The most canonical experimental paradigm for studying human attachment styles is the Strange Situation leading to classifications such as Secure, Insecure-avoidant, and so on.
What are the equivalent methodologies, classifications, findings and longtitudinal variability in studies of other primates?
I should add that I'm vaguely aware of, say, Harlow's work, but as far as I understand it, it seems to be about the existence of, rather than the variability of, attachment behaviour in animals.