How does "Sir Gawain and the Green Knight" juxtapose the Lady Bertilak with the three hunted animals?
Let us remember that there is a direct correlation between the test that Gawain faces and the hunts that Bertilak embarks upon. The test is first set up the night before Bertilak goes on his first hunt, and over the next three days, Bertilak will give what he kills to Gawain, who must, because of the chivalric code, return it with a gift of his own.
The first day, does (female deer) are hunted, which of course are juxtaposed very closely to the position of Gawain himself. Gawain at this point is courteous and has not resisted his captivity. We are told that the deer are being "driven to the valleys," which is similar to the way in which Gawain is being trapped in his room by Lady Bertilak, who refers to Gawain as her "captive knight."
On the second day, a large boar is hunted, which attacks violenty when cornered by Bertilak and his men. This again parallels the experience of Gawain, as when Lady Bertilak enters his chamber, he greets her at once, in a much more aggressive and confrontational boar-like way rather than feigning sleep like he did the day before.
The third day features the fox who conceals himself from the hunters and uses every act of animal ingenuity and cunning to escape. However, like Gawain, he is eventually hunted down and his hide is removed. Consider how this is paralleled with the public shaming of Gawain in the Green Chapel at the end of the story. To reinforce this comparison, Lady Bertilak convinces Gawain to accept a girdle and is rewarded for accepting it by the fox's hide that very night.
At each stage therefore, we can see that the hunt is juxtaposed very clearly with the experience of Gawain as he is "hunted" by the resourceful and determined Lady Bertilak. Both Bertilak and Lady Bertilak employ similar methods to entrap their prey.