8. Safety Issues
8,1. Aggression Among Males
In some territorial animalssuch as mice, rabbits and guinea pigsmales tend to be rather intolerant of each other. This can make it quite problematic to keep them together as isosexual groups in research laboratories. From the males' point of view, is it preferable to be alone? If the answer is yes, how should the cage be structured to provide species-adequate enrichment, so that the single-caged animal is not affected by distress resulting from chronic boredom? If it is preferable to keep these males in a social settingpairs or groupswhat are the options to minimize overt aggressive interactions?
Before getting hands-on experience in the animal facility, I read plenty about the issue of aggression in male mice and got the impression that it was next to impossible to house them in groups unless they were littermates. Working together with the animal caretakers in our facility, I have discovered that reality is more complex and also more positive than that. The practice in our animal house is that unfamiliar males, who are to be caged together, will be mixed early in the morning. The caretaker will then keep an eye on the animals for two days. If there is severe fighting, the most aggressivepresumably also most dominantmouse is taken out, and the poor fellow is then housed alone. As an ethologist, I would predict there would soon be a rearrangement in the hierarchical structure, with a new dominant, perhaps even more vicious male emerging, but the reality is, that this intervention does actually help decrease aggression within the group.
Emond et al. (2003) reported that animal care technicians at their center had started, out of concern for injured mice, separating dominant males who threatened, attacked or chased other males. The effect was so positive that two observation periods were set aside daily to identify dominant mice and separate these when indicated. By reducing or eliminating the number of aggressive acts between group members in the same cage, this "social conflict reduction program" led to a 57 percent reduction of mice being reported for injuries and death.
Male mice of several strains are particularly aggressive after their cage has been cleaned. They do not attack each other as buddies do in situations of conflicting motivations, but they go after each other in earnest. These little guys do not hesitate to inflict serious injuries on each other if they are not separated in time. Other rodents do not behave in this way when their cages are cleaned or changed.
After cage cleaning, individual mice try to establish new territories by depositing their scent marks on objects, such as enrichment items. Dominant males vigorously defend their territorial boundaries. The cramped space of the cage makes such an endeavor almost impossible, because subordinates have to cross these boundaries all the time. The constraints of confinement, therefore, can be a constant cause of territorial conflicts. The incidence of fighting can be reduced in some strainsnot in all!by placing novel toys, novel shelters, fresh cornhusk and paper tissues into the cages (Armstrong et al., 1998; Ambrose and Morton, 2000; Van Loo et al., 2002), allowing subordinate mice to break visual contact with the most dominant mouse in the cage.
There is convincing evidence that:
This makes it possible to minimize aggression among male mice by transferring used nesting materialnot soiled bedding material!at the time of cage cleaning (Van Loo et al., 2003; Van Loo et al., 2004b).
I think it is important to remember that, even though male mice tend to be pretty nasty among each other, they do show a strong preference for companionship even if this implies aggressive interactions. The proximity of another male is preferred to individual housing, irrespective of dominance, kinship or familiarity (Van Loo et al., 2001; Van Loo et al., 2004a). This indicates that "even" male mice are social animals who have an inherent need for social contact.
8,1,2. Guinea Pigs
We have kept some of our guinea pigs in groups of five or six for over a half year together. We have now started noticing an increase in aggression, especially bitten ears. Providing two 30 cm long PVC tubes seems to help with the fighting, but it has not solved the problem.
Based on my own experience with guinea pigs, I do not hesitate to say that these highly social animals are remarkably easy-going with each other in stable groups, especially in such small groups as you are dealing with. Space constraints may be a serious issue in your situation, but I think that a few behavioral observations will give you a clue what the real problem is and how to fix it. There should be plenty of hiding space for each guinea pig of your groups. As an alternative to the two PVC pipeswhich already probably take up most of the floor area of the cageyou may consider providing your animals with generous amounts of hay, serving both as a source of enrichment and a hiding substrate that all members of a group can make use of. If your animals are competing for the tube in order to be sheltered, they should no longer have a reason to compete when the shelter consists of hay.
Cozens (2006) had to euthanize several males due to bite wounds from fighting with cage mates. When the groups received hay on a regular basis, aggression diminished, and the animals stopped injuring each other seriously.
Agass and Ruffle (2005) addressed the problem associated with bullying by partitioning the cage and splitting the original group of four males into pairs. This modification considerably reduced the incidents of biting.
We had no success keeping male rabbits together after they have reached puberty. Our animals live in pens with outside run and places to hide, but this did not hinder them from viciously fighting with each other. Too little floor space may be the main problem; we cannot provide enough space for adequate social distancing. One buck, being chased by another dominant group member, can run away but is bound to quickly turn around, thereby making it impossible to actually escape from the attacker.
In the wild, bucks tend to stay away from each other and hardly ever engage in interactions other than chasing and fighting. Perhaps, attempts to socially house them are misguided. Castration makes them more tolerable (Kalagassy et al., 1999), but it does not eliminate serious aggression (Raje et al., 1997).
Most strains of male mice can and should be housed in small groups, if they are provisioned with proper nesting materialpart of which is transferred with them at the time of cage cleaningand if enrichment items are consistently exchanged with mouse-odor-free items when the cage is cleaned. Male guinea pigs get along with each other reasonably well when all of them have free access to places where they can get away from each other. To permanently live together in the same enclosure with each other is probably not a species-adequate housing arrangement for male rabbits. Their biologically normal intolerance of each other is unlikely to be overcome by castration.
8,2. How to Deal with Hamsters
How do you work with Syrian hamsters? I have never worked with these little guys before, but I hear they are nasty!
This is an ill-deserved reputation. Fair enough, hamsters are one of the most nocturnal of the common lab animals. You or I, just like a hamster, may be grumpy if someone wakes us up when we are sound asleep (Figure 61a). A hamster who is awake can easily be picked up with one hand or cupped in both hands (Figure 61b).
I have worked with hamsters for three years and have handled them extensively. I have not had one negative experience with catching and handling them, maybe because I love those little cuties! I always wait a couple minutes for them to wake up, before I handle them. This way they don't get startled. I then let them smell me, and finally just scoop them up. They allow me to do this without any protest. I have heard a lot of people claiming that hamsters are vicious, but I believe quite the contrarylet them handle mice to learn what's vicious!
Waking up a hamster before handling is prudent to give the animal no reason to bite in self-defense.
8,3. Handling of Mice
What is the safest and most animal-friendly way of handling mice?
I find the most important thing to remember is, being calm and quiet and move slowly, otherwise you may excite mice, and they will then attempt to bite you. When training people new to mouse handling, I always emphasize: "Don't be a cat!
Do not pounce! Be calm and move slowly!" Most people get the mental picture of a cat pouncing on a mouse and realize that this would naturally frighten a mouse quite a bit.
For the safe handling of a mouse. I would make the following recommendation: With a gentle but firm grip on the base of the tail with your thumb and index finger, turn your hand palm down, allowing the mouse to rest on your knuckles. Mice are much more cooperative if they have a firm base to stand on. I have never had a mouse bite me in this position. If you feel your mice are still frightened, you can use small PVC elbows. Just set one end in the cage, put some of their bedding material in the other end to encourage them to investigate and enter. They rarely tire of entering and exiting the elbow as long as there are familiar smells in it. When they are in the tube, you can carry them around.
Unlike rats, mice are better not handled by the body; it's a bit like trying to pick up a wet bar of soap in the bath.
When wishing to carry out injections, the mouse should be able to stand firmly while you pull her tail gently backwards, pick her up by the scruff, tuck her tail under your little finger, proceed to inject and return the mouse promptly to her cage. A little reward afterwards never hurts a mouse either!
The only thing I would add is that you need to have everything prepared before you open the cage, so that you can fully focus on the actual handling procedure and get the mouse back into the home environment without any delay. Unlike rats, most mice do not really acclimate to being handled. They want it to be done quickly, so they can get away from you and back where it's safe. I once saw someone scruffing the mouse and then fumbling to open a syringe packet. Fortunately, he was quick to understand why I was chastising him for that and is now always prepared before he even retrieves the cage.
If some basic, simple rules are strictly followed, the handling of mice is not associated with the risk of being bitten by a self-defensive animal.
8,4. Water Leakage
It is not uncommon that malfunctioning watering valves or leaky water bottles result in the accumulation of water in rodent cages, a circumstance that can have serious implications for the animals trapped in such flooded living quarters. In your own experience, what can be done to fix this problem?
I rarely see this problem in rats, but relatively often in mice. It seems to be worse if the animals are nervous or have litters. Since we have moved all our breeding colonies to a separate unit, where the animals are disturbed very little and kept in cages that are provisioned with shelters and nesting material, the incidence of wet cages has become negligible. When we have an occasional problem cage, we reduce the amount of sawdust and use more shredded paper instead. In my experience, water leakage is primarily triggered when the animals build a nest up against a drinker spout but is rarely due to a malfunctioning spout.
We have taken the following measures to keep the number of animals dying as a result of flooding very small:
We have moved away from an automatic watering systems since going to solid floor caging so as to prevent flooding, although we still get leaky bottles. Mice typically build up a mountain of bedding near the water bottlenot sure whyand that readily causes flooding. There is disagreement among caretakers about the amount of bedding to use. Some reason that a very thin layerhardly enough to cover the bottom of the cageand a 250 ml water bottle will prevent the mice from pushing the bedding up into the sipper tubes, and if the cage does flood, "only" 250 ml of water will be contained in the cage. However, there are still incidences of animals, especially pups, dying as a result of water leakage. Other colleagues argue that 1.5 cm of bedding or more will help keep the mice alive, since the bedding will absorb all the water that leaks from one bottle. But pups are likely to die from this also, since they would be cold from sitting on wet bedding.
We hang plastic tubes and other resting surfaces off the top of the cage, functioning as life rafts so to speak (Figure 31). This doesn't do much for the pups, but at least we save the adults. We are hoping this will alleviate much of the drowning risk, since we did not see any better options at this point. In fact, we are currently working on SOPs (standard operating procedures) that will make elevated furniture, such as tubes, a rule for all rodent cages.
I like the idea of tubes suspended on the side of the cages to keep adult mice dry and warm, but getting everyone else on the staff to agree turns out to be very difficult. Some people have a hard time endorsing anything that looks like environmental enrichment, and tubes fall into that category. I have seen videos of mouse and rat mothers carrying their pups to new nest sites. If a cage was to incorporate an elevated dry refuge structure, I wouldn't be surprised if the mothers evacuated the young from damp substrate to this dry and safe site.
Elevated resting surfaces can save animals from drowning and, therefore, should be regarded as basic furniture rather than as enrichment items for mice and rat cages.
8,5. Wire-Bottom Cages
Rodents prefer solid-bottom cages with bedding over standard wire-bottom cages without bedding (Blom et al., 1993; Schlingmann et al., 1994; Manser et al., 1995; National Research Council 1996; Van de Weerd et al., 1996). Apart from this preference, do the animals show behavioral, clinical or physiological signs that they are more distressed in wire-bottom cages than in solid-bottom cages?
We still use some wire-bottom cages for rats assigned to studies that require the exact measurement of food intake and the animal's waste. Any more than a few weeks, and the animals start getting sores on their feet in these cages. The sores are not infected, but I do think that they are painful and contribute to distress. Thankfully, the researchers finally agreed to limit the time that the rats have to spend in those cages to one or two weeks at the most, after which the animals are housed again in solid-bottom cages with appropriate bedding.
Sore hocks caused by wire-bottom cages jeopardize an animal's welfare. We have seen this problem very often in rabbits and in relatively heavy rats kept in wire-bottom cages. For this reason, we no longer use these cages. Fullerton and Gilliatt (1967), Grover-Johnson and Spencer (1981), Ortman et al. (1981) and Peace and Singer (2001) found in guinea pigs and rats, respectively, that long-term wire-mesh caging is often associated with pressure neuropathies. Kraus et al. (1994) underlines the high incidence of ulcerative pododermatitis (sore hocks) in rabbits kept on wire-bottomed cages. Sauer et al. (2006), however, claims in a study published in the Journal of the American Association for Laboratory Animal Science that:
A board-certified veterinary clinical pathologist determined that there were no clinically relevant differences between rats housed in wire-bottom cages and rats housed in solid-bottom cages.
I am afraid that this "professional" statement can very easily be twisted and used to keep the standard wire-bottom cage in place, at least in the United States where rats are explicitly excluded in federal animal welfare regulations. It is noticeable that even the Office of Laboratory Animal Welfare (2002) discourages the use of wire-bottom for rodents, especially on long-term studies or in larger and older animals, as it may cause foot injury.
Wire-bottoms jeopardize the welfare of caged animals. A 1999 report showed that more than 80 percent of the rodents in surveyed toxicology facilities were housed in wire-bottom cages, presumably because considerable costs would be associated with a change from wire- to solid-bottom caging (Stark 2001).
8,6. Wood in Cages
Have you ever encountered specific problems when you provide your animals with branches or gnawing sticks?
Our macaques have access to branches and gnawing sticks. All the wood first goes through a "quarantine" period and remains in a cool dry place indoors for approximately 2 to 3 weeks. We have been giving our animals natural wood for maybe over a year now with no clinical incidents, but we witnessed a behavioral problem associated with the branches: A juvenile rhesus male decided he was a chimp and chased his mates around the pen brandishing the branch as a weapon. After that we secured all branches on swinging cables!
We encountered a similar complication when one of our rhesus male started using small branches as a beating stick for the rest of the group! We switched to PVC pipes and fence boards because of this brat. However, we still give the animals cherry wood gnawing sticks, which we throw away after a few days and replace with new sticks. I am not aware of any clinical issues related to these gnawing sticks.
Over a period of several years, I provided more than 700 rhesus and stump-tailed macaques with gnawing sticks and branches, cut from dead red oak trees, and encountered no recognizable health hazards (Reinhardt, 1997). The wooden material is cleaned with warm water daily and disinfected once every two weeks during the routine cage sanitation procedures. After one to six months, the branches and sticks are replaced due to wear.
Our rabbits, guinea pigs and goats get branches from non-sprayed apple treeslightly autoclaved for 3 minutes at 120º F. They love them! We set the size limit at pencil thickness, which makes the sticks relatively soft and pliable. Perhaps this is why we encounter no splinter or digestive issues.
The provision of branches and gnawing sticks does not create fomite or clinical problems if common sense sanitary procedures are applied.
8,7. Swimming Pool for Macaques
The center where I work has several cyno breeding colonies housed in large outdoor enclosures. I am interested in using stock tanks to provide swimming opportunities. I have heard that cynos are adept swimmers, but is there a risk of drowning, particularly for infants? Is there danger of one monkey inadvertently drowning another monkey?
The stock tanks we use have a lip half way up the inside of the tank, so if an infant fell into the water it could easily get back out. We used these tanks all of last summer and half of the summer before without ill effects (Rawlins, 2005). The monkeys who do go under water hold their breath for a surprisingly long time. I have watched juvenile cynos swim with no difficulty. I have never come across one who can't swim. It seems to be an inherent skill they don't have to learn.
We give our pair-housed cynos "bathtubs," filled with 30 to 40 cm deep warm water, a few times a week, and have never encountered any problems other than a lot of splashing. Some monkeys take luxurious baths, others climb on a perch and jump into the water, others sit on the side walls and drag their hands in the water, and others wash their fruit in the water. Usually the monkeys make a real mess within the first half hour, and yes they do urinate/defecate in the water. We empty the tubs after about two hours, if the monkeys haven't done it already themselveswhich is often the case.
There are a few published articles on the use of swimming pools for rhesus, long-tailed and Japanese macaques. None of these papers mention any safety or hygienic problems (Gilbert and Wrenshall, 1989; Anderson et al., 1992; Anderson et al., 1994; Goodwin, 1999; Rock et al., 2004).
Empirical evidence indicates that captive long-tailed macaques enjoy contact with water, and that access to shallow water does not cause any risk of drowning.
8,8. Pairing Sedated Animals
Allowing two unfamiliar sedated partners to regain consciousness in the same cage is a way to form new pairs for previously single-caged animals. Based on your own experience, would you recommend this pair-formation technique?
It certainly works with pigs and rabbits. We establish new pairs in this manner on a routine basis with great success.
It also works with baboons: Bourgeois and Brent (2005) placed pairs of sedated, four years old male baboons in the same cage and allowed them to wake up together. All seven pairs tested were compatible. Rough-and-tumble wrestling was observed and dominance positions were quickly established, with all dominance disputes followed by bouts of grooming. During two-week follow-up periods no overt aggression was observed.
We don't use sedatives to establish new pairs of macaques, but it sometimes happens that one partner of a pair has been removed and sedated for clinical or experimental reasons. In this situation, we always make certain that the sedated animal first recovers fully before re-uniting the two companions. If the sedative was injected in the afternoon and the subject is still groggy at the end of the work day, we'll leave the two monkeys separated overnight. We don't want to take the risk that the awake partner possibly "takes advantage" and attacks the companion, who might still not be in full control of his or her body movements.
Using sedation as a tool to introduce new cage mates with each other seems to work well with pigs and rabbits and perhaps also with monkeys under the condition that the animals are carefully supervised.
8,9. Pair-Housed Monkeys with Head Cap Implants
Is it safe to house monkeys with head caps as pairs? Do you form the pairs prior to or after head cap implant surgery?
Our university tries to pair all rhesus macaques regardless of cranial implants. Normally the pairs are established before they have undergone surgery for head caps, but we have successfully paired primates after surgery as well. Over a period of ten years, we have had no incidents of damage to the implants. We have more problems, with coils of head caps breaking, in single-housed than in pair-housed rhesus. The head caps of pair-housed animals are cleaneras they groom each otherthan those of individually caged animals (Figure 62).
||Figure 62 Paired rhesus macaques keep the margins of each other's head cap implants remarkably clean. Photo by Viktor Reinhardt.|
We have 10 pair-housed male rhesus and long-tailed macaques with head caps. The animals were 3-to-6 years-old at the time of pair formation. They are presently approximately 10-years-old. Some of them had head caps before they were paired, others got them afterwards. It didn't seem to matter. In my experience, pair-housing does not create a risk factor when the animals have head cap implants. In all the time I've been working with these monkeys, they've never damaged one another's head caps.
I have worked with more than 100 pair-housed rhesus macaques with cranial implants and encountered no clinical problems related to the fact that these animals shared a cage with another companion. I always established the pairs prior to surgery, but this was perhaps not necessary. I just didn't want to take any avoidable risk.
Practical evidence indicates that macaques canand shouldbe pair-housed, without undue risk of jeopardizing ongoing research, though one or both partners of the pair has a cranial implant.
8,10. Re-Pairing Macaques after Separation
We have several same-sex pairs of adult cynos and rhesus who will be assigned to a project requiring repeated 48-hour separations, during which one partner will be tested in another room. The question is: Will it be safe to re-unite the animals after the testing, and will the pairs remain compatible when they are repeatedly separated and re-united?
Your animals will be separated only for relatively short periods, so I really don't think you have anything to worry about re-pairing them. I had no trouble re-pairing several adult male cyno pairs who were separated for weeks. The only animals I had consistent difficulties re-pairing were adult rhesus macaques of both sexes. When you simply put them together, the two compatible companions may not recognize each other quickly enough at the moment of re-pairing, but treat each other as strangers and start fighting. The consequences of this misunderstanding usually is very traumatic. I finally discovered that you can avoid this risk by inserting a transparent or grated mesh cage divider, and then introduce the one who had been away into the empty half of the home cage. Let the two find out who they are, and then simply remove the divider. I have used this trick many times without failure.
Re-union of temporarily separated cage companions bears some risk if both partners do not recognize each other instantaneously and, therefore, treat each other as strangers. This risk can be minimized by giving the two partners the chance to recognize each other first through a transparent barrier, and only then re-introducing them.
8,11. When a Monkey is Lying Down
I have heard that monkeys are will lie down when something is wrong with them. I do notice that some of our rhesus macaques spend a lot of time lying after they have experienced a distressing situation, for example after surgery and after enforced medication. I am wondering, should I really be concerned when a monkey is lying down?
I have observed some of our rhesus, bonnet and long-tailed macaques lying down. This happens rarely, but I can say that none of these monkeys was sick. I am like you, however, whenever I see a monkey in a recumbent position, my heart always skips a beat. It's true, the sight of a lying monkey is a bit alarming. I don't really know why.
Some of our rhesus girls occasionally lie down during the day, but there is nothing wrong with them. They either lie on their stomach or their sides. I never really thought anything ill of it. We have one little girl, who likes to lie down in her cage most of the time. She doesn't rest in her hammock or on the perch but always on the floor. She is healthy and by no means distressed. She lies down just like you or I would do when taking a nap. If I happen to approach her cage, she'll get up immediately.
We have a rhesus who does the same thing. The first time I saw her lying on the bare cage floor, I was scared to death. I thought she was in serious trouble. It is always comforting that she gets up the moment I walk into the room.
If your monkey had access to a tree, you would probably see her lying on her belly or on her side on a branch. It looks funny, but it's normal. I have seen this quite a number of times in group-housed rhesus who would often climb up on the highest perch and take a nap (Figure 63).
When you have a monkey who remains in a lying position even when you approach the cage and get ready to open the door, this is an alarm signal that you better do not overlook. Otherwise, lying down is a sign of comfort rather than discomfort.
8,12. Retro-Orbital Blood Collection
How safe is the retro-orbital bleeding technique?
How safe is the retro-orbital bleeding technique?
I used to take blood samples from the retro-orbital sinus in mice and got quite good at it. Fortunately no multiple bleeds were required on the same day. Now, I am in a different department and need to take eight samples in 24 hours. It really bothers me to use this site at the eye so often. I believe the saphenous vein is the way to go, although it may take longer in the beginning to become really proficient. A person working in ophthalmology told me that he did not like the retro-orbital bleeding method at all because it can easily alter the intraorbital pressure, causing severe discomfort to the subject. So yes, there are legitimate ethical concerns.
To my knowledge retro-orbital bleeding is mainly used in mice, rats, hamsters and guinea pigs. This technique does have important advantages. The technique is:
Additionally, the eyes can alternated with a one-week interval, and the rodent subject recovers quickly as reflected in corticosterone, catecholamine and behavioral responses (Van Herck et al., 1994). These practical advantages, however, are outweighed by serious ethical disadvantages:
In Denmark it is forbidden to take blood from the retro-orbital sinus without proper anaesthesia, as the procedure is deemed to be really painful. One has to remember that the conjunctiva has to be penetrated during this procedure. Taking blood from the lateral saphenous vein or by a small cut in the ventral tail vessels can be done without anaesthesia and goes fast in mice and rats.
The first time I saw a retro-orbital bleeding was about five years ago. We needed a sample to test for MHV (mouse hepatitis virus). I called our vet and asked if he could teach us newbies how to get a blood sample from a mouse. He discussed various methods and then told us that he always does retro-orbital bleeding on mice. He then proceeded to do the deed, without any anaesthesia. It took maybe 4 to 5 seconds! I do not mind saying that I went completely weak in the knees and if I had not been standing next to a wall, I might even have gone down! We checked the mouse several times that day and he seemed fine, better than me in fact.
It's true, retro-orbital blood collection appears to be somewhat gruesome, but if you have a good teacher and enough practicethis above all is the most important part of the puzzleit isn't a bad method. It is quick, provides a good amount of clean sample and, in my opinion, requires little to no anesthetic, depending on how much your mice resist. Now, I will admit that errors can occur during these bleeds, and I myself have made a few that have ended up in a way that definitely did not sit well with me at all.
Clinical and ethical concerns outweigh the practical advantages of the retro-orbital bleeding technique in rodents. Preference has to be given to alternative techniques, especially to the saphenous blood collection procedure, that are less risky.
8,13. Barking of Dogs
Barking dogs can be a serious noise problem in research labs. Do youand the dogssimply put up with it or do you try to modify the environment so that the dogs have less reasons to bark?
We house 40 to 60 dogs at a time in two rooms adjacent to each other. Whenever we enter a room, the dogs greet us with barkingof coursebut they usually chill out and stop barking after a short while, except at feeding time! We require that everybody wears ear protection when working in dog rooms. I wonder if having music in the rooms would help. Kilcullen-Steiner and Mitchell (2001) found that a "white noise" stereo system along with "new age music" can effectively decrease the amount and intensity of the barking.
The dogs at our facility bark much less if they are taken out and walked. We have a volunteer walking program. We also noticed a significant decrease in barking after we placed platforms in all our indoor group-runs. The platforms serve the dogs as look-out sites from which they can monitor all activities in the rooms, especially people entering the room.
It is probably impossible to make dogs stop barking altogether, but there is no need to accept barking that creates a noise problem. Dog-adequate enrichment, especially platforms giving the animals visual control of their immediate environment and regular walks with an accompanying person, can effectively decrease the dogs' need to bark.
9. Extraneous Variables
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