Calibrating Aerial Surveys of Kangaroos by Comparison With Drive Counts

1988 ◽  
Vol 15 (3) ◽  
pp. 277 ◽  
Author(s):  
J Short ◽  
J Hone
Keyword(s):  
Aerial Survey ◽  
Survey Area ◽  
Aerial Surveys ◽  
Drive Counts

Densities of red and western grey kangaroos and euros were assessed by aerial survey and compared with densities obtained in the same area by drive counts. The survey area (12.1 km2) was long, narrow and sparsely vegetated. Lakes and a kangaroo-proof fence bounded the area on three sides facilitating the drive count. Densities from aerial surveys ranged between 38 and 54% of the corresponding drive counts for red kangaroos, between 15 and 23% for western grey kangaroos, and between 9 and 10% for euros. The time of morning at which the surveys were conducted altered these percentages. About twice as many red and western grey kangaroos were counted on aerial surveys at sunrise compared to surveys 3.5 h later.

scholarly journals Surfacing and vertical behaviour of Atlantic bluefin tuna (Thunnus thynnus) in the Mediterranean Sea: implications for aerial surveys

2020 ◽  
Vol 77 (5) ◽  
pp. 1979-1991
Author(s):  
Robert Klaus Bauer ◽  
Fabien Forget ◽  
Jean-Marc Fromentin ◽  
Manuela Capello
Keyword(s):  
Mediterranean Sea ◽  
Fork Length ◽  
Bluefin Tuna ◽  
Aerial Survey ◽  
Thunnus Thynnus ◽  
Survey Period ◽  
Atlantic Bluefin Tuna ◽  
Aerial Surveys ◽  
Gulf Of Lion ◽  
Nw Mediterranean

Abstract Atlantic bluefin tuna (Thunnus thynnus) (ABFT) frequently engage in surface basking and foraging behaviour that makes them detectable from afar. This behaviour is utilized for the development of fisheries-independent abundance indices based on aerial surveys, although changes in the surface-feeding dynamics of ABFT are not yet accounted for. We investigated the daytime surfacing behaviour of ABFT at different temporal and vertical resolutions based on 24 individuals (117–158 cm fork length), tagged with pop-up archival tags in the Gulf of Lion, NW-Mediterranean Sea between 2015 and 2016. The results suggest that ABFT remain usually <2 min continuously within the visible surface (0–1 m) during daytime. ABFT presence in the 0–1 and 0–20 m layers varied over time and between individuals but showed a seasonal decline towards autumn with the breakdown of thermal stratification. Furthermore, the rate of surfacing events was highly correlated with the time spent in the 0–20 m layer. Geolocation estimates confirm a strong site fidelity of ABFT during the aerial survey period (August–October) in the Gulf of Lion. Our results support the choice of the survey region and period, but related indices should account for the seasonality of ABFT surface behaviour [i.e. the time spent in the 0–20 m layer.

scholarly journals Boreal old-growth forest structural diversity challenges aerial photographic survey accuracy

2020 ◽  
Vol 50 (2) ◽  
pp. 155-169 ◽  
Author(s):  
Maxence Martin ◽  
Nicole J. Fenton ◽  
Hubert Morin
Keyword(s):  
Sustainable Forest Management ◽  
Forest Succession ◽  
Structural Diversity ◽  
Aerial Survey ◽  
Old Growth ◽  
Tree Species Composition ◽  
Forest Inventories ◽  
Old Growth Forest ◽  
Aerial Surveys ◽  
Old Growth Forests

The erosion of old-growth forests in boreal managed landscapes is a major issue currently faced by forest managers; however, resolving this problem requires accurate surveys. The intention of our study was to determine if historic operational aerial forest surveys accurately identified boreal old-growth forests in Quebec, Canada. We first compared stand successional stages (even-aged vs. old-growth) in two aerial surveys performed in 1968 (preindustrial aerial survey) and 2007 (modern aerial survey) on the same 2200 km2 territory. Second, we evaluated the accuracy of the modern aerial survey by comparing its results with those of 74 field plots sampled in the study territory between 2014 and 2016. The two aerial surveys differed significantly; 80.8% of the undisturbed stands that were identified as “old-growth” in the preindustrial survey were classified as “even-aged” in the modern survey, and 60% of the stands identified as “old-growth” by field sampling were also erroneously identified as “even-aged” by the modern aerial survey. The scarcity of obvious old-growth attributes in boreal old-growth forests, as well as poorly adapted modern aerial survey criteria (i.e., criteria requiring high vertical stratification and significant changes in tree species composition along forest succession), were the main factors explaining these errors. It is therefore likely that most of Quebec’s boreal old-growth forests are currently not recognized as such in forest inventories, challenging the efficacy of sustainable forest management policies.

Some human, aircraft and animal factors affecting aerial surveys: how to enumerate animals from the air

2008 ◽  
Vol 35 (4) ◽  
pp. 258 ◽  
Author(s):  
Peter J. S. Fleming ◽  
John P. Tracey
Keyword(s):  
Visual Acuity ◽  
New South ◽  
Human Memory ◽  
Aerial Survey ◽  
Factors Affecting ◽  
Counting Error ◽  
Aerial Surveys ◽  
South Wales ◽  
Survey Estimates ◽  
Aerial Platforms

Aerial surveys of wildlife involve a noisy platform carrying one or more observers moving over animals in order to quantify their abundance. This simple-sounding system encapsulates limits to human visual acuity and human concentration, visual attention, salience of target objects within the viewed scene, characteristics of survey platforms and facets of animal behaviours that affect the detection of animals by the airborne observers. These facets are too often ignored in aerial surveys, yet are inherent sources of counting error. Here we briefly review factors limiting the ability of observers to detect animals from aerial platforms in a range of sites, including characteristics of the aircraft, observers and target animals. Some of the previously uninvestigated limitations identified in the review were studied in central and western New South Wales, showing that inaccuracies of human memory and enumeration processes are sources of bias in aerial survey estimates. Standard protocols that minimise or account for the reviewed factors in aerial surveys of wildlife are recommended.

On bias, precision and accuracy in wildlife aerial surveys

2008 ◽  
Vol 35 (4) ◽  
pp. 253 ◽  
Author(s):  
Jim Hone
Keyword(s):  
Survey Data ◽  
Wildlife Management ◽  
Aerial Survey ◽  
Review Of The Literature ◽  
Density Estimates ◽  
True Value ◽  
Wildlife Population ◽  
Aerial Surveys ◽  
Precision And Accuracy ◽  
Definition Of

Bias, precision and accuracy have been studied extensively in wildlife population estimation including aerial surveys. A review of the literature shows that the concepts of bias and precision are used broadly consistently. Aerial survey data from known populations of feral pig carcases and white-tailed deer show that few density estimates are unbiased and precise. Research is needed, however, to clarify how much bias and how much precision are enough for the various types of wildlife management activities. Accuracy is used in two closely related but different ways. One set of definitions of accuracy relates to deviations from the true value (bias) and the second set relates to squared deviations from the true value (bias and precision). The implications are that authors are encouraged to clearly state which definition of accuracy they use, or focus solely on bias and precision.

scholarly journals Opportunistically collected data from aerial surveys reveal spatio-temporal distribution patterns of marine debris in German waters

2020 ◽  
Vol 28 (3) ◽  
pp. 2893-2903
Author(s):  
Bianca Unger ◽  
Helena Herr ◽  
Sacha Viquerat ◽  
Anita Gilles ◽  
Patricia Burkhardt-Holm ◽  
...  
Keyword(s):  
Temporal Distribution ◽  
Distribution Patterns ◽  
Aerial Survey ◽  
Marine Debris ◽  
Encounter Rate ◽  
The North ◽  
Aerial Surveys ◽  
Spatio Temporal ◽  
German Waters ◽  
The Baltic

AbstractMarine debris is known for its ubiquitousness and harmful effects on marine life. This study is the first analysis to provide information on the distribution of floating marine debris in German waters using aerial survey data collected between 2002 and 2016. During regular harbour porpoise monitoring flights, 191,167 km were covered and 26,512 floating debris items recorded (average encounter rate 0.1387 items/km). Debris was encountered more often in the North Sea than in the Baltic Sea (0.16 items/km; 0.08 items/km). The average encounter rate was higher in offshore waters than in coastal areas. Overlaps of marine debris distribution with ‘Special Areas of Conservation’ are a particular reason for concern. Moreover, the spring months (March–May) were identified to be the time of the year with the highest average encounter rates for marine debris. Fishing-related debris was shown to contribute up to 25% of the total number of all observed items. This study shows that opportunistically collected data on marine debris from aerial surveys are valuable for identifying distribution patterns of floating debris without additional survey effort and costs. These data can be used as baseline information to inform management schemes such as the Marine Strategy Framework Directive.

Aerial survey of walrus haul-out sites in west Spitsbergen and Moffen

Polar Record ◽  
1993 ◽  
Vol 29 (168) ◽  
pp. 55-58 ◽  
Author(s):  
E. Cruwys ◽  
Dan Weinstein
Keyword(s):  
Aerial Survey ◽  
Northwest Coast ◽  
Physiological Changes ◽  
Engine Noise ◽  
The Past ◽  
Aerial Surveys ◽  
Odobenus Rosmarus ◽  
West Spitsbergen ◽  
Odobenus Rosmarus Rosmarus

ABSTRACTIn July 1992 two aerial surveys were conducted to assess the size of the walrus (Odobenus rosmarus rosmarus) population at haul-out sites reported on the northwest coast of Spitsbergen and on Moffen. Walrus have been extensively hunted in Svalbard during the past 350 years, and in 1952 concern about decreasing stocks caused the Norwegian government to pass a law protecting the animals from hunting. At the time of the survey, it is likely that the walrus would have been at some stage of the moult, and it is tentatively suggested that the physiological changes reported to take place during moulting can cause lethargy and sluggishness that may make walrus less susceptible to disturbance by engine noise. Thirty-seven walrus were counted on the survey around Moffen, and three walrus on the northwest coast of Spitsbergen three days later.

scholarly journals Trends in the distribution and abundance of cetaceans from aerial surveys in Icelandic coastal waters, 1986-2001

2009 ◽  
Vol 7 ◽  
pp. 117 ◽  
Author(s):  
Daniel G Pike ◽  
Charles GM Paxton ◽  
Thorvaldur Gunnlaugsson ◽  
Gísli A Víkingsson
Keyword(s):  
Relative Abundance ◽  
Minke Whale ◽  
Humpback Whales ◽  
Line Transect ◽  
Survey Area ◽  
Balaenoptera Acutorostrata ◽  
The North ◽  
Aerial Surveys ◽  
Minke Whales ◽  
Abundance Estimates

Aerial surveys were carried out in coastal Icelandic waters 4 times between 1986 and 2001 as part of the North Atlantic Sightings Surveys. The surveys had nearly identical designs in 3 of the 4 years. The target species was the minke whale (Balaenoptera acutorostrata) but all species encountered were recorded. Sighting rate and density from line transect analysis were used as indices of relative abundance to monitor trends over the period, and abundance estimates corrected for perception biases were calculated for some species from the 2001 survey. More than 11 species were sighted, of which the most common were the minke whale, humpback whale (Megaptera novaeangliae), dolphins of genus Lagenorhychus, and the harbour porpoise (Phocoena phocoena). Minke whales anddolphins showed little change in distribution or abundance over the period. There were an estimated 31,653 (cv 0.30) dolphins in the survey area in 2001. Humpback whales increased rapidly at a rate of about 12%, with much of the increase occurring off eastern and northeastern Iceland. In 2001 there were an estimated 4,928 (cv 0.463) humpback whales in the survey area. The relative abundance of harbour porpoises decreased over the period, but estimates for this species were compromised by uncorrected perception biases and poor coverage. The ecological and historical significance of these findings with respect to previous whaling activities and present-day fisheries is discussed.

scholarly journals Application of an Ultralight Aircraft to Aerial Surveys of Kangaroos on Grazing Properties

1997 ◽  
Vol 24 (3) ◽  
pp. 359 ◽  
Author(s):  
G. C. Grigg ◽  
A. R. Pople ◽  
L. A. Beard
Keyword(s):  
Species Identification ◽  
Small Area ◽  
Aerial Survey ◽  
Accreditation Process ◽  
Line Transect ◽  
Future Scenario ◽  
Numerical Comparisons ◽  
Aerial Surveys

A Drifter ultralight aircraft was used as a platform for line-transect aerial surveys of three species of kangaroo in the sheep rangelands south-east of Blackall and north of Longreach in central-western Queensland in winter 1993 and 1994. Favourable comparisons between the results of ultralight surveys and those made from a helicopter flying the same transects and foot surveys along another set of transects, all within a few days of the ultralight survey, confirmed the expectation we had that an ultralight would be a satisfactory and much cheaper vehicle for conducting aerial surveys of kangaroos. The comparisons are even more favourable when data for the three species surveyed are combined, pointing to a problem in species identification and underlining the importance of using only experienced observers for aerial survey of kangaroos, whatever the platform. The use of an ultralight aircraft could have particular value where a comparatively small area, such as an individual sheep or cattle property, is under consideration. In this paper, we present the numerical comparisons, along with an evaluation of the practicability of using this type of aircraft. We also describe a possible future scenario in which an accreditation process could see approved kangaroo surveyors undertaking property assessments by ultralight, under contract to graziers or other interested parties.

scholarly journals Pilot aerial study of the marine megafauna in northern coast Alagoas, Brazil

2013 ◽  
Vol 41 (1-2) ◽  
Author(s):  
Maria Danise de Oliveira ALVES ◽  
João Carlos Gomes BORGES ◽  
Maria Elisabeth De ARAÚJO
Keyword(s):  
Sea Turtles ◽  
Water Clarity ◽  
Aerial Survey ◽  
Northern Coast ◽  
Sampling Area ◽  
Turbid Waters ◽  
Aerial Surveys ◽  
Low Visibility ◽  
Marine Megafauna ◽  
Strip Transect

This study aimed to investigate the feasibility of strip-transect aerial survey for the study of the marine megafauna in northern coast of Alagoas, chosen as the pilot area due to the better water clarity and the occurrence of the Antillean manatee. It was sighted 15 dolphins, 13 sea turtles and 10 manatees. From five aspects tested on the experimental flight, three adjustments were necessary on the methodology as following: 1) reduction of the transect angle to 40º to increase the sampling area; 2) constant transects of 1.5 nautical miles from shore to standardize the area of coverage; and 3) transects restricted to the mouths of estuaries due to low visibility in turbid waters. This study demonstrated the effectiveness of aerial surveys for the detection of marine megafauna. However, the adjustments proposed are necessary to minimize the characteristic limitations of each species and/or habitat. Keywords: aerial method, manatees, dolphins, sea turtles, limitations

Aerial survey methodology and the cost of control for feral goats in Western Queensland

1998 ◽  
Vol 25 (4) ◽  
pp. 393 ◽  
Author(s):  
A. R. Pople ◽  
T. F. Clancy ◽  
J. A. Thompson ◽  
S. Boyd-Law
Keyword(s):  
National Park ◽  
Survey Methodology ◽  
Aerial Survey ◽  
Capra Hircus ◽  
Effective Control ◽  
Correction Factors ◽  
Large Area ◽  
Aerial Surveys ◽  
The Cost ◽  
Capita Cost

Feral goats (Capra hircus) were shot from a helicopter on four sites in central-western Queensland. These sites centred on Idalia National Park (660 km2) and three nearby properties: Lissoy (360 km2), Mt Calder (260 km2) and Ravensbourne (320 km2), the order reflecting increasing goat density. On Idalia, 134 goats were shot in 8 h of flying time. On Lissoy, 28 goats were shot in 3 h, 1038 goats were shot on Mt Calder in 15 h, while 2307 goats were shot on Ravensbourne in 21 h. The reduction was monitored by aerial surveys using fixed-wing aircraft. No goats were recorded on either Idalia or Lissoy immediately following shooting and substantial reductions in goat numbers were achieved on Mt Calder (75%) and Ravensbourne (49%). Surveys conducted six months after this reduction indicated population increases on all sites following shooting. This was particularly marked on Ravensbourne, where goat numbers had increased by 31% despite further substantial removals by commercial mustering. These population increases were largely the result of immigration. The cooperation of landowners over a large area is therefore essential for effective control of goats. The per capita cost of shooting goats from a helicopter was essentially constant down to a threshold density of <1 goat km-2 , below which the cost increased substantially. The accuracy of fixed-wing aerial surveys was improved by using double-counting and these corrected estimates compared favourably with index–manipulation–index estimates. Estimates of densities <1 goat km-2 were imprecise and at these densities goats were difficult to detect. The extent of vegetation cover did not affect the sightability of goats, whereas group size was positively correlated with the sightability of goats. To estimate true density, correction factors of 1–2 were applied to goat group sizes using survey parameters of 100 m strip width, a survey height of 76 m and a speed of 187 km h-1.

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