Sequelae of Occult Aggression Disqualifying Young, Socially Housed, Female New Zealand White Rabbits (Oryctolagus cuniculus) from Participation in Dermal Toxicology Studies.

International animal welfare organizations and federal, regional, and institutional oversight bodies encourage social housing of gregarious species, such as New Zealand white rabbits (Oryctolagus cuniculus), to promote animal wellbeing in research, teaching, testing and farming settings. At our institution, 2 groups of female New Zealand white rabbits (approximate age, 11 wk; mean weight, 2.35 kg), compatibly paired at the vendor for 5 wk, were paired in caging or group-housed in a floor pen. The rabbits appeared compatible, demonstrating primarily affiliative behaviors throughout 6 wk of daily observations. However, occult aggression that occurred between daily observations or nocturnally resulted in skin wounding. The skin injuries, first identified during prestudy clipping of fur from the back of each rabbit 6 wk after arrival, disqualified every animal from participation in skin toxicology and muscle implantation studies. Success meeting scientific research requirements while promoting animal welfare and health when socially housing New Zealand white rabbits requires examining the behavioral repertoire of their wild counterparts, European rabbits. Factors including age, sex, and housing density influence territoriality, dominance hierarchy, social ranking, and natural, agonistic, injurious, behavioral tendencies. IACUC and other relevant oversight bodies, researchers, and animal care staff should consider this case study and the species-specific natural history of New Zealand white rabbits when assessing the harm and benefit of social housing in regard to research utility and animal welfare.