openCR (version 2.2.6)

PPNpossums: Orongorongo Valley Brushtail Possums

Description

A subset of brushtail possum (Trichosurus vulpecula) data from the Orongorongo Valley live-trapping study of Efford (1998) and Efford and Cowan (2005) that was used by Pledger, Pollock and Norris (2003, 2010). The OVpossumCH dataset in secr is a different selection of data from the same study. Consult ?OVpossumCH for more detail.

The data comprise captures in February of each year from 1980 to 1988.

Usage

FebpossumCH

Format

The format is a 9-session secr capthist object. Capture locations are not included.

Details

The data are captures of 448 animals (175 females and 273 males) over 9 trapping sessions comprising 4--10 occasions each. All were independent of their mothers, but age was not otherwise distinguished. The individual covariate sex takes values `F' or `M'.

Pledger, Pollock and Norris (2010) fitted 2-class finite mixture models for capture probability p and apparent survival phi, with or without allowance for temporal (between year) variation, using captures from only the first day of each trapping session. The first-day data relate to 270 individuals (115 females and 155 males).

References

Efford, M. G. (1998) Demographic consequences of sex-biased dispersal in a population of brushtail possums. Journal of Animal Ecology 67, 503--517.

Efford, M. G. and Cowan, P. E. (2004) Long-term population trend of Trichosurus vulpecula in the Orongorongo Valley, New Zealand. In: The Biology of Australian Possums and Gliders. Edited by R. L. Goldingay and S. M. Jackson. Surrey Beatty & Sons, Chipping Norton. Pp. 471--483.

Pledger, S., Pollock, K. H. and Norris, J. L. (2010) Open capture--recapture models with heterogeneity: II. Jolly--Seber model. Biometrics 66, 883--890.

Examples

summary(FebpossumCH) 
m.array(FebpossumCH)
JS.counts(FebpossumCH)

FebD1CH <- subset(FebpossumCH, occasion = 1)

if (FALSE) {

# reading the text file 'poss8088.data'

datadir <- system.file('extdata', package = 'openCR')
poss8088df <- read.table (paste0(datadir,'/poss8088.data'), header = TRUE)
capt <- poss8088df[,c('session','id','day','day','sex')]

# duplication of day is a trick to get a dummy trapID column in the right place
# this is needed because make.capthist does not have nonspatial option
capt$day.1[] <- 1  

# keep only February samples
capt <- capt[capt$session %% 3 == 1,]

# build nonspatial secr capthist object using dummy trapping grid
FebpossumCH <- make.capthist(capt, make.grid(1,2,ID='numx'))
# discard dummy traps objects
for (i in 1:9) attr(FebpossumCH[[i]], 'traps') <- NULL
names(FebpossumCH) <- 1980:1988 
sessionlabels(FebpossumCH) <- 1980:1988

}