Chuck Jones always felt that you had to know how to draw animals in order to make your cartoon characters (human as well as other species) believable.  Here is a page from one of his sketchbooks (graphite on paper) filled with drawings and notes about primates.  His notes detail their behavioral habits as well as noting their physical characteristics.  He made good use of his study of primates in his television adaptation of Rudyard Kipling’s Jungle Book story “Mowgli’s Brothers.”