ASPEN, Colo. -

Online petitioners are calling on the Aspen Art Museum to cancel an upcoming exhibit featuring three tortoises with iPads mounted on their backs, calling it animal abuse.

The exhibit by Cai Guo-Qiang (Tsai Gwo-Chang) called "Moving Ghost Town" and is set to open Saturday as part of the public grand opening of the town's new $45 million museum. The African Sulcata tortoises will roam around grass on the museum's roof deck garden. Each will have two iPads showing video of area ghost towns.

The museum says the tortoises were rescued from a breeder and that a veterinarian is overseeing their care, which includes a daily salad of mixed greens and vegetables. It says the iPads are on mounts attached with an epoxy used to attach tracking devices to wild animals.