Effects of tourism operations on the behavioural patterns of dolphin populations off the Azores with particular emphasis on the common dolphin ( Delphinus delphis )

Objectivo

The cetacean diversity observed in the Azores accounts for around 30% of currently known cetacean species. This high level of diversity has supported the development of commercial recreational activities such as whale watching and swim-with-dolphin programs. Both operations are regulated by law, which is currently under revision. In order to produce effective management strategies and avoid detrimental impacts, an assessment of the populations targeted by such activities is imperative. This becomes even more critical in light of the poor, often absent, baseline information currently available for local populations. The short-beaked common dolphins (Delphinus delphis) is the most common species, encountered year-round, and thus is one of the most representative species in this industry. Other dolphin species such as the bottlenose (Tursiops truncatus) and the Atlantic spotted dolphin (Stenella frontalis) are also exposed to swim-with programs. Hence, the objectives of the present study are to (1) describe for the first time the normal undisturbed behavioural patterns of common dolphins, (2) measure behavioural changes resulting from whale watching (common dolphins), (3) investigate swimming-with-dolphins interactions (common, bottlenose and Atlantic spotted dolphins) and (4) provide suggestions for guidelines, especially the swim-with operations, which are considered more invasive and thus potentially have a greater impact.

Focal group follows and predominant group activity sampling was undertaken between 2013 and 2014 from a land-base station in São Miguel Island. The activity budget of common dolphins revealed that they use the area primarily for foraging and traveling. Travelling peaked during the summer months; foraging decreased around midday. Larger groups were observed during summer and during foraging. Common dolphins showed a variety of surface active behaviours such as breaches, porpoising, head and tail slaps when engaged in foraging, traveling and socializing, suggesting different functions of these behaviors depending on the context they are used in.

Common dolphins were found interacting with tour boats during 10% of their time, a relatively low percentage when compared to other common dolphin populations such as those in New Zealand. Nonetheless interaction with tourism activities revealed changes in the behavioural patterns of common dolphins, with less time spent foraging and more time socializing. The time to resume a preceding activity after a tour boat interaction was also affected, with dolphins taking longer to restart foraging and less time to re-engage in socializing. Similarly, the average foraging bout length was shorter in the presence of tour boats compared with control scenarios.

Boat-based sampling was conducted between 2013 and 2015 to assess the response of dolphin groups to swim-with programs. The three dolphin species observed showed mainly neutral or avoidance responses. The bottlenose dolphins showed higher neutral responses than the common dolphins, and Atlantic spotted dolphins tended to avoid and approach more often than the other two species, suggesting a higher variability in response to human activities. Among the three main strategies used to approach dolphin groups, intersecting the dolphin’s path was the most disruptive method and more likely to result in avoidance behavior and in shorter swimmer-dolphin interactions. Irrespective of species, the duration of swimmer-dolphin encounters was also shorter when dolphins were resting or traveling and when they were in small groups. Compliance with legal regulations was generally good except in the number of swim attempts per dolphin group. This averaged six whereas a maximum of only three attempts is allowed. Suggestions to improve the current legislation include not intersecting the path of dolphins when approaching groups, and avoiding swimming with resting groups and with groups which include new-borns, due to their particularly vulnerable nature.

Behavioral changes and the high avoidance responses detected in the three target species suggest that, although cetacean tourism in the Azores is still far from being considered a large industry, disruptive effects are already occurring. The likely increase in the number of tourists requires effective management that takes into account the importance of the area for dolphins and their susceptibility to tourism interactions. Enhancing monitoring efforts is also fundamental to clarifying site fidelity patterns and hence the potential for cumulative impact.