Effect of pair-housing and implications on husbandry and research (photos 50-62)


Photos 50* & 51*: Individually caged monkeys are paired to provide them a species-appropriate environment for the active expression of their need for social contact and social interaction. "Representing an every-changing, yet predictable stimulus, a compatible companion does not lose its boredom-reducing value over time" [Reinhardt & Dodsworth, 1989]. Here 27-year old Sissa grooming her 36-year old companion Senila 15% of the time (photo 50), while Senila spends 32% of the time grooming Sissa (photo 51) more than one year after pair formation [Reinhardt & Hurwitz, 1993; photos by Robert Dodsworth, Wisconsin Regional Primate Reseach Center].
Isosexually pair-housed rhesus macaques spent approximately 20% of the time - females more, males less [Reinhardt, 1990b; cf. stump-tailed macaques: Bernstein, 1980; long-tailed macaques: Crockett et al., 1994] - interacting and contacting each other in non-injurious species-typical manners [Ranheim & Reinhardt, 1989;
Eaton et al., 1994]. This is comparable with the situation of animals living in a natural setting [Teas et al., 1980; Chopra et al., 1992] and suggests that pair-housing offers the animals adequate conditions to meet their basic social needs.




Photos 52 & 53: Subordinate and dominant partners of compatible cage companions do not differ from each other and from single-caged subjects in terms of body weight gains – as compatibility implies that partners share food –, immune responses, serum cortisol concentration [cf. in squirrel monkeys: Coe et al., 1982; Gonzalez et al., 1982], and reproduction [Eaton et al., 1994; cf. Reinhardt et al., 1990,1991b; Reinhardt & Hurwitz, 1993; Schapiro et al., 1993]. There is, however, a conspicuous tendency for pair-housed animals to requiring veterinary treatments - in particular for diarrhea-related problems [Schapiro & Bushong, 1994] - less often than single-housed individuals [Reinhardt, 1990a]. Also, pair-housed companions engage in behavioral disorders less frequently than single-housed subjects [Goosen, 1988; Reinhardt et al., 1988; Eaton et al., 1994]. In a study of seven individually caged rhesus macaques, transfer to compatible pair-housing arrangements effectively cured the animals from the behavioral pathology of self-biting [Reinhardt, 1999a]. A similar finding has also been reported in five long-tailed macaques [Line et al., 1990b], substantiating the assumption that "prolonged individual housing is probably an influential factor" for "self-directed biting' [NRC, 1998].




Photos 54* & 55: Housing rhesus macaques in pairs rather than singly does not interfere with common husbandry procedures such as capture [Reinhardt, 1992c].




Photos 56* & 57*: Housing rhesus macaques in pairs (photo 56: female pair; photo 57: male pair) does not interfere with common handling procedures such as injection or blood collection  [Reinhardt et al., 1989b].

  Photo 58*: Housing rhesus macaques in pairs does not interfere with experimental manipulations such as headcap implantation [Reinhardt, 1991c].

If one partner has to be chair-restrained, the companion comes along to buffer fear and stress reactions (cf. photo 22).




Photos 59* & 60: Housing rhesus macaques in pairs rather than singly does not interfere with time-mated breeding programs [Reinhardt et al., 1989b]. Max and Ray, for example (photo 59), are compatible cage companions since more than 10 years regardless of the fact that Ray (left) has been used as breeder since all these years while Max was assigned to various physiological projects.

Raising offspring does not affect the compatibility of female pairs [Reinhardt & Dodsworth, 1989;
Reinhardt, 1994c]. Here time-mated Beta (left) holding her baby while sharing apples with her cage companion Little (photo 60); Beta and Little are living together as a pair since three years.




Photo 61 & 62: During controlled food-intake studies partners are separated with a grated cage dividing panel or grooming-contact bars [Crockett et al., 1997; Crockett, 1998, Figure 2]
– allowing continuous non-contact communication (photo 61) –
during the day and reunited during the night (photo 62).

  Positive versus negative human-nonhuman primate interactions (photos 63-72)

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