Unfortunately, in some cases, loli is correct. Some never learn unless first hand experience gets them. Even then, they may not. Case example, Steve Irwin.
If you are asking when should one endeavor to teach children respect for animal defenses, no age is too soon.
Unfortunately, my daughter is a Steve Irwin. She has been bitten by two squirrels, some snakes, a praying mantis, um, thinking.
Both squirrels she was trying to help. One had its leg caught between crossed branches, and she thought it would appreciate a bare handed human coming to grab it. The other one was injured.
She was attacked by a wild turkey once, but all he did was kick snow at her. It was an early snow, and she thinks he was pissed about it.