Geoscience Reference
In-Depth Information
8
Open-Popu
lation Mark-Recapture Models
Bryan Manly, Jorge Navarro, and Trent McDonald
8.1 Introduction
Many of the developments in mark-recapture methodology have been
designed for open animal populations, with new animals entering through
births and immigration and animals leaving through deaths and emigration.
Studies usually involve sampling the population several times, with animals
suitably marked when they are first captured so that they can be recognized
when they are recaptured and a record obtained of the captures and recap-
tures of individual animals. Studies of open populations often cover extended
time periods, and the population changes that occur are of great interest to
ecologists and managers. Early methods for analyzing data from open pop-
ulations were proposed by Jackson (1939, 1940, 1944, 1948), Fisher and Ford
(1947), Leslie and Chitty (1951), and Leslie et al
.
(1953).
8.2 The Jolly-Seber Model
An important contribution to the literature on mark-recapture methods for
open populations was the Jolly-Seber (JS) model (Jolly, 1965; Seber, 1965),
which is at the heart of Pollock's (1991) diagram showing the relationship
between different open-population models (Figure 8.1). This model provides
explicit parameter estimators with variances on the assumption that (1)
every animal present in the population has the same probability
p
j
of being
captured in the
j
th sample taken at time
t
j
; (2) every marked animal present
in the population immediately after the
j
th sample has the same probability
ϕ
j
of surviving until the (
j
+ 1)th sample is taken; (3) marks are not lost or not
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