Consumer roles of small mammals within fragmented native tallgrass prairie

Abstract

Grassland ecosystems globally are being negatively impacted by changes in climate, disturbance regimes, nutrient flux, and consumer guilds. Changes in the trophic ecology of consumers can substantially influence local resources, contributing to shifting diversity, community turnover, and other processes of ecosystem change. Small mammals are diverse and abundant within grasslands and yet the impact of changing ecosystems on small mammals and the role of these mammals as consumers are still both under-studied. We assessed small mammal resource use within grassland and woodland vegetation types that have resulted from landscape-scale experimental disturbance through fire treatments within the tallgrass prairie ecoregion of the North American Great Plains. We predicted that resource use would vary significantly among grassland vs. woodland communities, in turn reducing the role of small mammals in contributing to future maintenance of native prairies. We sampled five dominant species of rodents across three years and multiple habitats. Using stable isotope analysis, we investigated isotopic niche area and overlap to infer variation in diet, both within and among species. Resource use shifted in bivariate isotopic space seasonally but not across years when combining all species and habitats. Inferred spring diet (based on fur samples) was highly diverse and overlapping. Summer isotopic values (based on liver tissue) in woody habitat treatments were narrower and overlapped less than within grassland habitats. Consumers generally shifted from C 4 herbivory to C 3 herbivory, or greater omnivory, when analyzing grassland, shrubland, and woodland habitats respectively. Within the tallgrass prairie ecosystem, small mammal populations in herbaceous-dominated habitats use a broader variety of resources than small mammals in proximate woody-dominated habitats. As native grasslands experience woody encroachment, small mammal assemblages experience turnover of dominant species and associated changes in diet. Ecosystem changes such as cessation of frequent fire resulting in more woody habitats may include reduced roles by native small mammals as consumers/dispersers/propagators of native grassland plants.

Stable Isotopes Reveal the Dominant Species to Have the Widest Trophic Niche of Three Syntopic Microtus Voles

“…Our results are of interest for small mammal trophic ecology in general [ 5 , 18 , 59 , 65 , 66 ]. Due to agricultural activities, orchards and berry plantations are most possibly not places of abundant and diverse resources for herbivores.…”

“…Grass is mowed (and removed from the orchards), while herbicides and other plant protection measures are applied [ 11 , 67 , 68 , 69 ], despite the knowledge that cover crops in the orchards may enable ecosystem services [ 70 ]. The limited availability of resources should lead to narrow trophic niches and reduced niche overlap in small mammals [ 43 , 66 , 71 ].…”

Isotopic Niche of Syntopic Granivores in Commercial Orchards and Meadows

“…Depending on the habitat and latitude, seasonal changes in the isotopic niche may be expressed [ 44 , 50 , 52 ], not expressed [ 23 ], or absent (this paper).…”

Increased availability of preferred food and decreased foraging costs from degraded grasslands lead to rodent pests in the Qinghai-Tibet Plateau

“…Although the diet of plateau zokors contains numerous plant species, Potentilla accounted for a large proportion of their dietary choices. Owing to the high energetic cost of burrowing, non-directional underground search patterns, and low food availability, plateau zokors need to consider the benefits and costs of foraging (Xie et al, 2014), but diets of different qualities are distributed in a mosaic model (Hope et al, 2021). The dominant species of RG and LD grassland were mainly grasses and sedges, whereas the forbs favored by plateau zokors were relatively small and embedded within.…”

“…However, food types of different qualities are spatially distributed in a mosaic pattern. Highquality food resources often exist on a small scale and are often surrounded by large-scale, low-quality food resources (Hope et al, 2021). The primary vegetation of alpine meadows on the QTP is dominated by grasses and sedges; however, as grassland degradation advances, the proportion of forbs significantly increases (Zhang et al, 2018).…”