In his journal, Crusoe describes his first attempt at domesticating a goat in December of his first year on the island:
… by nursing it so long it grew tame, and fed upon the little
green at my door, and would not go away: This was the first
time that I entertain’d a thought of breeding up some tame
creatures, that I might have food when my powder and shot
was all spent. (Defoe 72)
After this first attempt, he does act on these thoughts, emanating from his necessity to fend for himself, after his supply of ammunition has depleted.