As a contribution to the more general discussion on causes of language endangerment and death, we describe the language ecologies of four related languages (Bà Mambila [mzk]/[mcu], Sombә (Somyev or Kila) [kgt], Oumyari Wawa [www], Njanga (Kwanja) [knp]) of the Cameroon-Nigeria borderland to reach an understanding of the factors and circumstances that have brought two of these languages, Sombә and Njanga, to the brink of extinction; a third, Oumyari, is unstable/eroded, while Bà Mambila is stable. Other related languages of the area, also endangered and in one case extinct, fit into our discussion, though with less focus. We argue that an understanding of the language ecology of a region (or of a given language) leads to an understanding of the vitality of a language. Language ecology seen as a multilayered phenomenon can help explain why the four languages of our case studies have different degrees of vitality. This has implications for how language change is conceptualised: we see multilingualism and change (sometimes including extinction) as normative.