Tinbergen’s Four Questions Regarding Orca Behaviour

Introduction The type of communication used to transmit information is closely related to the animal’s lifestyle and environment. This can be seen in most terrestrial mammals which are nocturnal so use olfactory and auditory which work as well in the dark as they do during the day. Visual communication would be relatively ineffective in this lifestyle. In contrast humans are diurnal and use primarily visual and auditory signals for communication, but miss many chemical cues which many other mammals base their behaviour upon. Marine mammals often need to communicate great distances, and the water does not support visual cues over great distance. This is why whales and dolphins use primarily auditory signals. Auditory signals can travel great distances and travel four and a half times faster in water than in air (Ford, 1984). Killer whales or Orca (Orcinus orca) are very social dolphins and live in pods often consisting of family members from between four up to fifty for residential whales while transient pods normally are only between two and five animals (Ford, 1989). These pods communicate with each other by use of echolocation clicks, tonal whistles and pulsed calls (Deecke et al., 2000). The three main noises have very different uses from each other. Clicks can either be produced as a single click or produced in rapid succession. Single clicks are generally used for navigation and collection of clicks and whistles are thought to be used for communication amongst members of the pod. Pulses are believed, with the assistance of single clicks, to be the method used by orcas to distinguish objects and discriminate prey (Barrett-Lennard et al., 1996). Residential orcas feed on fish, and can be frequently heard communicating with the clicks, whistles and calls because the fish have very poor hearing abilities (Wilson, 2002). The vocal behaviour of transient killer whales is quite different with the vocal communication consisting of occasional clicks