Seasonal and interspecific evaluation of predation by mammals and birds on the introduced red swamp crayfish Procambarus clarkii (Crustacea, Cambaridae) in a freshwater marsh (Portugal)

Abstract

The crayfish Procambarus clarkii is an introduced species in Portugal, becoming a new available resource that has possibly changed local trophic relationships. The purpose of the present study was to understand better how a naïve assembly of predators reacted to a recent invader. Predation on P. clarkii by nine species of mammals (Order: Carnivora) and six species of birds (Order: Ciconiiformes) in a marsh area in Portugal, was surveyed through the collection of faeces and pellets over a 24-month period. Seasonal variation in the consumption of this prey by different predators was evaluated, and estimation made of size and weight of P. clarkii consumed by them. Procambarus clarkii was readily preyed upon by four species of mammalian carnivores and five species of ciconiiform birds. The consumption of P. clarkii varied seasonally in both years with a trend between seasonal exploitation and its population structure and availability. Generally, the use of P. clarkii by all predators was more intense in spring, summer and autumn than in winter, and was directed towards larger and heavier individuals. These findings result from the population dynamics presented by P. clarkii in the marsh area studied here, since larger and heavier individuals were more available in spring, summer and autumn. Procambarus clarkii is an important food resource for mammals and birds and it seems to play a key role in the trophic interactions of the riparian and terrestrial communities of the marsh.