Who wants mice if there’s seafood? Crayfish as a novel food resource for a generalist avian predator.
Authors & affiliations
Jorge Sereno-Cadierno1 & Diego Fuentes-Lamas2
1Instituto de Investigación en Recursos Cinegéticos. Ronda de Toledo 12, 13005 Ciudad Real, Spain. E-mail: Jorge.Sereno@uclm.es
2Facultad de Biología, Universidad de Salamanca
Abstract
Generalist predators can exploit a wide range of food resources, making them more adaptable to many habitats and situations. Sometimes, the introduction or appearing of new species can lead to the exploitation of this resource, especially when it is abundant. In this sense, American crayfishes, being one of the most dangerous exotic species in the World are an important food resource to some species in their foreign distribution range.
Here, we describe a new behaviour and food source for common buzzards (Buteo buteo ) observed in Western Iberia. American crayfishes seem to be a recurrent food source for buzzards in late summer, showing a riverbank patrolling behaviour through riparian forests, overlapping the consumption of this crustacean with other carnivore species such as foxes (Vulpes vulpes ), american mink (Neogale vison ) and Eurasian otters (Lutra lutra ).
Introduction
American crayfishes (Procambarus clarkii Girard, 1852) are known to be one of the worst invasive species around the World (Vilá et al. 2010), supposing a menace to native biodiversity. This species has expanded considerably its original distribution range in Southern USA and Northern Mexico to other parts in America, Africa, Asia and Europe (Oficialdegi et al. 2020). In Spain, it was introduced in 1974 in the Guadalquivir marshes, to use it with commercial purposes (Catálogo Español de Especies Invasoras, 2013). From there, it has been introduced to almost every place in Iberia, becoming one of the main conservation threats to the Spanish crayfish (Austrapotamobius italicus ) (e.g. Gil-Sánchez et al. 2006) and other native fauna such as several species of amphibians (e.g. Cruz et al. 2006). However, since its introduction, it’s been demonstrated to have become an important part of the diet of several predators (Tablado et al. 2010), especially semi-acuatic carnivores such as Lutra lutra and several species of herons, storks and seagulls that can exploit this resource.
The role of crayfishes (Cambaridae) in raptor (referring here to Accipitriformes, Falconiformes and Strigiformes) diet has not been studied profoundly. In North America, are some records of owls likeStrix varia (Livezey, 2007) and Megascops asio (Courter, 2017) and some species of hawk, especially Buteo lineatus (e.g. Fisher, 2020; Johnston, 2000) preying upon crayfish (Cambaridae). Focusing on Europe and the Iberian Peninsula, it has been described that black kites (Milvus migrans ) have increased the consumption ofProcrambarus clarkii in the period 1976-2002 in Doñana National Park population, SW Iberia, in the place where American crayfishes were introduced first in Spain (Tablado et al. 2010).
In Europe, common buzzards (Buteo buteo L. 1758) are one of the most common raptor species and are recognized as generalist predators know to be capable of prey upon a great variety of species. They usually catch prey from gliding or soaring flight, although sometimes they hover, or walk on the ground when they are actively looking for invertebrates. Although common buzzard diet is wide, normally is mainly composed by mammals, (especially rabbits and rodents) and reptiles (mainly lizards) which usually constitute the main food income during the breeding period (e.g. Valverde, 1967; Mañosa & Cordero, 1992) while invertebrates (mainly Coleoptera and Orthoptera) play a more important role during the winter (Valverde, 1967; Bustamante, 1985). They can consume also carrion from roadkills (Elósegui, 1974), amphibians (Cramp & Simmons, 1980), nocturnal raptors (Tyto alba ) (Bullock, 2006) and even fish, since Madge, 1992 cited a predation event upon an eel. Although invertebrates can constitute an important part of the diet in certain populations and situations (Orta et al. 2022) the consumption of crustaceans has never been described for this species.
Methods
We used one Apeman H55 camera trap at a 40 cm height programmed to take 4 pictures every time the camera was activated. A period of 1 minute between activations was set. The camera is part of a 10 camera’s arrange along the Tormes river (Salamanca, Western Iberia) (Figure 1), designed to obtain carnivore pictures. We recorded buzzard events from 09/08/2021 until the 02/09/2021.
Results
Here, we describe a new foraging behaviour for common buzzards feeding on crayfishes in a riparian forest in Western Iberia. We observed a predation behaviour towards crayfishes several times by common buzzards. The animals were observed in 16 occasions in the riverbank that we were monitoring with a camera trap, showing a walking foraging behaviour in search of invertebrates (9) (Figure 2A), perching (2) or trying to catch prey (5). Despite this could be considered as isolated events, this behaviour was observed a lot of times during the study period, suggesting that these birds visit that place consciously (Table 1). The seem to actively look for this prey, walking next to the riverbank and catching them in the water when the level is low. After that, they usually move to a separate log to eat them. We recorded three events of successful predation and four attempts by at least two individuals (Figure 2B, Figure3). Since it is not easy to distinguish between individuals in this species, we assigned three codes to animals that we considered different basing on marks and colour.