What is an otter's favourite food? - a molecular investigation into the dietary preferences of the Eurasian otter (Lutra lutra) across the River Hull Catchment

Macarthur, James Alasdair

Abstract

Knowledge of top predator diets is fundamental to designing appropriate management strategies which ensure the protection of both predator and prey populations. The Eurasian otter (Lutra lutra) has traditionally been described as an opportunist; however, modern studies have demonstrated clear feeding preferences towards slow moving fish species. Prior dietary studies on the Eurasian otter have used morphological analysis of spraints to determine the prey eaten, and electrofishing to inform the fish communities present locally. Traditional morphological analyses are challenging, as it is difficult to identify bones down to the species level. Meanwhile, electrofishing may underestimate rare fish species present in the catchment. This study usesa non-invasive molecular methodology,whichprovidesgreater resolutionon the available fish community,to understand thedietary preferences of otters along the River Hull. Theresearchquestionswere: 1) Doesotter diet vary spatially in response to local fish communities?2) Doesotter diet vary seasonally in response to changes in fish activity?3) Is a single DNA extraction sufficient to investigate otter diets?4) Do otter and mink diets overlap in the River Hull catchment?DNA extracted from otter spraints (n= 81) was sequenced using broad scale vertebrate primers to inform the prey eaten; and compared with eDNA from water samples (n= 48) collected along the River Hull to inform the prey available. Otterdiet varied significantly across the upper, middle,and lower River Hull depending on the available fish community, and a consistent selective preference was observed towards the European bullhead (Cottus gobio). Overall otter diet did not vary significantly between seasons, however, Eurasian otters fed on significantly more different prey items in spring (Mean= 3.125) than winter (Mean= 2.482). The replicate DNA extraction experiment demonstrated that a single extraction replicate is sufficient for detecting most prey items. Finally, comparisons between the Eurasian otter and American mink have provided further evidence of niche differentiation between the two species, thus allowing for coexistence with minimal overlap.

Citation

Macarthur, J. A. What is an otter's favourite food? - a molecular investigation into the dietary preferences of the Eurasian otter (Lutra lutra) across the River Hull Catchment. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4297795

• Thesis Type: Thesis
• Deposit Date: May 25, 2023
• Publicly Available Date: May 25, 2023
• Keywords: Biological sciences
• Public URL: https://hull-repository.worktribe.com/output/4297795
• Additional Information: School of Biological, Biomedical and Environmental Sciences, The University of Hull
• Award Date: Aug 1, 2022