If you were outside in the cold, you’d want to find a nice warm place to shelter in. Mice are no different. Compost heaps can offer warmth, protection and quite possibly some food too. Sounds perfect (for a mouse!)
Unfortunately, humans are not always so keen on mice in the compost heap. But is it a problem? And if it is, what can you do about it? Let’s find out…
How big a problem are mice in compost?
Chances are, if you have a large garden, you’ll have mice (and rats!)
Gardens are full of bulbs, seeds and other nutritious and delicious snacks that mice love. You might dent their population, or even eliminate them for a while, but you’re unlikely to get rid of them permanently. Plus, it’s worth bearing in mind that mice can attract and provide a source of food for other predators such as owls and other birds of prey, which should act as a natural check on their population.
Personally, there’s two things that motivate me to have a crackdown on mice. The first is when I plant my broad bean seeds in the autumn, as the little blighters love burrowing into the soil and digging up the seeds. The second is when they start nibbling at my peas and stripping open my mange tout.
Diseases From mice
More seriously, mice can spread diseases. There’s a long list of diseases that they can spread, and these include Hantavirus, Salmonella and Lymphocytic Choriomeningitis. They also carry ticks which can in turn themselves carry diseases such as Lyme Disease. (Source: Elrich: Are mice dangerous?.)
Bear in mind that many of the sites that warn about diseases from mice and other rodents are pest control sites, which obviously have an incentive to hype the danger. It’s hard to know just how serious the threat it, but to put it in perspective Hantavirus, which is commonly mentioned on pest sites, is extremely rare amongst humans, at least in the UK. (Source: BBC – Hunting the elusive hantavirus.)
At the end of the day, you might be able to control mice numbers, but mice will still be able to enter your garden. So if you’re worried about disease, the best solution is probably to ensure you wash your hands properly after turning your compost heap.
That said, here’s … ways you can control mice if you need to.
How to stop mice in the compost heap…
You’ll often see recommendations to proof your compost bin with wire. Now, this might work for rats but mice are extremely good at getting into small spaces. With their super flexible skeletons, a mouse can squeeze through a 6mm gap – that’s about the size of a pencil. You can, however, get a special mouse-proof mesh.
If you don’t want to go down the mesh road, am alternative would be to source an enclosed compost bin made out of gnaw-proof materials, such as the Hot Bin or a compost tumbler.
2. Hose them out
I haven’t tried this method before, but Garden Organic suggests soaking your compost heap with water.
“To get rid of them, soak the heap several times over a period of a few days. An easy way to do this is to flood it using a hosepipe. Once the material is totally wet, the mice should move to drier accommodation.” (Source: Garden Organic: Mice in the compost heap.)
One problem I could see with this is your compost heap would get too wet, disturbing the composting process and potentially delaying the time until you get finished composting. The perfect consistency of your compost should be that of a sponge – after you have wrung the sponge out. Of course, if it’s in the middle of summer and you’re in a heatwave, things might be different.
3. Planting Mint
The idea of planting mint to deter mice is attractive. Do the job once and you have an on-going mouse-prevention system in place. However, I’ve always been sceptical about whether mint would actually work. Perhaps I’m biased after other companion planting experiments I’ve tried haven’t always worked.
But in the course of researching this article, I discovered the experiment below. This did use concentrated peppermint oil, with a stronger smell than a plant, but the results are encouraging. Perhaps mint would work! (Do remember that mint spreads like wildfire, though, and is best constrained to large pots.)
4. Turning the compost
One way to discourage mice is to turn your compost on a regular basis. This might not stop them from visiting for a snack. However, it is likely to stop them from making nests and breeding in it. Turning your compost regularly is more work, of course, but it also has the advantage of aerating the compost pile and producing compost more quickly. It can also help with…
5. Hot Composting
If you’re compost is big enough, and you have roughly the right measure of greens and browns, you should be able to get it hot. Hot compost can be too hot to touch, let alone for a mouse to take up home, and even if it doesn’t get that hot, it will rapidly reduce the attractiveness of any food you are adding.
6. Use a Bokashi bin for cooked food
Cooked foods, cheese, dairy products and meats can emit strong, attractive smells for rodents. But it’s far more fun to turn these products into compost than throw it out into the trash.
One option for dealing with this is to use a Bokashi bin. Bokashi bins offer two advantages – they have a tight seal, and rodents are said to dislike the pickling smell the brewing compost goes off.
It could be possible for a rodent to gnaw its way into a Bokashi bin, but I have yet to experience this with my own Bokashi bins.
7. Bury food waste deep
If you put food waste in your compost heap, it’s well burying it deep in the compost pile. This might not guarantee mice won’t find it, but it will mean the food is less accessible, and will give off less smells.
I sometimes dump cooked food in my Dalek Bin. There’s usually a fair bit in the bottom, and the sealed top means mice can’t get access from above, even if they do climb the hedge. Fingers crossed, I’ve yet to see any evidence of mice around the bin.
8. Controlling with dogs
Red Gardens has vlogged extensively about dealing with rats, and some of his tips may be applicable to mice.
He originally used a dog to catch escaping rats as he turned the compost. Terriers, in particular, are well known for their ratting skills and will eagerly dispose of rodents, although this might not be for the faint hearted!
(When it comes to mice, it’s not just terriers that will dispose of them, though. I remember by mother’s spaniel wolfing down field mice before we could stop her.)
The traditional method for training a dog to become a ratter is also rather brutal. This involved catching a live rat, putting it in a bin and then putting a young terrier. The rat would then bite the terrier, which then kill the rate and be left with a life-long hatred of rats. I’ve never seen this done, so can’t vouch for it myself (and it’s probably illegal too now).
(As a child I remember my own dog was not so effective. I cornered a rat once, and she grabbed the dog, shook it and let it go. I think she might have got bitten, as she refused to ever go near one in the future – as for the rat, I had to finish it off myself with a metal feed scoop.)
You can see the whole of RED Gardens guide below:
9. Get a cat
The great thing about a cat is that even when it’s not killing mice, the cat could still deter them. Proteins contained in a cat saliva, called MUPs, cause a reaction in mice which can cause them to freeze with fear. I think it’s feasible that having a cat around the garden could deter mice from setting up base.
But cats also have a lethal killing instinct – one they sometimes want to pass on! When I was a child, our house cat would often bring mice into the house for us to examine. These went for being completely dead, to half alive to fully alive – and we used to wonder if it was trying to teach us to kill mice.
Wondering what cat is best? Over on Victor Pest you can find a breakdown of the top ten best cats to kill mice.
Traps are easily available and cheap. In my experience it will put a dent in the mice population, but you’re not going to eliminate them in the garden.
I’ve tried several in recent years. Live traps can be effective, although when I used large ones as a kid I used to catch all sorts of things in them. The problem is you then need to dispose of them. I remember my father drowning rats, which I always thought was horrible. (Rats can access oxygen from trapped air molecules in their fur, which means they can live quite a while after being put in water.)
In the past I’ve also used electric traps in a greenhouse, which worked well, although as my step father learned, if you put your finger in to see if it is working it can give you quite a jolt! I do like the little plastic ones that are easy and safe to set (just push back on the back), and when I did catch my finger in them once it didn’t hurt me. Traditional mouse traps are effective, but can be a pain to set, and it’s easy to catch your fingers.
Some people recommend wearing gloves when you set traps in order to reduce the smell, although human smell doesn’t seem to put mice off from stealing our food. Perhaps more effective for garden mice?
If you do use traps, I recommend covering it with a bucket or pan. Mice seem to be get under these with no problem, but it prevents killing other animals. There’s nothing worse than coming out in the morning to find the Robin that follows you round the garden lying lifeless in your trap…
Poison is highly effective. What’s more, mice and rats just love the bait that the poison is embedded in. So, using poison is a highly effective solution for getting rid of furry pests.
The problem is that it doesn’t just kill mice and rats. In fact, one friend told me how, after he put rat poison down, the barn owls from his area disappeared. His theory is that mice and rats ate the poison, and were in turn eaten by the owls, which were poisoned.
If you decide to use poison, the best way to do it is with a bait station. This limits the amount of animals that can access the poison, although it doesn’t stop other creatures from eating the rats later.
Some people find the thought of mice in the compost heap off-putting. But we have lived alongside mice for thousands of years, and that’s not likely to stop now. Take measures to stop them if you wish, but bon’t let it stop you from enjoying composting, reducing waste and experiencing the joy and pleasure of growing your own plants in your own home-made compost.
Photo by Zdeněk Macháček