Guides, Guidelines & Regulations

Rodents

Baumans V 2004. The welfare of laboratory mice. In The Welfare of Laboratory Animals Kaliste E (ed), 119-152. Kluwer Academic Publishers, Dordrecht, The Netherlands
Excellent brief recommendations for the species-adequate housing of mice.

Brain PF, Büttner D, Costa P, Gregory JA, Heine WOP, Koolhaas J, Militzer K, Ödberg FO, Scharmann W, Stauffacher M, Baumans V, Poole TB, Sachser N, Whittaker D 1994 Rodents. In The Accommodation of Laboratory Animals in Accordance with Animal Welfare Requirements. Proceedings of an International Workshop held at the Bundesgesundheitsamt, Berlin [The Berlin Workshop]. O'Donoghue PN (ed), 1-14. Bundesministerium für Ernährung, Landwirtschaft und Forsten, Bonn, Germany
'Berlin Workshop' recommendations for the adequate housing of rodents address following issues: (1) Should rodents be maintained in pens or cage? (2) Should rodents be kept in groups or individually? (3) What should be the minimum cage size? (4) Complexity of space. (5) Is bedding necessary? "As laboratory rodents (notably mice, rats, hamsters, gerbils and guinea pigs) account for around 80% of the vertebrate species used in experimental and scientific procedures, changes applied to such animals would produce the most impact in welfare terms. .. It is also true that such animals have a lesser ability to move the sympathies of the general public than cats, dogs, rabbits and primates. It is odd, however, that welfare specialists are frequently urged to 'prove' that changes are beneficial to rodents by the same individuals who less critically accept enrichment for more emotive species."

Jennings M, Batchelor GR, Brain PF, Dick A, Elliott H, Francis RJ, Hubrecht RC, Hurst JL, Morton DB, Peters AG, Raymond R, Sales GD, Sherwin CM, West C 1998. Refining rodent husbandry: the mouse - Report of the Rodent Refinement Working Party. Laboratory Animals 32, 233-259
This report "describes ways in which existing husbandry and care of mice can be improved with emphasis on providing environments that allow the animals to express a wide range of behaviours." Valuable recommendations are made on the following topics: Caging materials; Cage size and design; Cage floor; Bedding and nesting material; Cage furniture; Establishing social groups; Cleaning and odour cues; Handling; Light; Noise.

Kuhnen G 2002 Comfortable quarters for hamsters in research institutions. In Comfortable Quarters for Laboratory Animals, Ninth Edition. Reinhardt V, Reinhardt A (eds.), 34-38. Animal Welfare Institute, Washington, DC
Practical guidelines for the species-adequate housing of hamsters in research facilities."Any housing system for hamsters should satisfy the physiological and ethological needs for resting, nestbuilding, grooming, exploring, climbing, hiding, digging, searching for food, hoarding and gnawing. Golden hamsters readily overcome their instinctive fear of humans when they are regularly handled with gentleness. Regular, gentle handling of a research hamster is no waste of time but will pay off in more reliable research data."

Lawlor MM 2002 Comfortable quarters for rats in research institutions. In Comfortable Quarters for Laboratory Animals, Ninth Edition. Reinhardt V, Reinhardt A (eds.), 27-33. Animal Welfare Institute, Washington, DC
Very useful guidelines for the species-adequate housing of rats. "Even though U. S. federal regulations currently do not regard rats as "animals" (United States Department of Agriculture, 1995), rats require and deserve the same professional care as other, perhaps more charismatic laboratory animals, because their well-being determines no less the quality and reliability of scientific research data collected from them. In order to design a species-appropriate and scientifically sound housing protocol it is essential to view the world with the eyes of a rat. It is through patient observation and a grain of humbleness that such a view can be cultivated."

National Research Council 1996 Guide for the Care and Use of Laboratory Animals, 7th Edition. Washington, DC: National Academy Press
"All who care for or use animals in research, teaching, or testing must assume responsibility for their well-being. .. A good management program provides the environment, housing, and care that ... minimizes variations that can affect research. Evidence suggests that solid-bottom caging, with bedding, is preferred by rodents. ...
Depending on the animal species and use, the structural environment should include resting boards, shelves or perches, toys, foraging devices, nesting materials, tunnels, swings, or other objects that increase opportunities for the expression of species-typical postures and activities and enhance the animals well-being. .. Animals should be housed with the goal of maximizing species-specific behaviors and minimizing stress-induced behaviors. For social species, this normally requires housing in compatible pairs or groups. ... In general, lighting should be diffused throughout an animal holding area and provide sufficient illumination for the well-being of the animals and to allow good housekeeping practices, adequate inspection of animals - including the bottom-most cages in racks - and safe working conditions for personnel."

NSW [New South Wales] Agriculture 2004 ARRP Guideline 20: Guidelines for the Housing of Rats in Scientific Institutions - DRAFT. Orange, NSW: NSW Department of Primary Industries
Very useful, practical guidelines for the species-appropriate care and housing of rats. It includes recommendations on cage design, rat care and management and environmental variables. "Adult rats should preferably be housed in groups not larger than 5 individuals taking into account differences between strains and sex Ideally rat groups should be made up of litter mates of the same sex Shelters should be provided within cages to enable rats to hide in case of conflict Rats should be provided with items to enrich their environment. Items that assist rats to perform each of the five following categories of behaviours should be provided: social interaction; chewing/gnawing; locomotion (including climbing, exploring and playing); resting/hiding and manipulating, carrying and hoarding food and objects."

Reinhardt V 2002 Comfortable quarters for guinea-pigs in research institutions. In Comfortable Quarters for Laboratory Animals, Ninth Edition. Reinhardt V, Reinhardt A (eds.), 39-43. Animal Welfare Institute, Washington, DC
Practical guidelines for the species-adequate housing of guinea pigs in research facilities. "Animals living in groups should be provided a floor area of no less than 1200 cm2 per breeding female, and no less then 750 cm2 per weaned, non-breeding animal. A box with an access hole makes the central area of the enclosure a place of refuge for the animals thereby improving their well-being and, at the same time, increasing the usable floor space."

Sherwin CM 2002 Comfortable quarters for mice in research institutions. In Comfortable Quarters for Laboratory Animals, Ninth Edition. Reinhardt V, Reinhardt A (eds.), 6-17. Animal Welfare Institute, Washington, DC
Very useful guidelines for the species-adequate housing of mice. "In providing comfortable quarters for mice, there are several '-isms' we should avoid. We should avoid speceisism and remember there is no evidence to suggest that mice do NOT have the same capacity to suffer as other vertebrates, although their suffering might occur in different ways. We should also avoid anthropomorphism and anthropocentrism, and try to understand the mouse's world from it's own perspective, rather than our own human concerns. We should also avoid sizeism: simply because laboratory mice are small and can all appear to be the same [at least to us], this does not mean they have any less capacity to suffer as individuals. In promoting appropriate housing for mice, it can be helpful to think in terms of optimising the 2 Q's, i.e., Quantity of space and Quality of space. We should be aiming to provide mice with the appropriate amount of space containing the appropriate diversity of environment that takes into account their species-specific characteristics and needs."

Sutherland SD, Festing MFW 1987 The guinea-pig. In The UFAW Handbook on the Care and Management of Laboratory Animals, Sixth Edition. Poole TB (ed), 393-410. Churchill Livingstone, New York, NY
Brief outline of species-adequate housing for guinea pigs. Softwood shavings or coarse sawdust are the most commonly used bedding materials, but peat-moss has also been used. Hay, which should primarily be used as a food, is usually fed loose and so can act as a bedding material.

United States Department of Agriculture 1995. Standards under the Animal Welfare Act as Amended (7 USC, 2131-2156) [Guinea Pigs, Hamsters, Rabbits]. 9 CFR Ch. 1 (1-1-95 Edition) Specifications for the Humane Handling, Care, Treatment, and Transportation of Guinea Pigs and Hamsters and Rabbits, §3.25 - §3.41 & §3.50 - §3.66
Federal law pertaining to the minimum requirements of acceptable housing and handling of laboratory animals.

Waiblinger E 2002 Comfortable quarters for gerbils in research institutions. In Comfortable Quarters for Laboratory Animals, Ninth Edition. Reinhardt V, Reinhardt A (eds.), 18-26. Animal Welfare Institute, Washington, DC
Practical guidelines for the species-adequate housing of gerbils in research facilities. " To create adequate quarters for gerbils in research laboratories the following provisions must be made to address the animals basic conditions for well-being: Species-adequate artificial burrow system;social housing; offspring stays long enough in the family group to get experienced in the care of juveniles."

Whittaker D 1999 Hamsters. In The UFAW Handbook on the Care and Management of Laboratory Animals Seventh Edition. UFAW [Universities Federation for Animal Welfare] (edited by Poole, T. and English, P. ), 256-266. Blackwell Science, Oxford, UK
"In summary, solid-bottomed cages with bedding material are preferable; in general, group housing is preferable to individual caging so long as the groups are formed early in life, are stable and harmonious. There should be room for hiding and escaping conspecifics within the cage."

Wolfensohn S, Lloyd M 1994 Handbook of Laboratory Animal Management and Welfare - Chapter on small species: Gerbils and Hamsters. Oxford, UK: Oxford University Press
"Gerbils are generally docile creatures, which are easily handled and rarely bite. They are generally very active, and when approached, they will resist being caught. Normally they exhibit exploratory behaviour in new surroundings, and if loose they do not hide but show curiosity and interest in the environment." Compatible "groups may be established by putting animals together before weaning. ... Gerbils prefer solid floors to mesh, and need at least 2 cm depth of bedding for nest building. ... Sawdust or shavings made from pine should not be used, as the fur tends to become matted with these materials. ... Gerbils need at least 15 cm space between the top of the bedding and the roof of the cage, as they like to sit erect. ... Hamsters are readily tamed, and rarely bite unless startled or handled roughly. Males are more docile than females. ... Groups of same sex animals may be maintained if they are put together at weaning or before puberty. ... Hamsters, being solitary, prefer to be housed individually."

Working Party for the Preparation of the Fourth Multilateral Consultation of Parties to the European Convention for the Protection of Vertebrate Animals Used for Experimental and Other Scientific Purposes (ETS 123) 2000 Proposal II (General part of Appendix A). Strasbourg, France: Council of Europe
"Animals should be socially housed whenever possible and provided with an adequately complex environment within the enclosures to enable them to carry out a range of normal behaviours. Restricted environments can lead to behavioural and physiological abnormalities and affect the validity of scientific data. ... Unless otherwise specified, additional surface areas provided by cage inserts such as shelves should be provided in addition to the recommended minimum floor areas. .. The flooring should provide a solid, comfortable resting area for all animals .. Animal care staff are expected, at all times, to have a caring and respectful attitude towards animals in their care, and to be proficient in their handling and restraint .. Where appropriate, staff time should be set aside for talking, handling and grooming ... Consideration should be given to windows, since they are a source of natural light and can provide environmental enrichment for some species."

Working Party for the Preparation of the Fourth Multilateral Consultation of Parties to the European Convention for the Protection of Vertebrate Animals Used for Experimental and Other Scientific Purposes (ETS 123) 2000 Revised Proposals for Rodents & Rabbits. Strasbourg, France: Council of Europe
Basic, but valuable recommendation for species-adequate housing environments.

Rabbits

Batchelor GR 1999 The Laboratory Rabbit. In The UFAW Handbook on the Care and Management of Laboratory Animals Seventh Edition. Poole T, English P (eds), 395-408. Blackwell Science, Oxford, UK
Description of rabbit-adequate floor pen housing and cage housing systems. "Behavioural work that the author has carried out has shown a significant improvement in the quality of life for group housed animals, even those regarded as subordinate, compared to those housed in solitary confinement."

Boers K, Gray G, Love J, Mahmutovic Z, McCormick S, Turcotte N, Zhang Y 2002 Comfortable quarters for rabbits in research institutions. In Comfortable Quarters for Laboratory Animals, Ninth Edition. Reinhardt V, Reinhardt A (eds.), 44-50. Animal Welfare Institute, Washington, DC
Practical recommendations for the species-adequate housing and handling of rabbits. "The most suitable quarters for rabbits allow for social interaction and provide physical substrate for digging, playing and hiding."
"The gentle touch provided by the technicians is as important as the physical environment in giving the rabbits a sense of security in the presence of humans who, in other circumstances may subject them to uncomfortable, perhaps even painful procedures."

Gunn-Dore D 1997 Comfortable quarters for laboratory rabbits. In Comfortable Quarters for Laboratory Animals, Eighth Edition. Reinhardt V (ed), 46-54. Animal Welfare Institute, Washington, DC
Valuable recommendations for rabbit-adequate housing and handling conditions. "The traditional standard-sized single cages currently used for housing rabbits are inadequate to satisfy the animals' behavioral and physiological needs. Group housing arrangements, preferably in well-structured floor pens with straw bedding and individual nest boxes can overcome these shortcomings. Group-housed rabbits express a considerably enhanced behavioral repertoire compared with singly caged rabbits. They are truly rabbits, because they can hop, leap, sit up on the hind legs in rabbit-fashion, hide in 'burrows', forage with other conspecifics, groom each other and sham-burrow in the substratum before lying down. In situations where a rabbit has to be caged alone, access to a refuge area and objects for gnawing and playing should be provided. A single caged rabbit must never be kept in social isolation but should always be able to have visual and possibly also olfactory contact with other rabbits."

Morton DB, Jennings M, Batchelor GR, Bell D, Birke L, Davies K, Eveleigh JR, Gunn D, Heath M, Howard B, Koder P, Phillips J, Poole T, Sainsbury AW, Sales GD, Smith DJA, Stauffacher M, Turner RJ 1993. Refinements in rabbit husbandry. Second report of the BVAAWF/FRAME/RSPCA/UFAW joint working group on refinement. Laboratory Animals 27, 301-329
Very useful recommendations for and review of species-appropriate housing and handling of rabbits. "The aims of this report is to identify the needs of domesticated rabbits and to present information on ways in which the current system of housing rabbits can be improved. ... In general, animals for group housing should be of the same sex, of similar size and, if possible, related and grouped when young. ... It is always important to provide refuges and hiding places for subordinate animals." The frequency of stereotyped behavior is substantially less in group-housed than in single-caged rabbits. "Whatever their weight or age we recommend rabbits kept in groups have a clear area of around 20000 cm2 in each pen to ensure that they are provided with space for activities such as hopping." Article includes a comprehensive and clear, descriptive ethogram [without photos] of rabbits.

NSW [New South Wales] Agriculture 2002 ARRP Guidelines 18: Guidelines for the Housing of Rabbits in Scientific Institutions. Orange, NSW: NSW Agriculture
Very useful, practical guidelines for the species-appropriate care and housing of rabbits. It includes recommendations on group housing in pens; pen design and environment; rabbit care and management; cage design and environment; cage enrichment; environmental variables. "Rabbits should be housed in groups in pens. Rabbits that cannot be housed in groups should be housed in pens with olfactory, visual and, if possible, physical contact with adjacent rabbits It is important that rabbits are provided with sufficient space and objects to assist them to escape and hide from their aggressors. Objects such as boxes, pipe, ledges and vertical barriers provide means for hiding and escape. Sufficient objects should be provided to eliminate competition for such items."

Stauffacher M, Bell DJ, Schulz K-DBV, Brain PF, Büttner D, Drescher B, Jilge B, Laurent J, Loeffler K, Militzer K, Morton DB, Nebendahl K, Schwartz K, Turner RJ, Völlm J 1994 Rabbits. In The Accommodation of Laboratory Animals in Accordance with Animal Welfare Requirements. Proceedings of an International Workshop held at the Bundesgesundheitsamt, Berlin [The Berlin Workshop]. O'Donoghue PN (ed), 15-30. Bundesministerium für Ernährung, Landwirtschaft und Forsten, Bonn, Germany
'Berlin Workshop' recommendations for the adequate housing of rabbits in the research laboratory setting address the following issues: (1) Should rabbits be maintained in pens or in cages. "Housing laboratory rabbits in groups in floor pens is recommended as a good alternative to cage housing as long as the animals are socially compatible." (2) Should rabbits be kept in groups or individually? If grouped, what should be the group size? "Individual housing in cages is the only practicable system for sexually-mature males (which are generally incompatible and for incompatible females." (3) What should be the minimum size of cages (Floor area and height)? "Cages should allow adult rabbits to stretch at full length and the height should allow them to sit up straight." (4) What should be the minimum size of pens? What should be the minimum area per animal? (5) What construction and design of cages should be used? (6) What construction and design of the floors of the pens or cages should be used? (7) What structural division of the space should be available? (8) Should occupational or nesting material ("Enrichment") be supplied? (9) Is bedding necessary? If so, of what quality? (10) Does the described housing system provide rabbits with the opportunity of taking sufficient exercise? "Minimum cage dimensions should allow the rabbit to perform at least 2-3 hopping steps."

Table of Contents

Bedding & Nesting Material
  
Bedding & flooring

Rats
Blom HJM, van Tintelen G, Baumans V, Beynen AC 1993 Comparison of sawdust bedding and wire mesh as cage flooring in preference tests with laboratory rats. Utrecht, Netherlands: Utrecht University
Rats preferred sawdust bedding and avoided cages with wire mesh or with a bare solid floor.

Blom HJM, van Tintelen G, van Vorstenbosch CJAHV 1996. Preferences of mice and rats for types of bedding material. Laboratory Animals 30, 234-244
"The results seem to indicate that size and manipulability are among the main determinants of the appreciation of bedding particles by laboratory mice and rats, and larger particles are preferred. .. In the test system with two test cages, [aspen] wood chips were preferred over sawdust and wire mesh. .. Shredded filter paper was so attractive to female laboratory mice that it masked differential preferences for wood chips, sawdust and wire mesh floor". When given a choice mice spend more time on solid than grid floor.

Dickson C, Wrightson D 1999. Rat cage modification: Improving welfare. Animal Technology 50, 43-44
"Rats living on a grid floor tended to rest piled in heaps, but they spread out and relax more on the solid floors."

Grover-Johnson N, Spencer PS 1981. Peripheral nerve abnormalities in aging rats. Journal of Neuropathology and Experimental Neurology 40, 155-165
Rats prefer solid-bottom caging with bedding over wire-bottom caging.

Hawkins P 1999. Working together to improve rodent well-being. Lab Animal 28(2), 30-32
"While rats housed on grid or mesh floors tend to pile up in heaps while resting, rats with access to solid flooring spread out on the bedding."

Krohn TC, Hansen AK, Dragsted N 2003. Telemetry as a method for measuring the impact of housing conditions on rats' welfare. Animal Welfare 12, 53-62
"The study revealed significant differences in systolic and diastolic blood pressure, heart rate and body temperature between rats housed in the three conditions, indicating that both grid floors and plastic floors are more stressful for the animals than bedding. The observed differences did not diminish over the two-week observation period. "

Manser CE, Elliott H, Morris TH, Broom DM 1996. The use of a novel operant test to determine the strength of preference for flooring in laboratory rats. Laboratory Animals 30, 1-6
"Both studies indicated that rats prefer to rest on solid floor. The experiments reported in this paper also show that rats are prepared to make considerable efforts to reach a solid floor when they wish to rest. Thus there is ground for suggesting that laboratory rats be housed on solid rather then grid floors whenever possible."

Manser CE, Morris TH, Broom DM 1995. An investigation into the effects of solid or grid cage flooring on the welfare of laboratory rats. Laboratory Animals 29, 353-363
"Preference testing revealed that rats chose to dwell on solid floors rather than grids, regardless of previous housing experience. This preference for solid floors was particularly marked (88%) when the animals were resting and much less during activity (55.4%). Since the rats were observed to spend 70 to 75% of their time resting, it was concluded that their welfare was likely to be improved by housing them on solid floors."

Mulder JB 1974. Bedding selection by rats. Laboratory Animal Digest 9, 27-30
Rats showed a preference for aspen shaving bedding.

Ras T, Van de Ven M, Patterson-Kane EG, Nelson K 2002. Rats' preferences for corn versus wood-based bedding and nesting materials . Laboratory Animals 36, 420-425
"Corn by-products can be used as bedding and nesting products. Corn-cob bedding resists ammonia build-up and corn-husk nesting material resists dampness. It is not clear whether these advantages are at the expense of animal comfort. Corn cob was compared to aspen chip bedding, and corn husk to paper strip nesting material. Data from 20 rats with differential early bedding experience suggested that they prefer aspen chip, but are also biased towards the bedding they were raised on. Data from 10 rats with no prior nesting material experience suggested that paper strip was preferred over cornhusk. Thus, corn-cob products are not recommended except in situations where air quality and/or flooding are significant problems."

Rock FM, Jaslow BW, Peterson A, Kaeppeli MK, Price JL 2000. Preference of single housed rats for a solid-bottom or wire-bottom stainless steel cage floor. AALAS [American Association for Laboratory Animal Science] 51st National Meeting Official Program , 79 (Abstract)
"We modified a stainless steel multiple-animal wire-bottom cage by covering one-half of the floor surface with a solid plate of stainless steel [emphasis added]. .. At night, rats demonstrated a significant (P <0.05) preference for a solid-bottom stainless steel floor. During the daytime rats significantly (P <0.05) preferred the wire-bottom side of the cage."

Van de Weerd HA, van den Broek FAR, Baumans V 1996. Preference for different types of flooring in two rat strains. Applied Animal Behaviour Science 46, 251-261
"The rats showed a significant preference for the cages with wood shavings and paper bedding, both consisting of large particles. ... The cages with sawdust and wire mesh floor were relatively avoided. Rats slept in the cages with large-particles bedding, but used the other cages for active behaviour such as eating and defecating; furthermore, many rats preferred different cages [with different substrates] during day and night. It is suggested that different behavioural activities may require different cage floor covering. .... Possibly the widely used concept of housing laboratory rats on one type of cage flooring should be abandoned and replaced by a cage concept with different types of flooring to enable the rats to express a more complete behavioural repertoire."

Mice
Blom HJM, Witkam ACP, Schlingmann F, Hoogervorst MJC, van de Weerd HA, Baumans V, Beynen AC 1993 Demonstration of preference for clean versus soiled cages as expressed by laboratory mice. Utrecht, The Netherlands: Utrecht University
Mice in cages with flooring consisting partly of wire mesh and partly of sawdust bedding chose the bedded area for sleeping. They kept their sleeping area clean and deposited almost all their excreta on the wire mesh. When offered a choice between a solid-floored bedded cage area and an area with a wire mesh base, they deposited urine and feces on the mesh.

Hobbs A, Kozubal W, Nebiar FF 1997. Evaluation of objects for environmental enrichment of mice. Contemporary Topics in Laboratory Animal Science 36(3), 69-71
Control animals "spent a mean of 35 min digging in bedding, suggesting that bedding served as an important enrichment device."

Iturrian WB, Fink GB 1968. Comparison of bedding material: Habitat preference of pregnant mice and reproductive performance. Laboratory Animal Care [Laboratory Animal Science] 18, 160-164
"Pregnant mice exhibit a definite preference for a processed sawdust bedding material as opposed to a commercial deodorized cellulose."

Mulder JB 1975. Bedding preferences of pregnant laboratory-reared mice. Behavior Research Methods and Instrumentation 7, 21-22
Pregnant mice invariably preferred aspen bedding over nine other commercially available bedding materials.

Port CD, Kaltenbach JP 1969. The effect of corncob bedding on reproductivity and leucine incorporation in mice. Laboratory Animal Care [Laboratory Animal Science] 19, 46-49
Preweaning mortality was increased when the mice were housed on corncob bedding (22%) when compared with pine sawdust bedding (13%).

Sherwin CM 1996. Laboratory mice persist in gaining access to resources: a method of assessing the importance of environmental features. Applied Animal Behaviour Science 48, 203-214
"By using traverses of shallow water in two experiments, it was determined how laboratory mice defended gaining access to feed, shelter, a conspecific or increased space (Experiment 1), and to feed, a running wheel, enrichments ('toys') or deep sawdust (Experiment 2). In both experiments, the mice continued to gain access to each of the resources several times each day despite having to traverse water, indicating that none of the resources was perceived as a luxury These results indicate that a wide variety of resources were perceived by laboratory mice as important, and suggest that conventional designs of cage which provide only food, water, companionship and a thin layer of sawdust might be inadequate with regards to welfare ... and could lead to suffering."

Sherwin CM 1996. Preferences of individually housed TO strain laboratory mice for loose substrate or tubes for sleeping . Laboratory Animals 30, 245-251
Individually housed mice "preferred to sleep in sawdust [rather than pre-formed tubes] when this was available. The mice slept in the tubes only after the sawdust was removed." The animals showed no preference for shape, opacity or openness of the tubes.

Sherwin CM 1996. Preferences of laboratory mice for characteristics of soiling sites. Animal Welfare 5, 283-288
"These results show that the mice defecated in localized areas and preferred to defecate in areas containing sawdust [rather than on bare plastic floors]. These results support other evidence which indicates that conventional cage designs for mice do not provide a sufficiently complex environment to allow selective soiling behaviour. Such cages might therefore be inadequate with respect to catering for the psychological needs and overall welfare of laboratory mice."

Sherwin CM, Nicol CJ 1996. Reorganising behaviour in laboratory mice with varying cost of access to resources. Animal Behaviour 51, 1087-1093
" Mice preferred to rest in deep sawdust than in scattered food or the tunnels.

Hamsters, guinea pigs and gerbils
Arnold CE, Estep DQ 1994. Laboratory caging preference in golden hamsters (Mesocericetus auratus). Laboratory Animals 28, 232-238
"Most hamsters preferred the solid floored cage with litter, but prolonged experience on wire led to a wire floored cage preference in 40% of these animals. ... Perhaps [many] hamsters find nothing natural about plastic cages with [corn-cob] litter bedding, even though humans think they might make an adequate substitute."

Arnold CE, Gillaspy S 1994. Assessing laboratory life for golden hamsters: social preference, caging selection, and human interaction. Lab Animal 23(2), 34-37
"Hamsters preferred the solid-floor cages with [corn-cob] bedding [over wire-mesh floored cages or solid floored cages without bedding], spending an average of 70% of their time there."

Fullerton PM, Gilliatt RW 1967. Pressure neuropathy in the hind foot of the guinea pig. Journal of Neurology, Neurosurgery and Psychiatry 30, 18-25
Solid-bottom caging is often associated with pressure neuropathies. Evidence suggests that solid-bottom caging, with bedding is preferred by the animals.

Pettijohn TF, Barkes BM 1978. Surface choice and behavior in adult Mongolian gerbils. The Psychological Record 28, 299-303
Both males and females clearly chose to be most frequently on the sand, followed by the wood chip bedding material."

Rabbits
Tamburrino PA, Michonski KJ, Cameron RA 1999. Adaptation of dog kennels for group housing of rabbits. Abstracts of the AALAS [American Association for Laboratory Animal Science] Meeting , 33 (Abstract)
"An increase in rabbit census prompted conversion of dog kennels to rabbit pens. ... The bedding system consisted of a four-inch layer of wood shavings covered with a six-inch layer of autoclaved straw to allow urine to pass through the straw and be absorbed by the shavings. Pens are cleaned weekly with rabbits being moved to an adjacent clean pen. Twelve to 20 week-old female rabbits are housed in five per group on arrival."

Turner RJ, Selby JI, Held SDE, Howells KJ, Eveleigh JR, Wootton RJ 1992. Preferred substrates for penned laboratory rabbits. Animal Technology 43, 185-192
Group-housed does preferred straw or shredded paper and avoided sawdust or wood shavings.

Nesting material

Rats
Bradshaw AL, Poling A 1991. Choice by rats for enriched versus standard home cages: Plastic pipes, wood platforms, wood chips, and paper towels as enrichment items. Journal of the Experimental Analysis of Behavior 55, 245-250
"Most [of the individually tested male] rats preferred cages with wood chips, and paper towels to otherwise identical [barren, wire mesh] cages. .... Plastic pipes ... were not preferred by most animals. Paper towels created no [husbandry routine] problems and appeared to be useful as enrichment items. Paper towels provided an opportunity for a significant species-typical behavior, nest building, and rats in the present study immediately constructed nests that they occupied during most observations."

Jegstrup IM, Vestergaard R, Vach W, Ritskes-Hoitinga M 2005. Nest-building behaviour in male rats from three inbred strains: BN/HsdCpb, BDIX/OrIIco and LEW/Mol. Animal Welfare 14, 149-156
It was demonstrated in three inbred strains [BN, BDIX, LEW] of pair-housed male rats that naïve animals who never had access to any kind of nesting material do build nests if the correct stimuli are provided. The animals was housed in 48 x 38 x 20 cm large cages with aspen wood chips bedding, each furnished with a roofed wooden nest box measuring 28.5 x 20.5 x 12.5 cm. The box had two entrance holes with a 6 cm diameter on two different sides. Aspen wood wool and autoclaved straw were placed outside the box. The nest was removed and the box along with the two rats transferred to a new cage every two weeks. Additional fresh bedding material and straw was added twice a week, and wood wool once a week. The wooden nest box was machine-washed every two months. All animals built a new nest in the box in the two week period between the cage changing procedure. The animals began with the removal of all aspen bedding material form the nest box. They continued with the collection of straw and wood wool, forming a mat inside the empty nest box. This mat could be several centimeters thick and formed into a cup-shape nest. The actual construction of the nest consisted of fibers of both straw and wood wool, with straw forming a larger part of the nest structure itself.

Manser CE, Broom DM, Overend P, Morris TH 1998. Investigation into the preference of laboratory rats for nest-boxes and nesting materials. Laboratory Animals 32, 23-35
"Rats were exposed to six commercially available nesting materials and those consisting of long paper strips were most preferred."

Manser CE, Broom DM, Overend P, Morris TH 1998. Operant studies to determine the strength of preference in laboratory rats for nest-boxes and nesting material. Laboratory Animals 32, 36-41
"It was shown that the rats would carry out more work to reach a nest-box, with or without nesting material, than to reach an empty cage."

Nolen GA, Alexander JC 1966. Effects of diet and type of nesting material on the reproduction and lactation of the rat. Laboratory Animal Care [Laboratory Animal Science] 16, 327-336
Reproductive "improvements due to paper nesting material were dramatic. The 10.8 pups per litter weaned by mothers nested in paper was very significantly higher than the 7.0 pups weaned by those with wood shaving. A more sensitive measure of the improvement was the lactation index [percentage of number of pups weaned that are alive at day 5] , which showed a 76% increase for paper-nested mothers over wood shaving-nested mothers. ... Females nested in shavings simply 'dried up'; those nested in paper had full milk glands." Access to paper nesting material reduced infant mortality from 45 to 3%. "We suggest that the use of shredded paper for nesting, which incidentally makes a nest similar to that of the wild rat, allows the female with her young to burrow and insulate themselves from disturbing environmental factors, thus enhancing the mother's feeling of security."

Norris ML, Adams CE 1976. Incidence of pup mortality in the rat with particular reference to nesting material, maternal age and parity. Laboratory Animals 10, 165-169
Better breeding results were obtained when animals had access to woodwool instead of paper tissue as nesting materials. With paper tissues for nesting purposes 60% of the young were lost compared with 18% with woodwool.

Oley NN, Slotnick BM 1970. Nesting material as a reinforcer for operant behavior in the rat. Psychonomic Science 21, 41-43
Rats will readily work for the acquisition of nesting material. "Paper strips serves as an adequate reinforcer. .. Prior to parturition, only a small daily nest was built and barpressing occurred only in the dark part of the lighting cycle. Following parturition, barpressing for nesting material greatly increased.

Ras T, Van de Ven M, Patterson-Kane EG, Nelson K 2002. Rats' preferences for corn versus wood-based bedding and nesting materials . Laboratory Animals 36, 420-425
"Data from 10 rats with no prior nesting material experience suggested that paper strip was preferred over cornhusk."

Mice
Armstrong KR, Clark TR, Peterson MR 1998. Use of cornhusk nesting material to reduce aggression in caged mice. Contemporary Topics in Laboratory Animal Science 37(4), 64-66
The provision of cornhusk reduced aggressive interactions by offering subordinate animals cover and escape routes.

*Barley J, Francis R, Van Loo P, Walsh M, Weilenmann R, Reinhardt V 2006. Do mice benefit from prefabricated dwellings? A discussion by the Laboratory Animal Refinement and Enrichment Forum. Animal Technology and Welfare 5, 13-15
"I conclude from our discussion that commercial prefabricated dwellings for mice are useful only if they are made of GLP-accepted material that the animals can readily gnaw and convert into nesting and bedding material. Since mice have a biologically inherent need and show a strong preference to build their own nests, it is advisable to provide the animals with suitable nesting material, such as paper tissues or re-used autoclaved paper pulp products, rather than enclosed plastic structures that are not only relatively expensive but also require some nesting material to make them habitable for the animals."

Bazille PG 2000. The problem with nestlets and Athymic Nudes. AALAS [American Association for Laboratory Animal Science] 51st National Meeting Official Program , 123 (Abstract)
"A colony of Hsd:Athymic Nude-nu mice was found to have an increased prevalence of conjunctivitis. .. It was theorized, because Athymic Nude mice lack the normal fur, i.e., guard hairs, and eye lashes, the fibers from nestlets can easily become embedded in the conjunctiva and periorbital tissues of the eye" predisposing the eyes to chronic irritation and subsequent infection. .. After treatment, conjunctivitis resolved in the mice housed without nestlets, but improved only slightly for the mice housed in boxes with nestlets present. As a result of these findings, Athymic Nude mice are now given paper towels as cage enrichment instead of nestlets."

Coviello-Mclaughlin GM, Starr SJ 1997. Rodent enrichment devices - evaluation of preference and efficacy. Contemporary Topics in Laboratory Animal Science 36(6), 66-68
The mice preferred cotton nestlets and cardboard rolls over wooden block and commercial toys.

Eskola S, Kaliste-Korhonen E 1999. Aspen wood-wool is preferred as a resting place, but does not affect intracage fighting in male BALB/c and C57BL/6J mice. Laboratory Animals 33, 108-121
"The nesting material [aspen wood-wool] used in this study did not cause any adverse effects on the animals, as determined by both behavioural and physiological observations. On the other hand, it might have a positive value for the animals; the material was clearly more preferred as a resting place than was conventional bedding and the animals did manipulate it during their active periods. These behavioural findings suggests that nesting material may improve the cage environment of laboratory mice."

Hawkins P 1999. Working together to improve rodent well-being. Lab Animal 28(2), 30-32
Highlights of the RSPCA/UFAW Rodent Welfare Group reports. "Barn-dried, first-cut hay is pliable enough for the transgenic mice to construct ball-shaped nests, connected chambers, and runs (paper materials are not suitable).

Lee CT 1972. The development of nest-building behaviour in inbred mice. Journal of General Psychology 87, 13-21
Both, females and males will build nests when they have access to appropriate nesting material.

Olsson IAS, Dahlborn K 2002. Improving housing conditions for laboratory mice: a review of 'environmental enrichment'. Laboratory Animals 36, 243-270
"We have reviewed 40 studies carried out between 1987 and 2000, in which preferences as well as the effect of housing modifications have been studied. Mice will work for access to nesting material and make use of this material to make nests in which they rest. They prefer a more complex cage to the standard cage and will also work for access to cages with shelter and raised platforms."

Porter G, Lane-Petter W 1965. The provision of sterile bedding and nesting materials with their effects on breeding mice. Journal of the Animal Technician Association [Animal Technology] 16, 5-8
Mice nested in shredded paper had a lower pre-weaning mortality than those nested in woodchips.

Roper TJ 1975. Self-sustaining activities and reinforcement in the nest building behaviour of mice. Behaviour 59, 40-57
Mice will readily work in order to get nesting material. "It is concluded that gathering is at least to some extent autonomously controlled, and that it is a weak positive reinforcer."

Scharmann W 1991. Improved housing of mice, rats and guineapigs: a contribution to the refinement of animal experimentation. Alternatives to Laboratory Animals [ATLA] 19, 108-114
"Like hamsters, mice of most strains are active nest builders. Therefore, they should be offered autoclaved materials, such as hay, straw or cellulose paper." By making the material available on the lid of the cage, the "mice will drag the straw or sheets through the bars of the lid, break up the material into small pieces and build a nest from it."

Sherwin CM 1997. Observations on the prevalence of nest-building in non-breeding TO strain mice and their use of two nesting materials. Laboratory Animals 31, 125-132
"Within 2-3 min of the nesting materials being placed in the cages, many mice had pulled the paper towel from the pot into the main cage, investigated, chewed and manipulated the sheet. ... Thirty-six of the mice constructed nests during the first dark phase after the materials had been placed in the cage - the remaining three mice constructed nests during the following 48 h.... The most frequently constructed nest was build under the feeder and comprised a mixture of both the [cellulose] fibre and the paper. ... Two [of 39] mice constructed their nest entirely of paper. ... Providing paper towels is an inexpensive and practical means of environmental enrichment for non-breeding, laboratory mice. ... The function of non-maternal nests may be directly related to welfare [e.g. thermoregulation, seclusion] which is negated in the absence of suitable nesting materials. ... Providing a pre-formed nest-box as a form of environmental enrichment may be inappropriate" because mice are not highly motivated to use them for sleeping. "It seems that manipulable material [e.g., paper] is preferred to a rigid pre-formed shelter/nesting area [e.g., empty pots, tubes]."

Smith GD, Hoffman WP, Lee EM, Young JK 2000. Improving the environment of mice by using synthetic gauze pads. Contemporary Topics in Laboratory Animal Science 39(6), 51-51
"The mice with gauze pads preferred to rest on them. In addition, these mice showed a statistically significant reduction in food consumption, but their body weights and weight gains did not differ from those of animals without gauze pads."

Van de Weerd HA, van Loo PLP, van Zutphen LFM, Koolhaas JM, Baumans V 1997. Preferences for nesting material as environmental enrichment for laboratory mice. Laboratory Animals 31, 133-143
"All [group-housed] mice showed a clear preference for cages with [paper] tissues or [paper] towels as compared to paper strips or no nesting material, and for cages with cotton string or wood-wool as compared to wood shavings or no nesting material. Paper-derived materials were preferred over wood-derived materials, although the results also suggest that the nature (paper or wood) of the nesting material is less important than its structure, which determines the nestability of the material." Both sexes built nests and there was no sex difference in preference for nesting materials. ... "10-20% of the time budget was spent on manipulation of the nesting material during day or night. ... Nesting material may be a relatively simple method to contribute to the well-being of laboratory mice."

Van de Weerd HA, van Loo PLP, van Zutphen LFM, Koolhaas JM, Baumans V 1998. Strength of preference for nesting material as environmental enrichment for laboratory mice. Applied Animal Behaviour Science 55, 369-382
"On average, the 47 mice tested spent significantly more time in the cage with the nesting material [paper towel or tissue] (more than 69% of their total time, whereas less than 25% of their time in the cage with the nest box [perforated metal or clear perspex box]. In the second experiment the preferred nesting material (tissues) was placed in a cage with a grid floor (previously found to be avoided) and the nest box (perforated metal) was placed in another cage, connected to the first, with a solid floor covered with sawdust bedding material. In this experiment, 24 female mice were tested and on average spent more than 67% of their time in the cage with the nesting material, despite the presence of a grid floor. Thus, it was concluded that providing a cage with nesting material (in addition to bedding) may be essential for the well-being of laboratory mice."

Van de Weerd HA, van Loo PLP, van Zutphen LFM, Koolhaas JM, Baumans V 1997. Nesting material as environmental enrichment has no adverse effects on behavior and physiology of laboratory mice. Physiology and Behavior 62, 1019-1028
"Throughout the study all mice used the nesting material to build nests and mice from enriched conditions weighed more than mice housed under standard conditions, although the latter consumed more food."

Hamsters and gerbils
Hawkins P 1999. Working together to improve rodent well-being. Lab Animal 28(2), 30-32
"When supplied with hay, gerbils become very active and chop it to a uniform size, building a structure resembling a bird's nest.

Jansen PE, Goodman ED, Jowaisas D, Bunnell BN 1969. Paper as a positive reinforcer for acquisition of a barpress response by the golden hamster. Psychonomic Science 16, 113-114
A hamster will readily work in order to get access to nesting material.

McClure DE, Thomson JI 1992. Cage enrichment for hamsters housed in suspended wire cages. Contemporary Topics in Laboratory Animal Science 31(4), 33 (Abstract)
"Golden Syrian hamsters (n=99) were housed individually in suspended wire cages so that spilled food and excreta could be removed. After 8 days, the hamsters developed bizarre aggressive behavior which consisted of growling, hissing, aggressive posturing toward humans, destruction of water bottle rubber stoppers, and attacking objects introduced into the cage. Many developed inappetence which progressed to anorexia, depression, and unresponsiveness. ... When cotton nestlets were provided to all of the hamsters, their appetite and responsiveness improved, but the aggressive behavior remained unchanged. The nestlets were replaced by a 13-cm length of 5.5-cm-diameter polyvinyl chloride pipe (PVC). The water bottles were replaced by an automatic watering system. After adding the PVC, the aggressive behavior diminished in 3 days and was unnoticeable in 14 days. In conclusion, when these hamsters were provided with nesting material their well-being was improved as indicated by resolution of inappetence and depression. Providing the PVC apparently resolved the aggressive behavior problem by providing a means for seclusion in addition to functioning as a burrow and as a toy."

Rabbits
Canali E, Ferrante V, Todeschini R, Verga M, Carenzi C 1991. Rabbit nest construction and its relationship with litter development. Applied Animal Behaviour Science 31, 259-266
"The results of this study have indicated the importance of prenatal behavior, particularly the construction of a straw nest, on the growth and survival of the young."

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Patterson-Kane EG 2003. Shelter enrichment for rats. Contemporary Topics in Laboratory Animal Science 42(2), 46-48
"Nest boxes are a simple and effective form of environmental enrichment. Rats accept a wide range of nest-box types but have the strongest...preference for enclosed, opaque, thermoplastic boxes. ... Tubes have proven a relatively ineffective enrichment for rats. ... Nesting paper may substitute for nest boxes to some extent, but nest boxes are preferred to nesting paper when the two are offered separately. .... All rats in standard laboratory caging should be provided with a nest box. This proviso should be considered a minimum husbandry requirement rather than a benevolent enrichment. As rat nest boxes are not commercially available at this time, laboratories should consider constructing their own, using the simple designs presented in this study."

Patterson-Kane EG, van de Ven M, Ras T 2001. Enrichment of laboratory rat caging. AALAS [American Association for Laboratory Animal Science] 52nd National Meeting Official Program , 106 (Abstract)
"Rats show strong and consistent preference for nest-boxes, and particularly Perspex nest-boxes with small entrance."

Van de Weerd HA, van Loo PLP, van Zutphen LFM, Koolhaas JM, Bauman V 1998. Preferences for nest boxes as environmental enrichment for laboratory mice. Animal Welfare 7, 11-25
"Individual mice prefer a cage with a nest box and avoid cages without one. ... In general, the preferred nest boxes were those consisting of perforated metal or grid metal."

Van Loo PLP, Blom HJM, Meijer MK, Baumans V 2005. Assessment of the use of two commercially available environmental enrichments by laboratory mice by preference testing. Laboratory Animals 39, 58-67
All three strains of mice showed a significant preference for the paper box. The paper box was much lighter [20 g] than the plastic box [95 g]. This allowed the mice to move the paper box around, manipulate it and change the position of the entrance within the cage. The plastic box seemingly was too heavy for such maneuvering and, hence, never changed its place. The mice also gnawed the paper box, occasionally nibbled an extra hole in the side, or shredded part of the box, using the shreds to strengthen their nest. They could not do this with the plastic box. All groups of mice slept inside the paper box but they never slept in the plastic box. If they chose to sleep in the cage that contained the plastic box, they did so in the sawdust outside the box. When tissue paper was provided, the mice dragged the material into the paper box and built a nest, but they never combined this nesting material with the plastic box.

Ward GE, DeMille D 1991. Environmental enrichment for laboratory mice (Mus musculus) . Animal Technology 42 , 149-156
"It must be considered as doubtful whether the current bland and unenriched laboratory animal cage environment is either sufficient or able to fulfill the legitimate requirements of this species." Water bottles containing sawdust provide effective cage enrichment for laboratory mice. They are used as refuges and climbing areas and also selectively as latrines or remain clean to be used as nests.

Rabbits
Heath M, Stott E 1990. Housing rabbits the unconventional way. Animal Technology 41, 13-25
A well-tested, species-adequate housing arrangement for rabbits is described. The rabbits are either group housed or in individual or paired floor pens. In both groups the rabbits are allowed social interaction, exercise, privacy, and an environment which occupies their attention and allows them to express more of their natural behaviour. Wooden nest boxes mounted 10cm above the ground are added to the pens as well as small branches for gnawing and scenting.

Mouse house/Igloo

Biczak M, Pellecchia D 2002. Environmental enrichment for rodents and rabbits. TriBranch Symposium 2002 , unpublished poster presentation
Access to a Mouse Igloo probably reduced anxiety and "has also helped to decrease mortality" in transgenic mice. Placing a Mouse Igloo and a tunnel into the cage of group-housed male mice abolished fighting.

Key D 2004. Environmental enrichment options for laboratory rats and mice. Lab Animal 33(2), 39-44
"The most important initiatives in providing environmental enrichment is group housing, providing nesting material, and a nest box. Pictures and description of various nest boxes are given such as skinner boxes, the mouse house, the mouse igloo, the Shepherd Shack insert and disposable nest boxes, called des Res houses. Details of improved cage design as in the 'Rat Hotel' and the 'Novo Nordisk Cage' are given.

Key D, Hewett A 2002. Developing and testing a novel cage insert, the "Mouse House", designed to enrich the lives of laboratory mice without adversely affecting the science. Animal Technology and Welfare 1, 55-64
"The 'Mouse House' should satisfy requirements for both environmental enrichment and legislation suggesting the use of cage inserts that allow privacy for the animal but facilitate observation."

Tunnels, tubes and burrows

Rodents
Foulkes A 2004. Do laboratory rats benefit from more cage space? AWI Quarterly 53(3), 18-19
The porphyrin scores were significantly higher in rats housed in small or large cages that were barren than in rats housed in small or large cages that were furnished with a PVC tube. The lowest porphyrin scores were found in rats living in the large PVC tube-furnished cages. This housing environment was the least stressful one of the four test situations. The animals stress status was reflected in their food consumption with rats living in barren cages eating much more food and gaining significantly more weight than rats living in the enriched cages. Rats kept in the typical, barren standard cages very often become obese. The present findings indicate that this problem is related to stressful living conditions, similarly to obesity in modern people living in stressful environments." Laboratory rats do not benefit from more cage space, unless the space is provisioned with proper enrichment such as a PVC tube. Being confined in a small standard cage is a much more stressful experience for rats than being confined in a larger cage furnished with a PVC tube. Access to a PVC tube reduces a rats stress level in a small cage, but the stress is still much higher than in a large cage with PVC tube."

Galef JrBG, Sorge RE 2000. Use of PVC conduits by rats of various strains and ages housed singly and in pairs. Journal of Applied Animal Welfare Science 3, 279-292
"Adult male Long-Evans rats rarely entered PVC conduits unless housed in pairs. ... Adult male Sprague-Dawley rats entered PVC conduits only during the illuminated portion of the day-night cycle and only if housed on shelves exposed to direct overhead illumination. Both juvenile rats and female rats made extensive use of PVC conduits throughout the day-night cycle."

McClure DE, Thomson JI 1992. Cage enrichment for hamsters housed in suspended wire cages. Contemporary Topics in Laboratory Animal Science 31(4), 33 (Abstract)
"Golden Syrian hamsters (n=99) were housed individually in suspended wire cages so that spilled food and excreta could be removed. After 8 days, the hamsters developed bizarre aggressive behavior which consisted of growling, hissing, aggressive posturing toward humans, destruction of water bottle rubber stoppers, and attacking objects introduced into the cage. Many developed inappetence which progressed to anorexia, depression, and unresponsiveness. After adding the PVC, the aggressive behavior diminished in 3 days and was unnoticeable in 14 days. In conclusion, when these hamsters were provided with nesting material their well-being was improved as indicated by resolution of inappetence and depression. Providing the PVC apparently resolved the aggressive behavior problem by providing a means for seclusion in addition to functioning as a burrow and as a toy."

Moons CPH, Van Wiele P, Ödberg FO 2004. To enrich or not to enrich: Providing shelter does not complicate handling of laboratory mice. Contemporary Topics in Laboratory Animal Science 43(4), 18-21
"Results indicate that EE [environmental enrichment] in the form of sheltering objects [PVC conduits] does not complicate catching or handling mice and that allowing access to enrichment in the laboratory cage, which has been shown to have positive effects on welfare, does not interfere with the management or cost of laboratory animals." The provision of shelter "reduces the time needed to catch and handle NMRI mice."

Sherwin CM 1996. Preferences of individually housed TO strain laboratory mice for loose substrate or tubes for sleeping . Laboratory Animals 30, 245-251
Individually housed mice "preferred to sleep in sawdust [rather than pre-formed tubes] when this was available. The mice slept in the tubes only after the sawdust was removed." The animals showed not preference for shape, opacity or openness of the tubes.

Smith MM, Hargaden M 2001. Developing a rodent enrichment program. Lab Animal 30(8), 36-41
The authors describe methods to establish a program for selecting, monitoring, and testing environmental enrichment devices for the rodents in their pharmaceutical facility.

Würbel H, Chapman R, Rutland C 1998. Effect of feed and environmental enrichment on development of stereotypic wire-gnawing in laboratory mice. Applied Animal Behaviour Science 60, 69-81
Enrichment significantly reduced stereotypic wire-gnawing in pair-housed male mice by 40%, presumably as a consequence of the cover provided by the cardboard tubes. This is substantiated by observations that the tubes were used as a place to retreat upon disturbance as well as for resting. As a consequence the animals showed more resting and less grooming in cages containing a cardboard tube-shelter.

Waiblinger E 2004. Refinement of gerbil housing and husbandry in the laboratory. The Three Rs at the Beginning of the 21st Century: Proceedings of the Fourth World Congress on Alternatives and Animal Use in the Life Sciences. Balls M, Firmani D and Rowan A, eds, 163-169. ATLA 32, Supplement 1.
An artificial borrow system for caged gerbils is described. Access to the system reduced stereotypic digging. "Laboratory gerbils should be offered a burrow, which must have an access tube, be opaque and undisturbed."

Wiedenmayer C 1997. Stereotypies resulting from a deviation in the ontogenetic development of gerbils. Behavioural Processes 39, 215-221
The provision of an artificial external burrow reduces stereotypic digging.

Rabbits
Howard B, Wortley M, Kay R 1999. Rabbit enclosures - structure and space. Animal Technology 50, 156-157
"When a screen was hung from the top of the pen near one end, raised approximately 10 mm above the surface of the litter, all rabbits in the pen spent much of their time in the small shielded area. Provision of tubes within which rabbits can hide together with the hanging screen produced an environment in which aggression (groups of 4 or 6 [probably female] rabbits) was minimised. In contrast, providing a shelf on which a rabbit could sit had no effect on overall levels of aggression in the pen, although dominant rabbits did tend to monopolise it."

Raje SS, Stewart KL 1997. Group housing for male New Zealand White rabbits. Lab Animal 26(4), 36-37
The animals preferred a 18" PVC pipe as hiding place.

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