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October 2012
Contents / home
Volunteers at the zoo
Let's stop hawkers
Vital role of our oceans
Holiday fun in the sun!
On the horns of a dilemma
Walkthrough aviary to open
Cape vulture chick born
Getting flamingo nests ready
Innovative magnetic sweeper
Bear necessities
ZooClub updates
Horned baboon spider
Conservation Grapevine

On the horns of a dilemma

The Bontebok (Damaliscus pygargus pygargus) and the Blesbok (Damaliscus pygargus phillipsi) originated from the endemic South African antelope (Damaliscus pygargus).

D. pygargus was distributed from the south-western Cape to the southern boundary of Zimbabwe. Due to climatic and habitat change, D. pygargus were divided into two groups -- Blesbok and Bontebok. Each group has morphological differences such as body markings and hide colours.

Historically the Bontebok's distribution was restricted to the coastal plains of the Western Cape.   The NZG's Dr Desiré Dalton and her team developed a DNA test that is set to become a valuable tool to confirm the purity of Bontebok and Blesbok populations.

Historical distribution

Historically the Blesbok was distributed in the grasslands of Gauteng, the Eastern Cape, Mpumalanga and Free State. The Bontebok's distribution was restricted to the coastal plains of the Western Cape, where its population size was reduced and driven to near extinction owing to hunting and human intrusion in the 1800s.

The ranges of the two sub-species were largely non-overlapping and they have different ecosystems. However, the deliberate mixing of Blesbok with Bontebok on game farms and the translocation of animals outside their former distribution range have resulted in a hybrid dilemma.

Test to determine hybridisation

Conservation agencies and the breeders association identified a need for a more sensitive and specific test to detect pure and hybrid animals, as they had concerns about the accuracy of the photographic test that was used. The Molecular Wildlife Genetics Unit at the NZG used a novel approach to assess hybridisation by identifying and developing a diagnostic DNA typing test consisting of eight species-specific and five cross-species microsatellite markers.

The 136 samples tested to date indicate a frequency of hybridisation of 40%. According to the IUCN there is approximately 3 500 Bontebok in South Africa. The results therefore imply that a large proportion of the Bontebok population may be hybrids.

Although hybridisation between closely related species can be a natural evolutionary process and has the potential of increasing genetic diversity over time, there are conservation implications. One of these is the Convention of Biodiversity, which aims to secure pure populations.

The DNA typing test will ultimately contribute to the accurate identification and genetic integrity of Bontebok populations. The test is set to become a valuable tool for conservation agencies and breeders wishing to confirm the purity of their populations.

By Anri van Wyk, Dr Desiré Dalton and Prof Antoinette Kotze, NZG

Zoo and Aquarium Visitor