Speculate as to why the aleuts never again returned to the island of the blue dolphins.

This question can be answered in a number of different ways.  It could be argued that the Aleuts did not feel it necessary to return to the island after they killed all of the otters.  On the other hand, given that Karana befriends Tutok and Rontu - young Aleutians who do not accept of believe in the violence that their tribe takes part in - it could be argued that the younger, upcoming generation of Aleutians are lead to change their ways due to Karana's actions.