Looking at Non-Kosher Animals
Although it’s not against halachah to gaze at non-kosher animals or at pictures of them, the Kav Hayashar and other mussar works speak of the importance of guarding one’s eyes from looking at devarim temei’im (impure creatures). The Lubavitcher Rebbe spoke about this at length, especially concerning the impressionable minds of babies and children, adding that our generation in particular needs to train its eyes to see only positive and holy things.
Still, there are a number of exceptions: