Over 56 years, researchers at Brookfield Zoo Chicago's Sarasota Dolphin Research Program have watched the dolphins of Sarasota Bay develop an increasingly risky habit: hunting for scraps near fishing boats and begging food from humans. Now, a landmark study in Animal Behaviour reveals something unexpected—these human-linked foraging behaviors are reshaping the social bonds between dolphins themselves, especially during environmental crises.
The research, led by Kyra Bankhead of Oregon State University, used more than 20 years of detailed observational data to track how dolphins' social networks shifted between 1995 and 2012. Scientists observed the dolphins before, during, and after a period of intense red tides in the early 2000s—harmful algal blooms that depleted the fish species dolphins normally rely on, forcing them to search more widely and bringing them into closer contact with human fishing activities.
The pattern was striking: dolphins that engaged in what researchers call "human-centric foraging"—taking bait from fishing gear, scavenging discarded catch, or approaching humans for food—tended to spend more time with other dolphins using the same tactics. The proportion of dolphins adopting these risky behaviors more than tripled over the study period, rising from 12 percent before the intense red tide events to 22 percent during them and 41 percent afterward. That trend alone suggests these practices are spreading through the dolphin community like a learned behavior, passed along and reinforced through social connections.
What makes this finding particularly important is what it reveals about dolphins as learners. "This study shows that human activities can do more than change where dolphins feed or how they find food," Bankhead explained. "They can influence the social fabric of a dolphin community, especially when that community is already experiencing environmental stress." Katherine McHugh, deputy director of the Sarasota Dolphin Research Program, added crucial context: "From a human perspective, feeding or interacting with a dolphin may seem harmless or even helpful. But for dolphins, these interactions can have lasting consequences."
Those consequences are serious. Dolphins that rely on human food sources face boat strikes, entanglement in fishing gear, hooking, ingestion of gear, injury, reduced reproductive success, and death. The red tide events complicated the picture further. During and after these blooms, the relationship between human-centric foraging and social bonds temporarily weakened, likely because dolphins of all foraging styles aggregated around the remaining natural prey. But the continued rise in human-centric behaviors afterward suggests something worrying: as conditions stabilized, these risky tactics continued to spread and solidify within the social network.
The Sarasota Bay dolphins represent the world's longest-running study of a wild dolphin population, giving scientists an unusually clear window into how marine mammal behavior evolves across decades. As harmful algal blooms and other environmental disruptions become more frequent or severe along many coasts, the findings underscore a sobering reality: dolphins face pressure not just from environmental change or human activity in isolation, but from the overlapping, compounding effects of both. Understanding how these stressors interact—and how they reshape dolphin behavior and social life—may be crucial for protecting these intelligent, adaptable animals in an increasingly challenging ocean.