Yeah, so this is two tortoises doing it. They're Madagascar radiated tortoises and they were radiating all over the place. The male would do his thing for a while and then get off and physically push the female around the enclosure for a while, then get back on. Not sure how long it was going on, but they were doing it when I got there and they were doing it when I left 5 minutes later.
Not really an animal you associate with stamina.
From Los Angeles Zoo, 2011