I’m about to have one of my front teeth crowned, and my dentist asked me to visit the dental technician for him to determine the appropriate colour match. I did so, and was impressed by his evident mastery of his subject. He took a whole series of photos of my face and teeth, first taking me into the natural daylight outside the building, and explaining to me how the replacement would be built up from multiple layers of porcelain of different translucencies and shades.
What struck me, however, was that he pronounced the word canine as kəˈnaɪn. For this word I’m only familiar with ˈkeɪnaɪn and ˈkænaɪn (the former, I think, predominating); so his version was new to me. Yet for him this is an everyday technical term of his professional speciality.
I see the OED gives all three pronunciations without comment, so perhaps he’s not alone. (Merriam-Webster Collegiate gives ˈkeɪ-, adding ˈkæ- for BrE only.)
This word is one of several that we have taken from Latin, all meaning ‘X-related’, where X is the name of an animal: aquiline, feline, asinine, vulpine and so on. Canine teeth are ‘dog-like’ teeth (Latin cănis ’dog’). It is regular in these adjectives for the suffix to be pronounced aɪn and for the stress to go on the stem. In some cases the Latin vowel length in the stem is preserved: ˈækwɪlaɪn (Latin ăquĭla ‘eagle’), ˈfiːlaɪn (fēles, fēlis 'cat’), ˈæsɪnaɪn (ăsĭnus ‘donkey, ass’), ˈvʌlpaɪn (vŭlpes ‘fox’) and so on — but in other cases, not: bovine ˈbəʊvaɪn (bōs, but stem bŏv- ‘ox, cow’), ovine ˈəʊvaɪn (ŏvis ‘sheep’). Hence the hesitation in canine ˈkeɪ- ~ ˈkæ-, which we also see in equine ˈiːk- ~ ˈek- (ĕquus ‘horse’).
The only case I can think of in which a Latin adjective in -īnus gives an English adjective with final stress does not have a stem designating an animal: marine məˈriːn (măre ‘sea’). It is also the only one in which the suffix is pronounced iːn rather than aɪn.