Trappability of coyotes relative to home range boundaries

1983 ◽  
Vol 61 (8) ◽  
pp. 1932-1934 ◽  
Author(s):  
John W. Laundré ◽  
Barry L. Keller
Keyword(s):  
Home Range ◽  
Equal Probability ◽  
Range Boundary ◽  
Probability Of Capture

Trappability of coyotes relative to location of the home range boundary was examined to determine whether animals were more susceptible to capture in an unfamiliar area. Susceptibility to trapping did not appear to increase on the edge or outside of home range boundaries, but equal probability of capture in areas receiving different intensities of use still needs to be assessed.

scholarly journals Sampling designs matching species biology produce accurate and affordable abundance indices

2013 ◽  
Author(s):  
Grant Harris ◽  
Sean Farley ◽  
Gareth J Russell ◽  
Matthew J Butler ◽  
Jeff Selinger
Keyword(s):  
Expert Opinion ◽  
Equal Probability ◽  
Sampling Frame ◽  
Brown Bears ◽  
Encounter Rates ◽  
Unequal Probability ◽  
Targeted Sampling ◽  
Abundance Estimates ◽  
Abundance Indices ◽  
Probability Of Capture

Wildlife biologists often use grid-based designs to sample animals and generate abundance estimates. Although sampling in grids is theoretically sound, in application, the method can be logistically difficult and expensive when sampling elusive species inhabiting extensive areas. These factors make it challenging to sample animals and meet the statistical assumption of all individuals having an equal probability of capture. Violating this assumption biases results. Does an alternative exist? Perhaps by sampling only where resources attract animals (i.e. targeted sampling), it would provide accurate abundance estimates more efficiently and affordably. However, biases from this approach would also arise if individuals have an unequal probability of capture, especially if some failed to visit the sampling area. Since most biological programs are resource limited, and acquiring abundance data drives many conservation and management applications, it becomes imperative to identify economical and informative sampling designs. Therefore, we evaluated abundance estimates generated from grid and targeted sampling designs using simulations based on geographic positioning system (GPS) data from 42 Alaskan brown bears (Ursus arctos). Migratory salmon drew brown bears from the wider landscape, concentrating them at anadromous streams. This provided a scenario for testing the targeted approach. Grid and targeted sampling varied by trap amount, location (traps placed randomly, systematically or by expert opinion), and traps stationary or moved between capture sessions. We began by identifying when to sample, and if bears had equal probability of capture. We compared abundance estimates against seven criteria: bias, precision, accuracy, effort, plus encounter rates, and probabilities of capture and recapture. One grid (49 km2 cells) and one targeted configuration provided the most accurate results. Both placed traps by expert opinion and moved traps between capture sessions, which raised capture probabilities. The grid design was least biased (-10.5%), but imprecise (CV 21.2%), and used most effort (16,100 trap-nights). The targeted configuration was more biased (-17.3%), but most precise (CV 12.3%), with least effort (7,000 trap-nights). Targeted sampling generated encounter rates four times higher, and capture and recapture probabilities 11% and 60% higher than grid sampling, in a sampling frame 88% smaller. Bears had unequal probability of capture with both sampling designs, partly because some bears never had traps available to sample them. Hence, grid and targeted sampling generated abundance indices, not estimates. Overall, targeted sampling provided the most accurate and affordable design to index abundance. Targeted sampling may offer an alternative method to index the abundance of other species inhabiting expansive and inaccessible landscapes elsewhere, provided their attraction to resource concentrations.

Aspects of the population dynamics of the western rock lobster, Panulirus cygnus George. I. Estimation of population density

1974 ◽  
Vol 25 (2) ◽  
pp. 235 ◽  
Author(s):  
GR Morgan
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Population Size ◽  
Equal Probability ◽  
Rock Lobster ◽  
Single Population ◽  
Baited Traps ◽  
Unbiased Estimates ◽  
Panulirus Cygnus ◽  
Probability Of Capture

Breakdowns in the assumptions made by the Jolly (1965) method of estimating population size were detected in mark-recapture experiments with the western rock lobster. Using information gathered from sampling by both baited traps and by diving it was shown that, in particular, the assumptions of (1) a single population and (2) equal probability of capture of marked and unmarked rock lobsters, were not valid at all times in the 'population' studied, and this resulted in underestimates of population density. However, it was found possible to make suitable corrections to the raw data to arrive at apparently unbiased estimates of population density. In the cases studied, the calculated unbiased estimates of population density agreed well with unbiased estimates calculated from information gathered by marking and recapturing by different methods. Single census and the De Lury (1958) methods also grossly underestimated population density.

scholarly journals Sampling designs matching species biology produce accurate and affordable abundance indices

2013 ◽  
Author(s):  
Grant Harris ◽  
Sean Farley ◽  
Gareth J Russell ◽  
Matthew J Butler ◽  
Jeff Selinger
Keyword(s):  
Expert Opinion ◽  
Equal Probability ◽  
Sampling Frame ◽  
Brown Bears ◽  
Encounter Rates ◽  
Unequal Probability ◽  
Targeted Sampling ◽  
Abundance Estimates ◽  
Abundance Indices ◽  
Probability Of Capture

Wildlife biologists often use grid-based designs to sample animals and generate abundance estimates. Although sampling in grids is theoretically sound, in application, the method can be logistically difficult and expensive when sampling elusive species inhabiting extensive areas. These factors make it challenging to sample animals and meet the statistical assumption of all individuals having an equal probability of capture. Violating this assumption biases results. Does an alternative exist? Perhaps by sampling only where resources attract animals (i.e. targeted sampling), it would provide accurate abundance estimates more efficiently and affordably. However, biases from this approach would also arise if individuals have an unequal probability of capture, especially if some failed to visit the sampling area. Since most biological programs are resource limited, and acquiring abundance data drives many conservation and management applications, it becomes imperative to identify economical and informative sampling designs. Therefore, we evaluated abundance estimates generated from grid and targeted sampling designs using simulations based on geographic positioning system (GPS) data from 42 Alaskan brown bears (Ursus arctos). Migratory salmon drew brown bears from the wider landscape, concentrating them at anadromous streams. This provided a scenario for testing the targeted approach. Grid and targeted sampling varied by trap amount, location (traps placed randomly, systematically or by expert opinion), and traps stationary or moved between capture sessions. We began by identifying when to sample, and if bears had equal probability of capture. We compared abundance estimates against seven criteria: bias, precision, accuracy, effort, plus encounter rates, and probabilities of capture and recapture. One grid (49 km2 cells) and one targeted configuration provided the most accurate results. Both placed traps by expert opinion and moved traps between capture sessions, which raised capture probabilities. The grid design was least biased (-10.5%), but imprecise (CV 21.2%), and used most effort (16,100 trap-nights). The targeted configuration was more biased (-17.3%), but most precise (CV 12.3%), with least effort (7,000 trap-nights). Targeted sampling generated encounter rates four times higher, and capture and recapture probabilities 11% and 60% higher than grid sampling, in a sampling frame 88% smaller. Bears had unequal probability of capture with both sampling designs, partly because some bears never had traps available to sample them. Hence, grid and targeted sampling generated abundance indices, not estimates. Overall, targeted sampling provided the most accurate and affordable design to index abundance. Targeted sampling may offer an alternative method to index the abundance of other species inhabiting expansive and inaccessible landscapes elsewhere, provided their attraction to resource concentrations.

From the Oort cloud to Halley-type comets

1999 ◽  
Vol 173 ◽  
pp. 327-338 ◽  
Author(s):  
J.A. Fernández ◽  
T. Gallardo
Keyword(s):  
Total Population ◽  
Complex Function ◽  
Dynamical Evolution ◽  
Oort Cloud ◽  
Capture Process ◽  
Influx Rate ◽  
Short Period ◽  
Dynamical Properties ◽  
Orbital Periods ◽  
Probability Of Capture

AbstractThe Oort cloud probably is the source of Halley-type (HT) comets and perhaps of some Jupiter-family (JF) comets. The process of capture of Oort cloud comets into HT comets by planetary perturbations and its efficiency are very important problems in comet ary dynamics. A small fraction of comets coming from the Oort cloud − of about 10−2− are found to become HT comets (orbital periods < 200 yr). The steady-state population of HT comets is a complex function of the influx rate of new comets, the probability of capture and their physical lifetimes. From the discovery rate of active HT comets, their total population can be estimated to be of a few hundreds for perihelion distancesq <2 AU. Randomly-oriented LP comets captured into short-period orbits (orbital periods < 20 yr) show dynamical properties that do not match the observed properties of JF comets, in particular the distribution of their orbital inclinations, so Oort cloud comets can be ruled out as a suitable source for most JF comets. The scope of this presentation is to review the capture process of new comets into HT and short-period orbits, including the possibility that some of them may become sungrazers during their dynamical evolution.

Seasonal Changes in the Home Range of the Antelope Jackrabbit (Lepus alleni)

Mammal Study ◽  
2019 ◽  
Vol 44 (2) ◽  
pp. 1
Author(s):  
Maria M. Altemus ◽  
John L. Koprowski ◽  
David E. Brown
Keyword(s):  
Home Range ◽  
Seasonal Changes

Foraging Habitat, Home-Range Size and Diet of a Mediterranean Bat Species, Savi's Pipistrelle

2019 ◽  
Vol 20 (2) ◽  
pp. 351
Author(s):  
Marina Kipson ◽  
Martin Šálek ◽  
Radek Lučan ◽  
Marcel Uhrin ◽  
Edita Maxinová ◽  
...  
Keyword(s):  
Home Range ◽  
Home Range Size ◽  
Range Size ◽  
Foraging Habitat
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