Abstract
Standardized measures of behavior can be powerful tools for assessing the impact of whale watching activities on natural populations of cetaceans. To determine the possible impact of tourism on dolphins between a period without whale watching (1989–1992) (T1) and a period with whale watching (2010–2020) (T2), we examined the changes in the rate of surface behaviors, the group size of long-time resident bottlenose dolphins living in the waters of the Humboldt Current off Chile, and for T2 alone, we compared these differences between two localities, the Punta de Choros and Chañaral de Aceituno coves. We observed a significant decrease in the group size of the resident population and in the frequency of surface events associated with the absence and presence of tourism. For T2, we observed significant differences for the frequency of surface events between the Chañaral de Aceituno and Punta de Choros coves and differences in the frequency of surface events at different hours of the day. This was associated with the number of vessels at the time of the encounter. In addition, we observed for T2 that the most observed instantaneous response of the dolphins to the presence of tourist vessels was to avoid the boats, while approaching the boats was the least observed response. The number of vessels present in each dolphin encounter was the most important variable for our model as it explains these differences. These results show that tourism vessels have a significant impact on dolphin behavior and sociability, while the same population of dolphins have different spatial and temporal responses to different impacts of tourism. Further studies are needed to establish whether changes in the rate of surface behaviors are associated with higher levels of stress in dolphins and with effects on their health and reproductive success in the long term.
Highlights
Over the last two decades, commercial boat-based whale watching has exponentially increased in the coastal areas of the world (Hoyt, 2001; Weir and Pierce, 2012; Hoyt and Parsons, 2014; Silva, 2015)
As for the results of the generalized linear model (GLM) analysis, we found a significant effect for the variables presence of tourism, cove, and years (p-value = 0.05), AM–PM, and presence and number of vessels (p-value < 0.0001)
There are numerous studies of bottlenose dolphins worldwide, there are a limited number of studies on the introduction of whale-watching vessels on the same individuals across time and space, as we describe here for the Chañaral de Aceituno and Punta de Choros coves
Summary
Over the last two decades, commercial boat-based whale watching has exponentially increased in the coastal areas of the world (Hoyt, 2001; Weir and Pierce, 2012; Hoyt and Parsons, 2014; Silva, 2015). In Chile, boat-based whale watching was first developed in the mid-1990s in Chañaral de Aceituno cove, and focused on a school of 40–45 bottlenose dolphins discovered in 1987 next to the west coast of Chañaral Island (29◦ 01 S, 71◦ 37 W) (González et al, 1989) These dolphins have been studied with photoidentification comparisons for about 30 years (González et al, 1989; Gibbons, 1992; Capella et al, 1999; Thomas, 2005; Molina, 2006; Cruz, 2011; Toro, 2011). The dolphins moved 28 km to the south coast of Choros Island (29◦ 15 S, 71◦ 33 W) (Capella et al, 1999; Sanino and Yáñez, 2001) and between 2000 and 2020 (Perez-Alvarez et al, 2018; Santos-Carvallo et al, 2018), the school has been seen at both sites, keeping the individual composition unchanged for a significant number of members (Thomas, 2005; Molina, 2006; Cruz, 2011)
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