To breed or not to breed
Tuesday 5th March 2013
To breed or not to breed
Western Lowland Gorilla

Zoos around the world work together to breed and help save threatened species so that they survive the 21st century. This requires a careful balancing of the number of spaces available for individual animals of each species in global zoos. Globally zoos set specific goals as a base-line measure of success. As a general goal, zoos aim to retain 90% of the genetic diversity of a species found in the wild over an agreed time span. The pressures that have made the animals’ habitats vulnerable persist to the extent that many of the species cared for in zoo-based breeding programs cannot be successfully returned to the wild in current circumstances. As such, the focus for zoos is on the conservation of genetic diversity, so that the animals held in zoo-based population management programs are suitable for release whenever it is viable to do so, whether it be in 10, 50 or 100 years.

In order to maintain the goals of the Insurance Programs, each individual animal in the zoo population must contribute by breeding but also by not breeding too much as there are only a finite number of zoos and a finite number of spaces for each species. This means an equal genetic contribution is required from each bloodline as over-representation of a particular bloodline would jeopardise the goals of the program. Breeding is therefore limited to selected individuals each year, after an assessment of the genetic and demographic status of the breeding program, at the conclusion of the last breeding season.

The ultimate goal of zoo-based breeding programs is to maintain populations of animals that are genetically and behaviourally suitable for release to the wild when their native habitats are secure. It is therefore not realistic to compare the breeding rates of species in the wild with those in zoos as zoos must limit the number of animals born for genetic and demographic reasons.

The problem in the wild in many cases is not necessarily a shortage of animals. It is a shortage of secure habitat. Right now zoos around the world could breed, for example, hundreds of Sumatran Tigers for release to the wild. The problem is an ever shrinking wild, with a remnant wild population of animals under threat of poaching. More tigers in that situation are not desirable. Therefore many zoo programs are designed to be effective in ensuring the persistence of species in zoos for at least 100 years. Once the species’ habitat is secure, zoos will have genetically sound tigers for release if re-introduction or augmentation with zoo bred tigers is warranted.

In some scenarios we can breed for more imminent release of Australian species, such as the Corroboree Frog and the Regent Honeyeater.

The impact that zoos can have on the conservation of species is limited by the amount of space and resources they can offer to house and breed each species. Zoos therefore carefully balance the resources available with the potential contribution to a species’ survival. This means that each animal in the zoo must have a clearly defined role so that the available resources go to the best possible conservation outcomes, be it through breeding endangered species, scientific research or educating our visitors. 

For the Insurance Programs this means the zoos aim to only breed those species for which there is a role for the offspring either in our zoos or in a regional or global breeding program, or to only breed sufficient animals to replace animals as they die of old age.

Erna Walraven

Senior Curator