scholarly journals A latent capture history model for digital aerial surveys

Biometrics ◽  
2020 ◽  
Author(s):  
David L. Borchers ◽  
Peter Nightingale ◽  
Ben C. Stevenson ◽  
Rachel M. Fewster
Keyword(s):  
Aerial Surveys ◽  
Capture History

Profiles of gamma-ray and magnetic data from aerial surveys over the conterminous United States

Data Series ◽  
10.3133/ds31 ◽  
1999 ◽  
Author(s):  
Joseph S. Duval ◽  
Frederic E. Riggle
Keyword(s):  
United States ◽  
Gamma Ray ◽  
Magnetic Data ◽  
Aerial Surveys

scholarly journals Population estimates of Antillean manatees in Puerto Rico: an analytical framework for aerial surveys using multi-pass removal sampling

2019 ◽  
Vol 100 (4) ◽  
pp. 1340-1349
Author(s):  
Jaime A Collazo ◽  
Matthew J Krachey ◽  
Kenneth H Pollock ◽  
Francisco J Pérez-Aguilo ◽  
Jan P Zegarra ◽  
...  
Keyword(s):  
Puerto Rico ◽  
Detection Probability ◽  
Analytical Framework ◽  
Population Estimates ◽  
High Concentration ◽  
Imperfect Detection ◽  
Factors Affecting ◽  
Management Actions ◽  
Aerial Surveys ◽  
Population Size Estimates

AbstractEffective management of the threatened Antillean manatee (Trichechus manatus manatus) in Puerto Rico requires reliable estimates of population size. Estimates are needed to assess population responses to management actions, and whether recovery objectives have been met. Aerial surveys have been conducted since 1976, but none adjusted for imperfect detection. We summarize surveys since 1976, report on current distribution, and provide population estimates after accounting for apparent detection probability for surveys between June 2010 and March 2014. Estimates in areas of high concentration (hotspots) averaged 317 ± 101, three times higher than unadjusted counts (104 ± 0.56). Adjusted estimates in three areas outside hotspots also differed markedly from counts (75 ± 9.89 versus 19.5 ± 3.5). Average minimum island-wide estimate was 386 ± 89, similar to the maximum estimate of 360 suggested in 2005, but fewer than the 700 recently suggested by the Puerto Rico Manatee Conservation Center. Manatees were more widespread than previously understood. Improving estimates, locally or island-wide, will require stratifying the island differently and greater knowledge about factors affecting detection probability. Sharing our protocol with partners in nearby islands (e.g., Cuba, Jamaica, Hispaniola), whose populations share genetic make-up, would contribute to enhanced regional conservation through better population estimates and tracking range expansion.El manejo efectivo del manatí antillano amenazado en Puerto Rico requiere estimados de tamaños de poblaciónes confiables. Dichas estimaciones poblacionales son necesarias para evaluar las respuestas a las acciones de manejo, y para determinar si los objetivos de recuperación han sido alcanzados. Se han realizado censos aéreos desde 1976, pero ninguno de ellos han sido ajustados para detecciones imperfectas. Aquí resumimos los censos desde 1976, actualizamos la distribución, y reportamos los primeros estimados poblacionales ajustados para la probabilidad de detección aparente en los censos de Junio 2010 a Marzo 2014. Las estimaciones poblacionales en áreas de mayor concentración del manatí promedió 317 ± 103, tres veces más abundante que los conteos sin ajuste (104 ± 0.56). Las estimaciones poblacionales en tres áreas fuera de las áreas de mayor concentración del manatí también fueron marcadamente diferentes (75 ± 9.89 vs 19.5 ± 3.5). El estimado mínimo poblacional en la isla entera fue de 386 ± 89, similar al estimado máximo de 360 sugerido en el año 2005, pero menor a los 700 sugeridos recientemente por el Centro de Conservación de Manatíes de Puerto Rico. Documentamos que el manatí tiene una distribución más amplia de lo que se sabía con anterioridad. El mejoramiento de los estimados poblacionales locales o a nivel de isla requerirá que se estratifique a la isla en forma diferente y que se investiguen los factores que influencian a la probabilidad de detección. Compartir protocolos como este con colaboradores de islas vecinas (por. ej., Cuba, Jamaica, Española), cuyas poblaciones de manatíes comparten material genético, contribuiría a la conservación regional mediante mejores estimaciones poblacionales y monitoreo de la expansión de su ámbito doméstico.

scholarly journals Drivers of Bornean Orangutan Distribution across a Multiple-Use Tropical Landscape

2021 ◽  
Vol 13 (3) ◽  
pp. 458
Author(s):  
Sol Milne ◽  
Julien G. A. Martin ◽  
Glen Reynolds ◽  
Charles S. Vairappan ◽  
Eleanor M. Slade ◽  
...  
Keyword(s):  
Forest Cover ◽  
Food Resource ◽  
Multiple Use ◽  
Natural Forests ◽  
Bornean Orangutan ◽  
Aerial Surveys ◽  
Significant Difference ◽  
The Difference ◽  
Fig Trees ◽  
Abundance And Distribution

Logging and conversion of tropical forests in Southeast Asia have resulted in the expansion of landscapes containing a mosaic of habitats that may vary in their ability to sustain local biodiversity. However, the complexity of these landscapes makes it difficult to assess abundance and distribution of some species using ground-based surveys alone. Here, we deployed a combination of ground-transects and aerial surveys to determine drivers of the critically endangered Bornean Orangutan (Pongo pygmaeus morio) distribution across a large multiple-use landscape in Sabah, Malaysian Borneo. Ground-transects and aerial surveys using drones were conducted for orangutan nests and hemi-epiphytic strangler fig trees (Ficus spp.) (an important food resource) in 48 survey areas across 76 km2, within a study landscape of 261 km2. Orangutan nest count data were fitted to models accounting for variation in land use, above-ground carbon density (ACD, a surrogate for forest quality), strangler fig density, and elevation (between 117 and 675 m). Orangutan nest counts were significantly higher in all land uses possessing natural forest cover, regardless of degradation status, than in monoculture plantations. Within these natural forests, nest counts increased with higher ACD and strangler fig density, but not with elevation. In logged forest (ACD 14–150 Mg ha−1), strangler fig density had a significant, positive relationship with orangutan nest counts, but this relationship disappeared in a forest with higher carbon content (ACD 150–209 Mg ha−1). Based on an area-to-area comparison, orangutan nest counts from ground transects were higher than from counts derived from aerial surveys, but this did not constitute a statistically significant difference. Although the difference in nest counts was not significantly different, this analysis indicates that both methods under-sample the total number of nests present within a given area. Aerial surveys are, therefore, a useful method for assessing the orangutan habitat use over large areas. However, the under-estimation of nest counts by both methods suggests that a small number of ground surveys should be retained in future surveys using this technique, particularly in areas with dense understory vegetation. This study shows that even highly degraded forests may be a suitable orangutan habitat as long as strangler fig trees remain intact after areas of forest are logged. Enrichment planting of strangler figs may, therefore, be a valuable tool for orangutan conservation in these landscapes.

scholarly journals Assessment and novel application of N ‐mixture models for aerial surveys of wildlife

Ecosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
Author(s):  
Sonja A. Christensen ◽  
Matthew T. Farr ◽  
David M. Williams
Keyword(s):  
Mixture Models ◽  
Aerial Surveys

Correcting for Visibility Bias in Strip Transect Aerial Surveys of Aquatic Fauna

1989 ◽  
Vol 53 (4) ◽  
pp. 1017 ◽  
Author(s):  
H. Marsh ◽  
D. F. Sinclair
Keyword(s):  
Aquatic Fauna ◽  
Aerial Surveys ◽  
Strip Transect

Change in abundance of dugongs in Shark Bay, Ningaloo and Exmouth Gulf, Western Australia: evidence for large-scale migration

2004 ◽  
Vol 31 (3) ◽  
pp. 283 ◽  
Author(s):  
Nick Gales ◽  
Robert D. McCauley ◽  
Janet Lanyon ◽  
Dave Holley
Keyword(s):  
Marine Protected Areas ◽  
Large Scale ◽  
Population Demographics ◽  
Shark Bay ◽  
Ningaloo Reef ◽  
Aerial Surveys ◽  
Large Numbers ◽  
Plausible Hypothesis ◽  
Exmouth Gulf ◽  
Regional Abundance

The third in a series of five-yearly aerial surveys for dugongs in Shark Bay, Ningaloo Reef and Exmouth Gulf was conducted in July 1999. The first two surveys provided evidence of an apparently stable population of dugongs, with ~1000 animals in each of Exmouth Gulf and Ningaloo Reef, and 10 000 in Shark Bay. We report estimates of less than 200 for each of Exmouth Gulf and Ningaloo Reef and ~14 000 for Shark Bay. This is an apparent overall increase in the dugong population over this whole region, but with a distributional shift of animals to the south. The most plausible hypothesis to account for a large component of this apparent population shift is that animals in Exmouth Gulf and Ningaloo Reef moved to Shark Bay, most likely after Tropical Cyclone Vance impacted available dugong forage in the northern habitat. Bias associated with survey estimate methodology, and normal changes in population demographics may also have contributed to the change. The movement of large numbers of dugongs over the scale we suggest has important management implications. First, such habitat-driven shifts in regional abundance will need to be incorporated in assessing the effectiveness of marine protected areas that aim to protect dugongs and their habitat. Second, in circumstances where aerial surveys are used to estimate relative trends in abundance of dugongs, animal movements of the type we propose could lead to errors in interpretation.

Closure to “Aerial Surveys for Reservoir Planning”

1956 ◽  
Vol 121 (1) ◽  
pp. 519-520
Author(s):  
Francis J. Guscio
Keyword(s):  
Aerial Surveys ◽  
Reservoir Planning

scholarly journals Changes in number and distribution of hippoptamus (Hippopotamus amphibius) in the Sabie River, Kruger National Park, during the 1992 drought

Koedoe ◽  
1995 ◽  
Vol 38 (2) ◽  
Author(s):  
P.C. Viljoen
Keyword(s):  
Southern Africa ◽  
National Park ◽  
Dry Season ◽  
Kruger National Park ◽  
Population Densities ◽  
Drought Period ◽  
Aerial Surveys ◽  
Hippopotamus Amphibius ◽  
Reduced Flow

The 1991/92 drought in Southern Africa and the effect of the resultant reduced flow of the Sabie River on hippopotami was investigated. Hippopotami are counted annually in the Kruger National Park's (KNP) major rivers as part of the park's monitoring pro- gramme. Two additional aerial surveys were conducted to document changes in hippopotamus population densities in the Sabie River during the drought period. The hippopotamus population decreased during the drought by 12.6 to 672 animals between July 1991 and October 1992. The highest and lowest hippopotamus densities recorded were 11.6 and 2.2 animals/km river length respectively in different river sections. Only 12 hippopotamus mortalities were recorded at the end of the 1992 dry season (October).

scholarly journals The influence of animal mobility on the assumption of uniform distances in aerial line-transect surveys

2008 ◽  
Vol 35 (4) ◽  
pp. 275 ◽  
Author(s):  
Rachel M. Fewster ◽  
Colin Southwell ◽  
David L. Borchers ◽  
Stephen T. Buckland ◽  
Anthony R. Pople
Keyword(s):  
Survey Design ◽  
Distance Sampling ◽  
High Mobility ◽  
Line Transect ◽  
Transect Line ◽  
Aerial Surveys ◽  
Pack Ice ◽  
Capture Recapture ◽  
Distance Data ◽  
Crabeater Seals

Line-transect distance sampling is a widely used method for estimating animal density from aerial surveys. Analysis of line-transect distance data usually relies on a requirement that the statistical distribution of distances of animal groups from the transect line is uniform. We show that this requirement is satisfied by the survey design if all other assumptions of distance sampling hold, but it can be violated by consistent survey problems such as responsive movement of the animals towards or away from the observer. We hypothesise that problems with the uniform requirement are unlikely to be encountered for immobile taxa, but might become substantial for species of high mobility. We test evidence for non-uniformity using double-observer distance data from two aerial surveys of five species with a spectrum of mobility capabilities and tendencies. No clear evidence against uniformity was found for crabeater seals or emperor penguins on the pack-ice in East Antarctica, while minor non-uniformity consistent with responsive movement up to 30 m was found for Adelie penguins. Strong evidence of either non-uniformity or a failure of the capture–recapture validating method was found for eastern grey kangaroos and red kangaroos in Queensland.

Aerial Surveys of Isle De Pasqua: Easter Island and the New Birdmen

Easter Island ◽  
2003 ◽  
pp. 187-194
Author(s):  
Robert A. Hemm ◽  
Marcelo Mendez
Keyword(s):  
Easter Island ◽  
Aerial Surveys
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