Group dynamics of raiding elephants

When elephants move into agricultural areas at night, their group dynamics may be different from that seen during the day in the natural habitat. Adult Asian elephant bulls are predominantly solitary during their daytime movements in the wild. I noticed, however, a distinct tendency among bulls to associate with each other while raiding crop fields at night. While 93% of sightings of bulls in the wild were of solitary bulls, only 58% of bull raids were by solitary ones. A very significant 26% of raids were by two-bull groups, 13% by three-bull groups, and the rest by a four-bull group. In most cases, these were not chance associations arising from individual bulls converging independently on a particularly attractive crop field at night. Rather, the associations were formed prior to the bulls entering cultivation from the forest. The group size among raiding bulls, however, was significantly higher only during the second wet season (October-December), when the majority of farmers grew crops in their land. Since raiding involves taking a certain risk (with angry farmers), it is mutually advantageous for bulls to cooperate, rather than compete, when crops are available in plenty.

Bull associations during raiding have been reported from other regions in Asia and also in Africa. Widodo Ramono, in a personal communication, informs me that all-male groups are known to raid plantation crops in Sumatra. Raiding bull groups are known from Sri Lanka. In a study of elephant-human conflict along the western periphery of Malawi's Liwonde National Park, Roy Bhima found bulls raiding in groups of up to six animals. In the Sengwa region of Zimbabwe, where most of the crop raiding is by bull elephants, Ferrel Osborn once observed an all-male raiding group of 17 individuals aged from about 6 years to large adults.

The size of bull groups is a function of the elephant density, proportion and numbers of bulls in the population, predation pressure, and local social relationships. The larger bull groups are generally observed in regions with high population density and numbers of bulls. Other factors, such as human disturbance through hunting, may also serve to increase group size in elephants. On the other hand, selective hunting of male elephants for ivory, such as in southern India, also serves to reduce the numbers of bulls and decrease bull group sizes. Since my study of crop raiding in southern India during the early 1980s, a systematic reduction of the male population through ivory poaching reduced the incidence of bull groups raiding crops. This was reflected not only in my study area, but also elsewhere, such as in the Hosur Division, where Ramesh Kumar observed only solitary bulls raiding crops during 1989-1991.

When family groups raided crops, I did not observe any tendency for them to form larger groups compared to their grouping in the forest. Roy Bhima similarly observed that the group size of raiding herds matched the group sizes of herds in their natural habitat at Liwonde during the wet season.

A possible explanation is that family groups may not gain any extra advantage in facing threats from farmers by coalescing into even larger groups. Rather, this may actually reduce the efficiency of feeding in crop fields. Large family groups do enter cultivated fields; group sizes of 50-80 elephants, including families and adult bulls, are reported from West Bengal State in India. The point I am trying to make, however, is that the group sizes of raiding family groups may not necessarily be different from what one observes in the natural habitat. One exception I found was that mother-calf units rarely seemed to venture for raiding. This is understandable as the mother may not risk exposing a lone calf to danger. At the same time, I must stress that more information is needed from a range of elephant habitats on the group dynamics of raiders.

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