He observed lots about elephant sociology - how they live in small packs who then temporarily merge and divide. He saw evidence of lots of loyalty, learned which elephants could be trusted so he could get close, and saw evidence how they mourned and buried their dead. His vehicle was damaged by elephants several times with tusks thrust through the radiator; he was trampled by a rhinoceros once.
The book is fascinating reading; I strongly recommend it.
Note the detail of the elephant's tail.
This elephant below had really long tusks. I read that they keep growing and can get inconveniently long (~16 ft) if they don't get damaged in fights or at work which apparently is frequent.
A 33 second movie of an elephant in Amboseli Park.