W.H. Dudok van Heel, C. Kamminga and J.D. van der Toorn (1982)
An experiment in two-way communication in Orcinus orca L.
From: Aquatic Mammals 9(3): 69-82
Table of contents
Subject and training
Appendix I - Time dependent frequency stimuli
Appendix II - Considerations with respect to future research
This paper describes a behavioural experiment in which an Orca was encouraged to attempt elementary two-way communication, i.e. choosing between two objects, by spontaneously using a learned connection between a visual object and a corresponding auditory stimulus. Frequency-modulated signals, which were related to and within the range of the natural vocalisations of the animal, were used as stimuli. Two signals were made to represent action words, i.e. the verbs "take" and "bring", and the three other signals were used as the names of familiar objects. Initial results indicate the orca's ability to incorporate the stimulus signals into her vocalisations and to use them spontaneously in a meaningful context.
Information processing of complex vocalisations and echoes requires sophisticated development of the auditive parts of the brain. It is, indeed, well-known that odontocetes have impressive brains, mostly characterised by large size and intricacy. This fact has given rise to much speculation as to its significance. In many papers the assumption is made that the capacities of the odontocete brain surpasses the above requirements and enables the animals to communicate at the level of "language". The reasoning, on which these assumptions are based, is carefully exposed by Reysenbach De Haan (1966).
In this respect Lilly's attempts to achieve interspecific communication, between man and dolphin, are well-known. If there is any chance for such an interspecific communication, we postulate that it is with the killer whale (Orcinus orca L.), the most advanced species in the delphinid family as far as behaviour is concerned. We are supported in our opinion by the survey on trainability and behavioural reliability of eight captive species conducted by Defran and Pryor (in Herman, 1980). We base our opinion on behavioural observations of Gudrun, a female orca, with respect to the other dolphins with whom she had contact. Therefore, when this female killer whale was placed at our disposal, preparations for a communication experiment were set in motion.
Whatever definition of "language" is used, it will be obvious that object-naming forms much of the basis for practical use of language. The easiest way to incorporate this element in our experiment is by assigning and acoustical symbol to a visual object. However, this requires that the animal is able to associate an auditory stimulus with a visual stimulus. One can not take it for granted that the necessary cerebral interconnections (Geschwind, 1964) exist in the orca. If they do, however, the possibilities to continue the experiments beyond an elementary stage are far better. Therefore it is worth while to examine the object-naming abilities of the killer whale in this way first. The ultimate goal of this experiment was to learn whether a killer whale would be able not only to learn and understand the meaning of certain simple, basic sentences of two elements (acoustic commands), but also whether she would be able to use these sentences herself in a proper context to transfer a message to the experimentators.
The subject of this experiment was a female killer whale, Orcinus orca, from the North-Atlantic ocean, named Gudrun. She was caught in October 1976 off the southeast coast of Iceland and transported to the Dolfinarium in Harderwijk. At the moment of capture she was about 1½ years old, and weaned, 2.70 metres long and weighed 300 kilos. In October 1980 she was measured for the last time and was found to be 4.50 m long and to weigh approx. 1300 kilos. She was in the company of the orca who had been captured with her until May 1977, after which she spent the summer in the company of several. bottlenose dolphins, Tursiops truncatus, and even voluntarily took part in the show. In November 1977 she was briefly joined by six orcas, the last two of which left in May 1978. After the beginning of December 1977 she did not have direct contact anymore with other orcas, although she could hear the two orcas that still remained. There were no indications that she was in contact with these two. She was, however, continuously in the company of the dolphins, with whom she built up an intense social contact. She has always shown a great deal of interest in people, and has also needed much human attention, indeed, more than the dolphins. When she doesn't get enough attention, her motivation decreases rapidly and she appears to be bored, i.e. is not interested anymore. If the situation does not alter, she eventually refuses to cooperate, retires to a corner to rest or sleep. Offering food does not evoke interest.
As a result of the experiments with sound she became more and more active in the acoustic domain. We note that Gudrun, unlike the captive orca reported by Schevill and Watkins (1966), often used tonal vocalisations, as described by Steiner et al. (1979) from wild animals. This is most probably due to the fact that one of the authors, from the beginning of his acquaintance with Gudrun, consistently reacted to and encouraged vocalisations. This encouragement was greatly facilitated as his office was beside the pools occupied by Gudrun and visual and acoustical contact was always possible through large windows. When he did not answer familiar calls, she quickly developed the habit of using new sounds and/or behaviours to attract attention and establish contact anew.
The training with sound signals as they occurred within the experiment was completely new for Gudrun. Prior to this experiment she had only worked with hand gestures.
The training methods employed were the basic methods as used by the trainers at the Dolfinarium. In order to prevent strained relationships we decided not to use more sophisticated methods.
We note that the amount of fish that she got every day was never correlated with her motivation to perform the experiment.
The experiments always took place in Gudrun's own, 4.5 m deep, holding pool, which has a total capacity of 360 m3 and a water depth of 4 m (Fig. 1). The pool is only separated by a gate from the main pool of 1450 m3 and 4 m deep, which is occupied by the orca and the dolphins in free time during the day and all through the night.
In Fig. 1 the positions of the hydrophone are indicated by H1 to H4, and the places where the objects were presented are represented by Ol to O3. A1 to A3 indicate equipment locations.
Figure 1: Orca pool, the experimental site. Click here to load figure in current window or click here to load figure in a new window.
After making an initial inventory of the vocalisations made by Gudrun, we were able to classify the sounds into some 12 different contour groups. The signals used in the experiment were then designed on the basis of this classification. Consequently, we designed five types of stylised replicas of Gudrun's vocalisations, and assigned to them certain, meanings. Two of the signals represented action words or verbs, namely "take" (signal A) and give or "bring" (signal B).
Two toys with which Gudrun was already familiar were selected to serve as nouns: a lightweight dumbbell (signal C) and a fender (signal D) of the type used as buffers between boat and dock. A third noun, namely one signifying "large fish" (signal E) was added to her repertoire at a later stage.
In devising these signals, care was taken to see that they would fit well in the audiogram (Hall and Johnson, 1972).
Using frequency-modulated patterns as information carriers is preferable to using constant-tone stimuli due to the number of degrees of freedom that can be modified. Without going into detail, we offer a short description of the analysis and coding of the structural information content of the patterns used in our experiment in the appendix. The frequency modulation patterns of the signals are represented in Fig. 2. Note that the description of the tonal vocalisations as given by Steiner et al (1979) for the wild killer whale fits these signals.
Figure 2: Time-dependent frequency contours used as stimuli. Click here to load figure in current window or click here to load figure in a new window.
The equipment used in the experimental setup of the communication experiment is schematically indicated in Fig. 3. The envelope generator is the central part of the pattern generating system and contains the electronic circuits necessary to deliver a set of five control signals, which activates the function generator HP type 3310 A to obtain the time-dependent frequency contours.
These pattern contours are fed into the power amplifier B&K type 2713, to get an adaptation for the underwater transducer B&K type 8104. The slope of 12 dB of the transmitting voltage response of the 8l04 transducer is linearised in the envelope generator by a low-pass filter of -12 dB, resulting in a flat transmitting frequency response over the bandwidth of interest.
From phase 8 onwards the projected signals were monitored via another hydrophone and made audible on headphones.
Finally, a tape recorder was added to register the transmitted stimuli and corresponding responses of the orca. During the experiments a monitoring microphone was incorporated in the recording chain to register Gudrun's vocalisations above water.
Figure 3: Diagram of the stimulus generator. Click here to load figure in current window or click here to load figure in a new window.
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