Comparison of trophic spectra and hunting strategies of some large arachnids (Arachnida: Scorpiones, Solifugae, Aranei) in semi-desert biocenoses of Gobustan (Eastern Azerbaijan)

Prey composition has been studied for the three syntopic species of arachnids. These were the mottled scorpion Mesobuthus eupeus (C.L. Koch, 1839), the common solifuge (camel-spider) Galeodes araneoides (Pallas, 1772), and the tarantula (wolf-spider) Lycosa praegrandis (C.L. Koch, 1836). The investigations were carried out in arid biocenoses of the interfluve of Pirsagat Jeyrankechmez (Gobustan, Eastern Azerbaijan). These species were chosen for study because of their high importance in communities, a wide range of methods of obtaining food, relatively high abundancy, co-habitation in this area, mainly the night activity and their quality as generalized predators. All this made them convenient model objects for studying the mechanisms of ecological segregation. Despite the fact that a significant number of publications have been devoted to these species in which various aspects of their biology and ecology have been examined, there is no holistic view of the structure of ecological niches of these arachnids in the literature. So far, some specific aspects of their biology which determine peculiar role of each species in nature have not been sufficiently studied. Ecological difference among these species discovered by previous studies does not allow us to fully determine the conditions for their cohabitation and to establish the presence or absence of any significant competition. Collection of data and visual observations were carried out from May to September in 2012, 2013 and 2016.The main part of the material was collected in the summer months in biotopes of three types: semi-desert loamy plain, stony slopes of the plateau, hilly valley with ridged clusters of residual rock. The composition and quantity of prey was estimated from the remains found in permanent shelters of the respective predators, as well as during direct observations of predators with a prey in chelicera. The remains of consumed organisms from the depth of predator’s burrows were extracted manually or by an aspirator (exhauster). Arachnids were weighed on electronic scales with precision to within 0.01 g before and after night activity. For this purpose, they were extracted from the shelters, placed in the plastic containers, weighed and then returned back. The next day they were caught again and re-weighed. In total, about 380 weightings of 126 individuals of arachnids were produced. Data on the mass of 90 specimens of arachnids (35 scorpions, 25 solifuges and 30 tarantulas) were the m