# Senior Rat Care: Aging Signs, Diet, and Comfort Senior rat care starts earlier than most owners expect. A pet rat usually enters the senior window somewhere between 18 and 24 months of age, and from that point the goal shifts from training and exploration to protecting muscle, warmth, hydration, mobility, and social contact. You do not need a prescription diet for every older rat. You do need weekly weighing, softer housing, quieter handling, and a much lower threshold for calling the veterinarian. This guide explains how to judge whether your rat is senior, what physical and behavioral changes to expect, how to feed an aging rat without destabilizing its digestion, and how to restructure the cage and daily routine around an older body. Behavior genuinely shifts with age in pet rats, and a survey of 677 fully completed owner questionnaires identified age-dependent changes in behavior as one of its findings [1]. What you are seeing is not your imagination. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## At a Glance: Senior Rat Care Priorities | Area | What to do | Why it matters | |--|--|--| | Age check | Treat 18 months as the start of senior care and 24 months as geriatric | The window from mature adult to end of life is short | | Weight | Weigh weekly on a small kitchen scale and record the number | Gradual loss is the earliest reliable signal of decline | | Body condition | Run your hands over the spine, ribs, and hips every week | Weight alone misses muscle wasting and fat gain | | Diet | Keep the base food stable and adjust texture and quantity | Abrupt diet changes cause diarrhea and food refusal | | Water | Offer at least two water sources and check them twice daily | Older rats dehydrate quickly when intake drops | | Flooring | Solid floor with deep, soft bedding | Recommended housing standard and easier on old joints [2] | | Rest sites | Low-entry shelters in several locations, plus nesting material | Rats prefer sheltered, complex spaces [3] | | Routine | Clean, handle, and feed during active hours | Husbandry during rest hours disrupts sleep and raises stress markers [4] | | Handling | Scoop with both hands and support the hindquarters | Low-stress handling reduces fear and stress [5] | | Veterinary contact | Ask for a baseline senior exam before obvious illness | Early findings are easier to manage than late ones | ## How Old Is a Senior Rat? Pet rats generally live about two to three years, with a minority reaching three and beyond. Working categories help you plan care: - Up to about 12 months: young adult - 12 to 18 months: mature adult - 18 to 24 months: senior - 24 months and older: geriatric These labels describe a stage of life, not a diagnosis. A two-year-old rat with good body condition and strong hind legs may be functionally younger than an 18-month-old that has been ill. Strain background, sex, lifelong diet, and previous disease all influence how a rat ages. Veterinary pathology reviews of laboratory rats note that species, strain, sex, and age all shape which spontaneous conditions appear, and that neoplasia sits within the expected spectrum of rat disease [6]. The short timeline is the reason senior rat care is so hands-on. A rat that drops from 500 grams to 450 grams has lost a tenth of its body mass in a species with very little reserve. In a larger animal the same percentage would trigger investigation immediately. In rats, that kind of loss can happen quietly over three weeks while the animal still greets you at the cage door. ### Why the senior window is short Rats reach sexual maturity within months and complete most of their physical development in the first year. Everything after that is a slow decline in reserve capacity. Muscle mass falls, skin elasticity drops, the coat thins, and the kidneys and heart have less margin under stress. Because the total lifespan is compressed, the interval between "a bit slower" and "needs help eating" can be a matter of weeks. That compression is why trend data beats snapshot data. Automated home cage monitoring used in laboratory settings captures spontaneous feeding, grooming, social contact, and sleep cycles across both light and dark phases, and it is valued for early detection of distress and disease progression through longitudinal, individualized records [7]. You can apply the same principle with a notebook and a $20 kitchen scale. ### Aging a rat with no known birth date Adopted rats, retired laboratory rats, and pet-store rats often arrive without a reliable birth date. Ask the veterinarian to help estimate age at the first visit. Useful clues include muscle tone over the spine, coat condition, clarity of the eyes, the amount of gray or thinning fur around the face, and how readily the rat climbs and rights itself. Retired laboratory rats are sometimes available through rehoming programs, and research on stakeholder views found support for rehoming across rehomers, animal technicians, and researchers [8]. ## Signs of Aging in Pet Rats Aging in pet rats shows up in the body first and the behavior second, but the behavioral clues are often what owners notice. Both deserve equal weight. ### Physical changes **Coat.** The fur loses gloss, thins over the flanks and hindquarters, and may look scruffy even after grooming. Some old rats develop bald patches from reduced self-grooming rather than from skin disease. **Muscle and topline.** The spine becomes more prominent and the hips look sharper. This is muscle loss, not necessarily starvation, and it changes how the rat tolerates handling and climbing. **Mobility.** Expect a stiffer gait, longer pauses before a jump, reluctance to climb cage bars, and eventually hind-limb weakness. Dragging of the hind feet is a reason to book a veterinary visit rather than accept it as normal. **Eyes and nose.** Cloudiness in the lens is common with age. Red-stained tears or nasal discharge are not normal aging. Chromodacryorrhoea, the red porphyrin staining around the eyes and nose, is used in laboratory welfare assessment as a stress marker, and rats whose husbandry was performed during their rest phase scored higher on it than rats handled during their active phase [4]. **Lumps and masses.** Older rats commonly develop subcutaneous masses. Mammary tumors, abscesses, and cysts can look similar to an owner, so a veterinarian should examine any new lump. A pathology review of laboratory rodents emphasizes that neoplasia is part of the expected disease spectrum in rats and that age influences which conditions appear [6]. **Teeth.** Rodent incisors grow continuously, and an older rat that stops gnawing can develop overgrowth or malocclusion. Drooling, food dropped from the mouth, and weight loss point toward a dental problem. **Breathing and stamina.** A rat that tires during short play sessions, breathes with visible flank effort, or makes audible respiratory noise needs prompt assessment. Respiratory disease in rats can progress quickly. **Bladder and water intake.** Increased drinking and urination, or urine scalding around the perineum, warrant a veterinary check. ### Behavioral and cognitive changes Older rats typically sleep more, explore less, and spend longer in one favorite spot. Some become more clingy with their owners. Others become less tolerant of cage mates or of being picked up. Reduced self-grooming is a meaningful sign. In the husbandry timing study, rats disturbed during their rest period showed reduced self-grooming alongside reduced sleep and reduced use of enrichment [4]. Cognitive change is harder to name but easy to spot. An old rat may stand staring at a cage wall, forget how it used to reach a shelf, or seem confused by a rearrangement of familiar objects. Keeping the cage layout stable, with food and water in the same place, reduces the mental load on a rat with declining memory. Owner surveys of pet rats have documented age-dependent changes in reported behavior, which supports treating these shifts as expected rather than as a sign that something has gone wrong [1]. ### Normal aging versus a veterinary problem | Finding | Often age-related | Needs a veterinary visit | |--|--|--| | Slower walking | Yes, if steady and pain-free | Sudden weakness, dragging, or knuckling of the hind feet | | More sleeping | Yes | Cannot be roused, or sleeps in an unusual hunched posture | | Coat thinning | Yes | Scratching, crusts, wounds, or parasites visible | | Weight change | Mild seasonal fluctuation | Loss of 5 to 10 percent of body weight, or rapid gain | | Cloudy eyes | Yes, gradual | Sudden blindness, red or cloudy discharge, squinting | | New lump | Common in old age | Any new mass, especially one growing over days | | Reduced appetite | Slower eating | Refusing food for more than a few hours, or dropping food | ## The Senior Rat Diet Most senior rats do not need a different diet. They need the same balanced diet delivered in a form and quantity that matches a changing body. The core requirements do not change with age. Laboratory animal care guidance describes access to clean water at all times and a wholesome, clean, palatable diet provided regularly so that protein, fat, carbohydrate, vitamins, salt, minerals, and fiber intake stays adequate [9]. ### Keep the base diet stable Do not switch foods because your rat turned two. Sudden diet changes in rats can trigger diarrhea and food refusal, both of which are dangerous in an animal with limited reserve. If a change is needed, transition gradually over one to two weeks by mixing increasing proportions of the new food into the old. ### Track body condition, not just weight A weekly weight on a small digital kitchen scale is the single most useful number you will collect. Pair it with your hands. Run your fingers along the spine and over the ribs, then feel the hips. You are checking for two opposite problems: - **Undercondition.** Spine and hips feel sharp, ribs are easy to count, and the rat looks tucked. This calls for a veterinary visit plus a review of food access, dental health, and competition from cage mates. - **Overcondition.** Ribs are hard to find and the rat looks round and sedentary. Obese old rats are poor surgical candidates and struggle more with heat and breathing. Cut treat volume rather than cutting the base diet. Never put an old rat on a severe calorie restriction plan without veterinary input. Older animals tolerate weight loss badly. ### Muscle and protein Muscle loss is one of the most visible features of aging in rats. Protein quality and total intake affect whether an old rat can hold onto lean mass. Rather than switching to a high-protein food on your own, ask your veterinarian whether your rat's current diet provides enough protein for its body condition, and whether any adjustment is appropriate given its kidney and liver status. That conversation is worth having at the senior baseline exam. ### Water and hydration Dehydration is one of the fastest ways an old rat deteriorates. Offer water in at least two places and in two formats if possible, a bottle and a shallow heavy bowl. Lower the bottle spout so a rat with stiff shoulders does not have to stretch. Check both sources twice daily, and check that the bottle ball actually moves. Wet foods help. A small amount of water-rich fresh vegetable, or kibble soaked in warm water, adds fluid without forcing drinking. If your rat is producing less urine or has dry gums, that is a veterinary matter, not something to solve with a bowl of water alone. ### Texture, chewing, and food interest An older rat with worn or painful teeth may still want to eat but cannot manage hard pieces. Soak kibble until soft. Offer cooked vegetables cut small. Avoid hard treats that require heavy gnawing if the rat is dropping food or drooling. Keep safe chew items available even for old rats. The incisors continue to grow, and a rat that stops gnawing for a few weeks can develop problems quickly. ### Feeding a rat that has stopped finishing meals 1. Weigh the food you put in and the food left over so you know whether intake has really fallen. 2. Separate the old rat at mealtimes if cage mates are stealing food. Supervise and then return it to the group. 3. Offer slightly warmed soft food to increase aroma. 4. Try smaller, more frequent offerings rather than one large bowl. 5. Hand-feed a few pieces to check appetite and to keep the human bond strong. 6. Book a veterinary visit if reduced intake lasts more than a day, or if it comes with weight loss, drooling, or changes in breathing. ### Treats, supplements, and human foods Treats should be small, low in sugar, and counted as part of the daily diet. Do not add supplements, vitamins, or human medications without veterinary direction. Rats are small enough that an inappropriate dose causes real harm, and the evidence base for most over-the-counter products in pet rats is thin. ## Comfort: Housing, Rest, and Daily Routine The cage that suited a lively one-year-old often fails a two-year-old. Rebuilding the environment around an aging body is the most effective comfort intervention you can make. ### Flooring, bedding, and warmth Solid-bottom cages with bedding are the recommended standard for rat housing, endorsed by the National Research Council and AAALAC International. A study comparing solid-bottom bedding cages with wire-bottom cages in male Sprague Dawley rats found no clinically relevant differences in a broad panel of clinical pathology values, so the recommendation rests on welfare and comfort grounds rather than on measurable blood changes [2]. For an old rat with thinning fur and less padding over the feet, solid flooring with a deep layer of soft, dust-free bedding is the obvious choice. Environment matters as much as equipment. Noise, temperature, humidity, ventilation, and the light-dark cycle all influence the health and welfare of rats in care [9]. Place the cage away from drafts, away from constant traffic, and out of direct sun. Old rats thermoregulate less well, so provide nesting material they can burrow into and check that the room does not swing between hot and cold. ### Rest sites and predictable layout Rats prefer complex environments that include shelters and multiple objects, offering different areas and resources for different behaviors [3]. For a senior, that preference translates into several low-entry shelters in different parts of the cage, so the rat never has to climb to find a soft place. Keep the layout stable. Moving the water bottle every cage cleaning forces an old rat to relearn a route it may no longer be able to navigate quickly. Clean around the furniture rather than rearranging it. ### Enrichment sized for an older body A large mapping review of 1,017 studies on rat housing refinements concluded that different refinements affect different rats in different ways, which argues against a single one-size-fits-all enrichment plan [3]. The senior version of enrichment is lower, softer, and shorter. Play has measurable value even in older animals. Access to a ball pit and playpen increased 50 kHz ultrasonic vocalizations in laboratory rats, a signal of a more positive affective state, and playpen access fully mitigated the negative affective state produced by an anxiety-inducing drug when compared with rats that stayed in their home cage [10]. You can adapt this at home with a shallow plastic tub of soft lightweight balls, or a low-sided playpen on a carpet, for five to ten minutes at a time. Skip anything that requires jumping or climbing. Good senior enrichment options include: - Shallow digging boxes with shredded paper or safe substrate - Soft cardboard tubes on the floor rather than mounted high - Scatter feeding a portion of the daily diet on a fleece mat - Scent trails using small amounts of familiar food - Gentle grooming with a soft brush if the rat accepts it ### Protect sleep and set your routine around it Rats are nocturnal-leaning animals that sleep heavily during the light phase. A study that moved routine husbandry procedures such as weighing and cage cleaning into the rats' rest period found clear costs. Rats handled during the light phase showed higher chromodacryorrhoea scores and less sleep, less self-grooming, and less enrichment-directed behavior than rats handled during the dark phase. The rats whose procedures took place during their active phase also showed higher relative thymus weight and more activity [4]. A companion report on the same work reached consistent conclusions about husbandry timing and welfare [11]. The practical translation is simple. Feed, clean, and handle your rats in the evening and early morning when they are naturally awake. Keep daytime disturbance to a minimum, especially for an old rat that already sleeps more. If you must clean during the day, work quietly and leave the nest area alone. ### Handling an older rat Nonaversive handling reduces fear and stress in laboratory rats and mice, and animal care professionals who use it report better welfare and better data quality [5]. Large organizations have moved away from tail handling toward refined methods across dozens of sites because of the benefits for animals, staff, and scientific integrity [12]. For a senior rat, refined handling means: - Scoop from below with both hands rather than lifting by the tail or the scruff - Support the hindquarters so the spine is not hanging - Let the rat walk onto your hand instead of being grabbed - Keep sessions short and put the rat back where it chose to be - Avoid picking up a sleeping rat without warning ### Companionship and social stability Rats are social animals, and social contact is a welfare need rather than a luxury. A study using social network analysis on a colony of rats found that individuals preferred to interact with rats of the same strain and laboratory of origin and with littermates, and that introducing new individuals caused social rearrangement, even though the original stability was eventually restored [13]. For senior care, that finding argues against disruptive introductions. If your old rat has a stable cage mate, protect that pair. If a cage mate dies, take time to decide whether a new companion is right for an elderly rat, and plan introductions carefully rather than dropping a young rat into the cage. Discuss the options with your veterinarian, who can weigh the social benefit against the stress and injury risk. ### Mobility modifications Small changes prevent a lot of decline: - Ramps at a shallow angle instead of vertical bars - Low-sided litter trays that can be stepped into - Food and water on every level the rat still uses - Non-slip shelf covering - A soft fleece hammock at floor level for a rat that can no longer climb - A shallow, heavy water bowl as a backup to the bottle ## A Daily and Weekly Comfort Checklist 1. Check both water sources and confirm the bottle is flowing. 2. Offer food and note how much is eaten within a few hours. 3. Look at the rat's eyes, nose, coat, and rear end. 4. Watch the rat walk across the cage floor for symmetry and stiffness. 5. Feel for new lumps along the flanks, chest, and belly. 6. Clean soiled bedding but leave the nest structure intact. 7. Weigh the rat once a week and write the number down. 8. Score body condition once a week with your hands. 9. Replace worn enrichment and check that hides are not tipped or blocked. 10. Book a veterinary review if any trend has moved the wrong way for two weeks. ## Monitoring: What to Record and Why Keep a simple log. Trends tell you more than any single observation, which is the same principle behind automated home cage monitoring in laboratory facilities, where spontaneous behaviors are tracked continuously across day and night phases to allow early detection of distress and disease progression [7]. Record these items weekly: - **Weight** in grams, same scale, same time of day - **Body condition** as a simple score, thin, ideal, or heavy - **Food intake** as a rough proportion of the normal portion eaten - **Water intake** as a rough estimate from bottle level - **Activity** as a count of minutes spent out of the nest during evening observation - **Grooming** as good, patchy, or poor - **Droppings** as normal, soft, or reduced - **Breathing** as quiet, audible, or labored - **New lumps** with location and approximate size Two weeks of a consistent downward trend in weight, grooming, or activity is enough to justify a veterinary appointment. You do not need to wait for an emergency. ## Common Mistakes in Senior Rat Care **Waiting for obvious symptoms.** Rats mask illness well. By the time an old rat looks sick, it has often been declining for days. **Skipping weights because the rat looks fine.** Visual assessment misses early muscle loss, especially in a fluffy rat. **Cleaning and handling during the day.** Husbandry performed during the rest phase measurably disrupts sleep, grooming, and enrichment behavior and raises a stress marker [4]. **Isolating an old rat for convenience.** Social separation removes a core welfare need. If a rat must be separated for medical reasons, discuss a plan for supervised contact with your veterinarian. **Changing the diet all at once.** Abrupt switches cause digestive upset. Transition slowly. **Rearranging the cage during cleaning.** Cognitive decline makes relearning harder. Keep landmarks stable. **Using tail handling because it is quick.** Refined handling reduces fear and stress, and the shift away from tail handling is well supported across large laboratory animal programs [5][12]. **Adding a young cage mate without a plan.** Introductions disrupt established social structure before stability returns [13]. **Ignoring a new lump.** Some masses are benign, some are not, and some are abscesses that need drainage. Only examination can separate them. **Using leftover medications or supplements from another pet.** Never do this with a rat. Doses are small and errors are serious. ## Troubleshooting Common Senior Rat Problems | Problem | Common contributors | What to do | |--|--|--| | Gradual weight loss | Dental pain, competition for food, kidney or heart disease, tumors | Book a veterinary exam, track intake, offer soft food in the meantime | | Sudden loss of appetite | Dental problem, respiratory disease, pain, GI upset | Veterinary visit the same day | | Hind-limb weakness | Age-related muscle loss, spinal disease, pain, obesity | Reduce climbing, add ramps, arrange a veterinary assessment | | Overgrown incisors | Reduced gnawing, malocclusion | Veterinary trimming, then provide safe chew items | | Scruffy coat and poor grooming | Pain, arthritis, dental disease, general decline | Check for lumps and mouth problems, then veterinary review | | Increased drinking and urination | Kidney disease, diabetes, urinary infection | Veterinary visit with a urine sample if possible | | Respiratory noise or effort | Respiratory infection, heart disease | Veterinary visit promptly, isolate from stressors | | Wounds or bite marks | Social instability, pain-related irritability | Separate temporarily, examine, consult a veterinarian | ## Welfare and Safety Points Senior rat care is welfare care. Three principles organize it. **Give the rat control.** Complex housing with shelters and multiple resources lets a rat choose where to rest, eat, and hide, and preference studies consistently show that rats favor this kind of environment [3]. Control over space reduces the stress of handling and cleaning. **Protect positive experience, not just absence of disease.** Enrichment such as a playpen or shallow ball pit produces measurable signs of positive emotional state in rats [10]. An old rat that still shows curiosity and engagement is doing well, and creating those moments is part of the job. **Reduce fear at every contact.** Low-stress handling reduces fear and stress and improves both welfare and the quality of any data collected from the animal [5]. That applies at home too. A rat that is not afraid of your hands is easier to examine, easier to medicate, and easier to help when it gets sick. Safety points worth repeating: no wire floors for old feet, no unguarded heights for a rat with weak hind legs, no cage mate introductions without a plan, no human medications without veterinary direction, and no unsupervised contact with other household pets. ## Limitations and When to Contact a Veterinarian Every rat is an individual. Age estimates, dietary needs, and tolerance for handling vary, and no general guide replaces an examination of your specific animal. If your rat has not seen a veterinarian in the past year, book a senior baseline visit now, while it is still stable. That visit gives you a reference point, a weight record, and a veterinarian who already knows your rat when something goes wrong. Contact a veterinarian promptly if you see any of the following: - Weight loss of 5 to 10 percent of body weight, or any rapid loss - Refusal of food for more than a few hours, or complete refusal of water - Labored, audible, or rapid breathing - A new lump, especially one that grows over days - Hind-limb dragging, knuckling, or sudden inability to walk - Drooling, food falling from the mouth, or visibly overgrown incisors - Persistent red discharge around the eyes or nose - A wound that does not close, or bite wounds from a cage mate - Hunched posture, tucked abdomen, or a rat that stops grooming entirely - Seizure activity, head tilt, circling, or collapse - Straining to urinate, blood in the urine, or urine scalding - Any sign of pain, including flinching when picked up or grinding of the teeth For urgent concerns outside normal hours, call an emergency veterinary service that treats exotic companion mammals. The Merck Veterinary Manual's exotic and laboratory animal section is a useful background resource for understanding the conditions your veterinarian may discuss, but it does not replace an examination. Quality of life deserves an explicit conversation. If your rat has more bad days than good, stops eating despite support, or has a condition that cannot be managed with reasonable comfort, ask your veterinarian to walk through the options with you. Planning that conversation early, while your rat is still stable, makes the decision easier when the time comes. ## Frequently Asked Questions ### How old is a senior rat? A pet rat is generally considered senior from about 18 months of age, and geriatric from around 24 months. Body condition and overall health matter as much as the calendar. ### How long do pet rats live? Most pet rats live roughly two to three years, with some individuals reaching three or a little beyond. Individual variation is wide, and lifelong health and genetics strongly influence the outcome. ### Do senior rats sleep more? Yes. Older rats typically sleep more and explore less. If your rat becomes difficult to rouse, sleeps in a hunched posture, or stops grooming, that is a reason to see a veterinarian rather than accept it as normal aging. ### What should I feed a senior rat? Feed the same balanced diet it has always eaten, adjusted for body condition, chewing ability, and appetite. Offer water in at least two places, soak hard food if the rat is dropping pieces, and ask your veterinarian before making any major diet change. ### Should I get a new cage mate for my older rat? Not automatically. Established pairs are valuable and should be protected. Introductions disturb social structure before stability returns, so plan carefully and discuss the risk with your veterinarian before adding a new rat. ### Are lumps common in older rats? Yes. Older rats often develop masses, and neoplasia is part of the expected disease spectrum in the species. Any new lump should be examined, because abscesses, cysts, and tumors can look identical from the outside. ### How often should a senior rat see a veterinarian? At least once at the start of the senior window for a baseline exam, then whenever a trend in weight, appetite, activity, or grooming changes. Many owners find twice-yearly checkups practical for older rats. ### When should I consider euthanasia for a senior rat? When your rat has more bad days than good, cannot eat or breathe comfortably despite treatment, or has a condition that cannot be managed with acceptable comfort. Discuss specific criteria with your veterinarian before a crisis. ## Sources 1. [Thinking outside the lab: can studies of pet rats inform pet and laboratory rat welfare?](https://doi.org/10.1016/j.applanim.2021.105507) 2. [Clinical pathology laboratory values of rats housed in wire-bottom cages compared with those of rats housed in solid-bottom cages.](https://pubmed.ncbi.nlm.nih.gov/16539332/) 3. [A mapping review of refinements to laboratory rat housing and husbandry](https://pubmed.ncbi.nlm.nih.gov/36759746/) 4. [Let sleeping rats lie: Does the timing of husbandry procedures affect laboratory rat behaviour, physiology and welfare?](https://doi.org/10.1016/J.APPLANIM.2007.06.019) 5. [Use of nonaversive handling and training procedures for laboratory mice and rats: Attitudes of American and Canadian laboratory animal professionals](https://pubmed.ncbi.nlm.nih.gov/36570505/) 6. [Research-Relevant Conditions and Pathology of Laboratory Mice, Rats, Gerbils, Guinea Pigs, Hamsters, Naked Mole Rats, and Rabbits.](https://pubmed.ncbi.nlm.nih.gov/34979559/) 7. [Challenges and expectations on the use of automated home cage monitoring for advancing laboratory animal care and welfare](https://pubmed.ncbi.nlm.nih.gov/41801108/) 8. [Rehoming laboratory rats: Exploring perceptions of rehomers, animal technicians and biomedical researchers](https://pubmed.ncbi.nlm.nih.gov/41519500/) 9. [Overview of laboratory animal lifestyle, care, and management: a case study of albino rats](https://doi.org/10.4314/jasem.v23i8.4) 10. [The use of ball pits and playpens in laboratory Lister Hooded male rats induces ultrasonic vocalisations indicating a more positive affective state and can reduce the welfare impacts of aversive procedures](https://pubmed.ncbi.nlm.nih.gov/35023405/) 11. [Let sleeping rats lie: does the timing of husbandry procedures compromise laboratory rat welfare?](https://www.semanticscholar.org/paper/cc6d3564618e9f1bec8c08b62898cbd1869d57f6) 12. [Change management strategies for improved animal welfare: Implementing refined handling for mice and rats in a global contract research organisation](https://doi.org/10.1017/awf.2026.10129) 13. [The “Second Life” of laboratory rats (Rattus norvegicus): Assessment of social behavior of a colony of rats based on social network analysis](https://pubmed.ncbi.nlm.nih.gov/36217647/)