Simplify the following text for a Grade 10 native English-speaking person.
Original: It raced over the grassy plateaus and hills of Patagonia , catching small reptiles and mammals leaving larger prey to its far more massive relatives such as Brontornis .
Simplified: It raced over the grassy plateaus and hills of Patagonia , catching small reptiles and mammals leaving larger prey to its more massive relatives such as Brontornis .