ESTIMATES OF THE NUMBERS OF HUMPBACK WHALES OBSERVED MIGRATING PAST CAPE VIDAL, SOUTH AFRICA, 1988–1991

A recovery-monitoring program of the African east coast humpback whale population was carried out through shore-based visual surveys from Cape Vidal, northern Natal. Surveys of the northward migration were undertaken each winter from 1988 to 1991, and a survey of the southward migration was undertaken in 1990. Independent observer surveys were undertaken during June 1990 and during the entire 1991 survey. Hourly densities of groups sighted each day were adjusted for groups missed by observers with distance from the shore and under different sighting conditions. Densities were multiplied by 24 h and the mean group size of the survey year to give resulting daily densities of individuals, which were summed to provide totals of whales sighted during each year's survey. The best estimate of population size was 1,711 (made during the northward migration of 1990), although this is likely to be biased downwards by a proportion of the population passing outside of observers'view. Bootstrapping of the 1991 daily data resulted in CVs between 11.4% and 12.2%. The numbers sighted show the population to have undergone considerable recovery since protection in October 1963.     

CHARACTERIZATION OF BEAKED WHALE (ZIPHIIDAE) AND SPERM WHALE (PHYSETER MACROCEPHALUS) SUMMER HABITAT IN SHELF-EDGE AND DEEPER WATERS OFF THE NORTHEAST U. S.

Sperm whales ( Physeter macrocephalus ) and beaked whales ( Mesoplodon spp. and Ziphius cavirostris ) are deep-diving cetaceans that frequent shelf-edge and Gulf Stream waters off the northeast U. S. coast. Sighting data collected during seven summer (1990, 1991, 1993, and 1995–1998) shipboard surveys were analyzed using a geographic information system to determine habitat use based on bathymetric and oceanographic features. Although sighting rates were lower for beaked whales, both taxa occupied similar habitats. Beaked whales were concentrated at the colder shelf edge, whereas sperm whales were associated with warmer off-shelf water. Mean sighting rates for both taxa were higher in canyon features, but only beaked whale sighting rates were significantly different between canyon and non-canyon habitat (Wilcoxon signed rank test P = 0.007). Within the shared habitat, the two taxa were separated at fine-scale based on oceanographic features.     

Abundance and distribution of harbour porpoisesPhocoena phocoena in selected areas of the western Baltic and the North sea

An aerial survey of harbour porpoises,Phocoena phocoena, was conducted in June–July 1992 in the western Baltic (Bay of Kiel, the Great Belt, Little Belt, an area north of Fyn) and a coastal area in the North Sea off the island of Sylt. Survey procedures and statistical analysis were identical to those of a similar survey in 1991 and survey results from the two years were compared. The highest density of porpoises was found in the North Sea area, whereas the Bay of Kiel and the Little Belt had low densities. The Great Belt and the area north of Fyn had intermediate densities and the area north of Fyn had a density similar to that found in the same area in 1991. The distribution of the perpendicular sighting distance from the surveys in 1991 and 1992 was identical in locality and dispersal, but gave rise to different estimates of effective search widths. Pod sizes for the 1992 survey were smaller than pod sizes estimated from boat surveys, but were within the range of those for the 1991 aerial survey.     

Modelling heterogeneity in detection probabilities in land and aerial abundance surveys in humpback whales (<Emphasis Type="Italic">Megaptera novaeangliae</Emphasis>)

The effective management and conservation of animal populations relies on statistically-sound and replicable surveys to obtain estimates of abundance and assess trends. Surveys of cetaceans, such as humpback whales Megaptera novaeangliae, are difficult to conduct and are particularly affected by bias in detection probability. For example, the probability of detection of whales from land decreases substantially with increased distance from the platform. This distance effect is also true for aerial surveys, combined with the problem that animals are unavailable for detection (underwater) whilst in the field of view. We present a novel approach that combines corrected double-platform land surveys with corrected aerial surveys to obtain a robust estimate of g(0), the probability of detection on the survey line, for aerial surveys of migrating humpback whales. Several sources of heterogeneity in detection probabilities were identified within the land and aerial surveys (including group composition, bearing of first sighting, number of groups being tracked simultaneously and cloud cover). After including these into our estimate of ĝ(0), we found that only 29% of available whales are being detected on the survey line (ĝ(0) = 0.288), which is a considerably smaller estimate than many available for humpback whales using other methods. Incorporating heterogeneity into the population surveys shows that we are likely to be underestimating the population size of whales on the east coast of Australia. The implications of this result for their conservation and management in light of increased whale-human conflict is discussed.     

DETECTION OF SEA OTTERS IN BOAT-BASED SURVEYS OF PRINCE WILLIAM SOUND, ALASKA

Boat-based surveys have been commonly used to monitor sea otter populations, but there has been little quantitative work to evaluate detection biases that may affect these surveys. We used ground-based observers to investigate sea otter detection probabilities in a boat-based survey of Prince William Sound, Alaska. We estimated that 30% of the otters present on surveyed transects were not detected by boat crews. Approximately half (53%) of the undetected otters were missed because the otters left the transects, apparently in response to the approaching boat. Unbiased estimates of detection probabilities will be required for obtaining unbiased population estimates from boat-based surveys of sea otters. Therefore, boat-based surveys should include methods to estimate sea otter detection probabilities under the conditions specific to each survey. Unbiased estimation of detection probabilities with ground-based observers requires either that the ground crews detect all of the otters in observed subunits, or that there are no errors in determining which crews saw each detected otter. Ground-based observer methods may be appropriate in areas where nearly all of the sea otter habitat is potentially visible from ground-based vantage points.     

Aerial census of ringed seals Pusa hispida basking on the ice of the Bothnian Bay, Baltic

The censuses are based on six surveys (1590 km total) carried out between 13 April and 17 May 1975 and two surveys (560 km) on 13 and 15 May 1978. The material consists of 716 observations in 1975 and 214 observations in 1978, involving 1960 and 572 ringed seal specimens respectively. The transect width was determined in retrospect on the basis of the sighting angle and sighting distance, the latter being estimated and corrected by a factor typical for each separate flight. The mean sighting distances varied from 720 to 1140 m with a range from 160 to 2450 m. On average over 3000 ringed seats were basking on the ice of the Bothnian Bay in 1975 and 1978, promising at least 4000 specimens living in the area in total. Sources of methodological bias, factors affecting the observability of the seals, and the estimation of the total population based on the numbers of basking seals are discussed.     

ATOC AND OTHER FACTORS AFFECTING THE DISTRIBUTION AND ABUNDANCE OF HUMPBACK WHALES (MEGAPTERA NOVAEANGLIAE) OFF THE NORTH SHORE OF KAUAI

Humpback whale diving behavior changes subtly when exposed to signals transmitted from the Acoustic Thermometry of Ocean Climate (ATOC) sound projector located 14 km offshore the island of Kauai. This study considered whether such responses would lead to changes in distribution and abundance. A land-based shore station measured humpback whale locations (scan samples) for both nearshore (<5 km) and offshore (5–10 km) areas. Control observations were made in 1994 and 1998. In 1998 multipleday blocks with ATOC transmissions were interspersed with multiple-day control blocks without transmissions. Sighting rates were higher in 1998 (ATOC) than in 1994 (control year), probably due to better sighting conditions, but may reflect increased population size. Sighting rates did not differ between control and ATOC conditions in 1998. A seasonal sighting peak was observed in both years. No vessel effect on sighting rate was detected in 1998.
There was no effect of ATOC on the distance from the shore station to whales, or the depth of water where pods were located. However, the distribution of whales shifted slightly eastward during the ATOC blocks and the mean distance between the ATOC source and pods was greater during transmissions. Nonetheless, more whales were found close to the source when it was on, suggesting a more variable response rather than simple avoidance, with whales found both closer to, and farther away from, the source during transmissions.     

Estimating Detection Probabilities from Sign of Collared Peccary

ABSTRACT Determining presence or absence of collared peccaries (Pecari tajacu) from surveys of sign (tracks and feces) requires information on whether animals in sample units are detected. We estimated detection probabilities of collared peccary from sign surveys using occupancy models. Because it was unlikely that residence status of collared peccary in sampling units remained the same over a survey season, which is a primary assumption of occupancy models, we first determined the time interval for which to pool data. We then examined the influence of rainfall and peccary abundance on detection probabilities. We placed 90 sign stations (25-m-diam circular plots) throughout Chaparral Wildlife Management Area, south Texas, USA. We surveyed plots weekly for the presence or non-presence of collared peccary during 2 11-week sampling seasons in spring and fall 2003. We examined sign data weekly and we pooled the data in intervals from 2 weeks to 5 weeks. Estimates of detection probabilities increased from 1 week to 3 weeks of pooled data and leveled off thereafter. We needed a 3-week time interval to meet the assumption of unchanging residence status. Using sign data pooled in 3-week increments, detection probabilities were influenced by areas that differed in peccary abundance, but they were not influenced by rainfall. Estimates of detection probabilities ranged from 0.43 to 0.77 for 3-week time intervals. Sign surveys and occupancy modeling of data can be used to measure spatial patterns of collared peccary in south Texas as long as multiple 3-week time intervals are sampled.     

Winter distribution of harp seals (Phoca groenlandica) off eastern Newfoundland and southern Labrador

The winter distribution of Newfoundland harp seals (Phoca groenlandica) was determined using sighting data collected during January and February from 1991 to 1995 aboard research vessels that covered the northeastern continental shelf between 46–55°N and 47–54°W. Data were standardized for effort and sighting conditions. Visual appraisals of data were made using a Geographical Information System. In contrast to historical perceptions, offshore areas such as the northern part of the Grand Banks (48–49°N and 49–51°W) appear to be extremely important to wintering harp seals. Southeastern shifts in distribution appear to have occurred since the early 1990s, particularly between the 1991–1993 and 1994–1995 periods. This southern shift in range agrees with the recent increase in extralimital occurrences of harp seals along the North American east coast. Concurrent changes in environmental conditions suggest that physical and biological factors may influence the distribution of this population. Accepted: 22 May 2000     

Estimating sika deer abundance using camera surveys

Cameras have been used throughout the world to estimate wildlife abundance and occupancy. Abundance estimates generated by camera surveys tend to be less invasive, less costly, and more accurate than other means in certain situations. We sought to expand and test the effectiveness of camera surveys on sika deer in Maryland. In 2008, we setup surveys with a 7-day pre-bait period followed by a 7-day active camera survey with 15 cameras. In 2009, we ran the cameras for the entire 14-day survey and moved cameras after each survey to determine if biases occur when using the same camera sites. During both years and all surveys, camera density was approximately 1-camera/65-ha. The abundance estimates were similar between years and estimators. In 2009, increasing photo intervals from 1-min to 5- and 10-min intervals reduced the number of pictures by 66 and 81%, respectively, while providing similar abundance estimates. We calculated the daily detection probabilities for all identifiable deer and we used radio-collared males that occurred within 2 km of the survey grid to assist in determining the optimum survey length. Detection probability did not vary between surveys in the same year, but varied between 2008 and 2009, most likely due to unlimited bait being available during 2008 surveys. Camera surveys have proven to be an accurate and cost effective means of estimating wildlife abundance and can be used successfully to determine sika deer abundance.     

FITNESS CONSEQUENCES OF SEASONAL POLYPHENISM IN WESTERN WHITE BUTTERFLIES

The western white butterfly, Pontia occidentalis, has distinctly different wing phenotypes during spring and summer generations as a result of phenotypic plasticity (seasonal polyphenism). We experimentally generated different seasonal phenotypes in the lab by altering photoperiodic conditions during rearing, and released the resulting butterflies in the field. Mark-recapture studies were then used to estimate the effects of the polyphenism on activity patterns and adult survival in both late-spring (one study) and summer (two studies) conditions. There were no significant effects of rearing treatment on temporal patterns of behavioral activity during either the late-spring or the summer field studies. Recapture probabilities were consistently higher for males than females in all three field studies; in the summer 1992 study, recapture probabilities were higher for long-day (LD) than for short-day (SD) treatment groups. During the late-spring 1992 study, there were no significant differences between LD and SD treatment groups for survival probabilities. In the two summer studies, there were significant effects of photoperiodic treatment on survival probabilities; in the summer 1992 study, LD individuals consistently had higher survival probabilities than SD individuals; in the summer 1991 study, there was a significant interaction between treatment and time period on survival probabilities, such that survival probabilities were higher for LD than for SD individuals in two of four time periods. The consistent differences in survival probabilities between treatment groups in the summer 1992 study can be accounted for by the differences in wing traits between the treatment groups. Micrometeorological data from the study site showed that midday ambient temperatures averaged ~3°C hotter during the 1992 than the 1991 summer study and that ambient conditions during the late-spring 1992 study were relatively warm and sunny for the season. These results document the varying relationships between phenotype and fitness in the temporally fluctuating environments experienced by this population.     

长江口水域鱼卵、仔稚鱼种类组成和数量的分布与变化

根据2005年4和11月、2006年4和9月在长江河口水域进行的鱼卵、仔稚鱼种类和数量调查,并结合1990年9月和1991年3月的历史数据,对该水域的鱼卵、仔稚鱼群落结构的种类组成和数量的季节变化作了研究,其结果共发现鱼卵、仔稚鱼36种(类),以海洋鱼类种类最多。秋季航次鱼卵、仔稚鱼的平均种类数和丰度均高于春季。河口咸淡水区鱼卵总数显著高于淡水区,而仔稚鱼总数略低于淡水区。与1990—1991年数据相比,2005—2006年春、秋季的鱼卵和仔稚鱼丰度均有所增加。1990、2006年秋季(9月)鱼卵、仔稚鱼种类组成差异较大,特别是翘嘴红鲌和太湖新银鱼丰度差异较大。这些都说明近20年来,长江河口水域鱼卵、仔稚鱼种类组成和数量均发生了明显的改变。     

SPATIOTEMPORAL PREDICTION MODELS OF CETACEAN HABITATS IN THE MID-WESTERN NORTH ATLANTIC OCEAN (FROM CAPE HATTERAS, NORTH CAROLINA, U.S.A. TO NOVA SCOTIA, CANADA)

Habitat prediction models were developed for 13 cetacean species of the mid-western North Atlantic Ocean: beaked whale, fin whale, humpback whale, minke whale, pilot whale, sperm whale, bottlenose dolphin, common dolphin, Risso's dolphin, spotted dolphin, whitesided dolphin, and harbor porpoise. Using the multiple logistic regression, sightings of cetaceans during the 1990–1996 summer (June-September) surveys were modeled with oceanographic (sea surface temperature, monthly probability of front occurrence) and topographic (depth, slope) variables for the same period. Predicted habitat maps for June and August were created for each species using a Geographical Information System. The predicted habitat locations matched with current and historic cetacean sighting locations. The model also predicted habitat shifts for some species associated with oceanographic changes. The correct classification rate of the prediction models with 1997–1998 summer survey data ranged from 44% to 70%, of which most of the misclassifications were caused by false positives ( i.e. , absence of sightings at locations where the models predicted).     

普氏原羚生境选择的数量化分析

1998 年8 月至1999 年8 月, 在湖东种羊场地区开展了普氏原羚生境选择的研究。在湖东—克图沙丘和草原交界处沿约30 km的样线开展种群调查, 在调查过程中, 共发现582 只普氏原羚。在研究中选择了8 类与普氏原羚生境选择相关的生态因子: 植被类型、食物丰富度、草原围栏、隐蔽条件、人为干扰、距公路距离、距沙丘距离和距农业用地距离, 研究了普氏原羚的生境选择。在研究中, 将这些生态因子分别分成3 个等级, 进行回归分析, 建立普氏原羚在不同生境中出现的概率的预测性方。通过对生态因子和普氏原羚在不同生境中出现的概率进行方差分析, 判断影响普氏原羚生境选择的主要生态因子是人为干扰和围栏, 其次为食物丰富度、距沙丘距离和农业用地距离, 植被类型、隐蔽条件和与公路距离对普氏原羚生境选择的影响不明显。     

Co-Occurrence and Habitat Use of Fin Whales,Striped Dolphins and Atlantic Bluefin Tuna in the Northwestern Mediterranean Sea

Different dolphin and tuna species have frequently been reported to aggregate in areas of high frontal activity, sometimes developing close multi-species associations to increase feeding success. Aerial surveys are a common tool to monitor the density and abundance of marine mammals, and have recently become a focus in the search for methods to provide fisheries-independent abundance indicators for tuna stock assessment. In this study, we present first density estimates corrected for availability bias of fin whales (Balaenoptera physalus) and striped dolphins (Stenella coeruleoalba) from the Golf of Lions (GoL), compared with uncorrected estimates of Atlantic bluefin tuna (ABFT; Thunnus thynnus) densities from 8 years of line transect aerial surveys. The raw sighting data were further used to analyze patterns of spatial co-occurrence and density of these three top marine predators in this important feeding ground in the Northwestern Mediterranean Sea. These patterns were investigated regarding known species-specific feeding preferences and environmental characteristics (i. e. mesoscale activity) of the survey zone. ABFT was by far the most abundant species during the surveys in terms of schools and individuals, followed by striped dolphins and fin whales. However, when accounted for availability bias, schools of dolphins and fin whales were of equal density. Direct interactions of the species appeared to be the exception, but results indicate that densities, presence and core sighting locations of striped dolphins and ABFT were correlated. Core sighting areas of these species were located close to an area of high mesoscale activity (oceanic fronts and eddies). Fin whales did not show such a correlation. The results further highlight the feasibility to coordinate research efforts to explore the behaviour and abundance of the investigated species, as demanded by the Marine Strategy Framework Directive (MSFD).     

Optimizing surveys for marsh songbirds: does timing matter?

Analysis of data from point counts, a common method for monitoring bird population trends, has evolved to produce estimates of various population parameters (e.g., density, abundance, and occupancy) while simultaneously estimating detection probability. An important consideration when designing studies using point counts is to maximize detection probability while minimizing variation in detection probability both within and between counts. Our objectives were to estimate detection probabilities for three marsh songbirds, including Marsh Wrens (Cistothorus palustris), Swamp Sparrows (Melospiza georgiana), and Yellow‐headed Blackbirds (Xanthocephalus xanthocephalus), as a function of weather covariates and to evaluate temporal variability in detection probability of these three species. We conducted paired, unlimited radius, 10‐min point counts during consecutive morning and evening survey periods for our three focal species at 56 wetlands in Iowa from 20 April to 10 July 2010. Mean detection probabilities ranged from 0.272 (SE = 0.042) for Marsh Wrens to 0.365 (SE = 0.052) for Swamp Sparrows. Time of season was positively correlated with detection probability for Swamp Sparrows, but was negatively correlated with detection probability for Yellow‐headed Blackbirds, suggesting that detection probability increased during the breeding season for Swamp Sparrows and was highest early in the breeding season for Yellow‐headed Blackbirds. Understanding how detection probabilities of marsh songbirds vary throughout the breeding season allows targeted survey efforts that maximize detection probabilities for these species. Furthermore, consistent detection probabilities of marsh songbirds during morning and evening survey periods mean that investigators have more time to conduct surveys for these birds, allowing greater flexibility to increase spatial and temporal replication of surveys that could provide more precise estimates of desired population parameters.     

Encounter Rates From Road-Based Surveys of Rio Grande Wild Turkeys in Texas

ABSTRACT Traditional index-based techniques have indicated declines in Rio Grande wild turkey (Meleagris gallopavo intermedia; hereafter, wild turkey) populations across much of Texas, USA. However, population indices can be unreliable. Research has indicated that road-based surveys may be an efficacious technique for monitoring wild turkey populations on an ecoregion level. Therefore, our goal was to evaluate applicability of road-based distance sampling in the Cross Timbers, Edwards Plateau, Rolling Plains, and South Texas ecoregions of Texas. We conducted road-based surveys in each ecoregion during December 2007—March 2008 to estimate wild turkey flock encounter rates and to determine survey effort (i.e., km of roads) required to obtain adequate sample sizes for distance sampling in each ecoregion. With simulations using inflatable turkey decoys, we also evaluated effects of distance to a flock, flock size, and vegetative cover on turkey flock detectability. Encounter rates of wild turkey flocks from road-based surveys varied from 0.1 (95% CI = 0.0–0.6) to 2.2 (95% CI = 0.8–6.0) flocks/100 km surveyed. Encounter rates from surveys restricted to riparian communities (i.e., areas ≤1 km from a river or stream) varied from 0.2 (95% CI = 0.1–0.6) to 2.9 (95% CI = 1.5–6.7) flocks/100 km surveyed. Flock detection probabilities from field simulations ranged from 22.5% (95% CI = 16.3–29.8%) to 25.0% (95% CI = 13.6–39.6%). Flock detection probabilities were lower than expected in all 4 ecoregions, which resulted in low encounter rates. Estimated survey effort required to obtain adequate sample sizes for distance sampling ranged from 2,765 km (95% CI = 2,597–2,956 km) in the Edwards Plateau to 37,153 km (95% CI = 12,861–107,329 km) in South Texas. When we restricted road-based surveys to riparian communities, estimated survey effort ranged from 2,222 km (95% CI = 2,092–2,370 km) in the Edwards Plateau to 22,222 km (95% CI = 19,782–25,349 km) in South Texas.     

A sampling design and model for estimating abundance of Nile crocodiles while accounting for heterogeneity of detectability of multiple observers

As part of the development of a management program for Nile crocodiles in Lake Nasser, Egypt, we used a dependent double-observer sampling protocol with multiple observers to compute estimates of population size. To analyze the data, we developed a hierarchical model that allowed us to assess variation in detection probabilities among observers and survey dates, as well as account for variation in crocodile abundance among sites and habitats. We conducted surveys from July 2008–June 2009 in 15 areas of Lake Nasser that were representative of 3 main habitat categories. During these surveys, we sampled 1,086 km of lake shore wherein we detected 386 crocodiles. Analysis of the data revealed significant variability in both inter- and intra-observer detection probabilities. Our raw encounter rate was 0.355 crocodiles/km. When we accounted for observer effects and habitat, we estimated a surface population abundance of 2,581 (2,239–2,987, 95% credible intervals) crocodiles in Lake Nasser. Our results underscore the importance of well-trained, experienced monitoring personnel in order to decrease heterogeneity in intra-observer detection probability and to better detect changes in the population based on survey indices. This study will assist the Egyptian government establish a monitoring program as an integral part of future crocodile harvest activities in Lake Nasser. © 2012 The Wildlife Society.     

中国野生动物调查存在的问题与改进建议

一百余年前,人类就开始了相对系统的野生动物调查。目前已经建立了成熟的方法体系,并制定了相应的调查规范。最近几十年来,我国科研人员进行了大量的野生动物调查。但是,当前我国的野外调查规范还不够细致,调查者在调查时缺乏必要的约束,导致调查数据不规范、不可靠,很多重要信息缺失。突出问题有：样线信息不全,只有起点和终点的经纬度,没有自动记录的详细样线信息（如每秒记录一次的连续点位信息,含经纬度和时间）;动物位点信息缺乏可信度指标（如距观测者的距离）;调查时间不合理;调查地点的空间取样不均衡;记录的标准化不够（如每个观测点的观测时长不确定）等等。对此,我们参考国际通用的调查规范,提出了一些简单易行的调查要点,以便提高野外调查数据的质量。另外,我们提倡野外记录的无纸化,充分利用现有的手机应用软件（APP）和模型工具提高野外记录以及后期数据处理的效率。最后,我们提议建立固定的中国生物多样性监测样线体系,以便消除每年调查时空间取样的不确定性,更好地量化野生动物的时间动态,为野生动物的保护和管理提供依据。     

ABUNDANCE OF SOUTHERN CALIFORNIA COASTAL BOTTLENOSE DOLPHINS ESTIMATED FROM TANDEM AERIAL SURVEYS

We describe a tandem aerial survey method for bottlenose dolphins ( Tursiops truncatus ) that uses two aircraft and independent observer teams to conduct consecutive surveys of the same coastal strip one hour apart. Alternatively, one aircraft with one observer team surveys the same coastal strip twice over several hours. Using mark-recapture analysis, we corrected survey counts for visibility bias resulting from missing dolphin groups at the surface and submerged groups. Dolphin groups were considered "recaptured" when we determined that both observer teams had detected the same group. This tandem method is highly useful for estimating abundance (and visibility bias) for species where population closure may be assumed between flights. We assumed population closure between flights and matched groups using geographic location, group size, and expected travel rates. We derive a new variance estimator of population size which incorporates group-size variability commonly encounteted in cetacean surveys. From six tandem surveys conducted from 1991 to 1994, we estimated the abundance of southern California coastal bottlenose dolphins to be between 78 (95% CI 60-102) and 271 (240-306) animals, with an average of 140 (128-154). Variability in abundance estimates is likely due to seasonal and interannual movement of animals along the California and Baja California coast. Abundance estimates from tandem surveys averaged 53% higher than dolphin counts obtained from individual survey flights, demonstrating the importance of correcting for visibility bias.