Jackals culled to restore ecological processes

Dr Hector Magome

According to SANParks managing executive of conservation services, Dr Hector Magome, jackal numbers are being removed from some parks such as Mountain Zebra and Karoo National Parks. "This culling intervention is being implemented within SANParks' strategic adaptive management approach which allows a suite of management tools to be tested in order to maximise knowledge gained and to enhance SANParks' ability to manage national parks to achieve biodiversity aims."

He said jackals are culled in accordance with SANParks standard operating procedures for lethal population management, which has been approved by SANParks Animal Use and Care Committee.

Impact of large carnivores

Dr Magome said the Centre for African Conservation Ecology at the Nelson Mandela Metropolitan University in Port Elizabeth will analyse biological material from the culled jackals as part of existing research to further understanding of jackal diets, particularly when impacted by the presence of large carnivores such as cheetah and lion.

The establishment of large predators such as lions and cheetah, may have created conditions that hamper natural regulatory mechanisms of medium-sized predators such as jackal. Declines of smaller herbivore species such as springbok, klipspringer and duiker, together with observed increases in jackal abundances, have raised concerns about a possible collapse of predator-prey dynamics in some of these small national parks.

"A number of hypotheses regarding the factors involved in such a collapse were proposed during the workshops involving SANParks scientists and managers. Firstly, robust fencing erected to contain larger predators is likely to prevent mature jackals from dispersing as they would in open systems, resulting in high jackal abundances and associated increases in jackal predation pressure."

Predation on springbok lambs

He said the presence of large carnivores such as cheetah, lion and spotted hyena can improve food availability for jackals through the provision of carrion, thereby enhancing jackal population growth. In addition low densities or absence of solitary carnivores such as leopard, known to kill jackal, potentially reduces jackal mortality rates. A complex array of ecological processes may therefore have been disrupted at various levels within frontier parks, ultimately favoring jackal population growth.

Demographic studies on springbok, as an indicator a model of small herbivore species, have pinpointed predation on springbok lambs (less than six months old) by jackals as the cause of population declines in Mountain Zebra National Park. In Karoo National Park, springbok dispersed after the park was expanded, reducing springbok herd sizes and increasing their vulnerability to jackal. Here demographic studies indicated that springbok have been limited by small population sizes.

Dr Magome emphasised that the management intervention through a combination of prey introductions and predator removals, specifically jackal removals, is therefore required to reduce the risk of local extinction of small springbok populations. "Existence of different combinations of predators and prey, as well as varying management intervention histories within the frontier parks, provides an opportunity to maximise learning during strategic prey reintroduction and jackal removal exercises which will be monitored as part of a registered SANParks research project," he concluded.