Abstract
Simple SummaryGranivorous murids, namely striped field (Apodemus agrarius), yellow-necked (Apodemus flavicollis), and harvest (Micromys minutus) mice, occur in a variety of habitats and live syntopically in agricultural areas. Agroecosystems may be quite complex isotopically with δ15N values being influenced by many internal and external fluxes. Using isotopic (δ15N and δ13C) compositions from hair samples, we analysed isotopic niches of granivores in apple and plum orchards, raspberry and currant plantations, and nearby meadows in Lithuania. As the main hypothesis, we expected differences in the isotopic niches of these species (being a proxy for their diet), minimising interspecific competition. Striped field and yellow-necked mice were trapped in every habitat. Therefore, syntopic co-occurrence of granivores depended on the presence of harvest mice in the apple orchards, raspberry plantations, and meadows that served as control habitats. All species were fully separated according to δ15N values, presuming different amounts of food of animal origin in their diet. The separation of species according to δ13C was not expressed in all habitats. The core dietary niches of these species were fully separated in the apple orchards and raspberry plantations. Intraspecific differences of the isotopic niche were not present in any of the three species: that is, resources were equally used by males and females, adults, subadults, and juveniles.In agricultural habitats, diets and trophic positions of syntopic granivorous small mammals are not known sufficiently. Agroecosystems may be quite complex isotopically and the most complex situation concerns the nitrogen-15 isotope as δ15N values are influenced by many internal and external fluxes. We analysed the isotopic niches of striped field (Apodemus agrarius), yellow-necked (Apodemus flavicollis), and harvest (Micromys minutus) mice living sympatrically and syntopically in apple and plum orchards, raspberry and currant plantations, and nearby meadows that were used as control habitats. Carbon (δ13C) and nitrogen (δ15N) stable isotope ratios from hair samples were used as a proxy for their diet. As the main hypothesis, we expected differences in the isotopic niches of these three species, minimising interspecific competition. All species were fully separated according to δ15N values, presuming different amounts of food of animal origin in their diet. The separation of species according to δ13C was not expressed in all habitats. The core dietary niches of these species were fully separated in the apple orchards and raspberry plantations. Intraspecific differences of the isotopic niche were not present in any of the three species: that is, resources were equally used by males and females, adults, subadults, and juveniles.
Highlights
We analysed the isotopic niches of striped field (Apodemus agrarius), yellow-necked (Apodemus flavicollis), and harvest (Micromys minutus) mice living sympatrically and syntopically in apple and plum orchards, raspberry and currant plantations, and nearby meadows that were used as control habitats
Three granivorous rodents, namely the striped field mouse Apodemus agrarius (Pallas, 1771), the yellow-necked mouse Apodemus flavicollis (Melchior, 1834), and the harvest mouse Micromys minutus (Pallas, 1771), all occur in a wide variety of habitats but favour areas of tall, dense vegetation [1,2,3,4]
M. minutus was trapped in seven sites (39%, CI = 20–61%), the distribution of this species was significantly narrower than that of A. agrarius (χ2 = 9.48, p = 0.002) and A. flavicollis (χ2 = 12.15, p < 0.001)
Summary
Namely the striped field mouse Apodemus agrarius (Pallas, 1771), the yellow-necked mouse Apodemus flavicollis (Melchior, 1834), and the harvest mouse Micromys minutus (Pallas, 1771), all occur in a wide variety of habitats but favour areas of tall, dense vegetation [1,2,3,4]. With high dietary and microhabitat overlaps, some small mammal species could coexist primarily only due to passive, mutually avoiding and amicable interactions [24] Another opportunity for coexistence is niche partitioning [25], which may be based on time [26,27], space or habitats [28,29], or resources [30,31]. Our study concentrated on a stable isotope-based evaluation of the trophic niches of three granivores species, namely striped field mouse, yellow-necked mouse, and harvest mouse, these being sympatric and syntopic simultaneously in commercial orchards, berry plantations, and nearby meadows, which are defined as control habitats. In a few cases, trapped animals were killed by cervical dislocation
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