Isotopic Niche of Syntopic Granivores in Commercial Orchards and Meadows

Abstract

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.

Diversity and Diet Differences of Small Mammals in Commensal Habitats

“…We, therefore, compared the central positions of the stable isotope ratios in the hair of syntopic small mammals in the commensal habitats with data on the same species from other disturbed habitats in Lithuania, namely commercial orchards and berry fields [48,49], flooded meadows [50] and flooded forest (Balčiauskas et al unpublished). In two species, A. flavicollis and C. glareolus, a comparison was also possible with the environment of a cormorant colony in Juodkrant ė, which was characterized by the ultimate level of disturbance in the form of biological pollution [39].…”

An Experimental Study in Wild Wood Mice Testing Elemental and Isotope Analysis in Faeces to Determine Variations in Food Intake Amount

“…in which authors found no gender differences in the concentration of various chemical elements in muscle and bone samples [ 80 ]. Likewise, no differences in isotopic values depending on age, sex or breeding condition have been found in several rodent species, including the wood mouse [ 51 , 70 , 74 , 75 , 81 , 82 , 83 , 84 ]. Overall, the non-variation in elemental and isotopic values due to individual traits could be attributed to the observed lack of individual differences in food intake inside traps.…”

Spatiotemporal Variation of Small Mammal Communities in Commercial Orchards across the Small Country

“…We show that commercial orchards are suitable habitats for various granivore and herbivore species and may support high abundances. As a source of provided foods, represented by the trophic niches of species, orchards are different from "wild" or "natural" habitats in as much as they are scarce in seeds for granivores [43], this thus influencing competition for food in herbivores [44]. Habitat characteristics have only so far been analyzed in general in terms of age and crop type ( [39] and this paper), though it is also possible that the structural diversity of vegetation may have an influence on diversity of small mammals in orchards and surrounding areas [53,68].…”