susceptibility to elephant crop raiding
Farmers in Africa face real challenges in preventing elephants from entering their farms and limiting crop damage during successful raids. Elephant crop raiding is often localized but can be catastrophic where it does occur (Naughton-Treves 1998; Sam, Haziel & Barnes 2002), with many farms suffering habitual raiding. This is in part because of location and physical factors; patterns of landscape variability and the seasonal movement of elephants determine the location of human–elephant conflict zones (Osborn & Parker 2003a; Sitati et al. 2003), and farm-scale variation in physical attributes may also play a part in determining the likelihood of elephant incursions. This may be why, in our study, previously raided farms were more likely to be raided again. However, elephants respond to risk as well as opportunity (Sukumar & Gadgil 1988), and the evidence from this study suggests that increasing human effort can reduce crop raiding even where physical factors and geography render farms more susceptible. Of particular importance are (i) early detection of elephants prior to their entry into a farm, (ii) increased guarding effort and (iii) use of active deterrents such as fire.
Investment in human resources appeared to be a significant factor in preventing crop raiding. However, the high degree of collinearity between guarding effort and farm size in our data permit an alternative explanation, namely that elephants were raiding larger farms because of greater availability of crops, as opposed to lower guarding effort. Indeed, broader-scale spatial analyses suggest that crop raiding is more likely where the proportion of cultivated land is greater (Sitati et al. 2003). However, three pieces of evidence support our conclusion that guarding effort is an important element of mitigation. First, a higher density of guards per farm increased the likelihood that elephants were detected, enabling deterrents to be applied. Secondly, the importance of guards actively patrolling was highlighted in the comparative analysis. In farms where houses were close to fields, there was a greater temptation for those guarding fields to retreat inside during the night, thereby reducing vigilance and patrol effort. In other areas farmers spend the night in makeshift huts within fields to increase their chances of detecting elephants and responding rapidly, but this was not generally the case in Transmara until the second phase of this study when watchtowers were erected within or adjacent to fields. Finally, evidence from field trials conducted in the second phase of the study revealed that applying increased vigilance and guarding effort to habitually raided farms did result in elephants being repelled.
Active methods to scare away elephants, such as burning fires and banging tins and drums, increased farmers’ ability to prevent raiding. Noise and light will deter elephants from entering a field but only if they are loud and bright. Less forceful methods, such as shouting or using battery-powered torches, appeared less successful. Our methodology did not capture information on the intensity of shouting, but if this were greater, and the elephants in question more naive to farmers’ efforts to defend their crops, then more success might be likely. However, farmers in this study site and elsewhere complain that elephants become used to such hollow threats and no longer fear them, so that stronger deterrents are needed.
Passive barrier methods were largely ineffective, as elephants were easily able to break through them. Larger farms appeared to invest more heavily in ‘improved’ barrier methods comprising wooden post and barbed wire fences at the expense of guarding effort, which actually declined as farm size increased (Fig. 1). This was doubly bad for large farms, as weak guarding effort and barriers both increased the risk of crop raiding (Table 1). There are two possible explanations for this additive effect of barriers. Elephants may have associated the presence of such barriers with worthwhile rewards within, and therefore targeted farms with such barriers. More likely, however, is that farmers with such barriers, besides having fewer guards overall, were more complacent about actively guarding fields and so did not detect elephants soon enough to prevent them entering fields.
Barriers are popular with communities because they may be of use against smaller crop pests such as zebra Equus burchelli Gray, and with donors because they represent a tangible and potentially long-term capital expense. Barriers alone are most effective if they are electrified and totally enclose an area of cultivation (O’Connell-Rodwell et al. 2000). They do, however, require significant resources for recurrent maintenance. For most farmers, therefore, investment in guarding is likely to be a better option.
Once elephants were within a field, there was little that could be done to reduce the damage caused. Both the proportional and actual amount of damage per incident were relatively high in Transmara compared with other sites with equivalent data elsewhere in Africa, such as Kibale, Uganda and the Red Volta area of Ghana (Naughton-Treves 1998; Sam, Haziel & Barnes 2002). This may be because elephants in Transmara do not forage from a protected area but exist in an unprotected farm–forest mosaic, and so may be more used to human presence and less easily displaced from fields. Counter-intuitively, the application of most active mitigation methods correlated with greater proportional and actual crop damage (Tables 2 and 3). This may be because such methods caused elephants to panic and thus damage more of the area of a field in their attempts to escape. Alternatively, it may be because such methods were deployed on some farms once elephants were already causing damage (Naughton-Treves 1998). This would confound any assessment of the effectiveness of guarding. Equally, it could be that the efforts farmers took to chase elephants out of their fields were not sufficiently strong to have an effect. Results from Zimbabwe, where guarding effort during crop raiding was experimentally manipulated, found that increased levels of sustained and varied harassment did reduce the amount of time elephants spent within fields, although substantial crop damage still took place (Osborn 2002). Clearly, early warning and the active deployment of deterrents before elephants gain entry to fields is critical to reducing conflict.
mitigating crop raiding
This study used a comparative analysis to develop a model of susceptibility to crop raiding that was subsequently tested in field manipulation trials that resulted in reduced crop raiding by elephants. Although the research was small-scale and short-term, the results are unequivocal and demonstrate the value of evidence-based approaches to conservation problems (Sutherland et al. 2004). Few such studies currently exist. Equally, although the parameters of the model may be specific to the Transmara scenario, the broad findings are likely to be applicable elsewhere. The methodology is easily transferable to other sites to verify this.
Moreover, the participatory nature of the study enhanced its demonstration effect on local farmers. This is important because, despite the relatively intuitive findings, there is a lack of confidence in local mitigation methods and many farms remain insufficiently guarded against elephants. The results of this study reveal that enhanced early warning and other methods can work in the short term. However, many farmers fear that the success of such methods may be eroded over time by habituation (Bell 1984; Tchamba 1996). The fact that previously raided farms were more likely to be raided again may reflect a growing familiarity with commonly used mitigation methods. Therefore, a shifting combination of methods may succeed for longer as it will give elephants less chance to habituate. In that light, the development of novel, cost-effective methods, such as chilli essence (from Capsicum spp.), that farmers can use in combination with traditional methods is important (Osborn 2002). Moreover, extended trials in a range of high conflict zones will be required to validate fully such methods and demonstrate more broadly their utility to farmers. Extended trials are currently taking place within Transmara District, and are soon to be exported to other human–elephant conflict zones in Africa and Asia. The exchange of information between farmers in different areas using different mitigation methods will maximize both the spread of useful methods and the variety of methods employed in each area.
Besides a lack of confidence among local farmers, efforts to reduce crop losses to elephants incurs a significant array of additional costs. The direct and opportunity costs of investing in guarding and mitigation materials place such farmers at a commercial disadvantage compared with those living without the threat of elephants, and is particularly problematic for subsistence communities. Moreover, pitting human against elephant in this way is an inherently risky strategy as elephants can become aggressive when provoked (Bell 1984). For such large and unpredictable animals, the perceived risk of injury may greatly outweigh the actual risk (Naughton-Treves, Treves & Rose 2000). This psychological cost is equally if not more significant, and only serves to decrease local tolerance towards elephants. Besides the testing and demonstration of effective solutions, there may be a need to provide assistance to, or develop incentives for, poor farmers to invest in conflict mitigation. Such inputs are already improving local attitudes towards elephants in Transmara District (Kanton 2004) and so may represent a worthwhile investment.