Reuniting Cats After an Evacuation Separation: When They Come Home and Act Like Strangers

Separate the cats with a barrier, not your hands. Get both examined by a veterinarian for pain or illness. Then reintroduce them gradually, starting with scent, at a pace your veterinarian agrees with. Current veterinary guidance says never to let the cats fight it out themselves.

This page is about the hallway after the evacuation is over. A common version: one cat spent the evacuation at a relative’s home and one at a boarding kennel, and soon after the second carrier opens they are screaming at each other, though nothing visible is wrong with either cat. Getting several cats out under an evacuation order is a separate job, covered in our room-by-room plan for evacuating multiple cats. This page starts after that one ends.

Every published protocol puts a veterinary examination before any behavior work. No veterinary source cited here covers the disaster version of this problem: staggered returns from different buildings to a house that no longer smells the same. Where this page applies general guidance to that situation, it says so.

The first hours: separate the cats safely

Use a barrier, not your hands. Cornell’s Feline Health Center says: “It is crucial that you never put your hand or any other body part between cats that are fighting, as you can be seriously injured.” It recommends barriers such as baby gates or panels of cardboard, light wood or plastic. The 2024 AAFP intercat tension guidelines suggest putting the cats in separate rooms with doors closed, and using large towels or blankets, or a cardboard or laminate sheet, as a visual barrier to prevent human injury. They add that anyone who feels they must step into a fight needs to understand the risk of redirected frustration and use appropriate protection.

Do not approach an aroused cat to comfort it. The AAFP guidelines say never to interact with cats who are “hissing, growling, tail flicking, urine marking or showing other signs of arousal”, because a cat that cannot reach the cat it is upset with may redirect its frustration onto the closest target. The ASPCA gives the same practical instruction: leave the cat alone and give it space, because if you come close it may redirect onto you.

Then leave them apart while they settle. The AAFP lists leaving the cats separated, with no physical interaction, after an incident until they have calmed down and returned to their normal routines. The AAFP adds: “This may take anywhere from a few hours to a couple of days.” That is a cool-down window, not a prediction of how long the reunion will take.

If anyone was bitten, treat it as a wound. A bitten person needs medical care and a bitten cat needs veterinary care. The AAFP’s second first aid item asks you to assess injury to both people and cats.

Call the veterinarian before any scent swapping

The 2024 AAFP guidelines include a numbered behavioral first aid kit. Item 1 reads: “Veterinary examination to assess for medical condition and pain; veterinarian-client-patient relationship must be established.” Item 2 is to assess injury to people and cats and separate the animals as needed. Scent work is not in the kit; it belongs to the reintroduction that follows. Item 10 asks the veterinary team to follow up with the caregiver in two weeks, which is worth asking them to book before you leave.

Cornell opens its aggression brochure the same way: “The first step in managing an aggressive cat is to ensure that there is no medical reason for aggressive behavior.” It names hyperthyroidism, osteoarthritis, dental disease and central nervous system problems as conditions that may cause aggression. The ASPCA says any sudden change in behavior could signal an underlying medical condition, and to see your veterinarian right away if a cat shows unusual symptoms or stops eating.

For an evacuation household this is not a formality. The cats may have been exposed to other animals, eaten and drunk differently, missed medication or been hurt in transport. When you collect a cat from a facility, ask what it was treated for, what it ate, and whether it was sedated. Our emergency boarding checklist covers the paperwork side of a stay.

One AAFP instruction applies to any cat that came home from a clinic: “in the case of cats returning from anesthesia, wait for full recovery before reintroducing the cats and begin with scent exchange to refamiliarize the cats.” Your veterinarian defines full recovery, not the calendar.

About the phrase “non-recognition aggression”

That is what many owners search for. The 2024 AAFP guidelines do not use it. They advise avoiding subjective terms: “Subjective terms such as ‘aggressor’, ‘bully’, ‘victim’ and ‘aggression’ should be avoided.” Their stated reason is to use terms that help explain the causes and emotions behind the behavior, and their preferred word is “tension.” Merck, the ASPCA and Cornell do not use the phrase either. This page calls the two animals the cat that came home and the cat that stayed, and calls the process by the AAFP’s term, reintroduction: reuniting resident cats who have been separated, for example after a veterinary visit or because of tension.

The term does appear in an article in the IAABC Foundation Journal (Issue 26, February 2023, by Allison Hunter-Frederick), which defines it as one cat returning after time outside the home and being treated as a stranger or threat by a cat that stayed. The author says her writing rests on expert opinion, her professional and personal experience, and an informal survey of cat owners, and she calls the survey’s sample of 30 too small for reliable conclusions. She also reports that two named experts, Dr. Sarah Ellis and Dr. Stephanie Borns-Weil, see some of these cases as better explained by redirected aggression. The label is contested inside the profession, so describe what your cats are doing to your veterinarian instead of bringing a diagnosis you found online.

What the sources say is happening

None of the veterinary sources describe one cat forgetting the other. They describe a change in how the returning cat smells, looks and acts, arriving in a household that identifies its members partly by smell.

• AAFP. Novel sensory stimuli, including a cat returning home after a veterinary visit, can be stressful for resident cats and may cause fear, anxiety or frustration. Tension can arise between long-term housemates, even formerly close ones, when a trigger disrupts the relationship. The trigger may be internal: pain or disease that raises irritability, or a change in odor or behavior after a trip to the veterinarian. The guidelines also say: “Because cat social groups share a communal scent, odor exchange is a useful preliminary step.”
• ASPCA. Cats may get along until something scary or unpleasant, such as fireworks or the odor of the veterinary clinic, becomes associated with the other cat. It also notes that relationships can change as cats mature, and that trouble at age one to three years may reflect social maturation. That matters if your cats are young and the evacuation is a coincidence.
• Cornell. It files the situation under territorial aggression: cats may attack resident cats that were previously accepted but were away from the home, such as for a hospital stay. Its page was last updated in December 2016, before the 2024 guidelines. Where they differ, the newer guidelines are current.
• Fear Free (Amy Shojai). Cats likely identify each other by a shared communal scent that intermingles when they sleep together and groom each other. A long absence, or even brief handling by strangers, changes that scent identification.
• IAABC article. It lists theories without ranking them: the returning cat’s scent masked by strangers, other animals, veterinary smells, disinfectant, anesthetic gas or grooming products; the resident cat linking the returning cat with a bad experience; the returning cat smelling of stress or fear; or looking and acting differently because of sedation, unusual body language or pain.

Put together, the sources suggest that a returning cat may arrive smelling of a building, possibly moving oddly and possibly in pain, and any one of those can make the household treat it as unfamiliar.

Why an evacuation return is different

The published protocols cited here are written around one cat leaving and coming back: a veterinary visit, a hospital stay, a groomer, a spell outdoors. None addresses an evacuation, so the four points below are reasoning from those triggers, not published findings.

• Staggered returns multiply the event. Two or three cats may come home on different days from different buildings. The AAFP protocol is written for one returning cat. Running it repeatedly against a household that has not resettled is not described anywhere, and the AAFP’s own warning applies: “A common error in reintroducing cats is rushing through the steps.”
• Several facilities mean several foreign scents. Our page on whether two cats can share a carrier notes that the 2011 AAFP and ISFM feline handling guidelines advise bringing cats to the clinic together, so both carry the clinic scent. A staggered evacuation return is the inverse of that situation.
• The house may no longer smell like the household’s territory. Floodwater, smoke, ash, professional cleaning and replaced carpet or furniture all change it. The AAFP’s redecoration and moving-house entries advise keeping or bringing the cat’s own furniture, plus pheromone therapy and a safe place. Applying that to a post-disaster house goes beyond what the AAFP wrote, and it may not be possible where items are destroyed or contaminated. Whether a smoke- or flood-damaged item is safe to give back to an animal is a hazard question covered in our returning home with pets checklist, and safety outranks scent.
• Both cats may be affected. After a staggered return, both may be arriving into a place that smells wrong, both may be unwell, and both may have spent days in a kennel run. That is another reason the veterinary examination is not optional.

How long it takes: three separate published timeframes

Three documents answer three different questions:

• Cool-down after an incident (AAFP): a few hours to a couple of days.
• When behavior work can start (Merck): counterconditioning and desensitization with favored rewards, such as play with toys or treats, can begin only after a cat is calm, which Merck says can take days to months. That range describes how long calm may take to arrive, not a treatment length.
• How long reintroduction runs (AAFP, Cornell): the AAFP says progress varies enormously with the cats’ adaptability and the caregiver’s commitment to training: “In less severe cases, reintroduction may take a few weeks; other cases may require several months or even a year or so.” Cornell says its process “can take weeks to months, depending upon the cats involved.”

None of these is a forecast for your cats, and each is a range wide enough to include a case that goes badly. The AAFP’s governing instruction is to repeat a step rather than move forward in the hope that things will work out.

Four published protocols, kept apart

These come from four documents and are not the same sequence. Follow the one your veterinarian points you to, and use the others to understand why it is built the way it is.

AAFP 2024: six steps and a detailed box

The AAFP’s algorithm lists six steps for cats being kept separated during treatment. It says progress should be gradual and dictated by the cats’ ability to adapt, and that if signs of tension do not fall or increase, you stay at that stage longer or go back a step.

1. Let the cats become comfortable in separate areas, with individual times to explore the rest of the home.
2. Add smell and sound contact at a distance, for example scent exchange through bedding swaps.
3. Allow supervised visual contact from a distance, for example each cat in a carrier it is very comfortable in, or both free but separated by a glass door.
4. Allow supervised physical proximity, for example each cat in a harness and leash, or both free only if very relaxed.
5. Bring the cats together under supervision for short periods outside of reintroduction sessions, such as a couple of hours after a very positive session.
6. Keep the cats together most of the time at first, then all the time.

The guidelines’ Box 6 adds detail:

• Scent. If the cats have been physically separated, exchange scent daily for a week or so before any visual reintroduction, by swapping a familiar piece of soft material that carries each cat’s scent. Time-sharing communal areas and synthetic feline pheromones may also help.
• Partition first. Reintroduction should be gradual and begin with the cats on either side of a dividing door or other partition. The box describes play on either side of the door with a string and small toy, limiting visual and physical access with door straps, and using treats to build a positive association.
• Session length and stop condition. Sessions are kept to 5 to 20 minutes maximum, ideally ending on a positive note with treats or play with a favorite toy away from the partition. “If cats show any sign of distress, the session should be ended immediately.”
• After the partition. When the cats can relax with partial visual access, use a fully transparent partition and repeat. If all goes well, allow supervised, time-limited physical proximity in a communal area. Cats may need to be harness-trained and introduced on a leash, especially after a serious injury or if one is highly fearful. Increase the time over weeks. Cats should not be forced into the area, and a cat that keeps hiding or retreating indicates persistent tension, so the earlier steps are repeated.
• Your situation. If tension has previously been observed in the household, including on arrival home from a veterinary visit, the returning cat should not go straight back with the others and should be reintroduced with these methods. That is conditional on tension already having been observed. If your household saw it after this evacuation, the condition is met.

Merck Veterinary Manual: confinement, then odors and a partition

Merck calls confinement away from the provoking stimulus an essential first step. Usually the cat is housed in its own room with litter box, toys, bedding and food. Some cats must be separated at all times until calm enough to be reintroduced, but if conflicts arise only at particular times or in particular situations, Merck says it might be necessary to separate them only at those times. Reintroduction by desensitization and counterconditioning might begin with odors, by grooming each cat with a brush or towel used on the other, and feeding each cat separately on opposite sides of a partition before moving to a common area at a distance where both stay calm. Merck’s odor step (a brush or towel) differs from the AAFP’s (a familiar soft item exchanged daily). Merck also says positive punishment increases fear, anxiety and aggression in cats.

Cornell: the room swap

Cornell says the most important thing is not to rush an introduction or reintroduction. New or returning cats should be confined to their own room with separate litter box, water and food. After a few days, the returning cat and the other cat swap rooms for about 30 minutes, then each goes back, repeated daily for several days. Next, the cats sit at opposite ends of the same room in carriers or on harness and leash, fed so they associate food with the other cat’s presence; if they will not eat, move them farther apart. The last stage releases them in the same room at a distance, with food, and if any signs of aggression occur, Cornell says to resume restraint and feeding in the same room until they calm down.

ASPCA: two tracks

The ASPCA splits advice by severity. The first track covers mild aggression, or cats who used to get along, which is likely the closer fit for an evacuation household.

• Separate the cats in different rooms for several days or weeks, with separate beds, bowls and litter boxes, so they can hear and smell each other without interacting.
• Put food bowls on opposite sides of a closed door.
• Have the cats switch rooms each day to share scents. You may need an assistant to do this safely.
• After several days, if both cats seem relaxed, crack the door open one inch, then a bit more if they stay calm. If either shows signs of aggression, such as growling, spitting, hissing or swatting, separate them again and follow its gradual reintroduction instructions.

The severe track adds daily supervised sessions that gradually bring the cats closer, harnesses and leashes or crates for control, and distraction with food or play. It says the cats should be left alone together unsupervised only once they can peacefully eat and play within a couple of feet of each other.

What to avoid

Do not let them settle it themselves. The AAFP guidelines say: “Veterinary professionals should educate caregivers not to let cats ‘work it out themselves’ or try to force cats to get along.” They point caregivers to the cats’ environment and whether resource distribution is creating tension. Cats have few reconciliation behaviors, so a stand-off can develop with neither cat having the skills to resolve it. The ASPCA also says never to let cats fight it out.

Do not punish or reprimand. Item 7 of the AAFP first aid kit is to stop reprimanding the cat or attempting discipline-based training such as yelling. The guidelines define that training as using fear-provoking stimuli (spraying water, yelling) or physical punishment.

Two sources disagree here. Right after telling readers never to let cats fight it out, the ASPCA suggests interrupting aggression with a loud clap or a spray from a water gun. The AAFP names spraying water as discipline-based training to discontinue. The two cannot both be followed. The 2024 AAFP guidelines are the current veterinary guideline on this problem, written by a task force of board-certified veterinary and applied behaviorists and clinical experts in feline medicine and behavior. Ask your veterinarian which they want you doing in your house.

Do not feed them side by side to force a bond. AAFP item 8 is to separate cats at feeding time with visual barriers, and its sessions never encourage eating in close proximity. The protocols above use food only at a distance, moved in slowly.

Do not add a medication, supplement or calming product on your own. The AAFP says psychotherapeutic medication can be a useful adjunct, sometimes essential, but only alongside environmental and behavior modification. That decision belongs to the veterinarian who examined your cats.

Pheromones: what the guidelines say, and the caveat

Synthetic feline pheromones are item 5 of the AAFP first aid kit and appear in its trigger-prevention entries, including the veterinary visit entry. The guidelines attach caveats. On one complex, they say preliminary studies suggest it helps with intercat tension, scratching, urine marking and fear, but that controlled clinical trials are needed to confirm efficacy. They add that responses depend on the individual’s emotional state and can be very subtle, and that in a cat who is already relaxed, or facing clear signals of danger, pheromones may have little effect. They note that traditional evidence-based evaluation can therefore be misleading. The term “pheromone” is not protected, so scent products may be labeled as pheromone-related, and the guidelines advise checking whether a product actually contains feline pheromone analogs. Merck says only that synthetic feline intermammary pheromones might effectively decrease intercat conflict.

A diffuser is a low-risk item within a plan alongside separation, examination and a paced reintroduction. No source says it is the plan.

Prevention, for the next time you leave

• Try to keep the cats together. Fear Free’s first tip: “One easy way to reduce the chance of cat bashing is to take all your cats to the clinic at the same time.” The IAABC article lists taking cats together on excursions among its prevention ideas. Whether that is possible in an evacuation depends on the boarding facility, vaccine lead time and hotel caps; see boarding versus evacuating together and choosing and timing emergency boarding.
• If they cannot travel together, plan the return. Fear Free suggests giving the returning cat some time alone at home, such as half a day in a guest bedroom, to let the hospital smell wear off. It also describes rubbing a clean, dry hand towel over the other cats, especially the returning cat’s closest companion, with attention to the cheeks, to re-share the family scent.
• Keep familiar items where it is safe. The AAFP redecoration and moving-house entries advise keeping the cat’s own furniture. Applied to disaster cleanup, that means leaving a bed, blanket or scratching post alone if it is safe, so the household still smells like itself when the cats return. Items exposed to floodwater, smoke or ash go; that call belongs to the returning home checklist.
• Do not plan on washing the smell off. The IAABC list includes bathing the returning cat to remove foreign odors, with the note that it introduces other foreign odors, which some have found problematic. If bathing is needed to remove ash or floodwater, that is a hazard decision made for a different reason.
• Carrier-train before the season. The IAABC list includes carrier training, and AAFP Step 3 assumes carriers the cats are very comfortable in. Our page on getting a hiding or scared cat into a carrier covers capture, and our multi-pet emergency planning guide covers staging carriers before an order lands.
• Get the discharge details. If a cat comes home from a facility, ask what it was treated for, what it ate, and whether and when it was sedated. All of it feeds the veterinary examination. What happens when your pet is at a facility when the order hits covers the custody and contract side.

When it does not resolve

The AAFP says veterinary professionals should be able to recognize, triage and offer first-line advice on intercat tension and to decide when to refer to a board-certified veterinary behaviorist. Its algorithm says that if the first aid kit does not resolve the problem sufficiently, a behaviorist consultation is advised, along with a recheck examination of the cats. The ASPCA names three credentials to look for: a Certified Applied Animal Behaviorist (CAAB or ACAAB) or a board-certified veterinary behaviorist (Dip ACVB).

The American College of Veterinary Behaviorists describes itself as the certifying board for veterinarians with specialty training in animal behavior, with board-certified specialists called Diplomates. It says they are trained to address the relationships between an animal’s health, environment, experiences and behavior, and are licensed to prescribe psychotropic medications when indicated. Use its directory of Diplomates at dacvb.org rather than a search engine. The same escalation ladder for wider behavior change is in our page on pet behavior changes after a disaster.

Then there is the outcome nobody wants to print. In severe cases with persistent animosity, the AAFP guidelines say serious consideration should be given to a home that allows permanent separation of the cats, noting that microchip-activated cat flaps on internal doors can help, or, as an alternative, rehoming one or more cats into an environment without other resident cats. Their box on that decision begins: “Not all cases of intercat tension can be resolved.” They add that the decision to rehome is the caregiver’s, with the veterinarian guiding the process and minimizing the stress of it.

The ASPCA reaches the same place: “Some cats simply cannot live together peacefully.” Rather than force them to suffer years of stressful coexistence, it says it may be more humane to keep them permanently separated in the house or find another home for one. Nothing on this page guarantees your cats will be a pair again, and the sources that know the most about this decline to guarantee it too.

Checklist

• Separate the cats first, using a barrier rather than your hands. Cornell says never to put a hand or any other body part between fighting cats.
• Do not approach, comfort or reprimand an aroused cat. The AAFP and the ASPCA both warn that it may redirect onto the nearest person.
• Check every person and every cat for injuries. A cat bite on a person needs medical care; a bite on a cat needs veterinary care.
• Call your veterinarian and book the examination. It is item 1 of the published first aid list, and you do not skip it because the cause looks obvious.
• Tell the veterinarian where each cat spent the displacement, for how long, whether it was sedated, and what it was treated for.
• Give each cat its own room with its own litter box, food, water and bedding while you wait.
• Let them settle before any behavior work. The AAFP cool-down window and Merck’s calm-first rule both come first.
• Start with scent, not sight, and follow the one sequence your veterinarian points you to instead of blending four.
• Keep sessions short and end them the moment either cat shows distress.
• Repeat a step rather than advance on hope. Rushing is the error the guidelines name.
• Feed them apart, with a visual barrier, until the protocol says otherwise.
• Add nothing to either cat, including calming products, without asking the veterinarian.
• If it does not resolve, ask for a referral to a board-certified veterinary behaviorist and use the ACVB directory.
• Before the next evacuation, decide whether the cats can travel and be housed together, and note it on the same page as your boarding numbers.

Where to go next

This page is the reunion spoke of our multi-pet emergency planning hub.

• Getting them out. The room-by-room plan for evacuating multiple cats covers capture order and the sweep, getting a hiding or scared cat into a carrier covers the animal that will not be caught, and whether two cats can share a carrier covers the question this page’s scent discussion keeps touching.
• The separation itself. Choosing and timing emergency boarding and the emergency boarding checklist cover where a cat goes and what the facility wants. What to do when your pet is at a facility when the order hits covers a separation that was not your choice.
• Coming home. Returning home with pets after a disaster runs the hazard sequence before any animal leaves the vehicle, and pet behavior changes after a disaster covers the wider set of changes and where the escalation ladder goes.

One thing costs nothing this week: write down, on the same page as your evacuation numbers, where each cat would go if you had to split the household, and ask your veterinarian at the next appointment what they want you to do on the day the cats come back.