environments is thus essential for the conservation of forest communities. The reproductive output of forest passerines is often reduced close to forest edges. Possible explanations include overcrowding by conspecifics, elevated rates of predation, and the occurrence of lower-quality habitat and/or individuals at forest edges. We attempted to separate these processes by examining edge effects in the absence of nest predation and by effectively controlling for differences in breeding density and the quality of habitats and individuals. We used an edge distance index (EDI), which accounts for the number and distribution of edges in close proximity to a breeding location, to help explain variation in breeding density, nesting success, and reproductive traits of 8308 pairs of Great Tits ( Parus major ) breeding between 1965 and 2005, in Wytham, near Oxford, United Kingdom. Results from linear mixed modeling confirmed higher breeding density and a higher proportion of immigrant individuals at forest edges. Nevertheless, independently of these effects, we also found that birds laying later, with smaller clutches but larger eggs, were typical of edge environments. The number of offspring recruited to the breeding offspring per breeding attempt was also reduced at edges, both directly and mediated through changes in clutch size and laying date. Edge effects on life histories were detectable within individual females and up to 500 m from the woodland edge. Woodland edges are increasingly common in contemporary fragmented landscapes. Therefore these results, which suggest a pervasive effect of edges on reproduction, are of considerable importance to the management and conservation of forest communities.     

The role of life histories and trophic interactions in population recovery

Factors affecting population recovery from depletion are at the focus of wildlife management. Particularly, it has been debated how life‐history characteristics might affect population recovery ability and productivity. Many exploited fish stocks have shown temporal changes towards earlier maturation and reduced adult body size, potentially owing to evolutionary responses to fishing. Whereas such life‐history changes have been widely documented, their potential role on stock's ability to recover from exploitation often remains ignored by traditional fisheries management. We used a marine ecosystem model parameterized for Southeastern Australian ecosystem to explore how changes towards “faster” life histories might affect population per capita growth rate r. We show that for most species changes towards earlier maturation during fishing have a negative effect (3–40% decrease) on r during the recovery phase. Faster juvenile growth and earlier maturation were beneficial early in life, but smaller adult body sizes reduced the lifetime reproductive output and increased adult natural mortality. However, both at intra‐ and inter‐specific level natural mortality and trophic position of the species were as important in determining r as species longevity and age of maturation, suggesting that r cannot be predicted from life‐history traits alone. Our study highlights that factors affecting population recovery ability and productivity should be explored in a multi‐species context, where both age‐specific fecundity and survival schedules are addressed simultaneously. It also suggests that contemporary life‐history changes in harvested species are unlikely to increase their resilience and recovery ability.     

Reduced Density and Nest Survival of Ground‐Nesting Songbirds Relative to Earthworm Invasions in Northern Hardwood Forests

Abstract: European earthworms (Lumbricus spp.) are spreading into previously earthworm‐free forests in the United States and Canada and causing substantial changes, including homogenization of soil structure, removal of the litter layer, and reduction in arthropod abundance and species richness of understory plants. Whether these changes affect songbirds that nest and forage on the forest floor is unknown. In stands with and without earthworms in the Chequamegon‐Nicolet National Forest, Wisconsin (U.S.A.), we surveyed for, monitored nests of, and measured attributes of habitat of Ovenbirds (Seiurus aurocapillus) and Hermit Thrushes (Catharus guttatus), both ground‐dwelling songbirds, and we sampled earthworms at survey points and nests. Bird surveys indicated significantly lower densities of Ovenbirds and Hermit Thrushes in relation to Lumbricus invasions at survey point and stand extents (3.1 and 15–20 ha, respectively). Modeling of Ovenbird nest survival (i.e., the probability that nestlings successfully fledge) indicated that lower survival probabilities were associated with increased sedge cover and decreased litter depth, factors that are related to Lumbricus invasions, possibly due to reduced nest concealment or arthropod abundance. Our findings provide compelling evidence that earthworm invasions may be associated with local declines of forest songbird populations.     

The role of psychology in determining human–predator conflict across southern Kenya

Conflict between people and carnivores can lead to the widespread killing of predators in retaliation for livestock loss and is a major threat to predator populations. In Kenya, a large, rural, pastoralist population comes into regular conflict with predators, which persist across southern Kenya. We explored the social and psychological backdrop to livestock management practices in this area in a process designed to be easy to use and suitable for use across large areas for the study of conflict and transboundary implementation of wildlife conflict reduction measures, focusing on community involvement and needs. We carried out fully structured interviews of livestock managers with a survey tool that examined how social and psychological factors may influence livestock management behavior. We compared survey responses on 3 sites across the study area, resulting in 723 usable responses. Efficacy of individuals’ livestock management varied between and within communities. This variation was partially explained by normative and control beliefs regarding livestock management. Individual livestock managers’ self-reported management issues were often an accurate reflection of their practical management difficulties. Psychological norms, control beliefs, and attitudes differed among sites, and these differences partially explained patterns associated with conflict (i.e., variation in livestock management behavior). Thus, we conclude that a one-size-fits-all approach to improving livestock management and reducing human–predator conflict is not suitable.     

3种生物处理方式对污泥减量效果的比较及优化

通过间歇试验得到3种生物方式(污泥好氧消化、厌氧消化以及颤蚓摄食)对污泥的比减量速率、污泥减量速率和污泥减量比例.当初始污泥浓度为2 500mg·L^-1时,经过24h减量,颤蚓摄食、厌氧消化和好氧消化3种方式对污泥的比减量速率R分别为0.13 mg·(mg·d)^-1,0.09 mg·(mg·d)^-1和0.03 mg·(mg·d)^-1,对污泥的减量速率分别为315 mg·(L·d)^-1,263mg·(L·d)^-1和65 mg·(L·d)^-1.通过细菌荧光染色和脱氢酶活性检测证实颤蚓摄食在短时间内对污泥中细菌细胞膜的破坏程度最大,可以将颤蚓摄食和厌氧消化相组合强化对污泥的减量.对于初始浓度为2 500mg·L^-1的污泥,颤蚓摄食12h后再厌氧消化36h,可以在2d左右使污泥减量的比例达到30%,减量比速率为0.25 mg·(mg·d)^-1.当初始污泥浓度增加到4 240mg·L^-1,颤蚓摄食时间需要延长到24h方能保证组合工艺对污泥最大程度地减量.