Crockett, C. M., Bellanca, R. U., Bowers, C. L. et al. 1997. Grooming-contact bars provide social contact for individually caged laboratory primates. Contemporary Topics in Laboratory Animal Science 36(6), 53-60.

We investigated pair housing of adult long-tailed macaques (Macaca fascicularis) by using widely spaced, vertical "grooming-contact" (G-C) bars that allow physical contact but prevent pursuit by one animal into the other's cage. Cages with G-C bars provide several potential advantages over run-through caging. Neighbors can choose physical social contact when both are next to the bars, and either of them can avoid physical contact by keeping out of reach. At the same time, the monkeys are easily accessible to research and husbandry staff because they are in individual cages and do not have to undergo stressful separation procedures. In conjunction with three different studies, pairs housed in G-C cages were evaluated long-term (at least 3 mo) or short-term (8 days). The basic success of pairs, unique combinations of two individuals, was defined as the absence of the necessity for premature separation due to injury or persistent aggression. All 21 male-female pairs (9 long-term; 12 short-term) and all 16 female-female pairs (1 long-term; 15 short-term) were successful, but 5 of 45 male-male pairs were unsuccessful (including the single long-term male-male pair tested). No pregnancies or significant injuries occurred in the nine long-term male-female pairs housed for more than 3207 pair-days in G-C cages with a double panel of bars. These nine pairs spent an average of 12% of the time in social grooming. Although compatible male pairs can be found, far less compatibility testing is required to meet the social needs of long-tailed macaque males by pairing them with females in G-C cages. We anticipate that caging with G-C bars is a housing innovation that will become a widely accepted means of providing social housing and physical contact for adult laboratory primates.