Animal memory is surpisingly poor. Conditioning however is different. Many will argue or doubt it but even dogs that have lived with a family for years will have their memories fade away but possibly not completely. My best dog was with me for a year and went away for six weeks for training. When I went to pick him up he did not recognize me visually. I walked right by him and the rat just glanced at me. But a few minutes after he got my scent he started to sniff the air and in about five minutes he remembered and jumped all over me! Some things condition animals quickly like fear, so if you hit a deer and he gets way they'll remember quickly. If you leave your scent for them to smell once they don't seem too worried. But if you visit them over a few days they seem to avoid that area. I can only guess that they figure a predator is lurking and hunting for them. They also may visit the area much later (like in the evening) when they can no longer pick up your sent. I think that is what makes deer nocturnal more than anything else. How long before they return? They may return right away to see if they can figure out what you are. Once they have figured you out they have started to patterned you before you patterned them! The more you let on about yourself the more you educate them, the more you condition them. Conditioning is realitively permanent. The more the scarely the education the faster and better they remember.