Tourism And Dolphin Disturbance
Human activities can directly or indirectly affect the behavior and reproductive success of other species by altering their habitat. To determine the exact impact, scientists must first develop a way to measure the effect of different environmental and social stimuli, which they call ‘agents’. This study tested an “agent-based model” for measuring the effect of boat-related activity on the behavior of bottlenose dolphins in Doubtful Sound, New Zealand.
The dolphins in Doubtful Sound are exposed to tourism boats used for wildlife watching trips, scenic cruises, and kayaking. Tourism is also believed to be a leading contributor to this populations’ current ‘critically endangered’ status by the IUCN. Past studies determined a link between tourism activities and how dolphins’ “budget” their time and energy. Based on this, the researchers assumed in this case that dolphins’ observable behavior stems from “unobservable motivational states” influenced by external factors, such as boat traffic, and internal needs, such as hunger.
As is often the case with computer models, this model was nuanced and incorporated complex submodels. The big picture, however, looked at three things: dolphins, boats, and grid cells. More than 60 dolphins were categorized by activity as well as physical, demographic, and motivational parameters (fear, hunger, inclination to socialize, and condition). Group size and dynamics were also analyzed. Boats were categorized by type, speed, frequency, and the nature of their trip. Lastly, grid cells were categorized by location, predation risk, and distance from other cells, as well as suitability for resting, socializing, and foraging.
On average, there were 8.8 dolphins per group. Their most common activities were traveling (51%), foraging (29%), socializing (16%), and resting (4%). They were exposed to boats an average of 11% of the time. Resting was most impacted by the presence of boats, with dolphins spending 10% more time resting under boat-free conditions. Motivational states for socialization and condition were fairly stable, but data for fear and hunger suggested “discontentment” due to the presence of boats, where activity varied depending on boat type. Over the long term, fear and hunger could affect dolphins’ activity budgets and eventually their individual (and group) health conditions.
Adjustments were made to make the model more “biologically realistic,” after the initial review revealed some shortages that impacted its outcome and reliability. Still, the researchers had some difficulty obtaining realistic results for all factors. They did find that dolphins spent a large proportion of their energy budgets on acquiring energy (eating) and that boats increased the motivation to spend energy.
Overall, the researchers concluded that their model successfully expanded upon a previous dolphin behavior model; furthermore, they concluded that agent-based models such as theirs could be used to depict animals’ behavioral response to human-caused disturbance.
They also acknowledged their shortcomings – namely, the use of group observations to define behavior. Because motivations are expected to vary among individuals, measuring in a group-context can erase individual activities. Visual observations were also subject to potential bias and misidentification.
Despite the model’s limitations, the results revealed that interactions with boats had a negative effect on dolphins in Doubtful Sound. This supports outcomes of previous studies, and indicates to animal advocates that ecotourism can have potential negative effects on wildlife populations. The good news is that, with some improvements to their models, human impact could be monitored and perhaps even mitigated.