I had tracked down a koalaphant and chased him into a medium sized pen, with only a 1 wall wide entrance for me. The koalaphant was safely trapped and I made sure he wasn’t going anywhere by watching him for a while. I then left the area for a day and when I came back, the pen was empty, with a trail of manure leading me to his location a few screens away. Maybe I should have made it bigger? If it helps I was in summer
Make a wood wall pen to house a single koalaphant and leave for a while.