For Day 11 of the 30 Days Wild challenge, I am focussing on a group of insects few would consider to be at all glamorous: Dung Beetles. In reality, though, the Scarabids are a vitally important family of beetles that humbly go about their business and provide a plethora of valuable ‘ecosystem services’.
They are an integral cog in the process of decomposition, making precious nutrients available for plants to use; are a vital food source for many species at higher trophic levels; greatly improve soil structure and drainage; and even reduce the prevalence of disease by lowering the number of dung-breeding flies.
Dung Beetles are also just very cool insects generally! Here are some fast facts:
- there are three main dung beetle lifestyles which helps avoid competition for the same resource: the famous dung-rollers called teleocoprids; beetles dwelling within dung (endocoprids), and those tunnelling away beneath the dung (paracoprids)
- dung can be such a scarce resource in rainforests that some species actually attach to the anal regions of monkeys and wait until they defecate, dropping off to the forest floor with the dung!
- Some Teleocroprid Dung Beetles can roll balls of dung over 1000 times their own weight! The record going to Onthphagus taurus, which shifted a ball equivalent to a human shifting 80 tons!
- Detecting volatiles given off by poo, they are incredibly quick at arriving on the scene: one scientist recorded 4,000 dung beetles arrive on a fresh pile of elephant dung within 15 minutes of it hitting the ground
- Research has shown that at least some species use the Milky Way to navigate, perching atop dung balls to orientate themselves prior to rolling its cargo to a nest
All is not well, however, with Britain’s Dung Beetles: a recent report from Natural England and JNCC indicates that 25% of the country’s 60 dung-feeding Scarab species are Nationally Rare following alarming declines, and four species have gone extinct in the last 50 years alone. Why? A cocktail of factors are responsible for their decline:
- changing land uses: from permanent pastureland to arable or crop monocultures and heavy application of chemical fertilisers
- the indiscriminate use of toxic wormers like avermectins to treat livestock
- overwintering livestock indoors and thus breaking the provision of their precious dung
- importing foreign livestock breeds that produce dung too moist for our native beetles to deal with
In response to these worrying declines, a project was recently set up in the UK to understand more about the country’s dung beetles, whilst highlighting their importance through outreach, and involving the public in a citizen science project to identify and record any sightings. So-named ‘DUMP’, the Dung Beetle UK Mapping Project provides great resources for the general public and land managers alike, so head over to their site to check out the info and how you can contribute to the irecord initiative.
So how is any of this relevant to today, or Bardsey for that matter?
Here on Bardsey the functions of dung beetles are closely-engrained in the island’s unique ecology: providing important sustenance for the Red-billed Chough population – a key feature of Ynys Enlli’s designation as an SSSI and a Special Protection Area (SPA), in addition to recycling the copious quantities of crap that our sheep and cows produce.
We have just this year re-started recording the island’s Dung Beetles after the last extensive work was carried out by Dick Loxton back in the 1980s. With the island’s cattle grazing regime set to change in the next year, we want to monitor any repercussions this has on dung beetle populations to ensure we don’t decimate the Chough fodder!
Mum has been diligently retrieving faecal samples (an eloquent word for ‘shit’) of both sheep and cow dung across the island every month this year. We’ve then been trying to identify and note down the relative abundance of any species we find, and submitting the results to the irecord scheme. Today was collection day for June’s sample, so we got stuck in…
It’s been very interesting finding out what species are present on Bardsey after such a gap in recording, particularly when the land management has been so variable over the last 70 years. Cows were absent from the island for several decades, for example, and rabbits went extinct from Myxomatosis back in the late 1990s. Since some dung beetles feed only on the dung of specific animals, the species composition can vary a surprising amount.
Identifying Dung Beetles is not entirely straight forward, even with a great range of resources from DUMP and other schemes. Using dichotomous keys and looking at various obscure anatomical features can be tricky – so we’ve sent off a number of images to DUMP and had useful pointers and verification back. Combining the results, we’ve so far recorded the following species on Bardsey this year:
- Aphodius fimetarius
- Aphodius prodromus
- Aphodius granarius
- Aphodius ater
- Aphodius sphacelatus
- Aphodius stcticus
- Aphodius fossor
- Aphodius pedellus
Species like A. fossor haven’t been recorded on the island before, and some were noted by previous entomologists prior to the removal of cattle in 1972, but not again since. It’s pretty cool to think of such small and bumbling insects crossing a pretty treacherous stretch of water to utilise the excrement of this pilgrimage isle.
Like any other farm in the UK, our livestock suffer from a range of parasites and infections that require treatment. The usual ‘solution’ to this issue is a blanket use of wormers containing avermectins: but these deadly chemicals pass through into the animal’s dung, and so don’t just kill internal parasites – they also kill insects feeding on the dung.
To combat this, we have been trying to be far more specific in how we treat our sheep: identifying the actual parasites causing the issue by looking at poo samples under a microscope. We then use wormers or drenches which target that species; if possible, using chemicals of low toxicity to invertebrates. The benefits are two-fold, helping to minimise the build-up of parasite resistance – a worrying problem that is accelerating across the UK.
One of today’s tasks was gathering a sheep flock to treat the lambs for one such problematic parasite…
Whilst I could go on rambling about the ecology and importance of dung beetles, I doubt many readers would persist much further, so here are a few other bits of news from today:
A new addition to my caterpillar menagerie…
And one of the Six-spot Burnet caterpillars has pupated
There has been a howling southerly gale all day and dazzling sunshine. The waves were pretty spectacular this evening and thousands of shearwaters were gliding by. Many images to come!