Genetic relationships of American alligator populations distributed across different ecological and geographic scales

Although much work has been conducted on coastal populations of the American alligator (Alligator mississippiensis), less is known about the population dynamics and genetic structure of populations of alligators confined to inland habitats. DNA microsatellite loci, derived from the American alligator, were used to investigate patterns of genetic variation within and between populations of alligators distributed at coastal and inland localities in Texas. These data were used to evaluate the genetic discreteness of different alligator stocks relative to their basic ecology at these sites. Observed mean heterozygosities across seven loci for both coastal and inland populations ranged from 0.50-0.61, with both inland and coastal populations revealing similar patterns of variation. Measures of F(st) revealed significant population differentiation among all populations; however, analyses of molecular variance (AMOVAs) failed to demonstrate any apparent geographic pattern relative to the population differentiation indicated by F(st) values. Each population contained unique alleles for at least one locus. Additionally, assignment tests based on the distribution of genotypes placed 76% of individuals to their source population. These genetic data suggest considerable subdivision among alligator populations, possibly influenced by demographic and life history differences as well as barriers to dispersal. These results have clear implications for management. Rather than managing alligators in Texas as a single panmictic population, translocation programs and harvest quotas should consider the ecological and genetic distinctiveness of local alligator populations.     

Nest success and hatchling survival of American alligators within inland wetlands of east Texas

Because of liberalization of American alligator (Alligator mississippiensis) harvest management in Texas, estimates of nest success and hatchling survival for inland populations are essential for long-term, sustainable population and harvest management. To date, few studies have examined American alligator nest success and hatchling survival. We initiated a 3-year study from 2006 to 2008 to document alligator nest success and hatchling survival within several wetlands in east Texas. From June 2006 to August 2008, we located 30 nests from 3 wetlands within east Texas, where overall nest success was 44.2% (95% CI = 25.1–63.1%), irrespective of year. Nest circumference and day during the nesting season exerted the greatest influence on nest success. Additionally, from August 2006 to August 2008 we captured, marked, and released 271 hatchling alligators at Little Sandy National Wildlife Refuge, and recaptured an additional 192 hatchling alligators during this time. We estimated yearly apparent survival at 6.0% (95% CI = 2.0–14.6%) for hatchling alligators born in 2006 and 43.0% (95% CI = 28.4–57.8%) for those hatched in 2007. Variation in nest success and hatchling survival was likely attributed to fluctuating water levels and habitat management practices. Alligator harvest regulations need to account for variability in nest success and hatchling survival by including site-specific estimates of these metrics into harvest models. Failing to account for spatial and temporal variation in nest success and hatchling survival may result in unsustainable harvest and/or overharvest. © 2012 The Wildlife Society.     

Habitat requirements of weasels <Emphasis Type="Italic">Mustela nivalis</Emphasis> constrain their impact on prey populations in complex ecosystems of the temperate zone

Differences in habitat use by prey and predator may lead to a shift of occupied niches and affect dynamics of their populations. The weasel Mustela nivalis specializes in hunting rodents, therefore habitat preferences of this predator may have important consequences for the population dynamics of its prey. We investigated habitat selection by weasels in the Bia?owie?a Forest in different seasons at the landscape and local scales, and evaluated possible consequences for the population dynamics of their prey. At the landscape scale, weasels preferred open habitats (both dry and wet) and avoided forest. In open areas they selected habitats with higher prey abundance, except during the low-density phase of the vole cycle, when the distribution of these predators was more uniform. Also in winter, the distribution of weasels at the landscape scale was proportional to available resources. In summer, within open dry and wet habitats, weasels preferred areas characterised by dense vegetation, but avoided poor plant cover. In winter, weasels used wet open areas proportionally to availability of habitats when hunting, but in contrast to summer, they rested only in habitats characterized by a lower water level, which offered better thermal conditions. At the local scale, the abundance of voles was a less important factor affecting the distribution of these predators. Although we were not able to provide direct evidence for the existence of refuges for voles, our results show that they may be located within habitat patches, where availability of dense plant cover and physiological constraints limit the activity of weasels. Our results indicate that in complex ecosystems of the temperate zone, characterized by a mosaic pattern of vegetation types and habitat specific dynamics of rodents, impact of weasels on prey populations might be limited.     

南陵县扬子鳄的种群数量及栖息地质量

1986-1998年,在安徽省南陵县对扬子鳄种群资源及分布区栖息地状况进行了4次调查。1999年对该县扬子鳄部分栖息地的质量做了研究。结果显示,南陵县扬子鳄野生种群目前只30头左右,每4年平均递减率约38%,分布于6个镇,7个行政村中,75%的栖息地已经消失,其中东河、三里、石铺三镇生活有全县80%的扬子鳄,而石铺镇扬子鳄密度最大,引起扬子鳄种群数量下降的主要原因是栖息地破坏,同时对鳄的捕杀,污染、天灾也是重要因素,其野外栖息地主要为两种类型,农耕区普通池塘和丘陵山地的山塘、水库,耕作区食物,栖息条件较好,人鳄矛盾较小的局部水域依然是扬子鳄最佳选择,但这类水域农药化肥污染已构成对扬子鳄的潜在威胁。     

Evaluation of Effects of Harvest on Alligator Populations in Louisiana

Biologists with the Louisiana Department of Wildlife and Fisheries, Louisiana, USA, have managed statewide annual harvest of alligators (Alligator mississippiensis) for 35 years (1981–present). We collected and analyzed harvest data for Louisiana alligators to determine the effects of harvest on the population structure, focusing on the larger size classes (≥274 cm) of this slow-growing species. Linear regression analyses revealed that body size-class structure, based on overall average size and the percentage of animals harvested in the larger size classes was relatively stable. Annual aerial alligator nest counts indicated a continual growth of the population, and over time harvested alligators maintained a constant average size. Analyses of population size (based on number of nests and population modeling) indicated that the current annual harvest represents approximately 3% of the population. Linear regression analysis showed that annual hunter success declined only slightly during the study period, and the scheduling of the hunt season after the hatch period and recommended hunting in areas not frequented by breeding females provides economic opportunities for hunters to participate in a sustainable harvest that preserves the larger size classes of alligators in the population. Strict enforcement of existing laws was a key factor responsible for the success of this harvest program. Comparison of alligator population size and number of harvest-related citations indicated that illegal harvest did not have a negative effect on population size, and linear regression analyses revealed that the rate of increase in citations was lower than the increase in populations over the study period. The results of this harvest program indicated that alligators can be hunted in a sustainable manner if hunting is conducted after the hatch period and occurs in areas that primarily exclude the harvest of adult females, and strict law enforcement curbs illegal activities that negatively affect populations. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.     

Variation in the quality and quantity of flavonoids in the leaves of coastal and inland Campanula punctata

Ultraviolet-B radiation is known as a noxious factor that destroys every life form. Plants that occupy the coastal area are assumed to be adaptive to UV-B as well as the other major stresses. The objective of this study was to clarify and compare (1) the flavonoid compositions of coastal and inland populations of Campanula punctata, and (2) UV-B effects on flavonoid content in plants originating from different habitats under uniform (i.e. experimental) and natural conditions. Flavonoid compositions of coastal and inland populations were shown to be identical. The UV-B exclusion experiment revealed two tendencies that were commonly observed in both coastal and inland populations: (1) the flavonoid accumulation decreased with an increase in degree of UV-B exclusion, and (2) the quantity of phenolic acids conversely became maximum under complete UV-B exclusion. Under the natural habitat conditions, significantly high accumulation of flavonoids were detected in two coastal populations even though no significant difference was found between the two other coastal populations and two inland populations. Weak correlations between UV-B intensity and flavonoid accumulation under the natural habitat conditions suggest that various micro-environmental factors may influence the production of flavonoids, and that the plants may acquire adaptive traits other than increasing flavonoids in order to inhabit the coastal environment.     

Isolation of faecal coliform bacteria from the American alligator (Alligator mississippiensis)

Aims: To determine whether American alligators (Alligator mississippiensis) are an unrecognized poikilothermic source of faecal coliform and/or potential pathogenic bacteria in South Carolina’s coastal waters. Methods and Results: Bacteria from the cloaca of American alligators, as well as bacteria from surface water samples from their aquatic habitat, were isolated and identified. The predominant enteric bacteria identified from alligator samples using biochemical tests included Aeromonas hydrophila, Citrobacter braakii, Edwardsiella tarda, Escherichia coli, Enterobacter cloacae, Plesiomonas shigelloides and putative Salmonella, and these were similar to bacteria isolated from the surface waters in which the alligators inhabited. Based on most‐probable‐number enumeration estimates from captive alligator faeces, faecal coliform bacteria numbered 8·0 × 10⁹ g^?1 (wet weight) of alligator faecal material, a much higher concentration than many other documented endothermic animal sources. Conclusions: A prevalence of enteric bacteria, both faecal coliforms and potential pathogens, was observed in American alligators. The high faecal coliform bacterial density of alligator faeces may suggest that alligators are a potential source of bacterial contamination in South Carolina coastal waters. Significance and Impact of the Study: These findings help to increase our understanding of faecal coliform and potential pathogenic bacteria from poikilothermic reptilian sources, as there is the potential for these sources to raise bacterial water quality levels above regulatory thresholds.     

我国扬子鳄种群及栖息地保护现状

扬子鳄(Alligator sinensis)是我国特有的古老而珍稀的爬行动物,现阶段野生扬子鳄的分布区域进一步萎缩,成为彼此孤立的点状,残存栖息地的生态环境趋于恶化,野生鳄数量估计为120～150条,老年化程度高。扬子鳄的保护管理依据现实状况及时加以调整,加大了野外保护力度,逐步改善野生鳄的栖息生境,实施野外放归工程,初步遏制了野生鳄数量迅速下滑的局面。人工饲养种群数量已逾10 000条,当前人工饲养繁殖的重点是管理好有限的遗传多样性资源。扬子鳄的研究主要涉及形态学、解剖学、组织胚胎学、生态学、生理生化、细胞及分子生物学,人工饲养繁殖技术等方面。营养生理和保护遗传学的应用研究有待加强。     

野生扬子鳄种群动态变化及致危因素

1998—2003年,采用问卷调查、走访居民、夜间灯光照射计数等方法,对可能有野生扬子鳄(Alligator sinensis)分布的安徽省、浙江省和江苏省的45个地点进行了调查。结果发现：目前野生扬子鳄呈点状分布在至少23个地点,个体总数约120条,主要集中分布在安徽扬子鳄国家级自然保护区内。通过连续调查和对比分析表明：自20世纪50年代扬子鳄数量急剧下降(从5000—6000条下降为120条),但1998年至今其数量保持相对稳定(120条),种群的致危因素主要是栖息地破坏、人为捕杀、环境污染、自然灾害、繁殖力低等。在不同时期导致数量下降的因素不同：1950—1990年问,主要是由于栖息地丧失、人为捕杀等;目前的主要致危因素是缺乏适宜的自然栖息地,环境污染和遗传多样性丧失是潜在的致危因素。旱灾对野生扬子鳄生存的影响并不明显。     

SHOREBIRD HABITAT USE AND NEST-SITE SELECTION IN THE PLAYA LAKES REGION

Abstract: Wetlands in the Playa Lakes Region (PLR) provide important habitats for wintering waterfowl, cranes, and both migrant and breeding shorebirds. Playa Lakes Region wetlands experience naturally fluctuating hydroperiods but are exposed to anthropogenic stresses, which are exacerbated during summer and may influence PLR wetland occupancy and selection by breeding shorebirds. We examined wetland-scale habitat use and nest-site selection of the 4 dominant shorebirds (American avocets [Recurvirostra americana], black-necked stilts [Himantopus mexicanus], killdeer [Charadrius vociferus], snowy plovers [C. alexandrinus]) nesting in playas, saline lakes, and in both created and riparian wetlands in the PLR of Texas, USA. All 4 species nested in saline lakes. Only avocets and killdeer nested in playas, and snowy plovers nested in riparian wetlands. No nests were found in created wetlands. Wetland habitat changed (P < 0.001) during the breeding season, while water habitats generally decreased. Used (i.e., shorebirds found nesting) wetlands had more (P < 0.05) mudflats than non-used (i.e., shorebirds not found nesting) wetlands, which had more (P < 0.05) dry habitats. Used and non-used wetlands had similar (P > 0.05) amounts of water habitats. Nests were located close to vegetation on bare dry ground and dry ground with vegetation. Because water is ephemeral in PLR wetlands, shorebirds must select—in a somewhat predictive manner upon arrival—wetlands with suitable nest-site and brood-rearing habitat. Although surface water is necessary for nesting, its presence is not adequate for delineating suitable PLR wetland habitat for breeding shorebirds. Our findings that created wetlands cannot compensate for regional wetland losses in habitat or function highlights the need for conservation of natural PLR wetlands     

The Origin of Winter Visitors to the British Isles 7. Fieldfare (Turdus pilaris)

Capsule Large‐scale intensification of agricultural management during the past 50 years has resulted in a reduction of invertebrate abundance and higher and denser ground vegetation. Food availability for insectivorous birds foraging on the ground has been negatively affected, but the interactions between birds and their food availability are complex and often species‐specific. Populations of Wrynecks Jynx torquilla are declining all over Europe, possibly because of reduced accessibility to their main prey, ground‐dwelling ants, due to higher and denser ground vegetation. However, it is not clear which ground vegetation structures are tolerated by foraging Wrynecks and which habitats are preferred.

Aims To identify the optimal ground vegetation structure and the main habitat types in which Wrynecks search for food.

Method We radiotracked seven Wrynecks in high‐intensity farmland in Switzerland to study foraging habitat use during the reproduction season. Several habitat variables were mapped at each foraging location and compared with locations selected randomly within individual home ranges.

Results Wrynecks preferentially foraged at places with ≥50% bare ground. Vegetation height was not important. Older fruit tree plantations and fallow land were the preferred foraging habitats.

Conclusion Conservation measures should concentrate on preserving semi‐open agricultural landscape matrices with loose ground vegetation cover to provide suitable foraging conditions. This can be achieved even in intensively managed farmland as illustrated in this study.     

Characteristics of American alligator bites on people in Florida

Human–American alligator (Alligator mississippiensis) conflict in Florida, USA, has increased since the early 1970s, along with the recovery of the American alligator population. To better understand factors contributing to the risk of people being bitten by free-ranging alligators in Florida, we evaluated the trend of alligator bites during 1971–2014 and examined characteristics associated with bites on people documented during 1948–2014. We classified 372 bites as either unprovoked or unintentionally provoked and used these in further analyses. Major injuries to victims occurred in 247 bite incidents. The estimated annual number of bites resulting in major injury to the victim increased from 3.5 to 7.0 during 1971–2014. The number of bites per Florida resident did not show a significant trend during 1971–2014. No significant change occurred in the frequency of fatal attacks during 1971–2014. Monthly frequency of bites was positively correlated with both mean maximum and mean minimum air temperatures but was not significantly correlated with testosterone concentration in adult male alligators, suggesting that bites are more likely related to feeding rates associated with seasonal fluctuations in ambient temperature than to aggression by male alligators during the breeding season. A high percentage of bites (41.8%) occurred in unnamed water bodies, which were generally small or man-made. Most (93.7%) victims were Florida residents, and 58.7% resided close to the incident site. Victims were predominantly male (81.4%), and adults were more frequently victims than were adolescents or children. Most victims (93.9%) were in the water or near the shore when bitten. Victims were more likely to sustain major injuries if the bite occurred in deeper water. Male alligators were more frequently (76.9%) responsible for bites. We found only 1 instance in which a bite was associated with defense of eggs or young by an adult female alligator. Evidence of people feeding alligators before the bite was documented in 34.7% of bite incidents. Twenty-two fatalities were attributed to alligator attacks, but we could not discern a pattern in the ages of victims. Alligators responsible for severe or fatal bites were predominantly in good condition with few deformities or injuries. Most alligator bites in Florida appeared to be attempts at feeding, although 36.8% of incidents entailed a single bite followed by immediate release, suggesting that alligators were unsure about their prey or were biting in defense. The risk of alligator bites can be reduced by educating people likely to interact with alligators and by selectively removing problem alligators in human residential areas and water bodies used regularly by people for swimming, wading, and shoreline activities. © 2019 The Wildlife Society.     

Changes in distribution of waterbirds following prolonged drought reflect habitat availability in coastal and inland regions

Provision of suitable habitat for waterbirds is a major challenge for environmental managers in arid and semiarid regions with high spatial and temporal variability in rainfall. It is understood in broad terms that to survive waterbirds must move according to phases of wet–dry cycles, with coastal habitats providing drought refugia and inland wetlands used during the wet phase. However, both inland and coastal wetlands are subject to major anthropogenic pressures, and the various species of waterbird may have particular habitat requirements and respond individualistically to spatiotemporal variations in resource distribution. A better understanding of the relationships between occurrence of waterbirds and habitat condition under changing climatic conditions and anthropogenic pressures will help clarify patterns of habitat use and the targeting of investments in conservation. We provide the first predictive models of habitat availability between wet and dry phases for six widely distributed waterbird species at a large spatial scale. We first test the broad hypothesis that waterbirds are largely confined to coastal regions during a dry phase. We then examine the contrasting results among the six species, which support other hypotheses erected on the basis of their ecological characteristics. There were large increases in area of suitable habitat in inland regions in the wet year compared with the dry year for all species, ranging from 4.14% for Australian White Ibis to 31.73% for Eurasian Coot. With over half of the suitable habitat for three of the six species was located in coastal zones during drought, our study highlights the need to identify and conserve coastal drought refuges. Monitoring of changes in extent and condition of wetlands, combined with distribution modeling of waterbirds, will help support improvements in the conservation and management of waterbirds into the future.     

黄河流域出土龙山时期扬子鳄骨板的多种同位素分析

扬子鳄现今生活在长江下游地区,但是在龙山时代(5000～4000 BP cal.)黄河流域多处遗址中发现了扬子鳄骨板。为判断龙山时代华北地区的扬子鳄是本地生长还是来自与长江流域的贸易交换,本研究对芮城清凉寺、邹平丁公、泗水尹家城3处遗址出土的7例鳄鱼骨板进行了Sr、C和O同位素分析。3处遗址鳄鱼骨板的⁸⁷Sr/⁸⁶Sr值均落入当地Sr同位素背景范围内,且山东样本的δ¹⁸O比值高于山西样本,符合δ¹⁸O值由内陆向沿海升高的趋势,证明这些扬子鳄个体属于本地物种的可能性很大。扬子鳄骨板的δ¹³C值都明显高于世界其他内陆地区淡水系统的鳄鱼,显示出复杂的饮食特征。上述结果有助于深入了解不同时期扬子鳄的地理分布变迁,对重建距今四千多年前华北地区的古环境具有重要意义,同时也对龙山先民与扬子鳄的关系提出了新的疑问。     

Streptanthus bracteatus (Brassicaceae), a rare annual woodland forb, thrives in less cover: evidence of a vanished habitat?

One of the challenges of understanding habitat requirements of endangered species is that the remaining populations may not be in optimal habitat, requiring experimentation to determine optimal habitat and to guide management. A better knowledge of its habitat requirements is important for the conservation of Streptanthus bracteatus, a rare annual of central Texas woodlands. The habitat requirements of a rare, declining species like S. bracteatus can also provide insights into anthropogenic habitat degradation and into previous disturbance regimes. We conducted a garden experiment and a transplant experiment to determine the effect of different light environments on the growth and reproduction of S. bracteatus. Higher levels of light improved S. bracteatus performance, especially fecundity. The optimum level of combined canopy and understory cover at the height of a S. bracteatus plant (??0.5?m above ground) was less than 50?%. The remaining populations of S. bracteatus are in sub-optimal habitat because it is not open enough. The results are consistent with the hypothesis that this species was a ??fire-follower.?? The results also support the hypotheses that central Texas woodlands were once more open and that fire played an ecological role in these woodlands, an example of the ecological requirements of a rare species revealing past community structure and dynamics.     

Influence of Juniper on Montezuma Quail Habitat Use in Texas

Montezuma quail (Cyrtonyx montezumae) inhabit oak (Quercus spp.)-juniper (Juniperus spp.) woodlands throughout Mexico and the southwestern United States. In Texas, USA, Montezuma quail occur in the Edwards Plateau and Trans-Pecos Mountains and Basins (Trans-Pecos), 2 ecoregions with contrasting juniper patterns. Ashe juniper (Juniperus ashei) dominates in the Edwards Plateau and has been increasing over decades, whereas alligator juniper (Juniperus deppeana) is a co-dominant in the Trans-Pecos and appears to have stable Montezuma quail populations. Our objectives were to compare between ecoregions the relative abundance and habitat use of Montezuma quail in relation to juniper and quantify the influence of juniper on key features of Montezuma quail habitat (grass height, grass cover, forb cover, and forb species richness). We conducted a study from March–August 2018‒2020 in the Edwards Plateau (Kinney and Edwards counties) and Trans-Pecos ecoregions (Jeff Davis County) to evaluate these objectives. We conducted call-back surveys to estimate relative abundance (number of detections/hr) of Montezuma quail and identify used locations. We collected vegetation data at a micro-scale (16-m) at used (n = 32–30 points) and random locations (n = 70–60 points) in each ecoregion. Relative abundance of Montezuma quail was considerably lower in the Edwards Plateau (0.06 ± 0.01 detections/survey hr; ± SE) than in the Trans-Pecos (1.10 ± 0.30 detections/survey hr). In addition, Montezuma quail selected areas of low Ashe juniper cover (<23% cover), density (<7 trees/80 m²), and height (<2 m) in the Edwards Plateau but selected areas of high alligator juniper cover (>18% cover), density (>4 trees/80 m²), and height (2–8 m) in the Trans-Pecos. Moreover, Ashe juniper cover had a significant, negative influence on herbaceous features, whereas alligator juniper exerted little to no influence. Our results suggest that these 2 juniper species have contrasting effects on Montezuma quail space use and their habitat, possibly as a result of the contrasting influence of these junipers on herbaceous understory. Creating habitat for Montezuma quail in the Edwards Plateau generally will involve the reduction of Ashe juniper and creating patches that possess juniper trees of small stature (<2 m) with low amounts of cover (<23%) and density (<7 trees/80 m²), whereas management in the Trans-Pecos will require site-specific assessments based on current alligator juniper influence. © 2021 The Wildlife Society.     

How to deal with ground truthing affected by human‐induced habitat change?: Identifying high‐quality habitats for the Critically Endangered Red Siskin

Species distribution models (SDM) can be valuable for identifying key habitats for conservation management of threatened taxa, but anthropogenic habitat change can undermine SDM accuracy. We used data for the Red Siskin (Spinus cucullatus), a critically endangered bird and ground truthing to examine anthropogenic habitat change as a source of SDM inaccuracy. We aimed to estimate: (1) the Red Siskin's historic distribution in Venezuela; (2) the portion of this historic distribution lost to vegetation degradation; and (3) the location of key habitats or areas with both, a high probability of historic occurrence and a low probability of vegetation degradation. We ground‐truthed 191 locations and used expert opinion as well as landscape characteristics to classify species' habitat suitability as excellent, good, acceptable, or poor. We fit a Random Forest model (RF) and Enhanced Vegetation Index (EVI) time series to evaluate the accuracy and precision of the expert categorization of habitat suitability. We estimated the probability of historic occurrence by fitting a MaxLike model using 88 presence records (1960–2013) and data on forest cover and aridity index. Of the entire study area, 23% (20,696 km²) had a historic probability of Red Siskin occurrence over 0.743. Furthermore, 85% of ground‐truthed locations had substantial reductions in mean EVI, resulting in key habitats totaling just 976 km², in small blocks in the western and central regions. Decline in Area of Occupancy over 15 years was between 40% and 95%, corresponding to an extinction risk category between Vulnerable and Critically Endangered. Relating key habitats with other landscape features revealed significant risks and opportunities for proposed conservation interventions, including the fact that ongoing vegetation degradation could limit the establishment of reintroduced populations in eastern areas, while the conservation of remaining key habitats on private lands could be improved with biodiversity‐friendly agri‐ and silviculture programs.     

Multi-scale habitat selection affects offspring survival in a precocial species

In theory, habitat preferences should be adaptive. Accordingly, fitness is often assumed to be greater in preferred habitats; however, this assumption is rarely tested and, when it is, the results are often equivocal. Habitat preferences may not directly convey fitness advantages if animals are constrained by tradeoffs with other selective pressures like predation or food availability. We address unresolved questions about the survival consequences of habitat choices made during brood-rearing in a precocial species with exclusive maternal care (mallard Anas platyrhynchos, n = 582 radio-marked females on 27 sites over 8 years). We directly linked duckling survival with habitat selection patterns at two spatial scales using logistic regression and model selection techniques. At the landscape scale (55–80 km²), females that demonstrated stronger selection of areas with more cover type 4 wetlands and greater total cover type 3 wetland area (wetlands with large expanses of open water surrounded by either a narrow or wide peripheral band of vegetation, respectively) had lower duckling survival rates than did females that demonstrated weaker selection of these habitats. At finer scales (0.32–7.16 km²), females selected brood-rearing areas with a greater proportion of wetland habitat with no consequences for duckling survival. However, females that avoided woody perennial habitats composed of trees and shrubs fledged more ducklings. The relationship between habitat selection and survival depended on both spatial scale and habitats considered. Females did not consistently select brood-rearing habitats that conferred the greatest benefits, an unexpected finding, although one that has also been reported in other recent studies of breeding birds.     

Microhabitat mosaics are key to the survival of an endangered ground beetle (<Emphasis Type="Italic">Carabus nitens</Emphasis>) in its post-industrial refugia

Biota dependant on early seral stages or frequently disturbed habitats belong to the most rapidly declining components of European biodiversity. This is also the case for Carabus nitens, which is threatened across Western and Central Europe. We studied one of the last remaining populations of this ground beetle in the Czech Republic, which inhabits post-extraction peat bogs. In line with findings from previous studies, we show that C. nitens prefers patches characterized by higher light intensity and lower vegetation cover. Abundance of females was positively correlated with the cover of plant species requiring higher temperature. In addition, we demonstrate its preference for periodically moist, but not wet or inundated plots, suggesting that the transition between dry heathland and wet peat bog might be the optimal habitat for this species. This hypothesis is further supported by results showing a positive correlation between the abundance of C. nitens and vegetation cover comprising of a mix of species typical for heathland, peat bog, and boreal habitats. Our results show that C. nitens mobility is comparable to other large wingless carabids. The maximum covered distance was ~?500 m in a month. To ensure the survival of this population, sites of recent peat extraction should be spared from reclamation and afforestation. In contrast, active measures should be taken to facilitate nutrient removal, disturbance of vegetation cover, and the creation of depressions with a humid microclimate. These actions will create a mosaic of heath, bog, and bare ground, which seems to be the preferred habitat of C. nitens at our study site.     

野生扬子鳄种群及栖息地现状研究

1999年7～8月及2000年8～9月,利用GPS、激光测距仪等,采用夜间灯光照射计数方法,对 有野生扬子鳄(Alligator sinensis)存在的安徽省宣州、泾县、广德、郎溪、南陵等5 县市的26个地点进行了调查,包括扬子鳄国家级自然保护区的13个指定保护点。结果发现： 目前野生扬子鳄主要生存在第一类栖息地（1999年50.7%、2000年40.0%）,面积为17.38 hm²;其他两类栖息地的野生扬子鳄分布比率较小（各为1999年24.0%、2000年30.9%、1999 年25.3% 、2000年29.1%）,面积分别为22.04hm²、19.03hm²。两年的平均生态密度分别为1.28条/hm²和1.79条/hm²,野生扬子鳄种群数量为145条。其种群已明显分为至少18个数 量不等且相互隔离的地方种群。建议恢复足够大的栖息地,并放饲养鳄于其中以重新 建立有效野生种群。