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

BLACK-FOOTED FERRETS
350
w 300
N_
V)
Z 250
0
J 200
EL
o 150
a
W
> 100
d
v 50
0
...................................................,.........
FROM THE WILD
REINTRODUCED
50
40 w
30 m
20 D
VO
1980 1982 1984 1986 1988 1990 1992
YEAR
Figure 2B. continued
increasing the planning period has a similar effect. For example, maintaining 90
percent of the ferret genetic variation for 100 years instead of 50 years would require
a target population of 1,300 rather than 500 individuals (Ballou and Oakleaf 1989).
For any given goal, increasing the number of founders reduces the required size
of the target population. As a "rule of thumb," 20 to 30 unrelated founders rep-
resenting the genetic diversity present in the wild population generally are sufficient
(Soule et al. 1986). In the ferrets, condors and rails (Table 2), captive breeding was
not initiated until after it was impossible to obtain this many founders. In such cases,
the number of founders cannot be changed. If it had been possible to obtain 25
founders for the ferret program, the target size would be 200 rather than 500 indi-
viduals. Although a small number of founders reduces the probability that a captive
breeding program will be successful, it does not reduce it to zero. For example, all
Speke's gazelles (Gazella spekei) currently in captivity are descended from four
individuals and this population appears to be thriving due to careful management
(Templeton and Read 1984). (However, it will require several more gazelle gener-
270 ? Trans. 57`' N. A. Wildl. & Nat. Res. Conf. (1992)