Acoustic mirror effect increases prey detection distance in trawling bats

Many different and phylogenetically distant species of bats forage for insects above water bodies and take insects from and close to the surface; the so-called trawling behaviour. Detection of surface-based prey by echolocation is facilitated by acoustically smooth backgrounds such as water surfaces that reflect sound impinging at an acute angle away from the bat and thereby render a prey object acoustically conspicuous. Previous measurements had shown that the echo amplitude of a target on a smooth surface is higher than that of the same target in mid-air, due to an acoustic mirror effect. In behavioural experiments with three pond bats (Myotis dasycneme), we tested the hypothesis that the maximum distances at which bats can detect prey are larger for prey on smooth surfaces than for the same prey in an airborne situation. We determined the moment of prey detection from a change in echolocation behaviour and measured the detection distance in 3D space from IR-video recordings using stereo-photogrammetry. The bats showed the predicted increase in detection distance for prey on smooth surfaces. The acoustic mirror effect therefore increases search efficiency and contributes to the acoustic advantages encountered by echolocating bats when foraging at low heights above smooth water surfaces. These acoustic advantages may have favoured the repeated evolution of trawling behaviour.     

Leptospirosis risk increases with changes in species composition of rat populations

Rats are major reservoirs of leptospirosis and considered as a main threat to biodiversity. A recent introduction of Rattus rattus to the island of Futuna (Western Polynesia) provided the opportunity to test if a possible change in species composition of rat populations would increase the risk of leptospirosis to humans. We trapped rodents on Wallis and Futuna and assessed Leptospira carriage in 357 rodents (Rattus norvegicus, R. rattus, Rattus exulans, and Mus domesticus) from 2008 to 2012. While Leptospira prevalence in rodents and the composition of rat populations on Futuna fluctuated with rainfall, the biomass of Leptospira-carrying rodents has been continuously rising from 2008 to 2012. Our results suggest that the introduction of R. rattus increases the risk to humans being infected with leptospirosis by rats.     

Predation by soil inhabiting arthropods in intercropped and monoculture agroecosystems

Experiments were carried out to determine effects of intercropping on macroarthropod predator activity, both diurnal and seasonal, and on relative consumption of lepidopteran pest larvae during a two-year study. Maize (corn, Zea mays) was intercropped into a grass-legume mixture and compared to monoculture maize. There was significantly more predator activity (number of attacks by predators on pest larvae) and predation (number of larvae consumed) in the intercropped system compared with the monocultured treatment during both years of the study. Predator activity and consumption of larvae were greatest at night in both systems and least during the day. However, the intercropped system had significantly more predator activity during each observation over a 24-h period than did the monocultured system. Predator activity and predation did not fluctuate appreciably over the early part of the growing season until August when there was a significant increase in both parameters. Carabid beetle larvae and spiders were the major predators in June, however, in July and August large carabid adults (> 15 mm) became the dominant predators. Significant correlations were found among carabid beetle activity, density estimates of macroarthropods and the number of lepidopteran larvae consumed in these corn agroecosystems. These correlations between techniques and endemic predatory arthropods indicate that predation is a significant factor in reducing pest populations in intercropped agroecosystems.     

Visual prey detection by near-infrared cues in a fish

Many animal species are able to perceive light wavelengths beyond those visible to humans. While numerous species are additionally sensitive to short wavelengths (UV), long wavelengths such as the near-infrared spectrum (NIR) are supposed to be unsuitable for visual perception. Here, we experimentally show that under exclusive NIR illumination, the cichlid fish Pelvicachromis taeniatus displays a clear foraging response towards NIR reflecting prey. Additional control experiments without prey indicate that the observed behavior is not a mere response to the NIR environment. These results give first evidence for NIR visual sensitivity in a functional context and thus challenge the current view about NIR perception.     

蠕虫污泥减量效果及其影响因素分析

研究了蠕虫生长在活性污泥法中试系统的污泥减量效果及其对出水水质的影响 ,同时对蠕虫生长的影响因素进行了初步分析 .结果表明 ,除了初始的20d之外 ,整个试验过程中均有蠕虫出现 ,其中红斑瓢体虫(Aeolosomahemprichicii)和仙女虫(Naiselinguis)交替占据优势地位 ,但红斑瓢体虫占据主导地位的时间长于仙女虫 ,而吻盲虫 (Pristinaaequiseta)只是偶尔存在 .蠕虫连续保持高密度生长 (曝气池中蠕虫总密度大于 30条 /mg)长达 172d .高密度下的蠕虫生长不仅能显著降低污泥产率 ,而且能明显提高污泥的沉降性能 .蠕虫密度越高 ,出水水质越差 .仙女虫比红斑瓢体虫具有更大的污泥减量能力 ,并且前者对出水水质的影响也大于后者 .蠕虫生长不影响硝化过程 ,但当仙女虫占优势时 ,蠕虫生长会导致出水PO3₄^3--P浓度的升高 .蠕虫生长影响因素的分析表明 ,只有污泥龄对 2种蠕虫的生长没有影响 ,但温度和水力停留时间均能显著影响它们的生长 .     

Predation and aggressiveness in host plant protection: a generalization using ants from the genus Azteca

In studying the ant genus Azteca, a Neotropical group of arboreal species, we aimed to determine the extent to which the ants use predation and/or aggressiveness to protect their host plants from defoliating insects. We compared a territorially dominant, carton-nester, Azteca chartifex, and three plant-ant species. Azteca alfari and Azteca ovaticeps are associated with the myrmecophyte Cecropia (Cecropiaceae) and their colonies shelter in its hollow branches; whereas Azteca bequaerti is associated with Tococa guianensis (Melastomataceae) and its colonies shelter in leaf pouches situated at the base of the laminas. Whereas A. bequaerti workers react to the vibrations transmitted by the lamina when an alien insect lands on a leaf making it unnecessary for them to patrol their plant, the workers of the three other species rather discover prey by contact. The workers of all four species use a predatory behaviour involving spread-eagling alien insects after recruiting nestmates at short range, and, in some cases, at long range. Because A. alfari and A. ovaticeps discard part of the insects they kill, we deduced that the workers' predatory behaviour and territorial aggressiveness combine in the biotic defence of their host tree.     

A review of postfeeding larval dispersal in blowflies: implications for forensic entomology

Immature and adult stages of blowflies are one of the primary invertebrate consumers of decomposing animal organic matter. When the food supply is consumed or when the larvae complete their development and migrate prior to the total removal of the larval substrate, they disperse to find adequate places for pupation, a process known as postfeeding larval dispersal. Several important ecological and physiological aspects of this process were studied since the work by Green (Ann Appl Biol 38:475, 1951) 50 years ago. An understanding of postfeeding larval dispersal can be useful for determining the postmortem interval (PMI) of human cadavers in legal medicine, particularly because this interval may be underestimated if older dispersing larvae or those that disperse longer, faster, and deeper are not taken into account. In this article, we review the process of postfeeding larval dispersal and its implications for legal medicine, in particular showing that aspects such as burial behavior and competition among species of blowflies can influence this process and consequently, the estimation of PMI.     

风险沟通在港口环境风险管理中的应用

风险沟通是风险管理中新兴起的领域,很快发展为风险管理中非常重要的内容。其对于促进事件处理、告知公众真相、增强政府威信、疏导公众情绪、维护社会稳定等都起到很大的作用。通过风险沟通内涵的探讨,建立了风险沟通模型,在分析美国、意大利等先进国家风险沟通经验以及研究进展分析的基础上,将风险沟通理论引入到我国港口环境风险管理中,从预防性沟通、应急性沟通和善后处理三方面讨论了我国港口发展过程中的风险沟通思路。     

Supercooling ability in the house spider, Achaearanea tepidariorum: effect of field-collected and laboratory-reared prey

The influence of prey animals on the supercooling ability of the house spider, Achaearanea tepidariorum, was studied by feeding spiders with field-collected and laboratory-cultured prey animals. Irrespective of the prey species supplied, spiders given field-collected prey had a higher supercooling point than those given laboratory-cultured counterparts. This means that (1) the field prey animals contained some efficient ice nucleators, whereas the laboratory animals were free from such substances and (2) the ice nucleators must be of external origin. Several lines of evidence also suggest that, under natural conditions, potential prey animals for the house spider are highly contaminated with ice nucleators.     

扎龙湿地丹顶鹤繁殖栖息地的选择及扩散

景观演变对野生动物栖息地质量和连接度造成的影响,一直是威胁全球生物多样性保护的关键问题,开展扎龙湿地丹顶鹤（Grus japonensis）繁殖栖息地选择及繁殖期生境间的扩散研究,对野生丹顶鹤的保护具有重要的意义。首先利用需要“出现点”的生态位MAXENT模型,进行适宜栖息地选择研究。从水源、食物、干扰、隐蔽物四个方面选择明水面距离、土壤湿度、NDVI、道路距离和居民地距离五个环境变量作为丹顶鹤繁殖栖息地选择的影响因子,预测扎龙保护区可供丹顶鹤进行营巢繁殖的栖息地分布,并分析各影响因子的反应曲线。结果显示：丹顶鹤易于选择远离道路和居民地干扰且靠近明水面的区域作为营巢栖息地,栖息地土壤湿度较高并且植被覆盖较多。从MAXENT模型中提取了38个适宜栖息地斑块,基于电路理论模拟丹顶鹤繁殖期失去飞行能力时的多路径扩散,最大电流密度图突出了可能的“夹点”,模拟出具有一定宽度范围的连接区域,可供丹顶鹤在繁殖期间进行扩散。累积电流密度图突出了在维持网络连通性方面起到积极作用的斑块,并进行面积加权来评估适宜栖息地斑块的综合重要性。结果表明,在MAXENT模型预测出的适宜栖息地斑块基础上,考虑丹顶鹤繁殖期的迁移扩散行为,利用累积电流密度面积加权来评估适宜栖息地斑块的综合重要性,得到的适宜性等级更符合丹顶鹤真实巢址的分布。研究成果可为保护区丹顶鹤栖息繁殖生境的恢复和保护提供科学依据。     

The population ecology of Datura ferox in soybean crops. A simulation approach incorporating seed dispersal

A numerical model for simulating the population dynamics of Datura ferox L. (chamico, chinese thronapple) has been built based on previously reported data. In the model, a soybean field is divided into 0.7×0.7-m conceptual modules. A seed production sub-model simulates the annual seed output of each module, and a seed dispersal sub-model simulates the distribution of these propagules within the field in accordance to a specified dispersal pattern. Different model scenarios were generated by varying the proportion of seeds lost from the soil bank, the annual recruitment, the seedling mortality and the proportion of seeds exported from the field during crop harvest. The results obtained by simulation suggest that (1) seed dispersal due to crop harvesting tends to produce an exponential growth of weed seed production, (2) limited or no success could be attained in the control of D. ferox using procedures that kill the seedlings efficiently if combine harvesters are not adjusted so as to maximize the proportion of weed seeds that are exported from the field and (3) if cleaning debris continues to be returned to the ground during crop harvesting, the improvement in the efficiency of the grain/weed separating mechanisms does not provide an effective long-term strategy to avoid grain contamination problems.     

From Specialization in Spider Egg Predation to an Original Nesting Mode in a "Primitive" Ant: A New Kind of Lestobiosis

 Mature colonies of Discothyrea oculata were observed nesting in cribellatid spider oothecas where they found both shelter and food although these oothecas, installed in preexisting cavities, were protected with crimped silk. Workers of colonies bred in test tubes during laboratory experiments recuperated the silk from spider oothecas introduced into their foraging area, using their mandibles and forelegs, to operculate and line the test tubes. Also, colonies left the test tubes to shelter in the cribellatid spider oothecas. The term "arachnolesty" is proposed for this new kind of lestobiosis. Received: 20 April 1998 / Accepted in revised form: 16 October 1998