Home About us Contact
|
Home About us Contact | ||
|
|
||
Sightings Data (sighting + data)
Selected AbstractsCHARACTERIZATION OF BEAKED WHALE (ZIPHIIDAE) AND SPERM WHALE (PHYSETER MACROCEPHALUS) SUMMER HABITAT IN SHELF-EDGE AND DEEPER WATERS OFF THE NORTHEAST U. S.MARINE MAMMAL SCIENCE, Issue 4 2001G. T. Waring Abstract 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. [source] Characterizing Core and Corridor Use by Nubian Ibex in the Negev Desert, IsraelCONSERVATION BIOLOGY, Issue 1 2000Yehoshua Shkedy To identify and characterize corridors used by Nubian ibex (Capra ibex nubiana), we analyzed sighting data recorded for the past 20 years in the Israel Nature Reserves Authority data banks. We categorized each recorded sighting as belonging to a corridor or a core zone based on the total number of sightings in its vicinity. We identified three main core populations, a natural corridor connecting two of them, and a corridor that was not evident connecting the third population. Ibex inside and outside core zones were sighted on steeper terrain than expected by chance; this was more pronounced inside the core zones than outside them. We hypothesize that because ibex outside core zones must move rapidly and directionally across unfamiliar habitats, they must use more moderate terrain. Although ibex sightings in core zones were mostly in the vicinity of water, we found no relationship between the location of the sightings and proximity to water sources in the corridor. Hence, water does not appear to be an important factor in movement through corridors. It was more common to observe ibex out of the core zones during the summer. Males, which can be twice the size of females, were found traveling alone in corridors more often than in core zones. There was no difference between males and females in the steepness of terrain in which they were sighted outside core zones. Our data show that protecting ibex habitat in core zones and corridors is important to ibex conservation in Israel's arid zones. In addition, protecting this habitat may benefit other rock-dwelling species in the area. Resumen: Los corredores son un factor clave en esfuerzos de conservación. Para identificar y caracterizar el uso de corredores por el íbice de Nubia (Capra ibex nubiana) analizamos datos de avistamiento de los últimos 20 años en las bases de datos de la Autoridad Israelí de Reservas Naturales. Categorizamos cada registro asignándolo a un corredor o a una zona núcleo basándonos en el total de registros cercanos. Identificamos tres poblaciones en zona núcleo, un corredor natural que conectaba a dos de ellas y un corredor, no muy evidente, conectando a la tercera población. Se registraron íbices en terrenos inclinados dentro y fuera de zonas núcleo más de lo esperado al azar; esto fue más marcado dentro de las zonas núcleo que afuera. Hipotetizamos que deben utilizar terrenos más moderados, debido a que los íbices fuera de las zonas núcleo deben moverse rápida y direccionalmente a través de hábitats no familiares. Aunque los registros de íbices en zonas núcleo estuvieron cercanos a agua, no encontramos relación entre la localización de los registros y la cercanía a fuentes de agua en el corredor. Por tanto, el agua no parece ser un factor importante en el movimiento en los corredores. Fue más común observar íbices afuera de las zonas núcleo en el verano. Los machos, que pueden ser dos veces más grandes que hembras, fueron registrados desplazándose solos en los corredores más a menudo que en las zonas núcleo. No hubo diferencia entre machos y hembras en la pendiente del terreno en que fueron registrados fuera de las zonas núcleo. Nuestros resultados indican que la protección del hábitat de íbices en zonas núcleo y corredores es importante para la conservación de íbices en las zonas áridas de Israel. Además, la protección de este hábitat puede beneficiar a otras especies en el área. [source] Habitat selection of freshwater-dependent cetaceans and the potential effects of declining freshwater flows and sea-level rise in waterways of the Sundarbans mangrove forest, BangladeshAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2009B.D. Smith Abstract 1.Generalized additive models of sighting data for cetaceans collected during two surveys of waterways in the Sundarbans mangrove forest of Bangladesh indicated that Ganges River dolphin Platanista gangetica gangetica distribution was conditionally dependent (P<0.05) on low salinity, high turbidity, and moderate depth during both low and high freshwater flow; and Irrawaddy dolphin Orcaella brevirostris distribution was conditionally dependent (P<0.05) on low salinity during high freshwater flow, high and moderate depths during low and high freshwater flow, respectively; low and high-low extremes of turbidity during low and high freshwater flow, respectively; and high temperature and increasing numbers of large,small channel confluences during low freshwater flow. 2.According to sighting data collected over a 3-year period by the captains of three nature tourism vessels, there were significant differences between the actual and expected frequencies of Ganges River dolphin sightings and individuals according to various channel types (chi-square=64.22, P<0.0001 and chi-square=134.14, P<0.0001, respectively, df=6) and of Irrawaddy dolphin sightings and individuals (chi-square=15.28, P=0.0182, and chi-square=29.42, P<0.0001, respectively, df=6), with shared preferences for wide sinuous channels with at least two small confluences or one large confluence. 3.The dependency exhibited by both species for environmental characteristics associated with abundant freshwater flow, including low salinity and the availability of confluences, make them particularly vulnerable to habitat loss due to upstream water abstraction and sea-level rise. 4.Although the results of this study may not affect plans for construction in India of large-scale, inter-basin water transfer projects that will result in further declines in freshwater flows, or decisions within the international community about CO2 emissions affecting global sea levels, they can be used to prioritize locations where protective measures could be employed to benefit the long-term conservation of both species. Copyright © 2008 John Wiley & Sons, Ltd. [source] Distribution of minke whales in the Bellingshausen and Amundsen Seas (60°W,120°W), with special reference to environmental/physiographic variablesFISHERIES OCEANOGRAPHY, Issue 3 2000Fujio Kasamatsu The relationship between the distribution of minke whales (Balaenoptera acutorostrata) in the Bellingshausen and Amundsen Seas (longitude between 60°W and 120°W), and environmental and physiographic variables (sea-surface temperature, sea-ice extension, and sea-floor-slope type), was studied to determine whether these environmental and physical factors affect the distribution and density of minke whales. The analysis was based on sightings data obtained from the 1989/90 and 1982/83 IWC/IDCR cruises. The mean sea-surface temperatures for comparable areas were significantly higher in 1989/90 (2.04°C) than in 1982/83 (1.12°C), and the area where the sea-surface temperature was greater than 1°C in the 1989/90 study was approximately twice that of the 1982/83 study. Additionally, during the surveys, the extent of the sea ice in 1989/90 was less than that in 1982/83, with the mean ice edge about 92.6 km (50 nautical miles; 1 nautical mile ,1.852 km) farther south in 1989/90 than in 1982/83. This is consistent with the sea ice extent observed in winter, when the sea ice extent was less in 1989 than in 1982. The distribution of minke whales was substantially different between the two surveys, with the density and abundance of minke whales being greater in 1982/83 than in 1989/90. The warmer sea-surface temperatures, fewer cold-water intrusions, and the smaller extent of sea ice in 1989/90 may be related to the difference in distribution of minke whales from 1982/83, possibly owing to the shift in availability of prey. [source] Estimating deer abundance from line transect surveys of dung: sika deer in southern ScotlandJOURNAL OF APPLIED ECOLOGY, Issue 2 2001Fernanda F.C. Marques Summary 1Accurate and precise estimates of abundance are required for the development of management regimes for deer populations. In woodland areas, indirect dung count methods, such as the clearance plot and standing crop methods, are currently the preferred procedures to estimate deer abundance. The use of line transect methodology is likely to provide a cost-effective alternative to these methods. 2We outline a methodology based on line transect surveys of deer dung that can be used to obtain deer abundance estimates by geographical block and habitat type. Variance estimation procedures are also described. 3As an example, we applied the method to estimate sika deer Cervus nippon abundance in south Scotland. Estimates of deer defecation and length of time to dung decay were used to convert pellet group density to deer density by geographical block and habitat type. The results obtained agreed with knowledge from cull and sightings data, and the precision of the estimates was generally high. 4Relatively high sika deer densities observed in moorland areas up to 300 m from the forest edge indicated the need to encompass those areas in future surveys to avoid an underestimate of deer abundance in the region of interest. 5It is unlikely that a single method for estimating deer abundance will prove to be better under all circumstances. Direct comparisons between methods are required to evaluate thoroughly the relative merits of each of them. 6Line transect surveys of dung are becoming a widely used tool to aid management and conservation of a wide range of species. The survey methodology we outline is readily adaptable to other vertebrates that are amenable to dung survey methodology. [source] Double-Observer Line Transect Methods: Levels of IndependenceBIOMETRICS, Issue 1 2010Stephen T. Buckland Summary Double-observer line transect methods are becoming increasingly widespread, especially for the estimation of marine mammal abundance from aerial and shipboard surveys when detection of animals on the line is uncertain. The resulting data supplement conventional distance sampling data with two-sample mark,recapture data. Like conventional mark,recapture data, these have inherent problems for estimating abundance in the presence of heterogeneity. Unlike conventional mark,recapture methods, line transect methods use knowledge of the distribution of a covariate, which affects detection probability (namely, distance from the transect line) in inference. This knowledge can be used to diagnose unmodeled heterogeneity in the mark,recapture component of the data. By modeling the covariance in detection probabilities with distance, we show how the estimation problem can be formulated in terms of different levels of independence. At one extreme, full independence is assumed, as in the Petersen estimator (which does not use distance data); at the other extreme, independence only occurs in the limit as detection probability tends to one. Between the two extremes, there is a range of models, including those currently in common use, which have intermediate levels of independence. We show how this framework can be used to provide more reliable analysis of double-observer line transect data. We test the methods by simulation, and by analysis of a dataset for which true abundance is known. We illustrate the approach through analysis of minke whale sightings data from the North Sea and adjacent waters. [source] | ||||||||||