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 and pulses (Deecke et al., 2000). The only occasion where transient orcas display significant amounts of vocal activity is when they are active on the surface or recently after a kill. The reasons for this reduction of noise could be due to many factors which can be seen in other species interactions and behaviour. Using ‘Tinbergen’s four questions’, I will explain what necessity for this behaviour and what the origins of the silent behaviour may have been. Tinbergen’s Four Questions
In 1963 Nikolaas Tinbergen published a paper “On aims and methods of ethology”. In this paper he discussed how he believed any question regarding animal behaviour should be broken down into four different questions. These four questions could be divided into two categories, evolutionary (ultimate) explanations and proximate explanations.
The evolutionary explanations, which refer to the population, include evolution or phylogenetic determinants and survival value or adaptive significance. The phylogenetic determinants refer to all evolutionary explanations which are not covered by adaptive significance. These may include random processes including mutation and changes in the environment which could have impacts on the population resulting in a specific behaviour adaptation. The adaptive significance closely follows Charles Darwin’s work on natural selection where it is explained that an animal’s form has been altered to function better in the habitat and resulting in a increase in fitness for the individual.
The proximate explanations are focused with dealing in terms of the individual as opposed to the population. The two different individual questions proposed by Tinbergen relate to causation and ontogeny. The causation for a display of behaviour relates to the mechanics of the body and which stimuli provides a cue for the animal to display this behaviour. Included in causation is control of hormones, motor control, central-nervous-system control and the ability to...
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