Animals despawning very quickly

I've been playing on peaceful so I'm not sure if this applies to hostile mobs as well but I've noticed that animals despawn extremely fast unless they've been tamed. For example I live on an island I found a chicken on my island but I didn't have a lead I went back to my base to get a lead (which is extremely close because I live on the same island) when I came back the chicken was gone. This is just one example it's happened plenty of times with various animals.