This paper uses variationist methods to attack a descriptive problem: by looking at the distribution of a typologically unusual subject prefix (tem- in realis and t- in irrealis) in a set of narrative texts recorded in Nkep, the language of Hog Harbour (Vanuatu), it explores the extent to which the goals of language documentation and variationist sociolinguistics can be pursued simultaneously. It concludes that a dual focus can benefit both enterprises. One finds out considerably more about the nature of subject-verb prefixes in Nkep and about the ways in which the Nkep language handles grammatical properties such as the realis/irrealis distinction. The paper also notes that studies of variation in endangered language contexts can provide a positive framework for the local community to evaluate synchronic variation and change.