When coastal waters are disturbed by the construction of a new bridge or a jetty, dolphins are able to adapt by altering feeding patterns.
According to a new study, published Thursday in the journal Frontiers in Marine Science, bottlenose dolphins move their feeding locations and shift the timing of feedings to avoid construction activity.
However, the impacts of construction may keep dolphin populations out of disturbed areas long after the project is completed.
In the United States, large swaths of the coastline host human development and are subject to a variety of human activities.
These areas also regularly feature construction, some of which require dredging and pile driving, two of the most severe forms of anthropogenic disturbance.
Many fish and marine mammal species rely on sound to navigate and hunt for prey.
Dredging and pile driving produce large amounts of noise pollution, in addition to churning up large amounts of sediment, impairing visibility.
For the new study, researcher Anne Weaver, an animal behaviorist and dolphin expert, observed the effects of bridge construction on a group of bottlenose dolphins living along Florida's Gulf Coast.
Weaver monitored the timing and locations of feedings among dolphins living near John's Pass, a narrow tidal inlet linking the Gulf of Mexico and the Intracoastal Waterway.
Weaver regularly collected data for 11 years — before, during and after the two-phase, five-year project.
During field observations, Weaver noted whether dolphins were present, their abundance and their behavior.
The data showed dolphins stopped feeding in John's Pass, where the bridge was being erected, relocating feeding locations outside the construction zone.
Though the dolphins remained present in the inlet, their numbers were reduced and the mammals stopped congregating and socializing. Five years after construction, the dolphins had still not returned to their previous patterns.
Weaver also noted that dolphins in the area altered feeding times to avoid the noise pollution.
By the second phase of the project, the dolphins had learned the times of day when construction activity and noise pollution was minimized. After construction was complete, the dolphins slowly returned to a more normal feeding schedule.
"Adaptation may also have been related in part to the way construction was managed," Weaver said in a news release. "This two-phase exposure to construction may have allowed the dolphins to become familiar with construction in the first phase and perhaps enabled them to adapt a 'new normal' during the second phase."
"These results provide a two-sided key to managing future coastal construction projects by mandating the following conservation policies," Weaver said.
"First, study the wildlife before construction begins to learn their habits. Second, apply that knowledge: Plan coastal construction activities accordingly to give them a chance to adapt and help the dolphins maintain their historic habits as much as possible," she said.
