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Managing Small Populations in Captivity
The goal of most captive breeding programs for endangered
species is to establish captive populations that are large
enough to be demographically stable and genetically healthy.
But the numbers of animals in any one zoo is too small to
meet this goal. So zoos have linked together in cooperative
captive breeding programs, such as the American Zoo
Association’s Species Survival Program (SSP) to pool
their animals into one much larger managed population.
Unfortunately, even then the population may not be large
enough to remain genetically healthy over the long-term. Zoo
managers worry about the problems with inbreeding. When related
animals breed (inbreeding), their offspring often are unhealthy,
have reduced survival and reproduction, and may show harmful
To avoid these problems, zoo managers
- Try to maintain large captive
populations. The larger the population, the less
inbred it will become. In small populations, very quickly
all individuals become closely related. It becomes impossible
to avoid inbreeding. Managers often try to establish populations
that are large enough so that the population will only become
10% inbred over the next 100 years.
- Preserve the gene pool and avoid
inbreeding. When picking
the animals to breed, managers use pedigrees to make sure that all the
genes are preserved.
This maintains the genetic health of the population. They
also try to make
sure males and females are unrelated to the best extent
leads to lots of problems. Managers preserve the gene pool
by picking mates
to minimize the mean kinship in the population.
- Monitor the health of the population.
Periodic health examinations and analysis of birth and death
records allow zoo managers to detect any genetic problems
if they occur. Bringing in unrelated animals from other
zoos is the best way to avoid these problems.
Zoo scientists and other zoo managers have develop a number
of tools and techniques to help zoo managers maintain viable
healthy captive populations.