Don’t bite the hand that feeds: assessing ecological impacts of provisioning ecotourism on an apex marine predator

Abstract

Summary1. There has been considerable debate over the past decade with respect to wildlife provisioning, especially resultant behavioural changes that may impact the ecological function of an apex predator. The controversy is exemplified by the shark diving industry, where major criticisms based on inference, anecdote and opinion stem from concerns of potential behaviourally mediated ecosystem effects because of ecotourism provisioning (aka 'chumming' or feeding).2. There is a general lack of empirical evidence to refute or support associated claims. The few studies that have investigated the behavioural impacts of shark provisioning ecotourism have generated conflicting conclusions, where the confidence in such results may suffer from a narrow spatial and temporal focus given the highly mobile nature of these predators. There is need for studies that examine the potential behavioural consequences of provisioning over ecologically relevant spatial and temporal scales. 3. To advance this debate, we conducted the first satellite telemetry study and movement analysis to explicitly examine the long-range migrations and habitat utilization of tiger sharks (Galeocerdo cuvier) originating in the Bahamas and Florida, two areas that differ significantly with regards to the presence ⁄ absence of provisioning ecotourism. 4. Satellite telemetry data rejected the behaviourally mediated effects of provisioning ecotourism at large spatial and temporal scales. In contrast, to the restricted activity space and movement that were hypothesized, geolocation data evidenced previously unknown long-distance migrations and habitat use for both tiger shark populations closely associated with areas of high biological productivity in the Gulf Stream and subtropical western Atlantic Ocean. We speculate that these areas are likely critically important for G. cuvier feeding forays and parturition. 5. We concluded that, in the light of potential conservation and public awareness benefits of ecotourism provisioning, this practice should not be dismissed out of hand by managers. Given the pressing need for improved understanding of the functional ecology of apex predators relative to human disturbance, empirical studies of different species sensitivities to disturbance should be used to guide best-practice ecotourism policies that maximize conservation goals.

Evaluating the landscape of fear between apex predatory sharks and mobile sea turtles across a large dynamic seascape

“…We found that tiger sharks spent more time at the surface during winter, potentially to enhance thermoregulation in warmer surface waters (Holland et al 1992). Moreover, during the winter, tiger shark core use areas were in the Bahamas, south of loggerhead turtle core use areas, probably such that tiger sharks could take advantage of warmer waters (Hammerschlag et al 2012a). Thus, the low turtle-shark overlap in winter could be a result of temperature primarily limiting their interactions.…”

“…Such an approach has previously been used by Hammerschlag et al (2012b). Moreover, home ranges for turtles and sharks are consistent between years (Hawkes et al 2011, Hammerschlag et al 2012a.…”

“…Their specialized teeth allow them to cut and take chunks out of large adult turtles (Witzell 1987). A subset of the tiger shark tracking data used in this study, including tag type and tagging methodology, was published in Hammerschlag et al (2012a).…”

“…Tiger sharks.-From January 2010 to August 2013, satellite tags were attached to 31 tiger sharks captured in Florida and the western Bahamas (for exact tagging locations, see Hammerschlag et al 2012a). Sharks ranged in size from 184 to 403 cm total length (283 6 58 cm, mean 6 SD).…”

Philopatry and Regional Connectivity of the Great Hammerhead Shark, Sphyrna mokarran in the U.S. and Bahamas

“…Although we were unable to confirm that presence at the provisioning site each visit resulted in food consumption, it was clear from the number of sharks detected at this site's receiver, and those in close proximity, this activity was concentrating great hammerheads to the west of South Bimini. However, like tiger and white sharks that are regularly provisioned in Grand Bahama and Australia, respectively (Hammerschlag et al, 2012;Bruce and Bradford, 2013), great hammerheads continued to make longdistance migrations and departed at different times during the winter season.…”