Smithsonian National Zoological Park l Friends of the National Zoo



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.

Golden Lion Tamarin Pedigree

Avoiding Problems

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 genetic traits.

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 possible. Inbreeding 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.