Volume 17 Issue 2 Pages 59 - 99 (October 2000)

Citation: Bailley, M.P. (2000) Otter Lutra lutra Predating Adult Dragonflies IUCN Otter Spec. Group Bull. 17(2): 84 - 85

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Otter Lutra lutra Predating Adult Dragonflies

Michael P. Bailley

Countryside Council for Wales, Plas Gogerddan, Aberystwyth, Ceredigion SY23 3EE, United Kingdom, e-mail: m.bailey@ccw.gov.uk

One day in June 2000, whilst walking beside a shallow drainage channel on the coastal raised bog of Cors Fochno (Borth bog) in west Wales, I noticed a collection of dragonfly wings clustered on wet sphagnum moss at the ditch margin. On close inspection the wings, 16 in all, were identified from their distinctive markings as belonging to adult Four-spotted Chaser, Libellula quadrimaculata, a common breeder at the location.

The cluster of wings also lay on a route regularly used by Otter Lutra lutra, and clearly marked by a trail through the floating carpet of sphagnum moss which covers much of this ditch. Following the otter run beyond the ditch into an area of tall vegetation, dominated by Purple moor-grass Molinia caerulea, I found a second, smaller cluster of wings and close by, an otter spraint. The latter confirmed my suspicion that one or more otter were responsible for the predation since it contained fragments of glossy brown and black carapace matching the thoracic markings of L. quadrimaculata. It would seem likely that the otter had been reaping a seasonal harvest of dragonflies plucked from roosting sites beside a regular foraging route.

A few weeks later I observed a further collection of L. quadrimaculata wings in a similar situation but 2.5km away at the western-most edge of the Cors Fochno peatland. Whilst it is possible that the same individual otter could be responsible, this occurrence suggests that the observed feeding habit may be more widespread amongst the local otter population.

The diet of Eurasian Otter has been investigated in some detail but this appears to be the first recorded instance of adult odonata being predated.

Resumen: Predación sobre libélulas adultas por parte de nutrias Lutra lutra

En junio 2000 se observó una colección de alas de libélulas (Libellula quadrimaculata) junto a un canal de drenaje en Cors Fochno en el oeste de Gales. Esta colección se encontraba junto a una ruta regularmente utilizada por nutrias Lutra lutra. Siguiendo dicho el trillo se encontró un segundo grupo de alas junto a una feca de nutria, lo que confirmó la sospecha de que una o más nutrias eran las responsables de la predación ya que la feca contenía fragmentos torácicos de L. quadrimaculata. Aparentemente la nutria había estado colectando libélulas aprovechando la presencia estacional de estas junto a una ruta regular de forrajeo. Pocas semanas después una colección similar de alas fue observada a 2.5 km del sitio anterior. Si bien es posible que el mismo animal haya sido el responsable, la observación sugiere que este hábito alimenticio puede estar más ampliamente extendido entre la población local de nutrias. La dieta de la nutria europea ha sido investigada con bastante detalle pero esta parece ser la primera vez que se registra predación sobre odonatas adultos.
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