Although feeding dolphins in Florida is illegal, Beggar had been cadging food off boats for 20 years in the Intracoastal Waterway near Nokomis, the Tampa Bay Times reported Tuesday.
His underweight, decomposing body was found Friday in south Sarasota County, the newspaper said.
Beggar was known for approaching any passing boat and sticking his head out of the water in search of food handouts.
Marine scientists say they could not pinpoint the exact cause of death, but suggested Beggar's close association with humans apparently damaged his health.
Broken ribs and scars from old wounds suggested numerous encounters with boat propellers, they said, while fish hooks were found in his stomach.
"All of these things indicate that he was spending more time attempting to get food from humans than foraging on his own," said Gretchen Lovewell, the manager of the Mote Marine Laboratory Stranding Investigations Program, who performed the necropsy.
Beggar was between 25 and 35 years old, researchers estimated.