For years, I thought it was to try and eat Leaf Eaters. Now, I think it's the latter.
For one, they happen to move along the same path as the Gang of Five and also happen to come to them first and spend a good deal of time trying to get them.
One of them seems to have tried to bite Ducky even though she was on the nose of their mate. That seems so odd for a predator, though an irate parent who wants to avenge their kid wouldn't think rationally always.
I mean, it just seems their motivation is more related to protecting/avenging Chomper throughout the film. Yes, they may have tried to hunt at various times, but Chomper seems to be their primary motivation here. I doubt they would have bothered Ozzy and Strut otherwise.
As for why they would be trying to eat the Gang of Five, well, they're edible and it would be an added bonus to avenging their egg.
