It’s the last day of July, which means we must watch our Animal of the Month – the mouse – scurry out of the spotlight. Mice are fascinating rodents and often don’t get the credit they are due when it comes to how amazing they are. We tweeted all month long @ExoticPetVets about mice, but if you missed any of our tweets you can find a summary right here. Did you know?:

• There are many species of mice, but only one species has been widely domesticated and is typically kept in captivity as pets or in laboratories and that is the house mouse (Mus musculus).
• It’s believed the house mouse originated from central Asia and has spent thousands of years spreading all over the world.
• Wherever you can find humans, you can find mice. House mice who are not kept as pets use human food and shelter in order to survive on their own. This is what’s called a commensal type of relationship.
• But, as we know, many people keep mice in captivity as pets, which changes the dynamic to a domestic or familial relationship.
• Because house mice live in such close proximity to humans, mice are able to live in harsh environments that they may not otherwise be able to live in on their own; such as tundra or desert.
• House mice are small and slender rodents. Adult mice typically have a body length of about 6.5 – 10 cms (2.5 – 4 inches). Their long tails pretty much equal their body length.
• The long tails of house mice look like they are bald, but they actually have a little bit of hair on them. Their tails also have rows of scales on them.
• House mice have small heads with triangular snouts and thin whiskers. They have small, usually black, eyes.
• House mice have great hearing ability and have round ears that are large relative to their head size. Their ears are like their tails in that they also look bald, but have a bit of fur on them.
• House mice naturally have light brown or grey short fur with white or buff-coloured fur on their bellies. Selective breeding has resulted in many different fur colours and patterns for domestic house mice.
• House mice have front feet that have four toes. Their hind feet have five toes and are narrow and larger than their front feet. All of their feet have short claws.
• It is widely known that mice can reproduce very rapidly. Mice are considered adults at just 5-7 weeks and can start reproducing at around that age.
• House mice mate according to a system known as polygyny, which means a male house mouse will mate with multiple females. Male mice will sing songs (at a frequency that humans can’t hear) to attract females.
• House mice can breed all year round. In a year, just one female can have up to 10 litters that typically consist of 5-6 babies.
• When not kept in captivity, house mice will burrow and make elaborate homes for themselves underground, which helps protect them from predators.
• Mice are also skilled in home organization. In their underground burrows, they will designate specific areas for things like sleeping, storing food and going to the toilet.
• People falsely believe that mice are dirty. In fact, mice are very clean animals. They will groom themselves and when they are in captivity, they can be trained like rabbits or cats to use a litter box.
• As the world grapples with the COVID-19 pandemic, mice are playing a part in the development of a vaccine for the virus.
• Mice and humans both have the ACE2 protein, which COVID-19 latches onto to cause infection. But mice can’t naturally get infected with COVID-19 like humans can because the ACE2 protein is different in mice.
• U.S. researchers are introducing a version of the human ACE2 protein into mice, which temporarily lives in the mice for a few days.
• The researchers are infecting these mice with COVID-19 in order to develop a vaccine. While the mice are falling ill with COVID-19, all of them are making complete recoveries.
• The research on mice and COVID-19 was reported in June 2020 in the scientific journal “Cell.”
• Mice made headlines in April 2020 after an amazing discovery was made about them that adds another similarity between mice and humans – Mice have the ability to make facial expressions.
• Researchers at the Max Planck Institute of Neurobiology in Germany found that mice express disgust, happiness, pain, fear, nausea and flight on their little faces.
• The researchers used computer vision technology to look at the face of the mice and two-photon imaging to look at their brain activity when they were presented with various stimuli.
• Not only were the facial expressions on the mice changing with their emotions, the researchers found the brain activity matched the strength and timing of their facial expressions.
• The researchers also found that the same brain regions are active in mice and humans.
• These findings build upon previous research that shows mice also feel empathy. This most recent study adds more evidence that mice have rich emotional lives.
• It has also been suggested that the study results on mice can also help improve the understanding and treatment of mood disorders in people.
• Mice have a very long list of predators, which run the gamut from birds to reptiles to other mammals – and even some arachnids on occasion.
• Most of us learn as children that cats are a primary predator of mice. But mice can also count certain types of birds (such as owls), snakes, large lizards, ferrets, foxes, weasels and – of course – humans among their predators.
• Mice evade predators by avoiding being out in the open. They are also extremely fast, excellent jumpers and climbers and can squeeze through seemingly impossible tight spaces.
• Because of the number of predators mice have, their ability to reproduce quickly could be considered a defense mechanism of sorts because it protects their population numbers from being decimated.
• Mice who are kept in captivity as pets under ideal conditions have an average lifespan of two years.
• Because mice have so many predators, in the wild they usually only live about six-months to a year.

This is the second time we have featured mice as our Animal of the Month. Check out our blog post from June 2016 to see our tweets about mice the first time they were our featured creature!