Diet composition and foraging activity of <Emphasis Type=Italic>Pipistrellus pygmaeus</Emphasis> in a floodplain forest

In 2000–2002 bat droppings were collected under the emerging crevice of a nursery colony of Pipistrellus pygmaeus. The locality was situated in a floodplain forest at the confluence of the Dyje and Morava rivers (S Moravia, Czech Republic). In total, 27 samples (20 pellets in one sample) of droppings were used to analyze prey remains. In the diet, 40 taxonomic groups of invertebrates were found. As expected, small dipteran insects were the main food item in which Nematocera dominated. Besides Chironomidae and Ceratopogonidae also a high percentage of nematoceran eggs were recorded. Surprisingly, a relatively high percentage of Brachycera was recorded. Further frequent prey items belonged to the orders of Trichoptera, Hymenoptera, Coleoptera and Sternorrhyncha. A heterodyne bat detector was used to follow foraging activity of P. pygmaeus on line transects in forest and water habitats in the vicinity of the colony. A significant decrease in foraging activity over water habitats and in forest sites during the late pregnancy (mid-May — early June) and an increase during the lactation and post-lactation periods (mid-June — early August) were found. Changes in the frequency of occurrence of Chironomidae, Neuroptera, Trichoptera, Aphidinea and Simuliidae were correlated with the bats’ foraging activity.     

Honey bee orientation behaviour and the influence of flower distribution on foraging movements

ABSTRACT.

• 1 Directional movement by foraging honey bees (Apis mellifera L.) was studied on several flower arrays. The most frequent move among equidistant flower stalks was straight ahead from stalk to stalk with frequencies decreasing for increasing turn angles. Turns to the left were about equal in frequency to turns to the right.
• 2 Bees maintained directionality when moving from flower stalks that had been rotated 90° counterclockwise while the bee was on the stalk (no difference between moves from rotated stalks and unrotated controls). Thus, directionality is maintained by the bee and is not an artefact of flower distribution.
• 3 Bees also maintained directionality when the entire array was rotated around the flower stalk the bee was on. Thus, bees use an external cue to orientate in a given direction rather than fixing on an inflorescence within the flower array.
• 4 Bees foraging on very different flower arrays differed in patterns of directionality and in distances flown between flower stalks. Therefore, even though bees maintain directionality using external cues, flower distribution can nevertheless influence flight patterns.

     

Influences of aquatic macrophytes on invertebrate community structure,guild structure,and microdistribution in streams

The aquatic macrophytes Ranunculus aquatilis and Rorippa nasturtium-aquaticum were transplanted into substrate trays and placed in a stream alongside unvegetated substrate. Macrophytes were observed to have significant effects on 1) invertebrate community structure, 2) guild structure, and 3) microdistribution. 1) Significantly higher taxa richness and community abundances were associated with macrophytes. 2) Significantly higher abundances of shredder, scraper, and predator guilds were associated with macrophytes in fall, and all guilds had higher abundances in macrophytes in spring. However, guild frequency distributions did not differ among habitats except in spring. 3) Enallagma, Gammarus, Gyraulus, Physa, and Pisidium exhibited a strong association with macrophytes, while Hydropsyche, Simulium, Baetis tricaudatus, Glossosoma velona, and Helicopsyche borealis appeared to avoid them. A strong correlation appeared to exist between current velocity preferences of these taxa and their selection or avoidance of vegetated habitat. Thus, the effect of macrophytes in reducing current velocities appeared to be the most important influence on invertebrate microdistribution. However, macrophytes also increase physical heterogeneity and their large surface areas benefit invertebrate community abundances by creating additional living spaces in the water column where none exist above unvegetated substrate.     

Temporal variation in foraging group structure of a size-structured stream fish community

Temporal variation in foraging group structure of a fish assemblage was examined in a flood-prone stream in southern Hokkaido, Japan. Foraging behaviour was observed underwater for four species which inhabit the water column: ayu, Plecoglossus altivelis, white-spotted charr, Salvelinus leucomaenis, masu salmon, Oncorhynchus masou, and Japanese dace, Tribolodon hakonensis, with each species being categorized into five size classes (species-size group; SSG). Based on foraging behaviour, each SSG of the fish assemblage was classified into one of four foraging groups: algae grazers, drift foragers, benthos-drift foragers, and omnivores, defined as SSG exhibiting similar foraging behaviour. All size classes of ayu, and of charr and salmon were categorized as algae grazers and drift foragers, respectively, throughout the study period. In contrast, size classes of dace were categorized as drift foragers, benthos-drift foragers, or omnivores with the same size classes often assigned to different foraging groups from month to month. Digestive tract contents of the fishes in the four foraging groups reflected their observed foraging behaviour, and foraging groups were therefore regarded as representing trophic groups. Abundance and membership of each foraging group varied in accordance with changes in abundance of SSG due to their growth, immigration, emigration, and/or mortality. Moreover, due to numerical dominance within the assemblage, plasticity in foraging behaviour of small- and medium-sized dace also played a key role in determining variability in the foraging group structure. Relative frequencies of two types of foraging behaviour, algae nipping and benthos foraging, of the small-sized dace were significantly correlated with the level of each resource, whereas no significant relationship was detected between foraging frequencies of the medium-sized dace and either resource. Fluctuations in foraging group structure within this assemblage occurred through niche shifts of some component members and by changes in SSG composition.     

Optimal foraging and community structure: implications for a guild of generalist grassland herbivores

Summary A particular linear programming model is constructed to predict the diets of each of 14 species of generalist herbivores at the National Bison Range, Montana. The herbivores have body masses ranging over seven orders of magnitude and belonging to two major taxa: insects and mammals. The linear programming model has three feeding constraints: digestive capacity, feeding time and energy requirements. A foraging strategy that maximizes daily energy intake agrees very well with the observed diets. Body size appears to be an underlying determinant of the foraging parameters leading to diet selection. Species that possess digestive capacity and feeding time constraints which approach each other in magnitude have the most generalized diets. The degree that the linear programming models change their diet predictions with a given percent change in parameter values (sensitivity) may reflect the observed ability of the species to vary their diets. In particular, the species which show the most diet variability are those whose diets tend to be balanced between monocots and dicots. The community-ecological parameters of herbivore body-size ranges and species number can possibly be related to foraging behavior.     

Geographic distribution and community structure of bumblebees in the northern Iberian peninsula

Summary Relationships between species distribution and abundance, the influence of proboscis length on species-packing, and species associations within the local assemblages were studied in local communities of bumblebees in northern Spain along an altitudinal gradient. Local species abundance and altitudinal range occupied accounted for much of the variation in species distribution. Altitudinal range occupied by species was related to species distribution, but the most important variable accounting for species distribution was the local percentage abundance. Despite this, there was no evidence for age abundance. Despite this, there was no evidence for bimodality in the distributions of species incidence. A general trends for mean proboscis length in each locality to be greater in lowland localities exists, but this variable was not related to species distribution or abundance. Proboscis length spacings were studied among species in local assemblages and in most of the cases observed spacing did not differ from random expectations. The same patterns were demonstrated calculating spacings for core species in each local assemblage. Furthermore, species showed little tendency towards associations, so it may be concluded that bumblebee assemblages were irregularly structured and no clear patterns emerged from the present study.     

At-sea distribution and scale-dependent foraging behaviour of petrels and albatrosses: a comparative study

1. In order to study and predict population distribution, it is crucial to identify and understand factors affecting individual movement decisions at different scales. Movements of foraging animals should be adjusted to the hierarchical spatial distribution of resources in the environment and this scale-dependent response to environmental heterogeneity should differ according to the forager's characteristics and exploited habitats. 2. Using First-Passage Time analysis, we studied scales of search effort and habitat used by individuals of seven sympatric Indian Ocean Procellariiform species fitted with satellite transmitters. We characterized their search effort distribution and examined whether species differ in scale-dependent adjustments of their movements according to the marine environment exploited. 3. All species and almost all individuals (91% of 122 individuals) exhibited an Area-Restricted Search (ARS) during foraging. At a regional scale (1000s km), foraging ranges showed a large spatial overlap between species. At a smaller scale (100s km, at which an increase in search effort occurred), a segregation in environmental characteristics of ARS zones (where search effort is high) was found between species. 4. Spatial scales at which individuals increased their search effort differed between species and also between exploited habitats, indicating a similar movement adjustment for predators foraging in the same habitat. ARS zones of the two populations of wandering albatross Diomedea exulans (Crozet and Kerguelen) were similar in their adjustments (i.e. same ARS scale) as well as in their environmental characteristics. These two populations showed a weak spatial overlap in their foraging distribution, with males foraging in more southerly waters than females in both populations. 5. This study demonstrates that predators of several species adjust their foraging behaviour to the heterogeneous environment and these scale-dependent movement adjustments depend on both forager and environment characteristics.     

Linking individual foraging behavior and population spatial distribution in patchy environments: a field example with Mediterranean blue tits

 In spite of recent theoretical interest, few field studies have addressed the links between individual behavioral decisions and population distribution. This work analyzes the foraging behavior of individuals and the spatial distribution of a population of blue tits (Parus caeruleus) just before the main breeding season, when blue tit foraging was not affected by central-place or flocking behaviors. The study was carried out in open holm oak Quercus ilex woodlands (dehesas) that are patchy for canopy-foraging birds because of the scattered arrangement of trees. Residence time on each tree was not correlated either with previous flight time or with prey abundance in trees. Flight distances between trees were larger than average distances estimated in random samples of holm oaks taken close to foraging birds. Trees were not selected by birds on the basis of their expected energy costs and rewards. Bird abundance was not related to food availability in trees or to tree size across dehesas. However, bird abundance was strongly correlated with tree density and with the availability of tree holes for nesting, to the extent that the proportion of tits matched the proportions of both tree abundance and hole abundance across study plots. Overall, neither the behavior of individuals nor the distribution of the population of blue tits corresponded with food resources, which appeared superabundant; instead, tits appeared to behave and be distributed according to the distribution of structural resources such as trees and tree holes for nesting. Received: 18 August 1996 / Accepted: 14 March 1997     

Distribution of cave-dwelling bats and conservation status of underground habitats in the Istanbul area

Populations of cave-dwelling bat species were investigated in the transitory region between the Eastern Thrace and the Western Pontus. Data were collected during 30 surveys in 13 underground sites, 10 of which had not been surveyed previously by bat researchers, between March 1999 and March 2000. Approximately 20 000 bats representing eight species were recorded. Grouping the sites according to their ecological resemblance, by means of cluster and correspondence analyses, yielded different results for the summer and winter data. In summer, there was a partial separation of the sites by their location in biogeographic regions. In winter, no regional grouping was observed. It was concluded that in the transitory region, species distribution does not differ considerably between the Eastern Thracian and Western Pontic ecosystems. In addition, a conservation scoring system is proposed for those sites investigated, their status is evaluated, and the most important local roosts are identified.     

腾格里沙漠东南缘公路对路域植被物种组成的影响

沿腾格里沙漠东南缘省道201线沙坡头-景泰段2侧设置48条垂直于公路的样线,调查距路缘不同距离处植被的物种分布特征,研究干旱荒漠区公路建设和运营对植被物种组成的影响.结果表明:随着距路缘距离的增加,草本植物的种数、盖度、生物量和α多样性均逐渐减小,5 m后与对照差异不显著,高度在0～6 m处较大,密度变化不显著.0～2 m处草本植物的物种周转速率较低,2～5 m处最高,10 m后物种组成与对照相似.路缘处的草本植物群落以禾本科植物占优势,抗干扰能力较强的白草、虎尾草和冰草占草本植物总个体数的68.6%.其中,虎尾草在距路缘1 m后,白草和冰草在距路缘2 m后数量和频度迅速减小,而菊科植物茵陈蒿和冷蒿急剧增加,距路缘2 m后占草本植物总个体数的70%.路缘处灌木植物的盖度和密度显著小于对照,物种组成与对照没有显著差异.     

Geographical distribution of genetic polymorphism of the pathogen Histoplasma capsulatum isolated from infected bats, captured in a central zone of Mexico

Fourteen Histoplasma capsulatum isolates recovered from infected bats captured in Mexican caves and two human H. capsulatum reference strains were analyzed using random amplification of polymorphic DNA PCR-based and partial DNA sequences of four genes. Cluster analysis of random amplification of polymorphic DNA-patterns revealed differences for two H. capsulatum isolates of one migratory bat Tadarida brasiliensis. Three groups were identified by distance and maximum-parsimony analyses of arf, H-anti, ole, and tub1 H. capsulatum genes. Group I included most isolates from infected bats and one clinical strain from central Mexico; group II included the two isolates from T. brasiliensis; the human G-217B reference strain from USA formed an independent group III. Isolates from group II showed diversity in relation to groups I and III, suggesting a different H. capsulatum population.     

Niche differentiation depends on body size in a cichlid fish: a model system of a community structured according to size regularities

1. Communities of different species are often structured according to niche differentiation associated with competitive interactions. We show that similar principles may apply on an ecological time-scale when individuals of a species having a wide size variation compete for resources, using the Lake Tanganyika cichlid Lobochilotes labiatus (5-30 cm). This species has a mouth especially adapted to suck up invertebrates from rock crevices. 2. Individuals defended feeding territories against similar-sized conspecifics, but not against different-sized ones. Thus, territories of similar-sized fish rarely overlapped, but up to a total of seven individuals (of seven size-ranks) had broadly overlapping territories with dissimilar-sized individuals. Comparison with expectation from the null model demonstrated clearly that observed size ratios between adjacent size rank were determined non-randomly regardless of sexual combinations. 3. Larger individuals took larger prey types of larger average size, but more importantly used wider rock crevices from which to suck food than smaller individuals. We calculated pairwise values of Schoener's index of diet overlap C(d) and the values of Levin's index of diet breadth B(d) (prey type and prey size) and the same for the width of the rock crevices used for foraging (C(r) and B(r)). C(d) remained high among all combinations of the seven ranks. In contrast, C(r) declined strongly in combinations of adjacent ranks (to 0.27), and was low or zero among further different size ranks. This shows that fish with overlapping territories divided the food resources largely through foraging site partitioning. Accordingly, B(d) did not depend on the size difference to the nearest two coinhabiting fish, whereas B(r) did. 4. We conclude that this L. labiatus community is structured non-randomly: body size-dependent effects on foraging site usage result in competition with, and territorial exclusion of, similar-sized individuals, but not of dissimilar-sized individuals that were accepted as coinhabitants. Accordingly, mean body size ratios (large/small) between two adjacent ranks were consistently approximately 1.28 [standard deviation (SD) = 0.07, n = 104], while approximately 1.34 from the null model (SD = 0.34, n = 10 400 simulations). We discuss our results as an example of Hutchinson's rule, applied originally to size ratios of different species.     

Plant structure and the foraging success of Aphidius rhopalosiphi (Hymenoptera: Aphidiidae)

Abstract. 1. A study of searching behaviour on wheat and host preference of Aphidius rhopalosiphi (DeStefani-Perez) is described.
2. Parasitoids divided their time equally between the leaves but spent very little time on the ear.
3. After contact with honeydew or an aphid host, parasitoids were arrested in a particular area and increased the time spent searching.
4. Aphids feeding on the ear were parasitized less successfully, since their position between the grains protected them from parasitoid attacks.
5. A.rhopalosiphi exhibited no preference for Metopolophium dirhodum (Walker) or Sitobion avenae (Fabricius), although the handling time for the latter was significantly longer; this resulted in fewer S.avenae being parasitized when it was abundant. Parasitoids did not switch between hosts in these experiments.
6. As a result of its searching behaviour, A.rhopalosiphi will encounter and parasitize M.dirhodum feeding on the leaves more frequently than S.avenae, which feeds on the ear. This will limit the parasitoid's ability to regulate populations of the cereal aphid S. avenae.     

夏季大亚湾鱼类群落结构与多样性

根据2018年8月大亚湾海域底拖网鱼类资源调查数据,分析了大亚湾夏季鱼类群落结构特征。结果表明:2018年大亚湾夏季渔获鱼类56种,隶属9目、34科、47属。其中,鲈形目(Perciformes)最多(39种,69.64%);物种组成以短吻鲾(Leiognathus brevirostris)、黄斑蓝子鱼(Siganus oramin)、拟矛尾鰕虎鱼(Parachaeturichthys polynema)、六指马鲅(Polynemus sextarius)和二长棘犁齿鲷(Evynnis cardinali)等小型低值鱼类为主;鱼类物种多样性存在明显的空间差异,表现为湾口海域最大,沿岸海域次之,湾中部海域最小。鱼类群落结构大体分为咸淡水湾内和海水广布湾口两个鱼类群组;对比1985—2017年夏季调查资料可知,30多年来大亚湾夏季鱼类群落物种多样性减小;优势种组成更替显著,由以大型中上层的经济鱼类为主演变为以小型底层、近底层的低值鱼类为主,其主要原因是人类活动对大亚湾生态系统的干扰,尤其是捕捞致使鱼类群落结构发生改变、趋向简单化。