Density and carrying capacity in the forgotten tigerland: Tigers in the understudied Nepalese Churia

While there are numerous wildlife ecology studies in lowland areas of Nepal, there are no in‐depth studies of the hilly Churia habitat even though it comprises 7642 km² of potential wildlife habitat across the Terai Arc. We investigated tiger, leopard and prey densities across this understudied habitat. Our camera trapping survey covered 536 km² of Churia and surrounding areas within Chitwan National Park (CNP). We used 161 trapping locations and accumulated 2097 trap‐nights in a 60‐day survey period during the winter season of 2010–2011. In addition, we walked 136 km over 81 different line transects using distance sampling to estimate prey density. We photographed 31 individual tigers, 28 individual leopards and 25 other mammalian species. Spatial capture–recapture methods resulted in lower density estimates for tigers, ranging from 2.3 to 2.9 tigers per 100 km², than for leopards, which ranged from 3.3 to 5.1 leopards per 100 km². In addition, leopard densities were higher in the core of the Churia compared to surrounding areas. We estimated 62.7 prey animals per 100 km² with forest ungulate prey (sambar, chital, barking deer and wild pig), accounting for 47% of the total. Based on prey availability, Churia habitat within CNP could potentially support 5.86 tigers per 100 km² but our density estimates were lower, perhaps indicating that the tiger population is below carrying capacity. Our results demonstrate that Churia habitat should not be ignored in conservation initiatives, but rather management efforts should focus on reducing human disturbance to support higher predator numbers.     

抚育间伐对小兴安岭天然针阔混交次生林生境的影响

以小兴安岭地区天然针阔混交次生林为研究对象,进行不同间伐强度、不同间伐带宽的抚育改造,选取各样地土壤因子、枯落物持水因子、物种多样性因子和冠层结构因子共38项评价指标进行分析。运用主客观赋权的方法确定指标权重,采用层次分析法确定主观权重,熵权法确定客观权重,最小信息熵法确定组合权重,最后对生境因子进行单独评价以及综合评价。结果表明:运用组合权重法得到各生境因子的权重大小,按重要性排序为土壤化学性质(0.370),枯落物持水性能(0.231),冠层结构(0.166),物种多样性(0.129),土壤物理性质(0.104)。不同抚育间伐强度和间伐带宽对各改造样地生境因子的影响程度不同。在间伐强度为15%、间伐带宽为10 m时枯落物持水性能最好,综合评价值为3.510;在间伐强度为20%、间伐带宽为18 m时土壤化学性质、冠层结构最佳,综合评价值分别为2.796、0.953;在间伐强度为30%的情况下,间伐带宽为10 m时群落物种多样性程度最优,综合评价值为1.820,带宽为18 m时土壤的物理性质优于其他样地,综合评价值为7.943。通过综合评价得出小兴安岭天然针阔混交次生林在抚育间伐强度为20%,间伐带宽为18 m时的森林生境最佳。从整体来看,抚育间伐大大改善了森林生境条件,为林内生物提供了良好的生存环境,此研究为天然次生林生态经营提供了很好的理论依据。      

Seasonal habitat requirements of Lemon Dove (Aplopelia larvata) in coastal forest: camera-trap surveys of a reclusive species

The modification of natural habitats requires behavioural plasticity, which may be challenging for ‘specialist’ species. Quantifying habitat requirements and behavioural responses of specialists to landscape transformation is thus a priority for baseline data to inform conservation practices. Using camera-trap surveys of the forest-dependent Lemon Dove Aplopelia larvata in conjunction with detailed microhabitat-scale covariates, we assessed habitat use during two periods in the year: autumn–winter and spring–summer (which largely encompassed peak breeding). We used occupancy modelling of forest-structural covariates to produce models of the probability of occupancy and detection of Lemon Doves in patches of the Indian Ocean Coastal Belt Forest of South Africa. The average occupancy and detection probability as indicated by the top-performing models was 0.39 ± 0.08 and 0.26 ± 0.05, respectively, during autumn–winter, and 0.37 ± 0.08 and 0.25 ± 0.04, respectively, during spring–summer. Although occupancy and probability of detection remained relatively constant between seasons, there was seasonal variation in the influence of individual covariates for both measures. The overall trend of positive influences on Lemon Dove occupancy was that of complex and diverse habitat structures and high plant species richness. The specific covariates that influenced occupancy positively during spring–summer may reflect the ecological requirements for nestling provisioning for both dietary needs and an avoidance of potential disturbance. Thus, while Lemon Doves may be less habitat-specific during autumn–winter, conservation management plans for safeguarding the breeding success of the species are advised to ensure adequate protection of large forest patches with complex and diverse interior structures and minimal disturbance.     

邛海湿地黑水鸡春季生境选择

2014年4~5月,在四川省西昌市邛海湿地的梦里水乡、焦家村-月亮湾、烟雨鹭洲、小渔村等区域选取了60个10 m×10 m黑水鸡(Gallinula chloropus L.)利用样方进行植被类型、明水面、水深、人为干扰距离、草本植物高度、草本植物密度、乔木距离、食物丰富度8个生态因子的生境选择分析。结果表明,黑水鸡喜植被茂盛、密度大、高度适中的隐蔽生境;就食物而言,黑水鸡尤喜水浅且食物丰富的水域,对明水面的选择不明显;干扰因素研究表明,人为活动对黑水鸡的影响不大,而人为活动稀少区域的黑水鸡对干扰稍显敏感。主成分分析结果显示,影响黑水鸡春季生境选择的因素主要有隐蔽性、食物多寡以及干扰程度。     

中西太平洋鲣栖息地指数预报模型比较研究

鲣(Katsuwonus pelamis)是太平洋热带海域重要的金枪鱼种类之一,也是目前我国金枪鱼围网渔船的主要捕捞对象之一。根据1995—2012年中西太平洋海域(5°N-10°S;125°E-135°W)延绳钓生产统计数据,结合海表面温度(SST)和海表面高度(SSH)的遥感数据,利用频次分布法分析了中西太平洋围网鲣分布的SST和SSH适宜范围;采用了外包络法,按季度分别建立了SST、SSH的适应性指数(SI),采用算术平均法(AMM)和几何平均法(GMM)建立栖息地指数(HSI)模型计算其栖息地指数,并用2013年度的捕捞数据进行验证。结果表明,中西太平洋围网鲣多分布在SST为28~30.5℃、SSH为65~95 cm的海域。以捕捞努力量(作业天数)为基础,采用外包络法建立SST、SSH的适应性指数最为合适,各个季度的SST权重分别为0.7、0.6、0.3、0.6的算数平均法适合中西太平洋围网鲣栖息地指数模型。不同季节的环境因子对中西太平洋围网鲣渔场分布有着不同的影响。     

海南霸王岭国家自然保护区拟石斛的附生特性

拟石斛(Oxystophyllum changjiangense)为海南岛特有的珍稀濒危附生兰科植物。为阐明其附生特性,笔者以分布于海南省霸王岭国家自然保护区的拟石斛为例,在系统调查其资源现状、生境特征及宿主种类的基础上,对其附生宿主的专一性、在宿主上的分布特点及附生个体数量与宿主胸径、树皮特性的相关性等进行分析。结果表明,86.6%的拟石斛个体分布在海拔800~1 000 m且主要附生在山地雨林中水源附近的高大乔木上;附生宿主18种,多见于木兰科、壳斗科、漆树科及梧桐科的植物;附生指数在0.32~0.94之间,其中白花含笑、长柄梭罗和红锥的附生指数接近于1;拟石斛全都分布在宿主的一级分支或二级分支处,二者差异性不显著;附生数量与宿主胸径呈显著性正相关(R=0.397,P0.05),拟石斛对树皮特性选择具有偏好性。     

多种数据源下栖息地模型及预测结果的比较

由于多来源的海洋环境数据常以不同时间、空间分辨率呈现,并具有不同的误差,因此,有必要分析数据源的差异是否会对研究结果产生显著影响,是否会影响基于不同数据源估计的模型对其他数据的适用性。为此,本研究利用多个网站提供的叶绿素浓度与海表水温数据,采用线性回归与随机检验方法,分析了不同数据源对栖息地模型构建及其预测效果的影响。研究结果表明,不同数据源的数据之间常存在系统性偏差,从而使得模型参数的估计具有显著性差异,该模型不适合于其他数据源的数据;多源环境数据间的离散性反映数据存在随机误差,环境数据的随机误差将使模型结果具有随机性,因此本研究建议定量分析模型结果的不确定性,以使模型结果得到科学应用。     

Predicting use of habitat patches by spawning horseshoe crabs (Limulus polyphemus) along a complex coastline with field surveys and geospatial analyses

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Changes in habitat use patterns by bottlenose dolphins over a 10‐year period render static management boundaries ineffective

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Estimation of habitat suitability for the southern form of the short‐finned pilot whale (Globicephala macrorhynchus) in the North Pacific

Habitat models were developed from dedicated sighting survey data collected during summers between 1983 and 2006 in the North Pacific Ocean. Our aim was to examine the distribution pattern of the southern form of the short‐finned pilot whale (Globicephala macrorhynchus) in relation to the physical environment. We tested two different types of analytical procedures for habitat estimation: generalized linear models (GLMs) and ecological niche factor analysis (ENFA). The area under the receiver operating characteristic curve and the Boyce index suggested that GLM defined the core habitat well, whereas ENFA estimated the suitable habitat more correctly. These models indicated the core habitat within the subtropical gyre. Among the environmental variables used to construct the habitat models, the temperature at a depth of 200 m contributed most to both GLM and ENFA. This corresponds to the fact that the species mainly feeds on mesopelagic prey and that the axis of the Kuroshio Current, in the northwestern part of the subtropical gyre, is characterized by its temperature at 200 m. Habitat suitability in the coastal waters off southern Japan also correlated with the Kuroshio meander patterns. Thus, the southern form of the short‐finned pilot whale appears to be particularly well adapted to the ecosystem of the North Pacific subtropical gyre.