Cost and efficiency of large mammal census techniques: comparison of methods for a participatory approach in a communal area, Zimbabwe

1. What they did

Wildlife counts are usually compared by how precise they are, but projects run by rural communities on small budgets also need to know what each method costs. In the Dande Communal Area of Zimbabwe’s Zambezi Valley, where people and wildlife share the land, a project supporting the CAMPFIRE programme (Communal Areas Management Programme for Indigenous Resources) needed a way for local people to monitor large mammals.

The researchers compared six methods of counting animals by sight (no tracks or signs), all for mammals over 200 g:

• Aerial census by the World Wildlife Fund (WWF), from a light aircraft, in 1997 and 1999.
• Day car counts from the back of a pick-up truck, with binoculars and a rangefinder, on 12 road transects (1997).
• Night car counts on the same roads, with a 1000-watt spotlight to pick up eyeshine (1997).
• Bicycle counts, one observer riding slowly along 10 road transects, about 30 times each (1999).
• Foot counts, one observer walking eighteen 1.8 km transects cut into the bush, once a month (1999).
• Water point counts, two observers in a tree blind watching for 24 hours around full moon, at 27 water points (1997).

Ground observers were local agents: Anti-Poaching Unit staff, the District Council’s Natural Resources Monitors and locally trained “Barefoot Biologists”. For each method, the researchers worked out how many human-hours and how many US dollars it took to survey one square kilometre, and how many animal sightings it produced per square kilometre covered.

2. What they found

Overall

• 10,368 animals of 27 species were counted. Common duiker, impala and kudu were seen most often.

Effort and cost

• Ground methods moved at very different speeds: 11.6 km/h by car, 5.5 km/h by bicycle and 1.3 km/h on foot.
• How far observers could see also differed: 46 m for night car counts, 56 m for day car counts, 79 m (effective strip width) for bicycles and 91 m on foot.
• Effort to survey one km² ranged from 0.07 human-hours (aerial) to 4.80 (foot). Among the ground transect methods, bicycle counts needed the least effort (1.32).
• Cost per km² ranged from US$0.18 (water points) to US$6.35 (night car counts). Bicycle counts cost US$1.46 and foot counts US$2.74, against US$4.54 for the aerial census and US$4.58 for day car counts.
• Water point counts were the cheapest, but only if one assumes the watched water points cover the whole area, which the authors call a very constraining assumption.

Detection

• Sightings per km² rose from day car counts (0.39) to night car counts (2.09), bicycle counts (2.79) and foot counts (5.83).
• At water points, observers had about one sighting every 10 hours, against one to two sightings an hour on bicycle, foot and night car counts.
• On the same roads at the same time of year, car counts did better in open woodland than in dense shrubland; foot counts did better in dense shrubland.
• Elephants were detected far more often by bicycle (1.15 per km²) and foot counts (1.96) than from the air (0.25). Buffalo showed the same pattern but varied more.
• Seeing one elephant cost about US$1 on bicycle and foot counts, against US$8 at water points, US$18 from the air, US$38 on night car counts and US$44 on day car counts.

3. What they concluded

• Simple, slow, cheap ground methods, especially bicycle counts and foot counts, gave the best value in this communal area, with its low animal numbers, thick bush and hunted, wary wildlife.
• Observers on foot or bicycle approach quietly, so they can get close to wary animals before they flee. Faster methods (cars, aircraft) miss animals in thick bush.
• Bicycle counts need good, safe roads; foot transects can go anywhere but need paths cut and marked. Both cover only a small area per observer, so they need many observers counting at the same time and may bring in observer bias. The authors suggest these methods suit small management areas.
• Where animal density is high, methods that cover large areas (aircraft and cars) may be better.
• The authors did not test how precise each method is from year to year, or how well each detects population change. Sampling designs differed between methods, so the cost comparisons are rough.

6. Other technologies, skills or innovations

• Bicycles as a cheap survey vehicle, with step counts to measure distance to animals.
• A simple way to measure how far observers could see: a person walked away from the road until out of sight, and the distance was measured with a rangefinder. At night, the person held a reflector to imitate eyeshine.
• The ground counts built on the local agents’ everyday patrols for anti-poaching and human–animal conflict. Observers needed only a few days of training to collect data on their own, and some later trained new observers.

7. Implications for conservation (from the paper)

• Cost matters as much as precision when choosing a monitoring method, especially for community-based programmes with little money. The extra cost of a better count should not outweigh what the better count is worth to management.
• A monitoring method in a community-based programme must be affordable, efficient and supported by local communities. Building counts into the duties of local agents is a step towards the community running its own monitoring over the long term.
• Census methods should be adapted to local conditions and facilities rather than following one standard method.