Arxius de Miscel·lània Zoològica. Volum 23 (2025) Pàgines: 87-89
First record of predation by Anoplotrupes stercorosus (Coleoptera, Geotrupidae) on a slug species of the genus Arion (Stylommatophora, Arionidae)
Arias-Alvarez, G., Piquero-Rodriguez, I.
DOI: https://doi.org/10.32800/amz.2025.23.0087Descarregar
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Arias-Alvarez, G., Piquero-Rodriguez, I., 2025. First record of predation by Anoplotrupes stercorosus (Coleoptera, Geotrupidae) on a slug species of the genus Arion (Stylommatophora, Arionidae). Arxius de Miscel·lània Zoològica, 23: 87-89, DOI: https://doi.org/10.32800/amz.2025.23.0087-
Data de recepció:
- 04/01/2025
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Data d'acceptació:
- 15/05/2025
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Data de publicació:
- 20/05/2025
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Abstract
First record of predation by Anoplotrupes stercorosus (Coleoptera, Geotrupidae) on a slug species of the genus Arion (Stylommatophora, Arionidae)The beetle Anoplotrupes stercorosus inhabits European forests, preferably in cool hardwood and mixed environments. Larvae are strictly coprophagous while adults exhibit a varied diet that includes dung, decaying organic matter, and fungi. In mountainous areas, they are present in advanced stages of carcass decomposition, highlighting their ecological relevance as a decomposer. In Navarra (Spain), a unique behavior is reported. It has been observed that A. stercorosus attacked slugs of the genus Arion, which are larger than the beetles, and subsequently nested beneath them. This finding provides new insight into the ecological role of A. stercorosus and expands knowledge about its diet and trophic plasticity.
Key words: Dung beetle, Diet, Ecological plasticity, Palearctic, Iberian Peninsula
Resumen
Primer registro de depredación de una especie de babosa del género Arion (Stylommatophora, Arionidae) por parte de Anoplotrupes stercorosus (Coleoptera, Geotrupidae)El escarabajo Anoplotrupes stercorosus habita bosques europeos, preferentemente ambientes frescos de árboles de hoja caduca y mixtos. Las larvas son estrictamente coprófagas, mientras que los adultos siguen una dieta variada, que incluye estiércol, materia orgánica en descomposición y hongos. En áreas montañosas, están presentes en etapas avanzadas de descomposición de cadáveres, lo que destaca su relevancia ecológica. En Navarra (España), se documentó un comportamiento único: A. stercorosus atacó babosas del género Arion, más grandes que él, y realizó nidificación bajo las mismas. Este hallazgo proporciona una nueva perspectiva sobre la función ecológica de A. stercorosus y amplía el conocimiento sobre su dieta y plasticidad trófica.
Palabras clave: Escarabajo pelotero, Dieta, Plasticidad ecológica, Paleártico, Península Ibérica
Resum
Primer registre de depredació d'una espècie de llimac del gènere Arion (Stylommatophora, Arionidae) per part d'Anoplotrupes stercorosus (Coleoptera, Geotrupidae)L'escarabat Anoplotrupes stercorosus habita boscos europeus, preferentment ambients frescos de arbres de fulla caduca i mixtos. Les larves són estrictament copròfagues, mentre que els adults segueixen una dieta variada, que inclou fem, matèria orgànica en descomposició i fongs. En àrees muntanyenques, són presents en etapes avançades de descomposició de cadàvers, cosa que destaca la rellevància ecològica que tenen. A Navarra (Espanya), es va documentar un comportament únic: A. stercorosus va atacar llimacs del gènere Arion, més grans que ell, i va nidificar-hi a sota. Aquesta troballa proporciona una perspectiva nova sobre la funció ecològica d'A. stercorosus i amplia el coneixement sobre la seva dieta i plasticitat tròfica.
Paraules clau: Escarabat piloter, Dieta, Plasticitat ecològica, Paleàrtic, Península Ibèrica
The dung beetle Anoplotrupes stercorosus (Scriba 1791) belongs to the family Geotrupidae. It mainly inhabits forests in areas ranging from western Europe to western Siberia. This species can be found from lowlands to mountainous areas, typically preferring cool hardwood, mixed hardwood and conifer forests over wet and swampy forests (Byk and Semkiw 2010).
In this context, A. stercorosus feeds on decaying animal and vegetable matter, which is consumed by both adults and larvae (Marczak 2013, Jarmusz and Bajerlein 2015). However, during the adult stage the diet is varied and the beetles feed on dung (especially from sheep), animal carcasses, decomposing plant matter, and occasionally, decaying fungi (Jarmusz and Bajerlein 2015, Weithmann et al 2020). Its presence in different types of decaying organic matter reveals its ecological importance in the decomposition cycle (Weithmann et al 2020, von Hoermann et al 2021).
Few cases of predatory behavior and trophic specialization have been reported in coprophagous beetles (e.g. Scarabaeinae) (Silveira et al 2006, Larsen et al 2009, Martín et al 2021). Despite the numerous ecological studies on A. stercorosus (Marczak 2013, Jarmusz and Bajerlein 2015, Weithmann et al 2020), no such behavior has been documented to date for this species.
In a mixed beech forest in the Señorío de Bértiz Natural Park (Navarra, Spain) on 05-06/11/2024 (43.17385 ºN, 1.61462 ºW), individuals of A. stercorosus were observed feeding on the remains of slugs of the genus Arion (Férussac 1819) and actively preying on live individuals even though the slugs are considerably larger than the beetles. Moreover, a strong rotting odor was perceived emanating from the live slugs, suggesting that chemical signals may have attracted the beetles. To our knowledge, this is the first record of a Geotrupidae species preying on mollusks in the Palearctic. Martín et al (2021) described a similar predatory behavior in Canthon chalybaeus (Scarabaeinae), a neotropic species, which attacked the snail Bulimulus apodemetes using its clypeal teeth and anterior tibiae, before nesting under the killed slug. In the case of A. stercorosus, the beetles were observed using their mandibles directly on the slug's body. Typical burrowing behavior (the first stage) was recorded, with beetles nesting directly beneath the still-living slug (fig. 1, https://drive.google.com/file/d/1K5j5qwog-KwsceghlNzBsHi9iWUxnyL4/view)
Fig. 1. A, Arion slug with two Anoplotrupes stercorosus individuals, one of them is initiating nesting behaviour; B, beech forest where the interaction was observed.
Fig. 1. A, babosa del género Arion junto con dos individuos Anoplotrupes stercorosus, uno de ellos está iniciando el comportamiento de nidificación; B, hayedo donde se observó la interacción.
Species of the genus Arion are gastropods belonging to the family Arionidae. This genus has a Palearctic distribution, with the Iberian Peninsula hosting the highest diversity (Quinteiro et al 2005). These slugs are herbivorous, and in many cases they cause agricultural damage. They also carry pathogenic bacteria and parasites (Liegertová et al 2022). Certain species of carabid beetle prey upon Arion eggs and juveniles. In this second stage (juvenil) they secrete a defensive mucus (Hatteland et al 2010). Adults secrete even greater amounts of mucus as a defense mechanism. However, this did not deter A. stercorosus in our observations. It is possible that the larger size and greater mucus production of adult slugs might make them more detectable targets for predatory A. stercorosus individuals.
These observations highlight the potential that in situ studies without human interference can provide new information on the ecology of such a well-studied species. Expanding knowledge about diet and trophic plasticity contributes to understanding potential adaptations to ecosystems, raising new questions about alternative food sources, such as live slugs in this case. This behavior may increase the ecosystem services provided by A. stercorosus.
