Seasonal use of ponds as foraging habitat by Eurasian otter with description of an alternative handling technique for common toad predation
2013
Almeida, David | Rodolfo, Nahuel | Sayer, Carl D. | Copp, Gordon H.
Research in freshwater ecology has traditionally focused on water courses or large still waters. However, ponds support proportionately high levels of biodiversity relative to other inland waters in Europe, and foraging by Eurasian otter Lutra lutra (L., 1758) could have considerable impacts on species composition in these small water bodies. The aim of the present study was to analyse otter spraints around ponds during two contrasting seasons (winter and spring) in north Norfolk (eastern England), where both otter and ponds are of particular conservation concern. Spraint density, prey diversity and the consumption of river-associated species were higher in spring than winter. In both seasons, birds were the most important prey category as ingested biomass. European eel Anguilla anguilla (L., 1758) and amphibians, specifically common frog Rana temporaria L., 1758 and common toad Bufo bufo (L., 1758), were more consumed in spring, whereas northern pike Esox lucius L., 1758 and tench Tinca tinca (L., 1758) were taken in winter. Non-native common carp Cyprinus carpio L., 1758 was important in both seasons, whereas threatened native crucian carp Carassius carassius (L., 1758) was a minor prey item. Massive kills of common toad, which involved a new handling technique for predation on this species, were observed mainly in spring. The study demonstrated otters to display great plasticity in foraging behaviour and contributes to the understanding of otter predatory pressure on pond biodiversity, with implications for landscape management.
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