What The Mice Do When The Cats Away?

Cats and mice have long had a storied rivalry. In children’s cartoons and other pop culture depictions, mice are often seen scurrying and hiding from cunning cats. But is this really the case when cats are not around? How do mice behave when the proverbial “cat’s away”? Recent research has shed light on some fascinating changes in mice behavior in the absence of feline predators.

Mice Become More Active

When cats are not around to pose a threat, mice tend to become much more active in exploring their environment. According to research from Midway Pest Management, mice are naturally curious creatures that like to investigate their surroundings, but this behavior is limited when cats are present because mice fear being captured and eaten.

With the cats away, mice feel emboldened to venture out from their nests and tunnels to scope out potential food sources and interact with other mice (Will Mice Stay Away If You Have Cats?, n.d.). They will explore new areas of the home looking for crumbs and leftovers to eat.

Additionally, mice engage in more play behavior when cats are absent. Young mice especially like to wrestle, chase each other, and practice agility skills while cats are gone (Do Cats Keep Mice Away?, 2021). This helps them develop muscles and coordination.

Mice are also very social and use play time to bond with other mice. They gather together in groups to play fight, groom each other, and communicate through squeaks and body language. The freedom from being hunted by cats allows them to socialize without fear (Will mice leave a house if they simply smell cats?, 2015).

Mice Seek Food

When cats are away, mice become bolder in seeking food outside their nests. According to one source, mice are attracted to warmth and shelter, so they may linger in rooms even without food present [1]. With the cat absent, mice are able to explore more freely in search of food.

Mice are opportunistic eaters and will seek out any available food sources. They become emboldened to approach new food sources they previously avoided when the cat was present [2]. This can lead to mice getting into cupboards, trash cans, and other areas to look for food.

Mice Breed More

When cats are away, mice tend to breed more frequently and have larger litters. This is because the absence of predators leads to increased mating activity. According to the Terminix website, “This quick maturation process gives mice immense breeding capabilities. Living indoors enhances these capabilities, since they can then breed all year long.”

Mice reach sexual maturity very quickly, enabling them to reproduce at a rapid rate. As explained on the Batzner Pest Control website, “This quick maturation process gives mice immense breeding capabilities. Living indoors enhances these capabilities, since they can then breed all year long without seasonal shifts affecting mating” (https://www.batzner.com/resources/blog-posts/the-rapid-reproduction-rate-of-mice/).

When cats and other predators are not around to hunt them, mice are free to mate and produce larger litters. The average litter size for mice is 5-6 babies, but litters can contain up to 12 baby mice when predators are absent.

Nesting Behavior Changes

When cats are away, mice tend to build more elaborate nests and rearrange their nesting areas more frequently. Mice normally construct nests out of soft materials like shredded paper, cotton, or dried grasses. These nests allow mice to rest, breed, and care for their young.

With cats absent, mice may expand their nests and incorporate more materials to make larger, thicker, and more insulating nests. One study found that lab mice built nests with up to twice the volume and weight compared to normal when cats were not present in the area (source:https://www.smithsonianmag.com/smart-news/once-a-toxoplasma-parasite-infects-mice-they-never-fear-cats-again-9757150/).

Additionally, mice may rearrange their nesting areas more frequently, moving nesting materials from spot to spot. Without the perceived threat of cats, mice can be more adventurous in seeking out choice nesting locations.

Mice Vocalizations Increase

One of the most noticeable changes in mice when cats are away is an increase in vocalizations. Mice rely heavily on vocal communication, using squeaks and ultrasonic sounds to connect with each other, navigate, and express alarm when threatened (1). Without cats around preying on them, mice tend to become much louder and more vocal in their day-to-day activities.

During periods of play and social interaction, mice make more frequent squeaking and singing sounds (2). This chattering helps strengthen social bonds between individual mice. Overall, mice colonies become significantly louder when the threat of cats is removed. There is more singing, squeaking, and chirping throughout the day and night (3). While mice are naturally very quiet and try to avoid detection, increased vocalization is a clear sign they feel less pressure to keep silent and stay hidden when predators go away.

Grooming Habits Improve

When cats are away, mice have much more free time available to devote to grooming themselves. With predators absent, mice do not need to be constantly on high alert, scanning for threats. This allows them to relax and carefully clean their fur, removing dirt, dust and parasites. Thorough grooming keeps a mouse’s coat shiny and healthy.

Researchers conducting the famous “Universe 25” mouse utopia experiment in the 1970s observed that with unlimited resources, space and no predators, mice spent increasing amounts of time on grooming behaviors. The extra grooming resulted in mice having shiny, clean coats.

Improved grooming also benefits mice by reducing disease transmission. When mice can meticulously clean themselves, they remove ectoparasites like mites that can spread illnesses. Keeping fur neat and tidy also prevents the buildup of mold, fungi and bacteria that could cause skin conditions or infections.

Mice May Fight More

When cats are away, mice may engage in more fighting and aggressive behavior towards each other. According to research from West Virginia University, unfamiliar male mice often fight when combined together and should not be housed in the same enclosure[1]. The absence of predator threats can lead to increased competition between male mice over resources like food, water, nesting areas, and mates. Male mice are extremely territorial and will fight to defend their territory and access to females.

Studies have shown that around 14% of group-housed male mice exhibit fighting behavior[2]. The fights can be quite vicious and even lead to injuries and death in some cases. Without cats present to keep mice focused on survival, the mice turn their aggression towards each other. The fights tend to be worse when new mice are introduced or when mice are overly crowded.

To reduce mouse in-fighting, experts recommend housing male mice separately or in compatible pairs. Providing adequate space, enrichment activities, and resources can also help minimize aggressive competition between males. But ultimately, the mice are more likely to fight each other when the cat threat has been removed from their environment.

Danger Response Declines

Without the cat around to keep them alert, mice may experience a decline in their danger response. Since the cat is a constant threat that keeps mice on high alert, mice likely react more quickly to potential threats when living with a cat. Mice have a strong instinct for detecting and responding to danger as a key survival mechanism. However, without practice identifying threats and reacting, such as escaping from the cat, the mice’s danger response can become slower.

According to research from the journal ScienceDirect, exposure to predator odors and cues leads mice to modify their behavior and movements to be more cautious and avoid risks that could lead to being detected by predators. Without these consistent cues from the cat, mice become generally less anxious and reactive over time.

As stated in an article from Quora, mice and other prey animals innately feel fear and react to potential predators as an adaptive trait hardwired by evolution. However, without the imminent threat of the cat at home, mice will gradually feel less on edge and anxious in their environment.


In summary, when the cat is away, mice tend to become more active and exhibit changes in behavior. They seek out food more often, breed more frequently, alter nesting habits, increase vocalizations, improve grooming, fight amongst each other, and have a reduced danger response. While the cat’s predatory presence normally keeps them inhibited, its absence allows their true social, reproductive, and survival instincts to emerge. This reveals the opportunistic and adaptive nature of mice. Much like humans, they modify their lifestyles and habits when external constraints are lifted, whether consciously or subconsciously. Just as we might stay up later, eat more junk food, or slack on chores when a parent or supervisor is not watching, mice take advantage of the cat’s absence to participate in activities that would normally carry too much risk. Their behavioral flexibility speaks to an ingrained drive to capitalize on circumstances for the sake of individual and group prosperity.

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