Housing and husbandry: Cat

Government regulations and scientific guidance documents from both Europe and the United States provide detailed information about the requirements and recommendations for housing cats used for research in ways that take into account their social, physiological and behavioural needs [1-3]. This page builds upon this information to formulate what can be considered ‘best practices’ in laboratory cat welfare with an emphasis on housing and enrichment.

The domestic cat (Felis silvestris catus) evolved from the African wild cat (Felis silvestris libyca), which is largely a solitary, territorial hunter [4]. Research has shown that although domestic cats too may live singly, they are also found in large socially structured groups [5]  with a high degree of cooperation. In contrast with dogs, which are social pack animals, cats have not been forced by selection pressures to develop as wide a range of social communication repertoires, formal group structures, or mechanisms for diffusing or reconciling after conflicts [4-6]. For cats, the primary mechanism for avoiding conflict is social distance [7], which means that housing arrangements must provide adequate space for cats to control their interactions with conspecifics (members of their own species), including refuges where they can hide and rest out of sight. Conflicts tend to arise over important resources, such as access to food, resting places, and litter trays. Accordingly these must be provided in sufficient quantity and in different locations throughout the enclosure to allow easy access by all cats and limit opportunities for guarding and monopolisation of resources [4].

Cats that are well socialised are less stressed and easier to handle, which is beneficial not only to the cat, but also to handlers, and can have implications for the overall validity of study results. In cats, friendliness to humans is, in part, genetically inherited from the father. It has been demonstrated that kittens from ‘friendly’ fathers tend to react with greater boldness when faced with unfamiliar people and novel objects [8]. Furthermore, the development of social behaviour in cats is profoundly affected by early socialisation with people and conspecifics. The sensitive period for kitten’s socialisation to humans and possibly to conspecifics is two to seven weeks of age [9]. Socialisation to humans is especially crucial during this period, and continues to be important throughout life, for their development of friendly relationships to humans.

Animals that receive early handling by humans tend to develop more rapidly, and show a general reduction in fearfulness [10,11]. These effects are likely to depend on a number of factors, including the type, frequency and duration of handling, as well as the number of different people involved in the handling [12]. It is recommended that young kittens are handled gently and spoken to on a daily basis [4]. In addition to providing exposure to people and other cats, it is important to habituate kittens to environmental conditions, routine husbandry, and experimental procedures likely to be encountered during their daily lives [3]. In most cases, positive refinforcement (e.g. rewarding with treats) can be used during training sessions to induce voluntary cooperation [13-15]. All of this has implications for the careful selection of suppliers of cats, and the care of kittens born within research colonies. Early weaning of kittens (≤12 weeks) is associated with a higher probability of aggressive behaviour and stereotypies; weaning at 14 weeks is recommended [16].

Space

The most basic aspect of housing is the amount of space available to each animal. Minimum space requirements for the housing of cats in laboratories in Europe are given in Annex III of Directive 2010/63/EU and Appendix A to the Council of Europe Convention ETS 123. When developing an enrichment programme, increasing the use of vertical space and enhancing the complexity of the environment will do more to improve welfare than simply increasing floor space [17,18]. Enclosures should be of sufficient height to allow caretakers to walk in, as this makes it easier to interact with the cats and conduct maintenance activities [19].

Grouping

It is recommended that cats be housed in socially compatible, stable groups. The recommended number of cats that should be housed together in a primary enclosure varies between five and 25 [20,21]. 

Cats that are unable to adapt to group housing may do better in a pair housing arrangement. If a cat proves unable to live harmoniously with conspecifics, he or she should be housed singly with optional visual access to other cats [4], and particular attention should be paid to providing social enrichment through additional daily contact with people [3]. If research requires single housing for periods of time, cats can often be returned to social groups in between trials or for a period each day [22,23].

The success of group housing depends on the social compatibility of the cats, their ability to manage distance from one another, and easy access for all group members to comfortable resting places, food, water, and litter trays. In addition, housing should be structured to provide mental stimulation and allow cats to express a wide range of normal behaviours including climbing, jumping, stretching, exploring, playing, chasing, and hiding [20,25]. The floor of enclosures should be smooth, non-slip and easy to clean [3,4]. Wire mesh or grid floors are uncomfortable for cats, and may cause injury to their paws or tails [4].

Enclosure furniture

Of particular importance is the availability of elevated and vertical structures such as platforms, shelves, raised walkways, resting boxes, hammocks, and cat ‘trees'. Steps, climbing poles, and slanted walkways should be available to help cats reach higher level structures [4]. Cats prefer and spend more time in elevated areas than on the floor [24], and because many cats are not well-adapted to living in close proximity to one another, having a variety of resting and hiding places provides one way for cats to maintain distance and avoid conflict, which in turn minimises stress [19]. Scratching posts, cat trees, and carpeted structures provide opportunities for the natural behaviours of claw sharpening and scent marking [24].

Cats prefer resting areas that are warm, dry, protected on one or two sides, and situated in corners or on the edges of an enclosure; this provides them with a vantage point from which to observe without the threat of being approached from behind [22,26,27]. There should be a sufficient number of resting areas for each cat, as cats may want to rest alone, and they will rest in litter trays if no other areas are available [4,24,27,28].  When litter trays are used as rest areas it not only creates a hygiene concern, it forces other cats to eliminate in undesirable locations [25].

Comfortable bedding should be provided in resting areas, and research has shown that cats prefer polyester fleece over other materials [29]. Cats that sleep on soft surfaces have longer periods of sleep than those who sleep on hard surfaces, which has been interpreted as a sign of an enhanced sense of security [28].

A minimum of one litter tray for every two cats in the enclosure is recommended. Toileting in unexpected or undesirable places can be an indicator that there are not a sufficient number of litter trays available [4,20,30]. Prompt investigation of unusual toileting behaviour is necessary as it can also be symptomatic of a urinary tract infection. Some cats will not use a tray if it has already been soiled, so trays need to be cleaned a minimum of once per day, and ideally spot cleaned multiple times per day [4]. Cats may have preferences for different types of litter or litter trays, and it may therefore be worthwhile to provide a variety of toileting options [13,25]. Litter trays and feeding areas should be located at least 0.5m apart, and locations for these functions should not be interchanged [3].
 

Domestic cats form matrilineal social groups, and most females will remain in the same social group for life. Unneutered females can be housed in groups, as can neutered cats of both sexes. Whole males can be successfully housed together (though this will require special care) [3], or with neutered cats of either sex [19,24]. One strategy is to house cats based on maternal grouping when possible, with male and/or female cats being neutered at six months of age [13,29]. Due to the territorial nature of cats, the re-grouping or introduction of new cats to the colony should be done as infrequently as possible, but when necessary, it should be undertaken gradually and with great care (see Rochlitz [25] for a potential means of introduction) [31]. Cats that re well socialised to other cats are much easier to integrate, so this is an important part of their preparation for group living in later life. Environments which provide a choice of resources will facilitate integration of cats new to a group.

Social stress in all pair- or group-housing situations should be monitored on a regular basis (at least weekly) using an established behavioural and/or physiological stress scoring system [3;32].

Daily handling by people is critical to the early socialisation of kittens, but people are also a rich source of stimulation for juvenile and adults cats, particularly for those kept in a relatively restricted environment [22]. Consistency and predictability of the type of interaction or handling are important factors in the success of cat-human interaction and for the psychological wellbeing of cats [31,33,34]. As stated by Rochlitz, “the caregiver is the most important determinant of a cat’s welfare, and group-housing in enriched environments cannot substitute for individual human care and attention" [35]. In order to ensure the highest level of welfare, caregivers should like cats and be knowledgeable about them. Periods of time each day that are not part of normal maintenance activities should be set aside for interaction between cats and their caregivers [23,35,36].

Social interaction with people [36] and conspecifics are important aspects of environmental enrichment, but there are numerous other strategies that can be employed to enhance the welfare of laboratory cats [34,37,38].

Goals of environmental enrichment include:

• Increased diversity of species-specific behavious.
• Reduced frequency of abnormal, unhealthy behaviours (stereotypies, e.g. excessive grooming).
• Increased positive utilisation of the environment.
• Facitatation of agency (choice and control over behaviour and environment).

Increasing environmental complexity is important for cat welfare, but it should not be assumed that providing certain enrichment items has a positive effect [34]. Environmental enrichment should be evaluated to ensure that it is beneficial to welfare; see [32] for a review of methods to assess the welfare of confined cats.

Cats housed in enriched environments that facilitate their agency and ability to perform species-specific behaviours such as perching, hiding and regulation of body temperature have higher welfare than cats in unenriched environments [39,40,41,42].

Cats exhibit individual preferences for different enrichment types [43]; providing a diversity of enrichment is recommended. The preferences of FIV-positive felines does not differ from FIV-negative cats [43].

Toys 

Cats enjoy a variety of toys, but prefer those that move, possess characteristics of prey, contain catnip, or have complex surface textures [43,44]. Toys that allow cats to move through all phases of the hunting sequence (i.e., chase, pounce, capture, consummatory behaviours) are potentially more satisfying to cats than those that do not [34]. Toys should be rotated frequently, as novelty is important to cats, and they quickly become bored if a toy is always available. Simple objects such as large paper bags and cardboard boxes can be added to the enclosure intermittently to encourage play and exploration [34]. Most cats play alone, rather than in groups, so the enclosure must be of sufficient size to ensure that cats can play safely without disturbing others [4].

Feeding methods

Natural feeding behaviours in cats include locating, capturing, killing, and processing food. Employing feeding devices (either commercial or homemade) that allow cats to forage and perform a range of natural behaviours to obtain food has been reported to improve some aspects of physical welfare [45], though psychological and behavioural benefits have, at this stage, only been reported anecdotally; see [34] for pictures and descriptions for some of these devices. Rochlitz suggests that consideration should be given to providing containers of grass for cats to chew, as this is thought to help eliminate fur balls (trichobezoars) [35].

Sensory stimulation

Visual stimulation is important to cats, and when given the opportunity, most will spend a great deal of time gazing out windows that overlook interesting environments. Access to windows [4,13,27] and outdoor runs [34,35] have been reported as potential means of providing visual stimulation. When this type of access to the outside world is not possible, employing videos containing wildlife and conspecifics as a form of visual stimulation has been reported as an alternative strategy [46]. Although it has been demonstrated that cats will watch these types of projected images, Ellis cautions that providing stimulation in a situation where the cat is unable to interact with the source of the stimulation (e.g., laser pointers, objects on TV or on the other side of a window) may create frustration in some animals [34].

Olfactory communication is important to cats, and they have a well-developed sense of smell. Providing surfaces for scratching allows cats to communicate with conspecifics via scent glands located between their digits. Many cats also enjoy the smell of catnip and will interact with the dried herb itself, or toys impregnated with the herb, by sniffing, pawing, and playing [47]. Sensitivity to catnip is inherited, and only 50 to 70% of cats will react to its odour [34,48].

Related to olfactory stimulation is the nascent use of synthetic pheromones to enhance feline welfare. As reported by Ellis, Feliway (CEVA) has been shown to reduce anxiety and related behaviours, and Felifriend (CEVA) has been demonstrated to promote positive social interactions (between cats and humans, as well as between conspecifics) [34]. Use of synthetic pheromones may be useful when dealing with anxious or fearful cats [49], or during the regrouping or introduction of new cats into an existing colony [52] (see [50] and [51] for reviews of the benefits of pheromones to some aspects of cat behaviour).

Aversive odours should be considered and avoided; the use of strongly scented cleaning agents, particularly those with citrus scents, may be a cause of chronic stress to confined cats [53].

There are limited studies into auditory enrichment for cats, but there is evidence that cat prefer species-appropriate music to music intended for humans [54]. External noise levels should be kept to a quiet conversational level and sudden noises should be avoided [40]. 

• Desforges E (2021). Challenges and Solutions Surrounding Environmental Enrichment for Dogs and Cats in a Scientific Environment Animals, 11(10): 2980. doi: 10.3390/ani11102980
• Rochlitz I (2015). Cats. In: Comfortable Quarters for Laboratory Animals, 10th edition. Animal Welfare Institute. 
• Bradshaw JWS et al. (2012) The Behaviour of the Domestic Cat, 2nd Edition. CABI.
• Rochlitz I (2000) Recommendations for the housing and care of domestic cats in laboratories. Lab Animal 34(1):1-9. doi: 10.1258/002367700780577939.