Environmental Enrichment

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General Policy

In accordance with federal laws and regulations and accreditation standards, this policy describes the program in effect to enhance the immediate environment and promote the psychological well being for laboratory animals housed at the institution or maintained elsewhere under IACUC protocols. Specific provisions for environmental enrichment are described below.

The main goal of an environmental enrichment program is to encourage the expression of species-typical behaviors, such as appropriate social interaction, social structure development, and opportunities for locomotion, manipulation, and feeding. Additionally, such a program should help prevent or reduce abnormal behaviors, including stereotypical movements, self-aggression, and ingestion-related disorders.

Enrichment strategies are developed to be compatible with the animals primary enclosure, the social needs and immediate environment of the animal, and opportunities for physical and cognitive activity. This program is designed on a species level but may be modified to accommodate individual animals or phenotypes, when appropriate.

This policy comprises social interaction, environmental enrichment, special considerations, behavioral intervention, physical restraint and training, exemptions, record keeping, enrichment studies and program assessment.

Specific Provisions

Social Interaction

Social interaction is usually necessary for development of species-typical behavior and communication patterns. Benefits of social interaction include an opportunity for the expression of species-typical social behavior and development of social structure.

a. Social housing is encouraged, particularly for animals that are known to exist in social groups in nature. Whenever possible, animals will be paired or socially housed. Compatible pairs or groups will be developed based on appropriate sex, age, and behavior and in accordance with the protocol.

b. Social housing is not encouraged and will not be performed in instances when scientifically justified or when necessary while animals are recovering from surgery or anesthesia. Animals will not be paired or group housed, or subsequently separated, if the animals are deemed too aggressive to be socialized with each other.

c. Some caging systems are designed to house animals singly. While housed in this environment, animals can see, smell, and hear one another within the room and will be allowed opportunities for social contact whenever possible. To allow for non-contact social enrichment of singly housed animals, animal cages may be positioned so they permit auditory, olfactory, pheromonal, and visual cues from other animals of the same species. In some cases, after veterinary evaluation, an animal may have to be isolated or moved to another room if such positioning is obviously stressful to that individual.

Environmental Enrichment

In addition to an emphasis on social interaction, creating more variety or complexity in the animals immediate environment can also encourage species-typical behaviors and improve psychological well-being. Environmental enrichment can also reduce boredom and isolation stress that may result in abnormal behaviors.
Environmental enrichment can be divided into several categories, including structural, food, sensory, and activity enrichment.

  • Structural enrichment is the addition of novel items into the primary enclosure. Laboratory animals can be encouraged to investigate their environment and express natural behaviors, such as gnawing, rooting, burrowing, stalking, hiding and exploration when structural enrichment items are offered. An enriched environment can also reduce the occurrence of stereotypic or maladaptive behaviors. Enclosures will be supplied with objects and materials that will encourage these natural behaviors.
  • Food enrichment offers novelty to the diet and allows for natural feeding behaviors. Vegetables, fruit, and commercially prepared treats augment nutritional needs and encourage foraging opportunities by allowing animals to have additional control over their environment. Foraging opportunities for the laboratory animal may provide mental stimulation, encourage locomotion and food gathering efforts, and increase time devoted to natural behavior. Animals will be offered species-specific food enrichment in addition to a nutritionally balanced diet for opportunities to express natural feeding behaviors. Care will be taken in the timing of food enrichment to ensure that food treats will not replace the regular diet.
  • Sensory enrichment includes items that promote auditory, visual, and tactile stimulation. Visual and auditory enrichment may be provided to appropriate animal species, especially when social housing is not possible.
  • Animal activity is an integral component of the environmental enrichment program. Activity is also monitored as an indication of well-being. Opportunities for physical and cognitive activity can be provided in the animals primary enclosure or through social housing and exercise.

All enrichment items must be non-toxic, free of sharp edges, and disposable or easily sanitized and durable for reuse. Toys and other materials must be cleaned and sanitized to the same degree as cages in which they are placed, and at least as often as those cages are changed or washed.

Special Considerations

Individual enrichment plans will be designed for animals with special needs. The veterinary staff will evaluate these animals regularly. At a minimum, the individual plan will include the increased presence of animal technicians in the room and a greater variety of environmental enrichment.

The following animals qualify for special attention:

  • Infants and juveniles
  • Animals showing signs of psychological stress
  • Animals housed in isolation due to research circumstances (e.g., immunosuppressed following whole body irradiation or inoculated with Biosafety Level 2 or higher pathogen), veterinary needs (e.g., intensive care following injury or surgery), or behavioral incompatibility with others of the same species

Provisions for juvenile animals are made to encourage the development and maintenance of species-typical social behavior through the exposure of juveniles to adults and/or peers. In order to do this, infants are left with their mothers in social groups until weaning. Juvenile animals are used as specified by the animal protocol and are provided with opportunities to develop normally, using and social interaction with humans and other individuals of the same species, and a variety of environmental enrichments.

The Enrichment Coordinator will be notified if any animal shows signs of psychological distress through behavior or appearance are brought to the attention of. An evaluation of the severity and possible cause of distress will be completed, including a detailed behavioral assessment, housing history, research history, and other information from the animal care staff. Action appropriate to the individual animal and condition will be proposed to the Principal Investigator and, if acceptable, implemented. The individual animal will then be continually monitored. Scientific justification must be submitted to the IACUC if enrichment intervention is not accepted by the P.I., and documented in the individual animal record.

No animal should be housed in social isolation for extended periods of time. In the event animals are removed from their typical housing environment for clinical or intensive care, an animal of the same species may accompany them. This may require that a cage-mate be brought into the isolation area so that individuals may have visual and auditory contact with each other. There may be exemptions to this policy in severe clinical cases or if scientifically justified and approved by the IACUC.

Behavioral intervention

Animals in which an abnormal and pathologic behavior is identified will be evaluated and a specific intervention plan will be made in coordination with the veterinary and research staff. Intervention may include a training plan and, if necessary and scientifically justified, drug therapy to reduce or eliminate the identified abnormal behavior. Detailed behavioral observations will be conducted before, during, and after any intervention to monitor its effect. Intervention will be documented in the individual animal record.


No animals are exempted from all environmental enrichment techniques.
However, some individuals may have restrictions from part of the program due to requirements in the animal protocol or animal health.

Experimental procedures requiring exemptions to this policy must be specifically approved by the IACUC and communicated to the Enrichment Coordinator and appropriate staff members. Activities that are exempt will be re-evaluated on a regular basis to determine if enrichment should be resumed.

Re-evaluation by the Veterinarian is required for exemptions exceeding thirty (30) days. The IACUC will review cases exempted for experimental reasons on a semi-annual basis. Records documenting granted exemptions must be maintained and made available to regulatory and accreditation agencies upon request.

Record Keeping

Records on social interaction, environmental enrichment and behavioral management are kept for each species in the individual animals record. In the event a particular species does not have an animal record (e.g., group-housed rodents and cage cards), documentation of the enrichment plan is described in the enrichment SOP for that species. Records on program development and assessment will be organized and filed by the Enrichment Coordinator and will also be part of the animals medical record.

Enrichment Studies

Detailed behavioral data may be collected as part of the assessment of particular behavioral and management procedures. Additionally, these data may be analyzed to determine the effect of a procedure on the behavior of the animal, as well as the cost and efficiency of the technique.

Program Assessment

In order to monitor the success of this plan, the Enrichment Coordinator will routinely assess the program, to include the following activities:

  • The effectiveness of the environmental enhancement program and its assessment strategies will be evaluated by the IACUC during IACUC semi-annual inspection and review. Feedback from these inspections will be used to further refine or enhance the program.
  • The Enrichment Coordinator will meet with animal care and veterinary staff to review the progress of the program. Items and techniques that are useful, as well as those that are not, will be discussed. Information on animal use and practical issues (cleaning, durability, etc) as well as observations on individual animals, housing conditions and behavior will be covered.
  • The Enrichment Coordinator will also periodically meet with investigators to review current enrichment plans and discuss alternative strategies.
  • The Enrichment Coordinator will maintain a list of references and web links on laboratory animal environmental enrichment. Such a list will be published on a website and communicated to investigators when appropriate.

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