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Diel activity and use of multiple artificially constructed shelters in Astacus leptodactylus (Decapoda: Astacidae)

Abstract Astacus leptodactylus is a widespread European crayfish species with both native and invasive populations. However, in spite of its wide distribution, studies regarding its activity seem to be lacking. Thus, our goal was to study its preference towards shelters built from natural and artificial materials and follow its activities throughout the day in order to understand its diel activity patterns. We analyzed the video recordings of diel activities for 20 individuals to find out more about this species routine in a captive environment. Every specimen spent 22 hours in an arena with 4 different kinds of shelters provided (stone, wood, PVC pipe, vegetation). We investigated time spent in every shelter and different activity patterns throughout the analysis period. A preference for stone and wooden shelters was clearly expressed by all the individuals, independent of sex and size. Most of the activity was concentrated in close proximity to the provided shelters. Individuals exhibited both daytime and nighttime activity, with the latter being more intense, although, specimens spent almost 85% of the entire time inside shelters. Crayfish used all available shelters during our trials, proving a wide flexibility of the species towards shelter type, but the frequency of visits and time spent inside certain type of shelter varied significantly. Our study brings novel information regarding narrow-clawed crayfish shelter preference and activity in the proximity of the shelters, highlighting the importance of natural refuges in its daily routine.