Changes in diving behaviour and habitat use of provisioned whale sharks: implications for management

Abstract

Whale shark (Rhincodon typus) tourism is increasingly popular at predictable aggregations around the world, but only a few use provisioning to ensure close interactions. Understanding the effects of provisioning on the behaviour of this endangered species is critical to manage this growing industry. We recorded the diving behaviour and habitat use of juvenile whale sharks (n = 4) for a mean of 49.5 provisioned and 33.8 non-provisioned days using temperature-depth-recorders. We found that time spent at the surface (< 2 m) between 6 am and 1 pm increased ~ sixfold, while timing of deep dives shifted from 4–10 am to 10 am–2 pm, i.e. near or at the end of the provisioning activities. The shift might be related to a need to thermoregulate following a prolonged period of time in warmer water. These changes could have fitness implications for individuals frequently visiting the provisioning site. Based on recorded amount of time spent in warm waters and published Q10 values for ectotherms, we estimate a 7.2 ± 3.7% (range 1.3–17.8%) higher metabolic rate when sharks frequent the provisioning site. The observed behavioural, habitat use, and potential fitness shifts should be considered when developing guidelines for sustainable tourism, particularly in light of new provisioning sites developing elsewhere.

In-water observations highlight the effects of provisioning on whale shark behaviour at the world's largest whale shark tourism destination

“…Since there are more whale sharks in the interaction area during these months, the competition for feeding opportunities from the provisioning boats is higher, resulting in an overall reduction in the vertical or horizontal feeding behaviour observed. When in Oslob, the whale sharks generally spend the majority of their time at the surface because that is where the food is being provisioned [ 28 ]. Whale sharks have a need to thermoregulate as ectotherms [ 40 ], and the prolonged exposure to warmer waters [ 28 ], particularly during habagat when the water is warmer, might also explain their reduced predictability feeding from the food provisioned.…”

“…When in Oslob, the whale sharks generally spend the majority of their time at the surface because that is where the food is being provisioned [ 28 ]. Whale sharks have a need to thermoregulate as ectotherms [ 40 ], and the prolonged exposure to warmer waters [ 28 ], particularly during habagat when the water is warmer, might also explain their reduced predictability feeding from the food provisioned. The predictability of whale shark feeding behaviour in Oslob is therefore a reflection of the consistent provisioning of food, and as such, offers unique insights into their versatile nature.…”

“…This community-run site is active year-round, and although some tourist [26] and whale shark [23] seasonality is observed, the sharks are provisioned daily. While the activity offers an avenue for a tourism industry to flourish [26], there is evidence that the current tourism practices have impacts on the host species [27][28][29]. Behaviour modification is evident through significant differences in residency patterns between provisioned and non-provisioned individuals [21], with some individuals displaying year-round residency, while others are seasonal residents [23].…”

“…Provisioned individuals have also increased tolerance to human interactions and are less likely to display avoidance behaviour [ 22 ]. High presence of scars, and changes in diving behaviour and metabolic rate have also been reported in provisioned individuals [ 23 , 27 , 28 ]. Furthermore, poor tourist compliance, especially regarding minimum distance, is evident, which suggests high tourism pressure on the whale sharks [ 22 ].…”

“…Furthermore, poor tourist compliance, especially regarding minimum distance, is evident, which suggests high tourism pressure on the whale sharks [ 22 ]. These considerable impacts [ 21 – 23 , 27 , 28 ] on an endangered and nationally protected species should prompt stakeholders, such as the tour operators and the local government, to delineate limits of acceptable change or other management strategies.…”