Finding and Identifying Dung Beetles
Identifying dung beetles to genus level is easy to do, see figure 1 below, but identifying to species level is more difficult and often requires microscopy and an expert to do so.
When searching for dung beetles, the first thing you need is dung. You can perform a manual search by simply pulling apart dung and seeing what emerges, however there are other methods too, such as the flotation method (see below). When sampling dung, there are also many other invertebrates as well as dung beetles that you may come across. See what else you can find in dung
Disclaimer: When surveying for dung beetles, we strongly advise that you wear gloves, and wash your hands and any equipment you use, to reduce the risk of spreading diseases between farms.
The colour of dung beetles can be very variable and may be an unreliable feature to use for identification. As a starting point, we would recommend that you categorise any dung beetles you find to genus or family (Aphodiines, Onthophagus and Geotrupidae). Firstly, you should separate dung beetles by size, the largest individuals (over about 13mm) will only be Geotrupidae. The next feature you should look at is the general shape, with Onthophagus beetles being generally more rounded, and Aphodiines beetles tending to be longer and pill-shaped (see figure below).
Figure 1 General representation of the three groups of dung beetles with body shape for Onthophagus and Aphodiines illustrated above.
Given that the majority of Aphodiine beetles are dwellers, and Onthophagus or Geotrupidae beetles are tunnellers, simply identifying dung beetles to these three families can provide very useful information
Finding dung beetles
To find out what types of dung beetles you have, we recommend that you undertake some dry sieve sampling of dung pats, or bucket/water sampling (the flotation method) if the pats are wet.
The water sampling process involves collecting a dung pat and placing it in water. Sampling should include some soil from under the dung pats for Onthophagus & Aphodiines as well as Geotrupids. Although Aphodiines live in dung pats they will hide in the soil under it as well. Geotrupids have deep tunnels so can be under-sampled in dung pats. If you see big tunnels under or next to a pat you can dig down to try and get them out; or even just record the number of holes as an indication of the abundance of Geotrupids.
Any dung beetles within the pat will float to the top; take care not to drown the dung beetles. It is recommended that you use a sieve to skim off beetles after agitating the dung in the water with a stirrer. Beetles can hide in air pockets in the dung if it is not broken up.
Take photographs to assist with identification of anything you find. We recommend releasing what that you catch and only taking a few samples to minimise disturbance to the dung beetle population. For those intent on species identification for more professional purposes voucher specimens of each species may be needed.
Surveying dung beetles
There is no 'standard' best practice for surveying dung beetles, particularly as there is such a variety in the behaviour of the different species.
Dung beetles can arrive to a dung pat within the first hour of it being on the ground, but which species you find will depend on the time of year as different species are active in different seasons. Different species also inhabit dung at different stages of decomposition, so you will need to sample a variety of dung pat ages.
Dung beetle species and numbers will vary with time of year, soil type, grazing management, soil and air temperatures and shade. So, a good practice is to select a number of different sampling points across the farm that cover the different habitats you have e.g., shaded areas, open pasture, grazed scrub and also bare soil (by a trough or gate). By selecting a number of different habitats, you are increasing the chances of surveying the more specialist species & not just the generalists.
Once you have chosen your sampling sites, we suggest surveying 4 times a year to collect complete species data, April/May - July/August - September/October - January/February. Then repeat each year at the same times, in the same locations to be able to get comparable data over time and space and to track trends in populations over time.
If you would like to know what species you have, we would encourage you to send in your records to iRecord where they can verify or correct your identifications.
The British Scarabs website is a good resource for identifying dung beetles, with some useful guides to help narrow down what you may have.
As with identifying any invertebrates, getting to know the anatomy is crucial. There are a number of useful books which can help you get started with identifying dung beetles e.g. (Jessop 1986)