Bayesian sequential monitoring of density estimates

2021 ◽  
Author(s):  
Wright Shamp ◽  
Antonio Linero ◽  
Eric Chicken
Keyword(s):  
Density Estimates

scholarly journals Evaluating Alternative Flight Plans in Thermal Drone Wildlife Surveys—Simulation Study

2021 ◽  
Vol 13 (6) ◽  
pp. 1102
Author(s):  
Julia Witczuk ◽  
Stanisław Pagacz
Keyword(s):  
Computer Simulations ◽  
Survey Design ◽  
Distance Sampling ◽  
Line Of Sight ◽  
Density Estimates ◽  
Accuracy And Precision ◽  
Survey Costs ◽  
Random Survey ◽  
Density Population

The rapidly developing technology of unmanned aerial vehicles (drones) extends to the availability of aerial surveys for wildlife research and management. However, regulations limiting drone operations to visual line of sight (VLOS) seriously affect the design of surveys, as flight paths must be concentrated within small sampling blocks. Such a design is inferior to spatially unrestricted randomized designs available if operations beyond visual line of sight (BVLOS) are allowed. We used computer simulations to assess whether the VLOS rule affects the accuracy and precision of wildlife density estimates derived from drone collected data. We tested two alternative flight plans (VLOS vs. BVLOS) in simulated surveys of low-, medium- and high-density populations of a hypothetical ungulate species with three levels of effort (one to three repetitions). The population density was estimated using the ratio estimate and distance sampling method. The observed differences in the accuracy and precision of estimates from the VLOS and BVLOS surveys were relatively small and negligible. Only in the case of the low-density population (2 ind./100 ha) surveyed once was the VLOS design inferior to BVLOS, delivering biased and less precise estimates. These results show that while the VLOS regulations complicate survey logistics and interfere with random survey design, the quality of derived estimates does not have to be compromised. We advise testing alternative survey variants with the aid of computer simulations to achieve reliable estimates while minimizing survey costs.

scholarly journals Foraging range and habitat use by Cape Vulture Gyps coprotheres from the Msikaba colony, Eastern Cape province, South Africa

Koedoe ◽  
2015 ◽  
Vol 57 (1) ◽  
Author(s):  
Morgan B. Pfeiffer ◽  
Jan A. Venter ◽  
Colleen T. Downs
Keyword(s):  
South Africa ◽  
Protected Areas ◽  
Breeding Season ◽  
Movement Ecology ◽  
Kernel Density ◽  
Eastern Cape Province ◽  
Eastern Cape ◽  
Convex Polygons ◽  
Density Estimates ◽  
Kernel Density Estimates

Despite the extent of subsistence farmland in Africa, little is known about endangered species that persist within them. The Cape Vulture (Gyps coprotheres) is regionally endangered in southern Africa and at least 20% of the population breeds in the subsistence farmland area previously known as the Transkei in the Eastern Cape province of South Africa. To understand their movement ecology, adult Cape Vultures (n = 9) were captured and fitted with global positioning system/global system for mobile transmitters. Minimum convex polygons (MCPs),and 99% and 50% kernel density estimates (KDEs) were calculated for the breeding and non breeding seasons of the Cape Vulture. Land use maps were constructed for each 99% KDE and vulture locations were overlaid. During the non-breeding season, ranges were slightly larger(mean [± SE] MCP = 16 887 km2 ± 366 km2) than the breeding season (MCP = 14 707 km2 ± 2155 km2). Breeding and non-breeding season MCPs overlapped by a total of 92%. Kernel density estimates showed seasonal variability. During the breeding season, Cape Vultures used subsistence farmland, natural woodland and protected areas more than expected. In the non-breeding season, vultures used natural woodland and subsistence farmland more than expected, and protected areas less than expected. In both seasons, human-altered landscapes were used less, except for subsistence farmland.Conservation implications: These results highlight the importance of subsistence farm land to the survival of the Cape Vulture. Efforts should be made to minimise potential threats to vultures in the core areas outlined, through outreach programmes and mitigation measures.The conservation buffer of 40 km around Cape Vulture breeding colonies should be increased to 50 km.

scholarly journals Assessing Satellite-derived Inter-annually Varying Snow/Firn Density Estimates Over the Greenland Ice Sheet during 2003-2009

2020 ◽  
Author(s):  
Xiaoli Su ◽  
C. K. Shum ◽  
Kenneth C. Jezek ◽  
Jun-Yi Guo ◽  
Ian M. Howat ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Density Estimates

Density Estimates of Harbour Porpoises Phocoena Phocoena at Eight Coastal Sites in Ireland

2014 ◽  
Vol 114B (1) ◽  
pp. 19-34
Author(s):  
Simon Berrow ◽  
Ronan Hickey ◽  
Ian O'Connor ◽  
David McGrath
Keyword(s):  
Phocoena Phocoena ◽  
Density Estimates

Evolution and Feedback Effects of High-z Star-Forming Galaxies

2015 ◽  
Vol 11 (A29B) ◽  
pp. 228-228
Author(s):  
Masami Ouchi
Keyword(s):  
Structure Formation ◽  
Gravitational Lensing ◽  
Formation Rate ◽  
Feedback Effect ◽  
Density Estimates ◽  
Feedback Effects ◽  
Planck Data ◽  
Star Forming ◽  
Deep Imaging ◽  
Open Question

AbstractI review the recent observational progresses of star-forming galaxies at a redshift up to z~10. Inconjunction with gravitational lensing magnifications, deep HST observations obtain first density estimates of UV continuum radiation given by young massive stars, and reveal that the star-formation rate density (SFRD)continuously decreases from z~2-3 to z~10. This SFRD decrease towards high-z should be explained by thecombination of the cosmic structure formation and radiative cooling+feedback effects in a halo. To decouple thecontribution of the cosmic structure formation from the SFRD decrease, the stellar-to-halo mass ratios (SHMR) ofhigh-z galaxies are derived by intensive clustering analyses with HST and Subaru survey data. The SHMR-halo massrelation shows a clear evolution from z~0 to 6, suggesting that the cooling and feedback effects are different betweenthe present and early epochs of the cosmic history. By deep imaging and spectroscopic observations, feedbacksignatures are found in 10-100 kpc-scale outflow of ionized oxgen gas identified around star-forming galaxies with andwithout an AGN heating. There are similarly-large hydrogen Lyα halos and blobs associated with high-z star-forminggalaxies, but the physical origin of these Lyα halos and blobs is an open question. At z≳6, UV radiation of ionizingphotons produced by star-forming galaxies contribute to the cosmic reionization, while it is thought that the UVradiation prevent formation of next generation stars in dwarf galaxies at the early cosmic epoch, which works as acosmological feedback effect. I discuss this reionizations cosmological feedback effect with the up-to-date resultsfrom the HST and Planck data.

Aerial Surveys of Sea Turtles in the Northern Great Barrier-Reef Marine Park

1989 ◽  
Vol 16 (3) ◽  
pp. 239 ◽  
Author(s):  
H Marsh ◽  
WK Saalfeld
Keyword(s):  
Great Barrier Reef ◽  
Sea Turtles ◽  
Analysis Of Covariance ◽  
Seagrass Beds ◽  
Barrier Reef ◽  
Sea State ◽  
Water Turbidity ◽  
Density Estimates ◽  
Marine Park ◽  
Specific Correction

In 1984 and 1985, during surveys designed primarily to census dugongs, six species of sea turtles were counted from the air at an overall sampling intensity of 9% over a total area of 31 288 km2 within the northern sections of the Great Barrier Reef Marine Park. The sea turtles were not identified to species. We attempted to correct sightings for perception bias (the proportion of animals visible in the transect which are missed by observers), and to standardise for availability bias (the.proportion of animals that are invisible due to water turbidity) with survey-specific correction factors. The resultant minimum population estimate in November 1985 was (mean � s.e.) 32 187 � 2532 sea turtles at an overall density of 1.03 � 0.08 km-2, a precision of 8%. We consider this to be a gross underestimate of numbers present. Significant differences between population and density estimates obtained from repeat surveys of the same areas were accounted for by differences in Beaufort sea state and cloud cover. The analysis of covariance data suggested that we had not been successful in standardising all biases. Turtles were widely distributed throughout the Great Barrier Reef lagoon from inshore seagrass beds to mid- and outer-shelf reefs. Highest densities were observed on inshore seagrass beds and on mid-shelf reefs, particularly between Murdoch Island and Cape Melville, and in Princess Charlotte Bay. Maps of density and distribution are given. We discuss the value and limitations of this survey regime for censusing sea turtles.

Density and activity patterns of ocelot populations in Yasuní National Park, Ecuador

Mammalia ◽  
2016 ◽  
Vol 80 (4) ◽  
Author(s):  
Julia Salvador ◽  
Santiago Espinosa
Keyword(s):  
Population Density ◽  
Habitat Loss ◽  
National Park ◽  
Conservation Status ◽  
Activity Patterns ◽  
Camera Trap ◽  
Oil Extraction ◽  
Density Estimates ◽  
Yasuni National Park ◽  
Ecuadorian Amazon

AbstractOcelots were historically hunted for their skins but habitat loss is now their most serious threat, causing rapid declines in populations throughout their range. Ocelot abundance has been estimated for various locations across the Neotropics, but we still lack this information from some countries, including Ecuador. Knowing whether ocelot abundance is increasing or decreasing is important to assess the conservation status of this species and the conditions of its habitats in the Ecuadorian Amazon and in the region. To determine whether ocelot abundance and its behavior are affected by human-related activities, camera-trap surveys were carried out in two localities of Yasuní National Park (YNP), one that has experienced hunting, oil extraction, and roads (Maxus Road) and one that is largely unaffected by these activities (Lorocachi). During the survey, 35 and 36 individual ocelots were photographed in Maxus Road and Lorocachi, respectively. Population density estimates were similar for both localities, ranging from 0.31 (SE±6) to 0.85 (SE±17) ocelots/km

DENSITY ESTIMATES AND DAILY MORTALITY RATE EVALUATIONS OF STABLE FLY (STOMOXYS CALCITRANS (DIPTERA: MUSCIDAE)) POPULATIONS IN FIELD CAGES

1975 ◽  
Vol 107 (6) ◽  
pp. 597-600 ◽  
Author(s):  
G. C. LaBrecque ◽  
Donald L. Bailey ◽  
D. W. Meifert ◽  
D. E. Weidhaas
Keyword(s):  
Mortality Rate ◽  
Sampling Technique ◽  
Late Summer ◽  
Stomoxys Calcitrans ◽  
Stable Fly ◽  
Daily Mortality ◽  
Density Estimates ◽  
Stable Flies ◽  
Normal Individuals ◽  
Gamma Irradiated

AbstractIn outdoor cage studies undertaken in the late summer of 1973, a method of estimating the absolute density of a stable fly (Stomoxys calcitrans (L.)) population was developed by correlating the average number of insects feeding or resting on a calf to the total number in the cage. Under the same cage conditions, where emigration, immigration, and to some extent, predation have been excluded, the daily mortality rate of normal stable flies marked with a fluorescent dye ranged from 25.3% to 27.3% dependent upon the sampling technique. Marker dyes have a deleterious effect on survival but surprisingly gamma irradiated flies succumbed at a lower rate than normal individuals.

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