Despite the fact that they occupy similar ecological niches, the social structure of Asian elephants differs from that of their African savannah counterparts. This is perhaps due to their differing habitats. It is important to understand this and grasp the diversity of strategies that these endangered species might be adopting to survive.
Since there have been many studies of the African savannah elephants since the 1970s and there have not been many of the Asian elephants until more recently, there is a tendency to believe that what holds good for the former also holds for the latter. However, this is not so, as evidenced by studies conducted by the members of the Evolutionary and Integrative Biology Unit of the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru.
Asian elephants, in general, do not move in mixed groups consisting of males and females. “From what we see, males use smell to track females. They also rove long distances when they are in musth to find females,” says T.N.C. Vidya from JNCASR, who led the studies, in an email to The Hindu .
When they do meet, males check females (and vice-versa sometimes) to probably assess fertility and possibly identity. “Rarely, this might lead to a mating. Sometimes, the male just feeds alongside the female herd for some time and then leaves,” she adds.
A study by the group, which has been published in Frontiers in Ecology and Evolution , looked at adult male associations. Male Asian elephants spent only about 12% of their time in all-male groups as compared to 30-60% of the time in African savannah elephants. There was also a constraint on the group size in the case of the former.
“This may be because of the differences in resource availability,” says P. Keerthipriya, the first author of the paper.
Further, in an African savannah elephant population, young males seemed to prefer old males possibly due to opportunities for social learning. This was contrary to what the group observed in Asian elephants.
The observations of the group can be summarised thus: Young males spent a greater proportion of time associating with females (in mixed-sex groups) than with other males (in all-male groups). For old males, these two proportions were similar. While males met at random in the presence of females, the behaviour when females were not present was different.
Old males preferentially associated with other old males, and old and young males met each other less than expected by chance. Young males met each other as expected by chance. There was no evidence that young males spent more time with old males relative to time they spent with other young males. They also did not preferentially initiate associations with older males.
Another important finding of the study is the restriction on male group size. The group had also found a similar restriction on female group size in Kabini. “This is important and suggests that the food distribution is such that it limits large groups of elephants from feeding together,” says Dr. Vidya.
The study documented 138 independent sightings of all-male groups during the study period. “There would be a lot more sightings if we included the non-independent sightings,” says Dr. Vidya.
The researchers had hypothesised two possibilities for adult male elephants getting together in groups – (i) Testing their strength in a relaxed setting against similarly sized and closely matched age-class peers and settling their dominance position, and (ii) young males preferentially associating with, and socially learning from, older males.
“We found no evidence for young males preferentially associating with older males, thus social learning from older males does not seem to play a big role in male associations in our study,” says Dr. Vidya.
In the study, elephants aged 15-30 years were classified as young and those above 30 years were classified as old. Characteristics such as shoulder height, body length, skull size, and skin folds were used to estimate the ages of the elephants.
“We used the semi-captive elephants near the study area, whose ages are known, as a reference while estimating the ages of the adults,” explains Ms. Keerthipriya.
The researchers used their field data from 2009-2014 based on observations made at the Nagarahole and Bandipur National Parks.
“We identified 96 adult males. In all, 83 of them were sighted when they were not in musth, and we used this in this study,” Ms. Keerthipriya clarifies.
