Season and Dung Type Affect Sheep Dung-Colonising Insects

Abstract

Dung-colonising beetles and flies play an important for many ecosystem services including reducing pasture fouling and increasing nutrient cycling, yet the insects colonising sheep dung remain poorly studied. This thesis aimed to characterise the species colonising sheep dung and compare assemblages between sheep and cow dung.
A nine-month observational study, conducted in the Southwest of the UK, included incubating fresh dung (less than 24h old) to catch dung-colonising beetles and rear fly larvae/eggs, which were then identified to track insect presence in sheep dung. A 15-day colonisation experiment examined succession patterns by placing fresh artificial dung pats into a field, removing them at day 2, 5, 7, and 15, where they were placed into an incubator to collect and identify insects. Species-level identification and abundance data were analysed with generalized linear mixed models, principal component analysis, and PERMANOVA to quantify temporal and dung-type effects.
Overall, 16 species of dung-colonising beetles were found in sheep dung, with abundance being highest in October and May. Dung-colonising beetle abundance in sheep dung peaked in dung exposed for 5 days, while dung-colonising fly abundance peaked in dung exposed for 2 days, dominated by Sepsis spp. The GLMM indicated that sheep dung supported significantly more beetles than cow dung (z = 9.56, p < 0.001), with sheep pats having a 40% higher abundance on average. PCA and PERMANOVA confirmed distinct dung-colonising beetle communities between dung types (R² = 0.21, p = 0.002).
These findings demonstrate that there is a clear succession sequence which, along with dung type, structures insect communities, with key species like Agrilinus ater (Degeer, 1774) and Esymus pusillus (Herbst, 1789f) driving differences.
This work provides baseline data to inform pasture management to support invertebrate biodiversity and ecosystem functioning in livestock systems and highlights that treating sheep with insecticides in spring could strongly disrupt early-season dung-colonising beetle activity, potentially slowing nutrient turnover.

Date of Award	9 Dec 2025
Original language	English
Awarding Institution	University of Bristol
Supervisor	Richard Wall (Supervisor) & Chris F Clements (Supervisor)