Burying Beetles like to recycle too

Burying beetles are probably not everyone’s cup of tea but if you are now intrigued then do read on.

Burying beetles comprise a whole family of beetles called the Silphidae, many of them associated with carrion which means they are important decomposers and recyclers.  They are known as the undertakers of the animal world and without them we would be up to our knees in dead animals. Burying beetles help to dispose of carcases by burying them and laying their eggs close to them and they are used extensively in forensic science to solve murders

Male and female burying beetles are attentive parents and when they find small dead vertebrates they work together to defend the carcase and bury it in a suitable location.  Beetles from the Nicrophorus species are capable of burying carcases up to 30 times their own weight. They will prepare the body by removing hair and feathers, and their gut bacteria produce antimicrobial substances which are spread over the carcase to preserve it.  The female lays her eggs close to the carcase and once hatched, the larvae move on to the carcase and the parents care for them by feeding upon the carrion and regurgitating it for their young.

There are 21 species recorded in the UK and the Silphidae Recording Scheme was set up in 2016 to monitor the distribution and status of these beetles.  They provide an indication of ecosystem health and some of the beetles are considered vulnerable, near threatened or locally scarce or rare.  The main threats are agricultural intensification, pollution, climate change, the use of insecticides both on vegetation and in medication for livestock, and most importantly the removal of carcases which may end up in our bins and at landfill. 

Burying beetles can be recorded by anyone, in your own garden.  All that is required is a quiet corner where you are happy to set up a pitfall trap with a small carcase. 

Dead mice that are used to feed pet reptiles can be obtained from a pet shop or if you find a small dead rodent, bird or rabbit, they will also be ideal.  The bait needs to be matured for about a week in an airtight container or plastic bag so that other invertebrates can’t move in to it first. 

You will then need a plastic tub such as an ice cream tub with some very small holes in the bottom so that water doesn’t collect in the tub but not too large that beetles can escape, some chicken wire on which to place your carcase, and something to protect it all so that the carcase won’t be taken away by a fox or if you have pets who may find it interesting.  A waterproof covering such as a small piece of roofing felt will also keep your occupants and the carcase dry.  

The plastic tub should be sunk in to the ground so that the opening is level with the soil so that the beetles will fall in to the trap but not be able to escape.  The bottom of the tub should also have a layer of leaves so the beetles can hide as some of them will fight to death over their carcase or another predatory invertebrate may fall in that will eat your beetles. 

The trap should be checked at least daily and occupants removed and released as soon as you have identified and photographed them.

I set up this pitfall trap in my garden using a dead rabbit I had found.  It took quite a while for the beetles to arrive as they were still overwintering when I found the rabbit but on the first day of spring the beetles suddenly appeared in my trap.  In total I had three Nicrophorus humator commonly called “The undertaker “or “Black sexton beetle” and eleven Thanatophilus rugosus or “The wrinkled death lover”.  Wrinkled death lovers are smaller beetles which mainly feed on carcases and are common throughout the UK.  The Undertaker is also common and will lay their eggs close to the carcase as described earlier.  Many burying beetles will also be seen covered in small red mites as shown in the photos.  These mites form a phoretic relationship with the beetles where they rely on the beetles for transport as the mites are unable to find their own carcasses.  Once at the carcase they also lay eggs and eat the eggs and larvae of flies which may devour the carcase before the beetle larvae have hatched thus helping the beetles. The mites will then attach themselves to the young beetles and disperse with them to new sites.  

Once I had taken photos of my beetles I released them on to the carcase of the rabbit and left them in a quiet corner under the hedge and removed the trap so I wouldn’t catch the same beetles again.  Within a day the rabbit was already partially buried and by day 2 it had completely disappeared hopefully now home to the next generation of burying beetles.  I will continue to set up traps in various locations as different beetles are abundant at different times of the year.

I am hoping to carry out pitfall trapping in some of our community woodlands over the summer.  If you live near one of our woodlands and would like to get involved then please get in touch with me michelle@bordersforesttrust.org or if you would like to set up your own pitfall traps in your garden you can contact me for more information or send us your photos on Twitter, Facebook or email.

Don’t forget to upload your records to iRecord too to help the Silphidae Recording Scheme.  You can find more information on the recording scheme here //www.coleoptera.org.uk/silphidae/home and there are also useful ID guides which you can download.