Due to their genetic engineering, gras had preprogrammed instincts to survive dangerous environments and predators; one directed them to seek elevated ground when daylight started to dim.
Gra flocks followed a dominant Alpha male, and his mate, Beta; in cases they had to split, a portion of the flock followed Beta.
They were genetically engineered to be hardier and have better survival instincts in the wilderness. Entire herds of frozen fertilized gra ova were sold, to be thawed out and grown by farmers on new worlds, along their manual. Farmers raised gra herds on Sulon and Ruusan, among others.
In 5 ABY a herder was on the road outside the western gate of the city on his way to the market next morning, when an Imperial force was returning to their base after twelve hours of patrol. A speeder bike traversed the flock, splitting it in half, Imperial commandos kicked the animals, which ran in circles, and an AT-ST stepped on one, crushing it. The unfortunate owner tried to put things in place. The chaos gave Kyle Katarn an opportunity to hijack the AT-ST and sneak into the city.
Another flock of gra was on a hilltop near Fuel City; as the Moldy Crow skimmed it, they scattered.
On Ruusan, Grif Grawley had a herd of 136 gra.
In the Dark Forces: Rebel Agent audio drama the gra herder is uncredited, although his voice resembles that of .