Mixing the Message: Do Dung Beetles (Coleoptera: Scarabaeidae) Affect Dung-Generated Greenhouse Gas Emissions?

By mixing and potentially aerating dung, dung beetles may affect the microbes producing the greenhouse gases (GHGs): carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Here, their sum-total global warming effect is described as the carbon dioxide equivalent (CO2e). Our literature analysis of reported GHG emissions and statistics suggests that most dung beetles do not, however, reduce CO2e even if they do affect individual GHGs. Here, we compare the GHG signature of homogenized ("premixed") and unhomogenized ("unmixed") dung with and without dung beetles to test whether mixing and burial influence GHGs. Mixing by hand or by dung beetles did not reduce any GHG - in fact, tunneling dung beetles increased N2O medians by [≥]1.8x compared with dung-only. This suggests that either: 1) dung beetles do not meaningfully mitigate GHGs as a whole; 2) dung beetle burial activity affects GHGs more than mixing alone; or 3) greater dung beetle abundance and activity is required to produce an effect.