Olfactometers can test dung beetle olfactory response and diel activity: a case study in South Korea.

Laboratory experiments are widely used to understand insect ecology and behavior. One of the taxa frequently studied this way is the dung beetle to test olfactory responses to resources using olfactometers. Diel activity is another frequently investigated characteristic of dung beetles, but this was usually done with field experiments. The disadvantages of this are that it is labor- and resource-intensive and that weather conditions can influence the results. To address this, we propose that diel activity can also be measured with olfactometers in addition to olfactory response. A four-trap olfactometer was designed to test for inter-trophic preference between carnivore, herbivore, omnivore dung, and control (no dung). Intra-trophic preference was also examined to check differences between mammals of a single feeding guild. The diel activity was examined by checking the traps every three hours from 07:30 to 19:30. Six experiments with different combinations of dung were conducted on six dung beetle species. The six species were chosen based on their resource preference assessed from field experiments, which were expected to be mimicked in the laboratory experiment. The results for the olfactory preference were unclear and did not resemble the results of the field experiment, possibly due to limitations in olfactometer design. However, more accurate results were produced for diel activity, suggesting that using olfactometers to measure diel activity is possible. Conducting two experiments simultaneously would save time and resources and ultimately contribute to enhancing our understanding of dung beetle morphology, evolutionary history, and life cycle.