Interacting with wildlife tourism increases activity of white sharks

Abstract

Anthropogenic activities are dramatically changing marine ecosystems. Wildlife tourism is one of the fastest growing sectors of the tourism industry and has the potential to modify the natural environment and behaviour of the species it targets. Here, we used a novel method to assess the effects of wildlife tourism on the activity of white sharks (Carcharodon carcharias). High frequency three-axis acceleration loggers were deployed on ten white sharks for a total of ~9 days. A combination of multivariate and univariate analysis revealed that the increased number of strong accelerations and vertical movements when sharks are interacting with cage-diving operators result in an overall dynamic body acceleration (ODBA) ~61% higher compared with other times when sharks are present in the area where cage-diving occurs. Since ODBA is considered a proxy of metabolic rate, interacting with cage-divers is probably more costly than are normal behaviours of white sharks at the Neptune Islands. However, the overall impact of cage-diving might be small if interactions with individual sharks are infrequent. This study suggests wildlife tourism changes the instantaneous activity levels of white sharks, and calls for an understanding of the frequency of shark-tourism interactions to appreciate the net impact of ecotourism on this species' fitness.

Keywords: Carcharodon carcharias; accelerometry; ecotourism; energy budget; metabolic rate.

Figure 1:

Location of the Neptune Islands Group Marine Park and areas where cage-diving operators typically anchor at the North Neptune Islands Group (red ellipses).

Figure 2:

Example of an accelerometer package deployed on a white shark (Carcharodon carcharias).

Figure 3:

Non-metric multidimensional scaling (nMDS) plot based on Euclidean distances, showing (N = 29) contexts from 10 white sharks (Carcharodon carcharias). Contexts (symbols) that are more similar to one another are ordinated closer together. Stress = 0.02.

Figure 4:

Plots showing the effects of different contexts on white shark activity metrics. Median values are indicated by the bold horizontal bar; the length of the box is the inter-quartile range; whiskers represents 1.5 inter-quartile range; circles are outliers; and asterisks are extreme values.