I met my first minotaur beetle recently. It was a male and he was making his way across my friend’s field, which she manages for wildlife. I stopped and watched him for a few minutes. He walked with purpose and determination, and I admired how he seemed to know exactly where he was going. I congratulated my friend on her rewilding efforts and then dutifully added the sighting to the biological recording site, iRecord.
In Greek mythology, the Minotaur was a monster with the body of a man and the head of a bull. He lived at the centre of the Labyrinth, and was eventually slain by Theseus, who navigated the Labyrinth with the help of a thread given to him by the King’s daughter, Ariadne.
His beetle namesake is so-called thanks to the male’s bull-like horns, which protrude from either side of his pronotum (the plate-like structure that covers the thorax), with a smaller one in between. The female has pointed stumps instead of horns, giving the illusion, perhaps, that she might one day grow horns of her own.
My friend’s field is a dung-beetle paradise. It’s never ploughed or fertilised, and there are two pet horses (never treated with wormers), along with wild deer and rabbits – plenty for a young minotaur pair to start a family. On my next visit I will head to the field to search dung for signs of these fascinating beetles. I wonder if I’ll find any, and who else might live in these piles of waste we rarely acknowledge but around which so much of our world turns.
How do minotaur beetles mate?
One of Britain’s 60-odd species of dung beetle, the minotaur emerges as an adult in autumn and then feeds up, to be in good condition for breeding. Once ready to breed, pairs are established, with males typically locking horns to fight for females. The male and female work together to dig a burrow beneath the dung of rabbits, sheep, deer and horses. They overwinter together in their new home before mating and laying eggs from late winter to early spring. How lucky I was to see one, when they spend so much of their time tucked away underground or immersed in piles of dung.
Minotaur burrows can be up to 1.5m deep. Inside is a maze-like network of side chambers, which both adults stock with dung dragged in from the supply above.
After mating, the female lays eggs on the stored dung – usually one egg per chamber – and the grubs feed on it, while the male guards the nest, using his large horns to fend off would-be intruders. After completing their parental duties in late spring or summer, both adults die, and the larvae pupate. They emerge in autumn to start their own search for a mate and requisite pile of dung.
Why are minotaur beetles important?
Dung beetles are ecosystem engineers, burrowing species that help to aerate and fertilise the soil. By eating dung, they help to prevent the release of methane into the atmosphere, and it’s also thought dung beetles reduce parasite burdens in livestock. Being small, the adults and larvae are an important food source for other species, including bats, owls, hedgehogs and starlings.
Why are dung beetle populations declining the UK?
Dung beetles are declining in the UK, with a few species already thought to be extinct. Reasons include change of land use, which removes habitat; the overwintering of livestock in barns rather than fields, which reduces the availability of dung; the ploughing of fields, which destroys dung beetle nests; use of veterinary wormers in farm animals, which can poison and even kill dung beetles; and the removal of dung from horse paddocks, which destroys the breeding efforts of those who may be using it (I hope I haven’t been guilty of this in my quest for horse manure for my allotment).
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Top image: minotaur beetle. Credit: Getty