Resource partitioning in coprophagous beetles from sheep dung: Phenology and microhabitat preferences

Peter Sowig & Thomas Wassmer

Institute of Biology I (Zoology), Albert-Ludwigs-University, Freiburg i. Brg., Germany

On a pasture in SW-Germany coprophagous beetles (Scarabaeidae, Hydrophilidae: Sphaeridiinae and Staphylinidae: Oxytelinae) from sheep droppings were studied considering the following niche dimensions: season, size, type and water content of the dropping. 1. Phenological differences were found especially within endocoprid Scarabaeidae. Dominant Aphodius-species were clearly separated from each other by their phenology, while nearly all Hydrophilidae from the genus Cercyon and paracoprid Scarabaeidae were most abundant in May. 2. Sheep produce different types of droppings, either compact lumps or small pellets. The latter are mostly deposited in groups. Since these pellets dry out quickly, but rehydrate during rainfall, a high variability of humidity conditions makes pellets unattractive to many dung beetles. 3. Pairwise niche overlap indices in coprophagous beetles from sheep droppings were calculated regarding two niche dimensions: dropping size and water content. Cluster trees showed a clear distinction between species according to these microhabitat factors. Especially Hydrophilidae tend to avoid small droppings which might be due to unstable humidity conditions there. Mean intrageneric overlap within genera with more than one species was equal to or even higher than mean intergeneric overlap rates.

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