Scaling Occupancy Estimates up to Abundance for Wolves

Management of wildlife populations often requires reliable estimates of population size or distribution. Estimating abundance can be logistically difficult, and occupancy models have been used as a less expensive proxy for abundance estimation. Another alternative is to use independent estimates of home-range size and mean group size to directly scale occupancy estimates up to abundance. We used simulations to explore when scaling occupancy up to abundance is reliable, and as an example we applied an occupancy approach to estimate abundance of wolves (Canis lupus) from roadside snow-tracking surveys in northern Wisconsin, USA, in 2016 and 2018. Estimates of wolf abundance were plausible and compared favorably with independent estimates produced by territory mapping, and snow-tracking data requirements were lower than for territory mapping. Simulation results suggested that reasonable abundance estimates could be obtained under some conditions but also that severe positive bias could result under other conditions, especially when populations were small and dispersed, home range size was small, and areal sampling units were large. Positive bias in abundance estimates occurs because of closure assumption violations when tracks from a single wolf or pack are detected in >1 sample unit, and the sum of the sample unit areas where tracks were detected exceed the sum of the home range areas. Bias was minimized when sampling units were small relative to home range size or when sampling units were route segments that approximate point sample units, and when home ranges were highly aggregated. We conclude that, although caution is warranted when scaling occupancy estimates up to abundance, scaled occupancy models can provide feasible and reliable estimates of abundance, assuming home range size and mean group size are accurately known or estimated, sampling units are appropriately chosen, and covariates that aggregate home ranges can be used to accurately predict occupancy probability. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.     

Effects of habitat-conditioning by the damselfish Stegastes nigricans (Lacepède) on the community structure of benthic algae

We compared the community structure of benthic algae inside and outside pomacentrid damselfish (Stegastes nigricans) territories in a moat at Sesoko Island, Okinawa, Japan. S. nigricans maintained “algae farms” that were dominated by the filamentous rhodophyte, Womersleyella setacea. Species richness and biomass were higher inside damselfish territories than outside, while species diversity and evenness were higher outside. Detrended correspondence analysis (DCA) based on species composition showed that the dominance of W. setacea was maintained throughout the year in all samples collected from inside damselfish territories. The observed strong dominance of filamentous rhodophytes was consistent with the findings of most studies on damselfish territories worldwide. However, the dominance of a single species of alga and low species diversity inside the territories was in contrast to the findings of previous studies, in which the reduction of grazing pressure caused intermediate disturbance and enhanced algal species diversity. This discrepancy in algal species diversity inside the damselfish territories seems to have been caused by unique characteristics of the alga and the fish. W. setacea traps sediment, which reduces the availability of firm substrata for attachment and inhibits the recruitment of some algae. Moreover, S. nigricans “weeds” indigestible calcareous and thicker algae. The algal assemblage outside damselfish territories varied among samples, and included mat-forming cyanophytes (Calothrix aeruginosa and Calothrix codicola), a prostrate laminar phaeophyte (Padina sp.), thin and small-scaled algae (Cladophora sp. and Feldmannia indica), finely branched filamentous rhodophytes (Taenioma perpusillum and Herposiphonia obscura), and a coarsely branched rhodophyte (Gelidiopsis variabilis).

We placed artificial slate plates inside and outside damselfish territories, and showed that the W. setacea inside territories gradually increased in biomass, reaching the same levels of biomass and dominance as W. setacea on natural substrata. Outside the territories, the algal assemblage underwent succession from early colonizers, i.e., thin and small-scaled algae, to grazing-resistant algae such as mat-forming cyanophytes and prostrate laminar Padina sp. Under heavy grazing, the flora outside the territories was composed of early colonizers, grazing-resistant algae, and scattered erect algae that had probably escaped grazing by chance.

Our findings suggest that sediment trapped by the turf of W. setacea inhibited recruitment of some algae, and that moderate cropping and selective weeding by S. nigricans excluded grazing-resistant algae and prevented early colonizers and competitively superior algae from out-competing W. setacea. Consequently, low species diversity and a high-biomass “farm” suitable for harvesting was maintained.     

Spatial distribution and habitats of useful plants: an initial assessment for conservation on an indigenous territory, Panama

In order to examine the spatial distribution of forest resources on local territories and to understand the factors controlling such distributions, we studied the spatial patterns of a group of 23 useful plant species on the territory of a Kuna community in the province of Darien, Panama. A stratified random sampling scheme was used to survey the distribution and abundance of the species across a 3500 ha area around the village. Data on the physical environment as well as the geographic coordinates of the sample plots were also obtained. A series of canonical analyses was conducted to evaluate the species–environment relationships and to identify spatial structures in the species distributions left unexplained by the environmental variables. Four distinct distribution patterns were identified among the species; these were most strongly explained by land-use, the degree of canopy closure and topography. Significant spatial structures, independent of the measured environmental variables, were related to anthropogenic pressure and an edaphic gradient, and the habitat associations of the individual species were described. The results obtained from this case study suggest that land-use dynamics may play a predominant role in structuring inhabited landscapes, and that diversity in distribution patterns and habitat associations will require a combination of spatially explicit management strategies to ensure the local resource base.     

论中国自然保护区的面积上限

中国从195 6年开始建设自然保护区,其间经过了一个较长的停滞时期之后,到2 0 0 2年底,中国建立了15 5 1个自然保护区,面积达14 14 86 6 km2 ,占国土面积14 .7%。中国自然保护区面积占国土面积的比例已经在2 0 0 2年末超过世界先进水平,然而,目前中国自然保护区的数量仍在增长。由于目前中国的自然保护区是严格意义的保护区,于是,作者提出应区分严格保护的自然保护区与广义的自然保护地,发展一个由不同保护目的、不同保护程度、合理布局的自然保护区组成的综合自然保护区体系,结合经济发展水平建设自然保护区的思想。估算了现阶段自然保护区的基本建设投入与管护费用,探讨了建设和管理2 0 0 2年末中国自然保护区的资金需求。还提出研究中国自然保护区中人口、中国国土面积及分类和中国各种类型土地的适宜保护面积,探讨“在中国多大的国土面积可以建设为自然保护区?”这一命题,从保存生物物种、生物资源、主要生态系统、可持续利用方面研究中国自然保护地的面积上限。     

灰胸薮鹛繁殖行为初报

2009年春季在四川省屏山县老君山自然保护区对灰胸薮鹛Liocichla omeiensis繁殖行为进行了观察.灰胸薮鹛胆小畏人,喜藏匿于茂密灌丛中活动、鸣叫.4月中旬进入繁殖期后雄鸟占区鸣唱逐渐增加,5月中旬占区鸣唱达到高峰,5月下旬逐渐减少,进入育雏期.在山顶茂密方竹丛中找到1巢,对其进行了2个全天观察,雌、雄鸟共同喂雏,亲鸟均会暖雏,但雄鸟暖雏较雌鸟少.亲鸟吃掉幼鸟粪便及食物残渣,以保持巢的清洁.亲鸟喂给幼鸟食物以昆虫和小型蛾类为主,在巢期为15天.     

Overlapping territory of the benthophagous cichlid fish, Lobochilotes labiatus, in Lake Tanganyika

Synopsis Feeding territories do not usually overlap in the same fish species. We studied overlapping territories and feeding behaviours of a benthophagous cichlid fish Lobochilotes labiatus Boulenger in a coastal area of Lake Tanganyika. Forty-four individuals of both sexes, 6–31 cm in total length, maintained territories in a 21 m × 25 m area. These could be regarded as feeding territories. The territories of similar-sized owners (usually different by less than 5 cm) did not overlap each other, but those of different-sized owners overlapped widely. Aggressive interactions were rarely observed between fish distinctly different in body size. Both large and small fish took benthic animals of the same kinds and of similar size. In contrast, the size of foraging sites (crevices) was different between them: the large fish foraged at large crevices and small fish at small crevices. This partitioning of foraging sites may enable the overlap of territories in this benthivore.     

基于卫星定位跟踪数据解读白头鹤的性别、年龄、繁殖及领域回归

2014—2021年,在中国东北、长江中下游以及蒙古国和俄罗斯,通过救助和野外捕捉共计为33只白头鹤(Grus monacha)安装了卫星定位跟踪器,同时佩戴了金属环和彩色塑料环。根据卫星定位信息,找到繁殖巢后,在其周边布设红外照相机。利用卫星跟踪6年以上的6只白头鹤个体以及在小兴安岭北部度夏、繁殖的7只白头鹤个体的定位跟踪数据,将5月15日零时位点为基准点,利用设置的位移-时间计算公式将定位坐标转为位移-时间曲线,使获得的定位数据图形化,结合野外行为观察,获得判别指标：繁殖地或度夏地夜间位移-时间曲线的平直度,反映了白头鹤夜栖点的位置变化;根据曲线平直度判断：曲线平直的是雌性,曲线呈锯齿状的是雄性;距离繁殖区较近、曲线变化幅度非常大的是亚成体,在繁殖区域、曲线近乎平直达1个月左右的是成鸟;根据平直曲线长度,确认是否繁殖成功及初始繁殖年龄;4月初至6月末期间的不同跟踪个体的位移-时间曲线重合的,可以认定为配对关系;重合部分的长短,则反映出配对关系的稳定性;巢址的位移-时间曲线间距,反映出巢址的变化。不同年份的巢址间距离,可以展示白头鹤具有很规则的领域回归行为。依据这些指标对跟踪的全部3...     

Die Bedeutung der Habitatstrukturen als Regulationsmechanismus für die Brutpaardichte von Rabenkr?hen (Corvus c. corone)

Zusammenfassung Von Januar bis September 1996 wurden in vier Gebieten Niedersachsens mit einer Gesamtfläche von 113 km² Untersuchungen zur Bedeutung des Brutplatzangebotes für die Ausbildung unterschiedlicher Siedlungsdichten der Rabenkrähen (Corvus c. corone) durchgeführt. Ziele waren eine Bestandserfassung der Rabenkrähen sowie eine Beurteilung der Habitatstruktur als Regulationsmechanismus für ihre Verteilung und Siedlungsdichte. Die meisten Horste fanden sich in Baumreihen oder Alleen, in gebäudeumgebenden Gehölzen und auf den Stahlmasten von Hochspannungsleitungen. Waldränder wurden als Brutstandort nicht bevorzugt. Der mittlere Nestabstand aller Gebiete betrug 689 m, Reviergrößen schwankten zwischen 0,18 und 0,6 km². Die Nisthöhen lagen zwischen 2,5 und 42 m; in Gehölzen dominierte eine Höhe von 13 m. Die Abundanzen schwankten zwischen 0,5 und 2,0 Paaren/km² bei einer mittleren Abundanz von 1,4 Paaren/km² und einer Gesamtzahl von 72 Nichtbrüterindividuen. Die Habitatstrukturen ermöglichten hypothetisch 3,2- bis 7,6fach höhere Brutpaardichten als real vorkamen. Nur 20% der Strukturen wurden als Nistplatz genutzt. Eine Abhängigkeit der Horstverteilung von der Verteilung der Habitatstrukturen wurde nicht gefunden. Weder die Habitatstrukturen an sich noch in Verbindung mit den Reviergrößen sind als ultimativer Regulationsmechanismus für die Revier- und Brutplatzwahl und damit für die Verteilung und Siedlungsdichte der Rabenkrähen anzusehen.

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Significance of habitat structures as a regulatory mechanism for the breeding density of Carrion Crows (Corvus corone corone)

Summary In four regions of Lower Saxony with a total area of 113 km² we examined woods and electricity pylons as habitat structures with respect to their frequency distribution and suitability as breeding places of carrion crows. We determined real population densities and calculated a hypothetical breeding density in relation to habitat structures in order to test a possible regulative effect of these structures on regional differences in settlement density ofCorvus c. corone. The regional capacities indicated a hypothetical breeding density 3.2 to 7.6 times higher than was proven in reality. Even in a medium-sized territory of 0.5 km² (a value to be found in literature) a 1.4 times higher density is still possible. Furthermore, the regional nest distribution established by the index of dispersion was random, but the habitat structures showed clumping. Neither the habitat structures on their own nor in combination with territory size can be regarded as definite mechanisms of regulation in the choice of territory and breeding place and thence of the distribution and settlement density ofCorvus c. corone. The possible influence of food supply and non-breeding populations on distribution patterns and settlement densities is discussed.

Gefördert mit Jagdforschungsmitteln des Landes Niedersachsen