a Pilot colleague of mine who flies Freighter 747's got interested when a group of us in a local bar were talking about the movie "Snakes on a Plane".
He said seriously - he did one flight when 3 Indian Elephants were being transported to the USA. These animals are very social and rarely cause problems - but for some reason they were split up and sealed into separate cages in the cargo hold. They were the only "Freight" that trip.
However they got really stressed as they were all in the same group and they managed to escape from their containers.
The poor Pilot had the agonising decision of saying --shoot them or just let them be. Shooting them would have been a disaster because once one had gone down the other two would have become seriously enraged - with obvious consequences.
Trying to sedate them as well would have the same outcome -- so the poor Pilot just had to try and fly his plane with a load of heavy cargo moving around.
Fortunately Elephants do have quite a lot of intelligence and once they were back in their group out of their cages they settled down fairly peacefully and the flight ended quite OK with zoo staff meeting them on arrival -- I'm sure Los Angeles Immigration at LAX wouldn't have known how to deal with 3 loose elephants in the Immigration arrivals hall.
This stuff does happen believe it ot not. !!