African elephants have a flexible social and hiking behavior. In order to keep in touch, the gray giants produce very deep sounds, some of which lie below the human hearing threshold in the so-called infrared range. With the help of these infrasonic sounds, which are called "rumbles", elephants can communicate widely over great distances. This "secret language" provides an important information and communication channel for the socially living pachyderms. In the context of a project funded by the FWF, Angela Stöger and Anton Baotic are concerned with the behavior and communication of the relatively little explored elephant bulls, specifically in the "Addo Elephant National Park" in South Africa. They use playback experiments to explore the sensory and cognitive abilities of the male pachyderms. [more]