The digging‐in effect on ant studies with pitfall traps: influence of type of habitat and sampling time

Abstract

Pitfall traps are among the most common sampling methods used for the study of ants. There are many types of traps and many possible ways of using them. The various methodologies may introduce biases in sampling. One possible bias may be caused by the digging‐in effect (DE), resulting in higher catches of ants immediately after traps are set in the ground which subsequently decline. In this study, we performed two experiments to verify the consequences of the DE for ants in a Mediterranean ecosystem. In the first experiment we distinguished between two types of habitats: closed and open (i.e., with or without shrub or tree cover). The second experiment was carried out in a homogeneous pasture where the time of prevalence of the DE was verified, investigating the duration of the effect. The results indicate differences between communities in the first 24 h after setting of the traps, which had disappeared after 48 h. This does not dismiss the possibility of certain species being affected either positively (increase in captures) or negatively (decrease). Changes in species composition, determining whether the DE was manifested or not, differed among habitat types.

Measuring the effect of long-term pitfall trapping on the prevalence of epigeal arthropods: A case study in the Pacific Coast of Colombia

“…Besides, there were important differences in total ant -and Ectatomma ruidum -captures across the four different plots, representing different levels of disturbance. Following the findings of Jiménez-Carmona et al (2019), this is of importance. Habitat specifics might influence differences in detected digging-in effects.…”

“…There is a systematic increase in the early captures of Collembola (Joosse & Kapteijn, 1968) and some ant species (Greenslade, 1973) since their locomotory activity also increases because of higher concentrations of CO 2 . More recent studies have tested how the robustness of pitfall trapping is affected by habitat specificities (Jiménez-Carmona et al, 2019), the timing of pitfall opening after installation (Lasmar et al, 2017), and length of the sampling interval (Schimel et al, 2010). Still, the hypothesis of a decrease in observed captures resulting from the reduction of ant populations caused by the pitfall traps, as proposed by Jansen and Metz (1977), has never been formally tested.…”

The population dynamics of the yellow crazy ant Anoplolepis gracilipes (Hymenoptera: Formicidae) on a tropical island in Malaysia

“…Each trap consisted of a 50 ml falcon tube filled with 75% ethyl alcohol. In the effort to reduce digging‐in effects (digging‐in effects occur when a disproportionately high number of ants are caught within pitfall traps immediately after the traps are placed; this is due to the penetration of their nest galleries; Jiménez‐Carmona et al, 2019), pitfall traps were set up and covered for 24 h before data collection commenced. The pitfall traps were placed in sandy soil surrounded by grass and small trees at SP, and in compacted, gravelly soil at a slight inclination with sparse tree cover at DC.…”

Environmental DNA detection of an invasive ant species (Linepithema humile) from soil samples

“…Therefore, there is an urgent need to identify their invasion and distribution at the early stages. Traditionally, direct observations and/or bait trap surveys have been performed to monitor ant populations 20 , 21 . However, such methods have disadvantages such as the requirement for significant labor input, time, and expenditure.…”