FAO has produced several publications on the
management of at-risk small populations – see for
example FAO (1998). These documents provide a
more extensive review of the subject. Where the
Where the objective is merely to ensure the survival
of the population and the maintenance of its
integrity (as a pure population), the conservation
strategy is limited to monitoring the population,
and ensuring that inbreeding and effective
population size are within acceptable limits.
Inbreeding is the result of mating related
animals. In a small population, all animals in
future generations will come to be related to each
other, and mating among these animals will result
in inbreeding. The genetic effect of inbreeding is
increased homozygosity – the animal receives the
same alleles from both its parents. The degree of
inbreeding and homozygosity in future generations
can be predicted from the population size.
As there is almost always a much smaller
number of breeding males than breeding
females, the number of breeding males is the
more important factor determining the amount
of inbreeding. The effective population size (Ne
) is
a function of the number of breeding males and
breeding females. If Nm represents the number of
breeding males and Nf
represents the number of
breeding females, effective population size can
be calculated as:
Ne = (4NmNf
) / (Nm + Nf
)