Guide for the Care and Use of Laboratory Animals - Office of ...

ENVIRONMENT, hOUSING, ANd MANAGEMENT 53exercise, manipulative activities, and cognitive challenges according tospecies-specific characteristics (NRC 1998a; Young 2003). Examples ofenrichment include structural additions such as perches and visual barriersfor nonhuman primates (Novak et al. 2007); elevated shelves for cats(Overall and Dyer 2005; van den Bos and de Cock Buning 1994) andrabbits (Stauffacher 1992); and shelters for guinea pigs (Baumans 2005), aswell as manipulable resources such as novel objects and foraging devicesfor nonhuman primates; manipulable toys for nonhuman primates, dogs,cats, and swine; wooden chew sticks for some rodent species; and nestingmaterial for mice (Gaskill et al. 2009; Hess et al. 2008; Hubrecht 1993;Lutz and Novak 2005; Olsson and Dahlborn 2002). Novelty of enrichmentthrough rotation or replacement of items should be a consideration; however,changing animals’ environment too frequently may be stressful.Well-conceived enrichment provides animals with choices and a degreeof control over their environment, which allows them to better cope withenvironmental stressors (Newberry 1995). For example, visual barriers allownonhuman primates to avoid social conflict; elevated shelves for rabbits andshelters for rodents allow them to retreat in case of disturbances (Baumans1997; Chmiel and Noonan 1996; Stauffacher 1992); and nesting material anddeep bedding allow mice to control their temperature and avoid cold stressduring resting and sleeping (Gaskill et al. 2009; Gordon 1993, 2004).Not every item added to the animals’ environment benefits their wellbeing.For example, marbles are used as a stressor in mouse anxiety studies(De Boer and Koolhaas 2003), indicating that some items may be detrimentalto well-being. For nonhuman primates, novel objects can increase therisk of disease transmission (Bayne et al. 1993); foraging devices can leadto increased body weight (Brent 1995); shavings can lead to allergies andskin rashes in some individuals; and some objects can result in injury fromforeign material in the intestine (Hahn et al. 2000). In some strains of mice,cage dividers and shelters have induced overt aggression in groups of males,resulting in social stress and injury (e.g., Bergmann et al. 1994; Haemischet al. 1994). Social stress was most likely to occur when resources weremonopolized by dominant animals (Bergmann et al. 1994).Enrichment programs should be reviewed by the IACUC, researchers,and veterinarian on a regular basis to ensure that they are beneficial to animalwell-being and consistent with the goals of animal use. They should beupdated as needed to ensure that they reflect current knowledge. Personnelresponsible for animal care and husbandry should receive training in thebehavioral biology of the species they work with to appropriately monitorthe effects of enrichment as well as identify the development of adverse orabnormal behaviors.Like other environmental factors (such as space, light, noise, temperature,and animal care procedures), enrichment affects animal phenotype