Home Range Statistics

Description

Two ad hoc measures of home range size may be calculated in secr from capture–recapture data:

dbar is the mean distance between consecutive capture locations, pooled over individuals (e.g. Efford 2004).

RPSV (for 'Root Pooled Spatial Variance') is a measure of the 2-D dispersion of the locations at which individual animals are detected, pooled over individuals.

Usage

dbar(capthist)
RPSV(capthist)

Arguments

Details

dbar is defined as

see pdf manual

RPSV is defined as

see pdf manual

dbar and RPSV have a specific role as proxies for home-range size in inverse-prediction estimation of density (Efford 2004; see ip.secr).

dbar is used in autoini to obtain plausible starting values for maximum likelihood estimation.

Value

Scalar distance in metres, or a list of such values if capthist is a multi-session list.

Note

Both measures are affected by the arrangement of detectors. dbar is also affected quite strongly by serial correlation in the sampled locations. Using dbar with 'proximity' detectors raises a problem of interpretation, as the original sequence of multiple detections within an occasion is unknown. RPSV is a value analogous to the standard deviation of locations about the home range centre.

Inclusion of these measures in the secr package does not mean they are recommended for general use! It is usually better to use a spatial parameter from a fitted model (e.g., sigma of the half-normal detection function). Even then, be careful that sigma is not 'contaminated' with behavioural effects (e.g. attraction of animal to detector) or 'detection at a distance'.

Author(s)

Murray Efford murray.efford@otago.ac.nz

References

Efford, M. G. (2004) Density estimation in live-trapping studies. Oikos 106, 598–610.

See Also

autoini

Examples

data(captdata)  
dbar(captdata)
RPSV(captdata)