To be a successful Ex pat in Madagascar you will need to learn the Language. There are officially 18 different dialects but there are far more as you move from town to town to village to village and I would give a free estimate of some 50 combined language dialects on top. If you think you can live and survive by only speaking the highlands/Merina language or so called "Language official" then you will be cut off when you travel beyond the Capital, which you will be discriminated against and that will work in both directions as a double edge sword- it cuts both ways. Out side tribes are snubbed when they enter Tana for example for their lack of ability to speak Merina or the" Language Official"
The official language has been perpetuated by the strong political group of the highlands of about 7 Million people- the other 17 tribes ( about 19 million people strong) could care little to less about such language and is the groundwork for civil war that is the quiet under belly conflict of all the tribes and their language and culture for at least 1000 years.
In short ,you ex pats out there- learn the language and dialects, know who you are talking to and their tribe and by recognizing their facial features which is a clue to their tribe. Just as I recognize the faces of the French from the Germans and the Americans and the Aussies and the Brits and the ( and these are easy ones) the Chinese or Indians.
Learning the Local language and dialect shows respect for the tribe but most of all , you will slowly become a member of the community where you choose to settle.