Gopher Tortoise Distance Sampling Data

Description

This simulated data set by Mazerolle (2015) is based on the biological parameters for the Gopher Tortoise (Gopherus polyphemus) reported by Smith et al. (2009). A half-normal distribution with a scale of 10 and without an adjustment factor was used to simulate the distance data for a study area of 120 km^2. An effort of 500 m in 300 line transects was deployed. A density of 72 individuals per km^2 was used in the simulation using the approach outlined in Buckland et al. (2001).

Usage

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data(tortoise)

Format

A data frame with 410 observations on the following 5 variables.

Region.Label

a numeric identifier for the study area.

Area

a numeric variable for the surface area of the study area in square meters.

Sample.Label

a numeric identifier for each line transect relating each observation to its corresponding transect.

Effort

Effort in meters expended in each line transect.

distance

a numeric variable for the perpendicular distances in meters relative to the transect line for each of the individuals detected during the survey. Note that transects without detections have a value of NA for this variable.

Details

This data set is used to illustrate classic distance sampling (Buckland et al. 2001, Mazerolle 2015).

Source

Buckland, S. T., Anderson, D. R., Burnham, K. P., Laake, J. L., Borchers, D. L., Thomas, L. (2001) Introduction to distance sampling: estimating abundance of biological populations. Oxford University Press: Oxford.

Mazerolle, M. J. (2015) Estimating detectability and biological parameters of interest with the use of the R environment. Journal of Herpetology 49, 541–559.

Smith, L. L., Linehan, J. M., Stober, J. M., Elliott, M. J., Jensen, J. B. (2009) An evaluation of distance sampling for large-scale gopher tortoise surveys in Georgia, USA. Applied Herpetology 6, 355–368.

Examples

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data(tortoise)
str(tortoise)

##plot distance data to determine if truncation is required
##(Buckland et al. 2001, pp. 15--17)
hist(tortoise$distance)

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