Introducing lions to a small-scale game reserve
- 3 MIN READ |
- August 29, 2019 |
- Science |
A recent study conducted in Dinokeng Game Reserve just north of Pretoria in Gauteng, South Africa has shown how lions introduced into a relatively small reserve will change their behaviour and choice of territory depending on interactions with neighbouring prides. Dinokeng is a relatively small reserve, spanning an area of 185 km2. The research was conducted by researchers at the Universities of the Witwatersrand (Wits) and Pretoria (UP).
Dinokeng was established by the Gauteng provincial government specifically as an ecotourism initiative and so does not necessarily reflect the conservation of a specific ecosystem or biome. These reserves are entirely fenced, leading to intense competition for resources and territories. Introduced animals also face the additional challenge of being in an unfamiliar environment where they need to explore and learn the locations of resources.
The study tracked 12 lions released in three tranches into the reserve. While this is a small study undertaken in a small reserve, the ability to track all the lions in the ecosystem yielded some fascinating results.
After an initial period of exploration, the lions became increasingly selective over time in which parts of their home ranges they used. Much of this selectivity was in response to other lions in the reserve, with less dominant individuals preferring less optimal areas to avoid their neighbours while more dominant males might actively choose areas with greater visibility to improve mating opportunities.
Lions released later in the study would also select less-optimal areas in response to being newcomers in a strange environment.
Within home ranges, lions selected areas with low elevation, gentle slopes, and high tree cover after release which is in line with other studies on large carnivores, suggesting preference for landscape features that can facilitate movement.
However, one lone male, who had seen his sibling killed in a territorial conflict with another pair of males, shifted from low elevations to high elevations, despite availability of low elevations, indicating how competitive interactions can result in a reversed habitat preference by the weaker individual to avoid further conflicts. This individual also preferred woodier areas throughout the study, as a further attempt to avoid conflict with neighbouring males.
Areas with denser vegetation improves prey ambushing success and provides shelter from competitors and human disturbances. All the lions preferred these environments initially. However, over time and especially after the third introduction (of females) both males and females began to prefer more open areas. This was likely triggered by the males need for greater visibility to detect the newly introduced females for mating opportunities, and the females need to avoid territorial conflict.
Studies in more open environments such as the Serengeti and Kalahari have reported more frequent encounters between male and female lions than more woody ecosystems such as the Kruger National Park or the Rwenzori Mountains National Park).
The changes suggest that lions optimize their use of the environment based on food accessibility as well as inter‐group interactions. Similar responses were found at the home range scale, with males expanding their home ranges to overlap with those of the newly introduced females, and the previously released females shifting theirs to avoid the new females.
The different priorities of males and females also influenced habitat selection. Males increase their fitness by maximizing mating opportunities and females by maximizing offspring survival. As a result, female lions are more risk sensitive than males and thus more likely to avoid human disturbances that are often perceived as a form of predation risk. In this study, males were more tolerant to human disturbances than females.
As anyone who has spent any time in a big 5 reserve will have guessed, the lions home ranges were established around the largest dam (0.43 km2) in the reserve and within their home ranges lions further selected areas close to the dams where prey density could be high. A similar pattern was observed in Hwange National Park, Zimbabwe, where lions preferred areas close to waterholes.
This study indicated that lions inhabit a complex social structure that extends beyond their immediate family group or territory. Throughout the study, both males and females altered their habitat use based on mating opportunities or perceived threats from the lions in neighbouring territories.
The study is published in the Journal of Zoology, Vol 307, Iss 2: Resource selection in reintroduced lions and the influence of intergroup interactions, and was authored by S. W. Yiu (Wits), L. Karczmarski, (UP), F. Parrini (Wits) and M. Keith (UP). The original article can be found here: https://doi.org/10.1111/jzo.12620.