How to Build a Bug Hotel or Hibernaculum
What is a Hibernaculum?
Hibernacula (the plural of hibernaculum) are often referred to as bug or insect hotels. They are specially designed structures that offer small invertebrates like solitary bees places to spend the winter where they can stay (relatively) warm, dry and safe from predictors.
As a Landscape Architect I have often built and specified hibernacula of varying types and sizes for varying purposes. The simplest I have prescribed have been simply piles of logs left in a stack after felling trees. Often in gardens a more aesthetic approach is required. In this lens I will show you how you can do your bit for biodiversity and sustainability and build a hibernaculum that not only looks good, but will also provided much needed habitat for wildlife in your garden or yard.
Why You Should Definitely Build a Hibernaculum in Your Yard or Garden
It can't have escaped your attention that the world's population of bees is falling drastically. Whilst there are likely many factors effecting the decline in bees and other insects (such as inappropriate use of insecticides, destruction of habitat, scarcity of food sources etc), I personally believe the loss of over-wintering sites also plays a large part in their decline.
Many insects hibernate over winter in secluded spots in holes in standing deadwood and in soft rock and brickwork. Sadly we have lost a lot of this valuable hibernation habitat.
Why the decline in certain invertebrates is a bad thing
Any decrease in biodiversity has knock on effects that ultimately reduce the resilience of an ecosystem. Put bluntly if a population of just one organism drastically declines the whole system is weakened and can become vulnerable. If this happens other species can become vulnerable. For example if we loose bees we loose our pollinators and our crops don't get pollinated. which means food shortages for us.
But we can help
By building a hibernaculum in your yard or garden you can provide a valuable home to insects, bees, grubs, all sorts. This in turn provides food for birds and hedgehogs etc.
Photo credit: quimby
Wildlife Gardening Resources
A great book for introducing your children to gardening for wildlife
What You Will Need to Build Your Hibernaculum
You will be able to find everything you need free of charge from your neighbourhood
I think the best hibernacula are made of a range of materials to give the widest possible choice for the wildlife in your garden. As I said above I have specified very simplistic hibernacula in the past constructed of nothing more than cut logs, leaf litter and earth. If these are all the materials you have to hand, then you can still make a decent hibernaulum!
Personally I prefer natural materials to make hiberrnacula. You may have seen some constructed using car or truck tyres, plastics, and concrete products. Whilst is possible for creepy-crawlies to make their over-winter homes within these materials I think it is better, both ecologically and aesthetically, to use a pallet of natural materials.
Here's a list of materials that I favour:
Sawn (untreated) timber
Scrap wood such as (untreated) timber pallets or railway sleepers
Wood shavings and sawdust
Newspapers (see note below)
Hessian and sackcloth
Bricks (preferably of the stock variety and not engineering bricks)
Clay roof tiles
Natural stone paving slabs
Its amazing what you can get for free. I once got a beautifully turned wooden display bowl from a green-waste recycling facility (I rescued it before it went in and asked the contractor if I could have it). I cleaned it up, sanded it down, and gave it to my mother as a present.
There might be a temptation to take items out of a skip, bin, dumpster, debris box, or similar. DON'T! Even if the item has been placed within the skip, and the skip/dumpster is on the public highway, it is still owned by the person who has thrown it away. Placing an item within a skip does not actually imply that the owner no longer wants it (legally). I've fallen foul of this myself. Once I was laying a patio at a client's house and loading the excavated debris into a skip on the road outside the front of the house. When I went for lunch I left my wheelbarrow on the skip, so it was out of the way. I came back half an hour later and it was gone!. Of course you can always ask the owner if you can take something from the skip.
Designing Your Hibernaculum
Use of Hibernaculua Materials
The list above is by no means exhaustive, feel free to add any other materials to your hibernaculum. Just make sure they are natural materials/products
I always aim to get a mix of soft and hard materials. I know many other designers will use only hard materials in their hibernacula, but there are two good reasons for including soft materials.
The first reason I believe adding soft hibernacula materials is a good idea is that they are often naturally insulating. The addition of things like straw and Hessian can offer protection against the harshest of the winter temperatures for hibernating wildlife.
The second reason is that these materials are preferred by some species. Whilst some species are happy to hunker down under a rock for the winter, others prefer to burrow into deadwood. Offering a mixture of materials simply widens the appeal of your hibernaculum for local wildlife.
It should be expected that the soft materials within your hibernaculum will degrade over time. This is natural and the best thing for the hibernaculum. Let the materials decompose naturally, and don't be tempted to keep you bug hotel too clean and tidy. Let it age gracefully.
My top tip: Make sure the basic structure of the hibernaculum is constructed of hard materials, or at least soft materials that will last. You often see hibernacula made of pallets and thin wood. Whilst there's nothing wrong with using these materials in a hibernaculum, they will degrade faster than brick, clay, and stone. This can lead to your hibernaculum collapsing prematurely. I recommend building the basic structure of hard materials, making shelves and then filling the shelves with soft materials. That way you will be able to keep the structure for many years and simply replace the soft materials once they have degenerated past to the point where they are no longer useful for wildlife to use for hibernation.
Building your Hibernaculum
How to build a really good bug hotel
Some people recommend lifting your hibernaculum of the ground on bricks or the like. The theory being it helps keep your materials drier, thus slowing their decomposition. Personally I prefer to set hibernacula directly on the ground. This is more natural, and will give easier access for non-flying invertebrates to take up residence. Provided you follow my advice and build the structure out of hard materials it doesn't matter if the soft materials in the lower level rot off quicker.
Start by sraping back the grass or other vegetation. Create a level area, slightly larger than your planned hibernaculum.
Next you are ready to start building the structure.
I like to create a bed of crushed concrete or stone to ensure I can get a level surface to build up from.
You can create the structure using pallets, railway sleepers, or old concrete posts.
You are aiming for a layered approach, like a high rise.
Another way to build the structure is to make side and back walls from, say pallets.
The structure wants to be built so that it will stand up with only the hard (or more durable soft) materials.
Experiment with what you like.
I think a good hibernaculum can be beautiful as well as functional.
Don't be afraid of using garden wire to secure the pieces of the structure together.
Filling the Structure
Once the basic structure is in place you can fill up the gaps with your soft materials.
With logs or other wood it pays to drills holes of varying sizes in the ends to allow easy access for the creepy-crawlies.
Keep in mind the look of the hibernaculum. Take a look at some of the examples I've posted here.