Can Estivation Preferences Be Used to Develop Novel Management Tools against Invasive Mediterranean Snails?

Abstract

Terrestrial snails that live in hot and dry climates have developed strategies to cope with high summer temperatures. Several species estivate during the warmest months of the years by resting on vertical supports, typically in groups. Understanding how snails choose their estivation sites and aggregate may lead to the development of new management tools in areas where these snails are invasive. Here, we investigated the preferences of four snail species for vertical supports varying in widths and heights under laboratory and field conditions, and tested whether the presence of conspecifics or snails of other species affected these preferences. The results show that the snails strongly preferred wider supports in laboratory dual-choice tests, and one species (Theba pisana) showed a consistent preference for taller supports as well. These results were confirmed in the field, where more snails were found on wider and taller supports 24 h after being placed in test quadrats. The percentage of snails found in groups on a support was strongly density-dependent. The presence of conspecifics or their mucus did not affect the choices of the snails, nor did the presence of snails of other species or their mucus. Taken together, these results could lead to the development of attractive supports that could be used to mass-capture snails in the field.

Toward a push–pull strategy against invasive snails using chemical and visual stimuli

“…Our choice-test results suggest that snails do not simply orient toward the darkest visible point in their environment, otherwise black would have been consistently preferred to all the other colors tested. Black is already known to be attractive to snails 26 , 32 . However, the preference for the red color in terrestrial gastropods had not yet been documented, and red does not play an obvious role in the ecology of the four species studied (i.e.…”

“…For color strip choice, pole choice and barrier experiments, snails were placed individually in a circular arena with a black self-adhesive film on the floor (“Uni schwarz lack”, d-c-fix®, Weißbach, Germany) 26 and a white matte self-adhesive film venilia wall (“Uni weiss lack”, d-c-fix®, Weißbach, Germany). This arena had a height of 15 cm for all species and a diameter of 20 cm for conical shell species or 25 cm for globular shell species.…”

“…The test consisted of offering a choice between two colors: a black paper strip and a red, green, purple, orange, blue or yellow paper strip (primary and secondary colors). Black is already known to be attractive to these snails 26 , 32 and was used here as a standard to compare with other colors. To detect possible positional biases in this experiment, the position of the color strip (left or right to the black strip) was regularly switched, and a control test with two black strips was carried out.…”

“…The use of visual stimuli in push–pull systems has already been explored in several cases, for instance with the use of UV traps against xylophagous insects 23 or the use of visually attractive sticky traps to control the cherry fruit fly Rhagoletis cerasi 24 , 25 . A recent study by Hanache et al 26 explored the notion that visual stimuli could be exploited to construct artificial estivation supports to facilitate the mass capture of invasive snails. Their laboratory and field experiments showed that snails preferred the tallest and widest supports for estivation.…”

“…The aim of this study was to further develop an innovative control method against invasive snails in Australia based on a push–pull method. The first objective of the study was to improve the attractiveness of the artificial estivation supports developed by Hanache et al 26 , by testing snail preferences for supports of different colors in choice tests under laboratory and field conditions. The second objective was to test different barriers based on substances with repellent properties against snails documented in the literature (coffee, coffee ground, garlic), Snails are known to be more active when humidity is high 30 .…”