The population of Nepal is composed by process called census
I believe the answer is: They thought it was animals.
At that time, the colonists still haven't been familiar with the local tribes in that area. By the time they realized that that the sound came from the native (as some sort of war cry that they do to initiate an attack) , it's far too late for them to run away.
This is not an easy questions, and there are different answers from different sources. I would start with:
1) all basic needs satisfied: food, security, shelter, health care
2) good social relations
3) possibility to grow: life-long education, possibility of advancement at work
4) time and resources to pursue hobbies and interests.
