New paper on elephant vocalisations
Our study on individual variation in rumbles in wild adult male African elephants is out now in PeerJ.
Studies have shown that adult male savanna elephants are more social than we once thought, such as
Shifra Goldenberg's analysis that took into account musth, when the elephants have a surge of hormones and their behaviour changes a lot.
ABEC post-doc Derek Murphy showed that the older males in the Elephants Alive dataset have more stable network centrality (indicating important connections) than younger males over time. We measured associations based on sightings of males together.
My big question after that was: what if we are not capturing all the associations? If males can communicate over large distances with low frequency rumbles *and* have individually distinct rumbles once they have reached adult size, maybe they have long-distance associations.
Angela Stoeger and colleagues showed that in captive male African elephants, body size/age impacts the characteristics of rumbles, but additional variation still exists.
So we decided to record the adult males, who were of similar size, in the wild in South Africa for three years (ended up using data from 18 months), to see if we could detect individual variation even under field conditions whereby we couldn't approach the elephants closely.
We recorded collared and individually-identified elephants from the vehicle and were challenged by engine noise, aeroplanes landing, wind, electricity generators. For higher frequencies like birdsong, we could have tried to cut these out, but it's the low freqs we needed! Eventually we accumulated repeated rumble vocalisations required to test differences between five individuals. It doesn't sound like much, but it was the result of many hours in the field. Males don't vocalise as much as females and sometimes a 5 hr session would be rumble-free.
We found evidence for individual variation and it was stable over the study period. It's just one step, but potentially it's evidence that testing for responses to difference individual rumbles could be worthwhile, and perhaps ultimately expanding our understanding of groups.
The more we know about adult male social behaviour and changes across the life course, the better we can consider their needs. It's important when things like illegal and legal hunting and challenging interactions with humans take place and adult males are often at the centre.