homerange: Home Range Statistics
Description
Some 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). moves returns the
raw distances.
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.
MMDM (for `Mean Maximum Distance Moved') is the average maximum
distance between detections of each individual i.e. the observed range
length averaged over individuals (Otis et al. 1978).
ARL or `Asymptotic Range Length') is obtained by fitting an
exponential curve to the scatter of observed individual range length vs
the number of detections of each individual (Jett and Nichols 1987: 889).Usage
dbar(capthist)
RPSV(capthist)
MMDM(capthist, min.recapt = 1, full = FALSE)
ARL(capthist, min.recapt = 1, plt = FALSE, full = FALSE)
moves(capthist)
Arguments
min.recapt
integer minimum number of recaptures for a
detection history to be used
plt
logical; if TRUE observed range length is plotted against number
of recaptures
full
logical; set to TRUE for detailed output
Value
- Scalar distance in metres, or a list of such values if
capthist
is a multi-session list.
The full argument may be used with MMDM and ARL to
return more extensive output, particularly the observed range length for
each detection history.
Details
dbar is defined as
$$\overline{d}=\frac{\sum\limits _{i=1}^{n}
\sum\limits _{j=1}^{n_i - 1}
\sqrt{(x_{i,j}-x_{i,j+1})^2 + (y_{i,j}-y_{i,j+1})^2}}
{\sum\limits _{i=1}^{n} (n_i-1)}$$
RPSV is defined as
$$RPSV = \sqrt{
\frac {\sum\limits _{i=1}^{n} \sum\limits _{j=1}^{n_i} [
(x_{i,j} - \overline x_i)^2 + (y_{i,j} - \overline y_i)^2
]}{\sum\limits _{i=1}^{n} (n_i-1) - 1}}$$
dbar and RPSV have a specific role as proxies for
detection scale in inverse-prediction estimation of density (Efford
2004; see ip.secr).
RPSV is used in autoini to obtain plausible starting
values for maximum likelihood estimation.
MMDM and ARL discard data from detection histories
containing fewer than min.recapt+1 detections.References
Efford, M. G. (2004) Density estimation in live-trapping studies.
Oikos 106, 598--610.
Jett, D. A. and Nichols, J. D. (1987) A field comparison of nested grid
and trapping web density estimators. Journal of Mammalogy
68, 888--892.
Otis, D. L., Burnham, K. P., White, G. C. and Anderson, D. R. (1978)
Statistical inference from capture data on closed animal
populations. Wildlife Monographs 62, 1--135.