In traditional studies of animal communication, individual variability was sometimes considered less relevant than species specific aspects, mostly because the goal was the classifications of sounds in repertories. However, individual variability seems to have a significant role in signal function and evolution. In this paper, we analyse individual variation in the structure of aggressive vocalisations of male southern elephant seals and we compare sounds from our main study population, Sea Lion Island (Falkland Islands), with sounds recorded in the nearby population of the Valdés Peninsula (Patagonia, Argentina).