Density of Large Predators on Commercial Farmland in Ghanzi, Botswana

1. What they did

Large predators such as cheetahs, African wild dogs and brown hyaenas range widely and often live outside protected areas, on farmland. Botswana is a core country for cheetah and wild dog conservation, yet its national predator strategy relied on density figures from protected areas and on assumptions for farmland. This was the first study to estimate large predator densities on Botswana farmland.

The authors ran three spoor surveys on the Ghanzi commercial farmlands:

• Mixed farmland (March to June 2007): cattle farms and neighbouring game ranches east of Ghanzi town.
• Game ranches and cattle farms (February to July 2008): two surveys run at the same time west of Ghanzi, alternating between them each day.

Each survey area had two fixed transects along sand roads, kept as straight as possible to avoid counting the same animal twice. A San tracker with a predator biologist searched for spoor from a vehicle driven slowly (about 10 to 13 km/h) from sunrise until 11:30, when spoor is easiest to see. Every large predator spoor was identified and recorded with the date, a Global Positioning System (GPS) location and the number of animals. Only fresh spoor (less than 24 hours old) was used, and road sections disturbed by vehicles or rain in the previous 24 hours were left out. Where several tracks of one species were found on the same transect, the team judged whether they came from the same or a new animal, so that each animal was counted only once a day. Animals travelling together were counted individually.

The spoor counts were converted into densities with calibration equations from earlier studies of predator populations of known size, and the surveys were compared with chi-square tests.

2. What they found

Effort

• In total the transects were driven for 3535 km (1026 km mixed, 1269 km game, 1240 km cattle), covering 1337 km² of farmland.

Spoor found

• Cheetah, leopard, brown hyaena and wild dog spoor were found. The wild dog spoor was off the transects, so no wild dog density could be estimated. No lion or spotted hyaena spoor was found.
• Spoor counted: 38 cheetah, 7 leopard and 257 brown hyaena.

Densities (per 100 km², mean of the three surveys)

• Brown hyaena: 2.18 (range 1.82 to 2.38 across surveys). This is far higher than the earlier estimate of 0.01 to 0.1 per 100 km², and similar to the Kgalagadi Transfrontier Park and the Makgadikgadi Pans.
• Cheetah: 0.21 (range 0.00 to 0.58), similar to the presumed 0.15 to 0.56.
• Leopard: 0.10 (range 0.00 to 0.25), lower than the assumed 0.95 to 1.5, and in contrast to local landowners who believe leopards are abundant.

Differences between farm types

• Cheetah spoor: 23 on mixed farmland, 13 on game ranches and only 2 on cattle farms, a significant difference.
• Leopard spoor: 6 on game ranches, 1 on mixed farmland and none on cattle farms. This difference was also significant, but there were too few leopard spoor to meet the test’s assumptions.
• Brown hyaena spoor did not differ between the three areas. (The text and Table 1 give the hyaena counts per area in a different order.)

Removals of predators

• Two leopards were killed in the cattle study area in the three months before that survey, and one leopard was shot in the mixed farmland area during the survey.
• Ten cheetahs had been removed from the game ranch area between November 2006 and June 2007 because of conflict with people.

3. What they concluded

• Measured densities differed from the figures that had been assumed for Ghanzi farmland, showing the risk of managing predators on assumptions rather than surveys.
• Brown hyaenas occur evenly across cattle and game farms, probably because, as scavengers, they find food on all farm types. Their wide movements may make their spoor easier to find than the calibration allows for, so their density may be overestimated, but the area still appears important for them.
• Cheetahs and leopards were found mostly on game ranches and mixed farmland, most likely because of prey. Cattle farms had no stocked game, plus feral dogs and poaching, and generally fewer wild game were seen there. The lower cheetah density on game ranches than on mixed farmland may reflect the cheetah removals of the year before.
• The leopard result may be biased low because leopards were killed during and just before the surveys, which breaks the assumption of a closed population. Landowners’ belief that leopards are abundant may be inflated by the high level of conflict.
• The variable results for cheetahs and leopards show the need for repeated surveys, and for surveys in other farming areas to confirm the land use preference and its cause.

4. How tracking was or was not used

Tracking was the survey method. A San tracker found and identified large predator spoor along sand road transects from a slow-moving vehicle, aged it (only spoor less than 24 hours old was counted), counted the number of animals, and judged whether repeated tracks of one species on a transect belonged to the same or a different animal. No trailing is reported.

5. Tracker or observer certification

The trackers were tested on spoor identification before they were hired for this study; details of the test and results are not given. No certification is reported. The authors cite Stander et al. (1997) as having shown that San trackers can reliably and accurately identify and age spoor. The tracker or trackers are not named; Vivien Kent, Adam Camm and Service are thanked for their help with the survey.

6. Other technologies, skills or innovations

• GPS locations recorded for every predator spoor.
• Calibration equations (Stander 1998; Funston et al. 2010) that turn spoor density into animal density.

7. Implications for conservation (from the paper)

• Farmland remains important habitat for large predators, especially cheetahs, and Ghanzi appears important for brown hyaenas.
• Human–predator conflict on Ghanzi farmland is still high; better livestock management and community education are needed for people to live alongside predators.
• Leopards, the predator farmers rank as most problematic, may be scarcer on this farmland than thought. Monitoring of predator off-take and trophy size, together with future surveys, is needed to find population trends.
• Accurate density estimates are needed to target conservation and conflict work, set trophy hunting quotas and guide national predator policy.