KERNERSVILLE, N.C. — As soon as the first robot arrived at a FedEx shipping hub in the heart of North Carolina tobacco country early last year, talk of pink slips was in the air.

Workers had been driving the “tuggers” that navigated large and irregular items across the vast concrete floor of the 630,000-square-foot freight depot since it opened in 2011.

Their initial robotic colleague drew a three-dimensional digital map of the place as it tugged freight around. A few months later, three other robots — nicknamed Lucky, Dusty and Ned in a nod to the movie “¡Three Amigos!” — arrived, using the digital map to get around on their own.

By March, they were joined by two others, Jefe and El Guapo. Horns honking and warning lights flashing, the autonomous vehicles snaked through the hub, next to about 20 tuggers that still needed humans behind the wheel.