Helga Happ, head of the zoo in Klagenfurt, said the giant turtles, together since they were young, came to the facility from the Basel Zoo in Switzerland 36 years ago, the Austrian Times reported Monday.
"But for no reason that anyone can discover they seem to have fallen out; they just can't stand each other," Happ said.
She said the turtles, named BiBi and Poldi, had to be separated when Bibi bit off a chunk of her mate's shell.
"We have staff talking to and trying to engage the two in interacting, and we hope that they might find their harmony again," she said. "We were told that it's very rare that after so many years animals who are a pair will fall apart, but that's where we are. We hope, though, we can [achieve] a reconciliation."