鄂尔多斯地区密点麻蜥的食性分析

对采自内蒙古自治区鄂尔多斯库布齐沙漠85只密点麻蜥Eremias multiocellata,采用胃剖法作食性分析,分别计算出它们的食物数量和频次百分比、营养生态位宽度、营养生态位重叠值和有益系数等。结果显示,密点麻蜥以觅食昆虫为主,其次为蛛形类和植物种子;其中包括2纲13目41科的节肢动物门物种。雌、雄个体的取食食性差异不显著,但幼体、亚成体和成体间食性有显著的差异。雌、雄个体的营养生态位重叠值较大。亚成体的营养生态位宽度与食物多样性指数最大,而成体最小。密点麻蜥的总有益系数为正值,表明该物种摄食较多的害虫。     

草原沙蜥秋季食性分析

利用剖胃法对采自内蒙古自治区鄂尔多斯库布齐沙漠的草原沙蜥(Phrynocephalus frontalis)进行食性分析研究。结果表明,该地区的草原沙蜥在8～9月间,以昆虫类动物为主要食物,占全部食物的95.8%。不同性别草原沙蜥取食的食物种类差异不显著,雌雄个体的食物百分率相似性指数及营养生态位重叠值均较大,雄性的食物多样性指数(IFD)及营养生态位宽度(BTN)均大于雌性。成体和亚成体之间以及亚成体和幼体之间食物种类存在差异但不显著,而成体和幼体间的食物种类差异极显著,不同年龄草原沙蜥的食物百分率相似性指数较小,IFD值与BTN值均是成体最大,幼体最小。总有益系数、不同性别的有益系数分别为V总=22.44%,V雌=12.76%,V雄=9.83%,草原沙蜥是对荒漠化草原有益的类群。     

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。     

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。     

种群外部及内部因子对东方田鼠巢区大小的效应

在野外围栏条件下, 采用重复的2×2×2析因实验, 测定外部和内部因子对东方田鼠(Microtus fortis)巢区大小的作用模式。研究结果表明, 雄体巢区大小显著大于雌体巢区大小。雄体巢区大小与体重存在显著的正相关, 而雌体巢区大小与体重的相关不显著; 雄体和雌体巢区大小与种群数量均呈显著的线性负相关。外部因子对东方田鼠雄体和雌体巢区大小的作用不一致。在排除内部因子种群数量及体重对雄体巢区大小作用的条件下, 食物对雄体巢区大小的作用显著; 而捕食及种间竞争的独立作用及其交互作用, 以及3 种外部因子的交互作用均不显著; 在排除种群数量对巢区大小作用的条件下, 食物与捕食的独立作用及3 种外部因子的交互作用对雌体巢区大小的效应均达到显著水平, 食物与种间竞争的交互作用接近显著, 而种间竞争的独立作用、食物和捕食的交互作用, 以及捕食与种间竞争的交互作用对雌体巢区大小的效应均不显著。本文结果验证了种群外部因子食物、捕食及种间竞争、种群内部因子种群数量及个体体重对田鼠种群巢区大小具有独立和交互作用的假设。     

高原鼠兔间断性移动模式与反捕食对策分析

本文采用直接观测法,测定了高原鼠兔地面移动频率及每次移动距离。结果表明,高原鼠兔地面移动频率和每次移动距离依繁殖时期、年龄及性别而存在极显著的差异。繁殖早期,成年雄体地面活动频率大于成年雌体。繁殖后期,第1胎雄性幼体大于同年龄的雌体。繁殖早期,成年雌体地面活动频率高于繁殖后期,而幼体与成体之间无显著的差异。繁殖初期雄体每次移动距离大于雌体,其它时期雌、雄体之间则无明显的差别。雄体每次移动距离逐月降低。雌体每次移动距离无显著的季节性差异。研究结果进一步验证了暴露于风险环境中的植食性小哺乳动物,主要采取间断性移动模式,增加反捕食时间投入,降低风险的假设。     

多疣壁虎的繁殖生态研究

多疣壁虎(Gekko japonicus)是一种季节性繁殖的爬行动物,性腺活动状态在不同的季节有显著的差异。成年雌体在冬眠结束后的4月初卵巢开始增大,野外产卵期一般在5月下旬至8月上旬。一个繁殖期平均产卵1.8窝,每窝恒定两枚。每窝卵重与个体大小之间存在着显著的正相关,大个体的产卵频率亦较高。雄体的精巢重量和大小的月间差异显著,但变化不及雌体的卵巢显著。雌体的繁殖期可以被环境温度所改变。繁殖效力用每窝卵干、湿重及能值与雌体干、湿重及能值的比值估算。     

山地麻蜥主要贮能部位水分含量和能值的年变化

研究了安徽宿州山地麻蜥主要贮能部位水分含量和能值的年变化。蜥蜴分别于2001年9-11月和2002年3—8月逐月捕回,经测量、称重后解剖分离为躯干(包括尾)、肝脏和腹脂肪体三组分。所有样品65℃恒温干燥至恒重,用索氏脂肪提取器测定脂肪含量,微电脑热量计测定能值。本研究结果显示：雄体躯干、肝脏水分含量显著高于雌体,躯干、肝脏水分含量的月间差异显著;雄体躯干、脱脂躯干能值显著高于雌体,躯干、脱脂躯干能值的月间差异显著;雄体肝脏能值、脱脂肝脏能值以及腹脂肪体能值显著低于雌体,肝脏能值、脱脂肝脏能值以及腹脂肪体能值的月间差异显著。上述结果表明,山地麻蜥躯干、肝脏以及腹脂肪体能值的年变化与繁殖和冬眠关系密切,繁殖期雄体适度贮能有利于提高运动的敏捷性;雌体适度贮能有利于增加繁殖输出,提高野外生存和适应性。     

挂榜山小鲵的繁殖生态

2004-2006年对挂榜山小鲵(Hynobius guabangshanensis)的繁殖生态进行了观察研究.结果表明:挂榜山小鲵繁殖期为每年的11月中旬至翌年1月;非繁殖期营陆生生活,繁殖期进入水中繁殖;繁殖期活动高峰为20:00到翌日6:00;繁殖种群数量为198条,现存分布区不足10 km2;繁殖期雌雄性比为1.6,存在明显的两性异型,性成熟雌体的体长和体质量显著大于雄体;挂榜山小鲵的抱对行为与东北小鲵、黑小鲵、极北鲵相似;雄体具有求偶炫耀行为和精子竞争行为;繁殖场多为临时水凼和小而浅的池塘,大部分卵袋被固定在浅水的枯枝和水草上;挂榜山小鲵的卵袋较同科物种粗大,幼体刚出膜时卵袋长(18.40±4.21) cm(n=31),直径(4.23±0.52) cm(n=31);卵径(2.10±0.25) mm(n=45);卵粒数(88.90±20.30)个(n=98)(单个卵袋),受精率为(93.3±21.4)%(n=98).     

大树蛙繁殖生态的研究

大树蛙的繁殖期在长沙岳麓山地区是4月15—30日前后的十多天时间内,一般是午夜后开始产卵、黎明前产完。产卵场要求静水水域,其上有依附植物,湿度较大。其他条件依各地而异。 在某个期间,产卵场内雄体占绝对优势,但在整个繁殖期内参加繁殖的雌雄个体数量和差不很大。 交配产卵:雌体伏于静水水域上空枝叶上,雄体伏于雌体背侧,并以前肢紧抱雌蛙腋窝,泄殖孔互相靠近。雌体排卵及输卵管分泌物是一阵一阵排出的,排出时以后肢搅拌分泌物起泡,与此同时雄体排精,并以后肢刮净泄殖孔,大腿周围的卵及输卵管分泌物,左右后肢把这些分泌物搓擦起泡。大树蛙在年繁殖期内是一次性产卵。 大树蛙产出的卵及输卵管分泌物形成特殊的卵泡,卵泡为泡沫状粘液构成,刚产出时呈乳白色,表面干燥后污黄色。卵的动物极略呈淡黄绿色,植物极白色,卵经为2—2.2毫水左右,比重大于1。一般每雌产卵一千多到二千多粒。大树蛙的卵泡常成群分布。 在常温下大树蛙的受精卵在第4天孵化,小蝌蚪落入水中发育,大约50天左右出现后肢,61天左右出现前肢,再过1—2天就登陆,但大树蛙蝌蚪发育不整齐,最迟可到3个月之后才登陆。     

Effects of Sexual Dimorphism and Landscape Composition on the Trophic Behavior of Greater Prairie-Chicken

Partitioning of ecological niche is expected in lekking species that show marked sexual size dimorphism as a consequence of sex-specific ecological constraints. However, niche partitioning is uncertain in species with moderate sexual dimorphism. In addition, the ecological niche of a species may also be affected by landscape composition; particularly, agricultural fragmentation may greatly influence the trophic behavior of herbivores. We studied trophic niche variation in Greater Prairie-Chickens (Tympanuchus cupido), a grouse species that shows moderate sex-dimorphism. Greater Prairie-Chickens are native to tallgrass prairies of North America, although populations persist in less natural mosaics of cropland and native habitats. We used stable isotope analysis of carbon and nitrogen in blood, claws and feathers to assess seasonal differences in trophic niche breadth and individual specialization between male and female Greater Prairie-Chickens, and between birds living in continuous and fragmented landscapes. We found that females showed broader niches and higher individual specialization than males, especially in winter and autumn. However, differences between females and males were smaller in spring when birds converge at leks, suggesting that females and males may exhibit similar feeding behaviors during the lekking period. In addition, we found that birds living in native prairies showed greater annual trophic variability than conspecifics in agricultural mosaic landscapes. Native habitats may provide greater dietary diversity, resulting in greater diversity of feeding strategies.     

The coexistence of fish species in streams: relationships between assemblage attributes and trophic and environmental variables

Diet overlap and niche breadth are well-known species traits from trophic ecology that can assist in explaining how species interact and coexist as well as the ecological mechanisms that influence biodiversity. In the present study, we analyzed the relationships between these trophic variables and indicators of resource availability with some attributes of fish assemblages (species richness, Shannon diversity index, evenness, density and individual body size). The physical and chemical characteristics of the biotopes (topography, water quality and conservation of slopes) were examined to identify possible patterns. Monthly sampling using electrofishing was conducted in 2003 along five streams located in the Cuiabá River watershed. The relationships between environmental variables and attributes of fish assemblages were evaluated using Spearman correlation. Species richness and abundance varied among streams, with higher values (54 and 82 species) found in low-gradient streams that drained small swampy areas discharging in Cuiabá River. Diet overlap showed significant and negative correlations with species richness, the diversity index, abundance, variation in body size and food availability and positive correlations with evenness and niche breadth. Environments that had greater food availability had a reduced variety of food items (smaller amplitude) and distinct values in terms of dietary overlap. Nevertheless, to explain resource partitioning in a fish assemblage (overlap), it is necessary to consider food availability and niche breadth (degree of trophic specialization) beyond the interaction of these variables with species richness and density. In conclusion, high diversity and abundance values were strongly associated with a high degree of trophic specialization (low amplitude of trophic niche) and a small degree of overlap in the diet.     

Niche breadth and trophic diversity: feeding behaviour of the red swamp crayfish (Procambarus clarkii) towards environmental availability of aquatic macroinvertebrates in a rice field (Portugal)

The red swamp crayfish, Procambarus clarkii (Girard 1852), an alien species in Portugal, may have dramatic effects on aquatic communities by depleting all food resources available, just after its introduction. The purpose of this study was to evaluate, through the concept of niche breadth, whether the diet of this species reflected the temporal changes of aquatic macroinvertebrate availability once it is acclimated. Petraitis’ index of niche breadth and Herrera’s trophic diversity index were used to evaluate the trophic behaviour of P. clarkii towards available resources over time and intraspecifically (size classes and sex) in a rice field in Portugal. Results from this study showed that the consumption of aquatic macroinvertebrates by P. clarkii reflected their seasonal availability. The high values of niche breadth and trophic diversity indicated resource use according to trophic availability, diversified diets and different individual exploitation of resources regardless of size or sex. These findings suggest that in habitats where P. clarkii is already acclimated, it adjusted its trophic behaviour to the seasonal availability of aquatic macroinvertebrates. The large niche breadth and high trophic diversity presented by P. clarkii enables it to successfully expand its range to new areas, when other environmental conditions are favourable, as has been observed in Portugal and worldwide.     

Niche separation in Varecia variegata rubra and Eulemur fulvus albifrons: II. Intraspecific patterns

Based on a year-long field study in northeastern Madagascar, I summarize annual patterns of niche use (food patch size, diet, forest height, and forest site) in two sympatric lemurs, Varecia variegata rubra and Eulemur fulvus albifrons. Furthermore, I examine intraspecific patterns of niche use according to sex, season, and reproductive stage in these two lemurs that differ in terms of energetic investment in reproduction. Lemurs as a group provide a special opportunity to test hypotheses concerning sex differences in niche use. Due to their body size monomorphism and seasonal, synchronous pattern of breeding, it is possible to directly evaluate whether sex differences in diet reflect high energetic investment in reproduction by females. Results confirm the hypothesis that intraspecific variation in niche use (e.g., sex differences, seasonal differences) would be more pronounced in V. v. rubra than in E. f. albifrons, due in large measure to the former's relatively high energetic investment in reproduction: 1a) Dietary sex differences in V. v. rubra are most pronounced during costly reproductive stages and involve acquisition of low-fiber, high-protein plant foods. Females of both species consume more seasonally available low-fiber protein (young leaves, flowers) relative to conspecific males during the hot dry season, but only in V. v. rubra females is this pattern also evident during gestation and lactation. 1b) The diets of female V. v. rubra and female E. f. albifrons are more similar to each other than are the diets of conspecific males and females in the case of V. v. rubra. This is not uniformly the case for female E. f. albifrons. This finding confirms a hypothesis put forward in Vasey ([2000] Am J Phys Anthropol 112:411-431) that energetic requirements of reproductive females drive niche separation more than do the energetic requirements of males. 1c) Both species synchronize most or all of lactation with seasonal food abundance and diversity. E. f. albifrons shows a more protracted period of synchrony, and this may contribute to its wide biogeographic distribution in Madagascar. 2) Sex differences and seasonal differences in microhabitat use reflect intraspecific patterns of thermoregulation, predator avoidance, and in the case of V. v. rubra, reproduction. One important factor selecting for body size monomorphism in lemurs appears to be the tight synchrony between lactation and periods of food abundance afforded by annual, seasonal breeding.     

Non-linear relationship between body size of terrestrial carnivores and their trophic niche breadth and overlap

Studying food partitioning of mammalian predators is important for understanding trophic structures and interactions between coexisting carnivore species. This is particularly pertinent in the light of expanding ranges of populations of generalist species whose habitat and diet overlap with more specialized species. Here, we tested the resource partitioning hypothesis in terrestrial carnivores, predicting that trophic niche breadth and overlap relate positively to body mass. We used dietary data from 18 terrestrial carnivore taxa in four families (Canidae, Mustelidae, Felidae and Ursidae; body mass 0.1–173.6 kg) in three regions in Central and Eastern Europe, i.e. deciduous forest and forest-steppe region (DFR), temperate deciduous and mixed forest region (MFR) and transitory mixed forest regions (TFR). We ranked carnivores along an axis of trophic niche (breadth and overlap), and analysed the relationship between trophic niche and body mass (or pair-wise difference in body mass). A hierarchical cluster analysis of diet composition divided carnivores into four ecological groups: wild ungulate predators; small-mammal predators; amphibians and small mammal predators and omnivores. The relationship between body mass of predators and both trophic niche breadth and trophic niche overlap were hump-shaped. The trophic niche breadth to body mass ratio was significantly lower in DFR than in TFR and trophic niche overlap was significantly higher in DFR than in MFR and TFR. The predominant food resource is small mammals whose abundance is related to local agricultural and forestry management practices. Modifications of management techniques can affect population dynamics and community composition of carnivore species, especially in the case of small-mammal predators.     

河北唐海湿地四种鹭的种群动态和繁殖空间生态位

2004年8月—2005年7月对河北唐海湿地夜鹭(Nycticoraxnycticorax)、白鹭(Egtettagarzetta)、池鹭(Ardeolabacchus)、大白鹭(Casmerodiusalbus)的种群动态和繁殖行为进行了观察,并对巢群关系进行了研究。统计了4种鹭垂直和水平巢位的巢密度,计算了不同种鹭巢的生态位重叠、生态位宽度值。结果4种鹭在唐海数量最多月份为4—9月,最大量达到了近5800只。共有Ⅰ、Ⅱ两个巢区,迁来Ⅱ区时间较Ⅰ区晚半个月左右。除池鹭外,3种鹭之间均有争巢现象,后期趋于稳定。迫于密度压力和竞争,部分白鹭和池鹭取食范围较广。除大白鹭外,其他3种鹭同种间均有混交现象。在混巢区,夜鹭迁来最早,数量最大,为优势种,多数占据中心区的顶巢;大白鹭数量最少,亦占据中心区的顶巢;白鹭迁来较晚,占据中位巢;池鹭迁来最晚,数量较白鹭少,多数在边缘区单独筑巢,少数在中心区占下位巢。白鹭巢的垂直生态位最宽;夜鹭巢的水平生态位最宽;池鹭巢的综合空间生态位最宽。池鹭和夜鹭巢位的空间格局最为相似,池鹭和白鹭的生态位重叠较大。夜鹭的数量最多、大白鹭的个体最大,导致其处于优势;白鹭和池鹭数量少、个体小,导致其处于劣势。唐海湿地内丰富的食物和适宜的林带是鹭鸟密度较大的主要原因。此外,鹭类只筑巢在散布的、双行杨树林带均高为22m以上区域,是该地鹭类巢区的主要特点。     

Competition versus opportunism: Diet and trophic niche relationship of two sympatric apex carnivores in a tropical forest

There is a little understanding of how apex carnivores partition their diet to coexist. We studied food habit and trophic niche overlap of two apex carnivores, tiger and leopard in the tropical forest of Similipal tiger reserve, eastern India. We used line transect and scat analysis method, to estimate the prey availability and determine the diet and prey selection of two apex carnivores. Tigers consumed mostly large and medium-sized prey, whereas leopards mostly consumed medium and small-sized prey. Both carnivores were not random in their consumption of prey, sambar and wild pigs were selectively consumed by tigers, whereas leopards selectively consumed wild pigs, barking deer and mouse deer. Dietary overlap between two carnivore species was moderate (Pianka's niche overlap index: 0.55), and trophic niche breadth (Levin's standardized niche breadth) of the leopard (0.52) was greater than that of the tiger (0.37). Overall, tigers exhibited specialized feeding habits, whereas leopards showed generalist feeding habits. Our study highlights the opportunistic nature of leopards and probably a reason for the species successfully coexist with tigers.