Environmental enrichment is important for keeping patients mentally stimulated and active and meeting their emotional and psychosocial needs. In the mammalian brain, environmental enrichment has been shown to induce biochemical and structural changes that correlate with better memory, learning, and immune function.1,2 Conversely, development of brain function and behavior has been negatively affected in rodents housed in restrictive and socially deprived conditions.3,4 Research also found that ferrets deprived of social stimulation and rough play associated with their natural development had lifelong behavior deficits.3-5
Other behavior issues that can occur if sensory and social needs are not met include overgrooming, self-mutilation, restlessness, cage chewing (Figure 1), stereotypical behaviors, and timidity.6-9 Lack of environmental enrichment can also lead to anorexia (or obesity) from stress, boredom, lack of stimulation, and general inactivity.
Figure 1. Chewing on cage bars can be a sign of stress and/or boredom in small mammals.
Providing enrichment (see Enrichment Strategies by Species) can be easy and inexpensive and allows creativity in simulating circumstances that cater to instinctive behaviors and natural habitats of small mammals (Figure 2).
Figure 2. Placing ping pong balls in a shallow pan of water can keep ferrets entertained and mentally stimulated as they try to fish the balls out of the water. Courtesy of Dr. Peter Fisher
The 5 main areas of enrichment that can be manipulated to better meet the needs and welfare of small mammals are social, physical, nutritional, sensory, and occupational.
Social enrichment includes catering to species-specific needs for social or solitary living and is generally considered the most effective form of enrichment. Many species (eg, rabbits, guinea pigs, mice, rats, chinchillas, sugar gliders [Figure 3]) prefer to be group housed. Care should be taken to ensure adequate, supervised bonding and the correct gender balance based on species. Those housed in groups should also have enough room and shelter to interact while spacing themselves in a socially acceptable way.
Figure 3. Keeping inherently social species (eg, sugar gliders) together is important in providing for psychosocial needs.
Although social interactions account for the most dynamic form of enrichment, they are also likely to result in injury. Some species, such as Syrian and Chinese hamsters, are prone to intraspecies aggression, and elevated cortisol levels related to stress have been detected when housed in groups.10,11
Physical enrichment entails making the patient’s environment conducive to performing natural behaviors (eg, digging, chewing, gnawing, climbing, perching) that can help minimize stress-related behaviors and improve quality of life (Figures 4–6).
Figure 4. Given sufficient room in an enriched rabbit-safe area, rabbits can be quite inventive. Courtesy of Darice Heishman
Figure 5. Creating tunnels using interconnected cardboard boxes covered with sheets or towels is a simple way to enrich the environment of small mammals. Placing food items in different areas of the tunnels is mentally stimulating and encourages physical activity. Courtesy of Paul and Debbie Ladas
Figure 6. Tunnels, deep hay, scattered food treats, and bonded cage mates can enrich the quality of life for guinea pigs. Courtesy of Rebecca Howell
Changes as simple as providing larger cages and deeper bedding resulted in fewer stereotypies (eg, cage chewing, excessive running on hamster wheel).11,12 Deep bedding can also help many rodents better regulate body temperature. Hamsters kept in deep substrate (40 cm, 15.8 in) were perceived to have better welfare than those kept in shallow bedding (10 cm, 3.9 in).13 Gerbils also prefer deep bedding (20 cm, 7.9 in) for tunnel construction (Figure 7).13
F__igure 7. Deep bedding, ramps, and vertical spaces can provide enrichment and help offset aggressive behavior in gerbils. Courtesy of Lewana Parker
Many small mammals prefer to be on high perches, likely so they can watch for perceived predators. Animals can perch on top of a hide box, or carpeted ramps can give them access to shelving or other vertical spaces (Figure 8).6 Introducing novel objects can improve spatial memory and lower stress to new situations, but care should be taken not to elicit fear or stress by introducing too many changes at once or too often.
Figure 8. An enriched enclosure for rats can include ramps, vertical shelves, hide spaces, toys, and deep bedding (A). Providing places to hide, be with cage mates, and enjoy nutritional treats (B) is important when small mammals are hospitalized.
Enriching the environment with healthy, species-appropriate food treats and providing foraging opportunities are other ways of fostering stimulation and increasing exercise (Figure 9). One study in rabbits showed that activity time was preferentially increased with food-based enrichment.14 Providing nutritional enrichment can be as simple as scattering food items in bedding for small rodents and other small mammals housed in groups, thereby encouraging foraging and increasing activity, both of which can lower cage-mate aggression.
Figure 9. Growing grass for herbivores creates a safe way to provide nutritional enrichment. Courtesy of Rebecca Howell
More complex environmental modifications to provide food include drilling holes in a nontoxic tree branch and filling it with favored foods to allow sugar gliders to forage similarly to how they would in nature.15,16
Care should be taken not to overfeed, and daily rations should be decreased so treats for enrichment do not result in obesity and medical problems.17
Sensory enrichment includes increasing sensory stimuli (ie, manipulating the environment with safe novel items, tastes and smells). This might include rotating cage furniture and food items and treats that are in season and occasionally providing safe branches smeared with a favored food. Providing a day/night cycle appropriate for the species can also aid sensory well-being.
Protected enrichment areas outside the cage allow for safety from other pets, young children, and predators (if outdoors) and dangerous items that can be chewed or ingested (eg, toxic plants, electrical cords). Supervision is recommended, especially for smaller species and always when a small pet mammal is outdoors. Protected areas can be as simple as a portable folding pen or a series of connected cardboard boxes or PVC tubing.
Figure 10. Compressed haystacks can enrich the lives of grass-eating species by providing mental stimulation through foraging for food. Courtesy of Oxbow Animal Health
Occupational enrichment allows small mammals to modify and have more control of their environment, which can lead to problem solving and learning. This includes allowing for environmental manipulation by providing objects or toys that stimulate problem solving, motor skills, and coordination. Providing materials to build nests or wood blocks that must be chewed through to gain access to another area of the enclosure also allows captive small mammals to modify their environment.
Figure 11. Providing a PVC structure with hammocks (A), hide spaces, and a solid small mammal safe wheel (B) can keep sugar gliders active and mentally stimulated. Courtesy of Tracie Brandow
Enrichment is necessary for small mammals and is as important as routine veterinary care and proper nutrition.5 Using natural history and species-specific natural behavior as a guide to creating healthier environmental parameters—while taking individual temperaments into consideration when choosing environmental manipulations—can make a significant difference in the quality of life of small pet mammals. Various safe toys, distractions, and healthy food treats that simulate natural behaviors can help offset boredom and destructive behaviors, increase exercise levels, and provide the mental stimulation that all pets deserve.
TERESA BRADLEY BAYS, DVM, CVA, DABVP (ECM), owns Belton Animal Clinic & Exotic Care Center in Belton, Missouri. She is an international speaker; has authored numerous articles on exotic animal medicine, several chapters for Veterinary Clinics of North America/Exotic Animal Practice, and the behavior chapter in Ferrets, Rabbits & Rodents; and is senior editor and coauthor of Exotic Pet Behavior—Birds, Reptiles & Small Mammals. Dr. Bays created Pajamas for Foster Kids and coleads KC-CAN, educating others on the correlation between animal abuse and domestic violence. Dr. Bays earned her DVM from Kansas State University and is a certified veterinary acupuncturist.
1. Double dissociation of social and environmental stimulation on spatial learning and reversal learning in rats. Schrijver NC, Pallier PN, Brown VJ, Würbel H. Behav Brain Res 152:307-314, 2004.2. Environmental enrichment enhances delayed-type hypersensitivity in both short- and long-day Siberian hamsters. Workman JL, DeWitt SJ, Fonken LK, Nelson RJ. Physiol & Behav 99:638-643, 2010.3. Effects of experience and environment on the developing and mature brain: Implications for laboratory animal housing. Benefiel AC, Greenough WT. ILAR J 39:5-11, 1998.4. Ideal homes? Housing effects on rodent brain and behaviour. Würbel H. Trends Neurosci 24:207-211, 2001.5. The effects of environmental enrichment in ferrets. Einon D. In Smith CP, Taylor VP (eds): Environmental Enrichment Information Resources for Laboratory Animals: 1965-1995. Birds, Cats, Dogs, Farm Animals, Ferrets, Rabbits, & Rodents. AWIC Resource Series No. 2— Beltsville: USDA & Hertfordshire, 1995, pp 113-126.6. The effect of environmental enrichment on the behaviour of caged rabbits (Oryctolagus cuniculus). Hansen LT, Berthelsen H. Appl Anim Behav Sc_i 68:163-178, 2000.7. Sources of stress in captivity. Morgan KN, Tromborg CT. _Appl Anim Behav Sci 102:262-302, 2007.8. Environmental enrichment reduces the likelihood of alopecia in adult C57BL/6J mice. Bechard A, Meagher R, Mason G. J Am Assoc Lab Anim Sci 50:171-174, 2011.9. Cage-induced stereotypies in female ICR CD-1 mice do not correlate with recurrent perseveration. Gross AN, Engel AK, Richter SH, et al. Behav Brain Res 216:613-620, 2011.10. Effects of social conditions on adult and subadult female rat-like hamsters (Cricetulus triton). Zhang JX, Ni J, Wu FY, Zhang ZB. J Ethol 22:161-165, 2004.11. Hamsters. Albright J, de Matos R. In Tynes VV (ed): Behavior of Exotic Pets—West Sussex: Wiley-Blackwell, 2010, pp 127-137.12. The striped or Chinese hamster: Biology and care. Chang A, Diani A, Connell M. In Van Hoosier GL Jr, McPherson CW (eds): Laboratory Hamster—Orlando: Academic Press, 1987, pp 305-320.13. Behavior of rodents with an emphasis on enrichment. Brandão J, Mayer J. J Exot Pet Me_d 20:256-269, 2011.14. Evaluation of objects and food for environmental enrichment of NZW rabbits. Harris LD, Custer LB, Soranaka ET, et al. _Contemp Top Lab Anim Sci 40:27-30, 2001.15. Feeding behavior and nutrition of the sugar glider (Petauras breviceps). Dierenfeld ES. Vet Clin North Am Exot Anim Pract 12:209-215, 2009.16. Sugar gliders. Booth R. Semin Avian Exotic Pet Med 12:228-231, 2003.17. Gerbils. Parker ADF, Tynes VV. In Tynes VV (ed): Behavior of Exotic Pets—West Sussex: Wiley-Blackwell, 2010, pp 117-126.