Written 10/01/2021, Last updated 13/09/2024

Natural habitat and enclosure design- 

Harvest Mice have an extensive natural range covering 2 continents: Europe and Asia. Across this vast expanse the species has evolved to thrive in a variety of differing habitats, including some created- and managed- by man. These include grasslands, meadows, cereal crops, hedgerows, and reed beds. These mice spend much of their time off the ground, navigating branches, or the stems of grasses and reeds. Grass is the main life support system for Harvest Mice; they use it for food and shelter, eating its seed heads and cereals, and creating spherical nests out of shredded living stems. This must all be considered when designing suitable housing for your mice. 

Whilst Harvest Mice are primarily arboreal, terrestrial activities are important too, so their tank must be large enough in every dimension. For a group of 4 mice a 45x45x60cm tank would be suitable, however they are incredibly active, so the bigger the better. Mice also breed quickly, they can have several litters a year, each with an average of 6 young. This will need to be considered if you decide to house males and females together. 

A front-opening glass tank is the ideal accommodation for Harvest Mice. These have a screen top which offers plenty of ventilation, whilst preventing draughts, which could cause illnesses. They are also readily available in a range of sizes, easy to clean, and can offer keepers great views of their mice. Conventional rodent enclosures with bars are completely unsuitable for housing this species. 

It is easy to create a naturalistic enclosure for this species, however it does often require a great deal of ongoing maintenance to ensure it remains enriching for the animal and looking great for you. You can see how I have designed my own enclosure here. 

Substrate is the foundation of any enclosure build, and there are numerous options for Harvest Mice. For a naturalistic enclosure I would always use sand or soil, which is also incredibly easy to clean with regular sifting. My preferred products are bird sand and arid reptile soil mixes, but alternatives such as organic gardening soils and washed play sand could also be used. If you are not too bothered about the natural aesthetics of the enclosure, typical rodent bedding options can be utilised. This includes paper bedding and wood shavings. 

Climbing opportunities are vitally important to allow the mice to exhibit natural behaviours and remain fit and healthy. There are plenty of things you could include for your mice to climb over, such as: 

• Branches 

• Logs 

• Rocks 

• Rope 

• Grass stems 

In my own setup I use most of these, along with old fencing and plenty of fresh browse. 

Harvest Mice may be small, but they can be incredibly destructive to certain materials, especially live plants. We did trial planting grasses and wildflowers in our setup for a brief time, but these were quickly nibbled until nothing but roots remained. Instead, I would recommend collecting grass stems, and branches/browse from your local area as often as possible. This allows plenty of enrichment through new scents and tastes, as well as opportunities to climb, feed naturally, and perhaps even build their nests, which would naturally be found between 30 and 100 centimetres off the ground. On a much larger scale I was able to create an enclosure for zoo-housed Harvest Mice in which the mice created and used natural nests! 

Some safe plant species to use for natural browse here in the UK are hawthorn, hazel, apple, willow, bamboo, and buddleia. 

Whilst every keeper hopes their mice will utilise these natural materials to create nests, it is unfortunately quite rare, so keepers should ensure that artificial hides are available. I usually use hollow coconut shells, which represent the natural spherical nests made by the species. It is recommended to have at least one hide for every mouse in the enclosure to avoid conflict. This is particularly important in bachelor and breeding groups. 

Within the setup you will also want to ensure that you have space for a food bowl, and a bowl or bottle for water. 

Environmental conditions- 

Harvest Mice will not require any additional heating or lighting, but it is still important to be mindful of their tolerance to varying environmental conditions. 

Draught from windows and doorways should be minimised as much as possible, and the tank should be situated away from any areas of the home where this cannot be done. Although a front-opening glass tank will offer protection against excess air flow, it is worth being cautious for the health and welfare of your animals. 

Similarly, avoid situating a tank in a window. Not only might this area be draughty, but a glass tank will quickly overheat in the sun, potentially risking the lives of the animals inside. Instead find a well-lit, protected area of the room. 

The use of UVB lighting (commonly seen in herptile setups) is becoming more common in mammal enclosure design. At this stage the research into its benefits for captive mammals is still ongoing. As a result, this inclusion of suitable UVB lighting would be at the discretion of individual keepers. 

Diet and captive feeding- 

Wild Harvest Mice are considered omnivorous, yet their diet consists mostly of seeds and grains. This is what we use in captivity to form the basis of their diet. I would recommend a reasonably low-fat seed mix- for example canary seed- which is readily available in most pet shops, and even online. Fatty seeds such as sunflower seeds can be fed as part of the diet, however it could cause obesity if it is fed too frequently, and the mice have limited room to exercise. 

Millet sprays are commonly used when feeding Harvest Mice. These would make up part of the species’ wild diet and can be hung from the top of the enclosure to encourage natural feeding behaviours, and the use of their prehensile tail. 

In the wild, the species will also eat berries and invertebrates, which can be offered in small amounts in captivity. A great way to provide berries is through the browse you add to the setup. Throughout the year many UK native plant species, for example hawthorn, grow berries. These can be left on any branches you give to your mice, giving them a free and enriching food source. 

Live invertebrates can also be placed in bowls or scattered around the enclosure for the mice to scavenge. These mice have been known to eat grasshoppers and various other species- great alternatives for your captive individuals are small locusts and mealworms. If you would rather not use live feeds, dried mealworms made for birds can also be used, but these tend to have little nutritional value. Some research suggests that Harvest Mouse diets vary seasonally, with the species consuming more invertebrate prey in the colder months. Whilst further study would be needed to help verify this, offering some seasonal variation to the diet in captivity could be beneficial, and perhaps more representative of the species’ wild habits. 

Alongside this varied diet, a bowl or bottle of fresh water must be available at all times and replenished regularly. If you opt to use a bowl for water, beware of the risk of drowning. Harvest Mice are a tiny species, so any open water should be shallow and have precautions in place to prevent drowning- for example stone chippings, marbles, or pebbles. 

Wild behaviour and enrichment- 

Harvest Mice are generally considered a social species, found in groups in the wild. This should be recreated in captivity, with keepers avoiding housing mice on their own. As previously mentioned, the species breeds quickly, so keepers may wish to opt for same-sex groups. Aggression may be seen in these groups, which is a natural behaviour. Providing plenty of different visual blocks in the setup, as well as numerous hiding opportunities, will reduce these behaviours, but it is important to closely monitor individuals should injury occur. 

Dietary enrichment is one of the easiest ways we can further enrich our mice. Keepers should consider not only offering the wild diet but presenting it in a natural way. When feeding live foods, these could be scattered across the enclosure or hidden beneath enclosure features such as leaves, which will encourage the mice to use their senses to search for their food. Even feeding seeds can be made more enriching with a small amount of work. High-value foods, such as those high in fat, could be hidden in the same way, or even concealed in simple puzzle feeders. The food bowl can also be placed in various locations around the tank to avoid predictability, or even suspended from the top of the enclosure to mimic the way in which wild mice will feed above the ground. 

Furthermore, sensory enrichment is also easily provided by the regular replacement of branches and browse. This will bring new scents into the enclosure and encourage explorative encounters which may otherwise disappear in a stagnant setup. 

Health and disease prevention- 

Regular cleaning is important to ensure that your mice remain healthy. I remove all waste, food and seed husks several times throughout the week by running the substrate through a fine sieve. In a naturalistic enclosure with regular spot cleaning, a full clean is only necessary every few weeks. Harvest Mice tend not to have a strong odour- unlike other rodents- so odour in the enclosure would be a sign that a full clean is required. 

This species is susceptible to many of the same common ailments as most other rodent species. Daily visual health checks, as well as occasional physical checks are recommended to ensure that any health concerns are addressed as quickly as possible. As a prey animal, it is likely that Harvest Mice will not show signs of illness or weakness until the health problem has become advanced. 

Common signs of illness include: 

• Lethargy 

• Loss of appetite 

• Unusual faeces 

• Reduced/increase defecation or urination 

• Abnormal discharge 

• Dull, sunken eyes 

• Unusual, rapid, slow, or loud breathing 

• Red, sore skin 

• Excessive itching 

• Self-mutilation 

It is also important to remember that, as with all rodents, the teeth of this species grow continually throughout their lives. This means that without the appropriate diet and enclosure furnishings they could quickly become overgrown, causing discomfort, injury, or preventing the mouse from eating.