Katniss recognizes the strange creatures chasing Cato as mutations, hybrid animals engineered by the Capitol. These mutations look like giant wolves but can walk upright like humans.
“The boy took one look back as if checking that the coast was clear”
Cato runs to the big rock and Katniss follows, but she realizes Peeta can’t keep up because of his injured leg. Unable to help him from the ground, she climbs to the top of the rock and fires arrows at the approaching mutations, allowing Peeta to climb up just in time to escape them.