Oviraptor was a small dinosaur, measuring about 6 feet long and a little over 3 feet tall. Gigantoraptor was a close relative, but, as its name suggests, it was big, at 26 feet in length and weighing more than a ton.
Gigantoraptor was created in 2007.
An oviraptor
I'm pretty sure, the gigantoraptor is many times the size of a grown man, but it depends on how big its mouth and throat is.
No
Oviraptors did, but scientists found a fossil of one sitting on a clutch of eggs which looked like the eggs from Protoceratops . They were actually Oviraptor eggs. The scientists thought that Oviraptor died when it found the eggs
Oviraptor, by scientific guess, lived around 3 years, maybe 5 if there are few predators. Oviraptor could well defend itself, though. It is probable they could live longer, but we may never know, due to the fact that Oviraptor is extinct.
on earth
Tyrannosaurs like Tarbosaurus and Alioramus, and dromaeosaurs like Velociraptor could have been natural predators of Oviraptor.
The dinosaur name oviraptor originally meant "egg thief", because of the fact that an oviraptor skeleton was discovered "stealing" eggs from another dinosaur's nest. But recent evidence actually shows that the oviraptor was just being a good mother and protecting her nest from egg thiefs, but most likely a sand storm.
Oviraptor probably would have run from predators. If it was desperate, it could have attacked by biting them with its beak or attacking with its claws.
about the same size as a ostirch
The Maiasaura and the Oviraptor did.