7842

• UCREFRP Catalog Number: 7842
• Author: Knopf, F. L.
• Title: Biological Diversity in Wildlife Management.
• USFW Year: 1992.
• USFW - Doc Type: 1992.
• Copyright Material: NO

GUAM' RAILS
200
W
N_
cn 150
Z
O
H
100
IL
O
CL
LJ
50
t=
CL
Q
U
0
FROM THE WILD
REINTRODUCED
40
30
2Q 2
10 Z
0
1980 1982 1984 1986 1988 1990 1992
YEAR
Figure 2C. continued
ations to truly evaluate the success of this program.) Thus, the lack of an ideal
number of founders is not justification for abandoning or failing to initiate a captive
breeding program.
The target size also depends upon the generation length of the taxon under con-
sideration and how rapidly the population can grow from the founding phase to the
target size: given the same goal, fewer individuals will be required if the taxon has
a relatively long generation time or could grow more rapidly each generation (Ballou
1987, Soule et at. 1986). In the golden lion tamarin, if generation time could be
artificially extended from 6 to 10 years (e.g., by delaying age of first reproduction)
the target size would be 290 rather than 550.
In addition to genetic and demographic factors, the target population size also
must consider the number of spaces available in zoos. Populations of species that
are difficult to exhibit, c.g., the Guam rail, may be limited by the number of zoos
that can participate in the captive breeding program. The target size therefore may
Managing Genetic Diversity ? 271