洗胃法在鳄蜥食性研究中的应用

为了研究洗胃法是否适用于鳄蜥（Shinisaurus crocodilurus）的食性研究,2006年8～9月我们在广东罗坑省级自然保护区,通过投喂食物,然后再冲洗的方法来检验洗胃法的冲洗效果。结果显示洗胃法对成体和亚成体鳄蜥的总洗出率均高于99．30％,食物个体数的洗出率均高于90．83％,投喂的12种食物都能被洗出。观察发现洗胃之后,对鳄蜥的正常生活没有影响。鳄蜥吃进的实验食物中,未洗出的食物大小与鳄蜥的体长、头宽、体重不相关;食物的洗出效率与鳄蜥的体长、头宽、体重不相关。成体、亚成体洗出和未洗出的食物大小均存在显著差异。未被洗出的食物个体在12种食物中不是随机分布的,体积大的食物比体积小的食物容易被洗出。研究表明,洗胃法适用于鳄蜥的食性研究,并且效果较好。     

鲁西南平原黑斑蛙食性分析

黑斑蛙(Rana nigromaculata)属两栖纲蛙科动物,是鲁西南平原的优势种,1989年6—8月间在以菏泽地区为中心的鲁西南平原进行了黑斑蛙野外捕食观察和食物分析,捕蛙时间一律在频繁捕食活动期刚过的20—21时,在田间、地头水沟旁捕蛙后立即称重、分类、断头、取胃,用甲醛固定。共剖析239只,雌102只,雄137只,胃内动物以有头为标准进行统计,结果如下。1食性与食量分析剖检胃内容物中动物性食物占食物总量的92.7%,其中有头动物482头,分属4门、7纲、18目、49科,以节肢动物昆虫纲最多,占个体总数的76.35%,蛛形纲占14.73%,脊椎动物占2.90%,其它占6.02%…     

无尾两栖类的简易标记法

在动物学、动物生理学和生态学等学科的研究中 ,常常需要对所研究的动物个体进行标记 ,以便于对其个体活动的追踪研究观察。在有关研究工作中 ,目前使用多种标记法 ,如烙印法、同位素示踪法等。在对蛙类的研究实践过程中 ,我们找到了针对蛙类研究的一种简单易行的标记法——划蹼法和切趾 (指 )法。由于蛙类个体小 ,较为脆弱。烙印等方法容易对其造成伤害 ,影响其生存 ,同时也不易进行操作。尤其是在蝌蚪变态期不易进行有效的标记 ,给追踪观察造成极大的困难。我们经过对中国林蛙的标记试验探索 ,找到了一种简单易行的标记方法。即采用划去蛙…     

舟山群岛变态后牛蛙的食性研究

牛蛙(Ranacatesbeiana)是极其危险的外来入侵种,对当地生物类群的捕食是其主要的危害机制,但目前有关其食性的研究均只局限于一个研究地点。为了全面评估牛蛙对当地生物类群的捕食影响,2005年6月30日至8月11日期间,作者采用洗胃法对舟山群岛8个岛屿(岱山、六横、秀山、佛渡、桃花、虾峙、册子和普陀山)变态后牛蛙的食性进行了研究。共采集到变态后的牛蛙391只,包括牛蛙成体113只和亚成体278只。食性分析结果表明:(1)按食物体积计算,成年牛蛙以十足目、鞘翅目、蜻蜓目、中腹足目、蛙形目和鲤形目为主要食物,亚成体牛蛙以十足目、鞘翅目、鲤形目、蜻蜓目、直翅目、膜翅目、鳞翅目幼虫、中腹足目和蛙形目为主要食物;成体和亚成体牛蛙胃中食物的平均大小均随其体长增加而增大;(2)不同岛屿上的牛蛙在主要食物类型构成上存在差异。这表明牛蛙在不同地方对不同生物类群造成的捕食危害是不一样的,充分反映了其生态危害的广泛性。     

DNA宏条形码技术在鸟类食性分析中的运用

鸟类在全球广泛分布,不同鸟类物种利用的食物类群存在很大差异,而食性研究是动物营养学和生态学领域的重要研究内容。本文对一些传统鸟类食性鉴别方式及其不足进行回顾,传统鸟类食性鉴别方式包含扎颈法、剖胃法、粪便收集法、相机记录法等。随着测序技术的高速发展,DNA宏条形码技术出现,并广泛应用于动物食性研究。近些年来,该技术也被应用于鸟类食性研究中。本文综述了DNA条形码和DNA宏条形码的操作原理和条件,对鸟类食性研究中的DNA条形码与引物的选择做了详细介绍。对比传统鉴别方法,DNA宏条形码技术降低了物种鉴定难度,减少了人为影响因素,提高了目标样本中物种的鉴定效率,能对粪便、胃容物等混合或不成型样本进行分析。另一方面,在扩增多物种混合的DNA样品中的目标片段时,可能出现偏离,造成结果的不确定性,并且难以根据结果得出较准确各食物组分的比例。未来在使用宏条形码技术对鸟类食性的分析中,可结合其他方法改善对食物的量化以及食物属性的判断。     

九华山习见蛙类的若干生态资料

一、食性分析对九华山区采得的青蛙(Rana nigromaculata)、泽蛙(R.limnocharis)、棘胸蛙(R.spinosa)、阔褶蛙(R.latouchii)和日本林蛙(R.japonica japonica)等5种习见蛙类共253个胃做了食性分析。除在野外直接观察记录外,主要是根据解剖胃部内容物,按其捕食的种类和数量逐项分析统计。对食物个数的确定,是根据被吞食动物的某些器官或结构的套数来计算,少于一套者计为一,多于一套少于二套者计为二,以此类推;有头者以头的数目汇计。根据解剖结果,以确定其对农林的益害关系。结果在253号标本中,有236号标本胃内有食物,包括环节动物、节肢动物…     

昆明滇蛙和昭觉林蛙食物比较及益害评价

:对1998年5月—2003年11月采自昆明白龙寺、花红洞及西街口的1105只滇蛙(Rana pleuraden)及428只昭觉林蛙(Rana chaochiaoensis),采用剖胃法作食性分析,分别计算它们的食物数量和频次百分比、α多样性指数、百分率相似性指数、营养生态位宽度、营养生态位重叠值和有益系数等。分析和计算结果显示,不同采集地的滇蛙以及滇蛙与昭觉林蛙之间的主要食物组成基本相同;但两种蛙之间,甚至同一物种的雌雄之间的食物多样性及营养生态位均存在分化。滇蛙和昭觉林蛙周年的有益系数都为正值,说明它们对人类的益处大于害处,其中又以滇蛙的有益程度较昭觉林蛙的高。研究结果表明,同一物种采自不同地域的种群和(或)同一种群采自不同的季节或年份,其有益系数均具可变性,即有益系数不具可比性。此系数仅表示蛙在一定时期对人类的益害程度。     

千岛湖花臭蛙个体发育过程中的食性变化

个体发育过程中的食性变化普遍存在于无尾目类群中。我们于2012~2013年,对千岛湖地区的花臭蛙(Odorrana schmackeri)进行抓捕采样,测量体长、体重以及头宽等身体指标,同时鉴定胃内食物并加以测量和分析。调查期间,共捕获花臭蛙838只,测量胃内食物2 178个。结果表明,花臭蛙食物种类丰富,食物类群隶属78科,但食谱宽度较窄。随着花臭蛙体长增加,其摄食的食物总体积和单个食物体积显著增加,但摄食食物数量显著减少。同时,不同体长的花臭蛙对不同食物的摄食频率也有不同。半翅目、膜翅目以及等翅目等小型食物的摄食频率随花臭蛙体长的增加而变小,而直翅目以及鳞翅目幼虫等大型食物的摄食频率随花臭蛙体长的增加而变大。综上所述,千岛湖地区花臭蛙在个体发育过程中存在食性变化,因此在以后无尾目类群的食性研究中,应将个体发育的因素考虑在内。     

昆明滇蛙的取食策略

目前国内研究两栖类食性选择或偏好多未考虑蛙胃内不同食物的丰盈程度与栖境不同食物资源是否存在相关性.在分析了采自昆明白龙寺和昆明石林西街口的494只滇蛙(Rana pleuraden)的食性的同时,分析了采自对应栖境中的食物资源组成.结果表明,滇蛙的食物成份与食物资源相具有稳定性,主要类群均为直翅目、同翅目、半翅目、鞘翅目、双翅目、鳞翅目、膜翅目和蛛形纲等8类.但又存在变异性,不同产地、不同年份和不同月份之间的蛙标本胃内的食物成分各类群的比例均不相同.主要食物成份与食物资源相的差异显著性分析、相关性分析和选择性分析等方面的结果均支持或证明:滇蛙对食物具有选择性或取食偏好.栖境的食物资源相与蛙胃内的食物成分不存在相关性(白龙寺:r=0.077,P=0.575;西街口:r=-0.086,P=0.500).直翅目(Ei＜-0.35)和同翅目(Ei＜-0.37)昆虫是滇蛙取食时回避的食物,而对鞘翅目、鳞翅目、膜翅目和蛛形纲等4个类群(Ei＞0.45)具有明显偏好.     

昆明滇蛙和昭觉林蛙食物比较及益害评价

对1998年5月—2003年11月采自昆明白龙寺、花红洞及西街口的1?105只滇蛙(Rana pleuraden)及428只昭觉林蛙(Rana chaochiaoensis)，采用剖胃法作食性分析，分别计算它们的食物数量和频次百分比、α多样性指数、百分率相似性指数、营养生态位宽度、营养生态位重叠值和有益系数等。分析和计算结果显示，不同采集地的滇蛙以及滇蛙与昭觉林蛙之间的主要食物组成基本相同；但两种蛙之间，甚至同一物种的雌雄之间的食物多样性及营养生态位均存在分化。滇蛙和昭觉林蛙周年的有益系数都为正值，说明它们对人类的益处大于害处，其中又以滇蛙的有益程度较昭觉林蛙的高。研究结果表明，同一物种采自不同地域的种群和(或)同一种群采自不同的季节或年份，其有益系数均具可变性，即有益系数不具可比性。此系数仅表示蛙在一定时期对人类的益害程度。     

On the trophic spectrum of Pelophylax ridibundus (Pallas, 1771) (Amphibia: Anura: Ranidae) in western Iran

Using the stomach flushing technique, a total of 188 specimens of the Marsh Frog, Pelophylax ridibundus, were flushed, of which 129 had at least one food item in the stomach. The diet consisted of Annelida, Mollusca, Arthropoda and Chordata with Arthropoda being the most abundant group. Both diet volume and number of food items per stomach were significantly larger in April than in August. The proportion of frequency of occurrence (FOi%) of food categories did not show a constant food item in flushed materials. Pelophylax ridibundus prefers Diptera, Coleoptera, Amphipoda and Hymenoptera over other food categories. The Index of Relative Importance (IRI) for food categories differs between sexes and seasons. Differences were found in the food volume and the number of food items between seasons, but not between sexes. Prey volume is positively correlated with frog size.     

The diet of the King Penguin Aptenodytes patagonicus at Macquarie Island

The diet of King Penguins Aptenodytes patagonicus at Macquarie Island was studied between November 1984 and November 1985 based on stomach flushed samples (obtaining 93% of the total stomach content) from ten birds each month. The mean stomach content mass of the 118 samples was 923 0 g. Percentage by number, percentage by weight and dietary coefficient analysis all showed the main prey of the penguins to be myctophid lantern fish of the species Electrona carlsbergi and Krefftichthys anderssoni. Juvenile fish of both species were eaten from December to July, and adults in August and September. Cephalopods were relatively unimportant in contrast to previous indications. The amount of food brought ashore and the composition of the diet varied over the year, with K. anderssoni the dominant food in all but the winter months when E. carlsbergi replaced it as the principal food item.     

Do lizard communities partition the trophic niche? A worldwide meta‐analysis using null models

Lizards have been widely used as model organisms in community ecology over the past 30 years. I have reviewed more than 50 studies from the literature on the community ecology of lizards worldwide, with a focus on studies from 1990–2007. I determined if there is support for the hypotheses that many lizard communities 1) are non‐randomly organized along the trophic niche dimension, and 2) partition the available food resource to minimize interspecific competition. I used data on number of prey items and percentage of prey volume, to calculate dietary overlap among species. I compared true datasets to randomly generate new datasets produced by 3×10⁴ Monte Carlo permutations using two algorithms (RA2 and RA3). The great majority (more than 80%) of the communities were randomly organized along the trophic niche dimension using RA2 or RA3; the frequency of occurrence of detecting a non‐random structure in lizard community dietary studies did not differ significantly between datasets based on either number of prey items or prey volume. Thus, lizard communities usually do not partition the trophic niche axis. Concerning the number of prey items, logistic regression models showed that the presence of a structure in the dataset did not depend on number of species, method employed to obtain dietary data, matrix size, or location (continent), but instead significantly depended on whether a community was tropical. Concerning prey volume, presence of a structure in the dataset also did not depend on number of species, method employed to obtain dietary data, and tropical vs non‐tropical origin, but was marginally dependent on continent (South America was favoured for identifying a structure in the dataset) and matrix size. In general, a structure in the dataset was more often uncovered by using RA2 than RA3. Overall, I conclude that 1) lizard communities are unlikely to partition available food resources, and 2) as the method for identifying dietary items does not allow for accurate prey identification (at least at the genus level), there is a risk of obtaining false null results about community structure. This is because structure along the trophic niche axis is genuinely rare in lizards and also because inappropriate methods may erroneously lead to this conclusion. Therefore, conclusions from studies utilizing stomach dissection as a source of diet data (still common in the literature) should be cautiously considered for ethical reasons and because it is difficult to find any difference between stomach‐dissection and fecal‐pellet data when assessing the presence of a structure in datasets. My data also showed there are minor differences in the probability of detecting a structure in datasets using prey item number or prey volume data for lizards. The biases, both statistical and biological, associated with this meta‐analysis are discussed.     

Diet of brown-nosed coatis and crab-eating raccoons from a mosaic landscape with exotic plantations in southern Brazil

We described the diets of two procyonids, the brown-nosed coati Nasua nasua and the crab-eating raccoon Procyon cancrivorus, through analysis of stomach contents of road-killed specimens in southern Brazil. We compared them with previously published dietary information for another syntopic mesopredator, the crab-eating fox Cerdocyon thous. The landscape of the study area includes native grasslands, forests, exotic tree plantations, and other crops. Food items were represented by frequency of occurrence (FO) and relative volume (RV). Stomach contents of 23 coatis were analyzed. Animal and plant items were equally frequent, although the volume of plants was greater. Exotic plant species were consumed more than native plants. Among prey items, invertebrates were more important than vertebrates, mainly because of the frequency of coleopterans and annelids and the volume of necrophagous dipteran larvae. Five specimens of raccoons were analyzed, in which animal items had the highest FO and plant items had the highest RV. Both invertebrate and vertebrate prey had the same FO, although vertebrates had a higher RV. Our data suggest that these procyonids are opportunistic hypocarnivores, utilizing anthropic sources, with diet overlap. The coatis also overlapped their diet substantially with the foxes. The stomach-contents analysis revealed the importance of fruit pulp biomass, soft-bodied animals such as larvae, and also soil, which might indicate feeding habits such as scavenging and geophagy.     

More on the validation of fecal samples for the large-scale study of dietary differences between two sympatric carnivores

Prey occurrence from stomach and fecal samples were compared in American martenMartes americana Turton, 1806, and fisherM. pennanti Erxleben, 1777. Diets were analyzed from stomach and fecal contents in four sex-age marten groups and four fisher groups, and dietary differences tested between species, sex, age and sample sources. Prey richness was compared between the two sample sources. Relative occurrence of dominant or co-dominant prey items did not differ between stomach and fecal samples in any of the groups. However, both series revealed inter-specific contrasts. Binomial correlations of prey occurrence between sample sources were significantly negative for most prey items. Correlations of prey richness between samples sources were not significant except in larger marten sample. Our results failed to reveal a bias in using fecal sample source. Thus we suggest that diet analyses using either sample source are valid when diets are assessed in a relatively large number of animals.     

Food consumption and diet composition of cod,Gadus morhua,inhabiting the southwestern Gulf of St. Lawrence

Synopsis Stomach content analysis of commercial size cod, Gadus morhua, inhabiting the southwestern Gulf of St. Lawrence are presented for the period May to November 1980. Season- and size-related changes in the diet composition are indicated and the results compared to those of earlier studies. The extent of cod predation on major prey groups is evaluated by estimating their consumption by cod age-groups 3–15. The evaluation is based on the estimate of food intake by individual cod of different ages derived with the aid of a procedure based on Ursin growth theory, estimates of numbers-at-age from cohort analysis and the results of stomach content analysis.With the exception of American plaice, Hippoglossoides platessoides, and snow crab, Chionoecetes opilio, the consumption of commercially important species was relatively low and restricted to older cod. Commercially important species accounted for less than 12% of the total food biomass consumed by cod during the study period. The remainder consisted of other fish (18%), decapods (22%), euphausiids (15%), molluscs (11%), annelids (8%), and other invertebrates (15%). Methods are suggested to improve the above estimates of total and individual prey biomasses consumed by the fish population.     

Utilizing stomach content and faecal DNA analysis techniques to assess the feeding behaviour of largemouth bass Micropterus salmoides and bluegill Lepomis macrochirus

In this study, the feeding behaviour of the non‐native invasive predatory fishes largemouth bass Micropterus salmoides and bluegill Lepomis macrochirus was studied in the Ezura River, a northern tributary of Lake Biwa, Japan. Prey composition was estimated based on visual examination of stomach contents and faecal DNA analysis to determine feeding habits of these predatory fishes. Stomach content analysis showed that native fishes (e.g. ayu Plecoglossus altivelis and gobies Rhinogobius spp.) and shrimps (e.g. Palaemon paucidens) were the major prey items for M. salmoides, while snails, larval Chironomidae and submerged macrophytes were the dominant prey items of L. macrochirus. Micropterus salmoides tended to select larger fish in the case of crucian carp Carassius spp., but smaller fishes in the case of P. altivelis and Rhinogobius spp. Faecal DNA analyses revealed prey compositions similar to those identified in predator stomach contents, and identified additional prey species not detected in stomach content inspection. This study demonstrated that both stomach content inspection and DNA‐based analysis bear several inherent shortcomings and advantages. The former method is straightforward, although identification of species can be inaccurate or impossible, whereas the latter method allows for accurate species identification, but cannot distinguish prey size or stage. Hence, integration of morphology‐based and DNA‐based methods can provide more reliable estimates of foraging habits of predatory fishes.     

Stable isotope analysis as a tool to monitor dietary trends in little penguins Eudyptula minor

Long‐term dietary monitoring of seabirds can be used to relate population fluctuations to at‐sea events. Stomach flushing is a conventional dietary monitoring technique, but has a number of disadvantages. Stable isotope analysis (SIA) is a less invasive method that provides unbiased dietary information over a longer period. We evaluated stable isotope analysis as a potential tool for monitoring long‐term little penguin Eudyptula minor diet. We determined diet composition during the chick feeding stage using stomach flushing and SIA at three separate colonies, using spatial variation in diet as a surrogate for potential temporal variation. Bayesian isotopic mixing models were generated for blood and feathers to evaluate their ability to discriminate broad‐scale (fish, squid, crustaceans) and fine‐scale (individual prey species) diet composition. Differences in stable carbon and nitrogen isotope ratios were found between colonies: broad‐scale isotopic mixing models predicted different proportional contributions of broad taxa (fish, cephalopod, crustacean) to diet than was indicated by stomach samples, reflecting the bias incurred by one‐off stomach contents analysis. Fine‐scale isotopic mixing models predicted proportional contributions of prey items with less certainty. Blood isotopic mixing models had narrower confidence intervals than models for feathers, but trends in δ¹⁵N for feathers mirrored those for blood. Our results suggest that relying on stomach contents analysis to detect shifts in prey consumption in little penguins could be very misleading, resulting in a less‐than‐complete idea of total prey consumption. SIA of little penguin tissues could be used to monitor dietary shifts across dissimilar taxa that may affect population numbers, but would fail to detect shifts between fish species.