Scientists suspect that Giganotosaurus hunted in packs. However I find that such a large creature hunting in packs quite unlikely. Even if it did the pack wouldn't be able to stay in area for too long or else they would unbalance the habitat because such large creatures must consume about 800lbs of food a day each. What is your opinion of such a large creature hunting in packs?
from Scott, age 14, Columbia, Richland, USA; July 9, 2001

TOM: The evidence that Giganotosaurus (actually not Giganotosaurus proper, but a closely related and somewhat younger form) hunted in packs comes from a site in Argentina. Several of these dinosaurs, of different age groups, were found buried together from the same event. No other dinosaur remains were found with them. This suggests that at least part of the time these dinosaurs did gather together, although whether these were true hunting packs or some other association is hard to say for certain.

I suspect that these packs, if that's what they are, must have operated over a huge range. However, the Cenomanian (earliest part of the Late Cretaceous Epoch), when these dinosaurs lived, was a time of very high temperatures and high carbon dioxide levels, which suggests a lot of plant activity, which suggests a lot of food for many plant eaters. This may have helped support the carnosaur population.

(I think you may have overestimated the food requirements of the theropods, incidentally. Using the equations that Mike Brett-Surman and Jim Farlow developed in The Complete Dinosaur, I find that a 7.5 ton theropod would only need about 81 kg/day of meat to live).

Some tyrannosaurs (Tyrannosaurus rex and Albertosaurus sarcophagus) have been found in similar groups, so it may be that they also gathered together.