Why do elephants raid crops?

Sampath Ekanayaka

Introduction
Large herbivores are key components of terrestrial biomes because of their relative abundance and pronounced influence on ecosystem functioning and habitat structure. To manage and conserve these species effectively, greater understanding of their resource requirements at varying spatial and temporal scales is fundamental.

The Asian elephant Elephas maximus is a species of ecological and cultural significance that has become endangered due to the rapid decline of populations in recent decades. Human–elephant conflict (HEC) causes a major threat to its survival in many parts of Asia, including Sri Lanka. The critical question for wildlife managers and ecologists is how elephant persistence can be ensured in agricultural landscapes in the face of expanding agriculture. Thus, a better understanding of the mechanisms and governing factors of crop raiding by elephants, should help wildlife managers recognize the problem and deal with it more effectively. Unfortunately, this information is significantly limited in Sri Lanka.

This study explores the relationship of elephant food habits and utilization of cultivated crops, considering raiding patterns throughout the year in a human dominated landscape of southeastern dry zone of Sri Lanka (SEDZ).

The main focus of the study was to assess whether crops were raided as an essential resource or as a preferred resource. It was hypothesized that, if crops were an essential resource; all elephants in an area will raid crops, raiding will occur throughout the year without any seasonal differences, and will involve both males and females equally. If crops were not an essential but a preferred resource only some animals in the area will raid crops, raiding would be more in the wet season, and raiding by male elephants would be more than by female herds.

Methods
To examine these hypotheses three data collection techniques were used; ground monitoring of crop damage, macroscopic dung analysis and micro histological analysis of plant fragments in dung. The field work for the study was conducted over a period of one year in four study areas.

Results
Ground monitoring of crop raiding in the four study sites indicated that there was significant differences between male and female elephants in raiding crops with males raiding much more than female herds. Raiding incidents showed a seasonal increase with higher raiding during the rainy season.

Macroscopic analysis of dung found crop seeds only in some dung piles. Crop seeds were found more commonly in male dung than in dung from female groups. There was a seasonal difference of crop seeds in dung with a higher frequency of dung piles with crop seeds during the wet season.

Micro-histological analysis of crop fragments in the dung found crop fragments in only some dung piles. Crop fragments were more common in dung of males than of female groups. Frequency of occurrence of crop fragments in dung was higher in the wet season.

Discussion
Therefore the different methods used in the study in varying spatial and temporal scales, provided similar findings, indicating that only some elephants raided crops, males raided more than females, raiding was seasonal and higher in the wet season. Thus I conclude that elephants in SEDZ Sri Lanka raid crops not as an essential but a preferred resource.

Therefore, conservation practices should focus on effective mitigation measures to prevent elephant damage, because resources within the ranges of elephants in SEDZ Sri Lanka are fairly stable and sufficient for their survival without consuming crops. Many elephants in the SEDZ Sri Lanka, including those in the study areas, have ranges outside protected areas. Therefore, if HEC can be mitigated successfully elephants can remain in these areas for the future. Management of elephants outside protected areas is important for the conservation of elephants in Sri Lanka.