Cage Size Preference in Rats in the Laboratory Emily G. Patterson-Kane Animal Welfare Program Faculty of Agricultural Sciences University of British Columbia The size of an enclosure is an integral part of how well it accommodates a nonhuman animal’s welfare; however, most enrichment studies concentrate on modifying the area inside the enclosure rather than enlarging it. It has been suggested that rats have little need for more cage space, but there is no empirical evidence about rats’ need for space. This experiment provides preliminary evidence for the preferences of 5 male and 5 female albino rats using T-maze choices followed by 5 min dwelling times. The rats showed a moderate but significant preference for the larger of 2 cages (540 cm2 vs. 1,620 cm2; binomial z, p < .05). When the rats shared the chosen cage with 4 famil- iar cage mates, their preference for the larger cage did not become any stronger (paired t(9) = –.820, p > .05). The results suggest that rats should be given a somewhat larger space allowance but could share it with up to 4 other rats. Appropriate enrichment can be based on observations of wild and feral popula- tions (Brain, 1992; Patterson-Kane, in press). Observations of free-living rats (Rattus norvegicus) have indicated that they typically form large colonies in ar- eas in which there is plentiful ground cover and they create complex burrows (Boice, 1977). Considerable research has demonstrated that these same variables can be used to enrich the caging of rats in the laboratory and substantially im- prove their welfare: (a) social contact (R. N. Hughes, 1969; Johnson, DeSisto, & Koenig, 1972; Morgan & Einon, 1975; Perez et al., 1997), (b) more complex en- vironments (Anzaldo, Harrison, Riskowski, Maghirangi, & Gonyou, 1994; JOURNAL OF APPLIED ANIMAL WELFARE SCIENCE, 5(1), 63–72 Copyright © 2002, Lawrence Erlbaum Associates, Inc. Requests for reprints should be sent to Emily G Patterson-Kane, Animal Welfare Program, Univer- sity of British Columbia, 2357 Main Mall, Vancouver British Columbia, Canada V6T 1Z4. E-mail: Rattitude2@hotmail.com