Communication
Elephants perceive their world very differently to us. They rely on hearing and smells much more than sight. We still know very little about how they communicate and exactly what they say.
So, we could be having a negative effect on them without even being aware of it. For example: our road and air traffic creates high volumes of infrasound that could disrupt elephant communication.
This is the study that has been undertaken by Graham Bowles:
The more we understand about elephants the more we appreciate the need to conserve them.
Graham fitting a recording collar to one of the study animals, Cathy