Cost-effective abundance estimation of rare animals: Testing performance of small-boat surveys for killer whales in British Columbia

Top predators are often rare, subject to anthropogenic mortality, and possess life-history traits that make them inherently vulnerable to extinction. IUCN criteria recognise populations as Critically Endangered when abundance is <250 mature individuals, but estimating abundance of rare species can be more challenging than for common ones. Cost-effective methods are needed to provide robust abundance estimates. In marine environments, small boats are more widely accessible than large ships for researchers conducting sightings surveys with limited funds, but studies are needed into efficacy of small-boat surveys. This study compares line transect and mark-recapture estimates from small-boat surveys in summer 2004 and 2005 for ‘northern resident’ killer whales in British Columbia to true population size, known from censuses conducted by Fisheries and Oceans Canada. The line transect estimate of 195 animals (95% CI 27-559) used model averaging to incorporate uncertainty in the detection function, while the mark-recapture estimate of 239 animals (CI 154-370) used a simple two-sample Chapman estimator. Both methods produced estimates close to the true population size, which numbered 219 animals in 2004 and 235 in 2006, but both suffered from the small sample sizes and violations of some model assumptions that will vex most pilot studies of rare species. Initial abundance estimates from relatively low-cost surveys can be thought of as hypotheses to be tested as new data are collected. For species of conservation concern, any cost-effective attempt to estimate absolute abundance will assist status assessments, as long as estimates are presented with appropriate caveats.     

金坛市土地生态质量的城乡梯度规律研究

金坛市作为长三角经济发达地区的典型地区,快速城镇化背景下其土地生态状况具有代表性。从基础、胁迫、结构、效益4个角度构建土地生态指数指标体系,以行政村为评价单元计算4个准则层分值和土地生态指数综合分值,在此基础上假设金坛市土地生态质量分布具有城乡梯度的规律。通过热点和梯度分析验证表明:（1）土地生态指数热点空间分异特征符合城乡梯度规律,城镇化是导致该规律的重要原因;（2）土地生态指数沿着金坛市“城镇—城乡结合部—近郊—远郊”环形梯度分布,总体上土地生态指数不断升高,沿城镇中心向外每增加2 400 m,土地生态指数提高1.6%;（3）城镇中心土地生态质量状况处于最低值,且城镇所在地土地生态质量比正常状态差,更精细地表明城镇化对土地生态质量的不良影响;区域土地生态结构是影响金坛市土地生态综合指数波动的最大因素。（4）该文对土地生态指数空间分异规律作了深入探究,对土地生态指数空间分异的驱动力分析和主控因子识别将在进一步研究中进行探索。该研究可引导政府在城镇化进程中实施改善土地生态质量的政策。     

An assessment of the olive ridley turtle (Lepidochelys olivacea) nesting population in Orissa, India

Olive ridley mass nesting events or ‘arribadas’ have been documented in Orissa, India since 1974. However, since standardised techniques have not been used to census turtles, actual population trends remain unknown. Herein, we summarise information on nesting populations in Orissa, using data from multiple sources to arrive at consensus estimates and to derive trends. We conducted a quantitative estimate of an arribada in March 1999, where nesting was estimated as ∼180,000 turtles by the strip transect method. Non-linear (quadratic) fits for arribada data from 1976-1999 and a recent decrease in the size of adults suggest a potential or imminent decline, consistent with fishery-related mortality of at least 90,000 turtles since 1994. Though statistical support for the recent decline is equivocal, efforts to reduce mortality and close monitoring of the population would be prudent. The absence of reliable data on which to base conservation action highlights an urgent need to train management personnel in data collection and estimation techniques for effective monitoring of status, threats and trends.     

Effect of surfacing patterns on abundance estimates of long-diving animals

ABSTRACT:   Population sizes of long-diving marine mammals can be estimated with minimal bias using line transect sampling techniques in conjunction with data on surfacing/diving, even though the detection probability on the trackline is considerably less than 1. Using a simulation, it was investigated whether population sizes can be accurately estimated when only the mean cue production rate, without information on surfacing/diving patterns, is available. In addition, a new model that incorporates information on surfacing/diving patterns into the estimation procedure was developed. The simulation showed that the new model can provide less biased abundance estimates, whereas neglecting surfacing/diving patterns can result in serious underestimates of abundance, in particular for long-diving animals.     

青藏铁路唐古拉山南段沿线植被多样性及盖度特征分析

通过以铁路线为样带中心点,对青藏铁路唐古拉山南段沿线垂直于铁路两侧系统设置植被调查样带、样地、样方,重点调查铁路沿线原生植被物种组成、高度、盖度、株丛数等,着重分析了不同样带植被物种丰富度、植被盖度、物种共有度沿纬度方向的空间变化特征,为铁路生态安全体系建设和植被生态修复提供重要参考。结果表明:①1 m×1 m样方平均物种数多在9～12种之间,丰富度相对较低;20 m×20 m样地平均物种17～26种。各样带总的物种丰富度在47～59种之间;植被物种丰富度纬度方向距离差异不明显;样方、样地、样带小尺度的变化对物种丰富度会产生很大影响。②青藏铁路南段总体植被覆盖度高,植被覆盖率80%以上的占1/2强;因受局部环境条件的影响,其植被覆盖度也存在一定差异。③应用Jaccard指数对沿线各植被样带物种共有度进行分析,结果表明,随着样带纬度方向间距的增大,物种共有度指数值呈逐渐减小的趋势,相邻样带的物种共有度最大,物种纬度方向逐渐替代的规律明显。      

Re-introduction of the golden eagle into the Republic of Ireland

The golden eagle (Aquila chrysaetos) became extinct in the Republic of Ireland in about 1912. Historical evidence suggests that, in the early nineteenth century, the population exceeded 50 pairs. It is thought that the extinction was a consequence of persecution and habitat change. Because there seems little chance of natural recolonisation a re-introduction programme has been developed. It is intended to release up to 15 birds per year for 5 years, starting in 2001. Single chicks will be obtained from Scottish nests with twins. The ways in which this project adheres to the six main IUCN re-introduction criteria are addressed. Two simulation models are described. The first, GEPM, demonstrates that the removal of chicks from Scottish nests should not have a detrimental effect on the Scottish population. The second model predicts the probable home range occupancy if only 12 birds are released each year. It is expected that between 3 and 13 ranges will be occupied by 2007. The imprecision in this estimate is a consequence of uncertainty about juvenile survival rates. The rationale behind our reintroduction scheme is outlined to stimulate debate about the development of good practice.     

Assessment of Three Methods for Estimating Abundance of Ungulate Populations

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Soil organic matter and land degradation in semi-arid area,Israel

Soil organic matter (SOM) was monitored at five research sites along a climatic transect extending from the Judean Mountains (mean annual rainfall 700 mm; annual mean temperature 17 °C) to the Dead Sea (mean annual rainfall < 100 mm; annual mean temperature 23 °C) in Israel. At four sites, representing four climatic regions, Mediterranean (site GIV), semi-arid (site MAL), mildly arid (site MIS) and arid (site KAL), four to eight soil samples were taken four times a year, in January, March, May and September, from 1992 through 1993 and 1994 and in April and August 2000. In the last 2 months soil samples were also taken from another site (MAB) in the semi-arid area. Comparison between the sites along the climatic transect shows that, except for site MAB, SOM increased significantly in both 0–2 cm and 2–10 cm, from the arid site, through the mildly arid site and the semi-arid site, to the Mediterranean site. Analysis of SOM temporal patterns of the two semi-arid sites (MAL and MAB) shows significant change from the normal SOM pattern in both the regional scale and the soil profile scale in one site (MAB). The a-normal pattern of SOM and the low soil aggregate stability at MAB indicates land degradation and it is attributed to overgrazing.     

内蒙古额济纳旗繁殖期鸟类群落与生态分布

2016年至2018年的5月和6月,采用样线法和样点法对额济纳旗的鸟类种类、数量和分布进行了多次调查.本项调查中共记录到繁殖期鸟类63种,隶属于18目30科,其中留鸟13种,夏候鸟42种,旅鸟8种.在繁殖鸟类中,古北界的鸟类有37种,占58.7％,鸟类区系具有典型的古北界特征.文中对该地区不同生境鸟类群结构及其之间的关...