Picture book – published prior to 1985
Rabbits in jeopardy. Little (young) rabbit wants to escape. Persuades old, previously resigned-to-his-fate rabbit to escape with him.  Big rabbit is scared out in the larger world, returns to his fate where they began.  Little rabbit goes on to other adventures alone.  Could be related to Watership Down – maybe a chapter of that turned into picture book.  Illustrations were beautiful, and NOT clips from the cartoon movie of that book.