In paragraph 4, the phrase “…they now thrash their bodies and twitch their limbs” most likely describes
Lê-se em: “They have had to change how they react behaviorally to [this new] predator…their limbs have even changed to be longer so they can run faster.”
“The research shows that, in areas rife [cheias] with fire ants, lizards have changed other defensive strategies. Rather than freezing to camouflage, they now thrash [mexem vigorosamente] their bodies and twitch [estremecem] their limbs before fleeing, much as a human would when attacked by a fire ant.”