 | Copies of this journal are no longer available for sale, but our other two journals, Society & Animals and the Journal of Applied Animal Welfare Science, are available and subscriptions are quite affordable. They can be ordered online via our secure order page. |
The author describes a cage that she developed and used for over forty years of working with mice. This cage, named the Cambridge Cage, not only meets species-specific needs, but also meets the convenience needs of their caretakers. When compared with conventional cages, the Cambridge Cage provides a less stressful environment. The cage provides opportunity for choices including both warm and cool temperatures, and a com-fortable sleeping and nesting area with low light density and opportunity for social huddling. The design has also resulted in less ammonia in the room air.
It is amazing to me that cage advertisers usually illustrate with pictures of an uninhabited cage, with no bedding. It is only by seeing the resident there as well, that we can have some perception of the animal's reality. Someone with knowledge of ethology can tell, from seeing an inhabited cage just before it is due to be cleaned, a great deal about the individuals' well-being and their struggles to adapt the cage to their needs. We should all know some ethology. It is astonishing that books purporting to give guidance and standards in animal welfare show only perfectly clean, uninhabited cages.
A too often neglected need that mice demonstrate is a need for tactile comfort. Isolation is stressful for mice. One evidence of this is their "piling behavior." Even when large numbers of mice are stored together, they huddle and group beneath any shelter they can find. They do this even in warm rooms, which signifies a need for tactile comfort.
Anthropomorphism can be a short-cut to understanding, and quite a legitimate scientific tool. Much of the data for this report has come from forty years of observing mice and corroborating both with the technicians lab in my department at Cambridge University and with many colleagues elsewhere. I have always admitted to a great deal of purely aesthetic pleasure in observing my mice.
Briefly, my approach was as follows. First, I listed the animal needs of which I was aware (Table 1). The list was fuller than I expected. My reading of current literature did not add to it. Then I listed human requirements (my requirements). The length of this list led me to expect conflicts.
A colleague who was experimenting with a shape rather shallower than the usual shoebox shape had remarked that his box was not suitable "because the mice shove all the sawdust out of it onto the floor." I thought it might not be the mouse which was behaving stupidly, but the person. Perhaps his mice were "telling" about a need he had not recognized. My first idea was that here might be a nest-building instinct they were using inappropriately, since there was plenty of bedding and the room was warm. Other people said that the deeper shoebox shape was best because it kept the bottle spout out of reach of bedding, which mice "inappropriately" pushed up to it which caused flooding of the cage.
I now set out to answer the question, "If you provide a nest area, will mice nest there, and will they still push excess sawdust up to the bottle or out of the cage?"
The resulting design (See Figures 1 and 2) is quite different from any cage in use then or now. None of its innovative features appears in the guideline manuals from the USA, the UK, or the EEC.
I found that the activity area seemed big enough for all activities, such as grooming, mating, fighting, and running up and down the floor and under the lid. Upright postures were not limited, except for stretching in very large mice. In a few strains there was some stereotyped gnawing of bars and twirling at the bottle end.
The spout was made of a 2cm length of capillary tubing, with not less than l.5mm bore instead of the usual wide-bore spout. In the <0.8 percent of cages surveyed on one occasion, in which bedding was built to the spout, the water did not siphon out due to the thickness of the glass.
If mice were not disturbed during the day, they slept under the shelter, even when not nesting. They mostly slept side by side, their bodies touching, with their noses lined up at the inner edge of the trough.
At one point, I took the nest temperature at different stages of nursing. At first it was much higher than room temperature (close to mouse body temperature), and by 15 days it had lowered to room temperature. The mice built a rounded snug nest before parturition, and gradually opened it until it was nearly unrecognizable, at 15 days and onward.
I now had the answer to my question (Figure 2). It was clear that mice needed not only nest material, but also a sheltered area to put it in. This area had to be of a shape in which they could manipulate the bedding to exclude draughts by closing the nest area up like a tunnel with one open end, and in which they could regulate nest temperature during nursing and sleeping. The term "draught" here simply means the unwanted exchange of air temperature between the animal room and the nest area. It also means, more importantly, unwanted exchange of air temperature between the activity area inside the cage and the nest area; the former, in a shallow cage, is the same as room temperature. For the nestlings, the nest had the same function as a woolly sweater for a person, and the solid tunnel outside the nest, the same function as a windbreaker over the sweater.
My conclusions were that mice need a sheltered nest area both to nest and sleep in. If given the sheltered area, they will not build elsewhere, unless nesting materials are excessive. Single mice get cold more quickly than a huddle of mice, so they need the "sweater and windbreaker" even more. It also seems that mice prefer the same temperature for activity as a human being does.
The design process for developing the Cambridge Cage followed the animal's needs throughout. To suit my own requirements I had had to make only minor alterations and additions on the way to make cleaning and stacking easier and to limit the cost of production. This was easily accomplished using simple shapes for the wire lid, shelter, and divider. Other details suiting human requirements are described in Table 2 (from Wallace, 1982).
Clearly mice responded strongly to temperatures inside the cages. In fact, uneven temperatures, using this cage, could be detected by observing unusual nest positions and by huddling of the mice, which does not happen in the usual shoe box type. When draughts are not detected, mice in the Cambridge cage move away from it in an attempt to build up the temperature around them.
In a design where animal needs and human beings' requirements are in harmony, new observations can be made, and new ideas tried out. This produces bonus features for animal and human.
In the Cambridge Cage, the two main areas are partially separated from each other. A cardboard inner from a toilet roll along the activity side allows token surrender when there is fighting, for example, between males.
Females, whether breeding or not, use a particular patch in the cage for urinating. Males without females do not concentrate the urine so much, as can be expected from our knowledge of their territorial behavior. But the observation prompts the question: why do females have this different behavior from that of males? If we knew, we could probably use the knowledge in cage design so as to reduce ammonia concentration in the animal room.
The importance to a mouse of having a sheltered nest cannot be overemphasized. Their smaller size must be conducive to heat loss at a greater rate than that for larger animals. The conventional mouse cage design does not allow for choice between warm and cool areas. The Cambridge Cage offers other choices for mice as well. Mice are extremely sensitive to draughts. As shown here, mice build nests in odd locations in the cage and in unusual ways in order to protect themselves from a draught hardly sensitive to my hands, but disclosed through taking temperature readings round the cage.
* nesting area for the comfort of mice, where they can control the temperature themselves.
* opportunity for a comfortable sleeping area with low light density, allowing for social huddling.
* easy access to water.
* a dry living space.
* less ammonia in the room air for the sake of both inmates and humans.
* a solid bottom cage, preferred by rodents over wire cages (Bradshaw and Poling, 1991).
* a less stressful environment.
* flexibility for change in experimental design (Wallace, 1977.) All in all, the Cambridge Cage seems to meet the needs of mice in humane and innovative ways that most conventional cages do not seem to be able to accomplish.
Margaret co-founded Lucy Cavendish College and retired from the Genetics Department in 1984, as an Assistant Director in Research. She has worked with mice all her professional life and has continued research in her own breeding unit set up with consultancy fees, with the help of her husband David.
Her family enjoyed riding their three ponies who all lived into their thirties and have since died. They have also rescued an abandoned Great Dane and have had the companionship of several other animals. Margaret now studies the behavior of mice and garden birds.
|
| Copies of this journal are no longer available for sale, but our other two journals, Society & Animals and the Journal of Applied Animal Welfare Science, are available and subscriptions are quite affordable. They can be ordered online via our secure order page. |