A comparison of pitfall traps with bait traps for studying leaf litter ant communities.

A comparison of pitfall traps with bait traps for sampling leaf litter ants was studied in oak-dominated mixed forests during 1995-1997. A total of 31,732 ants were collected from pitfall traps and 54,694 ants were collected from bait traps. They belonged to four subfamilies, 17 genera, and 32 species. Bait traps caught 29 species, whereas pitfall traps caught 31 species. Bait traps attracted one species not found in pitfall traps, but missed three of the species collected with pitfall traps. Collections from the two sampling methods showed differences in species richness, relative abundance, diversity, and species accumulation curves. Pitfall traps caught significantly more ant species per plot than did bait traps. The ant species diversity obtained from pitfall traps was higher than that from bait traps. Bait traps took a much longer time to complete an estimate of species richness than did pitfall traps. Little information was added to pitfall trapping results by the bait trapping method. The results suggested that the pitfall trapping method is superior to the bait trapping method for leaf litter ant studies. Species accumulation curves showed that sampling of 2,192+/-532 ants from six plots by pitfall traps provided a good estimation of ant species richness under the conditions of this study.     

陷阱法和Winkler法调查土壤节肢动物多样性比较:以千岛湖岛屿封闭生境研究为例

陷阱法和Winkler法是调查土壤动物的两种常规方法,然而这两种方法的调查效率各有优劣。本研究于2010年秋季,在千岛湖中心湖区选取了15个面积不同的岛屿,同时采用Winkler法和陷阱法采集岛屿上的土壤节肢动物,在岛屿这一封闭生境中比较两种方法收集土壤节肢动物的效率。结果表明,两种方法捕获土壤动物类群丰富度差异不显著,但多样性指数差异极显著。Winkler法对常规土壤节肢动物类群的采集效率优于陷阱法,尤其对运动较缓慢、活动范围较小的土壤节肢动物类群的采集具有优势;陷阱法则更优于采集运动能力较强、活动范围较大的类群。基于样方的稀疏曲线结果说明,Winkler法能用少量样方快速获取研究区域的土壤节肢动物群落基本组成,推荐在面积较小的岛屿上使用;而在面积较大的岛屿上使用陷阱法能够获取更多的类群。ChaoJaccard相似性系数比较则显示两种方法所取的土壤节肢动物相似性在大型岛屿上差异较大,说明大样本数据的采集需要两种方法同时使用能够提高数据的完整性和可靠性。本研究的结果为土壤节肢动物研究的方法选择提供了数据支持,具有一定的实际应用性。     

Optimizing Diversity Assessment Protocols for High Canopy Ants in Tropical Rain Forest

The canopies of tropical rain forests support highly diverse, yet poorly known, animal and plant communities. It is vital that researchers who invest the time needed to gain access to the high canopy are able efficiently to survey the animals and plants that they find there. Here, we develop diversity assessment protocols for one of the most ecologically important canopy animal groups, the ants, in lowland dipterocarp rain forest in Sabah, Malaysia. We design and test a novel trap (the purse‐string trap) that can be remotely collected, thus avoiding disturbance to ants. We compare this modified trap with two other methods for surveying canopy ants: precision insecticide fogging and baited pitfall trapping. In total, we collected 39,351 ants belonging to 173 species in 38 genera. Fogging collected the most individuals and species, followed by purse‐string trapping with baited pitfall trapping catching the fewest. Fogging also resulted in samples with a different species composition to purse‐string trapping and baited pitfall trapping, which were not different from one another. Using a ‘greedy algorithm’, which guides the selection of inventory methods in order to maximize new species discovered per researcher‐hour, we show that projects allocating fewer than 132 researcher‐hours to canopy ant collection and identification should sample exclusively using fogging. Those with more time should use a combination of methods. This prioritization technique could be used to accelerate species discovery in future rapid biodiversity assessments. Abstract in Malay is available in the online version of this article.     

Hand searching versus pitfall trapping: how to assess biodiversity of ground beetles (Coleoptera: Carabidae) in high altitude equatorial Andes?

The use of ground beetles (Coleoptera: Carabidae) as bioindicators of environmental change depends on the reliability and the effectiveness of the sampling methods. Those that have been tested in the temperate zone and in tropical forests still await experimentation in tropical high-altitude environments. For the first time, pitfall trapping and hand searching have been compared in Ecuadorian páramo above 4000 m a.s.l., in terms of practical effectiveness. The study was performed on six volcanoes and was based on the comparison of 28 sampling sessions (pitfall trapping and hand searching) performed along two different elevational belts [lower superpáramo (LSP) and upper superpáramo (USP)]. Analyses of sampling sessions showed that detected species richness is slightly higher with hand searching than with pitfall trapping, regardless of the elevation. Additionally, hand searching is more time-effective than pitfall trapping. The performance of the sampling method slightly varies when species assemblage composition is analysed in relation to elevational belts. In the LSP, hand searching and pitfall trapping should be simultaneously used to obtain exhaustive inventories of carabid biodiversity, since different species are likely to be collected by each method. In the USP, hand searching and pitfall trapping efficiency is very similar, but hand searching allows to collect a slightly larger number of species. Lastly, the sample-based rarefaction curves showed that four temporal replicates are mandatory to obtain a robust dataset and an exhaustive inventory of the true species richness and species assemblages composition. Our findings suggest a combined use of hand searching and pitfall trapping in the LSP, while both methods can be used alone for surveying carabids in the USP. Furthermore, hand searching is recommended if the aim is to obtain an inventory of species diversity, whereas pitfall trapping seems more convenient for fine grain ecological and comparative studies.     

Pitfall trapping of scarce Orthoptera at a coastal nature reserve in Essex, UK

The value of pitfall trapping was questioned in a recent review of methods for sampling Orthoptera in grassland ecosystems. However, subsequent to the publication of this review, interesting data has become available from pitfall trapping at Colne Point, an important coastal nature reserve in Essex, UK. As a result of this trapping, the nationally scarce and Essex Red Data List species, Platycleis albopunctata, was rediscovered in the county. This tettigoniid was believed to be extinct in Essex as previous visual searches for the insect at Colne Point had failed to locate it. Large numbers of the Essex Red Data List species, Myrmeleotettix maculatus, were also captured, as were specimens of the nationally scarce cockroach, Ectobius panzeri (Dictyoptera). Systematic pitfall trapping at Colne Point was therefore pivotal in recording scarce species such as P. albopunctata which had proved difficult to locate by visual searching methods.     

笼捕法和陷阱法对森林小型兽类多样性监测效率比较

<正>小型兽类包括食虫目(Insectivora)、啮齿目(Rodentia)、翼手目(Chiroptera)、兔形目(Lagomorpha)等,物种数量多,分布广,适应能力强,对环境变化敏感,因此其群落组成和种群数量变化可较好地反映生境变化的质量和人类活动的干扰程度(肖治术等,2002;李俊生等,2003;仝磊和路纪琪,2010)。小型兽类多样性一直是生物多样性和生态环境监测与评价的重要指示类群之一(周立志和马勇,2002)。统计动物毛发、粪便、巢穴、叫声、足迹等动物痕迹以及直接观察等方法已被广泛用于兽类物种监测和种群密度估计(Eberhardt and Van Etten,1956;Bider,1968;Gannon     

Diversity and composition of epigeal arthropods using pitfall trapping method in different habitat types of Abu Dhabi Emirate,UAE

Pitfall trapping is an efficient self-sampling method for capturing epigeal arthropods for ecological and faunistic studies. During the present study, conducted between March 2009 and March 2015, pitfall trapping was undertaken in five study sites of different habitats in Abu Dhabi Emirate. During the study period a total of 94 monitoring visits were made to collect data from the pitfall traps at five sites in Abu Dhabi. A total of 36,238 individuals of ground-dwelling arthropods of 121 different species belonging to 14 orders and 46 families were recorded from all the study sites using pitfall traps. The order Coleoptera (beetles) was recorded to be the most dominant order with 46 species followed by Hymenoptera (ants, bees & wasps) with 24 species. On average 37.5 ± 3 (mean ± SE) species were recorded every month from all the study sites and number of species did not vary significantly across the months (df = 11, F = 0.48, p = 0.91 one-way – ANOVA). The arthropod fauna was recorded to be highly diversified in different habitat types, but the number of individuals were not evenly distributed across the study sites (H) 1.10, (E) 0.53, Shannon Diversity Index). The highest diversity of arthropods was recorded from a site Wadi Tarabat, followed by Al Wathba Wetland Reserve (AWWR) and Abu Al Abyed. Our findings indicate that to study ground dwelling invertebrate species, pitfall trapping is an efficient method. Moreover, capture efficiency of pitfall traps can be affected by climatic factors and habitat types of Abu Dhabi Emirate. The ideal period to encounter the highest number of species is between March to April and September to November across all the habitat types.     

Using demographic data to better interpret pitfall trap catches

The results of pitfall trapping are often interpreted as abundance in a particular habitat. At the same time, there are numerous cases of almost unrealistically high catches of ground beetles in seemingly unsuitable sites. The correlation of catches by pitfall trapping with the true distribution and abundance of Carabidae needs corroboration. During a full year survey in 2006/07 in the Lake Elton region (Volgograd Area, Russia), 175 species of ground beetles were trapped. Considering the differences in demographic structure of the local populations, and not their abundances, three groups of species were recognized: residents, migrants and sporadic. In residents, the demographic structure of local populations is complete, and their habitats can be considered "residential". In migrants and sporadic species, the demographic structure of the local populations is incomplete, and their habitats can be considered "transit". Residents interact both with their prey and with each other in a particular habitat. Sporadic species are hardly important to a carabid community because of their low abundances. The contribution of migrants to the structure of carabid communities is not apparent and requires additional research. Migrants and sporadic species represent a "labile" component in ground beetles communities, as opposed to a "stable" component, represented by residents. The variability of the labile component substantially limits our interpretation of species diversity in carabid communities. Thus, the criteria for determining the most abundant, or dominant species inevitably vary because the abundance of migrants in some cases can be one order of magnitude higher than that of residents. The results of pitfall trapping adequately reflect the state of carabid communities only in zonal habitats, while azonal and disturbed habitats are merely transit ones for many species of ground beetles. A study of the demographic structure of local populations and assessment of the migratory/residential status of particular carabid species are potential ways of increasing the reliability of pitfall trap information.     

Ground beetle (Coleoptera: Carabidae) inventories: a comparison of light and pitfall trapping

Carabid inventories gained via pitfall trapping were compared to manual samples from light towers. A comparison of the two methods indicated that pitfall traps recorded a significantly higher diversity of carabids and were efficient in indicating changes of habitat conditions. Nevertheless, this method failed to give near-complete inventories of all carabid species present. Manual sampling at light towers resulted in far greater sample sizes, and this method was particularly efficient in monitoring potential pest species, but again failed to record all species present. Both methods hence showed different strengths, and only a combination, potentially also including further sampling techniques, will enable the generation of complete species inventories.     

Is pitfall trapping a valuable sampling method for grassland Orthoptera?

Common methods to assess diversity and abundance of Orthoptera are sweep netting, transect counts and box-quadrat sampling. Pitfall trapping, by contrast, is rarely used, and the value of this method is still being questioned. In 2008, we studied Orthoptera species richness and abundance in five vegetation types along a gradient of dune succession on the Baltic Sea island of Hiddensee (NE Germany) by comparing transect-count and pitfall-trapping data. Using transect counts, 12 species were detected in the study area. With pitfall traps, three chorto- and thamnobiont Ensifera species (C. dorsalis, M. roeselii and T. viridissima) were not caught at all, and it was only in low-growing and sparsely-vegetated grey dunes that all present species were detected. With pitfall traps, the proportion of present species recorded strongly declined with increasing height and density of the vegetation type. Assuming that transect counts are a good proxy for relative Orthoptera densities, densities ascertained by pitfall traps are strongly biased by vegetation structure and locomotive behaviour of the species. More than 80% of all individuals were caught in sparsely-vegetated grey dunes. Frequency patterns of the species also differed. Using pitfall traps, especially chortobiont species were significantly underrepresented. Qualitative and quantitative sampling of Orthoptera using pitfall traps seems only reasonable in habitats with low and sparse vegetation and a high proportion of geobiont species.     

A census of a community of small terrestrial vertebrates

A small vertebrate community of eighteen terrestrial species was revealed by removal trapping in 1 ha of Western Australian Banksia woodland in autumn. Nine of these species were lizards, three were mammals, three were snakes and three were frogs. The use of pitfall and mammal traps on an 8 × 8 m grid was shown to be sufficient to census the majority of terrestrial species in the study site. A biomass of 2063 g/ha of terrestrial species was estimated from trapping records. Frogs (three species) had the greatest biomass (41% of total), but the introduced mouse Musmusculus contributed the greatest biomass (36%) of any single specie.     

The energetic equivalence rule rejected because of a potentially common sampling error: evidence from carabid beetles

Abundance data from pitfall traps are widely used to estimate the relationship between beetle body size and abundance. Such data probably overestimate densities of large bodied species and may overestimate slopes of size‐abundance relationships. Here, we test this idea by comparing size‐abundance patterns found using data from pitfall trapping with those found with data from a quantitative method of estimating abundance, quadrat sampling. We use data from a total of 47 communities. As expected, slopes of size‐abundance relationships are significantly more positive when estimated using data from pitfall traps compared to when using quadrat sampling data. This was seen when looking across different communities, within communities sampled by both methods and when focusing on the set of species found by both methods within a community. These results were also generally found regardless of method of analysis, which were done using regression with species values as independent data points and using the independent contrast method, and with slopes estimated using ordinary least square regression or the structural relation. Most important, slopes of size‐abundance relationships based on data from pitfall traps were on average significantly more positive than ?0.75 on log–log scales, and thus inconsistent with the energetic equivalence rule. Slopes based on quadrat sampling, on the other hand, were on average not significantly different from ?0.75. The rejection of the energetic equivalence rule based on data from pitfall traps here is therefore a sampling artefact. Similar problems may apply to abundance data from virtually all insect trapping methods, and should make us consider re‐examining many of the size‐abundance patterns documented so far. As a large proportion of all animal species are insects, and traps are widely used to estimate abundance, this is a potentially important problem for our general understanding of the relationship between species body size and abundance.     

Too hot to handle? Balancing increased trapability with capture mortality in hot weather pitfall trapping

Trapping at air temperatures close to, or exceeding, critical thermal maxima is important for comprehensive sampling of vertebrate assemblages and collection of sufficient data for impact assessment. However, pitfall trapping on hot days also potentially exposes trapped animals to stress or death through overheating or desiccation. We investigate causes of mortality from 14 305 captures over a 22‐year pitfall trap study in arid South Australia and compared mortality rates with maximum temperatures, solar radiation and rainfall. Overall mortality rate was 3.2% with chewing by rodents and handling accidents the most influential cause of death recorded. The highest mortality rates were experienced by the tiny skink, Lerista labialis, which was difficult to detect in traps each day and hence problematic to assess the effect of weather variables on capture mortality. For all other abundant species, high maximum temperature was only a significant explanatory variable for increased death rates of the house mouse Mus domesticus, and increased solar radiation was positively related to capture mortality for the house mouse, the frog Neobatrachus sudelli and the small skink Ctenotus schomburgkii. However, capture rates for these taxa and eight other common species would have been significantly lower if trapping did not occur on days of 40 °C or more. We conclude that trapping in hot weather is both desirable and justifiable and suggest techniques for further reducing mortality rates in pitfall studies.     

A comparison of three methods to survey saproxylic beetles in hollow oaks

One of the most endangered assemblages of species in Europe is insectsassociated with old trees. For that reason there is a need of developing methodsto survey this fauna. This study aims at comparing three methods – windowtrapping, pitfall trapping and wood mould sampling – to assess speciesrichness and composition of the saproxylic beetle fauna in living, hollow oaks.We have used these methods at the same site, and to a large extent in the sametrees. Useful information was obtained from all methods, but they partiallytarget different assemblages of species. Window trapping collected the highestnumber of species. Pitfall trapping collected beetles associated with treehollows which rarely are collected by window traps and therefore it isprofitable to combine these two methods. As wood mould sampling is the cheapestmethod to use, indicator species should preferably be chosen among specieswhich are efficiently collected with this method.     

The use of barrier-connected pitfall trapping for sampling predatory beetles and spiders

The efficiency of barrier-connected pitfall trapping was compared to conventional single traps or arrays. For ground-active beetles, the use of a pitfall system incorporating a wetting agent with five traps arranged in a cross formation connected by plastic barriers was more efficient than a single dry trap by at least an order of magnitude and at least twice as efficient as five traps without connecting barriers. It is argued that the efficiency of pitfall trapping may be improved markedly by using barrier-connected traps, particularly for some carabid and staphylinid beetles and lycosid spiders. Capture of linyphiids was not improved by the use of barriers and was dependent only on the use of wetting agent and number of traps used.     

地面节肢动物营养类群对土地覆被变化和管理扰动的响应

近几十年来,黑河中游荒漠绿洲过渡带大面积天然沙质草地被转变为农田和防风固沙人工林,然而目前尚缺乏土地利用/覆被变化和管理措施对地面节肢动物多样性形成和维持影响的系统研究。以天然沙质草地转变为的人工梭梭灌木林、人工杨树林、人工樟子松林和农田为研究对象,以天然草地为对照,通过对5种样地地面节肢动物群落的调查及非生物环境因子的测定,采用典范对应分析(CCA)等方法,系统探讨了土地覆被和管理强度(天然草地和人工梭梭林实施零管理、杨树和樟子松人工林实施灌溉管理、农田实施灌溉和施肥管理)变化对地面节肢动物营养类群组成、数量和物种丰富度的影响。主要结果是:(1) 在干旱环境下,单纯改变土地覆被并不会导致土壤环境的显著变化,而高强度的管理扰动加速了土壤环境的演变过程。(2)不同土地覆被和管理措施对营养类群组成及其数量和丰富度的调控作用不同,将天然草地转变为杨树和樟子松人工林和农田后,显著提高了捕食性和植食性类群的比例,降低了'腐食性+杂食性’类群的比例;转变为人工梭梭林后显著降低了3种营养类群的数量;转变为人工杨树林后显著降低了'腐食性+杂食性’类群数量;转变为人工樟子松林后显著增加了植食性类群数量而降低了其它类群的数量;转变为农田后显著增加了植食性类群数量而降低了'腐食性+杂食性’类群数量。(3)影响捕食性动物分布的关键环境因子是地面温度、土壤硝态氮和田间持水量,影响植食性动物分布的关键因子是土壤粘粉粒、土壤硝态氮、土壤容重和pH值,影响'腐食性+杂食性’动物分布的关键因子是地面温度和田间持水量。主要结论是:土地覆被变化与管理措施相互作用对地面节肢动物群落组装过程及其多样性形成具有重要调控作用,尽管其相对重要性不同。     

Seasonal distribution and prevalence of dung beetles (Coleoptera: Scarabaeidae) in Kurukshetra,Northern India

A total of 8306 individuals as 29 species from 3 subfamilies (Hybosorinae, Aphodiinae, Scarabaeinae) were trapped by pitfall bait trapping. The maximum number of species of Scarabaeinae (68.97%) and number of individuals of Aphodiinae (56.84%) take part in the formation of a community. The number of species, number of individuals, diversity and dominance changes throughout the season. Seasonal prevalence of 82.76% of species and 50.81% of individuals was found in June. Aphodius campestris was found to be more attracted to the pitfall bait traps. The beetle community found in May shows the maximum Shannon's Diversity Index (2.46) but Margalef's Diversity Index was highest in August (3.06). Environmental factors play an important role in the occurrence and abundance of dung beetles. In the present study non-significant but positive correlations between temperature and species richness, abundance and diversity were found. Percent relative humidity showed a positive correlation with abundance only, and negative correlations with species richness and diversity.     

Influence of abiotic factors on spider and ground beetle communities in different salt-marsh systems

Salt marshes are interesting and endangered ecosystems in West-Europe. Nevertheless, their arthropod fauna remains largely unknown and the factors determining assemblages at micro-habitat scale are poorly understood. Few data are also available about the effects of management measures in salt marshes and how to monitor them. The aim of the present study is to determine the major factors structuring two dominant communities of arthropods, spider and ground beetles, in natural, managed (cutting and sheep grazing) and invaded (by the grass Elymus athericus) salt marshes. The two taxa were studied during 2002 and 2003 in different salt marshes of the Mont Saint-Michel Bay (NW France) by pitfall traps and hand-collecting. A total of 12 350 spiders (57 species) and 16 355 ground beetles (34 species) were caught during the study and analysed with respect to effects of the salinity gradient and of habitat structure characteristics. Spiders and ground beetles reacted differently to environmental factors in salt marshes. Spiders could more easily cope with salinity and their presence/absence was less related to the salinity than that of ground beetles. For ground beetles, there were few other community-structuring environmental factors and these were only related to the edaphic environment: species restricted to open habitats, significant effects of moisture content and salinity revealed by CCA. Because they are likely to bring complementary information on abiotic factors, we finally suggest using both spiders and ground beetles for monitoring the effects of management practices in salt marshes.     

Slippery or sticky? Functional diversity in the trapping strategy of Nepenthes carnivorous plants

The pitcher-shaped leaves of Nepenthes carnivorous plants have been considered as pitfall traps that essentially rely on slippery surfaces to capture insects. But a recent study of Nepenthes rafflesiana has shown that the viscoelasticity of the digestive fluid inside the pitchers plays a key role. Here, we investigated whether Nepenthes species exhibit diverse trapping strategies. We measured the amount of slippery wax on the pitcher walls of 23 taxa and the viscoelasticity of their digestive liquid and compared their retention efficiency on ants and flies. The amount of wax was shown to vary greatly between species. Most mountain species exhibited viscoelastic digestive fluids while water-like fluids were predominant in lowland species. Both characteristics contributed to insect trapping but wax was more efficient at trapping ants while viscoelasticity was key in trapping insects and was even more efficient than wax on flies. Trap waxiness and fluid viscoelasticity were inversely related, suggesting the possibility of an investment trade-off for the plants. Therefore Nepenthes pitcher plants do not solely employ slippery devices to trap insects but often employ a viscoelastic strategy. The entomofauna specific to the plant's habitat may exert selective pressures, favouring one trapping strategy at the expense of the other.     

Inventory and Bioindicator Sampling: Testing Pitfall and Winkler Methods with Ants in a South African Savanna

The sampling efficiency and consistency of pitfall traps and Winkler samples for inventory, bioindicator and ecological studies in savanna habitats was compared using ants. Pitfall traps are often used for ant collecting while Winkler litter sampling has until now had rather limited use. We test Winkler sampling for the first time in a South African savanna. Pitfall traps were more efficient and productive than Winkler sampling for epigaeic ants, with a greater total species richness and higher abundance of ants recorded. Winkler samples contributed few additional species. The relative abundance of different sized ants was different with the two collection methods. Winkler sampling was found to catch greater numbers of smaller ants than pitfall trapping, whereas pitfall trapping caught more larger ants. The standard collecting Winkler quadrat size of 1m² did not perform as well as 2× m² quadrats combined for one sample.