I needed a word that didn't explicitly tell the viewer what to look for. "Prey" or "Predator" would have made it too obvious, and I certainly didn't want to say "find the fox" or "find the animal".

I used the word "threat" because the act of finding the fox in the image represents our survival mechanisms being put to use, even if the animal is not a real threat, if you heard rustling in the foliage, the first instinct is to assume it's a threat.