Curly was unable to adapt every well because in the book on page 14-15 it says Curly made a friendly advance to a husky dog the size of a full grown wolf, though not as half as large as she. There was no warning only a leap in like a lash, a metallic of teeth, a leap out equally swift, and Curly's face was ripped open from eye to jaw. She was unable to adapt because she was friendly and it got her killed.
Buck and Spitz fight
Buck was able to adapt to the law of club because on page 10 it states that a man with a club was a law-giver, a master to be obeyed, though not necessarily conciliated, and for that buck stopped attacking the man in the red sweater and lived.
Buck was able to adapt and learn how fights work in the law of fang because on page 15, it says; so that was the way. No fair play. Once down, that was the end of you. This helped Buck adapt because if he didn't know the way the law of fang was fought he would die if he got in a fight without knowing.
Buck was able to adapt and win the fight because in the book on page 40, it says; But Buck possessed a quality that made for greatness- imagination. He fought be instinct, but he could fight by head as well. So for that Buck was able to win and not fight crazily and blindly, while Spitz was fighting with anger which made him blind with rage.
Sol-lecks was able to adapt to who the leader / alpha was because when Buck won the fight he went to the lead position and Perault went to put Buck back in his spot on the sled, on page 42, it says the old dog did not like it, and showed plainly he was afraid of buck. This helped Sol-lecks because Buck wont fight Sol-lecks because he is not a threat to Bucks alpha position.