Already several years ago H. Zwartepoorte mentioned the necessity to split up the studbooks in several categories. This because of the fact that some studbooks were considered of higher priority than others for witch a different kind of management is required. Often studbooks for species that are very abundant in captivity appeared to be less successful as the studbooks became overfull and relations between animals were becoming unclear. The management of this kind of studbooks should there for be quit different in confront with studbooks with low numbers of animals and with a threatened category in the wild. In order to give to proper attention to each studbook the board split up the studbooks into several categories, which are presented below.
High protection. This category means that the species is threatened in the wild or is expected to become threatened in the near future and that keeping a genetically healthy population in captivity could be essential for the survival of the species.
Moderate protection. This category means that there is no direct danger of extinction for the species in the wild but close monitoring of the population stays important. This category will also be given to species of which the captive population is very small and or consists of a very limited number of bloodlines so careful breeding stays necessary.
Low protection. This category is given to species with save populations in the wild and in captivity.
The category of a studbook is evaluated yearly by the ESF-Board. Studbook keepers and advisory boards can and will be asked to advice on the category.