Summary
Electric fences and other barriers to prevent elephants accessing farmland are increasingly important in Africa. In Laikipia District (9,723 km²), Kenya, crop raiding elephants are a problem. As a non-lethal crop protection measure, many types of elephant barriers have been erected over the last 30 years. In this study undertaken in Laikipia in 1992, information was collected on efficacy of existing fences, and an experimental fence was built along the Ol Ari Nyiro Ranch boundary (west Laikipia) to assess the importance of different fence design features in repelling elephants.
All electric fences in Laikipia were visited, and information collected on design, voltage, location, length, and the degree of elephant pressure (light, medium or heavy). Interviews were conducted with those responsible for maintenance to determine effectiveness, defined as:
i) low - fence broken by elephants at least once per week;
ii) medium - occasional fence breaks;
iii) high - not broken more than twice per year.
At Ol Ari Nyiro, 33 km of the ranch boundary was patrolled on at least 10 mornings per month to look for elephant footprints and fence breaks. Elephants were assumed to have crossed where there was fence damage and footprints indicated crossing of the fence line.
Comparison of 24 electric fences of various designs (categorised as simple or multi-strand) and three drystone walls (total fence length over 500 km) at about 23 localities showed that there was no clear relationship between fence effectiveness and design, construction or voltage.
Simple fences: Some simple fences (i.e. 1 or 2 wires carrying the current; voltage from < 2 kV to over 7 kV; little additional physical strength) worked well for long periods. Higher voltages tended to be more effective, but some successful fences had voltages of only 3-4 kV.
Multi-strand fences: Effectiveness of purpose built 2 m tall, high-specification fences(voltage usually over 6 kV, reinforced posts etc) varied. At one locality an 11-strand fence protecting wheat and maize crops from elephants proved successful; at Ol Ari Nyiro a fence of the same design was much less effective.
Drystone walls: Although these can be pushed over by elephants, at one ranch they were moderately effective, perhaps as there was ‘vigorous reaction’ to individuals that broke through.
In this study, the previous experience of elephants with electric fences in a particular locality, and shooting of fence-breaking individuals was considered more important than any fence design criteria.
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