A couple of book I read that really opened my eyes to animal intelligence:
Stories about animal intelligence in captivity:
https://www.goodreads.com/book/show/10476.The_Parrot_s_Lament_and_Other_True_Tales_of_Animal_Intrigue_Intelligence_and_Ingenuity
Stories about octopus in acquariums and in the wild:
https://www.goodreads.com/book/show/22609485-the-soul-of-an-octopus