The question of exactly how many lions there are in the Kruger National Park (KNP) has been asked at various times over the years, with numbers of around 2,000 lions being considered to be reasonably accurate. Now, a new research project is attempting to tighten up this estimate, and data has already been gathered for the northern half of Kruger.
Preliminary results show that lion densities in the north of the park are as expected, with about five to six lions per 100km2 in the northern granites, and seven to eight lions per 100km2 in the northern basalts. The research will continue this winter, counting lions in the southern half of the park, which will increase the accuracy of the estimate of 1,700 to 2,200 lions in Kruger.
This is the first time a survey has been made of the lion densities in the north of the park, other than when a small section was surveyed in the northern plains to help discover why the numbers of roan antelope and other rare herbivores were declining in the area. Previous research carried out by Butch Smuts in the 1970s concentrated on the area south of the Olifants River.
Broadly speaking, lion density is related to the number of animals available for them to eat in a certain area, which depends on the amount of vegetation. This in turn generally depends on the rocks underlying the soil and the amount of rainfall.
Based on this, the project has divided the park into northern and southern granite and basalt areas. Lion densities are higher on the richer basaltic soils, and in the south of the park where there is higher rainfall. Led by Dr Paul Funston from the Tshwane University of Technology and Dr Sam Ferreira from the Conservation Ecology Research Unit at the University of Pretoria, the study is counting lions, looking at their relative ages, sexes and their general body condition.
Tshwane students Andrei Snyman and Hennie de Beer have been gathering the data over a period of time from June to December 2005. The data will then be compared with bovine tuberculosis prevalence in the park, to see if the disease is changing how long lions live, when they breed and their fertility in the different zones of the park.
Calling Stations
Adapting a technique first piloted in the 1970s, the researchers are attracting lions to calling stations, which consists of a loudspeaker set-up accompanied by researchers sitting inside a steel frame on the back of a bakkie. The loudspeaker broadcasts a recording of the distress call of a buffalo calf, played continuously for an hour, with the speakers turned every 15 minutes so the call covers a circular area. A shaded torch scans the area for shining eyes, alerting the researchers to the presence of lions.The calling station is then moved several times in the night, to cover the maximum possible area in the shortest time. Unfortunately, this technique does not work very well in the wet summer months, as fewer lions respond to the calls, so research has to be carried out in the dry season. Calling stations are set up in a regular pattern throughout the park, and figures on the number of lions called up will be extrapolated. This is based on a calibration exercise, where the team was based at Satara camp for six weeks.
Lions were found during the day by tourists or by luck when the researchers drove around at night. When lions were found, tests were carried out to find out what percentage of lions within a certain area would respond to a calling station. 170 lions were observed during this calibration survey.
Generally, the closer the lions are to a calling station, the more likely they are to turn up, within a four-kilometre radius. Females with cubs generally don't respond if they are more than one or two kilometres from the calling station, while all lion groups without cubs will come from further to investigate the sound effects.Taking Aim
Once animals turn up at the calling stations, two kinds of shots are taken at the lions - one with a laser range finder and one with a digital camera. Back in the lab, the photos can be analysed. The lion's height can be calculated by counting the number of pixels in the photo from the lion's shoulder to the ground. This is converted into an actual height estimate using a mathematical relationship based on the distance from the camera to the lion. The laser range finder tells the researcher how far the lion was from the camera when its photo was taken.
Lion shoulder heights are a well-known way of estimating ages. In the past, lions would have to be darted and physically measured, and sometimes marked to see if the same lions were turning up more than once.
This led to some obvious dangers, such as when researchers were measuring one set of drugged lions and other lions arrived on the scene. The lions can also be judged on their physical condition, with a mark of five being given to a lion that looks healthy with lots of muscle mass and tone, four to animals slightly off peak condition, three if the lion is a bit thin with some major bones starting to show through, two to a lion that has not eaten in weeks, and one to a lion that is on the verge of death.The condition scoring for the lions in the north of the park shows that they are generally in a good condition, with the average score of 149 lions being 4.3. In the central area, the average score of 170 lions was 4.6. The lowest score in the whole top half of the park was a two, and only one lion scored this. The average size of a group of lions coming to the calling stations was five lions. The largest pride found so far was in the Shangoni section, with 21 lions in the pride.
By looking at the relative ages of all the lions in a single group, the researchers can produce the equivalent of a country's population pyramid, with lions grouped into various age classes. This can give an estimate of the lion population growth rate, fertility and other interesting data.
Dr Funston says that the lion group size and population structure has been much as expected in the areas surveyed to date. So far, over 130 calling stations have been set up, and more than just lions have been attracted. Other than predators looking for a meal on a distressed buffalo calf, Dr Funston relates the story, "At the very first call-up station two hippos arrived and were very agitated by the buffalo calf distress calls.
They were aggressive to a pride of six lions that arrived, regularly charging the lions." He adds that in the north of the park, elephants are often a problem as they come "trumpeting and charging" out of the dark in response to the distress calls.
On one memorable evening, at the junction of the Timbavati and Orpen-Satara road, within six minutes of switching on the loudspeakers a cheetah arrived, followed by a bull elephant, a leopard and finally four lions, all turning up within 35 minutes.
Only on two nights calling were no lions seen. All the carnivores seen are being counted, and Dr Funston believes it will be possible to get population estimates for spotted hyena using the call-up method, provided they carry out a calibration run similar to that done for the lions, to check hyena responsiveness, call in distances and times to the call-up station.
The researchers will be back in the field with their lasers and cameras in late May, and will set up calling stations beginning at the base of the park, slowly making their way up to where they finished last year's survey. They are expecting to find 10-12 lions per 100 km2 in the southern granites and 12-15 lions per 100km2 in the southern basalts.
As this is the half of the park with the highest bovine tuberculosis prevalence in buffalo (one in three buffalo in the south of the park have visible BTB growths in their organs) and where the vets most often get reports of emaciated lions that are found to have advanced BTB on necropsy, many people will be eagerly waiting for the results of the survey.
The condition scoring for the lions in the north of the park shows that they are generally in a good condition, with the average score of 149 lions being 4.3. In the central area, the average score of 170 lions was 4.6. The lowest score in the whole top half of the park was a two, and only one lion scored this. The average size of a group of lions coming to the calling stations was five lions. The largest pride found so far was in the Shangoni section, with 21 lions in the pride.
By looking at the relative ages of all the lions in a single group, the researchers can produce the equivalent of a country's population pyramid, with lions grouped into various age classes. This can give an estimate of the lion population growth rate, fertility and other interesting data.
Dr Funston says that the lion group size and population structure has been much as expected in the areas surveyed to date. So far, over 130 calling stations have been set up, and more than just lions have been attracted.
Other than predators looking for a meal on a distressed buffalo calf, Dr Funston relates the story, "At the very first call-up station two hippos arrived and were very agitated by the buffalo calf distress calls. They were aggressive to a pride of six lions that arrived, regularly charging the lions."
He adds that in the north of the park, elephants are often a problem as they come "trumpeting and charging" out of the dark in response to the distress calls. On one memorable evening, at the junction of the Timbavati and Orpen-Satara road, within six minutes of switching on the loudspeakers a cheetah arrived, followed by a bull elephant, a leopard and finally four lions, all turning up within 35 minutes. Only on two nights calling were no lions seen.
All the carnivores seen are being counted, and Dr Funston believes it will be possible to get population estimates for spotted hyena using the call-up method, provided they carry out a calibration run similar to that done for the lions, to check hyena responsiveness, call in distances and times to the call-up station.
The researchers will be back in the field with their lasers and cameras in late May, and will set up calling stations beginning at the base of the park, slowly making their way up to where they finished last year' survey. They are expecting to find 10-12 lions per 100 km2 in the southern granites and 12-15 lions per 100km2 in the southern basalts.
As this is the half of the park with the highest bovine tuberculosis prevalence in buffalo (one in three buffalo in the south of the park have visible BTB growths in their organs) and where the vets most often get reports of emaciated lions that are found to have advanced BTB on necropsy, many people will be eagerly waiting for the results of the survey.
