Diet composition analysis provides new management insights for a highly specialized endangered small mammal

Abstract

The critically endangered Amargosa vole (Microtus californicus scirpensis) is found only in rare marsh habitat near Tecopa, California in a plant community dominated by three-square bulrush (Schoenoplectus americanus). Since the earliest research on the Amargosa vole, the existing paradigm has been that these voles are obligatorily dependent on bulrush as their only food source and for the three-dimensional canopy and litter structure it provides for predator avoidance. However, no prior research has confirmed the diet of the Amargosa vole. In this study we characterized the Amargosa vole' nutritional needs, analyzed the quality of bulrush by forage analysis, and performed microhistological and metabarcoding analyses of vole feces to determine what foods were consumed in the wild. All bulrush plant tissues analyzed were low in fat (from 0.9% of dry matter in roots to 3.6% in seeds), high in neutral detergent fiber (from 5.9% in rhizomes to 33.6% in seeds), and low in protein (7.3-8.4%). These findings support the conclusion that bulrush alone is unlikely to support vole survival and reproduction. Fecal microhistology and DNA metabarcoding revealed relatively diverse diets including plants in 14 families, with rushes (Juncaceae), bulrushes (Cyperaceae), and grasses (Poaceae) being the most common diet items. On microhistology, all analyzed samples contained bulrush, sedges (Carex sp.), rushes (Juncus sp.), and beaked spikerush (Eleocharis rostrellata) even from marshes where non-bulrush plants were uncommon. There was evidence of insects at <1% in two marshes but none in the remaining marshes. Metabarcoding detected ten genera of plants. When considering non-Schoenoplectus targets, for which metabarcoding had poor sensitivity, saltgrass (Distichlis spicata) was the most commonly detected species, with prominent contributions from seaside arrowgrass (Triglochin concinna) and yerba mansa (Anemopsis californica) as well. Diversity of vole diets generally increased with increasing site plant diversity, but differences were not statistically significant. Confirming details about dietary behaviors is critical for informing

Molecular dietary analyses of western capercaillies (Tetrao urogallus) reveal a diverse diet

“…Alternatively, metabarcoding may be a more sensitive and powerful method to detect a larger variety of diet items within one faecal sample. This is supported by studies that have directly compared non-molecular methods and metabarcoding for reconstructing diet from the same individuals (Castle et al, 2020; Nichols et al, 2016).…”

High total water loss driven by low-fat diet in desert-adapted mice

“…Different macronutrients yield different volumes of metabolic water via catabolism (carbohydrates = 0.6g metabolic water per gram, protein = 0.4g per gram, and fats = 1.07g per gram, Davidson et al, 1986). Many plants native to the Sonoran Desert have a fat content comparable to that of the LFD used in this study (5.49 - 9.88% for leaf tissues and branches, McArthur, 1994; 0.90-3.60% for roots and seeds, Castle et al, 2020). Moisture content can influence diet selection in wild desert mammals, which depend on preformed water in their diet (Frank, 1988; Orr et al, 2015).…”

Molecular dietary analyses of western capercaillies (Tetrao urogallus) reveal a diverse diet

“…Alternatively, metabarcoding is a more sensitive and powerful method to detect a larger variety of diet items within one fecal sample. This is supported by studies that have directly compared non‐molecular methods and metabarcoding for reconstructing diet from the same individuals (Castle et al, 2020; Nichols et al, 2016). Another consideration could be that ingested plant DNA from prior meals are retained due to differential retention time, leading to the rarity of monodiets being observed using metabarcoding.…”