Distribution and Abundance of Feral Livestock in the 'Top End' of the Northern Territory (1985-86), and Their Relation to Population Control.

1989 ◽  
Vol 16 (6) ◽  
pp. 651 ◽  
Author(s):  
P Bayliss ◽  
P Bayliss ◽  
KM Yeomans ◽  
KM Yeomans
Keyword(s):  
Population Control ◽  
Sampling Rate ◽  
Aerial Survey ◽  
Northern Territory ◽  
Population Estimates ◽  
Correction Factors ◽  
Coastal Lowland ◽  
Domestic Livestock ◽  
The Mean ◽  
Over The Top

Feral and domestic livestock (buffalo, cattle, horses and donkeys) were censused by fixed-wing aerial survey over the 'Top End' of the Northern Territory (above the 16th parallel) in March-April 1985, encompassing 233 672 km2 (16.7% of the Territory). The mean sampling rate on the major coastal lowland (38 281 km2) was 7.3%, and that for the rest was 3.7%. The accuracy of population estimates was improved by applying habitat-specific visibility correction factors to animals counted in groups.

scholarly journals Comparison of Surveys of Kangaroos in Queensland Using Helicopters and Fixed-Wing Aircraft.

1998 ◽  
Vol 20 (1) ◽  
pp. 92 ◽  
Author(s):  
AR Pople ◽  
SC Cairns ◽  
TF Clancy ◽  
GC Grigg ◽  
LA Beard ◽  
...  
Keyword(s):  
Aerial Survey ◽  
Population Estimates ◽  
Line Transect ◽  
Correction Factors ◽  
Density Estimates ◽  
Australian State ◽  
Transect Counts ◽  
Comparative Accuracy ◽  
Harvest Quotas ◽  
Strip Transect

Kangaroo harvest quotas for each Australian state have been set mainly as proportions of population estimates derived from aerial surveys. Estimating population size from strip transect counts using fixed- wing aircraft has become an established technique, but counts must be adjusted by correction factors to ensure population estimates are both accurate and repeatable. Surveys of kangaroos in Queensland are currently conducted with helicopters using line transect methodology, but cost restricts their use to relatively small survey blocks. Nevertheless, they return more accurate and repeatable estimates of kangaroo density than surveys with fixed-wing aircraft. A comparison of the above two techniques was made along the same transect lines in seven survey blocks (5000-10,000 km2) in southern and western Queensland, allowing an assessment of the comparative accuracy of the fixed-wing method. For red kangaroos (Macropus rufus), required correction factors of 0.7-3.1 were similar to those used previously. However, for eastern grey kangaroos (M. giganteus), substantially larger correction factors of 3.4-10.2 were needed to approach true density. For wallaroos (M. robustus), correction factors of 3.8-4.8 were required, but can be considered conservative because helicopter-derived density estimates are known to be underestimated by a factor of 2-3. Further work is needed to establish how correction factors for each species should be applied on a broader scale and whether they lead to repeatable estimates of kangaroo density. Key words: aerial survey, line transect, correction factors, strip transect, wallaroo.

scholarly journals Cerebral CT Perfusion in Acute Stroke: The Effect of Lowering the Tube Load and Sampling Rate on the Reproducibility of Parametric Maps

Diagnostics ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1121
Author(s):  
Georgios S. Ioannidis ◽  
Søren Christensen ◽  
Katerina Nikiforaki ◽  
Eleftherios Trivizakis ◽  
Kostas Perisinakis ◽  
...  
Keyword(s):  
Cerebral Blood Volume ◽  
Ct Perfusion ◽  
Sampling Rate ◽  
Volumetric Analysis ◽  
Sampling Interval ◽  
Diagnostic Efficiency ◽  
Temporal Sampling ◽  
Sampling Intervals ◽  
The Mean ◽  
Parametric Maps

The aim of this study was to define lower dose parameters (tube load and temporal sampling) for CT perfusion that still preserve the diagnostic efficiency of the derived parametric maps. Ninety stroke CT examinations from four clinical sites with 1 s temporal sampling and a range of tube loads (mAs) (100–180) were studied. Realistic CT noise was retrospectively added to simulate a CT perfusion protocol, with a maximum reduction of 40% tube load (mAs) combined with increased sampling intervals (up to 3 s). Perfusion maps from the original and simulated protocols were compared by: (a) similarity using a voxel-wise Pearson’s correlation coefficient r with in-house software; (b) volumetric analysis of the infarcted and hypoperfused volumes using commercial software. Pearson’s r values varied for the different perfusion metrics from 0.1 to 0.85. The mean slope of increase and cerebral blood volume present the highest r values, remaining consistently above 0.7 for all protocol versions with 2 s sampling interval. Reduction of the sampling rate from 2 s to 1 s had only modest impacts on a TMAX volume of 0.4 mL (IQR −1–3) (p = 0.04) and core volume of −1.1 mL (IQR −4–0) (p < 0.001), indicating dose savings of 50%, with no practical loss of diagnostic accuracy. The lowest possible dose protocol was 2 s temporal sampling and a tube load of 100 mAs.

scholarly journals Conservation implications of the temporal and spatial distribution of Bearded Vulture Gypaetus barbatus in Crete

2002 ◽  
Vol 12 (3) ◽  
pp. 269-280 ◽  
Author(s):  
Stavros Xirouchakis ◽  
Manolis Nikolakakis
Keyword(s):  
Distribution Patterns ◽  
High Mountains ◽  
Temporal And Spatial Distribution ◽  
Gypaetus Barbatus ◽  
Conservation Implications ◽  
Bearded Vulture ◽  
Nesting Sites ◽  
Domestic Livestock ◽  
The Mean ◽  
Temporal And Spatial

We carried out a four-year (1995-1999) survey on the foraging and breeding distribution of Bearded Vulture Gypaetus barbatus on the island of Crete. The age classes of all birds sighted were systematically recorded and data on seasonal distribution patterns were collected; 262 observations were made covering an area of about 4,000 km2, at altitudes ranging from 200 m to 2,450 m a.s.l (mean 1,100 m). Adult birds were distributed evenly throughout the island while young birds avoided active territories and were mostly sighted at the periphery of the high mountains. The species depended almost entirely on domestic livestock herded into and away from the mountains seasonally, with birds foraging in the uplands (> 1,200 m a.s.l.) from early May to late October and frequenting midland pastures (600-1,200 m a.s.l.) for the rest of the year. The mean altitude of nesting sites was 750 m (range = 280-1,450 m), with 80% of nests positioned below the 1,000 m contour. Bearded Vultures are more vulnerable to human-induced mortality within their breeding territories and on midland pastures in winter than in the upland areas in summer.

Factors Affecting Aerial Surveys of Marine Fauna, and Their Relationship to a Census of Dugongs in the Coastal Waters of the Northern-Territory

1986 ◽  
Vol 13 (1) ◽  
pp. 27 ◽  
Author(s):  
P Bayliss
Keyword(s):  
Coastal Waters ◽  
Total Population ◽  
Surface Condition ◽  
High Tide ◽  
Northern Territory ◽  
Probability Of Detection ◽  
Correction Factors ◽  
Marine Fauna ◽  
Factors Affecting ◽  
Similar Range

Some factors that may affect the aerial counts of dugongs, dolphins and turtles were examined experimentally. Tidal influence did not affect the counts of dugongs or dolphins, but those of turtles increased around high tide. A combined doubling of survey altitude and transect width reduced observed density of all three classes of animals by 50%. The counts of four observers did not differ significantly, but further data counsel caution. Overcast weather depressed counts of dugongs and turtles. Dolphin counts were affected by water surface condition, counts being lowest in choppy seas. A mark-recapture model was used on tandem observations to derive correction factors for groups of animals missed on the surface of a transect. Observers missed between 33% and 75% of dugong groups on the surface, the probability of detection decreasing with increased survey altitude and transect width. A similar range and pattern of probabilities was found for dolphins and turtles. Dugongs were censused in the coastal waters of the Northern Territory between the Daly River and Millingimbi in December 1983, an area of 28 746 km*2. Sampling intensity was 7.6%. A minimum population of 2953 � 530 (standard error) was estimated, an overall relative density of 0.11 � 0.02 km-2. A theoretical correction for submerged dugongs not seen yielded a total population estimate of 38 000, an overall density of 1.46 km-2. The distribution of dugongs in the survey area was patchy, the highest densities being associated with shallow coastal waters, sheltered bays, and large islands.

scholarly journals Demography of feral camels in central Australia and its relevance to population control

2010 ◽  
Vol 32 (1) ◽  
pp. 11 ◽  
Author(s):  
A. R. Pople ◽  
S. R. McLeod
Keyword(s):  
Population Control ◽  
Northern Territory ◽  
Adult Survival ◽  
Large Mammals ◽  
Limited Data ◽  
Control Programs ◽  
Rate Of Increase ◽  
Zero Growth ◽  
Central Australia ◽  
Alternative Species

Since their release over 100 years ago, camels have spread across central Australia and increased in number. Increasingly, they are being seen as a pest, with observed impacts from overgrazing and damage to infrastructure such as fences. Irregular aerial surveys since 1983 and an interview-based survey in 1966 suggest that camels have been increasing at close to their maximum rate. A comparison of three models of population growth fitted to these, albeit limited, data suggests that the Northern Territory population has indeed been growing at an annual exponential rate of r = 0.074, or 8% per year, with little evidence of a density-dependent brake. A stage-structured model using life history data from a central Australian camel population suggests that this rate approximates the theoretical maximum. Elasticity analysis indicates that adult survival is by far the biggest influence on rate of increase and that a 9% reduction in survival from 96% is needed to stop the population growing. In contrast, at least 70% of mature females need to be sterilised to have a similar effect. In a benign environment, a population of large mammals such as camels is expected to grow exponentially until close to carrying capacity. This will frustrate control programs, because an ever-increasing number of animals will need to be removed for zero growth the longer that culling or harvesting effort is delayed. A population projection for 2008 suggests ~10 500 animals need to be harvested across the Northern Territory. Current harvests are well short of this. The ability of commercial harvesting to control camel populations in central Australia will depend on the value of animals, access to animals and the presence of alternative species to harvest when camels are at low density.

Developing a census method based on sight counts to estimate rabbit (Oryctolagus cuniculus) numbers

2003 ◽  
Vol 30 (5) ◽  
pp. 487 ◽  
Author(s):  
Dylan W. Poole ◽  
Dave P. Cowan ◽  
Graham C. Smith
Keyword(s):  
Population Size ◽  
Field Trials ◽  
Population Estimates ◽  
Economic Costs ◽  
Natural Conditions ◽  
Commercial Farms ◽  
The Mean ◽  
The Difference ◽  
Study Sites ◽  
Autumn And Winter

A rabbit-census method, based on systematic counts conducted at night or at dawn and dusk, was developed and validated in terms of estimating the total number of rabbits present in a given area. Initially, models were developed under semi-natural conditions to describe the relationships between the numbers of rabbits counted and population size. Confidence limits were also calculated. The models were developed by comparing rabbit counts with the actual number of rabbits present, from a known population of animals. Only spotlight counts at night were considered reliable enough to estimate rabbit population size. During the autumn and winter months these represented ~60% of the population present. The model was subsequently validated, in two different exercises, following a series of field trials conducted under a variety of conditions on commercial farms. Initially, population estimates derived from the model were compared with those calculated using an alternative census technique. Population estimates, using the two techniques, were very similar at nine of the ten study sites. A second validation exercise was also conducted whereby the number of rabbits removed at each of the sites was compared with the difference between the mean pre- and post-removal spotlight counts. The results further supported the proposition that spotlight counts represent ~60% of the population present, with the difference between the two mean spotlight counts representing 61.2% (± 11.0, s.d.) of the number of rabbits removed. The census method therefore shows considerable promise as a means to estimate rabbit numbers under a range of agricultural conditions and therefore has the potential to predict accurately the economic costs of rabbit damage and also to gauge the effectiveness of various methods of rabbit control.

Accuracy of Pup Classifications and Its Effect on Population Estimates in the Hooded Seal (Cystophora cristata)

1988 ◽  
Vol 45 (4) ◽  
pp. 715-719 ◽  
Author(s):  
G. B. Stenson ◽  
R. A. Myers
Keyword(s):  
Developmental Stages ◽  
Survey Design ◽  
Aerial Survey ◽  
Similar Proportion ◽  
Population Estimates ◽  
Hooded Seal ◽  
Cystophora Cristata ◽  
Current Survey ◽  
Survey Estimates ◽  
Misclassification Rates

Information from the classification of age-specific developmental stages has been used to adjust aerial survey estimates of pup production in a number of species of seals, including the hooded seal (Cystophora cristata). We test the assumption that hooded seal pups were accurately and consistently classified according to developmental stage and examine the consequences of misclassifications upon adjusted population estimates. We determined overall misclassification rates, the effect of survey height on classifications, and interobserver variability. At ice level, misclassifications rates were low (<3%). From an altitude of 30 m, newborn pups could not be classified correctly and misclassification rates for the two other stages of attended pups varied between 6.4 and 21.3%. There was no evidence of an overall bias in classifications or differences among observers although there was a significant interaction between day and stage. Individual pups appear to have been misclassified independently by each observer. Under actual survey conditions, observers classified a similar proportion of pups into each recognizable stage. The misclassification rates we observed did not significantly alter the previous population estimate. Methods for improving the current survey design include modifying classification criteria, providing observers with a period of on-ice training, and reducing the width of survey transects.

A NEW APPLICATION OF ENSEMBLE EMD AMELIORATING THE ERROR FROM INSUFFICIENT SAMPLING RATE

2011 ◽  
Vol 03 (04) ◽  
pp. 493-508 ◽  
Author(s):  
DISHAN HUANG ◽  
YULIN XU
Keyword(s):  
Ball Bearing ◽  
Broad Band ◽  
Sampling Rate ◽  
Vibration Signal ◽  
Intrinsic Mode Functions ◽  
Mode Decomposition ◽  
Ensemble Mean ◽  
Mixed Noise ◽  
Bearing Vibration ◽  
The Mean

The objective of this paper is to apply an assisted noise method for ameliorating the empirical mode decomposition (EMD) error from insufficient sampling rate for a vibration signal. When the intrinsic mode functions (IMFs) are extracted from a signal mixed noise at a certain level on the sifting algorithm, an extraordinary phenomenon, where noise submerges the EMD error, is discovered. Thus, noise-assisted data is proposed to disturb the EMD error in the sifting process. In order to cancel out noise after serving its purpose, the IMFs are processed with an ensemble mean. As a result, the noise-assisted data ameliorates the EMD error from insufficient sampling rate, and the method treats the mean as the final true result. An EMD example of ball bearing vibration is presented to illustrate the validity of the approach. This paper recommends implementing the noise-assisted method in the EMD on vibration and acoustic signals with broad band.

Patterns of Aerial Photo Weather in Canada

1971 ◽  
Vol 25 (1) ◽  
pp. 42-48
Author(s):  
J. FLEMING
Keyword(s):  
Average Frequency ◽  
Aerial Survey ◽  
Observation Data ◽  
Frequency Of Occurrence ◽  
Mean Values ◽  
Solar Altitude ◽  
Weather Patterns ◽  
The Mean ◽  
Single Figure ◽  
Weather Observation

Weather suitable for high altitude aerial survey photography is defined in terms of cloud cover, horizontal visibility, and solar altitude. With these criteria established, relevant weather observation data, stored in the electronic archives of the Meteorological Service of Canada, were selected and used to compute a single figure value of average frequency of occurrence for each observation station, each month, for each of two minimum solar altitudes. Isopleths were then plotted on suitable base maps to depict the mean frequency of occurrence of observations meeting the criteria over a 10-year period. During the study of the accumulated data, it became apparent that four major areas which exhibit distinctive zonal photo weather patterns are to be found in Canada. Possible reasons for the existence of these zonal distributions are discussed in terms of their regional and local, geographical and meteorological characteristics. The information presented is statistical. Because of the nature of the computer program used to select data it was, unfortunately, not possible to compute standard deviations from mean values. This and other limitations on the application of the data to specific cases are discussed.

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