Behavioural responses of Onthophagus squalidus, Onthophagus consentaneus (Scarabaeidae), Saprinus cupreus (Histeridae), and Liparochrus sp. (Hybosoridae) to experimental warming, soil moisture, and dung availability in New South Wales, Australia

Abstract

Climate change and resulting conditions like droughts and extreme heat have resulted in a loss of species diversity. Assessing how ecosystem service providers such as coprophagous beetles cope with these changes is vital to maintaining ecosystem health. The effects of increasing temperature in both moist and dry soil are explored, as is the question of whether dung’s presence (food resource) plays a role. Four beetle species – two dung beetles (Scarabaeidae: Onthophagus consentaneus and Onthophagus squalidus) and two coprophagous (Histeridae: Saprinus cupreus and Hybosoridae: Liparochrus sp.) – are examined. Six beetles of each species were placed inside a heat chamber at four different temperatures: 25 °C, 30 °C, 35 °C, and 40 °C. Each heat chamber only contained one species type, and, for each temperature, beetles were exposed to dry soil with dung, moist soil with dung, dry soil without dung, and moist soil without dung. Beetles were able to leave their chambers at any time and chambers were left active for 168 hours. Results show that Liparochrus sp. always left the chambers before 72 hours, regardless of conditions. Saprinus cupreus was unaffected by temperature and soil moisture, mostly remaining in the chambers for the full 168 hours if dung was available and leaving when not. Both dung beetle species were unaffected by temperature and soil moisture when dung was present. When dung was removed at 25 °C and 30 °C in dry soil, beetles all left the chambers, however at 35 °C and 40 °C most beetles remained in the chambers. All dung beetles left the chambers when soil was moist, and no dung was available at all four temperatures. This paper shows how dung beetle behaviour changes at high temperatures in dry soil, both when food is present and when it is not. In contrast, other coprophagous beetle species (such as S. cupreus) leave when no dung is available regardless of soil moisture and temperature.