The reintroduction of large predators is becoming an increasingly popular ecotourism strategy on small reserves, but ranchers should note that just a few lions can kill a lot of prey animals every year. Roelof Bezuidenhout reports.
Studies on the feeding habits of lion groups and the number of animals they are likely to take can help managers select the best pride size and composition, as well as the best prey base, for any particular ranch. One such study in the Karongwe Game Reserve, between Hoedspruit and Tzaneen, Limpopo, focused on a single pride of lions. According to the researchers, Monika Lehmann and Paul Funston of the Department of Nature Conservation at the Tshwane University of Technology, the aim was to determine the prey requirements of one pride and its related males in an enclosed reserve.
The 8 500ha reserve was effectively the pride’s home range. Although there were no other lions, there was competition from other large predators including leopard, cheetah, and spotted hyena to consider. Lions live in permanent social units that may exist for generations. But although the pride is a cohesive unit, its members may be scattered in groups throughout its range at any one time. It’s rare to find all pride members together. According to Paul, the founder population consisted of two brothers and two unrelated lionesses. “Over six years after they were released, they had five litters of two or three cubs each.
The first sub-adult group was formed in 2002, consisting of one male and one female, with a sub-adult group splitting off every year after that. “Two of the males formed a coalition to govern the pride – behaviour which increases their chance of tenure in the pride – but one was removed by the reserve’s management after three years as the pair were taking more prey than a single male would alone,” he says. The lion population over the six-year trial period varied between four and 11 and had access to about 377 960kg of available biomass, including 1 571 impala, 152 kudu, 77 giraffe and 178 Burchell’s zebra (the figures are based on the average number of each species on the ranch). The lions preyed on 21 species and probably made about 1 500 kills, although the research team only located 43% of these. This is an informed guess based on the amount of food any particular average-sized lion (referred to as a lion feeding unit or LFU) would be expected to consume for normal body maintenance and reproduction.
King-size appetites
But the researchers say the total biomass killed per LFU is more important for management than the actual number of kills, as group size and composition impact on prey selection. Collectively, the lions made an average of 42 kills per LFU per year and an average of 21 kills per month. Blue wildebeest, warthog, waterbuck, zebra and impala were the most preferred species. They killed between 3,3% and 7,1% of available prey annually, eating 6,9kg/day to 12,1kg/day and killing every 1,8 days.
Clearly, say the researchers, reserves should ensure the preferred prey base is large enough to sustain a lion population as well as other predators. But lions won’t hunt only those animals you want them to hunt. This, warns Paul, undermines the theory that buffer species such as impala – which were heavily utilised by cheetah, leopard, and wild dogs – reduce predation on rarer species.
“Lions tend to prey on larger prey (190kg to 550kg) and don’t compete directly with smaller predators for most prey species,” he says. “Even though gemsbok, red hartebeest and eland were present in very low numbers, the lions appeared to select them. Perhaps because they’re alien to the area they were more vulnerable to predation.”
Population control
In small enclosed reserves, fences prevent migration or movement when food is in short supply, as well as the dispersal of sub-adults and the arrival of new individuals and therefore new genes. Paul says populations must be actively managed to prevent overutilisation of resources and to ensure genetic integrity. One of the main considerations is managing males and sub-adult lions. As males kill more medium-to-large ungulates than females, on small reserves they’d reduce the large species used for game viewing more quickly, particularly in the case of giraffe.
As sub-adults have the most impact on giraffe and wildebeest, and dispersing sub-adult males kill a substantial number of prey, they should be translocated as early as possible, preferably at between two and three years of age. Paul says it’s important to understand the difference between prey selection when a two-male coalition is present, and when one of the males is removed and sub-adult males disperse from the pride, leaving a single male. “A single male has several advantages and might be enough to satisfy tourists. A coalition of pride males or sub-adults will kill significantly more animals than an individual male.”
The study showed the solitary pride male spent much more time with the females and shared most of their kills, so fewer kills may be made. A single male probably won’t kill large species such as giraffe while on his own, but will do so in a coalition or with the pride.
The single pride male spent very little time alone, indicating his reliance on females for food. It could also be that he spent more time than normal guarding the cubs from infanticidal males.Some studies suggest lionesses do most of the hunting, but males are also efficient hunters under certain circumstances, obtaining at least half their food from their own kills. As the male coalition spent almost half their time away from the pride, they also made many of their own kills. E-mail Paul Funston at [email protected] full research report appeared in the South African Journal of Wildlife Research, Volume 38, Number 1, 2008. |fw
