Widely Used, Often Overlooked: Rabbits are among the most widely used laboratory animals worldwide — approximately 1 million are used annually across Europe and the USA in research, testing, and education. Despite this, rabbit welfare in research has historically received less attention than rodents or primates. Recent decades have seen significant advances in understanding rabbit behavioral needs and applying refinements to improve their welfare.
~1M
Rabbits used in labs annually (US+EU)
3rd
Most commonly used lab mammal (after mice/rats)
10–12yr
Natural rabbit lifespan
60%
Lab rabbits showing abnormal repetitive behaviors (some studies)
Natural Rabbit Behavior
Understanding natural rabbit behavior is essential for identifying welfare deficits in laboratory housing and designing meaningful refinements.
Key Natural Behaviors
- Burrowing and hiding: Rabbits are prey animals that naturally live in underground warrens. They have a strong drive to hide and feel enclosed
- Locomotion: Rabbits perform characteristic "binkies" — high-speed runs with twists and jumps — as expressions of positive emotional states. They need space for these
- Social behavior: Wild rabbits live in complex social groups. Rabbits are naturally social and benefit from conspecific companionship
- Foraging: Rabbits spend many hours daily foraging for fibrous plant material. Their digestive system requires continuous trickle-feeding of hay
- Cecotrophy: Rabbits consume soft cecotropes (gut-produced droppings) directly from the anus — an essential nutritional behavior often prevented by cage design
Traditional Lab Housing vs. Natural Needs
Traditional rabbit housing — individual small wire cages — fails to meet virtually all natural behavioral needs:
- Too small for running or jumping
- No hiding areas or shelter
- Social isolation from conspecifics
- Wire floors prevent normal locomotion and cause hock sores
- Limited foraging opportunity
Common Welfare Problems in Lab Rabbits
Stereotypic Behaviors
Stereotypies — repetitive, functionless behaviors — indicate chronic welfare compromise. Common in rabbits housed in barren, restricted conditions:
- Bar-biting: Repetitive gnawing on cage bars — indicator of frustration and motivation to escape
- Repetitive head-swaying: Side-to-side head movement — associated with social isolation and spatial restriction
- Polydipsia: Excessive drinking beyond physiological need — associated with boredom and restricted activity
Studies have found stereotypy prevalence of 40–60% in individually housed rabbits in traditional cages.
Physical Health Problems from Inadequate Housing
- Sore hocks (ulcerative pododermatitis): Wire-floor cages cause chronic pressure wounds on hind feet
- Spinal deformities: Insufficient space for normal posture and movement causes musculoskeletal problems
- Dental disease: Insufficient hay/foraging leading to dental malocclusion
- GI stasis: Inadequate fiber intake from restricted hay access causes life-threatening gut slowdown
- Obesity: Restricted movement and high-concentrate diets cause weight gain
Psychological Welfare
Research using cognitive bias testing (affective state assessment) has confirmed that rabbits in impoverished housing show pessimistic cognitive biases — indicating chronic negative emotional states. Rabbits in enriched housing with conspecific companionship show optimistic biases and higher activity levels.
The 3Rs Applied to Rabbit Research
Replacement
- The Draize eye test (instilling test substances in rabbit eyes) has been significantly reduced through validated in vitro alternatives
- Polyclonal antibody production using rabbits can be partially replaced with in vitro methods
- Pyrogen testing (historically done with rabbits) now has validated in vitro alternatives in many applications
Reduction
- Statistical power calculations to minimize animal numbers while maintaining scientific validity
- Tissue sharing between researchers at same facility
- Harmonized study designs reducing duplication across institutions
- Better experimental design reducing wastage from failed experiments
Refinement
Refinement offers the most immediate welfare improvements for rabbits currently in use:
- Pair housing: Pairing compatible rabbits dramatically reduces stereotypies and improves welfare
- Larger, enriched enclosures: Hideboxes, platforms, and adequate run space enable natural behavior
- Solid flooring: Replacing wire floors with solid or mat-covered flooring eliminates hock sores
- Continuous hay access: Hay racks provided at all times support digestive and psychological health
- Positive reinforcement training: Training rabbits to cooperate with procedures reduces stress for both animals and researchers
Housing Improvements: Current Standards
| Standard | Minimum Space (rabbit >3kg) | Key Features |
|---|
| EU Directive 2010/63 | 3500 cm² floor + 40cm height | Group housing recommended; enrichment required |
| US Guide for Care and Use | 0.56 m² (per animal) | Social housing "considered"; lacks EU specificity |
| UK Home Office Code | 3500 cm² + raised platform | Pair/group housing strongly encouraged |
| Best practice (welfare orgs) | >5000 cm² + run access | Pairs, hideboxes, foraging enrichment, solid floors |
Pair Housing Success: Multiple institutions have demonstrated that pair housing of laboratory rabbits is practical, does not compromise experimental results in most research areas, and dramatically reduces stereotypy prevalence and other welfare indicators. The transition requires management attention but is widely achievable.
Pain Recognition and Management
The Challenge of Rabbit Pain Assessment
Rabbits are prey animals that instinctively hide pain — behavioral signs of pain are subtle and easily missed. This has historically led to under-recognition and under-treatment of pain in laboratory rabbits.
Rabbit Grimace Scale
The Rabbit Grimace Scale (RbtGS) was developed and validated by Keating et al. (2012) based on facial action units:
- Orbital tightening (eye closure)
- Cheek flattening
- Nose shape (V-shape)
- Whisker position (forward and bunched)
- Ear position (rotated/folded)
The RbtGS is now widely used in labs and validated as a reliable pain assessment tool. Training staff to use it has significantly improved pain recognition and analgesic use.
Analgesic Protocols
- Preemptive analgesia before procedures reduces pain sensitization
- Multimodal analgesia (combining drug classes) is more effective than single agents
- Rabbits metabolize many analgesics differently than rodents — species-specific dosing critical
- NSAIDs are well-tolerated and effective for many types of post-procedural pain
Recommendations for Institutions
1. Transition all individually housed rabbits to pair or group housing where scientifically feasible
2. Replace wire floors with solid flooring or deep bedding throughout
3. Provide continuous hay access for all rabbits
4. Add hideboxes or tunnel shelters to all enclosures
5. Train all animal care staff in the Rabbit Grimace Scale
6. Implement positive reinforcement training protocols to reduce procedural stress
7. Apply replacement and reduction strategies to minimize rabbit use in pyrogen testing and Draize testing