One of the most striking things about the African savanna is the amount of animal dung on the ground. Walking through glades where herds of impala had recently foraged or through grasslands and acacia bushland where elephants have wandered, it’s difficult to traverse without crunching on dry dung or unluckily stepping in fresh dung. In an environment supporting high population densities of megafauna and other mammalian fauna, the clean-up crew must be accordingly abundant. My favorite group of insects that fulfill this role are the dung beetles. Dung beetles play a vital role in savanna ecosystems through recycling of nutrients in feces into soil as well as aeration by sheer physical tunneling. It was exciting to see such a high diversity of dung beetles at Mpala, some blue and iridescent and others adorned with horns and protuberances of all kinds of shapes and sizes.
After observing their dung-associated habits, it became apparent that many species specialize on dung from particular mammalian species. The dung beetle pictured above (Heliocopris cf. andersoni) belongs to the genus of the largest dung beetles on Earth. Most Heliocopris feed exclusively on megaherbivore dung, including that of elephants, hippos, rhinos, and also cattle. As large mammal populations continue to decline, without a doubt cascading effects will impact coprophagous animals, nutrient uptake into soil, and consequently growth of vegetation. I only found a single illustrious male with two pronounced antler-like horns on the anterior part of the head, a first for me in scarabs (as opposed to above the eyes or on the thorax). However, females of what I suspect are the same species were pretty abundant, and once I witnessed a female moving a piece of elephant dung into her large tunnel. Females will lay eggs in tunnels crafted beneath the dung, and larvae will hatch to feed on the supplied piece of dung. To dig into the substrate, dung beetles have enlarged and spiked fore-tibia. Just like a mole cricket, it’s easy to appreciate their strength at excavation when confining them between your hands.
We spotted most Heliocopris at night. As these beasts would fly to the dining area lights, we would hear loud crashes of their exoskeletons bashing against the ceiling and floor. As if that was not alarming enough, once they are picked up they emit a loud and persistent squeaking sound. Before travelling to Africa, I had only heard these types of antipredator stridulations in longhorn beetles, so I was surprised to see the majority of large scarabs (and buprestids!) also employing this strategy. The sounds are accompanied by up and down movement of the head relative to the thorax, so the beetles probably have file-like extensions of chitin on one segment that rasp against the adjacent segment, as in the tergites of some ants and wasps.
Dung beetles are well known for crafting pieces of dung into little orbs for ease of maneuver over long distances. Many of them, however, opt out of the neat packing and heave whatever they can get a hold of. This female Heliocopris belongs to the latter group, and made several trips to her nearby tunnel to cram in as much zebra dung as she possibly could. Though less than a meter away, the dung beetle put in a lot of effort to make her way through the dense grasses. Watch a small bit of her journey here along with a few cute tumbles.