Option 1 -> The author actually got into trouble by NOT following instructions to stay on the machaan.
Option 2 -> Defying orders to leave the machaan early nearly led to a dangerous encounter with the elephant.
Option 3 -> Setting off on foot is what created the dangerous situation with the mad elephant.
Option 4 -> The author realized the juvenile monkey's extreme caution was justified, and they should have been equally cautious in the wild.
Hence, Option 4: Never lower your guard when out in the wild -> The author initially mocked the forest monkey for being overly cautious ("I thought these forest monkeys were such wimps!"), but after the dangerous encounter with the mad elephant, he realized "the juvenile rhesus had a very good reason for being so cautious. We had not." This experience taught him to always remain alert and careful in the wilderness. -> correct