Fabian Ritter, Faculty of Biology, University of Bremen
Ute A. Ladner, Faculty of Psychology, University of Bremen
From September to December 1995, a study on the abundance of cetaceans off La Gomera (Canary Islands) and their interaction with whale-watching boats and swimmers was conducted. Observation platforms were the boats of CLUB DE MAR, Valle Gran Rey, organisers of commercial whale watching trips.
The behaviour sampling method was modified with the following objectives: not only the animals’ behaviour but also certain manoeuvres and actions of the boat were recorded during the three-minute sampling intervals. Group behaviour was categorised on the basis of existing ethograms – preliminary categories were established for those species where no ethograms had been defined so far. Special emphasis was given to the observation of interactive behaviour (which were defined), and the spatial relationship of boat and animals was recorded constantly. The encounters as a whole were categorised according to their intensity, as for example by the duration of the encounter or the affinity of the animals to the boats/swimmers. These categories are: (1) Avoidance, (2) Distant Encounter, 3) Close Encounter and 4) Intense Encounter. An Interaction Value was introduced to quantify the degree of interaction between men and cetaceans. Every species was given a value (I) and for three species (bottlenose dolphin, pilot whale and rough-toothed dolphin) several values (Is) could be found which were related to particular behavioural states.
During 82 whale-watching tours cetaceans were sighted 46 times, 8 different species were identified. It was found that different cetacean species showed divergent reactions to the approach of humans and that the same species may react in different ways depending on its behavioural state. 58 % of the sightings fall under categories (3) and (4) which confirms the »friendly image« of cetaceans.
During 26 encounters (=52%) people went into the water to swim with the animals. Here again different reactions of animals within their own species or of different species were observed. In 10 % of the in-water-encounters a real interaction (as defined) took place.
In this thesis the abundance and behaviour of the different species is discussed. Completely new results could be formulated for some of the less-known species (e.g. dense-beaked whales). The diversity of species in a relatively small area underlines the importance of the waters around La Gomera as habitat for cetaceans. The species will be characterised by their interactions with boats and swimmers. This makes it possible to submit specific rules for each species: every single species needs to be »treated« according to its peculiarities. This necessity is discussed and related to existing or missing regulations and laws. Possible rules for each species are proposed on the basis of the results.
Finally, the implications on whale-watching management as well as the urgent necessity of multidisciplinary approaches are pointed out. Specific steps to prevent an ecological counter-development are proposed. A process-orientated and holistic proceeding for management and scientific research will be pleaded for.
In line with the behavioural studies, interviews were made with the participants of whale-watching tours before and after the trip. The repertory-grid-method (used in the psychology of personal constructs) was applied, thus introducing this technique into a new context. The aim was to identify possible changes in the individuals’ attitudes during the encounters with cetaceans. This part of the study is the contents of the diploma thesis of Ute Ladner.